welding

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Duties and ResponsibilitiesDuties and ResponsibilitiesSection 1Section 1

Welding InspectorWelding Inspector

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•• Code complianceCode compliance

•• Workmanship controlWorkmanship control

•• Documentation controlDocumentation control

Main Responsibilities Main Responsibilities 1.11.1

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Personal Attributes Personal Attributes 1.11.1

Important qualities that good Inspectors are expected Important qualities that good Inspectors are expected to have are: to have are:

••HonestyHonesty

••IntegrityIntegrity

••KnowledgeKnowledge

••Good communicatorGood communicator

••Physical fitnessPhysical fitness

••Good eyesightGood eyesight

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Standard for Visual Inspection Standard for Visual Inspection 1.11.1

Basic RequirementsBasic RequirementsBS EN 970 BS EN 970 -- NonNon--destructive examination of fusion destructive examination of fusion

welds welds -- Visual examinationVisual examinationWelding Inspection Personnel should:Welding Inspection Personnel should:

•• be familiar with relevant standards, rules and specifications be familiar with relevant standards, rules and specifications applicable to the fabrication work to be undertakenapplicable to the fabrication work to be undertaken

•• be informed about the welding procedures to be usedbe informed about the welding procedures to be used

•• have good vision have good vision (which should be checked every 12 (which should be checked every 12 months)months)

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Welding Inspection Welding Inspection 1.21.2

Conditions for Visual Inspection (to BS EN 970)Conditions for Visual Inspection (to BS EN 970)Illumination:Illumination:•• 350 lux minimum required350 lux minimum required•• (recommends 500 lux (recommends 500 lux -- normal shop or office lighting)normal shop or office lighting)

Vision Access:Vision Access:•• eye should be within 600mm of the surfaceeye should be within 600mm of the surface•• viewing angle (line from eye to surface) to be not less than viewing angle (line from eye to surface) to be not less than

3030°°

3030°°

600mm600mm

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Aids to Visual Inspection (to BS EN 970)Aids to Visual Inspection (to BS EN 970)

When access is restricted may use: When access is restricted may use: a mirrored boroscopea mirrored boroscopea fibre optic viewing systema fibre optic viewing system

Other aids:Other aids:welding gauges welding gauges (for checking bevel angles, weld (for checking bevel angles, weld profile, fillet sizing, undercut depth)profile, fillet sizing, undercut depth)dedicated welddedicated weld--gap gauges and linear misalignment gap gauges and linear misalignment (high(high--low) gaugeslow) gaugesstraight edges and measuring tapesstraight edges and measuring tapesmagnifying lens magnifying lens (if magnification lens used it (if magnification lens used it should have magnification between X2 to X5)should have magnification between X2 to X5)

usually by usually by agreementagreement

}}

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Welding Inspectors Equipment Welding Inspectors Equipment 1.31.3

Measuring devices:Measuring devices:•• flexible tape, steel ruleflexible tape, steel rule

•• Temperature indicating crayonsTemperature indicating crayons

•• Welding gaugesWelding gauges

•• VoltmeterVoltmeter

•• AmmeterAmmeter

•• Magnifying glassMagnifying glass

•• Torch / flash lightTorch / flash light

•• Gas flowGas flow--metermeter

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TWI MultiTWI Multi--purpose Welding Gaugepurpose Welding Gauge Misalignment GaugesMisalignment GaugesHiHi--Lo GaugeLo Gauge

Fillet Weld GaugesFillet Weld Gauges

G.A.L.

S.T.D.

10mm

12m

m

16mm

3mm

6mm

9mm

5mm4m

m

LG.A.L.

S.T.D.

10mm

12mm

16mm

3mm

6mm

9mm5mm

4mm

T

Welding Inspectors Gauges Welding Inspectors Gauges 1.31.3

605040

0 1/4 1/2 3/4 10

510

1520

IN

MM

MM15

1/2MMIN

HI-L

O S

ingl

e Pu

rpos

e W

eldi

ng G

auge

1

2

3

4

5

6

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Tong TesterTong Tester

AmmeterAmmeterVoltmeterVoltmeter

Welding Inspectors Equipment Welding Inspectors Equipment 1.31.3

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Stages of Visual Inspection (to BS EN 970)Stages of Visual Inspection (to BS EN 970)Extent of examination and when required should be defined in Extent of examination and when required should be defined in the application standard or by agreement between the the application standard or by agreement between the contracting partiescontracting parties

For high integrity fabrications inspection required throughout For high integrity fabrications inspection required throughout the fabrication process: the fabrication process:

Before weldingBefore welding(Before assemble & After assembly)(Before assemble & After assembly)

During weldingDuring weldingAfter weldingAfter welding

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Typical Duties of a Welding Inspector Typical Duties of a Welding Inspector 1.51.5

Before WeldingBefore Welding

Preparation: Preparation:

Familiarisation with relevant Familiarisation with relevant ‘‘documentsdocuments’…’…

•• Application Standard/Code Application Standard/Code -- for visual acceptance for visual acceptance requirementsrequirements

•• Drawings Drawings -- item details and positions/tolerances etcitem details and positions/tolerances etc

•• Quality Control Procedures Quality Control Procedures -- for activities such as material for activities such as material handling, documentation control, storage & issue of handling, documentation control, storage & issue of welding consumableswelding consumables

•• Quality Plan/Inspection & Test Plan/Inspection Checklist Quality Plan/Inspection & Test Plan/Inspection Checklist --details of inspection requirements, inspection procedures details of inspection requirements, inspection procedures & records required& records required

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Welding Procedures:Welding Procedures:

•• are applicable to joints to be welded & approvedare applicable to joints to be welded & approved

•• are available to welders & inspectorsare available to welders & inspectors

Welder Qualifications:Welder Qualifications:

•• list of available qualified welders related to WPSlist of available qualified welders related to WPS’’ss

•• certificates are valid and certificates are valid and ‘‘inin--datedate’’

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Equipment:Equipment:

all inspection equipment is in good condition & all inspection equipment is in good condition & calibrated as necessarycalibrated as necessary

all safety requirements are understood & necessary all safety requirements are understood & necessary equipment availableequipment available

Materials:Materials:

can be identified & related to test certificates, can be identified & related to test certificates, traceability !traceability !

are of correct dimensionsare of correct dimensions

are in suitable condition (no damage/contamination)are in suitable condition (no damage/contamination)

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Consumables:Consumables:

in accordance with WPSin accordance with WPS’’ss

are being controlled in accordance with Procedureare being controlled in accordance with Procedure

Weld Preparations:Weld Preparations:

comply with WPS/drawingcomply with WPS/drawing

free from defects & contaminationfree from defects & contamination

Welding Equipment:Welding Equipment:

in good order & calibrated as required by Procedurein good order & calibrated as required by Procedure

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Before WeldingBefore WeldingFitFit--upup

complies with WPScomplies with WPS

Number / size of tack welds to Code / good Number / size of tack welds to Code / good workmanship workmanship

PrePre--heatheat

if specified if specified

minimum temperature complies with WPSminimum temperature complies with WPS

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During WeldingDuring Welding

Weather conditionsWeather conditions

•• suitable if site / field weldingsuitable if site / field welding

Welding Process(es)Welding Process(es)

•• in accordance with WPSin accordance with WPS

WelderWelder

•• is approved to weld the jointis approved to weld the joint

PrePre--heat (if required)heat (if required)

•• minimum temperature as specified by WPSminimum temperature as specified by WPS

•• maximum interpass temperature as WPSmaximum interpass temperature as WPS

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During WeldingDuring WeldingWelding consumablesWelding consumables

in accordance with WPSin accordance with WPS

in suitable conditionin suitable condition

controlled issue and handlingcontrolled issue and handling

Welding ParametersWelding Parameters

current, voltage & travel speed current, voltage & travel speed –– as WPSas WPS

Root runsRoot runs

if possible, visually inspect root before singleif possible, visually inspect root before single--sided sided welds are filled upwelds are filled up

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During WeldingDuring Welding

InterInter--run cleaningrun cleaning

in accordance with an approved method (& back in accordance with an approved method (& back gouging) to good workmanship standardgouging) to good workmanship standard

Distortion controlDistortion control

welding is balanced & overwelding is balanced & over--welding is avoidedwelding is avoided

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After WeldingAfter WeldingWeld IdentificationWeld Identification

•• identified/numbered as requiredidentified/numbered as required

•• is marked with welderis marked with welder’’s identitys identity

Visual InspectionVisual Inspection

•• ensure weld is suitable for ensure weld is suitable for allall NDTNDT

•• visually inspect & visually inspect & ‘‘sentencesentence’’ to Code requirementsto Code requirements

Dimensional SurveyDimensional Survey

•• ensure dimensions comply with Code/drawingensure dimensions comply with Code/drawing

Other NDTOther NDT

•• ensure all NDT is completed & reports availableensure all NDT is completed & reports available

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After WeldingAfter WeldingRepairsRepairs

monitor repairs to ensure compliance with Procedure, monitor repairs to ensure compliance with Procedure, ensure NDT after repairs is completedensure NDT after repairs is completed

PWHTPWHT

monitor for compliance with Proceduremonitor for compliance with Procedure

check chart records confirm Procedure compliancecheck chart records confirm Procedure compliance

Pressure / Load TestPressure / Load Test

ensure test equipment is suitably calibratedensure test equipment is suitably calibrated

monitor to ensure compliance with Proceduremonitor to ensure compliance with Procedure

ensure all records are availableensure all records are available

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After WeldingAfter Welding

DocumentationDocumentation

ensure any modifications are on ensure any modifications are on ‘‘asas--builtbuilt’’ drawingsdrawings

ensure all required documents are availableensure all required documents are available

Collate / file documents for manufacturing recordsCollate / file documents for manufacturing records

Sign all documentation and forward it to QC Sign all documentation and forward it to QC department. department.

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Summary of DutiesSummary of Duties

A Welding Inspector must: A Welding Inspector must: ObserveObserveTo observe all relevant actions related to weld quality To observe all relevant actions related to weld quality throughout production. throughout production.

RecordRecordTo record, or log all production inspection points relevant to To record, or log all production inspection points relevant to quality, including a final report showing all identified quality, including a final report showing all identified imperfectionsimperfections

CompareCompareTo compare all recorded information with the acceptance To compare all recorded information with the acceptance criteria and any other relevant clauses in the applied criteria and any other relevant clauses in the applied application standardapplication standard

It is the duty of a Welding Inspector to ensure all the welding It is the duty of a Welding Inspector to ensure all the welding and and associated actions are carried out in accordance with the associated actions are carried out in accordance with the specification and any applicable procedures.specification and any applicable procedures.

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Terms & DefinitionsTerms & DefinitionsSection 2Section 2

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Welding Terminology & DefinitionsWelding Terminology & Definitions 2.12.1

What is a Weld?What is a Weld?

•• A localised coalescence of metals or nonA localised coalescence of metals or non--metals produced metals produced either by heating the materials to the welding temperature, either by heating the materials to the welding temperature, with or without the application of pressure, or by the with or without the application of pressure, or by the application of pressure alone (AWS)application of pressure alone (AWS)

•• A permanent union between materials caused by heat, and A permanent union between materials caused by heat, and or pressure (BS499)or pressure (BS499)

•• An Autogenous weld:An Autogenous weld:A weld made with out the use of a filler material and can A weld made with out the use of a filler material and can only be made by TIG or Oxyonly be made by TIG or Oxy--Gas WeldingGas Welding

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Welding Terminology & Definitions Welding Terminology & Definitions 2.12.1

What is a Joint?What is a Joint?

The junction of members or the edges of members The junction of members or the edges of members that are to be joined or have been joined (AWS)that are to be joined or have been joined (AWS)

A configuration of members (BS499)A configuration of members (BS499)

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Joint Terminology Joint Terminology 2.22.2

EdgeEdge Open & Closed CornerOpen & Closed Corner LapLap

TeeTee ButtButtCruciformCruciform

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Welded Butt Joints Welded Butt Joints 2.22.2

A_________A_________Welded butt jointWelded butt jointButtButt

A_________A_________Welded butt jointWelded butt jointFilletFillet

A____________A____________Welded butt jointWelded butt jointCompoundCompound

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A_________A_________Welded T jointWelded T jointFilletFillet

A_________A_________Welded T jointWelded T jointButtButt

A____________A____________Welded T jointWelded T jointCompoundCompound

Welded Tee Joints Welded Tee Joints 2.22.2

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Weld Terminology Weld Terminology 2.32.3

Compound weldCompound weld

Fillet weldFillet weldButt weldButt weld

Edge weldEdge weld

Spot weldSpot weld

Plug weldPlug weld

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Butt Preparations Butt Preparations –– Sizes Sizes 2.42.4

Full Penetration Butt Weld

Partial Penetration Butt Weld

Design Throat

Thickness

Design Throat

Thickness

Actual Throat

Thickness

Actual Throat

Thickness

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Weld Weld BoundaryBoundary

C

A B

D

Heat Heat Affected Affected ZoneZone

RootRoot

Weld Weld metalmetal

A, B, C & D = Weld ToesA, B, C & D = Weld Toes

FaceFace

Weld Zone Terminology Weld Zone Terminology 2.52.5

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Excess Root Excess Root PenetrationPenetration

ExcessExcessCap heightCap heightor Weld or Weld ReinforcementReinforcement

Weld Zone Terminology Weld Zone Terminology 2.52.5

Weld cap widthWeld cap width

Design Throat Thickness

Actual Throat Thickness

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Heat Affected Zone (HAZ) Heat Affected Zone (HAZ) 2.52.5

tempered zonetempered zone

grain growth zonegrain growth zone

recrystallised zonerecrystallised zonepartially transformed zonepartially transformed zone

Maximum Maximum TemperatureTemperature

solidsolid--liquid Boundaryliquid Boundarysolid solid weld weld metalmetal

unaffected baseunaffected basematerialmaterial

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Joint Preparation Terminology Joint Preparation Terminology 2.72.7

Included angleIncluded angle

Root GapRoot GapRoot FaceRoot Face

Angle ofAngle ofbevelbevel

Root FaceRoot FaceRoot GapRoot Gap

Included angleIncluded angle

Root Root RadiusRadius

SingleSingle--V ButtV Butt SingleSingle--U ButtU Butt

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Joint Preparation Terminology Joint Preparation Terminology 2.8 & 2.92.8 & 2.9

Root GapRoot GapRoot FaceRoot Face Root FaceRoot FaceRoot GapRoot Gap

Root Root RadiusRadius

Single Bevel ButtSingle Bevel Butt SingleSingle--J ButtJ Butt

Angle of bevelAngle of bevel Angle of bevel

LandLand

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Single Sided Butt Preparations Single Sided Butt Preparations 2.102.10

Single BevelSingle Bevel Single VeeSingle Vee

SingleSingle--JJ SingleSingle--UU

Single sided preparations are normally made on thinner materialsSingle sided preparations are normally made on thinner materials, or , or when access form both sides is restrictedwhen access form both sides is restricted

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Double Sided Butt PreparationsDouble Sided Butt Preparations 2.112.11

Double sided preparations are normally made on thicker materialsDouble sided preparations are normally made on thicker materials, or , or when access form both sides is unrestrictedwhen access form both sides is unrestricted

--VeeVeeDoubleDouble--BevelBevelDoubleDouble

-- JJDoubleDouble -- UUDoubleDouble

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Weld PreparationWeld Preparation

Terminology & Typical Dimensions:Terminology & Typical Dimensions: VV--JointsJoints

bevel anglebevel angle

root faceroot face

root gaproot gap

included angleincluded angle

Typical DimensionsTypical Dimensions

bevel anglebevel angle 30 to 3530 to 35°°

root faceroot face ~1.5 to ~2.5mm~1.5 to ~2.5mm

root gaproot gap ~2 to ~4mm~2 to ~4mm

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6 mm6 mm

8080°°

Poor Weld Toe Blend AnglePoor Weld Toe Blend Angle

Improved Weld Toe Blend Improved Weld Toe Blend AngleAngle

2020°°

3 mm3 mm

••Most codes quote the weld Most codes quote the weld toes toes shall blend smoothlyshall blend smoothly

••This statement is not This statement is not quantitative and therefore quantitative and therefore open open to individual to individual interpretationinterpretation

••The higher the toe blend The higher the toe blend angle angle the greater thethe greater theamountamount of of stress stress concentrationconcentration

••The toe blend angle ideally The toe blend angle ideally should should be be between 20between 20oo--3030oo

Butt Weld Butt Weld -- Toe BlendToe Blend

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Fillet Weld Features Fillet Weld Features 2.132.13

Design Design ThroatThroat

Vertical Vertical Leg Leg

LengthLength

Horizontal leg Horizontal leg LengthLength

ExcessExcessWeld Weld MetalMetal

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Fillet Weld Throat Thickness Fillet Weld Throat Thickness 2.132.13

bbaa

b = Actual Throat Thicknessb = Actual Throat Thicknessa = Design Throat Thicknessa = Design Throat Thickness

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bbaa

b = Actual Throat Thicknessb = Actual Throat Thicknessa = Design Throat Thicknessa = Design Throat Thickness

Deep Penetration Fillet Weld FeaturesDeep Penetration Fillet Weld Features 2.132.13

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Fillet Weld Sizes Fillet Weld Sizes 2.142.14

Calculating Calculating Throat ThicknessThroat Thickness from a known Leg from a known Leg Length:Length:

Design Throat Thickness = Leg Length x 0.7Design Throat Thickness = Leg Length x 0.7

Question:Question: The Leg length is 14mm. The Leg length is 14mm.

What is the Design Throat?What is the Design Throat?

Answer: Answer: 14mm x 0.7 =14mm x 0.7 = 10mm 10mm Throat Thickness Throat Thickness

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Calculating Calculating Leg LengthLeg Length from a known Design from a known Design Throat Thickness:Throat Thickness:

Leg Length = Design Throat Thickness x 1.4Leg Length = Design Throat Thickness x 1.4

Question:Question: The Design Throat is 10mm. The Design Throat is 10mm.

What is the Leg length?What is the Leg length?

Answer: Answer: 10mm x 1.4 =10mm x 1.4 = 14mm 14mm Leg LengthLeg Length

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Features to Consider 2 Features to Consider 2 2.142.14

Approximately the same weld volume in both Fillet Approximately the same weld volume in both Fillet Welds, but theWelds, but the effective throat thickness has been effective throat thickness has been

altered, reducing considerably the strength of weld Baltered, reducing considerably the strength of weld B

Importance of Fillet Weld Leg Length SizeImportance of Fillet Weld Leg Length Size

2mm2mm

(b)(b)

4mm4mm

8mm8mm

(a)(a)

4mm4mm

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AreaArea = = 4 x 4 4 x 4 ==8mm8mm22

22

AreaArea = = 6 x 6 6 x 6 ==18mm18mm22

22The c.s.a. ofThe c.s.a. of (b)(b) is overis over doubledouble the area ofthe area of (a) (a) without the extra without the extra

excess weld metal being addedexcess weld metal being added

4mm

(a)

6mm

(b)

Importance of Fillet weld leg length SizeImportance of Fillet weld leg length Size

4mm(a)

Excess

6mm(b)

Excess

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MitreMitre FilletFillet Convex FilletConvex Fillet

Concave FilletConcave Fillet

A concave profile A concave profile is preferred for is preferred for joints subjected to joints subjected to fatigue loading fatigue loading

Fillet Weld Profiles Fillet Weld Profiles 2.152.15

Fillet welds Fillet welds -- ShapeShape

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EFFECTIVE THROAT THICKNESSEFFECTIVE THROAT THICKNESS“s” = Effective throat thickness

sa

“a” = Nominal throat thickness

Deep penetration fillet welds from high heat input welding process MAG, FCAW & SAW etc

Fillet Features to Consider 2.15

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Welding Positions Welding Positions 2.172.17

PAPA 1G / 1F1G / 1F Flat / DownhandFlat / Downhand

PBPB 2F2F HorizontalHorizontal--VerticalVertical

PCPC 2G2G HorizontalHorizontal

PDPD 4F4F HorizontalHorizontal--Vertical (Overhead)Vertical (Overhead)

PEPE 4G4G OverheadOverhead

PFPF 3G / 5G3G / 5G VerticalVertical--UpUp

PGPG 3G / 5G3G / 5G VerticalVertical--DownDown

HH--L045L045 6G6G Inclined Pipe (Upwards)Inclined Pipe (Upwards)

JJ--L045L045 6G6G Inclined Pipe (Downwards)Inclined Pipe (Downwards)

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Welding Positions Welding Positions 2.172.17

ISO

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Welding position designationWelding position designation 2.172.17

Butt welds in plate (see ISO 6947)Butt welds in plate (see ISO 6947)

Flat - PA Overhead - PE

Vertical up - PF

Vertical down - PG

Horizontal - PC

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Welding position designation Welding position designation 2.172.17

Butt welds in pipe (see ISO 6947)Butt welds in pipe (see ISO 6947)

Flat - PAaxis: horizontal pipe: rotated

H-L045axis: inclined at 45°pipe: fixed

Horizontal - PCaxis: vertical pipe: fixed

Vertical up - PFaxis: horizontal pipe: fixed

Vertical down - PGaxis: horizontal pipe: fixed

J-L045axis: inclined at 45°pipe: fixed

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Welding position designationWelding position designation 2.172.17

Fillet welds on plate (see ISO 6947)Fillet welds on plate (see ISO 6947)

Flat - PA Overhead - PD

Vertical up - PF Vertical down - PG

Horizontal - PB

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Welding position designation Welding position designation 2.172.17

Fillet welds on pipe (see ISO 6947)Fillet welds on pipe (see ISO 6947)

Flat - PA axis: inclined at 45°pipe: rotated

Overhead - PD axis: vertical pipe: fixed

Vertical up - PF axis: horizontal pipe: fixed

Vertical down - PG axis: horizontal pipe: fixed

Horizontal - PB axis: vertical pipe: fixed

Horizontal - PB axis: horizontal pipe: rotated

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PA / 1GPA / 1GPA / 1FPA / 1F

PC / 2GPC / 2GPB / 2FPB / 2F

PD / 4FPD / 4FPE / 4GPE / 4G PG / 3GPG / 3G

PF / 3GPF / 3G

Plate/Fillet Weld PositionsPlate/Fillet Weld Positions 2.172.17

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Pipe Welding Positions Pipe Welding Positions 2.172.17

Weld: FlatWeld: FlatPipe: rotatedPipe: rotatedAxis: Horizontal Axis: Horizontal

PA / 1GPA / 1GWeld: Vertical DownwardsWeld: Vertical DownwardsPipe: FixedPipe: FixedAxis: Horizontal Axis: Horizontal

PG / 5G PG / 5G

Weld: Vertical upwardsWeld: Vertical upwardsPipe: FixedPipe: FixedAxis: Horizontal Axis: Horizontal

PF / 5G PF / 5G

Weld: Upwards Weld: Upwards Pipe: FixedPipe: FixedAxis: Inclined Axis: Inclined

Weld: HorizontalWeld: HorizontalPipe: FixedPipe: FixedAxis: Vertical Axis: Vertical

PC / 2G PC / 2G

4545oo

Weld: Downwards Weld: Downwards Pipe: FixedPipe: FixedAxis: Inclined Axis: Inclined

JJ--LO 45 / 6GLO 45 / 6G

4545oo

HH--LO 45 / 6GLO 45 / 6G

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Travel Speed MeasurementTravel Speed Measurement 2.182.18

Definition:Definition: the rate of weld progressionthe rate of weld progressionmeasured in case of mechanised and automatic measured in case of mechanised and automatic welding processeswelding processesin case of MMA can be determined using ROL and arc in case of MMA can be determined using ROL and arc timetime

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Welding ImperfectionsWelding ImperfectionsSection 3Section 3

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Welding Imperfections Welding Imperfections 3.13.1

All welds have imperfectionsAll welds have imperfections

•• Imperfections are classed as Imperfections are classed as defectsdefects when they are of a when they are of a type, or size, not allowed by the Acceptance Standardtype, or size, not allowed by the Acceptance Standard

A defect is an unacceptable imperfectionA defect is an unacceptable imperfection

•• A weld imperfection may be allowed by one Acceptance A weld imperfection may be allowed by one Acceptance Standard but be classed as a defect by another Standard Standard but be classed as a defect by another Standard and require removal/rectificationand require removal/rectification

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Standards for Welding ImperfectionsStandards for Welding Imperfections

BSBS EN ISO 6520EN ISO 6520--11(1998) (1998) Welding and allied processes Welding and allied processes ––Classification of geometric Classification of geometric imperfections in metallic materials imperfections in metallic materials --Part 1: Fusion weldingPart 1: Fusion welding

Imperfections are classified into 6 groups, namely:Imperfections are classified into 6 groups, namely:

1 Cracks1 Cracks2 Cavities2 Cavities3 Solid inclusions3 Solid inclusions4 Lack of fusion and penetration4 Lack of fusion and penetration5 Imperfect shape and dimensions5 Imperfect shape and dimensions6 Miscellaneous imperfections6 Miscellaneous imperfections

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Standards for Welding ImperfectionsStandards for Welding Imperfections

EN ISO 5817 EN ISO 5817 (2003)(2003) Welding Welding -- FusionFusion--welded joints in steel, welded joints in steel, nickel, titanium and their alloys (beam nickel, titanium and their alloys (beam welding excluded) welding excluded) -- Quality levels for Quality levels for imperfectionsimperfections

This main imperfections given in EN ISO 6520This main imperfections given in EN ISO 6520--1 are listed in1 are listed inEN ISO 5817 with acceptance criteria at 3 levels, namelyEN ISO 5817 with acceptance criteria at 3 levels, namely

Level B (highest)Level B (highest)

Level C (intermediate)Level C (intermediate)

Level D (general)Level D (general)

This Standard is This Standard is ‘‘directly applicable to directly applicable to visualvisual testing of weldstesting of welds’’......(weld surfaces & macro examination)(weld surfaces & macro examination)

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Welding imperfections Welding imperfections 3.13.1

classificationclassification

CracksCracks

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Cracks Cracks 3.13.1

Cracks that may occur in welded materials Cracks that may occur in welded materials are caused generally by many factors and are caused generally by many factors and may be classified by shape and position.may be classified by shape and position.

Note:Note: Cracks are classed as Planar Cracks are classed as Planar Defects.Defects.

Classified by ShapeClassified by Shape••LongitudinalLongitudinal••TransverseTransverse••ChevronChevron••Lamellar TearLamellar Tear

Classified by PositionClassified by Position••HAZHAZ••CenterlineCenterline••CraterCrater••Fusion zoneFusion zone••Parent metalParent metal

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Longitudinal parent metalLongitudinal parent metal

Longitudinal weld metalLongitudinal weld metalLamellar tearing Lamellar tearing

Transverse weld metalTransverse weld metal


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Transverse crackTransverse crack Longitudinal crackLongitudinal crack


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Main Crack TypesMain Crack TypesSolidification CracksSolidification CracksHydrogen Induced CracksHydrogen Induced CracksLamellar TearingLamellar TearingReheat cracksReheat cracks


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Solidification CrackingSolidification Cracking

Occurs during weld solidification processOccurs during weld solidification process

Steels with high Steels with high sulphursulphur impurities content (low impurities content (low ductility at elevated temperature)ductility at elevated temperature)

Requires high tensile stressRequires high tensile stress

Occur longitudinally down centre of weldOccur longitudinally down centre of weld


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Hydrogen Induced Cold CrackingHydrogen Induced Cold Cracking

Requires susceptible hard grain structure, stress, low Requires susceptible hard grain structure, stress, low temperature and hydrogen temperature and hydrogen

Hydrogen enters weld via welding arc mainly as Hydrogen enters weld via welding arc mainly as result of contaminated electrode or preparationresult of contaminated electrode or preparation

Hydrogen diffuses out into parent metal on coolingHydrogen diffuses out into parent metal on cooling

Cracking developing most likely in HAZCracking developing most likely in HAZ

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Lamellar TearingLamellar Tearing 3.53.5

Location:Location: Parent metalParent metal

Steel Type:Steel Type: Any steel type possibleAny steel type possible

Susceptible Microstructure:Susceptible Microstructure: Poor through thickness Poor through thickness ductilityductility

•• Lamellar tearing has a step like appearance due to the Lamellar tearing has a step like appearance due to the solid inclusions in the parent material (e.g. sulphides solid inclusions in the parent material (e.g. sulphides and silicates) linking up under the influence of welding and silicates) linking up under the influence of welding stresses stresses

•• Low ductile materials in the short transverse direction Low ductile materials in the short transverse direction containing high levels of impurities are very susceptible containing high levels of impurities are very susceptible to lamellar tearingto lamellar tearing

•• It forms when the welding stresses act in the short It forms when the welding stresses act in the short transverse direction of the material (through thickness transverse direction of the material (through thickness direction)direction)

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Gas Cavities Gas Cavities 3.63.6

Root pipingRoot piping

Cluster porosityCluster porosityGas poreGas pore

Blow holeBlow holeHerringbone porosityHerringbone porosity

Gas pore <1.5mm Gas pore <1.5mm Blow hole.>1.6mmBlow hole.>1.6mm

Causes:Causes:

••Loss of gas shieldLoss of gas shield

••Damp electrodesDamp electrodes

••ContaminationContamination

••Arc length too largeArc length too large

••Damaged electrode fluxDamaged electrode flux

••Moisture on parent materialMoisture on parent material

••Welding current too lowWelding current too low

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Root pipingRoot piping

PorosityPorosity


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Cluster porosityCluster porosity Herringbone porosityHerringbone porosity


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Crater pipeCrater pipe

Weld craterWeld crater

Crater Pipe Crater Pipe 3.93.9

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Crater pipe is a shrinkage defect and not a gas defect, it has Crater pipe is a shrinkage defect and not a gas defect, it has the appearance of a gas pore in the weld craterthe appearance of a gas pore in the weld crater

Causes:Causes:

•• Too fast a cooling Too fast a cooling raterate

•• Deoxidization Deoxidization reactions and reactions and liquid to solid liquid to solid volume changevolume change

•• ContaminationContamination

Crater cracksCrater cracks(Star cracks)(Star cracks)

Crater pipeCrater pipe

Crater Pipe Crater Pipe 3.93.9

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Solid InclusionsSolid Inclusions 3.103.10

Slag inclusions are defined as a nonSlag inclusions are defined as a non--metallic inclusion metallic inclusion caused by some welding process caused by some welding process

Causes:Causes:

••Slag originates from Slag originates from welding fluxwelding flux

••MAG and TIG welding MAG and TIG welding process produce silica process produce silica inclusionsinclusions

••Slag is caused by Slag is caused by inadequate cleaninginadequate cleaning

••Other inclusions include Other inclusions include tungsten and copper tungsten and copper inclusions from the TIG inclusions from the TIG and MAG welding processand MAG welding process

Slag inclusionsSlag inclusions

Parallel slag linesParallel slag lines

Lack of sidewall Lack of sidewall fusion with fusion with

associated slagassociated slag

Lack of Lack of interuninterunfusion + slag fusion + slag

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Elongated slag linesElongated slag linesInterpass slag inclusionsInterpass slag inclusions

Solid Inclusions Solid Inclusions 3.113.11

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Typical Causes of Lack of Fusion:Typical Causes of Lack of Fusion:

• welding current too low

• bevel angle too steep

• root face too large (single-sided weld)

• root gap too small (single-sided weld)

• incorrect electrode angle

• linear misalignment

• welding speed too high

• welding process related – particularly dip-transfer GMAW

• flooding the joint with too much weld metal (blocking Out)

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Lack of FusionLack of Fusion 3.133.13

Incomplete filled groove + Incomplete filled groove + Lack of sidewall fusionLack of sidewall fusion

11

22

1.1. Lack of sidewall fusionLack of sidewall fusion2.2. Lack of interLack of inter--run fusionrun fusion

Causes:Causes:

••Poor welder skillPoor welder skill

•• Incorrect electrode Incorrect electrode manipulationmanipulation

•• Arc blowArc blow

•• Incorrect welding Incorrect welding current/voltagecurrent/voltage

•• Incorrect travel speedIncorrect travel speed

•• Incorrect interIncorrect inter--run cleaningrun cleaning

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Lack of sidewall fusion + incomplete filled grooveLack of sidewall fusion + incomplete filled groove

Lack of Fusion Lack of Fusion 3.133.13

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Weld Root Imperfections Weld Root Imperfections 3.153.15

Lack of Root FusionLack of Root Fusion Lack of Root PenetrationLack of Root Penetration

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Cap UndercutCap Undercut 3.183.18

Intermittent Cap UndercutIntermittent Cap Undercut

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Cap undercutCap undercutRoot undercutRoot undercut

Undercut Undercut 3.183.18

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Surface and Profile Surface and Profile 3.193.19

Incomplete filled grooveIncomplete filled groove Poor cap profilePoor cap profile

Excessive cap heightExcessive cap height

Poor cap profiles and Poor cap profiles and excessive cap reinforcements excessive cap reinforcements may lead to stress may lead to stress concentration points at the concentration points at the weld toes and will also weld toes and will also contribute to overall poor toe contribute to overall poor toe blendblend

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Incomplete filled grooveIncomplete filled grooveExcess cap reinforcementExcess cap reinforcement

Surface and Profile Surface and Profile 3.193.19

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Excessive root Excessive root penetrationpenetration

Weld Root ImperfectionsWeld Root Imperfections 3.203.20

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Overlap Overlap 3.213.21

An imperfection at the toe or root of a weld caused by metal An imperfection at the toe or root of a weld caused by metal flowing on to the surface of the parent metal without fusing to flowing on to the surface of the parent metal without fusing to itit

Causes:Causes:

••ContaminationContamination

••Slow travel speedSlow travel speed

••Incorrect welding Incorrect welding techniquetechnique

••Current too lowCurrent too low

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Overlap Overlap 3.213.21

Toe OverlapToe Overlap

Toe OverlapToe Overlap

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SetSet--Up Irregularities Up Irregularities 3.223.22

Plate/pipe Linear MisalignmentPlate/pipe Linear Misalignment(Hi(Hi--Lo)Lo)

Angular MisalignmentAngular Misalignment

Linear misalignmentLinear misalignment is is measured from the lowest measured from the lowest plate to the highest point.plate to the highest point.

Angular misalignmentAngular misalignment is is measured in degreesmeasured in degrees

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SetSet--Up IrregularitiesUp Irregularities 3.223.22

Linear MisalignmentLinear Misalignment

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Linear MisalignmentLinear Misalignment

SetSet--Up IrregularitiesUp Irregularities 3.223.22

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Lack of sidewall fusion + incomplete filled grooveLack of sidewall fusion + incomplete filled groove

Incomplete GrooveIncomplete Groove 3.233.23

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Concave RootConcave Root

Causes:Causes:

•• Excessive back purge Excessive back purge pressure during TIG weldingpressure during TIG welding

Excessive root bead grinding Excessive root bead grinding before the application of the before the application of the second passsecond pass

welding current too high for welding current too high for 2nd pass2nd pass overhead weldingoverhead welding

root gap too large root gap too large -- excessive excessive ‘‘weavingweaving’’

A shallow groove, which may occur in the root of a butt weldA shallow groove, which may occur in the root of a butt weld


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Concave RootConcave Root


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Concave rootConcave root Excess root penetrationExcess root penetration


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Causes:Causes:

•• High Amps/voltsHigh Amps/volts

•• Small Root faceSmall Root face

•• Large Root GapLarge Root Gap

•• Slow Travel Slow Travel SpeedSpeedBurn throughBurn through

A localized collapse of the weld pool due to excessive A localized collapse of the weld pool due to excessive penetration resulting in a hole in the root runpenetration resulting in a hole in the root run


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Burn ThroughBurn Through


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Causes:Causes:

•• Loss or insufficient Loss or insufficient back purging gas (TIG)back purging gas (TIG)

•• Most commonly occurs Most commonly occurs when welding stainless when welding stainless steelssteels

•• Purging gases include Purging gases include argon, helium and argon, helium and occasionally nitrogen occasionally nitrogen

Oxidized Root (Root Coking)Oxidized Root (Root Coking)

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Miscellaneous Imperfections Miscellaneous Imperfections 3.263.26

Arc strikeArc strike

Causes:Causes:

•• Accidental striking of the Accidental striking of the arc onto the parent arc onto the parent materialmaterial

•• Faulty electrode holder Faulty electrode holder

•• Poor cable insulationPoor cable insulation

•• Poor return lead Poor return lead clampingclamping

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Miscellaneous ImperfectionsMiscellaneous Imperfections 3.273.27

Causes:Causes:

•• Excessive currentExcessive current

•• Damp electrodes Damp electrodes

•• ContaminationContamination

•• Incorrect wire feed Incorrect wire feed speed when welding speed when welding with the MAG welding with the MAG welding processprocess

•• Arc blowArc blowSpatterSpatter

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Mechanical DamageMechanical Damage 3.283.28

Mechanical damage can be defined as any surface Mechanical damage can be defined as any surface materialmaterial

damage cause during the manufacturing process.damage cause during the manufacturing process.

•• GrindingGrinding

•• HammeringHammering

•• ChisellingChiselling

•• ChippingChipping

•• Breaking off welded attachments Breaking off welded attachments

(torn surfaces)(torn surfaces)

•• Using needle guns to compress Using needle guns to compress

weld capping runsweld capping runs

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Mechanical Damage Mechanical Damage 3.283.28

Mechanical Damage/Grinding MarkMechanical Damage/Grinding Mark

Chipping MarksChipping Marks

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Destructive Testing Destructive Testing Section 4Section 4

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Qualitative and Quantitative TestsQualitative and Quantitative Tests 4.14.1

The following mechanical tests have units and are termedThe following mechanical tests have units and are termedquantitativequantitative tests to tests to measure Mechanical Propertiesmeasure Mechanical Properties

Tensile tests (Transverse Welded Joint, All Weld Metal)Tensile tests (Transverse Welded Joint, All Weld Metal)Toughness testing (Charpy, Izod, CTOD) Toughness testing (Charpy, Izod, CTOD) Hardness tests (Brinell, Rockwell, Vickers)Hardness tests (Brinell, Rockwell, Vickers)

The following mechanical tests have no units and are termedThe following mechanical tests have no units and are termedqualitativequalitative tests for tests for assessing joint qualityassessing joint quality

Macro testingMacro testingBend testingBend testingFillet weld fracture testingFillet weld fracture testingButt weld nickButt weld nick--break testingbreak testing

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Tensile SpecimensTensile Specimens

Fracture Fillet Fracture Fillet SpecimenSpecimen

CTOD SpecimenCTOD Specimen

Charpy SpecimenCharpy Specimen

Bend Test Bend Test SpecimenSpecimen

Mechanical Test Samples Mechanical Test Samples 4.14.1

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Destructive TestingDestructive Testing 4.14.1

Typical Positions for Test Typical Positions for Test PiecesPieces

Specimen Type PositionSpecimen Type Position

••Macro + HardnessMacro + Hardness 55

••Transverse TensileTransverse Tensile 2, 4 2, 4

••Bend TestsBend Tests 2, 42, 4

••Charpy Impact TestsCharpy Impact Tests 33

••Additional TestsAdditional Tests 33

WELDING PROCEDURE QUALIFICATION TESTINGWELDING PROCEDURE QUALIFICATION TESTING

22

33

44

55

top of fixed pipetop of fixed pipe

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•• MalleabilityMalleability•• DuctilityDuctility•• ToughnessToughness•• HardnessHardness•• Tensile StrengthTensile Strength

Ability of a material to Ability of a material to withstand deformation withstand deformation under static compressive under static compressive loading without ruptureloading without rupture

DefinitionsDefinitionsMechanical Properties of metalsMechanical Properties of metals are related to the amount of are related to the amount of deformation which metals can withstand under different deformation which metals can withstand under different circumstances of force application.circumstances of force application.

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Ability of a material Ability of a material undergo plastic undergo plastic deformation under static deformation under static tensile loading without tensile loading without rupture. Measurable rupture. Measurable elongation and reduction elongation and reduction in cross section areain cross section area


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Ability of a material to Ability of a material to withstand bending or the withstand bending or the application of shear application of shear stresses by impact loading stresses by impact loading without fracture.without fracture.


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Measurement of a Measurement of a materials surface materials surface resistance to indentation resistance to indentation from another material by from another material by static loadstatic load


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Measurement Measurement of the of the maximum force required maximum force required to fracture a materials bar to fracture a materials bar of unit crossof unit cross--sectional sectional area in tension area in tension


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Transverse Joint Tensile TestTransverse Joint Tensile Test 4.24.2

Weld on plateWeld on plate

Multiple cross joint Multiple cross joint specimensspecimensWeld on pipeWeld on pipe

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AllAll--Weld Metal Tensile Weld Metal Tensile SpecimenSpecimen

Transverse Tensile Transverse Tensile SpecimenSpecimen

Tensile Test Tensile Test 4.34.3

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STRA (Short Transverse Reduction Area)STRA (Short Transverse Reduction Area)For materials that may be subject to Lamellar TearingFor materials that may be subject to Lamellar Tearing

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UTS Tensile test UTS Tensile test 4.44.4

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Charpy VCharpy V--Notch Impact TestNotch Impact Test 4.54.5

Objectives:Objectives:•• measuring impact strength in different weld joint areasmeasuring impact strength in different weld joint areas•• assessing resistance toward brittle fractureassessing resistance toward brittle fracture

Information to be supplied on the test report:Information to be supplied on the test report:•• Material typeMaterial type•• Notch typeNotch type•• Specimen sizeSpecimen size•• Test temperatureTest temperature•• Notch locationNotch location•• Impact Strength ValueImpact Strength Value

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-- 5050 00-- 2020 -- 1010-- 4040 -- 3030

Ductile fractureDuctile fracture

Ductile/BrittleDuctile/Brittletransition transition pointpoint

47 Joules47 Joules

28 Joules28 Joules

Temperature rangeTemperature range

Transition rangeTransition range

Brittle fractureBrittle fractureEnergy absorbedEnergy absorbed

Testing temperatureTesting temperature - Degrees CentigradeDegrees Centigrade

Ductile / Brittle Transition CurveDuctile / Brittle Transition Curve 4.64.6

Three specimens are normally tested at each temperatureThree specimens are normally tested at each temperature

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Impact Energy JoulesImpact Energy Joules

Room TemperatureRoom Temperature --2020ooC TemperatureC Temperature

1.1. 197 Joules197 Joules2.2. 191 191 JoulesJoules3.3. 186 186 JoulesJoules

1.1. 49 49 JoulesJoules2.2. 53 53 JoulesJoules3.3. 51 51 JoulesJoules

Average =Average = 191 191 JoulesJoules Average =Average = 51 51 JoulesJoules

The test results show the specimens carried out at room The test results show the specimens carried out at room temperature absorb more energy than the specimens carried temperature absorb more energy than the specimens carried out at out at --2020ooCC

Comparison Charpy Impact Test ResultsComparison Charpy Impact Test Results 4.64.6

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Charpy VCharpy V--notch impact test specimennotch impact test specimen 4.74.7

Specimen dimensions according ASTM E23Specimen dimensions according ASTM E23

ASTM: American Society of Testing MaterialsASTM: American Society of Testing Materials

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Charpy VCharpy V--Notch Impact Test Notch Impact Test 4.84.8

SpecimeSpecimenn

PenduluPendulumm

(striker)(striker)

Anvil (support)Anvil (support)

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10 mm10 mm8

mm

8 m

m2

mm

2 m

m22.522.5oo

Machined Machined notchnotch

100% Ductile100% DuctileMachined Machined

notchnotch

Large reduction Large reduction in area, shear in area, shear lipslips

Fracture surface Fracture surface 100% bright 100% bright crystalline brittle crystalline brittle fracturefracture

Randomly torn, Randomly torn, dull gray fracture dull gray fracture surfacesurface

Charpy Impact TestCharpy Impact Test 4.94.9

100% Brittle100% Brittle

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Hardness TestingHardness Testing 4.104.10

DefinitionDefinition

Measurement of resistance of a material against Measurement of resistance of a material against penetration of an indenter under a constant loadpenetration of an indenter under a constant load

There is a direct correlation between UTS and There is a direct correlation between UTS and hardnesshardness

Hardness tests:Hardness tests:

BrinellBrinell

VickersVickers

RockwellRockwell

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Hardness Testing Hardness Testing 4.104.10

Objectives:Objectives:•• measuring hardness in different areas of a welded jointmeasuring hardness in different areas of a welded joint

•• assessing resistance toward brittle fracture, cold cracking assessing resistance toward brittle fracture, cold cracking and corrosion sensitivity within a Hand corrosion sensitivity within a H22S (Hydrogen Sulphide) S (Hydrogen Sulphide) environment.environment.

Information to be supplied on the test report:Information to be supplied on the test report:•• material typematerial type

•• location of indentationlocation of indentation

•• type of hardness test and load applied on the indentertype of hardness test and load applied on the indenter

•• hardness valuehardness value

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Vickers hardness tests:Vickers hardness tests:

indentation body is a square based diamond pyramid indentation body is a square based diamond pyramid (136(136ºº included angle)included angle)

the average diagonal (d) of the impression is the average diagonal (d) of the impression is converted to a hardness number from a tableconverted to a hardness number from a table

it is measured in HV5, HV10 or HV025it is measured in HV5, HV10 or HV025Adjustable Adjustable shuttersshuttersIndentationIndentationDiamond Diamond

indentorindentor

Vickers Hardness Test Vickers Hardness Test 4.114.11

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Vickers Hardness Test MachineVickers Hardness Test Machine 4.114.11

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•• Hardened steel ball of given diameter is subjected for Hardened steel ball of given diameter is subjected for a given time to a given loada given time to a given load

•• Load divided by area of indentation gives Brinell Load divided by area of indentation gives Brinell hardness in kg/mmhardness in kg/mm22

•• More suitable for on site hardness testingMore suitable for on site hardness testing

Brinell Hardness Test Brinell Hardness Test 4.114.11

30KN30KN

Ø=10mm steel ball

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Rockwell Hardness TestRockwell Hardness Test

1KN1KN

Ø=1.6mm steel ball

Rockwell BRockwell B Rockwell CRockwell C

1.5KN1.5KN

120°Diamond Cone

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Hardness Testing Hardness Testing 4.124.12

Hardness Test Methods Typical DesignationsHardness Test Methods Typical Designations

VickersVickers 240 HV10240 HV10

RockwellRockwell Rc 22Rc 22

BrinellBrinell 200 BHN200 BHN--WW

usually the hardest regionusually the hardest region

1.5 to 3mm1.5 to 3mm

HAZHAZ

fusion line fusion line or or

fusion fusion boundaryboundary

Hardness specimens can also be used for CTOD samples

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Crack Tip Opening Displacement testing Crack Tip Opening Displacement testing 4.124.12

Test is for fracture toughnessTest is for fracture toughnessSquare bar machined with a notch placed Square bar machined with a notch placed in the centre.in the centre.Tested below ambient temperature at a Tested below ambient temperature at a specified temperature.specified temperature.Load is applied at either end of the test Load is applied at either end of the test specimen in an attempt to open a crack at specimen in an attempt to open a crack at the bottom of the notchthe bottom of the notchNormally 3 samplesNormally 3 samples

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Location: Location: Any stress concentration areaAny stress concentration area

Steel Type: Steel Type: All steel typesAll steel types

Susceptible Microstructure: Susceptible Microstructure: All grain structuresAll grain structures

Test for Fracture Toughness is CTOD Test for Fracture Toughness is CTOD (Crack Tip Opening Displacement)(Crack Tip Opening Displacement)

Fatigue FractureFatigue Fracture 4.134.13

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•• Fatigue cracks occur under cyclic stress conditionsFatigue cracks occur under cyclic stress conditions

•• Fracture normally occurs at a change in section, notch Fracture normally occurs at a change in section, notch and weld defects i.e stress concentration area and weld defects i.e stress concentration area

•• All materials are susceptible to fatigue crackingAll materials are susceptible to fatigue cracking

•• Fatigue cracking starts at a specific point referred to as Fatigue cracking starts at a specific point referred to as a initiation pointa initiation point

•• The fracture surface is smooth in appearance The fracture surface is smooth in appearance sometimes displaying beach markingssometimes displaying beach markings

•• The final mode of failure may be brittle or ductile or a The final mode of failure may be brittle or ductile or a combination of bothcombination of both

Fatigue FractureFatigue Fracture 4.134.13

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• Toe grinding, profile grinding.

• The elimination of poor profiles

• The elimination of partial penetration welds and weld defects

• Operating conditions under the materials endurance limits

• The elimination of notch effects e.g. mechanical damage cap/root undercut

• The selection of the correct material for the service conditions of the component

Precautions against Fatigue Cracks

Fatigue FractureFatigue Fracture

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Fatigue fracture occurs in structures subject to repeated Fatigue fracture occurs in structures subject to repeated application of tensile stress. application of tensile stress.

Crack growth is slow (in same cases, crack may grow Crack growth is slow (in same cases, crack may grow into an area of low stress and stop without failure).into an area of low stress and stop without failure).


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Initiation points / weld defectsInitiation points / weld defects

Fatigue fracture surface Fatigue fracture surface

smooth in appearancesmooth in appearance

Secondary mode of failure Secondary mode of failure ductile fracture rough fibrous ductile fracture rough fibrous appearance appearance


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Crack growth is slowCrack growth is slow

It initiate from stress concentration pointsIt initiate from stress concentration points

load is considerably below the design or yield stress level load is considerably below the design or yield stress level

The surface is smoothThe surface is smooth

The surface is bounded by a curveThe surface is bounded by a curve

Bands may sometimes be seen on the smooth surface Bands may sometimes be seen on the smooth surface ––””beachmarksbeachmarks””. They show the progress of the crack front from the . They show the progress of the crack front from the point of originpoint of origin

The surface is 90The surface is 90°° to the loadto the load

Final fracture will usually take the form of gross yielding (as Final fracture will usually take the form of gross yielding (as the the maximum stress in the remaining ligament increase!)maximum stress in the remaining ligament increase!)

Fatigue crack need initiation + propagation periodsFatigue crack need initiation + propagation periods

Fatigue FractureFatigue FractureFatigue fracture distinguish features:Fatigue fracture distinguish features:

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Object of test:Object of test:

•• To determine the soundness of the weld zone. Bend To determine the soundness of the weld zone. Bend testing can also be used to give an assessment of testing can also be used to give an assessment of weld zone ductility.weld zone ductility.

•• There are three ways to perform a bend test:There are three ways to perform a bend test:

Root bendRoot bend

Face bendFace bend

Side bendSide bendSide bend tests are normally carried out on welds over 12mm in tSide bend tests are normally carried out on welds over 12mm in thicknesshickness

Bend Tests Bend Tests 4.154.15

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Bending testBending test 4.164.16

Types of bend test for welds (acc. BS EN 910):Types of bend test for welds (acc. BS EN 910):

Thickness of material Thickness of material -- ““tt””

““tt”” up to 12 mmup to 12 mm

““tt”” over 12 mmover 12 mm

Root / face Root / face bendbend

Side bendSide bend

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Fillet Weld Fracture Tests Fillet Weld Fracture Tests 4.174.17

Object of test:Object of test:To break open the joint through the weld to permit To break open the joint through the weld to permit examination of the fracture surfacesexamination of the fracture surfaces

Specimens are cut to the required lengthSpecimens are cut to the required length

A saw cut approximately 2mm in depth is applied A saw cut approximately 2mm in depth is applied along the fillet welds lengthalong the fillet welds length

Fracture is usually made by striking the specimen Fracture is usually made by striking the specimen with a single hammer blowwith a single hammer blow

Visual inspection for defectsVisual inspection for defects

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Fracture should break weld saw cut to rootFracture should break weld saw cut to root

2mm 2mm NotchNotch

HammerHammer

Fillet Weld Fracture TestsFillet Weld Fracture Tests 4.174.17

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This fracture indicates This fracture indicates lack of fusion lack of fusion

This fracture has This fracture has occurred saw cut to rootoccurred saw cut to root

Fillet Weld Fracture Tests Fillet Weld Fracture Tests 4.174.17

Lack of PenetrationLack of Penetration

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NickNick--Break TestBreak Test 4.184.18

Object of test:Object of test:

To permit evaluation of any weld defects across To permit evaluation of any weld defects across the fracture surface of a butt weld.the fracture surface of a butt weld.

•• Specimens are cut transverse to the weldSpecimens are cut transverse to the weld

•• A saw cut approximately 2mm in depth is applied A saw cut approximately 2mm in depth is applied along the welds root and capalong the welds root and cap

•• Fracture is usually made by striking the specimen with Fracture is usually made by striking the specimen with a single hammer blowa single hammer blow

•• Visual inspection for defectsVisual inspection for defects

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Approximately 230 mmApproximately 230 mm

19 mm19 mm

2 mm2 mm

2 mm2 mm

Notch cut by hacksawNotch cut by hacksaw

Weld reinforcement Weld reinforcement may or may not be may or may not be removedremoved

NickNick--Break TestBreak Test 4.184.18

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Nick Break Test Nick Break Test 4.184.18

Inclusions on fracture Inclusions on fracture lineline

Lack of root penetration Lack of root penetration or fusionor fusion

Alternative nickAlternative nick--break test break test specimen, notch applied all specimen, notch applied all way around the specimen way around the specimen

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We test welds to establish minimum levels of mechanical properties, and soundness of the welded joint

We divide tests into Qualitative & Quantitative methods:

Qualitative: (Have no units/numbers)

For assessing joint quality

Macro tests

Bend tests

Fillet weld fracture tests

Butt Nick break tests

Quantitative: (Have units/numbers)

To measure mechanical properties

Hardness (VPN & BHN)

Toughness (Joules & ft.lbs)

Strength (N/mm2 & PSI, MPa)

Ductility / Elongation (E%)

Summary of Mechanical TestingSummary of Mechanical Testing 4.194.19

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WPS WPS –– Welder QualificationsWelder QualificationsSection 5Section 5

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Welding Procedure QualificationWelding Procedure Qualification 5.15.1

Question:Question:

What is the main reason for carrying out a Welding Procedure What is the main reason for carrying out a Welding Procedure Qualification Test ?Qualification Test ?

(What is the test trying to show ?)(What is the test trying to show ?)

Answer:Answer:

To show that the welded joint has the To show that the welded joint has the propertiesproperties** that satisfy that satisfy the design requirements (fit for purpose)the design requirements (fit for purpose)

* p* propertiesroperties

••mechanical properties are the main interest mechanical properties are the main interest -- always strengthalways strength but but toughness & hardness may be important for some applicationstoughness & hardness may be important for some applications

••test also demonstrates that the weld can be made without defectstest also demonstrates that the weld can be made without defects

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Welding ProceduresWelding Procedures 5.15.1

Producing a welding procedure involves: Producing a welding procedure involves:

Planning the tasksPlanning the tasks

Collecting the dataCollecting the data

Writing a procedure for use of for trialWriting a procedure for use of for trial

Making a test weldsMaking a test welds

Evaluating the resultsEvaluating the results

Approving the procedureApproving the procedure

Preparing the documentationPreparing the documentation

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In most codes reference is made to how the procedure are toIn most codes reference is made to how the procedure are tobe devised and whether approval of these procedures isbe devised and whether approval of these procedures isrequired.required.The approach used for procedure approval depends on theThe approach used for procedure approval depends on thecode:code:Example codes:Example codes:•• AWS D.1.1: Structural Steel Welding CodeAWS D.1.1: Structural Steel Welding Code•• BS 2633: Class 1 welding of Steel Pipe WorkBS 2633: Class 1 welding of Steel Pipe Work•• API 1104: Welding of PipelinesAPI 1104: Welding of Pipelines•• BS 4515: Welding of Pipelines over 7 BarBS 4515: Welding of Pipelines over 7 Bar

Other codes may not specifically deal with the requirement ofOther codes may not specifically deal with the requirement ofa procedure but may contain information that may be used ina procedure but may contain information that may be used inwriting a weld procedurewriting a weld procedure•• EN 1011Process of Arc Welding Steels EN 1011Process of Arc Welding Steels

Welding Procedures Welding Procedures 5.25.2

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The welding engineer writes The welding engineer writes qualified Welding Procedure Welding Procedure Specifications (WPS) for production weldingSpecifications (WPS) for production welding

Welding Procedure Qualification Welding Procedure Qualification 5.35.3

Production Production welding conditions must remain within the must remain within the range of qualification allowed by the WPQR

(according to EN ISO 15614)(according to EN ISO 15614)

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(according to EN Standards)(according to EN Standards)

welding conditionswelding conditions are called are called welding variableswelding variables

welding variables are classified by the EN ISO Standard as:welding variables are classified by the EN ISO Standard as:

••Essential variablesEssential variables

••NonNon--essential variablesessential variables

••Additional variablesAdditional variablesNote:Note: additional variables = ASME supplementary essential additional variables = ASME supplementary essential

The The range of qualificationrange of qualification for production welding is based on for production welding is based on the limits that the EN ISO Standard specifies for the limits that the EN ISO Standard specifies for essential essential variables*variables*

((** and when applicable and when applicable -- the additional variables)the additional variables)

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WELDING ESSENTIALWELDING ESSENTIAL VARIABLESVARIABLESQuestion: Question:

Why are some welding variables classified as Why are some welding variables classified as essential essential ??

Answer:Answer:

A variable, that if changed beyond certain limits (specified by A variable, that if changed beyond certain limits (specified by the Welding Standard) may have the Welding Standard) may have a significant effecta significant effect on theon thepropertiesproperties* of the joint* of the joint

* particularly joint strength and ductility* particularly joint strength and ductility

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SOME TYPICAL SOME TYPICAL ESSENTIALESSENTIAL VARIABLESVARIABLES

•• Welding ProcessWelding Process•• Post Weld Heat Treatment (PWHT)Post Weld Heat Treatment (PWHT)•• Material TypeMaterial Type•• Electrode Type, Filler Wire Type (Classification)Electrode Type, Filler Wire Type (Classification)•• Material ThicknessMaterial Thickness•• Polarity (AC, DC+ve / DCPolarity (AC, DC+ve / DC--ve)ve)•• PrePre--Heat TemperatureHeat Temperature•• Heat InputHeat Input•• Welding PositionWelding Position

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Components of a welding procedureComponents of a welding procedureParent materialParent material

Type (Grouping)Type (Grouping)ThicknessThicknessDiameter (Pipes)Diameter (Pipes)Surface condition)Surface condition)

Welding processWelding processType of process (MMA, MAG, TIG, SAW etc)Type of process (MMA, MAG, TIG, SAW etc)Equipment parametersEquipment parametersAmps, Volts, Travel speedAmps, Volts, Travel speed

Welding ConsumablesWelding ConsumablesType of consumable/diameter of consumableType of consumable/diameter of consumableBrand/classificationBrand/classificationHeat treatments/ storageHeat treatments/ storage

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Components of a welding procedure Components of a welding procedure Joint designJoint design

Edge preparationEdge preparationRoot gap, root faceRoot gap, root faceJigging and tackingJigging and tackingType of bakingType of baking

Welding PositionWelding PositionLocation, shop or siteLocation, shop or siteWelding position e.g. 1G, 2G, 3G etcWelding position e.g. 1G, 2G, 3G etcAny weather precautionAny weather precaution

Thermal heat treatmentsThermal heat treatmentsPreheat, tempsPreheat, tempsPost weld heat treatments e.g. stress relieving Post weld heat treatments e.g. stress relieving

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Object of a welding procedure testObject of a welding procedure test

To give maximum confidence that the welds mechanical To give maximum confidence that the welds mechanical and metallurgical properties meet the requirements of the and metallurgical properties meet the requirements of the applicable code/specification.applicable code/specification.

Each welding procedure will show a range to which the Each welding procedure will show a range to which the procedure is approved (extent of approval)procedure is approved (extent of approval)

If a customer queries the approval evidence can be If a customer queries the approval evidence can be supplied to prove its validitysupplied to prove its validity


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Summary of designations:Summary of designations:

pWPS:pWPS: Preliminary Welding Procedure SpecificationPreliminary Welding Procedure Specification

(Before procedure approval)(Before procedure approval)

WPAR (WPQR):WPAR (WPQR): Welding Procedure Approval RecordWelding Procedure Approval Record

(Welding procedure Qualification record)(Welding procedure Qualification record)

WPS:WPS: Welding Procedure SpecificationWelding Procedure Specification

(After procedure approval)(After procedure approval)

Welding ProceduresWelding Procedures

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Example: Example: Welding Welding

Procedure Procedure Specification Specification

(WPS)(WPS)

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Numerous codes and standards deal with welder qualification, Numerous codes and standards deal with welder qualification, e.g. BS EN 287.e.g. BS EN 287.

•• Once the content of the procedure is approved the next Once the content of the procedure is approved the next stage is to approve the welders to the approved procedure. stage is to approve the welders to the approved procedure.

•• A welders test know as a A welders test know as a Welders Qualification Test (WQT).Welders Qualification Test (WQT).

Object of a welding qualification test:Object of a welding qualification test:

•• To give maximum confidence that the welder meets the To give maximum confidence that the welder meets the quality requirements of the approved procedure (WPS).quality requirements of the approved procedure (WPS).

•• The test weld should be carried out on the same material and The test weld should be carried out on the same material and same conditions as for the production welds.same conditions as for the production welds.

Welder QualificationWelder Qualification 5.45.4

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Welder Qualification Welder Qualification 5.4 & 5.55.4 & 5.5


Question:Question:

What is the main reason for qualifying a welder ?What is the main reason for qualifying a welder ?

Answer:Answer:

To show that he has the skill to be able to make production To show that he has the skill to be able to make production welds that are free from defectswelds that are free from defects

Note:Note: when welding in accordance with a Qualified WPSwhen welding in accordance with a Qualified WPS

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The welder is allowed to make production welds within the The welder is allowed to make production welds within the range of qualification shown on the Certificaterange of qualification shown on the Certificate

The The range of qualification allowed for production welding is range of qualification allowed for production welding is based on the limits that the EN Standard specifies for the based on the limits that the EN Standard specifies for the welder qualification essential variables

Welder Qualification Welder Qualification 5.55.5(according to EN 287 )(according to EN 287 )

A Certificate may be withdrawn by the Employer if there is A Certificate may be withdrawn by the Employer if there is reason to doubt the ability of the welder, for examplereason to doubt the ability of the welder, for example

•• a high repair ratea high repair rate•• not working in accordance with a qualified WPSnot working in accordance with a qualified WPS

The qualification shall remain valid for 2 years provided there The qualification shall remain valid for 2 years provided there is certified is certified confirmation of welding to the WPS in that time.confirmation of welding to the WPS in that time.A WelderA Welder’’s Qualification Certificate automatically expires if the welder s Qualification Certificate automatically expires if the welder has not has not used the welding process for 6 months or longer.used the welding process for 6 months or longer.

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Welding Engineer writes a Welding Engineer writes a preliminary Welding Procedure Welding Procedure Specification (Specification (ppWPS) for each test weld to be madeWPS) for each test weld to be made

•• A welder makes a test weld in accordance with the A welder makes a test weld in accordance with the ppWPSWPS

•• A welding inspector records all the welding conditions used A welding inspector records all the welding conditions used for the test weld (referred to as the for the test weld (referred to as the ‘‘asas--runrun’’ conditions)conditions)

An Independent Examiner/ Examining Body/ Third Party An Independent Examiner/ Examining Body/ Third Party inspector inspector maymay bebe requested to monitor the qualification requested to monitor the qualification processprocess



The finished test weld is subjected to NDT in accordance with The finished test weld is subjected to NDT in accordance with the methods specified by the EN ISO Standard the methods specified by the EN ISO Standard -- Visual, MT or Visual, MT or

PT & RT or UTPT & RT or UT

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Welding Procedure Qualification Welding Procedure Qualification 5.75.7

Test weld is subjected to destructive testing (tensile, bend, Test weld is subjected to destructive testing (tensile, bend, macro)macro)The Application Standard, or Client, may require additional The Application Standard, or Client, may require additional tests such as impact tests, hardness tests (and for some tests such as impact tests, hardness tests (and for some materials materials -- corrosion tests)corrosion tests)


A A Welding Procedure Qualification Record (WPQR) is prepared is prepared giving details of: giving details of: --

•• The welding conditions used for the test weldThe welding conditions used for the test weld•• Results of the NDTResults of the NDT•• Results of the destructive testsResults of the destructive tests•• The welding conditions that the test weld allows for The welding conditions that the test weld allows for

production weldingproduction weldingThe The Third Party may be requested to sign the WPQR as a true may be requested to sign the WPQR as a true recordrecord

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(according to EN 287 )(according to EN 287 )

An approved WPS should be available covering the range of An approved WPS should be available covering the range of qualification required for the welder approval.qualification required for the welder approval.

• The welder qualifies in accordance with an approved WPSThe welder qualifies in accordance with an approved WPS

•• A welding inspector monitors the welding to make sure that A welding inspector monitors the welding to make sure that the welder uses the conditions specified by the WPSthe welder uses the conditions specified by the WPS

EN Welding Standard states that an Independent Examiner, EN Welding Standard states that an Independent Examiner, Examining Body or Third Party Inspector Examining Body or Third Party Inspector maymay bebe required to required to monitor the qualification processmonitor the qualification process

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The finished test weld is subjected to NDT by the methods The finished test weld is subjected to NDT by the methods specified by the EN Standard specified by the EN Standard -- Visual, MT or PT & RT or UTVisual, MT or PT & RT or UTThe test weld may need to be destructively tested - for certain materials and/or welding processes specified by the EN Standard or the Client Specification


(according to EN 287 )(according to EN 287 )

•• A WelderA Welder’’s Qualification Certificate is prepared showing the s Qualification Certificate is prepared showing the conditions used for the test weld and the range of qualificationconditions used for the test weld and the range of qualificationallowed by the EN Standard for production weldingallowed by the EN Standard for production welding

•• The Qualification Certificate is usually endorsed by a Third The Qualification Certificate is usually endorsed by a Third Party Inspector as a true record of the testParty Inspector as a true record of the test

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Information that should be included on a welders test certificatInformation that should be included on a welders test certificate are, e are, which the welder should have or have access to a copy of !which the welder should have or have access to a copy of !

• Welders name and identification number• Date of test and expiry date of certificate• Standard/code e.g. BS EN 287• Test piece details• Welding process.• Welding parameters, amps, volts• Consumables, flux type and filler classification details• Sketch of run sequence • Welding positions• Joint configuration details• Material type qualified, pipe diameter etc• Test results, remarks• Test location and witnessed by• Extent (range) of approval


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Materials InspectionMaterials InspectionSection 6Section 6

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Material InspectionMaterial InspectionOne of the most important items to consider is TraceabilityOne of the most important items to consider is Traceability..

The materials are of little use if we can not, by use of an The materials are of little use if we can not, by use of an effective QA system trace them from specification and effective QA system trace them from specification and purchase order to final documentation package handed over to purchase order to final documentation package handed over to the Client.the Client.

All materials arriving on site should be inspected for:All materials arriving on site should be inspected for:

Size / dimensionsSize / dimensions

ConditionCondition

Type / specificationType / specification

In addition other elements may need to be considered In addition other elements may need to be considered depending on the materials form or shapedepending on the materials form or shape

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We inspect the condition(Corrosion, Damage, Wall thickness Ovality, Laminations & Seam)

Specification

Welded seam

Size

LP5

Pipe InspectionPipe Inspection

Other checks may need to be made such as: distortion tolerance, number of plates and storage.

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Size

We inspect the condition

(Corrosion, Mechanical damage, Laps, Bands & Laminations)

5L

Specification

Other checks may need to be made such as: distortion tolerance, number of plates and storage.

Plate InspectionPlate InspectionPlate Inspection

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Parent Material ImperfectionsParent Material Imperfections

LaminationLamination

Mechanical damageMechanical damage LapLap

Segregation lineSegregation lineLaminationsLaminations are caused in the parent plate by the steel making are caused in the parent plate by the steel making process, originating from ingot casting defects.process, originating from ingot casting defects.

Segregation bandsSegregation bands occur in the centre of the plate and are low occur in the centre of the plate and are low melting point impurities such as sulphur and phosphorous.melting point impurities such as sulphur and phosphorous.

LapsLaps are caused during rolling when overlapping metal does not are caused during rolling when overlapping metal does not fuse to the base material.fuse to the base material.

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LappingLappingLapping

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LaminationLaminationLamination

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LaminationsLaminations

Plate LaminationPlate Lamination

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Codes & StandardsCodes & StandardsSection 7Section 7

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Codes & StandardsCodes & StandardsThe 3 agencies generally identified in a code or standard:

The customer, or client

The manufacturer, or contractor

The 3rd party inspection, or clients representative

Codes often do not contain all relevant data, but may refer to other standards

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Standard/Codes/SpecificationsStandard/Codes/Specifications

STANDARDSSTANDARDS

SPECIFICATIONSSPECIFICATIONS CODESCODES

ExamplesExamples

plate, pipe plate, pipe

forgings, castingsforgings, castings

valvesvalves

electrodeselectrodes

ExamplesExamples

pressure vesselspressure vessels

bridgesbridges

pipelinespipelines

tankstanks

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Welding SymbolsWelding SymbolsSection 8Section 8

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Advantages of symbolic representation:Advantages of symbolic representation:simple and quick plotting on the drawingsimple and quick plotting on the drawing

does not overdoes not over--burden the drawingburden the drawing

no need for additional viewno need for additional view

gives all necessary indications regarding the specific gives all necessary indications regarding the specific joint to be obtainedjoint to be obtained

Disadvantages of symbolic representation:Disadvantages of symbolic representation:used only for usual jointsused only for usual joints

requires training for properly understanding of symbolsrequires training for properly understanding of symbols

Weld symbols on drawingsWeld symbols on drawings

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The symbolic representation includes: The symbolic representation includes:

an arrow linean arrow line

a reference linea reference line

an elementary symbol an elementary symbol

The elementary symbol may be completed by:The elementary symbol may be completed by:

a supplementary symbola supplementary symbol

a means of showing dimensionsa means of showing dimensions

some complementary indicationssome complementary indications


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In most standards the cross sectional dimensions are given to In most standards the cross sectional dimensions are given to the left side of the symbol, and all linear dimensions are give the left side of the symbol, and all linear dimensions are give on on the right sidethe right side

DimensionsDimensionsConvention of dimensions Convention of dimensions

a = Design throat thicknesss = Depth of Penetration, Throat thicknessz = Leg length (min material thickness)

BS EN ISO 22553BS EN ISO 22553

AWS A2.4AWS A2.4•In a fillet weld, the size of the weld is the leg length•In a butt weld, the size of the weld is based on the depth of the joint preparation

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A method of transferring information from the A method of transferring information from the design office to the workshop is:design office to the workshop is:

The above information does not tell us much about the wishes The above information does not tell us much about the wishes of the designer. We obviously need some sort of code which of the designer. We obviously need some sort of code which would be understood by everyone.would be understood by everyone.

Most countries have their own standards for symbols. Most countries have their own standards for symbols. Some of them are AWS A2.4 & BS EN 22553 (ISO 2553)Some of them are AWS A2.4 & BS EN 22553 (ISO 2553)

Please weld Please weld here here


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Joints in drawings may be indicated:Joints in drawings may be indicated:

••by detailed sketches, showing every dimensionby detailed sketches, showing every dimension

••by symbolic representationby symbolic representation

Weld symbols on drawings

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Elementary Welding SymbolsElementary Welding Symbols(BS EN ISO 22553 & AWS A2.4)(BS EN ISO 22553 & AWS A2.4)

Convention of the elementary symbols: Convention of the elementary symbols: Various categories of joints are characterised by an elementary symbol.

The vertical line in the symbols for a fillet weld, single/double bevel butts and a J-butt welds must always be on the left side.

Square edgeSquare edgebutt weldbutt weld

Weld typeWeld type SketchSketch SymbolSymbol

SingleSingle--vvbutt weldbutt weld

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Elementary Welding SymbolsElementary Welding Symbols

SingleSingle--V butt V butt weld with broad weld with broad

root faceroot face


Single Single bevel butt bevel butt

weldweldSingle bevel Single bevel

butt weld with butt weld with broad root broad root

facefaceBacking runBacking run

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Elementary Welding SymbolsElementary Welding Symbols

SingleSingle--UUbutt weld butt weld


SingleSingle--JJbutt weldbutt weld

Fillet weldFillet weld

SurfacingSurfacing

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Plug weld

Resistance spot weld

Resistance seam weld

Square Butt weld

Steep flanked Single-V Butt

Surfacing

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553

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Arrow LineArrow Line(BS EN ISO 22553 & AWS A2.4):(BS EN ISO 22553 & AWS A2.4):

Convention of the arrow line:Convention of the arrow line:

•• ShallShall touch the joint intersectiontouch the joint intersection

•• ShallShall not be parallel to the drawingnot be parallel to the drawing

•• ShallShall point towards a single plate preparation (when only point towards a single plate preparation (when only one plate has preparation)one plate has preparation)

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(AWS A2.4)(AWS A2.4)

Convention of the reference line: Convention of the reference line:

ShallShall touch the arrow linetouch the arrow line

ShallShall be parallel to the bottom of the drawingbe parallel to the bottom of the drawing

Reference LineReference Line

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oror

Reference LineReference Line

(BS EN ISO 22553)(BS EN ISO 22553)

Convention of the reference line: Convention of the reference line:

•• ShallShall touch the arrow linetouch the arrow line

•• ShallShall be parallel to the bottom of the drawingbe parallel to the bottom of the drawing

•• There shallThere shall be a further broken identification line above or be a further broken identification line above or beneath the reference line (Not necessary where the weld beneath the reference line (Not necessary where the weld is symmetrical!)is symmetrical!)

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(BS EN ISO 22553 & AWS A2.4)(BS EN ISO 22553 & AWS A2.4)

Convention of the double side weld symbols:Convention of the double side weld symbols:

Representation of welds done from Representation of welds done from both sidesboth sides of the joint of the joint intersection, touched by the arrow headintersection, touched by the arrow head

Fillet weldFillet weld

Double VDouble V

Double bevelDouble bevel

Double UDouble U

Double JDouble J

Double side weld symbolsDouble side weld symbols

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Arrow lineArrow line

Reference linesReference lines

Arrow sideArrow side

Other sideOther side Arrow sideArrow side

Other sideOther side

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553

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SingleSingle--V Butt flush capV Butt flush cap SingleSingle--U Butt with sealing runU Butt with sealing run

SingleSingle--V Butt with V Butt with permanent backing strippermanent backing strip

M M

SingleSingle--U Butt with U Butt with removable backing stripremovable backing strip

M RM R

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553

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SingleSingle--bevel buttbevel butt DoubleDouble--bevel buttbevel butt

SingleSingle--bevel butt bevel butt SingleSingle--J buttJ butt

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553

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Partial penetration singlePartial penetration single--V buttV butt‘‘SS’’ indicates the depth of penetrationindicates the depth of penetration

s10s10

10101515

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553

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aa = Design throat thickness= Design throat thicknessss = Depth of Penetration, Throat = Depth of Penetration, Throat

thicknessthicknessz z = Leg length(min material thickness)= Leg length(min material thickness)a a = (0.7 x z)= (0.7 x z)

a 4a 4

4mm Design throat 4mm Design throat

z 6z 6

6mm leg6mm leg

az s

s 6s 6

6mm Actual throat 6mm Actual throat

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553

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ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553



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ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553


s6

s6

6mm fillet weld

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n n = number of weld elements= number of weld elementsl l = length of each weld element= length of each weld element((ee)) = distance between each weld element= distance between each weld element

nn x x l l ((ee))

Welds to be Welds to be staggeredstaggered

ProcessProcess

2 x 402 x 40 (50)(50)3 x 403 x 40 (50)(50)

111111

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553

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80 80 80

909090

6

6

5

5

z5z5

z6z6

3 x 80 (90)3 x 80 (90)

3 x 80 (90)3 x 80 (90)

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553

All dimensions in mmAll dimensions in mm

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ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553

All dimensions in mmAll dimensions in mm

8

8

6

680 80 80

909090

z8z8

z6z6

3 x 80 (90)3 x 80 (90)

3 x 80 (90)3 x 80 (90)

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Supplementary symbolsSupplementary symbols

Concave or ConvexConcave or Convex

Toes to be ground smoothly Toes to be ground smoothly (BS EN only)(BS EN only)

Site WeldSite Weld

Weld all roundWeld all round


Convention of supplementary symbolsConvention of supplementary symbols

Supplementary information Supplementary information such as welding process, weld profile, NDT and any special instructions

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Supplementary symbolsSupplementary symbols

Further supplementary information, such as WPS number, or Further supplementary information, such as WPS number, or NDT may be placed in the fish tailNDT may be placed in the fish tail

Ground flushGround flush

111111

Welding process Welding process numerical BS EN numerical BS EN

MRMR

Removable Removable backing strip backing strip

Permanent Permanent backing strip backing strip

MM


Convention of supplementary symbolsConvention of supplementary symbols

Supplementary information Supplementary information such as welding process, weld profile, NDT and any special instructions

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bbaa

ddcc

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553

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ConvexConvexMitreMitre

Toes Toes shall be shall be blendedblended

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553

ConcaveConcave

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aa = Design throat thickness= Design throat thicknessss = Depth of Penetration, Throat = Depth of Penetration, Throat

thicknessthicknessz z = Leg length(min material thickness)= Leg length(min material thickness)a a = (0.7 x z)= (0.7 x z)

a 4a 4

4mm Design throat 4mm Design throat

z 6z 6

6mm leg6mm leg

az s

s 6s 6

6mm Actual throat 6mm Actual throat

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553

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Field weld (site weld)Field weld (site weld)

The component requires The component requires NDT inspectionNDT inspection

WPSWPS

Additional information, Additional information, the reference document the reference document

is included in the boxis included in the box

Welding to be carried out Welding to be carried out all round component all round component

(peripheral weld)(peripheral weld)

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553Complimentary SymbolsComplimentary Symbols

NDTNDT

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Numerical Values for Welding Processes:Numerical Values for Welding Processes:

111:111: MMA welding with covered electrodeMMA welding with covered electrode

121:121: SubSub--arc welding with wire electrodearc welding with wire electrode

131: 131: MIG welding with inert gas shieldMIG welding with inert gas shield

135:135: MAG welding with nonMAG welding with non--inert gas shieldinert gas shield

136:136: Flux core arc weldingFlux core arc welding

141:141: TIG weldingTIG welding

311:311: OxyOxy--acetylene weldingacetylene welding

72:72: ElectroElectro--slag weldingslag welding

15: 15: Plasma arc weldingPlasma arc welding

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553

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AWS A2.4 Welding SymbolsAWS A2.4 Welding Symbols

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11(1(1--1/8)1/8)

6060oo1/81/8

Depth of Depth of BevelBevel

Effective Effective Throat Throat

Root OpeningRoot Opening

Groove AngleGroove Angle

AWS Welding SymbolsAWS Welding Symbols

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1(11(1--1/8)1/8)

6060oo1/81/8

GSFCAWGSFCAW

Welding Process Welding Process

GMAWGMAW

GTAWGTAW

SAWSAW


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3 3 –– 10103 3 –– 1010

Welds to be Welds to be staggeredstaggered

SMAWSMAW

ProcessProcess

1010

33 33


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1(1-1/8) 1/860o

FCAW

Sequence of Operations

1st Operation

2nd Operation

3rd Operation


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1(1-1/8) 1/860o

FCAW

Sequence of Operations

RT

MTMT


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Dimensions- Leg Length

6/86 leg on member A

8

6Member A

Member B


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Intro To Welding ProcessesIntro To Welding ProcessesSection 9Section 9

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Welding is regarded as a joining process in which the work Welding is regarded as a joining process in which the work pieces are in atomic contactpieces are in atomic contact

Pressure weldingPressure welding•• Forge weldingForge welding•• Friction weldingFriction welding•• Resistance WeldingResistance Welding

Fusion weldingFusion welding•• OxyOxy--acetyleneacetylene•• MMA (SMAW)MMA (SMAW)•• MIG/MAG (GMAW)MIG/MAG (GMAW)•• TIG (GTAW)TIG (GTAW)•• SubSub--arc (SAW)arc (SAW)•• ElectroElectro--slag (ESW)slag (ESW)•• Laser Beam (LBW)Laser Beam (LBW)•• ElectronElectron--Beam (EBW)Beam (EBW)

Welding ProcessesWelding Processes

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2020 80804040 6060 130130 140140120120100100 180180160160 200200

1010

6060

5050

4040

3030

2020

8080

7070

9090

100100

Normal Operating Normal Operating Voltage RangeVoltage Range

Large voltage variation, e.g. Large voltage variation, e.g. + + 10v (due to changes in arc 10v (due to changes in arc length) length) Small amperage change Small amperage change resulting in virtually constant resulting in virtually constant current e.g. current e.g. ++ 5A. 5A.

Volta

geVo

ltage

AmperageAmperage

Required for: MMA, TIG, Plasma Required for: MMA, TIG, Plasma arc and SAW > 1000 AMPSarc and SAW > 1000 AMPS

O.C.V. Striking voltage (typical) for O.C.V. Striking voltage (typical) for arc initiationarc initiation

Constant Current Power SourceConstant Current Power Source(Drooping Characteristic)(Drooping Characteristic)

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Monitoring Heat InputMonitoring Heat Input

Heat Input:Heat Input:The amount of heat generated in theThe amount of heat generated in thewelding arc per unit length of weld.welding arc per unit length of weld.Expressed in kilo Joules per millimetre Expressed in kilo Joules per millimetre length of weld (kJ/mm).length of weld (kJ/mm).

Heat Input (kJ/mm)= Heat Input (kJ/mm)= Volts x AmpsVolts x AmpsTravel speed(mm/s) x 1000Travel speed(mm/s) x 1000

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Weld and weld pool temperatures

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Monitoring Heat Input As Required byMonitoring Heat Input As Required byBS EN ISO 15614BS EN ISO 15614--1:20041:2004In accordance with EN 1011In accordance with EN 1011--1:19981:1998

When impact requirements and/or hardness requirements are specified, impact test shall be taken from the weld in the highest heat input position and hardness tests shall be taken from the weld in the lowest heat input position in order to qualify for all positions

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MMA WeldingMMA WeldingSection 10Section 10

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MMA MMA -- Principle of operationPrinciple of operation

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MMA weldingMMA welding

Main features: Main features: Shielding provided by decomposition of flux coveringShielding provided by decomposition of flux coveringElectrode consumableElectrode consumableManual processManual process

Welder controls:Welder controls:Arc lengthArc lengthAngle of electrodeAngle of electrodeSpeed of travelSpeed of travelAmperage settingsAmperage settings

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Power sourcePower source

Holding ovenHolding oven

Inverter power Inverter power sourcesource

Electrode holderElectrode holder

Power cablesPower cablesWelding visor Welding visor filter glassfilter glass

Return leadReturn lead

ElectrodesElectrodes

Electrode Electrode ovenoven

Control panel Control panel (amps, volts)(amps, volts)

Manual Metal Arc Basic EquipmentManual Metal Arc Basic Equipment

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Transformer:Transformer:•• Changes mains supply voltage to a voltage suitable for welding. Changes mains supply voltage to a voltage suitable for welding.

Has no moving parts and is often termed static plant.Has no moving parts and is often termed static plant.Rectifier:Rectifier:•• Changes a.c. to d.c., can be mechanically or statically achievedChanges a.c. to d.c., can be mechanically or statically achieved..Generator:Generator:•• Produces welding current. The generator consists of an armature Produces welding current. The generator consists of an armature

rotating in a magnetic field, the armature must be rotated at a rotating in a magnetic field, the armature must be rotated at a constant speed either by a motor unit or, in the absence of constant speed either by a motor unit or, in the absence of electrical power, by an internal combustion engine.electrical power, by an internal combustion engine.

Inverter:Inverter:•• An inverter changes d.c. to a.c. at a higher frequency.An inverter changes d.c. to a.c. at a higher frequency.

MMA Welding PlantMMA Welding Plant

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VoltageVoltage•• The arc voltage in the MMA process is measured as close to The arc voltage in the MMA process is measured as close to

the arc as possible. It is variable with a change in arc lengththe arc as possible. It is variable with a change in arc length

O.C.V.O.C.V.•• The open circuit voltage is the voltage required to initiate, orThe open circuit voltage is the voltage required to initiate, or

rere--ignite the electrical arc and will change with the type of ignite the electrical arc and will change with the type of electrode being used e.g 70electrode being used e.g 70--90 volts90 volts

CurrentCurrent•• The current used will be determined by the choice of The current used will be determined by the choice of

electrode, electrode diameter and material type and electrode, electrode diameter and material type and thickness. Current has the most effect on penetration.thickness. Current has the most effect on penetration.

PolarityPolarity•• Polarity is generally determined by operation and electrode Polarity is generally determined by operation and electrode

type e.g DC +type e.g DC +veve, DC , DC ––veve or ACor AC

MMA Welding VariablesMMA Welding Variables

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2020 80804040 6060 130130 140140120120100100 180180160160 200200

1010

6060

5050

4040

3030

2020

8080

7070

9090

100100

Normal Operating Normal Operating Voltage RangeVoltage Range

Large voltage variation, e.g. Large voltage variation, e.g. + + 10v (due to changes in arc 10v (due to changes in arc length) length) Small amperage change Small amperage change resulting in virtually constant resulting in virtually constant current e.g. current e.g. ++ 5A. 5A.

Volta

geVo

ltage

AmperageAmperage

O.C.V. Striking voltage (typical) for arc O.C.V. Striking voltage (typical) for arc initiationinitiation

Constant Current Power SourceConstant Current Power Source(Drooping Characteristic)(Drooping Characteristic)

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MMA welding parametersMMA welding parametersTravel speedTravel speed

Travel Travel speedspeed Too highToo highToo lowToo low

••wide weld bead contourwide weld bead contour••lack of penetrationlack of penetration••burnburn--throughthrough

••lack of root fusionlack of root fusion••incomplete root incomplete root penetrationpenetration••undercutundercut••poor bead profile, poor bead profile, difficult slag removaldifficult slag removal

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MMA welding parametersMMA welding parametersType of current:Type of current:

voltage drop in welding cables is lower with ACvoltage drop in welding cables is lower with ACinductive looses can appear with AC if cables are coiledinductive looses can appear with AC if cables are coiledcheaper power source for ACcheaper power source for ACno problems with arc blow with ACno problems with arc blow with ACDC provides a more stable and easy to strike arc, DC provides a more stable and easy to strike arc, especially with low current,especially with low current, better positional weld, thin better positional weld, thin sheet applicationssheet applicationswelding with a short arc length (low arc voltage) is easier welding with a short arc length (low arc voltage) is easier with DC,with DC, better mechanical propertiesbetter mechanical propertiesDC provides a smoother metal transfer, less spatterDC provides a smoother metal transfer, less spatter

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MMA welding parametersMMA welding parametersWelding currentWelding current

–– approx. 35 A/mm of diameterapprox. 35 A/mm of diameter–– governed by thickness, type of joint and welding governed by thickness, type of joint and welding

position position

Welding Welding currentcurrent Too highToo highToo lowToo low

••poor startingpoor starting••slag inclusionsslag inclusions••weld bead contour too weld bead contour too highhigh••lack of lack of fusion/penetrationfusion/penetration

••spatterspatter••excess excess penetrationpenetration••undercutundercut••burnburn--throughthrough

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MMA welding parametersMMA welding parametersArc length = arc voltageArc length = arc voltage

Arc Arc voltagevoltage Too highToo highToo lowToo low

••arc can be extinguishedarc can be extinguished••““stubbingstubbing””

••spatterspatter••porosityporosity••excess excess penetrationpenetration••undercutundercut••burnburn--throughthrough

Polarity: DCEP generally gives deeper penetrationPolarity: DCEP generally gives deeper penetration

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MMA MMA -- TroubleshootingTroubleshooting

MMA quality (left to right)MMA quality (left to right)current, arc length and travel speed normal;current, arc length and travel speed normal;

current too low; current too low; current too high;current too high;

arc length too short;arc length too short;arc length too long;arc length too long;

travel speed too slow;travel speed too slow;travel speed too hightravel speed too high

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MMA electrode holderMMA electrode holder

Collet or twist typeCollet or twist type ““TongsTongs”” type with type with springspring--loaded jawsloaded jaws

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The three main electrode covering types used in MMA weldingThe three main electrode covering types used in MMA welding

•• CellulosicCellulosic -- deep penetration/fusion deep penetration/fusion

•• RutileRutile -- general purposegeneral purpose

•• BasicBasic -- low hydrogenlow hydrogen

(Covered in more detail in Section 14)(Covered in more detail in Section 14)

MMA Welding ConsumablesMMA Welding Consumables

MMA Covered ElectrodesMMA Covered Electrodes

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Most welding defects in MMA are caused by a lack of welder Most welding defects in MMA are caused by a lack of welder skill (not an easily controlled process), the incorrect settingskill (not an easily controlled process), the incorrect settings s of the equipment, or the incorrect use, and treatment of of the equipment, or the incorrect use, and treatment of electrodeselectrodes

Typical Welding Defects:Typical Welding Defects:

••Slag inclusionsSlag inclusions

••Arc strikes Arc strikes

••PorosityPorosity

••UndercutUndercut

••Shape defects (overlap, excessive root penetration, etc.)Shape defects (overlap, excessive root penetration, etc.)

MMA welding typical defectsMMA welding typical defects

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Advantages:Advantages:•• Field or shop useField or shop use•• Range of consumablesRange of consumables•• All positionsAll positions•• PortablePortable•• Simple equipment Simple equipment Disadvantages:Disadvantages:•• High welder skill requiredHigh welder skill required•• High levels of fumeHigh levels of fume•• Hydrogen control (flux)Hydrogen control (flux)•• Stop/start problemsStop/start problems•• Comparatively uneconomic when compared with Comparatively uneconomic when compared with some some

other processes i.e MAG, SAW and FCAWother processes i.e MAG, SAW and FCAW

Manual Metal Arc Welding (MMA)Manual Metal Arc Welding (MMA)

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TIG WeldingTIG WeldingSection 11Section 11

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The TIG welding process was first developed in the USA The TIG welding process was first developed in the USA during the 2during the 2ndnd world war for the welding of aluminum alloysworld war for the welding of aluminum alloys

•• The process uses a nonThe process uses a non--consumable tungsten electrodeconsumable tungsten electrode

•• The process requires a high level of welder skillThe process requires a high level of welder skill

•• The process produces very high quality welds.The process produces very high quality welds.

•• The TIG process is considered as a slow process compared The TIG process is considered as a slow process compared to other arc welding processesto other arc welding processes

•• The arc may be initiated by a high frequency to The arc may be initiated by a high frequency to avoid scratch avoid scratch starting, which could cause starting, which could cause contamination of contamination of the tungsten the tungsten and weld and weld

Tungsten Inert Gas WeldingTungsten Inert Gas Welding

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TIG TIG -- Principle of operationPrinciple of operation

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VoltageVoltage

The voltage of the TIG welding process is variable only by the The voltage of the TIG welding process is variable only by the type of gas being used, and changes in the arc lengthtype of gas being used, and changes in the arc length

Current Current

The current is adjusted proportionally to the tungsten The current is adjusted proportionally to the tungsten electrodes diameter being used. The higher the current the electrodes diameter being used. The higher the current the deeper the penetration and fusiondeeper the penetration and fusion

PolarityPolarityThe polarity used for steels is always DC The polarity used for steels is always DC ––ve as most of the ve as most of the heat is concentrated at the +ve pole, this is required to keep heat is concentrated at the +ve pole, this is required to keep the tungsten electrode at the cool end of the arc. When the tungsten electrode at the cool end of the arc. When welding aluminium and its alloys AC current is usedwelding aluminium and its alloys AC current is used

TIG Welding VariablesTIG Welding Variables

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Types of currentTypes of currentcan be DCEN or DCEPcan be DCEN or DCEPDCEN gives deep penetrationDCEN gives deep penetration

requires special power sourcerequires special power sourcelow frequency low frequency -- up to 20 up to 20 pulses/sec (thermal pulsing)pulses/sec (thermal pulsing)better weld pool controlbetter weld pool controlweld pool partially solidifies weld pool partially solidifies between pulsesbetween pulses

Type of Type of welding welding currentcurrent

can be sine or square wavecan be sine or square waverequires a HF current (continuos requires a HF current (continuos or periodical)or periodical)provide cleaning actionprovide cleaning action

DCDC

ACAC

Pulsed Pulsed currentcurrent

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Choosing the proper electrodeChoosing the proper electrodeCurrent type influenceCurrent type influence

++++

++

++++

++

++++

++

----

--

----

--

----

--

Electrode capacityElectrode capacity

Current type & polarity

Heat balanceHeat balance

Oxide cleaning actionOxide cleaning actionPenetrationPenetration

DCENDCEN DCEPDCEPAC (balanced)AC (balanced)

70% at work30% at electrode30% at electrode



Deep, narrowDeep, narrow MediumMedium Shallow, wideShallow, wide

NoNo Yes Yes -- every half cycleevery half cycle YesYesExcellent Excellent

(e.g. 3,2 mm/400A)(e.g. 3,2 mm/400A)Good Good

(e.g. 3,2 mm/225A)(e.g. 3,2 mm/225A)Poor Poor

(e.g. 6,4 mm/120A)(e.g. 6,4 mm/120A)

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ARC CHARACTERISTICSARC CHARACTERISTICS

VoltsVolts

AmpsAmps

OCVOCV

Constant Current/Amperage CharacteristicConstant Current/Amperage Characteristic

Large change in voltage = Large change in voltage = Smaller change in amperageSmaller change in amperage

Welding VoltageWelding VoltageLarge arc gapLarge arc gap

Small arc Small arc gapgap

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TIG TIG -- arc initiation methodsarc initiation methods

simple methodsimple methodtungsten electrode is in contact tungsten electrode is in contact with the workpiece!with the workpiece!high initial arc current due to high initial arc current due to the short circuitthe short circuitimpractical to set arc length in impractical to set arc length in advanceadvanceelectrode should tap the electrode should tap the workpiece workpiece -- no scratch!no scratch!ineffective in case of ACineffective in case of ACused when a high quality is not used when a high quality is not essentialessential

Arc initiation Arc initiation methodmethod

Lift arcLift arc HF startHF startneed a HF generator (sparkneed a HF generator (spark--gap oscillator) that generates a gap oscillator) that generates a high voltage AC output (radio high voltage AC output (radio frequency) frequency) �� costlycostlyreliable method reliable method �� required on required on both DC (for start) and AC (to both DC (for start) and AC (to rere--ignite the arc)ignite the arc)can be used remotelycan be used remotelyHF produce interferenceHF produce interferencerequires superior insulationrequires superior insulation

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Pulsed currentPulsed currentusually peak current is 2usually peak current is 2--10 10 times background currenttimes background currentuseful on metals sensitive to useful on metals sensitive to high heat inputhigh heat inputreduced distortionsreduced distortionsin case of dissimilar thicknesses in case of dissimilar thicknesses equal penetration can be equal penetration can be achieved achieved

Time

Cur

rent

(A) Pulse

timeCycle time

Peak current

Background current

Average current

one set of variables can be used in all positionsone set of variables can be used in all positionsused for bridging gaps in open root jointsused for bridging gaps in open root jointsrequire special power sourcerequire special power source

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Choosing the proper electrodeChoosing the proper electrode

Polarity Influence Polarity Influence –– cathodic cleaning effectcathodic cleaning effect

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Old types: (Slightly Radioactive)Old types: (Slightly Radioactive)

•• Thoriated: DC electrode Thoriated: DC electrode --veve -- steels and most metalssteels and most metals

•• 1% thoriated + tungsten for higher current values1% thoriated + tungsten for higher current values

•• 2% thoriated for lower current values2% thoriated for lower current values

•• Zirconiated: AC Zirconiated: AC -- aluminum alloys and magnesiumaluminum alloys and magnesium

New types: (Not Radioactive)New types: (Not Radioactive)

•• Cerium: DC electrode Cerium: DC electrode --ve ve -- steels and most metalssteels and most metals

•• Lanthanum: AC Lanthanum: AC -- Aluminum alloys and magnesiumAluminum alloys and magnesium

Tungsten ElectrodesTungsten Electrodes

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TIG torch setTIG torch set--upup

Electrode extensionElectrode extension

Electrode Electrode extensionextension

StickoutStickout 22--3 times 3 times electrode electrode diameterdiameter


Low electron Low electron emission emission ��

Unstable arcUnstable arc

Too Too smallsmall

Overheating Overheating �� Tungsten Tungsten inclusionsinclusions

Too Too largelarge

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Choosing the correct electrodeChoosing the correct electrode

Polarity Influence Polarity Influence –– cathodic cleaning effectcathodic cleaning effect

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Old types: (Slightly Radioactive)Old types: (Slightly Radioactive)

•• Thoriated: DC electrode Thoriated: DC electrode --veve -- steels and most metalssteels and most metals

•• 1% thoriated + tungsten for higher current values1% thoriated + tungsten for higher current values

•• 2% thoriated for lower current values2% thoriated for lower current values

•• Zirconiated: AC Zirconiated: AC -- aluminum alloys and magnesiumaluminum alloys and magnesium

New types: (Not Radioactive)New types: (Not Radioactive)

•• Cerium: DC electrode Cerium: DC electrode --ve ve -- steels and most metalssteels and most metals

•• Lanthanum: AC Lanthanum: AC -- Aluminum alloys and magnesiumAluminum alloys and magnesium

Tungsten ElectrodesTungsten Electrodes

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Tungsten electrode typesTungsten electrode typesPure tungsten electrodes:Pure tungsten electrodes:

colour code colour code -- greengreen

no alloy additions no alloy additions

low current carrying capacitylow current carrying capacity

maintains a clean balled end maintains a clean balled end

can be used for AC welding of Al and Mg alloyscan be used for AC welding of Al and Mg alloys

poor arc initiation and arc stability with AC compared poor arc initiation and arc stability with AC compared with other electrode typeswith other electrode types

used on less critical applicationsused on less critical applications

low costlow cost

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Tungsten electrode typesTungsten electrode types

Thoriated tungsten electrodes:Thoriated tungsten electrodes:

colour code colour code -- yellowyellow//redred//violetviolet

20% higher current carrying capacity compared to 20% higher current carrying capacity compared to pure tungsten electrodespure tungsten electrodes

longer life longer life -- greater resistance to contaminationgreater resistance to contamination

thermionic thermionic -- easy arc initiation, more stable arceasy arc initiation, more stable arc

maintain a sharpened tipmaintain a sharpened tip

recommended for DCEN, seldom used on AC recommended for DCEN, seldom used on AC (difficult to maintain a balled tip)(difficult to maintain a balled tip)

This slightly radioactiveThis slightly radioactive

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Tungsten electrode typesTungsten electrode types

CeriatedCeriated tungsten electrodes:tungsten electrodes:

colour code colour code -- grey (orange acc. AWS Agrey (orange acc. AWS A--5.12)5.12)

operate successfully with AC or DCoperate successfully with AC or DC

Ce not radioactive Ce not radioactive -- replacement for thoriated typesreplacement for thoriated types

LanthaniatedLanthaniated tungsten electrodes:tungsten electrodes:

colour code colour code -- black//goldgold//blueblue

operating characteristics similar with ceriated operating characteristics similar with ceriated electrodeelectrode

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Tungsten electrode typesTungsten electrode typesZirconiated tungsten electrodes:Zirconiated tungsten electrodes:

colour code colour code -- brownbrown//white

operating characteristics fall between those of pure operating characteristics fall between those of pure and thoriated electrodesand thoriated electrodes

retains a balled end during welding retains a balled end during welding -- good for AC good for AC weldingwelding

high resistance to contaminationhigh resistance to contamination

preferred for radiographic quality weldspreferred for radiographic quality welds

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Electrode tip for DCENElectrode tip for DCEN

Electrode tip prepared for low Electrode tip prepared for low current weldingcurrent welding

Electrode tip prepared for high Electrode tip prepared for high current weldingcurrent welding

Vertex Vertex angleangle

Penetration Penetration increaseincrease

IncreaseIncrease

Bead width Bead width increaseincrease

DecreaseDecrease

22 --2,

5 tim

es

2,5

times

el

ectr

ode

diam

eter

elec

trod

e di

amet

er

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Electrode tip for ACElectrode tip for AC

Electrode tip groundElectrode tip ground Electrode tip ground and Electrode tip ground and then conditionedthen conditioned

ACDC -ve

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Tungsten electrodesTungsten electrodesThe electrode diameter, type and vertex angle are all critical The electrode diameter, type and vertex angle are all critical factors considered as essential variables. The vertex angle is factors considered as essential variables. The vertex angle is as shownas shown

Vetex angleVetex angleNote: Note: when welding when welding aluminium with AC aluminium with AC current, the tungsten end current, the tungsten end is chamfered and forms a is chamfered and forms a ball end when weldingball end when welding

DC DC --veve

Note: Note: too fine an angle will too fine an angle will promote melting of the promote melting of the electrodes tipelectrodes tip

ACAC

TIG Welding VariablesTIG Welding Variables

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Choosing the proper electrodeChoosing the proper electrode

Unstable Unstable arcarc

Tungsten Tungsten inclusionsinclusions

Welding Welding currentcurrent

Electrode tip Electrode tip not properly not properly

heatedheated

Excessive Excessive melting or melting or

volatilisationvolatilisation

Too Too lowlow

Too Too highhigh

Factors to be considered:Factors to be considered:

PenetrationPenetration

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Shielding gas requirementsShielding gas requirements

Preflow and Preflow and postflowpostflow

PreflowPreflow PostflowPostflow

Shielding gas flowShielding gas flow

Welding currentWelding current

Flow rate Flow rate too lowtoo low

Flow rate Flow rate too hightoo high

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Special shielding methodsSpecial shielding methodsPipe root run shielding Pipe root run shielding –– Back Purging to prevent Back Purging to prevent excessive oxidation during welding, normally argon.excessive oxidation during welding, normally argon.

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TIG torch setTIG torch set--upupElectrode extensionElectrode extension


StickoutStickout 22--3 times 3 times electrode electrode diameterdiameter


Low electron Low electron emission emission ��

Unstable arcUnstable arc

Too Too smallsmall

Overheating Overheating �� Tungsten Tungsten inclusionsinclusions

Too Too largelarge

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TIG Welding ConsumablesTIG Welding ConsumablesWelding consumables for TIG:Welding consumables for TIG:

•• Filler wires, Shielding gases, tungsten electrodes (nonFiller wires, Shielding gases, tungsten electrodes (non--consumable). consumable).

•• Filler wires of different materials composition and Filler wires of different materials composition and variable diameters available in standard lengths, with variable diameters available in standard lengths, with applicable code stamped for identification applicable code stamped for identification

•• Steel Filler wires of very high quality, with copper Steel Filler wires of very high quality, with copper coating to resist corrosion. coating to resist corrosion.

•• shielding gases mainly Argon and Helium, usually of shielding gases mainly Argon and Helium, usually of highest purity (99.9%).highest purity (99.9%).

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A Tungsten Inclusion always shows up as A Tungsten Inclusion always shows up as bright white on a radiographbright white on a radiograph

Tungsten InclusionTungsten Inclusion

May be caused by Thermal Shock of heating to fast and small fragments

break off and enter the weld pool, so a “slope up” device is normally fitted to prevent this could be caused by touch

down also.

Most TIG sets these days have slope-up devices that brings the current to the set level over a short period of

time so the tungsten is heated more slowly and gently

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Most welding defects with TIG are caused by a lack of welder Most welding defects with TIG are caused by a lack of welder skill, or incorrect setting of the equipment. i.e. current, torcskill, or incorrect setting of the equipment. i.e. current, torch h manipulation, welding speed, gas flow rate, etc.manipulation, welding speed, gas flow rate, etc.

•• Tungsten inclusions (low skill or wrong vertex angle)Tungsten inclusions (low skill or wrong vertex angle)

•• Surface porosity (loss of gas shield mainly on site)Surface porosity (loss of gas shield mainly on site)

•• Crater pipes (bad weld finish technique i.e. slope out)Crater pipes (bad weld finish technique i.e. slope out)

•• Oxidation of S/S weld bead, or root by poor gas coverOxidation of S/S weld bead, or root by poor gas cover

•• Root concavity (excess purge pressure in pipe)Root concavity (excess purge pressure in pipe)

•• Lack of penetration/fusion (widely on root runs)Lack of penetration/fusion (widely on root runs)

TIG typical defectsTIG typical defects

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Tungsten Inert Gas WeldingTungsten Inert Gas WeldingAdvantagesAdvantages

High qualityHigh quality

Good controlGood control

All positionsAll positions

Lowest HLowest H22 processprocess

Minimal cleaningMinimal cleaning

Autogenous weldingAutogenous welding

(No filler material)(No filler material)

Can be automatedCan be automated

DisadvantagesDisadvantages

High skill factor requiredHigh skill factor required

Low deposition rateLow deposition rate

Small consumable Small consumable rangerange

High protection requiredHigh protection required

Complex equipmentComplex equipment

Low productivityLow productivity

High ozone levels +HFHigh ozone levels +HF

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MIG/MAG WeldingMIG/MAG WeldingSection 12Section 12

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The MIG/MAG welding process was initially developed in the The MIG/MAG welding process was initially developed in the USA in the late 1940s for the welding of aluminum alloys.USA in the late 1940s for the welding of aluminum alloys.

The latest EN Welding Standards now refer the process by the The latest EN Welding Standards now refer the process by the American term GMAW (Gas Metal Arc WeldingAmerican term GMAW (Gas Metal Arc Welding))

•• The process uses a continuously fed wire electrodeThe process uses a continuously fed wire electrode

•• The weld pool is protected by a separately supplied The weld pool is protected by a separately supplied shielding gasshielding gas

•• The process is classified as a semiThe process is classified as a semi--automatic welding automatic welding process but may be fully automatedprocess but may be fully automated

•• The wire electrode can be either bare/solid wire or flux The wire electrode can be either bare/solid wire or flux cored hollow wirecored hollow wire

Gas Metal Arc WeldingGas Metal Arc Welding

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MIG/MAG MIG/MAG -- Principle of operationPrinciple of operation

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MIG/MAG process variablesMIG/MAG process variables

Welding current

Polarity

•Increasing welding current•Increase in depth and width•Increase in deposition rate

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MIG/MAG process variablesMIG/MAG process variables

Arc voltage

Travel speed•Increasing travel speed•Reduced penetration and width, undercut

•Increasing arc voltage•Reduced penetration, increased width•Excessive voltage can cause porosity, spatter and undercut

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Gas Metal Arc WeldingGas Metal Arc WeldingTypes of Shielding GasTypes of Shielding Gas

MIG (Metal Inert Gas)MIG (Metal Inert Gas)

•• Inert Gas is required for Inert Gas is required for all nonall non--ferrous alloysferrous alloys (Al, Cu, Ni)(Al, Cu, Ni)

•• Most common inert gas is ArgonMost common inert gas is Argon

•• Argon + Helium used to give a Argon + Helium used to give a ‘‘hotterhotter’’ arc arc -- better for thicker better for thicker joints and alloys with higher thermal conductivityjoints and alloys with higher thermal conductivity

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MIG/MAG MIG/MAG –– shielding gasesshielding gasesType of materialType of material Shielding gasShielding gas

Carbon steelCarbon steel

Stainless steelStainless steel

AluminiumAluminium

COCO22 , Ar+(5, Ar+(5--20)%CO20)%CO22

Ar+2%OAr+2%O22

ArAr

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MIG/MAG shielding gasesMIG/MAG shielding gases

Argon (Ar): Argon (Ar): higher density than air; low thermal conductivity higher density than air; low thermal conductivity �� the the arc has a high energy inner cone; good wetting at the arc has a high energy inner cone; good wetting at the toes; low ionisation potentialtoes; low ionisation potential

Helium (He): Helium (He): lower density than air; high thermal conductivity lower density than air; high thermal conductivity ��uniformly distributed arc energy; parabolic profile; high uniformly distributed arc energy; parabolic profile; high ionisation potentialionisation potential

Carbon Dioxide (COCarbon Dioxide (CO22):):cheap; deep penetration profile; cannot support spray cheap; deep penetration profile; cannot support spray transfer; poor wetting; high spatter transfer; poor wetting; high spatter

Ar Ar-He He CO2

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MIG/MAG shielding gasesMIG/MAG shielding gasesGases for dip transferGases for dip transfer::

COCO22: : carbon steels onlycarbon steels only: deep penetration; fast welding : deep penetration; fast welding speed; high spatter levelsspeed; high spatter levels

Ar + up to 25% COAr + up to 25% CO22: : carbon and low alloy steelscarbon and low alloy steels: : minimum spatter; good wetting and bead contourminimum spatter; good wetting and bead contour

90% He + 7.5% Ar + 2.5% CO90% He + 7.5% Ar + 2.5% CO22::stainless steelsstainless steels: : minimises undercut; small HAZminimises undercut; small HAZ

Ar: Ar: Al, Mg, Cu, Ni and their alloys on thin sectionsAl, Mg, Cu, Ni and their alloys on thin sections

Ar + He mixtures: Ar + He mixtures: Al, Mg, Cu, Ni and their alloys on Al, Mg, Cu, Ni and their alloys on thicker sections (over 3 mm)thicker sections (over 3 mm)

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MIG/MAG shielding gasesMIG/MAG shielding gasesGases for spray transferGases for spray transfer

Ar + (5Ar + (5--18)% CO18)% CO22: : carbon steelscarbon steels: minimum spatter; : minimum spatter; good wetting and bead contourgood wetting and bead contour

Ar + 2% OAr + 2% O22: : low alloy steels:low alloy steels: minimise undercut; minimise undercut; provides good toughnessprovides good toughness

Ar + 2% OAr + 2% O22 or COor CO22: : stainless steelsstainless steels: improved arc : improved arc stability; provides good fusionstability; provides good fusion

Ar: Ar: Al, Mg, Cu, Ni, Ti and their alloysAl, Mg, Cu, Ni, Ti and their alloys

Ar + He mixtures: Ar + He mixtures: Al, Cu, Ni and their alloysAl, Cu, Ni and their alloys: hotter arc : hotter arc than pure Ar to offset heat dissipationthan pure Ar to offset heat dissipation

Ar + (25Ar + (25--30)% N30)% N22: : Cu alloysCu alloys: greater heat input: greater heat input

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Gas Metal Arc WeldingGas Metal Arc WeldingTypes of Shielding GasTypes of Shielding Gas

MAG (Metal Active Gas)MAG (Metal Active Gas)

Active gases used are Oxygen and Carbon DioxideActive gases used are Oxygen and Carbon Dioxide

Argon with a small % of active gas is required for all Argon with a small % of active gas is required for all steels (including stainless steels) to ensure a stable steels (including stainless steels) to ensure a stable arc & good droplet wetting into the weld poolarc & good droplet wetting into the weld pool

Typical active gases areTypical active gases are

Ar + 20% COAr + 20% CO22 for Cfor C--Mn & low alloy steelsMn & low alloy steels

Ar + 2% OAr + 2% O22 for stainless steelsfor stainless steels

100% CO100% CO22 can be used for C can be used for C -- steelssteels

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Penetration Deep Moderate ShallowPenetration Deep Moderate ShallowExcess weld metal Maximum Moderate MinimumExcess weld metal Maximum Moderate MinimumUndercut Severe Moderate MinimumUndercut Severe Moderate Minimum

MIG/MAG Gas Metal Arc WeldingMIG/MAG Gas Metal Arc Welding

Electrode Electrode orientationorientation

Electrode extensionElectrode extension••Increased extensionIncreased extension

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MIG / MAG MIG / MAG -- selfself--regulating regulating arcarcStable conditionStable condition Sudden change in gun positionSudden change in gun position

LL 19 mm19 mm 25 mm25 mmLL’’

Arc length L = 6,4 mmArc length L = 6,4 mmArc voltage = 24VArc voltage = 24VWelding current = 250AWelding current = 250AWFS = 6,4 m/minWFS = 6,4 m/minMelt off rate = 6,4 m/minMelt off rate = 6,4 m/min

Arc length LArc length L’’ = 12,7 mm= 12,7 mmArc voltage = 29VArc voltage = 29VWelding current = 220AWelding current = 220AWFS = 6,4 m/minWFS = 6,4 m/minMelt off rate = 5,6 Melt off rate = 5,6 m/minm/min

Current (A)Current (A)

Volta

ge (V

)Vo

ltage

(V)

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MIG/MAG MIG/MAG -- selfself--regulating arcregulating arcSudden change in gun positionSudden change in gun position

25 mm25 mmLL’’

Arc length LArc length L’’ = 12,7 mm= 12,7 mmArc voltage = 29VArc voltage = 29VWelding current = 220AWelding current = 220AWFS = 6,4 m/minWFS = 6,4 m/minMelt off rate = 5,6 m/minMelt off rate = 5,6 m/min

Current (A)Current (A)

Volta

ge (V

)Vo

ltage

(V)

ReRe--established stable conditionestablished stable condition

25 mm25 mmLL

Arc length L = 6,4 mmArc length L = 6,4 mmArc voltage = 24VArc voltage = 24VWelding current = 250AWelding current = 250AWFS = 6,4 m/minWFS = 6,4 m/minMelt off rate = 6,4 m/minMelt off rate = 6,4 m/min

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Terminating the arcTerminating the arc

Burnback timeBurnback time–– delayed current cutdelayed current cut--off to prevent wire freeze off to prevent wire freeze

in the weld end craterin the weld end crater–– depends on WFS (set as short as possible!)depends on WFS (set as short as possible!)

Contact tipContact tip

WorkpiecWorkpiecee

Burnback timeBurnback time 0.05 sec0.05 sec 0.10 sec0.10 sec 0.15 sec0.15 sec

14 mm 14 mm 8 mm 8 mm

3 mm 3 mm Current Current -- 250A250AVoltage Voltage -- 27V27VWFS WFS -- 7,8 m/min7,8 m/minWire Wire diamdiam. . -- 1,2 mm1,2 mmShielding gas Shielding gas --Ar+18%COAr+18%CO22

InsulatinInsulating slagg slag

Crater fillCrater fill

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MIG/MAG MIG/MAG -- metal transfer modesmetal transfer modes

SetSet--up for dip transferup for dip transfer SetSet--up for spray transferup for spray transfer

Electrode Electrode extension extension 1919--25 mm25 mm

Contact tip Contact tip recessed recessed (3(3--5 mm)5 mm)

Contact tip Contact tip extension extension (0(0--3,2 mm)3,2 mm)

Electrode Electrode extension extension 66--13 mm13 mm

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MIG/MAG MIG/MAG -- metal transfer modesmetal transfer modes

Current/voltage conditionsCurrent/voltage conditions

CurrentCurrent

VoltageVoltage

Dip transferDip transfer

Spray Spray transfertransfer

Globular Globular transfertransfer

Electrode diameter = 1,2 mmElectrode diameter = 1,2 mm

WFS = 3,2 m/minWFS = 3,2 m/min

Current = 145 ACurrent = 145 A

Voltage = 18Voltage = 18--20V20V

Electrode diameter = 1,2 mmElectrode diameter = 1,2 mm

WFS = 8,3 m/minWFS = 8,3 m/min

Current = 295 ACurrent = 295 A

Voltage = 28VVoltage = 28V

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MIG/MAGMIG/MAG--methods of metal transfermethods of metal transferDip transferDip transfer

Transfer occur due to short circuits Transfer occur due to short circuits between wire and weld pool,between wire and weld pool, high high level of spatter, need inductance level of spatter, need inductance control to limit current raisecontrol to limit current raiseCan use pure COCan use pure CO22 or Aror Ar-- COCO22mixtures as shielding gasmixtures as shielding gasMetal transfer occur when arc is Metal transfer occur when arc is extinguishedextinguishedRequires low welding current/arc Requires low welding current/arc voltage, avoltage, a low heat input process. low heat input process. Resulting in low residual stress Resulting in low residual stress and distortionand distortionUsed for thin materials and all Used for thin materials and all position weldsposition welds

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MIG/MAGMIG/MAG--methods of metal transfermethods of metal transferSpray transfer Spray transfer

Transfer occur due to pinch Transfer occur due to pinch effect effect NO contact between wire NO contact between wire and weld pool!and weld pool!

Requires argonRequires argon--rich shielding rich shielding gasgas

Metal transfer occur in small Metal transfer occur in small droplets, adroplets, a large volume weld large volume weld poolpool

Requires high welding Requires high welding current/arc voltage, a current/arc voltage, a high heat high heat input process. Resulting in high input process. Resulting in high residual stress and distortionresidual stress and distortion

Used for thick materials and Used for thick materials and flat/horizontal position weldsflat/horizontal position welds

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MIG/MAGMIG/MAG--methods of metal transfermethods of metal transferPulsed transferPulsed transfer

Controlled metal transfer,Controlled metal transfer, one droplet per pulse, one droplet per pulse,

No transfer between droplet and weld pool!No transfer between droplet and weld pool!

Requires special power sourcesRequires special power sources

Metal transfer occur in small droplets (diameter equal Metal transfer occur in small droplets (diameter equal to that of electrode)to that of electrode)

Requires moderate welding current/arc voltage, a Requires moderate welding current/arc voltage, a reduced heat input . Resulting in smaller residual reduced heat input . Resulting in smaller residual stress and distortion compared to spray transferstress and distortion compared to spray transfer

Pulse frequency controls the volume of weld pool, Pulse frequency controls the volume of weld pool, used for root runs and out of position weldsused for root runs and out of position welds

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MIG/MAG MIG/MAG -- metal transfer modesmetal transfer modesPulsed transferPulsed transfer

Controlled metal transfer.Controlled metal transfer. one droplet one droplet per pulse. NO transfer during per pulse. NO transfer during background current!background current!Requires special power sourcesRequires special power sourcesMetal transfer occur in small droplets Metal transfer occur in small droplets (diameter equal to that of electrode)(diameter equal to that of electrode)

Requires moderate welding current/arc voltage,Requires moderate welding current/arc voltage, reduced reduced heat inputheat input’’ smaller residual stress and distortions smaller residual stress and distortions compared to spray transfercompared to spray transferPulse frequency controls the volume of weld pool, used Pulse frequency controls the volume of weld pool, used for root runs and out of position weldsfor root runs and out of position welds

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MIG/MAGMIG/MAG--methods of metal transfermethods of metal transfer

Globular transfer Globular transfer Transfer occur due to gravity Transfer occur due to gravity or or short circuits between drops and short circuits between drops and weld poolweld poolRequires CORequires CO22 shielding gasshielding gasMetal transfer occur in large drops Metal transfer occur in large drops (diameter larger than that of (diameter larger than that of electrode) hence electrode) hence severe spattersevere spatterRequires high welding current/arc Requires high welding current/arc voltage, a voltage, a high heat input process. high heat input process. Resulting in high residual stress Resulting in high residual stress and distortionand distortionNon desired mode of transfer!Non desired mode of transfer!

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O.C.V. Arc Voltage O.C.V. Arc Voltage Virtually no Change. Virtually no Change.

VoltageVoltage

Flat or Constant Voltage Characteristic Used With Flat or Constant Voltage Characteristic Used With

MIG/MAG, ESW & SAW < 1000 ampsMIG/MAG, ESW & SAW < 1000 amps

100100 200200 300300

3333

3232

3131

Large Current ChangeLarge Current Change

Small Voltage Small Voltage Change. Change.

AmperageAmperage

Flat or Constant Voltage CharacteristicFlat or Constant Voltage Characteristic

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MIG/MAG welding gun assemblyMIG/MAG welding gun assembly

Contact Contact tiptip

Gas Gas diffuserdiffuser

HandleHandle

Gas Gas nozzlenozzle

TriggerTrigger WFS remote WFS remote control control potentiometerpotentiometer

Union nutUnion nut

The PushThe Push--Pull gunPull gun

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Gas Metal Arc WeldingGas Metal Arc WeldingPROCESS CHARACTERISTICSPROCESS CHARACTERISTICS

•• Requires a constant voltage power source, gas supply, wire Requires a constant voltage power source, gas supply, wire feeder, welding torch/gun and feeder, welding torch/gun and ‘‘hose packagehose package’’

•• Wire is fed continuously through the conduit and is burntWire is fed continuously through the conduit and is burnt--off off at a rate that maintains a constant arc length/arc voltageat a rate that maintains a constant arc length/arc voltage

•• Wire feed speed is directly related to burnWire feed speed is directly related to burn--off rateoff rate

•• Wire burnWire burn--off rate is directly related to currentoff rate is directly related to current

•• When the welder holds the welding gun the process is said When the welder holds the welding gun the process is said to be a semito be a semi--automatic processautomatic process

•• The process can be mechanised and also automatedThe process can be mechanised and also automated

•• In Europe the process is usually called MIG or MAGIn Europe the process is usually called MIG or MAG

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Most welding imperfections in MIG/MAG are caused by lack of Most welding imperfections in MIG/MAG are caused by lack of welder skill, or incorrect settings of the equipmentwelder skill, or incorrect settings of the equipment

••Worn contact tips will cause poor power pick up, or transferWorn contact tips will cause poor power pick up, or transfer

••Bad power connections will cause a loss of voltage in the arcBad power connections will cause a loss of voltage in the arc

••Silica inclusions (in Fe steels) due to poor interSilica inclusions (in Fe steels) due to poor inter--run cleaningrun cleaning

••Lack of fusion (primarily with dip transfer)Lack of fusion (primarily with dip transfer)

••Porosity (from loss of gas shield on site etc)Porosity (from loss of gas shield on site etc)

••Solidification problems (cracking, centerline pipes, crater Solidification problems (cracking, centerline pipes, crater pipes) especially on deep narrow weldspipes) especially on deep narrow welds

MIG/MAG typical defectsMIG/MAG typical defects

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Flux Core Arc WeldingFlux Core Arc Welding

(Not In The Training Manual)(Not In The Training Manual)

WELDING PROCESSWELDING PROCESS

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Flux cored arc weldingFlux cored arc welding

FCAW FCAW methodsmethods

With gas With gas shielding shielding --

““OutershieldOutershield””

Without gas Without gas shielding shielding --

““InnershieldInnershield””

With metal With metal powder powder --

““Metal coreMetal core””

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““OutershieldOutershield”” -- principle of operationprinciple of operation

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““InnershieldInnershield”” -- principle of operationprinciple of operation

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VoltsVolts

AmpsAmps

OCVOCV

Constant Voltage CharacteristicConstant Voltage Characteristic

Small change in voltage = Small change in voltage = large change in amperagelarge change in amperage

The self The self adjusting arc.adjusting arc.

Large arc gapLarge arc gap

Small arc gapSmall arc gap

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Insulated extension nozzleInsulated extension nozzle

Current carrying guild tube Current carrying guild tube

Flux cored hollow wire Flux cored hollow wire

Flux powderFlux powderArc shield composed of Arc shield composed of vaporized and slag forming vaporized and slag forming compounds compounds

Metal droplets covered Metal droplets covered with thin slag coating with thin slag coating

Molten Molten weld weld poolpoolSolidified weld Solidified weld

metal and slagmetal and slag

Flux coreFlux core

Wire jointWire joint

Flux core Flux core wireswires

Flux Core Arc Welding (FCAW)Flux Core Arc Welding (FCAW)

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Flux cored arc weldingFlux cored arc weldingFCAW FCAW

methodsmethods

With gas With gas shielding shielding --

““OutershieldOutershield””

Without gas Without gas shielding shielding --

““InnershieldInnershield””(114)(114)

With metal With metal powder powder --

““Metal coreMetal core””

With active With active gas shielding gas shielding

(136)(136)

With inert gas With inert gas shielding (137)shielding (137)

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FCAW FCAW -- differences from MIG/MAGdifferences from MIG/MAG

usually operates in DCEP usually operates in DCEP but some but some ““InnershieldInnershield””wires operates in DCENwires operates in DCENpower sources need to power sources need to be more powerful due to be more powerful due to the higher currentsthe higher currentsdoesn't work in deep doesn't work in deep transfer modetransfer moderequire knurled feed rolls require knurled feed rolls

““InnershieldInnershield”” wires use wires use a different type of a different type of welding gun welding gun

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Backhand (Backhand (““dragdrag””) technique) techniqueAdvantagesAdvantages

preferred method for flat or horizontal positionpreferred method for flat or horizontal positionslower progression of the weldslower progression of the welddeeper penetrationdeeper penetrationweld stays hot longer,weld stays hot longer, easy to remove dissolved easy to remove dissolved gassesgasses

DisadvantagesDisadvantagesproduce a higher weld profileproduce a higher weld profiledifficult to follow the weld jointdifficult to follow the weld jointcan lead to burncan lead to burn--through on thin sheet platesthrough on thin sheet plates

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Forehand (Forehand (““pushpush””) technique) technique

AdvantagesAdvantagespreferred method for vertical up or overhead preferred method for vertical up or overhead positionpositionarc is directed towards the unwelded joint arc is directed towards the unwelded joint , preheat , preheat effecteffecteasy to follow the weld joint and control the easy to follow the weld joint and control the penetrationpenetration

DisadvantagesDisadvantagesproduce a low weld profile, with coarser ripplesproduce a low weld profile, with coarser ripplesfast weld progression, shallower depth of penetrationfast weld progression, shallower depth of penetrationthe amount of spatter can increasethe amount of spatter can increase

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FCAW advantagesFCAW advantagesless sensitive to lack of fusionless sensitive to lack of fusionrequires smaller included angle compared to MMArequires smaller included angle compared to MMAhigh productivityhigh productivityall positionalall positionalsmooth bead surface, less danger of undercutsmooth bead surface, less danger of undercutbasic types produce excellent toughness propertiesbasic types produce excellent toughness propertiesgood control of the weld pool in positional welding good control of the weld pool in positional welding especially with rutile wiresespecially with rutile wiresseamless wires have no torsional strain, twist freeseamless wires have no torsional strain, twist freeease of varying the alloying constituentsease of varying the alloying constituentsno need for shielding gasno need for shielding gas

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FCAW disadvantagesFCAW disadvantageslimited to steels and Nilimited to steels and Ni--base alloysbase alloysslag covering must be removedslag covering must be removedFCAW wire is more expensive on a weight basis FCAW wire is more expensive on a weight basis than solid wires (exception: some high alloy steels)than solid wires (exception: some high alloy steels)for gas shielded process, the gaseous shield may be for gas shielded process, the gaseous shield may be affected by winds and draftsaffected by winds and draftsmore smoke and fumes are generated compared more smoke and fumes are generated compared with MIG/MAGwith MIG/MAGin case of Innershield wires, it might be necessary to in case of Innershield wires, it might be necessary to break the wire for restart (due to the high amount of break the wire for restart (due to the high amount of insulating slag formed at the tip of the wire)insulating slag formed at the tip of the wire)

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Advantages:Advantages:

1) Field or shop use1) Field or shop use

2) High productivity2) High productivity

3) All positional3) All positional

4) Slag supports and 4) Slag supports and shapes the weld Beadshapes the weld Bead

5) No need for shielding 5) No need for shielding gasgas

Disadvantages:Disadvantages:

1) High skill factor1) High skill factor

2) Slag inclusions2) Slag inclusions

3) Cored wire is 3) Cored wire is ExpensiveExpensive

4) High level of fume 4) High level of fume (Inner(Inner--shield)shield)

5) Limited to steels and 5) Limited to steels and nickel alloysnickel alloys

FCAW advantages/disadvantagesFCAW advantages/disadvantages

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Submerged Arc WeldingSubmerged Arc WeldingSection 13Section 13

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• Submerged arc welding was developed in the Soviet Union during the 2nd world war for the welding of thick section steel.

• The process is normally mechanized.

• The process uses amps in the range of 100 to over 2000, which gives a very high current density in the wire producing deep penetration and high dilution welds.

• A flux is supplied separately via a flux hopper in the form of either fused or agglomerated.

• The arc is not visible as it is submerged beneath the flux layerand no eye protection is required.

Submerged Arc Welding IntroductionSubmerged Arc Welding Introduction

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SAW Principle of operationSAW Principle of operation

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Principles of operationPrinciples of operationFactors that determine whether to use SAWFactors that determine whether to use SAW chemical chemical composition and mechanical properties required for the weld composition and mechanical properties required for the weld depositdeposit

•• thickness of base metal to be weldedthickness of base metal to be welded

•• joint accessibilityjoint accessibility

•• position in which the weld is to be madeposition in which the weld is to be made

•• frequency or volume of welding to be performedfrequency or volume of welding to be performed

SAW methodsSAW methods

SemiautomaticSemiautomatic MechanisedMechanised AutomaticAutomatic

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Submerged Arc WeldingSubmerged Arc Welding

-- ++

Power Power supplysupply

Filler wire spoolFiller wire spoolFlux hopperFlux hopper

Wire electrodeWire electrode

FluxFlux

Slide railSlide rail

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SAW process variablesSAW process variables•• welding currentwelding current•• current type and polaritycurrent type and polarity•• welding voltagewelding voltage•• travel speedtravel speed•• electrode sizeelectrode size•• electrode extensionelectrode extension•• width and depth of the layer of fluxwidth and depth of the layer of flux

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SAW process variablesSAW process variablesWelding currentWelding current

••controls depth of penetration and the amount of controls depth of penetration and the amount of base metal melted base metal melted && dilutiondilution

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SAW operating variablesSAW operating variablesCurrent type and polarityCurrent type and polarity

••Usually DCEP, deep Usually DCEP, deep penetration, better penetration, better resistance to resistance to porosityporosity

••DCEN increase DCEN increase deposition rate but deposition rate but reduce penetration reduce penetration (surfacing)(surfacing)

••AC used to avoid AC used to avoid arc blow; can give arc blow; can give unstable arcunstable arc

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SAW ConsumablesSAW Consumables(Covered in detail in Section 14)(Covered in detail in Section 14)

Fused fluxes advantages:Fused fluxes advantages:••good chemical homogeneitygood chemical homogeneity••easy removal of fines without affecting flux easy removal of fines without affecting flux compositioncomposition••normally not hygroscopic normally not hygroscopic & easy storage and handling& easy storage and handling••readily recycled without significant change in particle readily recycled without significant change in particle size or compositionsize or composition

Fused fluxes disadvantages:Fused fluxes disadvantages:••difficult to add deoxidizers and ferrodifficult to add deoxidizers and ferro--alloys (due to alloys (due to segregation or extremely high loss)segregation or extremely high loss)••high temperatures needed to melt ingredients limit the high temperatures needed to melt ingredients limit the range of flux compositionsrange of flux compositions

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SAW ConsumablesSAW ConsumablesAgglomerated fluxes advantages:Agglomerated fluxes advantages:

•• easy addition of deoxidizers and alloying elementseasy addition of deoxidizers and alloying elements

•• usable with thicker layer of flux when weldingusable with thicker layer of flux when welding

•• colour identificationcolour identification

Agglomerated fluxes disadvantages:Agglomerated fluxes disadvantages:

•• tendency to absorb moisturetendency to absorb moisture

•• possible gas evolution from the molten slag leading to possible gas evolution from the molten slag leading to porosityporosity

•• possible change in flux composition due to segregation or possible change in flux composition due to segregation or removal of fine mesh particlesremoval of fine mesh particles

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SAW equipmentSAW equipmentPower sources can be:Power sources can be:

•• transformers for ACtransformers for AC

•• transformertransformer--rectifiers for DCrectifiers for DC

Static characteristic can be:Static characteristic can be:

•• Constant Voltage (flat) Constant Voltage (flat) -- most of the power sourcesmost of the power sources

•• Constant Current (drooping)Constant Current (drooping)

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SAW equipmentSAW equipmentConstant Voltage (Flat Characteristic) power sources:Constant Voltage (Flat Characteristic) power sources:

•• most commonly used supplies for SAWmost commonly used supplies for SAW

•• can be used for both semiautomatic and automatic weldingcan be used for both semiautomatic and automatic welding

•• selfself--regulating arcregulating arc

•• simple wire feed speed controlsimple wire feed speed control

•• wire feed speed controls the current and power supply wire feed speed controls the current and power supply controls the voltagecontrols the voltage

•• applications for DC are limited to 1000A due to severe arc applications for DC are limited to 1000A due to severe arc blow (also thin wires!)blow (also thin wires!)

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Volts

Amps

OCV

Constant Voltage Characteristic

Small change in voltage = large change in amperage

The self adjusting arc.

Large arc gap

Small arc gap

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SAW equipmentSAW equipmentConstant Current (Drooping Characteristic) power sources:Constant Current (Drooping Characteristic) power sources:

•• Over 1000A Over 1000A -- very fast speed required very fast speed required -- control of burn off control of burn off rate and stick out lengthrate and stick out length

•• can be used for both semiautomatic and automatic weldingcan be used for both semiautomatic and automatic welding

•• not selfnot self--regulating arcregulating arc

•• must be used with a voltagemust be used with a voltage--sensing variable wire feed sensing variable wire feed speed controlspeed control

•• more expensive due to more complex wire feed speed more expensive due to more complex wire feed speed controlcontrol

•• arc voltage depends upon wire feed speed whilst the power arc voltage depends upon wire feed speed whilst the power source controls the currentsource controls the current

•• cannot be used for highcannot be used for high--speed welding of thin steelspeed welding of thin steel

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SAW equipmentSAW equipmentWelding heads can be mounted on a:Welding heads can be mounted on a:

Tractor type carriageTractor type carriage

•• provides travel along straight or provides travel along straight or gently curved jointsgently curved joints

•• can ride on tracks set up along the can ride on tracks set up along the joint (with grooved wheels) or on joint (with grooved wheels) or on the workpiece itselfthe workpiece itself

•• can use guide wheels as tracking can use guide wheels as tracking device device

•• due to their portability, are used in due to their portability, are used in field welding or where the piece field welding or where the piece cannot be movedcannot be moved

Courtesy of ESAB ABCourtesy of ESAB AB


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SAW operating variablesSAW operating variablesWelding currentWelding current••too high current: excessive excess weld metal too high current: excessive excess weld metal (waste of electrode), increase weld shrinkage and (waste of electrode), increase weld shrinkage and causes greater distortionscauses greater distortions

••excessively high current:excessively high current: digging arc, undercut, digging arc, undercut, burn through; also a high and narrow bead & burn through; also a high and narrow bead & solidification crackingsolidification cracking

••too low current:too low current: incomplete incomplete fusion or inadequate penetrationfusion or inadequate penetration

••excessively low current: excessively low current: unstable arcunstable arc

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SAW operating variablesSAW operating variables

Welding voltageWelding voltage••welding voltage controls arc welding voltage controls arc lengthlength

••an increased voltage can increase pickan increased voltage can increase pick--up of alloying elements up of alloying elements from an alloy fluxfrom an alloy flux

••increase in voltage produce a increase in voltage produce a flatter and wider beadflatter and wider bead

••increase in voltage increase increase in voltage increase flux consumptionflux consumption

••increase in voltage tend to increase in voltage tend to reduce porosityreduce porosity

••an increased voltage may an increased voltage may help bridging an excessive help bridging an excessive root gaproot gap

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SAW operating variablesSAW operating variables

Welding voltageWelding voltage

••low voltage produce a low voltage produce a ““stifferstiffer”” arc & improves arc & improves penetration in a deep penetration in a deep weld groove and resists weld groove and resists arc blow arc blow

••excessive low voltage excessive low voltage produce a high narrow produce a high narrow bead & difficult slag bead & difficult slag removalremoval

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SAW operating variablesSAW operating variablesWelding voltageWelding voltage

••excessively high voltage excessively high voltage produce a produce a ““hathat--shapedshaped”” bead bead & tendency to crack & tendency to crack

••excessively high voltage excessively high voltage increase undercut & make slag increase undercut & make slag removal difficult in groove removal difficult in groove weldswelds

••excessively high voltage excessively high voltage produce a concave fillet weld produce a concave fillet weld that is subject to crackingthat is subject to cracking

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SAW operating variablesSAW operating variablesTravel speedTravel speed••increase in travel speed: decrease heat input increase in travel speed: decrease heat input & less & less filler metal applied per unit of length, less excess filler metal applied per unit of length, less excess weld metalweld metal && weld bead becomes smallerweld bead becomes smaller

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SAW operating variablesSAW operating variablesTravel speedTravel speed

••excessively high speed excessively high speed lead to undercut, arc lead to undercut, arc blow and porosity blow and porosity

••excessively low speed excessively low speed produce produce ““hathat--shapedshaped”” beads beads �� danger of crackingdanger of cracking

••excessively low speed produce rough beads and excessively low speed produce rough beads and lead to slag inclusionslead to slag inclusions

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SAW operating variablesSAW operating variablesElectrode sizeElectrode size

••at the same current, small electrodes have higher at the same current, small electrodes have higher current density current density & higher deposition rates& higher deposition rates

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SAW operating variablesSAW operating variablesElectrode extensionElectrode extension

••increased electrode extension adds resistance in the increased electrode extension adds resistance in the welding circuit welding circuit I increase in deposition rate, decrease in I increase in deposition rate, decrease in penetration and bead widthpenetration and bead width

••to keep a proper weld shape, when electrode extension is to keep a proper weld shape, when electrode extension is increased, voltage must also be increasedincreased, voltage must also be increased

••when burnwhen burn--through is a problem (e.g. thin gauge), increase through is a problem (e.g. thin gauge), increase electrode extensionelectrode extension

••excessive electrode extension: it is more difficult to excessive electrode extension: it is more difficult to maintain the electrode tip in the correct positionmaintain the electrode tip in the correct position

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SAW operating variablesSAW operating variablesDepth of fluxDepth of flux

••depth of flux layer influence the appearance of welddepth of flux layer influence the appearance of weld

••usually, depth of flux is 25usually, depth of flux is 25--30 mm30 mm

••if flux layer is to deep if flux layer is to deep the arc is too confined, result is the arc is too confined, result is a rough ropelike appearing welda rough ropelike appearing weld

••if flux layer is to deep the gases cannot escape & the if flux layer is to deep the gases cannot escape & the surface of molten weld metal becomes irregularly surface of molten weld metal becomes irregularly distorteddistorted

••if flux layer is too shallow, flashing and spattering will if flux layer is too shallow, flashing and spattering will occur, give a poor appearance and porous weldoccur, give a poor appearance and porous weld

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SAW technological variablesSAW technological variablesTravel angle effect Travel angle effect -- Butt weld on platesButt weld on plates

Penetration Deep Moderate SPenetration Deep Moderate ShallowhallowExcess weld metal Maximum Moderate MinimumExcess weld metal Maximum Moderate MinimumTendency to undercut Severe Moderate MinimumTendency to undercut Severe Moderate Minimum

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SAW technological variablesSAW technological variablesEarth positionEarth position ++

--

Direction of Direction of traveltravel

••welding towards earth produces backward arc blowwelding towards earth produces backward arc blow

••deep penetrationdeep penetration

••convex weld profileconvex weld profile

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SAW technological variablesSAW technological variablesEarth positionEarth position

++

--

Direction of Direction of traveltravel

••welding away earth produces forward arc blowwelding away earth produces forward arc blow

••normal penetration depthnormal penetration depth

••smooth, even weld profilesmooth, even weld profile

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Weld backingWeld backing

Backing stripBacking strip

Backing weldBacking weld

Copper backingCopper backing

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Starting/finishing the weldStarting/finishing the weld

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SAW variantsSAW variants

Twin wire SAW weldingTwin wire SAW welding ••two electrodes are feed two electrodes are feed into the same weld poolinto the same weld pool

••wire diameter usually 1,6 to wire diameter usually 1,6 to 3,2 mm3,2 mm

••electrodes are connected electrodes are connected to a single power source to a single power source & a & a single arc is establishedsingle arc is established

••normally operate with normally operate with DCEP DCEP

••offers increased deposition offers increased deposition rate by up to 80% compared rate by up to 80% compared to single wire SAWto single wire SAW

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Wires can be oriented Wires can be oriented for maximum or for maximum or minimum penetrationminimum penetration

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SAW variantsSAW variantsTandem arc SAW processTandem arc SAW process ••usually DCEP on lead usually DCEP on lead

and AC on trail toand AC on trail to reduce reduce arc blowarc blow

••requires two separate requires two separate power sourcespower sources

••the electrodes are active the electrodes are active in the same puddle BUT in the same puddle BUT there are 2 separate arcsthere are 2 separate arcs

••increased deposition increased deposition rate by up to 100% rate by up to 100% compared with single compared with single wire SAW wire SAW

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SAW variantsSAW variantsSAW tandem arc SAW tandem arc with two wireswith two wires


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Single pool Single pool -- highest deposition ratehighest deposition rate

Twin pool Twin pool -- travel speed limited by undercut; travel speed limited by undercut; very resistant to porosity and cracksvery resistant to porosity and cracks

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Tandem arc SAW process Tandem arc SAW process -- multiple wiresmultiple wires

••only for welding thick only for welding thick sections (>30 mm)sections (>30 mm)

••not suitable for use in not suitable for use in narrow weld narrow weld preparations (root preparations (root passes)passes)

••one 4 mm wire at 600 A,one 4 mm wire at 600 A,6.8 kg/hr6.8 kg/hr

••tandem two 4 mm wires tandem two 4 mm wires at 600 A, 13.6 kg/hrat 600 A, 13.6 kg/hrCourtesy of ESAB ABCourtesy of ESAB AB

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SAW variantsSAW variantsStrip cladding needs aStrip cladding needs a

special welding headspecial welding head

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SAW variants SAW variants Narrow gap weldingNarrow gap welding

••for welding thick for welding thick materialsmaterials••less filler metal requiredless filler metal required••requires special groove requires special groove preparation and special preparation and special welding headwelding head••requires special fluxes, requires special fluxes, otherwise problems with otherwise problems with slag removalslag removal••defect removal is very defect removal is very difficultdifficult

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SAW variants SAW variants Hot wire weldingHot wire welding

••the hot wire is connected to power source the hot wire is connected to power source & much & much more efficient than cold wire (current is used entirely more efficient than cold wire (current is used entirely to heat the wire!)to heat the wire!)••increase deposition rates increase deposition rates up to 100%up to 100%

••requires additional requires additional welding equipment, welding equipment, additional control of additional control of variables, considerable variables, considerable setset--up time and closer up time and closer operator attentionoperator attention

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SAW variantsSAW variantsSAW with metal powder additionSAW with metal powder addition

••increased deposition rates up to increased deposition rates up to 70%; increased welding speed70%; increased welding speed••gives smooth fusion, improved gives smooth fusion, improved bead appearance, reduced bead appearance, reduced penetration and dilution from parent penetration and dilution from parent metal metal & higher impact strength& higher impact strength••metal powders can modify metal powders can modify chemical composition of final weld chemical composition of final weld depositdeposit••does not increase risk of crackingdoes not increase risk of cracking••do not require additional arc energydo not require additional arc energy••metal powder can be added ahead metal powder can be added ahead or directly into the weld poolor directly into the weld pool

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SAW variants SAW variants SAW with metal powder additionSAW with metal powder addition

••magnetic attachment of powdermagnetic attachment of powder

••SAW with metal cored wiresSAW with metal cored wires

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SAW variants SAW variants Storage tank Storage tank SAW of circular SAW of circular weldswelds


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Advantages of SAWAdvantages of SAW•• high current density,high current density, high deposition rates (up to 10 times high deposition rates (up to 10 times

those for MMA), high productivitythose for MMA), high productivity•• deep penetration allowing the use of small welding groovesdeep penetration allowing the use of small welding grooves•• fast travel speed, less distortionfast travel speed, less distortion•• deslagging is easierdeslagging is easier•• uniform bead appearance with good surface finish and good uniform bead appearance with good surface finish and good

fatigue propertiesfatigue properties•• can be easily performed mechanised, giving a higher duty can be easily performed mechanised, giving a higher duty

cycle and low skill level required cycle and low skill level required •• provide consistent quality when performed automatic or provide consistent quality when performed automatic or

mechanisedmechanised•• Virtually assured radiographically sound weldsVirtually assured radiographically sound welds•• arc is not visiblearc is not visible•• little smoke/fumes are developedlittle smoke/fumes are developed

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AdvantagesAdvantages

•• Low weldLow weld--metal costmetal cost

•• Easily automatedEasily automated

•• Low levels of ozoneLow levels of ozone

•• High productivityHigh productivity

•• No visible arc lightNo visible arc light

•• Minimum cleaningMinimum cleaning


•• Restricted welding Restricted welding positionspositions

•• Arc blow on DC Arc blow on DC currentcurrent

•• Shrinkage defectsShrinkage defects

•• Difficult penetration Difficult penetration controlcontrol

•• Limited jointsLimited joints

Submerged Arc WeldingSubmerged Arc Welding

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Welding ConsumablesWelding ConsumablesSection 14Section 14

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BS EN 499 MMA Covered ElectrodesBS EN 499 MMA Covered Electrodes

Covered ElectrodeCovered Electrode

ToughnessToughnessYield Strength N/mmYield Strength N/mm22

Chemical compositionChemical compositionFlux CoveringFlux CoveringWeld Metal RecoveryWeld Metal Recoveryand Current Typeand Current TypeWelding PositionWelding PositionHydrogen ContentHydrogen Content

EE 5050 33 2Ni2Ni BB 77 22 H10H10

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Welding consumables are any products that are used up in Welding consumables are any products that are used up in the production of a weldthe production of a weld

Welding consumables may be:Welding consumables may be:

•• Covered electrodes, filler wires and electrode wires.Covered electrodes, filler wires and electrode wires.

•• Shielding or oxyShielding or oxy--fuel gases.fuel gases.

•• Separately supplied fluxes.Separately supplied fluxes.

•• Fusible inserts.Fusible inserts.

Welding consumablesWelding consumables

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Welding Consumable StandardsWelding Consumable Standards

MMA (SMAW)MMA (SMAW)•• BS EN 499: Steel electrodesBS EN 499: Steel electrodes

•• AWS A5.1 NonAWS A5.1 Non--alloyed steel alloyed steel


•• AWS A5.4 Chromium AWS A5.4 Chromium


•• AWS A5.5 Alloyed steel AWS A5.5 Alloyed steel


MIG/MAG (GMAW) TIG MIG/MAG (GMAW) TIG

(GTAW)(GTAW)BS 2901: Filler wires BS 2901: Filler wires

BS EN 440: Wire electrodesBS EN 440: Wire electrodes

AWS A5.9: Filler wiresAWS A5.9: Filler wires

BS EN 439: Shielding gasesBS EN 439: Shielding gases

SAWSAWBS 4165: Wire and fluxesBS 4165: Wire and fluxes

BS EN 756: Wire electrodesBS EN 756: Wire electrodes

BS EN 760: FluxesBS EN 760: Fluxes

AWS A5.17: Wires and fluxesAWS A5.17: Wires and fluxes

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Welding Consumable GasesWelding Consumable Gaseswelding gaseswelding gases

•• GMAW, FCAW, TIG, OxyGMAW, FCAW, TIG, Oxy-- FuelFuel•• Supplied in cylinders or Supplied in cylinders or storage storage

tanks for large quantitiestanks for large quantities•• Colour coded cylinders to minimise Colour coded cylinders to minimise

wrong usewrong use•• Subject to regulations concerned Subject to regulations concerned

handling, quantities and positioning handling, quantities and positioning of storage areasof storage areas

•• Moisture content is limited to avoid Moisture content is limited to avoid cold crackingcold cracking

•• Dew point (the temperature at which Dew point (the temperature at which the vapour begins to condense) the vapour begins to condense) must be checkedmust be checked

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Welding ConsumablesWelding ConsumablesEach consumable is critical in respect to:Each consumable is critical in respect to:

•• Size, (diameter and length)Size, (diameter and length)

•• Classification / SupplierClassification / Supplier

•• ConditionCondition

•• Treatments e.g. baking / dryingTreatments e.g. baking / drying

•• Handling and storage is critical for consumable Handling and storage is critical for consumable

controlcontrol

•• Handling and storage of gases is critical for safetyHandling and storage of gases is critical for safety

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The three main electrode covering types used in MMA weldingThe three main electrode covering types used in MMA welding

•• CellulosicCellulosic -- deep penetration/fusion deep penetration/fusion

•• RutileRutile -- general purposegeneral purpose

•• BasicBasic -- low hydrogenlow hydrogen


MMA Covered ElectrodesMMA Covered Electrodes

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MMA Welding ConsumablesMMA Welding ConsumablesWelding consumables for MMA:Welding consumables for MMA:

•• Consist of a core wire typically between 350Consist of a core wire typically between 350--450mm in 450mm in length and from 2.5mm length and from 2.5mm -- 6mm in diameter6mm in diameter

•• The wire is covered with an extruded flux coatingThe wire is covered with an extruded flux coating

•• The core wire is generally of a low quality rimming steelThe core wire is generally of a low quality rimming steel

•• The weld quality is refined by the addition of alloying The weld quality is refined by the addition of alloying and refining agents in the flux coatingand refining agents in the flux coating

•• The flux coating contains many elements and The flux coating contains many elements and compounds that all have a variety of functions during compounds that all have a variety of functions during weldingwelding

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MMA Welding ConsumablesMMA Welding ConsumablesFunction of the Electrode Covering:Function of the Electrode Covering:•• To facilitate arc ignition and give arc stabilityTo facilitate arc ignition and give arc stability

•• To generate gas for shielding the arc & molten metal from air To generate gas for shielding the arc & molten metal from air contaminationcontamination

•• To deTo de--oxidise the weld metal and flux impurities into the slagoxidise the weld metal and flux impurities into the slag

•• To form a protective slag blanket over the solidifying and To form a protective slag blanket over the solidifying and cooling weld metalcooling weld metal

•• To provide alloying elements to give the required weld metal To provide alloying elements to give the required weld metal propertiesproperties

•• To aid positional welding (slag design to have suitable To aid positional welding (slag design to have suitable freezing temperature to support the molten weld metal)freezing temperature to support the molten weld metal)

•• To control hydrogen contents in the weld (basic type)To control hydrogen contents in the weld (basic type)

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1: Electrode size (diameter and length)1: Electrode size (diameter and length)

2: Covering condition: adherence, cracks, chips and concentricit2: Covering condition: adherence, cracks, chips and concentricityy

3: Electrode designation3: Electrode designation

EN 499-E 51 3 B

Arc ignition enhancing materials (optional!)Arc ignition enhancing materials (optional!)

See BS EN ISO 544 for further informationSee BS EN ISO 544 for further information

Covered electrode inspectionCovered electrode inspection

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Plastic foil sealed cardboard boxPlastic foil sealed cardboard box••rutile electrodesrutile electrodes••general purpose basic electrodesgeneral purpose basic electrodes

Tin canTin can••cellulosic electrodescellulosic electrodes

Vacuum sealed packVacuum sealed pack••extra low hydrogen electrodesextra low hydrogen electrodes

Courtesy of Lincoln ElectricCourtesy of Lincoln Electric

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MMA Welding ConsumablesMMA Welding ConsumablesCellulosicCellulosic electrodes:electrodes:

covering contains cellulose (organic material). covering contains cellulose (organic material). produce a gas shield high in hydrogenproduce a gas shield high in hydrogen raising the arc raising the arc voltage.voltage.Deep penetration / fusion characteristicsDeep penetration / fusion characteristics enables enables welding at high speed without risk of lack of fusion.welding at high speed without risk of lack of fusion.generates high level of fumes and H2generates high level of fumes and H2 cold cracking.cold cracking.Forms a thin slag layer with coarse weld profile.Forms a thin slag layer with coarse weld profile.not require baking or drying (excessive heat will not require baking or drying (excessive heat will damage electrode covering!). damage electrode covering!). Mainly used for stove pipe weldingMainly used for stove pipe weldinghydrogen content is 80hydrogen content is 80--90 ml/100 g of weld metal.90 ml/100 g of weld metal.

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MMA Welding ConsumablesMMA Welding ConsumablesCellulosic Electrodes Cellulosic Electrodes


•• weld beads have high hydrogenweld beads have high hydrogen

•• risk of cracking risk of cracking (need to keep joint hot during welding to allow (need to keep joint hot during welding to allow H to escape)H to escape)

•• not suitable for higher strength steels not suitable for higher strength steels -- cracking risk too cracking risk too high high (may not be allowed for Grades stronger than X70)(may not be allowed for Grades stronger than X70)

•• not suitable for very thick sections not suitable for very thick sections (may not be used on (may not be used on thicknesses > ~ 35mm)thicknesses > ~ 35mm)

•• not suitable when low temperature toughness is required not suitable when low temperature toughness is required (impact toughness satisfactory down to ~ (impact toughness satisfactory down to ~ --2020°°C)C)

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Deep penetration/fusionDeep penetration/fusion

Suitable for welding in all Suitable for welding in all positionspositions

Fast travel speeds Fast travel speeds

Large volumes of shielding Large volumes of shielding gasgas

Low controlLow control

DisadvantagesDisadvantages::

High in hydrogenHigh in hydrogen

High crack tendencyHigh crack tendency

Rough weld Rough weld appearanceappearance

High spatter contentsHigh spatter contents

Low deposition ratesLow deposition rates

Cellulosic ElectrodesCellulosic Electrodes

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MMA Welding ConsumablesMMA Welding ConsumablesRutile electrodes:Rutile electrodes:•• covering contains TiOcovering contains TiO22 slag former and arc stabiliser.slag former and arc stabiliser.•• easy to strike arc, less spatter, excellent for positional easy to strike arc, less spatter, excellent for positional

welding.welding.•• stable, easystable, easy--toto--use arcuse arc can operate in both DC and AC.can operate in both DC and AC.•• slag easy to detach, smooth profile.slag easy to detach, smooth profile.•• Reasonably good strength weld metal.Reasonably good strength weld metal.•• Used mainly on general purpose work.Used mainly on general purpose work.•• Low pressure pipework, support brackets.Low pressure pipework, support brackets.•• electrodes can be dried to lower H2 content but cannot be electrodes can be dried to lower H2 content but cannot be

bakedbaked as it willwill destroy the coating.•• hydrogen content is 25hydrogen content is 25--30 ml/100 g of weld metal.30 ml/100 g of weld metal.

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MMA Welding ConsumablesMMA Welding ConsumablesRutile electrodesRutile electrodes


•• they cannot be made with a low hydrogen contentthey cannot be made with a low hydrogen content

•• cannot be used on high strength steels or thick joints cannot be used on high strength steels or thick joints --cracking risk too highcracking risk too high

•• they do not give good toughness at low temperaturesthey do not give good toughness at low temperatures

•• these limitations mean that they are only suitable for general these limitations mean that they are only suitable for general engineering engineering -- low strength, thin steellow strength, thin steel

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Easy to useEasy to use

Low cost / controlLow cost / control

Smooth weld profilesSmooth weld profiles

Slag easily detachableSlag easily detachable

High deposition High deposition possible with the possible with the addition of iron powderaddition of iron powder


High in hydrogenHigh in hydrogen

High crack tendencyHigh crack tendency

Low strengthLow strength

Low toughness valuesLow toughness values

Rutile ElectrodesRutile Electrodes

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MMA Welding ConsumablesMMA Welding ConsumablesRutile VariantsRutile Variants

High Recovery Rutile Electrodes High Recovery Rutile Electrodes

Characteristics:Characteristics:•• coating is coating is ‘‘bulked outbulked out’’ with iron powderwith iron powder

•• iron powder gives the electrode iron powder gives the electrode ‘‘high recoveryhigh recovery’’

•• extra weld metal from the iron powder can mean that weld extra weld metal from the iron powder can mean that weld deposit from a single electrode can be as high as 180% of deposit from a single electrode can be as high as 180% of the core wire weightthe core wire weight

•• give good productivitygive good productivity

•• large weld beads with smooth profile can look very similar to large weld beads with smooth profile can look very similar to SAW weldsSAW welds

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MMA Welding ConsumablesMMA Welding ConsumablesHigh Recovery Rutile ElectrodesHigh Recovery Rutile Electrodes


•• Same as standard rutile electrodes with respect to hydrogen Same as standard rutile electrodes with respect to hydrogen controlcontrol

•• large weld beads produced cannot be used for alllarge weld beads produced cannot be used for all--positional positional weldingwelding

•• the very high recovery types usually limited to PA & PB the very high recovery types usually limited to PA & PB positionspositions

•• more moderate recovery may allow PC usemore moderate recovery may allow PC use

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MMA Welding ConsumablesMMA Welding ConsumablesBasic covering:Basic covering:•• Produce convex weld profile and difficult to detach slag.Produce convex weld profile and difficult to detach slag.

•• Very suitable for Very suitable for for for high pressure work, high pressure work, thick section steel thick section steel and for high strength steels.and for high strength steels.

•• Prior to use Prior to use electrodeselectrodes should be baked, typically 350should be baked, typically 350°°C for 2 C for 2 hour plus hour plus to reduce moisture to very low levels and achieve to reduce moisture to very low levels and achieve low hydrogen potential status.low hydrogen potential status.

•• Contain calcium fluoride and calcium carbonate compounds.Contain calcium fluoride and calcium carbonate compounds.

•• cannot be recannot be re--baked indefinitely!baked indefinitely!

•• low hydrogen potential gives low hydrogen potential gives weld metal very good weld metal very good toughness and YS.toughness and YS.

•• have the lowest level of hydrogen (less than 5 ml/100 g of have the lowest level of hydrogen (less than 5 ml/100 g of weld metal).weld metal).

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MMA Welding ConsumablesMMA Welding ConsumablesBasic ElectrodesBasic Electrodes

Disadvantages:Disadvantages:•• Careful control of baking and/or issuing of electrodes is Careful control of baking and/or issuing of electrodes is

essential to maintain low hydrogen status and avoid risk of essential to maintain low hydrogen status and avoid risk of crackingcracking

•• Typical baking temperature 350Typical baking temperature 350°°C for 1 to 2hours. C for 1 to 2hours.

•• Holding temperature 120 to 150Holding temperature 120 to 150°°C.C.

•• Issue in heated quivers typically 70Issue in heated quivers typically 70°°C.C.

•• Welders need to take more care / require greater skill.Welders need to take more care / require greater skill.

•• Weld profile usually more convex.Weld profile usually more convex.

•• DeslaggingDeslagging requires more effort than for other types.requires more effort than for other types.

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Basic ElectrodesBasic ElectrodesAdvantagesAdvantages

High toughness valuesHigh toughness values

Low hydrogen contentsLow hydrogen contents

Low crack tendencyLow crack tendency


High costHigh cost

High controlHigh control

High welder skill High welder skill requiredrequired

Convex weld profilesConvex weld profiles

Poor stop / start Poor stop / start propertiesproperties


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BS EN 499 MMA Covered ElectrodesBS EN 499 MMA Covered Electrodes

Covered ElectrodeCovered Electrode

ToughnessToughnessYield Strength N/mmYield Strength N/mm22

Chemical compositionChemical compositionFlux CoveringFlux CoveringWeld Metal RecoveryWeld Metal Recoveryand Current Typeand Current TypeWelding PositionWelding PositionHydrogen ContentHydrogen Content

EE 5050 33 2Ni2Ni BB 77 22 H10H10

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BS EN 499 MMA Covered ElectrodesBS EN 499 MMA Covered ElectrodesElectrodes classified as follows:Electrodes classified as follows:

E 35 E 35 -- Minimum yield strength 350 N/mmMinimum yield strength 350 N/mm22

Tensile strength 440 Tensile strength 440 -- 570 N/mm570 N/mm22









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AWS A5.1 Alloyed ElectrodesAWS A5.1 Alloyed Electrodes

Covered ElectrodeCovered ElectrodeTensile Strength (p.s.i)Tensile Strength (p.s.i)Welding PositionWelding PositionFlux CoveringFlux Covering

EE 6060 11 33

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AWS A5.5 Alloyed ElectrodesAWS A5.5 Alloyed Electrodes

Covered ElectrodeCovered ElectrodeTensile Strength (p.s.i)Tensile Strength (p.s.i)Welding PositionWelding PositionFlux CoveringFlux CoveringMoisture ControlMoisture ControlAlloy ContentAlloy Content

EE 7070 11 88 MM GG

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MMA Welding ConsumablesMMA Welding ConsumablesTYPES OF ELECTRODESTYPES OF ELECTRODES

(for C, C(for C, C--Mn Steels)Mn Steels)BS EN 499BS EN 499 AWS A5.1AWS A5.1

•• CellulosicCellulosic E XX X E XX X CC EXX1EXX10 0 EXX1EXX111

•• RutileRutile E XX X E XX X RR EXX1EXX12 2 EXX1EXX133

•• Rutile Heavy CoatedRutile Heavy Coated E XX X E XX X RRRR EXX2EXX244

•• BasicBasic E XX X E XX X BB EXX1EXX155EXX1EXX166EXX1EXX188

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Electrode efficiencyElectrode efficiency

7575--90% for usual electrodes90% for usual electrodes

up to 180% for iron powder electrodesup to 180% for iron powder electrodes

Mass of weld metal depositedMass of weld metal depositedElectrode Electrode EficiencyEficiency = =

Mass of core wire meltedMass of core wire melted

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Covered electrode treatmentCovered electrode treatment

Cellulosic Cellulosic electrodeselectrodes

Rutile Rutile electrodeselectrodes

Use straight from the Use straight from the box box -- No baking/drying!No baking/drying!

If necessary, dry up to If necessary, dry up to 120120°°CC-- No baking!No baking!

Vacuum Vacuum packed basic packed basic electrodeselectrodes

Use straight from the pack Use straight from the pack within 4 hours within 4 hours -- No No rebaking!rebaking!

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Covered electrode treatmentCovered electrode treatment

After baking, maintain in After baking, maintain in oven at 150oven at 150°°CC

Basic electrodesBasic electrodes Baking in oven 2 hours Baking in oven 2 hours at 350at 350°°C!C!

Use from quivers at Use from quivers at 7575°°CC

If not used within 4 If not used within 4 hours, return to oven hours, return to oven and rebake!and rebake!

WeldWeld

Limited number of Limited number of rebakes!rebakes!

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TIG ConsumablesTIG Consumables

Welding ConsumablesWelding Consumables

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TIG Welding ConsumablesTIG Welding ConsumablesWelding consumables for TIG:Welding consumables for TIG:

•• Filler wires, Shielding gases, tungsten electrodes (nonFiller wires, Shielding gases, tungsten electrodes (non--consumable). consumable).

•• Filler wires of different materials composition and Filler wires of different materials composition and variable diameters available in standard lengths, with variable diameters available in standard lengths, with applicable code stamped for identification applicable code stamped for identification

•• Steel Filler wires of very high quality, with copper Steel Filler wires of very high quality, with copper coating to resist corrosion. coating to resist corrosion.

•• shielding gases mainly Argon and Helium, usually of shielding gases mainly Argon and Helium, usually of highest purity (99.9%).highest purity (99.9%).

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TIG Welding ConsumablesTIG Welding Consumables

Welding rods:Welding rods:

••supplied in cardboard/plastic tubessupplied in cardboard/plastic tubes

••must be kept clean and free from oil and dustmust be kept clean and free from oil and dust

••might require degreasingmight require degreasing

Courtesy of Lincoln ElectricCourtesy of Lincoln Electric

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Fusible InsertsFusible Inserts


PrePre--placed filler materialplaced filler material

After WeldingAfter Welding

Other terms used include:Other terms used include:

EB inserts (Electric Boat Company)EB inserts (Electric Boat Company)

Consumable socket rings (CSR)Consumable socket rings (CSR)

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Fusible InsertsFusible InsertsConsumable inserts:Consumable inserts:

•• used for root runs on pipesused for root runs on pipes

•• used in conjunction with TIG weldingused in conjunction with TIG welding

•• available for carbon steel, Cravailable for carbon steel, Cr--Mo steel, austenitic stainless Mo steel, austenitic stainless steel, nickel and coppersteel, nickel and copper--nickel alloysnickel alloys

•• different shapes to suit applicationdifferent shapes to suit application

RadiusRadius

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Fusible InsertsFusible InsertsApplication of consumable insertsApplication of consumable inserts

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Shielding gases for TIG weldingShielding gases for TIG welding

ArgonArgonlow cost and greater availabilitylow cost and greater availability

heavier than air heavier than air -- lower flow rates than Heliumlower flow rates than Helium

low thermal conductivity low thermal conductivity -- wide top bead profilewide top bead profile

low ionisation potential low ionisation potential -- easier arc starting, better arc easier arc starting, better arc stability with AC, cleaning effectstability with AC, cleaning effect

for the same arc current produce less heat than for the same arc current produce less heat than helium helium -- reduced penetration, wider HAZreduced penetration, wider HAZ

to obtain the same arc arc power, argon requires a to obtain the same arc arc power, argon requires a higher current higher current -- increased undercutincreased undercut

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Helium Helium

costly and lower availability than Argoncostly and lower availability than Argon

lighter than air lighter than air -- requires a higher flow rate compared requires a higher flow rate compared with argon (2with argon (2--3 times)3 times)

higher ionisation potential higher ionisation potential -- poor arc stability with AC, poor arc stability with AC, less forgiving for manual weldingless forgiving for manual welding

for the same arc current produce more heat than for the same arc current produce more heat than argon argon -- increased penetration, welding of metals with increased penetration, welding of metals with high melting point or thermal conductivityhigh melting point or thermal conductivity

to obtain the same arc arc power, helium requires a to obtain the same arc arc power, helium requires a lower current lower current -- no undercutno undercut

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HydrogenHydrogen

not an inert gas not an inert gas -- not used as a primary shielding gasnot used as a primary shielding gas

increase the heat input increase the heat input -- faster travel speed and faster travel speed and increased penetrationincreased penetration

better wetting action better wetting action -- improved bead profileimproved bead profile

produce a cleaner weld bead surfaceproduce a cleaner weld bead surface

added to argon (up to 5%) added to argon (up to 5%) -- only for austenitic only for austenitic stainless steels and nickel alloysstainless steels and nickel alloys

flammable and explosiveflammable and explosive

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NitrogenNitrogen

not an inert gasnot an inert gas

high availability high availability -- cheapcheap

added to argon (up to 5%) added to argon (up to 5%) -- only for back purge for only for back purge for duplex stainless, austenitic stainless steels and copper duplex stainless, austenitic stainless steels and copper alloysalloys

not used for mild steels (age embritlement)not used for mild steels (age embritlement)

strictly prohibited in case of Ni and Ni alloys (porosity)strictly prohibited in case of Ni and Ni alloys (porosity)

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MIG / MAG ConsumablesMIG / MAG Consumables(Gases Covered previously)(Gases Covered previously)


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MIG/MAG Welding ConsumablesMIG/MAG Welding ConsumablesWelding consumables for MIG/MAGWelding consumables for MIG/MAG

•• Spools of Continuous electrode wires and shielding Spools of Continuous electrode wires and shielding gasesgases

•• variable spool size (1variable spool size (1--15Kg) and Wire diameter (0.615Kg) and Wire diameter (0.6--1.6mm) supplied in random or orderly layers1.6mm) supplied in random or orderly layers

•• Basic Selection of different materials and their alloys Basic Selection of different materials and their alloys as electrode wires.as electrode wires.

•• Some Steel Electrode wires copper coating purpose Some Steel Electrode wires copper coating purpose is corrosion resistance and electrical pickis corrosion resistance and electrical pick--upup

•• Gases can be pure COGases can be pure CO22, CO, CO22+Argon mixes and +Argon mixes and Argon+2%OArgon+2%O22 mixes (stainless steels).mixes (stainless steels).

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MIG/MAG Welding ConsumablesMIG/MAG Welding Consumables

Welding wires:Welding wires:

••carbon and low alloy wires may be copper coatedcarbon and low alloy wires may be copper coated• stainless steel wires are not coatedstainless steel wires are not coated

••wires must be kept clean and free from oil and dustwires must be kept clean and free from oil and dust••flux cored wires does not require baking or dryingflux cored wires does not require baking or drying

Courtesy of Lincoln ElectricCourtesy of Lincoln Electric Courtesy of ESAB ABCourtesy of ESAB AB

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Flux Core Wire ConsumablesFlux Core Wire Consumables(Not in training manual)(Not in training manual)


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Flux Core Wire ConsumablesFlux Core Wire Consumables

provide form stability to the wireserves as current transfer during welding

Functions of metallic sheath: Function of the filling powder:stabilise the arcadd alloy elementsproduce gaseous shieldproduce slagadd iron powder

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Types of cored wireTypes of cored wire

not sensitive to moisture not sensitive to moisture pickpick--upupcan be copper coated,can be copper coated,better current transferbetter current transferthick sheath, good form thick sheath, good form stability, 2 roll drive stability, 2 roll drive feeding possiblefeeding possibledifficult to manufacturedifficult to manufacture

good resistance to good resistance to moisture pickmoisture pick--upupcan be copper can be copper coatedcoatedthick sheaththick sheathdifficult to seal the difficult to seal the sheathsheath

Seamless Seamless cored wirecored wire

Butt joint Butt joint cored wirecored wire

Overlapping Overlapping cored wirecored wire

sensitive to sensitive to moisture pickmoisture pick--upupcannot be cannot be copper coatedcopper coatedthin sheaththin sheatheasy to easy to manufacturemanufacture

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Core elements and their functionCore elements and their functionAluminiumAluminium -- deoxidize & denitrifydeoxidize & denitrify

Calcium Calcium -- provide shielding & form slagprovide shielding & form slag

CarbonCarbon -- increase hardness & strengthincrease hardness & strength

ManganeseManganese -- deoxidize & increase strength and toughnessdeoxidize & increase strength and toughness

MolybdenumMolybdenum -- increase hardness & strengthincrease hardness & strength

NickelNickel -- improve hardness, strength, toughness & corrosion improve hardness, strength, toughness & corrosion resistanceresistance

Potassium Potassium -- stabilize the arc & form slagstabilize the arc & form slag

SiliconSilicon -- deoxidize & form slagdeoxidize & form slag

Sodium Sodium -- stabilize arc & form slagstabilize arc & form slag

TitaniumTitanium -- deoxidize, denitrify & form slagdeoxidize, denitrify & form slag

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SAW ConsumablesSAW Consumables


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SAW ConsumablesSAW ConsumablesWelding fluxes:Welding fluxes:

•• are granular mineral compounds mixed according to various are granular mineral compounds mixed according to various formulationsformulations

•• shield the molten weld pool from the atmosphereshield the molten weld pool from the atmosphere

•• clean the molten weld poolclean the molten weld pool

•• can modify the chemical composition of the weld metalcan modify the chemical composition of the weld metal

•• prevents rapid escape of heat from welding zoneprevents rapid escape of heat from welding zone

•• influence the shape of the weld bead (wetting action)influence the shape of the weld bead (wetting action)

•• can be fused, agglomerated or mixedcan be fused, agglomerated or mixed

•• must be kept warm and dry to avoid porositymust be kept warm and dry to avoid porosity

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•• Fused fluxes are normally not hygroscopic but particles can Fused fluxes are normally not hygroscopic but particles can hold surface moisture hold surface moisture so only dryingso only drying

•• Agglomerated fluxes contain chemically bonded water. SAgglomerated fluxes contain chemically bonded water. Similar imilar treatment as basic electrodestreatment as basic electrodes

•• If flux is too fine it will pack and not feed properly. It cannoIf flux is too fine it will pack and not feed properly. It cannot be t be recycled indefinitelyrecycled indefinitely

Welding flux:Welding flux:

•• might be fused or agglomeratedmight be fused or agglomerated

•• supplied in bagssupplied in bags

•• must be kept warm and drymust be kept warm and dry

•• handling and stacking requires carehandling and stacking requires careCourtesy of Lincoln ElectricCourtesy of Lincoln Electric

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Fused Flux:Fused Flux:Baked at high temperature, glossy, hard and black in colour, cannot add ferro-manganese, non moisture absorbent and tends to be of the acidic type

Fused FluxFused Flux

•• Flaky appearance Flaky appearance

•• Lower weld qualityLower weld quality

•• Low moisture intakeLow moisture intake

•• Low dust tendencyLow dust tendency

•• Good reGood re--cyclingcycling

•• Very smooth weld Very smooth weld profileprofile

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SAW ConsumablesSAW ConsumablesTYPES OF FLUXTYPES OF FLUX

FUSED (ACID TYPE)FUSED (ACID TYPE)•• name indicates method of manufacturename indicates method of manufacture•• minerals are fused (melted) and granules produced by minerals are fused (melted) and granules produced by

allowing to cool to a solid mass and then crushing or by allowing to cool to a solid mass and then crushing or by spraying the molten flux into waterspraying the molten flux into water

•• flux tends to be flux tends to be ‘‘glassglass--likelike’’ (high in Silica)(high in Silica)•• granules are hard and may appear shinygranules are hard and may appear shiny•• granules do not absorb moisturegranules do not absorb moisture•• granules do not tend break down into powder when being granules do not tend break down into powder when being

rere--circulatedcirculated•• are effectively a low hydrogen fluxare effectively a low hydrogen flux•• welds do not tend to give good toughness at low welds do not tend to give good toughness at low

temperaturestemperatures

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SAW ConsumablesSAW ConsumablesFused fluxes advantages:Fused fluxes advantages:

••good chemical homogeneitygood chemical homogeneity••easy removal of fines without affecting flux easy removal of fines without affecting flux compositioncomposition••normally not hygroscopic normally not hygroscopic �� easy storage and easy storage and handlinghandling••readily recycled without significant change in readily recycled without significant change in particle size or compositionparticle size or composition

Fused fluxes disadvantages:Fused fluxes disadvantages:••difficult to add deoxidizers and ferrodifficult to add deoxidizers and ferro--alloys (due to alloys (due to segregation or extremely high loss)segregation or extremely high loss)••high temperatures needed to melt ingredients limit high temperatures needed to melt ingredients limit the range of flux compositionsthe range of flux compositions

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Agglomerated Flux:Baked at a lower temperature, dull, irregularly shaped, friable,(easily crushed) can easily add alloying elements, moisture absorbent and tend to be of the basic type

SAW ConsumablesSAW ConsumablesAgglomerated FluxAgglomerated Flux

•• Granulated appearanceGranulated appearance

•• High weld quality High weld quality

•• Addition of alloys Addition of alloys

•• Lower consumptionLower consumption

•• Easy slag removalEasy slag removal

•• Smooth weld profileSmooth weld profile

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SAW ConsumablesSAW ConsumablesAgglomerated fluxes advantages:Agglomerated fluxes advantages:

•• easy addition of deoxidizers and alloying elementseasy addition of deoxidizers and alloying elements

•• usable with thicker layer of flux when weldingusable with thicker layer of flux when welding

•• colour identificationcolour identification

Agglomerated fluxes disadvantages:Agglomerated fluxes disadvantages:

•• tendency to absorb moisturetendency to absorb moisture

•• possible gas evolution from the molten slag leading to possible gas evolution from the molten slag leading to porosityporosity

•• possible change in flux composition due to segregation or possible change in flux composition due to segregation or removal of fine mesh particlesremoval of fine mesh particles

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SAW ConsumablesSAW ConsumablesTYPES OF FLUXTYPES OF FLUX

AGGLOMERATED (BASIC TYPE)AGGLOMERATED (BASIC TYPE)

•• name indicates method of manufacturename indicates method of manufacture

•• basic minerals are used in powder form and are mixed with a basic minerals are used in powder form and are mixed with a binder to form individual granulesbinder to form individual granules

•• granules are soft and easily crushed to powdergranules are soft and easily crushed to powder

•• granules will absorb moisture and it is necessary to protect granules will absorb moisture and it is necessary to protect the flux from moisture pickthe flux from moisture pick--up up -- usually by holding in a usually by holding in a heated siloheated silo

•• granules tend to break down into powder when being regranules tend to break down into powder when being re--circulatedcirculated

•• are a low hydrogen flux are a low hydrogen flux -- if correctly controlledif correctly controlled

•• welds give good toughness at low temperatureswelds give good toughness at low temperatures

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Mixed fluxes advantages:Mixed fluxes advantages:••several commercial fluxes may be mixed for highly several commercial fluxes may be mixed for highly critical or proprietary welding operationscritical or proprietary welding operations

Mixed fluxes disadvantages:Mixed fluxes disadvantages:••segregation of the combined fluxes during segregation of the combined fluxes during shipment, storage and handlingshipment, storage and handling••segregation occurring in the feeding and recovery segregation occurring in the feeding and recovery systems during weldingsystems during welding••inconsistency in the combined flux from mix to mixinconsistency in the combined flux from mix to mix

Mixed fluxesMixed fluxes -- two or more fused or bonded fluxes are two or more fused or bonded fluxes are mixed in any ratio necessary to yield the desired mixed in any ratio necessary to yield the desired resultsresults

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SAW filler materialSAW filler material

Welding wires can be used to weld:Welding wires can be used to weld:••carbon steelscarbon steels

••low alloy steelslow alloy steels

••creep resisting steelscreep resisting steels

••stainless steelsstainless steels

••nickelnickel--base alloysbase alloys

••special alloys for surfacing applicationsspecial alloys for surfacing applicationsWelding wires can be:Welding wires can be:

••solid wiressolid wires

••metalmetal--cored wirescored wires

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SAW filler materialSAW filler materialWelding wires:Welding wires:••carbon and low alloy wires are copper coatedcarbon and low alloy wires are copper coated

••wires must be kept clean and free from oil and dustwires must be kept clean and free from oil and dust

••stainless steel wires are not coatedstainless steel wires are not coated

Courtesy of Lincoln ElectricCourtesy of Lincoln Electric Courtesy of Lincoln ElectricCourtesy of Lincoln Electric

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SAW filler materialSAW filler materialCopper coating functions:Copper coating functions:

••to assure a good electric contact between wire to assure a good electric contact between wire and contact tipand contact tip

••to assure a smooth feed of the wire through the to assure a smooth feed of the wire through the guide tube, feed rolls and contact tip (decrease guide tube, feed rolls and contact tip (decrease contact tube wear)contact tube wear)

••to provide protection against corrosionto provide protection against corrosion

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Non Destructive TestingNon Destructive TestingSection 15Section 15

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NonNon--Destructive TestingDestructive TestingA welding inspector should have a working knowledge of A welding inspector should have a working knowledge of NDT methods and their applications, advantages and NDT methods and their applications, advantages and disadvantages.disadvantages.

Four basic NDT methodsFour basic NDT methods

•• Radiographic inspection (RT)Radiographic inspection (RT)

•• Ultrasonic inspection (UT)Ultrasonic inspection (UT)

•• Magnetic particle inspection (MT)Magnetic particle inspection (MT)

•• Dye Dye penetrantpenetrant inspection (PT)inspection (PT)

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NonNon--Destructive TestingDestructive TestingSurface Crack DetectionSurface Crack Detection

•• Liquid Penetrant (PT or DyeLiquid Penetrant (PT or Dye--Penetrant)Penetrant)

•• Magnetic Particle Inspection (MT or MPI)Magnetic Particle Inspection (MT or MPI)

Volumetric & Planar InspectionVolumetric & Planar Inspection

•• Ultrasonics (UT)Ultrasonics (UT)

•• Radiography (RT)Radiography (RT)

Each technique has advantages & disadvantages with respect Each technique has advantages & disadvantages with respect to: to:

•• Technical Capability and CostTechnical Capability and Cost

Note:Note: The choice of NDT techniques is based on consideration The choice of NDT techniques is based on consideration of these advantages and disadvantagesof these advantages and disadvantages

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Radiographic Testing (RT)Radiographic Testing (RT)

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The principles of radiographyThe principles of radiography

•• X or Gamma radiation is imposed upon a test objectX or Gamma radiation is imposed upon a test object

•• Radiation is transmitted to varying degrees Radiation is transmitted to varying degrees dependant upon the density of the material through dependant upon the density of the material through which it is travellingwhich it is travelling

•• Thinner areas and materials of a less density show as Thinner areas and materials of a less density show as darker areas on the radiographdarker areas on the radiograph

•• Thicker areas and materials of a greater density show Thicker areas and materials of a greater density show as lighter areas on a radiographas lighter areas on a radiograph

•• Applicable to metals,nonApplicable to metals,non--metals and composites metals and composites

Radiographic TestingRadiographic Testing

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X X –– RaysRaysElectrically generatedElectrically generated

Gamma RaysGamma RaysGenerated by the decay Generated by the decay

of unstable atoms of unstable atoms


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SourceSource

Radiation beamRadiation beam Image quality indicatorImage quality indicator

Radiographic film with latent image after exposureRadiographic film with latent image after exposure

10fe1610fe16

Test specimenTest specimen

10fe1610fe16


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Radiographic TestingRadiographic TestingDensityDensity -- relates to the degree of darknessrelates to the degree of darkness

ContrastContrast -- relates to the degree of differencerelates to the degree of difference

Definition Definition -- relates to the degree of sharpnessrelates to the degree of sharpness

SensitivitySensitivity -- relates to the overall quality of the radiographrelates to the overall quality of the radiograph

Densitometer

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7FE127FE12

Step / Hole type IQIStep / Hole type IQI Wire type IQIWire type IQI

Radiographic SensitivityRadiographic Sensitivity

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Wire Type IQIWire Type IQI

Step/Hole Type IQIStep/Hole Type IQI

Radiographic SensitivityRadiographic Sensitivity

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Single Wall Single Image (SWSI)Single Wall Single Image (SWSI)

•• film inside, source outsidefilm inside, source outside

Single Wall Single Image (SWSI)Single Wall Single Image (SWSI) panoramicpanoramic

•• film outside, source inside (internal exposure)film outside, source inside (internal exposure)

Double Wall Single Image (DWSI)Double Wall Single Image (DWSI)

•• film outside, source outside (external exposure)film outside, source outside (external exposure)

Double Wall Double Image (DWDI)Double Wall Double Image (DWDI)

•• film outside, source outside (elliptical exposure)film outside, source outside (elliptical exposure)

Radiographic TechniquesRadiographic Techniques

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IQIIQI’’ss should be placed source sideshould be placed source side

FilmFilm

FilmFilm

Single Wall Single Image (SWSI)Single Wall Single Image (SWSI)

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•• IQIIQI’’ss are placed on the film sideare placed on the film side

•• Source inside film outside (single exposure)Source inside film outside (single exposure)

FilmFilm

Single Wall Single Image PanoramicSingle Wall Single Image Panoramic

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•• IQIIQI’’ss are placed on the film sideare placed on the film side

•• Source outside film outside (multiple exposure)Source outside film outside (multiple exposure)

•• This technique is intended for pipe diameters This technique is intended for pipe diameters over 100mmover 100mm

FilmFilm


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RadiographRadiograph

•• IdentificationIdentification

IDID MR11MR11

•• Unique identificationUnique identificationEN W10EN W10

•• IQI placingIQI placing

AA BB•• Pitch marks indicating Pitch marks indicating readable film length readable film length


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RadiographRadiograph


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FilmFilm

•• IQIIQI’’ss are placed on the source or film sideare placed on the source or film side

•• Source outside film outside (multiple exposure)Source outside film outside (multiple exposure)

•• A minimum of two exposuresA minimum of two exposures

•• This technique is intended for pipe diameters less than 100mmThis technique is intended for pipe diameters less than 100mm


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Shot A RadiographShot A Radiograph

•• IdentificationIdentification

•• Unique identificationUnique identification

ID MR12

EN W10

•• IQI placingIQI placing

1 2•• Pitch marks indicating Pitch marks indicating readable film length readable film length

4 3


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Elliptical RadiographElliptical Radiograph

11 22

44 33


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RadiographyRadiographyPENETRATING POWERPENETRATING POWER

Question:Question:

What determines the penetrating power of an XWhat determines the penetrating power of an X--ray ?ray ?

••the kilothe kilo--voltage applied voltage applied (between anode & cathode)(between anode & cathode)

Question: Question:

What determines the penetrating power ofWhat determines the penetrating power of a gamma ray ?a gamma ray ?

••the type of isotope the type of isotope (the wavelength of the gamma rays)(the wavelength of the gamma rays)

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RadiographyRadiographyGAMMA SOURCESGAMMA SOURCES

IsotopeIsotope Typical Thickness RangeTypical Thickness Range

•• Iridium 192Iridium 192 10 to 50 mm 10 to 50 mm (mostly used)(mostly used)

•• Cobalt 60Cobalt 60 > 50 mm> 50 mm

•• YtterbiumYtterbium < 10 mm< 10 mm

•• ThuliumThulium < 10 mm< 10 mm

•• CesiumCesium < 10 mm< 10 mm

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•• Permanent recordPermanent record

•• Little surface preparationLittle surface preparation

•• Defect identificationDefect identification

•• No material type limitationNo material type limitation

•• Not so reliant upon operator Not so reliant upon operator skillskill

•• Thin materialsThin materials


•• Expensive consumablesExpensive consumables

•• Bulky equipmentBulky equipment

•• Harmful radiationHarmful radiation

•• Defect require significant Defect require significant depth in relation to the depth in relation to the radiation beam (not good radiation beam (not good for planar defects)for planar defects)

•• Slow resultsSlow results

•• Very little indication of Very little indication of depthsdepths

•• Access to both sides Access to both sides requiredrequired


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Radiographic TestingRadiographic TestingComparison with Ultrasonic ExaminationComparison with Ultrasonic Examination

ADVANTAGESADVANTAGES

good for nongood for non--planar defectsplanar defects

good for thin sectionsgood for thin sections

gives permanent recordgives permanent record

easier for 2nd party interpretationeasier for 2nd party interpretation

can use on all material typescan use on all material types

high productivityhigh productivity

direct image of imperfectionsdirect image of imperfections

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Radiographic TestingRadiographic TestingComparison with Ultrasonic ExaminationComparison with Ultrasonic Examination

DISADVANTAGESDISADVANTAGES

health & safety hazardhealth & safety hazard

not good for thick sectionsnot good for thick sections

high capital and relatively high running costshigh capital and relatively high running costs

not good for planar defectsnot good for planar defects

XX--ray sets not very portableray sets not very portable

requires access to both sides of weldrequires access to both sides of weld

frequent replacement of gammafrequent replacement of gamma source needed (half life)source needed (half life)

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Ultrasonic Testing (UT)Ultrasonic Testing (UT)

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Main Features:Main Features:•• Surface and subSurface and sub--surface detectionsurface detection•• This detection method uses high frequency sound waves, This detection method uses high frequency sound waves,

typically above 2MHz to pass through a materialtypically above 2MHz to pass through a material•• A probe is used which contains a A probe is used which contains a piezopiezo electric crystal to electric crystal to

transmit and receive ultrasonic pulses and display the transmit and receive ultrasonic pulses and display the signals on a cathode ray tube or digital displaysignals on a cathode ray tube or digital display

•• The actual display relates to the time taken for the The actual display relates to the time taken for the ultrasonic pulses to travel the distance to the interface and ultrasonic pulses to travel the distance to the interface and backback

•• An interface could be the back of a plate material or a defectAn interface could be the back of a plate material or a defect•• For ultrasound to enter a material a couplant must be For ultrasound to enter a material a couplant must be

introduced between the probe and specimenintroduced between the probe and specimen

Ultrasonic TestingUltrasonic Testing

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DigitalDigitalUT Set,UT Set,

Pulse echo Pulse echo signals signals A scan A scan DisplayDisplay

Compression probeCompression probe checking the material checking the material ThicknessThickness


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defectdefect

00 1010 2020 3030 4040 5050

defect defect echoecho

Back wall Back wall echoecho

CRT DisplayCRT DisplayCompression ProbeCompression Probe

Material Material ThkThk

initial pulseinitial pulse


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Angle ProbeAngle Probe

UT SetUT SetA Scan A Scan DisplayDisplay


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initial pulse

defect echodefectdefect

defect

0 10 20 30 40 50

CRT Display

0 10 20 30 40 50

initial pulse

defect echo

CRT Display

½ Skip

Full Skip


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Rapid resultsRapid results

Both surface and Both surface and

subsub--surface detectionsurface detection

SafeSafe

Capable of measuring the Capable of measuring the depth of defectsdepth of defects

May be battery poweredMay be battery powered

PortablePortable


Trained and skilled operator Trained and skilled operator requiredrequired

Requires high operator skillRequires high operator skill

Good surface finish requiredGood surface finish required

Defect identificationDefect identification

CouplantCouplant may contaminate may contaminate

No permanent recordNo permanent record

Calibration RequiredCalibration Required

Ferritic Material (Mostly)Ferritic Material (Mostly)


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Ultrasonic TestingUltrasonic TestingComparison with RadiographyComparison with Radiography


••good for planar defectsgood for planar defects

••good for thick sectionsgood for thick sections

••instant resultsinstant results

••can use on complex jointscan use on complex joints

••can automatecan automate

••very portablevery portable

••no safety problems no safety problems ((‘‘parallelparallel’’ working is possible) working is possible)

••low capital & running costslow capital & running costs

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Ultrasonic TestingUltrasonic TestingComparison with RadiographyComparison with Radiography


no permanent record no permanent record (with standard equipment)(with standard equipment)

not suitable for very thin joints <8mmnot suitable for very thin joints <8mm

reliant on operator interpretationreliant on operator interpretation

not good for sizing Porositynot good for sizing Porosity

good/smooth surface profile needed good/smooth surface profile needed

not suitable for coarse grain materials (e.g., castings)not suitable for coarse grain materials (e.g., castings)

Ferritic Materials Ferritic Materials (with standard equipment)(with standard equipment)

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Magnetic Particle testing (MT)Magnetic Particle testing (MT)

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Magnetic Particle TestingMagnetic Particle TestingMain features:Main features:

Surface and slight subSurface and slight sub--surface detectionsurface detectionRelies on magnetization of component being testedRelies on magnetization of component being testedOnly FerroOnly Ferro--magnetic materials can be testedmagnetic materials can be testedA magnetic field is introduced into a specimen being A magnetic field is introduced into a specimen being testedtestedMethods of applying a magnetic field, yoke, permanent Methods of applying a magnetic field, yoke, permanent magnet, prods and flexible cables.magnet, prods and flexible cables.Fine particles of iron powder are applied to the test areaFine particles of iron powder are applied to the test areaAny defect which interrupts the magnetic field, will create Any defect which interrupts the magnetic field, will create a leakage field, which attracts the particlesa leakage field, which attracts the particlesAny defect will show up as either a dark indication or in Any defect will show up as either a dark indication or in the case of fluorescent particles under UVthe case of fluorescent particles under UV--A light a A light a green/yellow indication green/yellow indication

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Electro-magnet (yoke) DC or AC

Prods DC or AC

Collection of ink Collection of ink particles due to particles due to leakage fieldleakage field

Magnetic Particle TestingMagnetic Particle Testing

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A crack like A crack like indicationindication


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Alternatively to contrast inks, fluorescent inks may be used Alternatively to contrast inks, fluorescent inks may be used for greater sensitivity. These inks require a UVfor greater sensitivity. These inks require a UV--A light source A light source and a darkened viewing area to inspect the componentand a darkened viewing area to inspect the component


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Typical sequence of operations to inspect a weldTypical sequence of operations to inspect a weld

•• Clean area to be testedClean area to be tested

•• Apply contrast paintApply contrast paint

•• Apply magnetisism to the componentApply magnetisism to the component

•• Apply ferroApply ferro--magnetic ink to the component duringmagnetic ink to the component duringmagnatisingmagnatising

•• Iterpret the test areaIterpret the test area

•• Post clean and dePost clean and de--magnatise if requiredmagnatise if required


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•• Simple to useSimple to use

•• InexpensiveInexpensive

•• Rapid resultsRapid results

•• Little surface preparation Little surface preparation requiredrequired

•• Possible to inspect through Possible to inspect through thin coatingsthin coatings


•• Surface or slight subSurface or slight sub--surface surface detection onlydetection only

•• Magnetic materials onlyMagnetic materials only

•• No indication of defects No indication of defects depthsdepths

•• Only suitable for linear Only suitable for linear defectsdefects

•• Detection is required in two Detection is required in two directionsdirections


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Magnetic Particle TestingMagnetic Particle TestingComparison with Penetrant TestingComparison with Penetrant Testing


•• much quicker than PTmuch quicker than PT

•• instant resultsinstant results

•• can detect nearcan detect near--surface imperfections surface imperfections (by current flow (by current flow technique)technique)

•• less surface preparation neededless surface preparation needed


•• only suitable for ferromagnetic materialsonly suitable for ferromagnetic materials

•• electrical power for most techniques electrical power for most techniques

•• may need to demay need to de--magnetise (machine components)magnetise (machine components)

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Penetrant Testing (PT)Penetrant Testing (PT)

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Penetrant TestingPenetrant TestingMain features:Main features:

Detection of surface breaking defects only.Detection of surface breaking defects only.

This test method uses the forces of capillary action This test method uses the forces of capillary action

Applicable on any material type, as long they are non Applicable on any material type, as long they are non porous. porous.

PenetrantsPenetrants are available in many different types:are available in many different types:

•• Water washable contrastWater washable contrast

•• Solvent removable contrastSolvent removable contrast

•• Water washable fluorescentWater washable fluorescent

•• Solvent removable fluorescentSolvent removable fluorescent

•• PostPost--emulsifiableemulsifiable fluorescent fluorescent

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Step 1. PreStep 1. Pre--CleaningCleaning

Ensure surface is very Clean normally with the use of a solventEnsure surface is very Clean normally with the use of a solvent

Penetrant TestingPenetrant Testing

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Step 2. Apply penetrantStep 2. Apply penetrantAfter the application, the penetrant is normally left on the After the application, the penetrant is normally left on the components surface for approximately 15components surface for approximately 15--20 minutes (dwell 20 minutes (dwell time).time).The penetrant enters any defects that may be present by The penetrant enters any defects that may be present by capillary action.capillary action.


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Step 3. Clean off penetrantStep 3. Clean off penetrantthe penetrant is removedthe penetrant is removed after sufficient penetration time (dwell after sufficient penetration time (dwell time).time).Care must be taken not to wash any penetrant out off any Care must be taken not to wash any penetrant out off any defects presentdefects present


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Step 3. Apply developerStep 3. Apply developerAfter the penetrant has be cleaned sufficiently, a thin layer ofAfter the penetrant has be cleaned sufficiently, a thin layer ofdeveloper is applied. developer is applied. The developer acts as a contrast against the penetrant and The developer acts as a contrast against the penetrant and allows for reverse capillary action to take place.allows for reverse capillary action to take place.


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Step 4. Inspection / development timeStep 4. Inspection / development timeInspection should take place immediately after the developer Inspection should take place immediately after the developer has been applied.has been applied.any defects present will show as a bleed out during any defects present will show as a bleed out during development time. development time. After full inspection has been carried out post cleaning is After full inspection has been carried out post cleaning is generally required.generally required.


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ColourColour contrast Penetrantcontrast Penetrant

Fluorescent PenetrantFluorescent Penetrant Bleed out viewed Bleed out viewed under a UVunder a UV--A light A light sourcesource

Bleed out viewed Bleed out viewed under white light under white light


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AdvantagesAdvantagesSimple to useSimple to useInexpensiveInexpensiveQuick resultsQuick resultsCan be used on any nonCan be used on any non--porous materialporous materialPortabilityPortabilityLow operator skill requiredLow operator skill required

DisadvantagesDisadvantagesSurface breaking defect Surface breaking defect onlyonlylittle indication of depthslittle indication of depthsPenetrant may Penetrant may contaminate componentcontaminate componentSurface preparation criticalSurface preparation criticalPost cleaning requiredPost cleaning requiredPotentially hazardous Potentially hazardous chemicalschemicalsCan not test unlimited Can not test unlimited timestimesTemperature dependant Temperature dependant

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Penetrant TestingPenetrant TestingComparison with Magnetic Particle InspectionComparison with Magnetic Particle Inspection


••easy to interpret resultseasy to interpret results

••no power requirementsno power requirements

••relatively little training requiredrelatively little training required

••can use on all materialscan use on all materials


••good surface finish neededgood surface finish needed

••relatively slowrelatively slow

••chemicals chemicals -- health & safety issue health & safety issue

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Weld RepairsWeld RepairsSection 16Section 16

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Weld RepairsWeld RepairsWeld repairs can be divided into 2 specific Weld repairs can be divided into 2 specific areas:areas:

Production repairsProduction repairs

In service repairsIn service repairs

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A weld repair can be a relatively straight forward A weld repair can be a relatively straight forward activity, but in many instances it is quite complex, and activity, but in many instances it is quite complex, and various engineering disciplines may need to be involved various engineering disciplines may need to be involved to ensure a successful outcome.to ensure a successful outcome.

•• Analysis of the defect types may be carried out by Analysis of the defect types may be carried out by the Q/C department to discover the likely reason for the Q/C department to discover the likely reason for their occurrence, (Material/Process or Skill related).their occurrence, (Material/Process or Skill related).

In general terms, a welding repair involves In general terms, a welding repair involves What!What!

Weld RepairsWeld Repairs

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Weld RepairsWeld RepairsA weld repair may be used to improve weld profiles or A weld repair may be used to improve weld profiles or extensive metal removal:extensive metal removal:

•• Repairs to fabrication defects are generally easier Repairs to fabrication defects are generally easier than repairs to service failures because the repair than repairs to service failures because the repair procedure may be followedprocedure may be followed

•• The main problem with repairing a weld is the The main problem with repairing a weld is the maintenance of mechanical propertiesmaintenance of mechanical properties

•• During the inspection of the removed area prior to During the inspection of the removed area prior to welding the inspector must ensure that the defects welding the inspector must ensure that the defects have been totally removed and the original joint have been totally removed and the original joint profile has been maintained as close as possible profile has been maintained as close as possible

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Weld RepairsWeld RepairsIn the event of repair, it is required:In the event of repair, it is required:

Authorization and procedure for repairAuthorization and procedure for repair

Removal of material and preparation for repairRemoval of material and preparation for repair

Monitoring of repair WeldMonitoring of repair Weld

Testing of repair Testing of repair -- visual and NDTvisual and NDT

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There are a number of key factors that need to be There are a number of key factors that need to be considered before undertaking any repair:considered before undertaking any repair:

The most important The most important -- is it financially worthwhile? is it financially worthwhile?

Can structural integrity be achieved if the item is repaired?Can structural integrity be achieved if the item is repaired?

Are there any alternatives to welding?Are there any alternatives to welding?

What caused the defect and is it likely to happen again?What caused the defect and is it likely to happen again?

How is the defect to be removed and what welding process How is the defect to be removed and what welding process is to be used?is to be used?

What NDE is required to ensure complete removal of the What NDE is required to ensure complete removal of the defect?defect?

Will the welding procedures require approval/reWill the welding procedures require approval/re--approval?approval?


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Weld RepairsWeld RepairsCleaning the repair area, (removal of paint, grease, etc)Cleaning the repair area, (removal of paint, grease, etc)

A detailed assessment to find out the extremity of the A detailed assessment to find out the extremity of the defect. This may involve the use of a surface or sub surface defect. This may involve the use of a surface or sub surface NDE method.NDE method.

Once established the excavation site must be clearly Once established the excavation site must be clearly identified and marked out.identified and marked out.

An excavation procedure may be required (method used An excavation procedure may be required (method used i.e. grinding, arci.e. grinding, arc--air gouging, preheat requirements etc).air gouging, preheat requirements etc).

NDE should be used to locate the defect and confirm its NDE should be used to locate the defect and confirm its removal.removal.

A welding repair procedure/method statement with the A welding repair procedure/method statement with the appropriate welding process, consumable, technique, appropriate welding process, consumable, technique, controlled heat input and interpass temperatures etc will controlled heat input and interpass temperatures etc will need to be approved.need to be approved.

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Use of approved welders.Use of approved welders.

Dressing the weld and final visual.Dressing the weld and final visual.

A NDT procedure/technique prepared and carried out to A NDT procedure/technique prepared and carried out to ensure that the defect has been successfully removed and ensure that the defect has been successfully removed and repaired.repaired.

Any post repair heat treatment requirements.Any post repair heat treatment requirements.

Final NDT procedure/technique prepared and carried out Final NDT procedure/technique prepared and carried out after heat treatment requirements.after heat treatment requirements.

Applying protective treatments (painting etc as required).Applying protective treatments (painting etc as required).

(*Appropriate(*Appropriate’’ means suitable for the alloys being repaired means suitable for the alloys being repaired and may not apply in specific situations)and may not apply in specific situations)


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What will be the effect of welding distortion and What will be the effect of welding distortion and residual stress?residual stress?

Will heat treatment be required?Will heat treatment be required?

What NDE is required and how can acceptability of the What NDE is required and how can acceptability of the repair be demonstrated?repair be demonstrated?

Will approval of the repair be required Will approval of the repair be required –– if yes, how if yes, how and by whom? and by whom?


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Production Weld RepairsProduction Weld RepairsBefore the repair can commence, a number of elements need Before the repair can commence, a number of elements need to be fulfilled:to be fulfilled:

If the defect is surface breaking and has occurred at the fusionIf the defect is surface breaking and has occurred at the fusionface the problem could be cracking or lack of sidewall fusion. face the problem could be cracking or lack of sidewall fusion.

If the defect is found to be cracking the cause may be If the defect is found to be cracking the cause may be associated with the material or the welding procedureassociated with the material or the welding procedure

If the defect is lack of sidewall fusion this can be apportionedIf the defect is lack of sidewall fusion this can be apportionedto the lack of skill of the welder.to the lack of skill of the welder.

In this particular case as the defect is open to the surface, MPIn this particular case as the defect is open to the surface, MPI I or DYEor DYE--PEN may be used to gauge the length of the defect and PEN may be used to gauge the length of the defect and U/T inspection used to gauge the depth.U/T inspection used to gauge the depth.

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Weld RepairsWeld RepairsThe specification or procedure will govern how the The specification or procedure will govern how the defective areas are to be removed. The method of defective areas are to be removed. The method of removal may be:removal may be:

•• GrindingGrinding

•• ChippingChipping

•• MachiningMachining

•• FilingFiling

•• OxyOxy--Gas gougingGas gouging

•• Arc air gougingArc air gouging

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Defect ExcavationDefect Excavation

ArcArc--air gougingair gouging

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ArcArc--air gouging featuresair gouging features•• Operate ONLY on DCEPOperate ONLY on DCEP

•• Special gougingSpecial gouging copper copper coated carbon electrodecoated carbon electrode

•• Can be used on carbon Can be used on carbon and low alloy steels, and low alloy steels, austenitic stainless steels austenitic stainless steels and nonand non--ferrous materialsferrous materials

•• Requires CLEAN/DRY Requires CLEAN/DRY compressed air supplycompressed air supply

•• Provides fast rate of metal removalProvides fast rate of metal removal•• Can remove complex shape defectsCan remove complex shape defects•• After gouging, grinding of carbured layer is mandatoryAfter gouging, grinding of carbured layer is mandatory•• Gouging doesnGouging doesn’’t require a qualified welder!t require a qualified welder!

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Production RepairsProduction Repairsare usually identified during production are usually identified during production inspectioninspectionevaluation of the reports is usually carried out evaluation of the reports is usually carried out by the Welding Inspector, or NDT operatorby the Welding Inspector, or NDT operator

Production Weld RepairsProduction Weld Repairs

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Production Weld RepairsProduction Weld Repairs

Plan View of defect

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Production Weld RepairsProduction Weld RepairsSide View of defect excavation

D

W

Side View of repair welding

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In Service Weld RepairsIn Service Weld RepairsIn service repairsIn service repairs

Can be of a very complex nature, as the component is Can be of a very complex nature, as the component is very likely to be in a different welding position and very likely to be in a different welding position and condition than it was during productioncondition than it was during production

It may also have been in contact with toxic, or It may also have been in contact with toxic, or combustible fluids hence a permit to work will need to combustible fluids hence a permit to work will need to be sought prior to any work being carried outbe sought prior to any work being carried out

The repair welding procedure may look very different The repair welding procedure may look very different to the original production procedure due to changes in to the original production procedure due to changes in these elements. these elements.

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In Service Weld RepairsIn Service Weld RepairsOther factors to be taken into consideration:Other factors to be taken into consideration:

Effect of heat on any surrounding areas of the Effect of heat on any surrounding areas of the component i.e. electrical components, or materials that component i.e. electrical components, or materials that may become damaged by the repair procedure. may become damaged by the repair procedure.

This may also include difficulty in carrying out any This may also include difficulty in carrying out any required pre or post welding heat treatments and a required pre or post welding heat treatments and a possible restriction of access to the area to be possible restriction of access to the area to be repaired. repaired.

For large fabrications it is likely that the repair must For large fabrications it is likely that the repair must also take place on site and without a shut down of also take place on site and without a shut down of operations, which may bring other elements that need operations, which may bring other elements that need to be considered. to be considered.

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Is welding the best method of repair?Is welding the best method of repair?

Is the repair really like earlier repairs?Is the repair really like earlier repairs?

What is the composition and weldability of the base metal?What is the composition and weldability of the base metal?

What strength is required from the repair?What strength is required from the repair?

Can preheat be tolerated?Can preheat be tolerated?

Can softening or hardening of the HAZ be tolerated?Can softening or hardening of the HAZ be tolerated?

Is PWHT necessary and practicable?Is PWHT necessary and practicable?

Will the fatigue resistance of the repair be adequate?Will the fatigue resistance of the repair be adequate?

Will the repair resist its environment?Will the repair resist its environment?

Can the repair be inspected and tested?Can the repair be inspected and tested?


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Weld repair related problemsWeld repair related problemsheat from welding may affect dimensional stability heat from welding may affect dimensional stability and/or mechanical properties of repaired assemblyand/or mechanical properties of repaired assembly

due to heat from welding, YS goes down,due to heat from welding, YS goes down, danger of danger of collapsecollapse

filler materials used on dissimilar welds may lead to filler materials used on dissimilar welds may lead to galvanic corrosiongalvanic corrosion

local preheat may induce residual stresseslocal preheat may induce residual stresses

cost of weld metal deposited during a weld joint cost of weld metal deposited during a weld joint repair can reach up to 10 times the original weld repair can reach up to 10 times the original weld metal cost! metal cost!

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Residual Stress & DistortionResidual Stress & DistortionSection 17Section 17

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Residual stressResidual stressResidual stresses are undesirable because:Residual stresses are undesirable because:

they lead to distortionthey lead to distortionthey affect dimensional stability of the they affect dimensional stability of the welded assemblywelded assemblythey enhance the risk of brittle fracturethey enhance the risk of brittle fracturethey can facilitate certain types of they can facilitate certain types of corrosioncorrosion

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The heating and subsequent cooling from welding produces The heating and subsequent cooling from welding produces expansion and contractions which affect the weld metal and expansion and contractions which affect the weld metal and adjacent material.adjacent material.

If this contraction is prevented or inhibited residual stress wiIf this contraction is prevented or inhibited residual stress will ll develop.develop.

The tendency to develop residual stresses increases when the The tendency to develop residual stresses increases when the heating and cooling is localised. heating and cooling is localised.

Residual stresses are very difficult to measure with any real Residual stresses are very difficult to measure with any real accuracy.accuracy.

Residual stresses are self balancing internal forces and not Residual stresses are self balancing internal forces and not stresses induced whilst applying external loadstresses induced whilst applying external load

Stresses are more concentrated at the surface of the Stresses are more concentrated at the surface of the component.component.

The removal of residual stresses is termed stress relieving.The removal of residual stresses is termed stress relieving.

Residual StressesResidual Stresses

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Normal StressNormal Stress

Stress arising from a force perpendicular to Stress arising from a force perpendicular to the the crosscross sectional areasectional area

CompressionCompression

TensionTension

StressesStresses

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Shear StressShear Stress

Stress arising from forces which are parallel to, and Stress arising from forces which are parallel to, and lie lie in in the plane of the cross sectional the plane of the cross sectional area.area.

Shear StressShear Stress

StressesStresses

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Hoop StressHoop Stress

Internal stress acting on the wall a pipe or cylinder Internal stress acting on the wall a pipe or cylinder due to internal pressure.due to internal pressure.

Hoop StressHoop Stress

StressesStresses

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LongitudinalLongitudinal

Along the weld Along the weld –– longitudinal residual stresseslongitudinal residual stresses

TransverseTransverse

Across the weld Across the weld –– transverse residual stressestransverse residual stresses

Short TransverseShort Transverse

Through the weld Through the weld –– short transverse residual stressesshort transverse residual stresses

Residual stresses occur in welds in the following directionsResidual stresses occur in welds in the following directions

Residual StressesResidual Stresses

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Residual stressResidual stress

Heating and Heating and cooling causes cooling causes expansion and expansion and contractioncontraction

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Residual stressResidual stress

In case of a heated In case of a heated bar, the resistance bar, the resistance of the surrounding of the surrounding material to the material to the expansion and expansion and contraction leads contraction leads to formation of to formation of residual stressresidual stress

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1.1. Residual stresses are locked in elastic strain, which is Residual stresses are locked in elastic strain, which is caused by local expansion and contraction in the weld caused by local expansion and contraction in the weld area.area.

2.2. Residual stresses should be removed from structures Residual stresses should be removed from structures after welding.after welding.

3.3. The amount of contraction is controlled by, the volume of The amount of contraction is controlled by, the volume of weld metal in the joint, the thickness, heat input, joint weld metal in the joint, the thickness, heat input, joint design and the materials propertiesdesign and the materials properties

4.4. Offsetting may be used to finalise the position of the joint.Offsetting may be used to finalise the position of the joint.

5.5. If plates or pipes are prevented from moving by tacking, If plates or pipes are prevented from moving by tacking, clamping or jigging etc (restraint), then the amount of clamping or jigging etc (restraint), then the amount of residual stresses that remain will be higher.residual stresses that remain will be higher.

SummarySummary

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6.6. The movement caused by welding related stresses is The movement caused by welding related stresses is called distortion.called distortion.

7.7. The directions of contractional stresses and distortion is The directions of contractional stresses and distortion is very complex, as is the amount and type of final distortion, very complex, as is the amount and type of final distortion, however we can say that there are three directions: however we can say that there are three directions:

a. a. LongitudinalLongitudinal b. b. TransverseTransverse c. c. Short transverseShort transverse

8.8. A high percentage of residual stresses can be removed by A high percentage of residual stresses can be removed by heat treatments.heat treatments.

9.9. The The peeningpeening of weld faces will only redistribute the of weld faces will only redistribute the residual stress, and place the weld face in compression.residual stress, and place the weld face in compression.

SummarySummary

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Types of distortionTypes of distortionAngular distortionAngular distortion

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Angular DistortionAngular Distortion

Bowing DistortionBowing Distortion Longitudinal DistortionLongitudinal Distortion

Transverse DistortionTransverse Distortion

DistortionDistortion

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Factors which affect distortionFactors which affect distortion

•• Material properties and conditionMaterial properties and condition

•• Heat inputHeat input

•• The amount of restrainThe amount of restrain

•• The amount of weld metal depositedThe amount of weld metal deposited


Control of distortion my be achieved in the following way:Control of distortion my be achieved in the following way:

••The used of a different joint design The used of a different joint design

••Presetting the joints to be welded Presetting the joints to be welded –– so that the so that the metal distorts metal distorts into the required position.into the required position.

••The use of a balanced welding techniqueThe use of a balanced welding technique

••The use of clamps, jigs and fixtures.The use of clamps, jigs and fixtures.

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•• Distortion will occur in all welded joints if the material Distortion will occur in all welded joints if the material are are free to move i.e. not restrained free to move i.e. not restrained

•• Restrained materials result in low distortion but high Restrained materials result in low distortion but high residual stressresidual stress

•• More than one type of distortion may occur at one time More than one type of distortion may occur at one time

•• Highly restrained joints also have a higher crack Highly restrained joints also have a higher crack tendency tendency than joints of a low restraintthan joints of a low restraint

•• The action of residual stress in welded joints is to cause The action of residual stress in welded joints is to cause distortiondistortion


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DistortionDistortionFactors affecting distortion:Factors affecting distortion:

parent material propertiesparent material propertiesamount of restrainamount of restrainjoint designjoint designfitfit--upupwelding sequencewelding sequence

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Factors affecting distortionFactors affecting distortionParent material properties:Parent material properties:

thermal expansion coefficient thermal expansion coefficient -- the greater the value, the the greater the value, the greater the residual stressgreater the residual stressyield strength yield strength -- the greater the value, the greater the the greater the value, the greater the residual stressresidual stressYoungYoung’’s modulus s modulus -- the greater the value (increase in the greater the value (increase in stiffness), the greater the residual stressstiffness), the greater the residual stressthermal conductivity thermal conductivity -- the higher the value, the lower the the higher the value, the lower the residual stressresidual stresstransformation temperature transformation temperature -- during phase during phase transformation, expansion/contraction takes place. The transformation, expansion/contraction takes place. The lower the transformation temperature, the lower the lower the transformation temperature, the lower the residual stressresidual stress

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Factors affecting distortionFactors affecting distortionJoint design:Joint design:

weld metal volumeweld metal volumetype of joint type of joint -- butt vs. fillet, single vs. double sidebutt vs. fillet, single vs. double side

Amount of restrain:Amount of restrain:thickness thickness -- as thickness increase, so do the stressesas thickness increase, so do the stresseshigh level of restrain lead to high stresseshigh level of restrain lead to high stressespreheat may increase the level of stresses (pipe preheat may increase the level of stresses (pipe welding!)welding!)

FitFit--up:up:misalignment may reduce stresses in some casesmisalignment may reduce stresses in some casesroot gap root gap -- increase in root gap increases shrinkageincrease in root gap increases shrinkage

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Factors affecting distortionFactors affecting distortionWelding sequence:Welding sequence:

number of passes number of passes -- every pass adds to the total every pass adds to the total contractioncontractionheat input heat input -- the higher the heat input, the greater the higher the heat input, the greater the shrinkagethe shrinkagetravel speed travel speed -- the faster the welding speed, the the faster the welding speed, the less the stressless the stressbuildbuild--up sequenceup sequence

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Distortion preventionDistortion prevention

Distortion prevention by preDistortion prevention by pre--setting setting

a) prea) pre--setting of fillet joint to setting of fillet joint to prevent angular distortionprevent angular distortion

b) preb) pre--setting of butt joint to setting of butt joint to prevent angular distortionprevent angular distortion

c) tapered gap to prevent c) tapered gap to prevent closureclosure

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PrePre--set or Offsetting:set or Offsetting:

The amount of offsetting required is generally a function of The amount of offsetting required is generally a function of trial and error.trial and error.


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Distortion prevention by preDistortion prevention by pre--bending bending using strongbacks and wedges using strongbacks and wedges

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Clamping and jigging:Clamping and jigging:

The materials to be welded are prevented from moving by the The materials to be welded are prevented from moving by the clamp or jig the main advantage of using a jig is that the clamp or jig the main advantage of using a jig is that the elements in a fabrication can be precisely located in the elements in a fabrication can be precisely located in the position to be welded. Main disadvantage of jigging is high position to be welded. Main disadvantage of jigging is high restraint and high levels of residual stresses.restraint and high levels of residual stresses.


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Distortion preventionDistortion preventionDistortion prevention by restraint techniques Distortion prevention by restraint techniques

a) use of welding jigsa) use of welding jigs

b) use of flexible b) use of flexible clampsclamps

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Distortion preventionDistortion preventionDistortion prevention by restraint techniques Distortion prevention by restraint techniques

c) use of strongbacks c) use of strongbacks with wedgeswith wedges

d) use of fully welded d) use of fully welded strongbacksstrongbacks

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Distortion preventionDistortion preventionDistortion prevention by designDistortion prevention by designConsider eliminating the welding!!Consider eliminating the welding!!

a) by forming the platea) by forming the plateb) by use of rolled or extruded sectionsb) by use of rolled or extruded sections

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Distortion preventionDistortion preventionDistortion prevention by designDistortion prevention by design

consider weld placementconsider weld placement

reduce weld metal volume reduce weld metal volume and/or number of runsand/or number of runs

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The volume of weld metal in a joint will affect the amount of The volume of weld metal in a joint will affect the amount of local expansion and contraction, hence the more weld local expansion and contraction, hence the more weld deposited the higher amount of distortion deposited the higher amount of distortion

Preparation angle 60Preparation angle 60oo




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Distortion preventionDistortion preventionDistortion prevention by designDistortion prevention by design

use of balanced weldinguse of balanced welding

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-- Transverse ShrinkageTransverse ShrinkageFillet WeldsFillet Welds 0.8mm per weld where the leg length 0.8mm per weld where the leg length does not exceed 3/4 plate thicknessdoes not exceed 3/4 plate thicknessButt weldButt weld 1.5 to 3mm per weld for 601.5 to 3mm per weld for 60°° V joint, V joint, depending on number of runs depending on number of runs -- Longitudinal ShrinkageLongitudinal ShrinkageFillet WeldsFillet Welds 0.8mm per 3m of weld0.8mm per 3m of weldButt WeldsButt Welds 3mm per 3m of weld3mm per 3m of weld

Allowances to cover shrinkageAllowances to cover shrinkageDistortions prevention by designDistortions prevention by design

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Distortion preventionDistortion preventionDistortion prevention by fabrication techniques Distortion prevention by fabrication techniques

tack weldingtack weldinga) tack weld straight through a) tack weld straight through

to end of jointto end of jointb) tack weld one end, then use b) tack weld one end, then use

backback--step technique for step technique for tacking the rest of the jointtacking the rest of the joint

c) tack weld the centre, then c) tack weld the centre, then complete the tack welding complete the tack welding by the backby the back--step techniquestep technique

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back to back assemblyback to back assembly

a)a) assemblies tacked together assemblies tacked together before weldingbefore welding

b) use of wedges for b) use of wedges for components that distort on components that distort on separation after weldingseparation after welding

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use of stiffenersuse of stiffeners

control welding process by:control welding process by:-- deposit the weld metal as quickly as possible deposit the weld metal as quickly as possible -- use the least number of runs to fill the jointuse the least number of runs to fill the joint

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Distortion preventionDistortion preventionDistortion prevention by welding procedureDistortion prevention by welding procedure

reduce the number of reduce the number of runs required to make a runs required to make a weld (e.g. angular weld (e.g. angular distortion as a function distortion as a function of number of runs for a of number of runs for a 10 mm leg length weld)10 mm leg length weld)

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Distortion prevention by welding procedure Distortion prevention by welding procedure

control welding techniques by use control welding techniques by use balanced welding about the neutral axisbalanced welding about the neutral axiscontrol welding techniques by keeping control welding techniques by keeping the time between runs to a minimum the time between runs to a minimum

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Distortion preventionDistortion preventionDistortion prevention by welding procedureDistortion prevention by welding procedure

control welding techniques bycontrol welding techniques bya) Backa) Back--step weldingstep weldingb) Skip weldingb) Skip welding

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BackBack--skip welding techniqueskip welding technique

BackBack--step welding techniquestep welding technique

1.1. 2.2. 3.3. 4.4. 5.5. 6.6.

1.1. 2.2. 3.3. 6.6.4.4. 5.5.


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Distortion preventionDistortion preventionDistortion Distortion -- Best practice for fabrication corrective techniques Best practice for fabrication corrective techniques

using tack welds to set up and maintain the joint gap using tack welds to set up and maintain the joint gap

identical components welded back to back so welding can be identical components welded back to back so welding can be balanced about the neutral axisbalanced about the neutral axis

attachment of longitudinal stiffeners to prevent longitudinal attachment of longitudinal stiffeners to prevent longitudinal bowing in butt welds of thin plate structuresbowing in butt welds of thin plate structures

where there is choice of welding procedure, process and where there is choice of welding procedure, process and technique should aim to deposit the weld metal as quickly as technique should aim to deposit the weld metal as quickly as possible; MIG in preference to MMA or gas welding and possible; MIG in preference to MMA or gas welding and mechanised rather than manual weldingmechanised rather than manual welding

in long runs, the whole weld should not be completed in one in long runs, the whole weld should not be completed in one direction; backdirection; back--step or skip welding techniques should be usedstep or skip welding techniques should be used

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Distortion corrective techniquesDistortion corrective techniquesDistortion Distortion -- mechanical corrective techniques mechanical corrective techniques

Use of press to correct bowing in T butt jointUse of press to correct bowing in T butt joint

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Distortion corrective techniquesDistortion corrective techniquesDistortion Distortion -- Best practice for mechanical corrective techniques Best practice for mechanical corrective techniques

Use packing pieces which will over correct the distortion so Use packing pieces which will over correct the distortion so that springthat spring--back will return the component to the correct shapeback will return the component to the correct shape

Check that the component is adequately supported during Check that the component is adequately supported during pressing to prevent bucklingpressing to prevent buckling

Use a former (or rolling) to achieve a straight component or Use a former (or rolling) to achieve a straight component or produce a curvatureproduce a curvature

As unsecured packing pieces may fly out from the press, the As unsecured packing pieces may fly out from the press, the following safe practice must be adopted: following safe practice must be adopted:

-- bolt the packing pieces to the platen bolt the packing pieces to the platen -- place a metal plate of adequate thickness to intercept the place a metal plate of adequate thickness to intercept the

'missile' 'missile'

-- clear personnel from the hazard areaclear personnel from the hazard area

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Distortion corrective techniquesDistortion corrective techniquesDistortion Distortion -- thermal corrective techniques thermal corrective techniques

Localised heating to Localised heating to correct distortioncorrect distortion

Spot heating for Spot heating for correcting bucklingcorrecting buckling

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Line heating to correct angular Line heating to correct angular distortion in a fillet welddistortion in a fillet weld

Use of wedge shaped heating Use of wedge shaped heating to straighten plateto straighten plate

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Distortion corrective techniquesDistortion corrective techniquesDistortion Distortion -- thermal corrective techniques thermal corrective techniques Wedge shaped heating to correct distortionWedge shaped heating to correct distortion

a)a) standard rolled standard rolled steel sectionsteel section

b)b) buckled edge of buckled edge of plateplate

c)c) box fabricationbox fabrication

General guidelines:•Length of wedge = two-thirds of the plate width

•Width of wedge (base) = one sixth of its length (base to apex)

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•use spot heating to remove buckling in thin sheet structures•other than in spot heating of thin panels, use a wedge-shaped heating technique•use line heating to correct angular distortion in plate•restrict the area of heating to avoid over-shrinking the component•limit the temperature to 60° to 650°C (dull red heat) in steels to prevent metallurgical damage•in wedge heating, heat from the base to the apex of the wedge, penetrate evenly through the plate thickness and maintain an even temperature

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Heat TreatmentHeat TreatmentSection 18Section 18

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Heat TreatmentHeat TreatmentWhy?Why?

Improve mechanical propertiesImprove mechanical propertiesChange microstructureChange microstructureReduce residual stress levelReduce residual stress levelChange chemical compositionChange chemical composition

How?How?Flame ovenFlame ovenElectric oven/electric heating blanketsElectric oven/electric heating blanketsinduction/HF heating elementsinduction/HF heating elements

Where?Where? LocalLocalGlobalGlobal

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Heat TreatmentsHeat TreatmentsMany metals must be given heat treatment before and Many metals must be given heat treatment before and after welding. after welding.

The inspectorThe inspector’’s function is to ensure that the treatment s function is to ensure that the treatment is given correctly in accordance with the specification or is given correctly in accordance with the specification or as per the details supplied.as per the details supplied.

Types of heat treatment available:Types of heat treatment available:PreheatPreheat

AnnealingAnnealing

NormalisingNormalising

Quench HardeningQuench Hardening

TemperTemper

Stress ReliefStress Relief

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Heat TreatmentsHeat TreatmentsPrePre--heat treatmentsheat treatments

are used to increase weldability, by reducing sudden are used to increase weldability, by reducing sudden reduction of temperature, and control expansion and reduction of temperature, and control expansion and contraction forces during weldingcontraction forces during welding

Post weld heat treatmentsPost weld heat treatments

are used to change the properties of the weld metal, are used to change the properties of the weld metal, controlling the formation of crystalline structures controlling the formation of crystalline structures

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Post Weld Post Weld --Heat TreatmentsHeat TreatmentsPost Hydrogen Release Post Hydrogen Release (according to BS EN1011(according to BS EN1011--2)2)

Temperature:Temperature: Approximately 250Approximately 250°°C hold up to 3 hoursC hold up to 3 hours

Cooling:Cooling: Slow cool in air Slow cool in air

Result:Result: Relieves residual hydrogen Relieves residual hydrogen

Procedure:Procedure: Maintaining preMaintaining pre--heat / interpass temperature heat / interpass temperature after completion of welding for 2 to 3 hours.after completion of welding for 2 to 3 hours.

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Post Weld Heat TreatmentsPost Weld Heat Treatments

(A) Normalised

(B) Fully Annealed

(C) Water-quenched

(D) Water-quenched & tempered

A B

C D

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Post Weld Heat TreatmentsPost Weld Heat TreatmentsThe inspector, in general, should ensure that:The inspector, in general, should ensure that:

Equipment is as specifiedEquipment is as specified

Temperature control equipment is in good condition Temperature control equipment is in good condition

Procedures as specified, is being used e.g.Procedures as specified, is being used e.g.

oo Method of applicationMethod of application

oo Rate of heating and coolingRate of heating and cooling

oo Maximum temperatureMaximum temperature

oo Soak timeSoak time

oo Temperature measurement (and calibration)Temperature measurement (and calibration)

DOCUMENTATION AND RECORDSDOCUMENTATION AND RECORDS

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Post Weld Heat Treatment CyclePost Weld Heat Treatment Cycle

TimeTime

TemperaturTemperaturee SoakingSoakingTemperature Temperature

and time at the and time at the attained temperatureattained temperature

HeatingHeating SoakingSoaking CoolingCooling

heating rateheating rate Cooling rateCooling rate

Variables for heat treatment process must be carefully controlleVariables for heat treatment process must be carefully controlledd

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Post Weld Heat TreatmentPost Weld Heat TreatmentRemoval of Residual StressRemoval of Residual Stress

Temperature (Temperature (°°C)C)

100100 200200 300300 400400 500500 600600 700700

Yield Yield Strength Strength (N/mm(N/mm2 2 ))

100100

200200

300300

400400

500500CrCr--Mo steel Mo steel -- typicaltypical

CC--Mn steel Mn steel -- typicaltypical

•• At PWHT temp. the yield At PWHT temp. the yield strength of steel reduced strength of steel reduced so that it it is not strong so that it it is not strong enough to give restraint.enough to give restraint.

•• Residual stress reduced Residual stress reduced to very low level by to very low level by straining straining (typically < ~ (typically < ~ 0.5% strain)0.5% strain)

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Heat TreatmentHeat TreatmentRecommendationsRecommendations

Provide adequate support (low YS at high temperature!)Provide adequate support (low YS at high temperature!)

Control heating rate to avoid uneven thermal expansionsControl heating rate to avoid uneven thermal expansions

Control soak time to equalise temperaturesControl soak time to equalise temperatures

Control temperature gradients Control temperature gradients -- NO direct flame NO direct flame impingement!impingement!

Control furnace atmosphere to reduce scalingControl furnace atmosphere to reduce scaling

Control cooling rate to avoid brittle structure formationControl cooling rate to avoid brittle structure formation

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Post Weld Heat Treatment MethodsPost Weld Heat Treatment Methods

Gas furnace heat treatmentGas furnace heat treatment

Advantages: Advantages: Easy to set upEasy to set upGood portabilityGood portabilityrepeatability and repeatability and temperature uniformitytemperature uniformity

Disadvantages:Disadvantages:Limited to size of partsLimited to size of parts

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HF (Induction) local heat treatmentHF (Induction) local heat treatment

Advantages:Advantages:High heating ratesHigh heating ratesAbility to heat a Ability to heat a narrow bandnarrow band

Disadvantages:Disadvantages:High equipment High equipment costcostLarge equipment, Large equipment, less portableless portable

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Local heat treatment using Local heat treatment using electric heating blanketselectric heating blankets

Advantages:Advantages:Ability to vary Ability to vary heatheatAbility to Ability to continuously continuously maintain heatmaintain heat

Disadvantages:Disadvantages:Elements may Elements may burn out or arcing burn out or arcing during heatingduring heating

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Cutting ProcessesCutting ProcessesSection 19Section 19

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Use of gas flameUse of gas flame

WeldingWelding GougingGougingBrazingBrazing

HeatingHeating StraighteningStraightening

CuttingCutting

BlastingBlasting SprayingSpraying

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Oxygen regulatorOxygen regulator Fuel gas regulatorFuel gas regulator

RegulatorsRegulators

Regulator Regulator typetype

Single stageSingle stage

Two stageTwo stage

used when slight rise in delivery used when slight rise in delivery pressure from full to empty cylinder pressure from full to empty cylinder condition can be toleratedcondition can be tolerated

used when a constant delivery used when a constant delivery pressure from full to empty pressure from full to empty cylinder condition is requiredcylinder condition is required

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Flashback arrestorsFlashback arrestorsFlashback Flashback -- recession of the flame into or back of the mixing chamberrecession of the flame into or back of the mixing chamber

Flashback flame quenched at the flashback barrier

Flame barrier

Built-in check valve

Normal flow

Reverse flow

Flashback

Built-in check valve stops reverse flow

SAFETY SAFETY SAFETY

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A jet of pure oxygen reacts with iron, that has been A jet of pure oxygen reacts with iron, that has been preheated to its ignition point, to produce the preheated to its ignition point, to produce the oxide Feoxide Fe33OO4 4 by exothermic reaction.This oxide is by exothermic reaction.This oxide is then blown through the material by the velocity of then blown through the material by the velocity of the oxygen streamthe oxygen streamDifferent types of fuel gases may be used for the Different types of fuel gases may be used for the prepre--heating flame in oxy fuel gas cutting: i.e. heating flame in oxy fuel gas cutting: i.e. acetylene, hydrogen, propane. etcacetylene, hydrogen, propane. etc

By adding iron powder to the flame we are able By adding iron powder to the flame we are able to cut most metals to cut most metals -- ““Iron Powder InjectionIron Powder Injection””

The high intensity of heat and rapid cooling will The high intensity of heat and rapid cooling will cause hardening in low alloy and medium/high C cause hardening in low alloy and medium/high C steels steels �� they are thus prethey are thus pre--heated to avoid the heated to avoid the hardening effecthardening effect

Oxyfuel gas cutting processOxyfuel gas cutting processOxyfuel gas cutting process

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Oxyfuel gas cutting equipmentOxyfuel gas cutting equipmentOxyfuel gas cutting equipmentThe cutting torchThe cutting torch

Neutral cutting flameNeutral cutting flame

Neutral cutting flame with Neutral cutting flame with oxygen cutting streamoxygen cutting stream

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Oxyfuel gas cutting related termsOxyfuel gas cutting related terms

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Oxyfuel gas cutting qualityOxyfuel gas cutting qualityGood cut Good cut -- sharp top edge, fine and even drag lines, sharp top edge, fine and even drag lines, little oxide and a sharp bottom edgelittle oxide and a sharp bottom edge

Cut too fast Cut too fast --pronounced break in pronounced break in the drag line, the drag line, irregular cut edgeirregular cut edge

Cut too slow Cut too slow -- top edge is top edge is melted, deep groves in the melted, deep groves in the lower portion, heavy scaling, lower portion, heavy scaling, rough bottom edgerough bottom edge

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Preheat flame too high Preheat flame too high --top edge is melted, top edge is melted, irregular cut, excess of irregular cut, excess of adherent drossadherent dross

Preheat flame too low Preheat flame too low --deep groves in the lower deep groves in the lower part of the cutpart of the cut faceface

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Irregular travel speed Irregular travel speed -- uneven uneven space between drag lines, space between drag lines, irregular bottom with adherent irregular bottom with adherent oxideoxide

Nozzle is too high above Nozzle is too high above the works the works -- excessive excessive melting of the top edge, melting of the top edge, much oxidemuch oxide

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Mechanised oxyfuel cuttingMechanised oxyfuel cuttingcan use portable carriages or gantry type machines can use portable carriages or gantry type machines and obtain and obtain high productivityhigh productivityaccurate cutting for complicate shapesaccurate cutting for complicate shapes

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OFW/C advantages/disadvantagesOFW/C advantages/disadvantagesOFW/C advantages/disadvantagesDisadvantages:Disadvantages:

1) High skill factor1) High skill factor

2) Wide HAZ2) Wide HAZ

4) Slow process4) Slow process

5) Limited range of 5) Limited range of consumablesconsumables

3) Safety issues3) Safety issues


1) No need for power 1) No need for power supply,supply, portableportable

3) Low equipment cost3) Low equipment cost

4) Can cut carbon and low 4) Can cut carbon and low alloy steelsalloy steels

5) Good on thin materials5) Good on thin materials

2) Versatile: preheat, 2) Versatile: preheat, brazing, surfacing, repair, brazing, surfacing, repair, straighteningstraightening

6) Not suitable for reactive 6) Not suitable for reactive & refractory metals& refractory metals

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Special oxyfuel operationsSpecial oxyfuel operationsGougingGouging Rivet cuttingRivet cutting

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Special oxyfuel operationsSpecial oxyfuel operationsThin sheet cuttingThin sheet cutting Rivet washingRivet washing

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Cutting ProcessesCutting Processes

Plasma arc cuttingPlasma arc cuttingUses high velocity jet of ionised gas Uses high velocity jet of ionised gas through a constricted nozzle to remove the through a constricted nozzle to remove the molten metalmolten metalUses a tungsten electrode and water Uses a tungsten electrode and water cooled nozzlecooled nozzleHigh quality cuttingHigh quality cuttingHigh intensity and UV radiation High intensity and UV radiation –– EYES !EYES !

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Cutting ProcessesCutting ProcessesAirAir--arc for cutting or gougingarc for cutting or gouging

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AirAir--arc gouging featuresarc gouging features•• Operate ONLY on DCEPOperate ONLY on DCEP

•• Special gougingSpecial gouging copper copper coated carbon electrodecoated carbon electrode

•• Can be used on carbon Can be used on carbon and low alloy steels, and low alloy steels, austenitic stainless steels austenitic stainless steels and nonand non--ferrous materialsferrous materials

•• Requires CLEAN/DRY Requires CLEAN/DRY compressed air supplycompressed air supply

•• Provides fast rate of metal removalProvides fast rate of metal removal•• Can remove complex shape defectsCan remove complex shape defects•• After gouging, grinding of carbured layer is mandatoryAfter gouging, grinding of carbured layer is mandatory•• Gouging doesnGouging doesn’’t require a qualified welder!t require a qualified welder!

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Arc Welding SafetyArc Welding SafetyPlease discussPlease discuss

Section 20Section 20

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SafetySafety

Electrical safetyElectrical safetyHeat & LightHeat & Light–– Visible lightVisible light–– UV radiation UV radiation -- effects on effects on

skin and eyesskin and eyesFumes & Explosive Fumes & Explosive GassesGassesNoise levelsNoise levelsFire HazardsFire HazardsScaffolding & StagingScaffolding & StagingSlips, trips and fallsSlips, trips and fallsProtection of others from Protection of others from exposureexposure

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Weldability Of SteelsWeldability Of SteelsSection 21Section 21

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Weldability of SteelsWeldability of SteelsDefinitionDefinition

It relates to the ability of the metal (or alloy) to be welded wIt relates to the ability of the metal (or alloy) to be welded with ith mechanical soundness by most of the common welding mechanical soundness by most of the common welding processes, and the resulting welded joint retain the processes, and the resulting welded joint retain the properties for which it has been designed. properties for which it has been designed.

is a function of many interis a function of many inter--related factors but these may be related factors but these may be summarised as: summarised as:

Composition of parent materialComposition of parent material

Joint design and sizeJoint design and size

Process and techniqueProcess and technique

AccessAccess

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Weldability of SteelsWeldability of SteelsThe weldability of steel is mainly dependant on carbon & other aThe weldability of steel is mainly dependant on carbon & other alloying lloying elements content.elements content.

If a material has limited weldability, we need to take special mIf a material has limited weldability, we need to take special measures easures to ensure the maintenance of the properties requiredto ensure the maintenance of the properties required

Poor weldability normally results in the occurrence of crackingPoor weldability normally results in the occurrence of cracking

A steel is considered to have poor weldability when:A steel is considered to have poor weldability when:

•• an acceptable joint can only be made by using very narrow range an acceptable joint can only be made by using very narrow range of welding conditions of welding conditions

•• great precautions to avoid cracking are essential great precautions to avoid cracking are essential (e.g., high pre(e.g., high pre--heat etc)heat etc)

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The Effect of Alloying on SteelsThe Effect of Alloying on SteelsElements may be added to steels to produce the Elements may be added to steels to produce the properties required to make it useful for an application. properties required to make it useful for an application.

Most elements can have many effects on the properties Most elements can have many effects on the properties of steels.of steels.

Other factors which affect material properties are: Other factors which affect material properties are:

•• The temperature reached before and during weldingThe temperature reached before and during welding

•• Heat inputHeat input

•• The cooling rate after welding and or PWHTThe cooling rate after welding and or PWHT

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Iron (Fe):Iron (Fe): Main steel constituent. On its own, is relatively soft, ductileMain steel constituent. On its own, is relatively soft, ductile, with low , with low strength.strength.

Carbon (C):Carbon (C): Major alloying element in steels, Major alloying element in steels, a strengthening element with a strengthening element with major influence on HAZ hardnessmajor influence on HAZ hardness. Decreases weldability.. Decreases weldability.

••typically < ~ 0.25%typically < ~ 0.25%

Manganese (Mn):Manganese (Mn): Secondary only to carbon for strength, toughness and Secondary only to carbon for strength, toughness and ductility, secondary deductility, secondary de--oxidiseroxidiser and also reacts with and also reacts with sulphursulphur to form to form manganese manganese sulphidesulphide..

< ~0.8% is residual from steel de< ~0.8% is residual from steel de--oxidation oxidation

••up to ~1.6% (in Cup to ~1.6% (in C--Mn steels) improves strength & toughnessMn steels) improves strength & toughness

Silicon (Si):Silicon (Si): Residual element from steel deResidual element from steel de--oxidation.oxidation.

••typically to ~0.35%typically to ~0.35%

Steel Alloying ElementsSteel Alloying Elements

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Phosphorus (P):Phosphorus (P): Residual element from steelResidual element from steel--making minerals.making minerals. difficult to difficult to reduce below < ~ 0.015% brittlenessreduce below < ~ 0.015% brittleness

Sulphur (S):Sulphur (S): Residual element from steelResidual element from steel--making minerals making minerals

< ~ 0.015% in modern steels< ~ 0.015% in modern steels

< ~ 0.003% in very clean steels< ~ 0.003% in very clean steels

Aluminium (Al):Aluminium (Al): DeDe--oxidant and grain size controloxidant and grain size control

••typically ~ 0.02 to ~ 0.05%typically ~ 0.02 to ~ 0.05%

Chromium (Cr):Chromium (Cr): FFor creep resistance & oxidation (scaling) resistance for or creep resistance & oxidation (scaling) resistance for elevated temperature service.elevated temperature service. Widely used in stainless steels for Widely used in stainless steels for corrosion resistance, increases hardness and strength but reducecorrosion resistance, increases hardness and strength but reduces s ductility. ductility.

••typically ~ 1 to 9% in low alloy steelstypically ~ 1 to 9% in low alloy steels

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Nickel (Ni)Nickel (Ni):: Used in stainless steels, high resistance to corrosion from Used in stainless steels, high resistance to corrosion from acids, increases strength and toughnessacids, increases strength and toughness

Molybdenum (Mo)Molybdenum (Mo):: Affects Affects hardenabilityhardenability. Steels containing . Steels containing molybdenum are less susceptible to temper brittleness than molybdenum are less susceptible to temper brittleness than other alloy steels. other alloy steels. Increases the high temperature tensile and Increases the high temperature tensile and creep strengths of steel. typically ~ 0.5 to 1.0%creep strengths of steel. typically ~ 0.5 to 1.0%

Niobium (Nb)Niobium (Nb):: a grain refiner, typically~ 0.05%a grain refiner, typically~ 0.05%

Vanadium (V)Vanadium (V):: a grain refiner, typically ~ 0.05%a grain refiner, typically ~ 0.05%

Titanium (Ti)Titanium (Ti):: a grain refiner, typically ~ 0.05%a grain refiner, typically ~ 0.05%

Copper (Cu)Copper (Cu):: present as a residual, (typically < ~ 0.30%) present as a residual, (typically < ~ 0.30%) added to added to ‘‘weathering steelsweathering steels’’ (~ 0.6%) to give better resistance (~ 0.6%) to give better resistance to atmospheric corrosionto atmospheric corrosion

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Classification of SteelsClassification of SteelsMild steel (CE < 0.4)Mild steel (CE < 0.4)

Readily weldable, preheat generally not required if low hydrogenReadily weldable, preheat generally not required if low hydrogenprocesses or electrodes are used processes or electrodes are used Preheat may be required when welding thick section material, Preheat may be required when welding thick section material, high restraint and with higher levels of hydrogen being high restraint and with higher levels of hydrogen being generatedgenerated

CC--Mn, medium carbon, low alloy steels (CE 0.4 to 0.5)Mn, medium carbon, low alloy steels (CE 0.4 to 0.5)Thin sections can be welded without preheat but thicker sectionsThin sections can be welded without preheat but thicker sectionswill require low preheat levels and low hydrogen processes or will require low preheat levels and low hydrogen processes or electrodes should be usedelectrodes should be used

Higher carbon and alloyed steels (CE > 0.5)Higher carbon and alloyed steels (CE > 0.5)Preheat, low hydrogen processes or electrodes, post weld Preheat, low hydrogen processes or electrodes, post weld heating and slow cooling may be requiredheating and slow cooling may be required

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Process CracksProcess Cracks

•• Hydrogen Induced Hydrogen Induced HAZHAZ CrackingCracking (C/Mn steels)(C/Mn steels)

•• Hydrogen Induced Hydrogen Induced Weld MetalWeld Metal CrackingCracking (HSLA steels).(HSLA steels).

•• Solidification or Hot CrackingSolidification or Hot Cracking (All steels)(All steels)

•• Lamellar TearingLamellar Tearing (All steels)(All steels)

•• ReRe--heat Crackingheat Cracking (All steels, very susceptible Cr/Mo/V (All steels, very susceptible Cr/Mo/V steels)steels)

•• InterInter--Crystalline Corrosion or Weld DecayCrystalline Corrosion or Weld Decay (stainless (stainless steels)steels)

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CrackingCrackingWhen considering any type of cracking mechanism, three When considering any type of cracking mechanism, three elements must always be present:elements must always be present:

•• StressStressResidual stress is always present in a weldment, Residual stress is always present in a weldment, through unbalanced local expansion and through unbalanced local expansion and contractioncontraction

•• RestraintRestraintRestraint may be a local restriction, or through Restraint may be a local restriction, or through plates being welded to each otherplates being welded to each other

•• Susceptible microstructureSusceptible microstructureThe microstructure may be made susceptible to The microstructure may be made susceptible to cracking by the process of weldingcracking by the process of welding

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CracksCracks


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May occur:May occur:

up to 48 hrs after completion up to 48 hrs after completion

In weld metal, HAZ, parent In weld metal, HAZ, parent metal.metal.

At weld toesAt weld toes

Under weld beadsUnder weld beads

At stress raisers.At stress raisers.

Also know as:

Cold Cracking, happens when the welds cool down.

HAZ cracking, normally occurs in the HAZ.

Delayed cracking, as it takes time for the hydrogen to migrate. 48 Hours normally but up to 72,

Under-bead cracking, normally happens in the HAZ under a weld bead

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There is a risk of hydrogen cracking when all of the 4 There is a risk of hydrogen cracking when all of the 4 factors occur together:factors occur together:

Hydrogen Hydrogen More than 15ml/100g of weld metalMore than 15ml/100g of weld metal

StressStress More than More than ½½ the yield stressthe yield stress

TemperatureTemperature Below 300Below 300ooCC

HardnessHardness Greater than 400HV VickersGreater than 400HV Vickers

Susceptible MicrostructureSusceptible Microstructure (Martensite)(Martensite)


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Precautions for controlling hydrogen crackingPrecautions for controlling hydrogen cracking

Pre heat, removes moisture from the joint preparations, Pre heat, removes moisture from the joint preparations, and slows down the cooling rateand slows down the cooling rate

Ensure joint preparations are clean and free from Ensure joint preparations are clean and free from contaminationcontamination

The use of a low hydrogen welding process and correct The use of a low hydrogen welding process and correct arc lengtharc length

Ensure all welding is carried out is carried out under Ensure all welding is carried out is carried out under controlled environmental conditionscontrolled environmental conditions

Ensure good fitEnsure good fit--up as to reduced stressup as to reduced stress

The use of a PWHT The use of a PWHT

Avoid poor weld profilesAvoid poor weld profiles

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•• Hydrogen is the smallest atom knownHydrogen is the smallest atom known

•• Hydrogen enters the weld via the arcHydrogen enters the weld via the arc

•• Source of hydrogen mainly from moisture pickSource of hydrogen mainly from moisture pick--up on up on the electrodes coating, welding fluxes or from the the electrodes coating, welding fluxes or from the consumable gasconsumable gas

HH22

HH22

HH22

HH22HH22

Moisture on Moisture on the electrode the electrode or grease on or grease on the wirethe wire

Water vapour Water vapour in the air or in the air or in the in the shielding gasshielding gas

Oxide or grease on Oxide or grease on the platethe plate


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Hydrogen absorbed in a long, or unstable arc

Hydrogen introduced in weld from consumable, oils, or paint on plate

Cellulosic electrodes produce hydrogen as a shielding gas

Hydrogen Hydrogen crackcrack

Martensite forms from γ H2 diffuses to γ in HAZ

H2H2


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Hydrogen Induced Cold CrackingHydrogen Induced Cold CrackingSusceptible Microstructure:Susceptible Microstructure:

Hard brittle structure Hard brittle structure –– MARTENSITE Promoted by:MARTENSITE Promoted by:

A)A) High Carbon Content, Carbon Equivalent (CE)High Carbon Content, Carbon Equivalent (CE)

Heat input (Kj/mm)Heat input (Kj/mm) = Amps x Volts x arc time= Amps x Volts x arc time

Run out length x 10Run out length x 103 3 (1000) (1000)

CEV = %C + CEV = %C + MnMn + + Cr+Mo+V Cr+Mo+V + + Ni+CuNi+Cu6 5 156 5 15

B)B) high alloy content high alloy content C)C) fast cooling rate:fast cooling rate: Inadequate PreInadequate Pre--HeatingHeating

Cold MaterialCold MaterialThick Material Thick Material Low Heat Input.Low Heat Input.

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Typical locations for Cold CrackingTypical locations for Cold Cracking

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••HSLA or MicroHSLA or Micro--Alloyed Steels are high strength steels Alloyed Steels are high strength steels (800MPa/N/mm2) that derive their high strength from small (800MPa/N/mm2) that derive their high strength from small percentage alloying (overpercentage alloying (over--alloyed Weld metal to match the alloyed Weld metal to match the strength of parent metal)strength of parent metal)

••Typically the level of alloying is in the elements such as Typically the level of alloying is in the elements such as vanadium molybdenum and titanium, vanadium molybdenum and titanium, nickel and chromium nickel and chromium StrengthStrength. are used. It would be impossible to match this micro . are used. It would be impossible to match this micro alloying in the electrode due to the effect of losses across an alloying in the electrode due to the effect of losses across an electric arc (Ti burn in the arc)electric arc (Ti burn in the arc)

••It is however important to match the strength of the weld to It is however important to match the strength of the weld to the strength of the plate, Mn 1.6 Cr Ni Mothe strength of the plate, Mn 1.6 Cr Ni Mo

HICC in HSLA steelsHICC in HSLA steels

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Hydrogen ScalesHydrogen Scales

List of hydrogen scales from BS EN 1011:part 2.List of hydrogen scales from BS EN 1011:part 2.

Hydrogen content related to 100 grams of weld Hydrogen content related to 100 grams of weld metal deposited.metal deposited.

ScaleScale AA High:High: >>15 ml15 ml

ScaleScale B B Medium:Medium: 10 ml 10 ml -- 15 ml15 ml

ScaleScale C C Low: Low: 5 ml 5 ml -- 10 ml10 ml

ScaleScale D D Very low: Very low: 3 ml 3 ml -- 5 ml5 ml

ScaleScale E E UltraUltra--low: low: << 3 ml3 ml

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Potential Hydrogen Level ProcessesPotential Hydrogen Level Processeslist of welding processes in order of potential lowest list of welding processes in order of potential lowest hydrogen content with regards to 100g of deposited weld hydrogen content with regards to 100g of deposited weld metal.metal.

TIGTIG < 3 ml< 3 ml

MIGMIG < 5 ml< 5 ml

ESWESW < 5 ml< 5 ml

MMA (Basic Electrodes)MMA (Basic Electrodes) < 5 ml< 5 ml

SAWSAW < 10ml< 10ml

FCAWFCAW < 15 ml< 15 ml

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WeldabilityWeldability


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Usually Occurs in Weld Centerline Usually Occurs in Weld Centerline


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Solidification CrackingSolidification CrackingAlso referred as Also referred as

Hot Cracking:Hot Cracking: Occurring at high temperatures while the weld is hot Occurring at high temperatures while the weld is hot

Centerline cracking:Centerline cracking: cracks appear down the centre line of the bead.cracks appear down the centre line of the bead.

Crater cracking:Crater cracking: Small cracks in weld centers are solidification cracksSmall cracks in weld centers are solidification cracks

Crack type:Crack type: Solidification cracking Solidification cracking

Location:Location: Weld centreline (longitudinal) Weld centreline (longitudinal)

Steel types:Steel types: High sulphur & phosphor concentration in steels.High sulphur & phosphor concentration in steels.

SusceptibleSusceptible Microstructure: Microstructure: Columnar grains In direction Columnar grains In direction of solidificationof solidification

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Factors for solidification crackingFactors for solidification cracking

•• Columnar grain growth with impurities in weld metal (Columnar grain growth with impurities in weld metal (sulphursulphur, , phosphor and carbon)phosphor and carbon)

•• The amount of stress/restraintThe amount of stress/restraint

•• Joint design high depth to width ratios Joint design high depth to width ratios

Liquid iron sulphides are formed around solidifying grains. Liquid iron sulphides are formed around solidifying grains.

High contractional strains are present High contractional strains are present

High dilution processes are being used. High dilution processes are being used.

There is a high carbon content in the weld metalThere is a high carbon content in the weld metal

•• Most commonly occurring in subMost commonly occurring in sub--arc welded joints arc welded joints


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Solidification CrackingSolidification Cracking•• SulphurSulphur in the parent material may dilute in the weld in the parent material may dilute in the weld

metal to form iron sulphides (low strength, low metal to form iron sulphides (low strength, low melting point compounds)melting point compounds)

•• During weld metal solidification, columnar crystals During weld metal solidification, columnar crystals push still liquid iron sulphides in front to the last place push still liquid iron sulphides in front to the last place of solidification, weld centerline.of solidification, weld centerline.

•• The bonding between the grains which are The bonding between the grains which are themselves under great stress and may now be very themselves under great stress and may now be very poor to maintain cohesion and a crack will result, poor to maintain cohesion and a crack will result, weld centerline.weld centerline.

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Deep, narrower weld beadDeep, narrower weld bead

On solidification the On solidification the bonding between the grains bonding between the grains may now be very poor to may now be very poor to maintain cohesion and a maintain cohesion and a crack may resultcrack may result

Shallow, wider weld beadShallow, wider weld bead

On solidification the On solidification the bonding between the bonding between the grains may be adequate to grains may be adequate to maintain cohesion and a maintain cohesion and a crack is unlikely to occurcrack is unlikely to occur

Solidification CrackingSolidification CrackingAvoidanceAvoidance

HAZHAZ HAZHAZ

Intergranular liquid filmIntergranular liquid filmColumnar Columnar grainsgrains Columnar Columnar

grainsgrains

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Precautions for controlling solidification crackingPrecautions for controlling solidification cracking

••The first steps in eliminating this problem would be to choose aThe first steps in eliminating this problem would be to choose a low low dilution process, and change the joint designdilution process, and change the joint design

Grind and seal in any lamination and avoid further dilution????Grind and seal in any lamination and avoid further dilution????

Add Manganese to the electrode to form spherical Mn/S which formAdd Manganese to the electrode to form spherical Mn/S which formbetween the grain and maintain grain cohesionbetween the grain and maintain grain cohesion

As carbon increases the Mn/S ratio required increases As carbon increases the Mn/S ratio required increases exponentially and is a major factor. Carbon content % should be exponentially and is a major factor. Carbon content % should be a a minimised by careful control in electrode and dilutionminimised by careful control in electrode and dilution

Limit the heat input, hence low contraction, & minimise restrainLimit the heat input, hence low contraction, & minimise restraintt


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Solidification CrackingSolidification CrackingPrecautions for controlling solidification crackingPrecautions for controlling solidification cracking

•• The use of high manganese and low carbon content The use of high manganese and low carbon content fillersfillers

•• Minimise the amount of stress / restraint acting on the Minimise the amount of stress / restraint acting on the joint during welding joint during welding

•• The use of high quality parent materials, low levels of The use of high quality parent materials, low levels of impurities (Phosphor & impurities (Phosphor & sulphursulphur))

•• Clean joint preparations contaminants (oil, grease, paints Clean joint preparations contaminants (oil, grease, paints and any other and any other sulphursulphur containing product) containing product)

•• Joint design selection depth to width ratiosJoint design selection depth to width ratios

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Solidification cracking in Austenitic Stainless SteelSolidification cracking in Austenitic Stainless Steel

particularly prone to solidification crackingparticularly prone to solidification cracking

large grain size gives rise to a reduction in grain boundary arelarge grain size gives rise to a reduction in grain boundary area a with high concentration of impurities with high concentration of impurities

Austenitic structure very intolerant to contaminants (Austenitic structure very intolerant to contaminants (sulphursulphur, , phosphorous and other impurities). phosphorous and other impurities).

High coefficient of thermal expansion /Low coefficient of thermaHigh coefficient of thermal expansion /Low coefficient of thermal l conductivity, with high resultant residual stressconductivity, with high resultant residual stress

same precautions against cracking as for plain carbon steels same precautions against cracking as for plain carbon steels with extra emphasis on thorough cleaning and high dilution with extra emphasis on thorough cleaning and high dilution controls. controls.

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CracksCracks

Lamellar TearingLamellar Tearing

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Lamellar TearingLamellar TearingFactors for lamellar tearing to occurFactors for lamellar tearing to occur

Cracks only occur in the rolled plate !Cracks only occur in the rolled plate !

Close to or just outside the HAZ !Close to or just outside the HAZ !

Cracks lay parallel to the plate surface and the fusion Cracks lay parallel to the plate surface and the fusion boundary of the weld and has a stepped aspect.boundary of the weld and has a stepped aspect.

•• Low quality parent materials, high levels of impuritiesLow quality parent materials, high levels of impurities

•• Joint design, direction of stressJoint design, direction of stress

•• The amount of stress acting across the joint during The amount of stress acting across the joint during weldingwelding

•• Note: very susceptible joints may form lamellar tearing Note: very susceptible joints may form lamellar tearing under very low levels of stress under very low levels of stress

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Tee fillet weldTee fillet weld Tee butt weld Tee butt weld (double(double--bevel)bevel)

Corner butt weldCorner butt weld(single(single--bevel)bevel)

Susceptible joint types combined with susceptible rolled plate Susceptible joint types combined with susceptible rolled plate used to make a joint.used to make a joint.

High stresses act in the through thickness direction of the platHigh stresses act in the through thickness direction of the plate e (know as the short transverse direction).(know as the short transverse direction).

T, K & Y joints normally end up with a tensile residual stress T, K & Y joints normally end up with a tensile residual stress component in the through thickness direction.component in the through thickness direction.


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Critical areaCritical area

Critical Critical areaarea

Critical areaCritical area


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Modifying a corner joint to avoid lamellar tearingModifying a corner joint to avoid lamellar tearing

SusceptibleSusceptible NonNon--SusceptibleSusceptible

Prior welding both Prior welding both plates may be grooved plates may be grooved to avoid lamellar tearingto avoid lamellar tearing

An open corner joint An open corner joint may be selected to may be selected to avoid lamellar tearingavoid lamellar tearing


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Precautions for controlling lamellar tearingPrecautions for controlling lamellar tearing

•• The use of high quality parent materials, low levels of The use of high quality parent materials, low levels of impuritiesimpurities

•• The use of buttering runsThe use of buttering runs

•• A gap can be left between the horizontal and vertical A gap can be left between the horizontal and vertical members enabling the contraction movement to take place members enabling the contraction movement to take place

•• Joint design selection Joint design selection

•• Minimise the amount of stress / restraint acting onMinimise the amount of stress / restraint acting on the the joint joint during weldingduring welding

•• Hydrogen precautionsHydrogen precautions


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Lamellar TearingLamellar TearingCrack type:Crack type: Lamellar tearingLamellar tearing

Location:Location: Below weld HAZBelow weld HAZ

Steel types:Steel types: High sulphur & phosphorous steelsHigh sulphur & phosphorous steels

Microstructure:Microstructure: Lamination & SegregationLamination & Segregation

Occurs when:Occurs when:

High contractional strains are through the short High contractional strains are through the short transverse direction. There is a high sulfur content in transverse direction. There is a high sulfur content in the base metal.the base metal.

There is low through thickness ductility in the base There is low through thickness ductility in the base metal.metal.

There is high restraint on the workThere is high restraint on the work

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The short tensile test or through thickness test is a The short tensile test or through thickness test is a test to determine a materials susceptibility to test to determine a materials susceptibility to lamellar tearing lamellar tearing

Friction Welded CapsFriction Welded CapsShort Tensile SpecimenShort Tensile Specimen

Through Through Thickness Thickness DuctilityDuctility

Sample of Parent MaterialSample of Parent Material

The results are given as a The results are given as a STRASTRA valuevalueShort Transverse Reduction in AreaShort Transverse Reduction in Area

Short Tensile (Through Thickness) TestShort Tensile (Through Thickness) Test

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High contractional strains

Lamellar tear

Restraint


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Practical Visual InspectionPractical Visual InspectionSection 22Section 22

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Leg Length GaugeLeg Length Gauge

G.A.L.

S.T.D.

10mm

12m

m

16mm

3mm

6mm

9mm

5mm4m

m

L

Throat Thickness GaugeThroat Thickness Gauge

G.A.L.

S.T.D.

10mm

12mm

16mm

3mm

6mm

9mm5mm

4mm

T

Fillet Weld GaugesFillet Weld Gauges

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HI-L

O S

ingl

e Pu

rpos

e W

eldi

ng G

auge

1

2

3

4

5

6 Root gap Root gap dimensiondimension

Internal Internal alignmentalignment

HIHI--LO Welding GaugeLO Welding Gauge

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Plate / Pipe InspectionPlate / Pipe Inspection

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Remember in the CSWIP 3.1 Welding Inspectors Remember in the CSWIP 3.1 Welding Inspectors examination your are required to conduct a practical examination your are required to conduct a practical examination of a plate test weld, complete a thumb examination of a plate test weld, complete a thumb print sketch and a final report on your findingsprint sketch and a final report on your findings

Time allowed 1 hour and 15 minutesTime allowed 1 hour and 15 minutes

The code is providedThe code is provided

Plate Inspection ExaminationPlate Inspection Examination

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1)1) Use a pencil for the arrow lines, but make all Use a pencil for the arrow lines, but make all written comments and measurements in written comments and measurements in ink ink onlyonly

3)3) Do not forget to Do not forget to compare and sentencecompare and sentence your your reportreport

2) Report 2) Report everythingeverything that you can observethat you can observe

4) Do not forget to 4) Do not forget to date & signdate & sign your reportyour report

5)5) Make any observations, such as Make any observations, such as recommendations for further investigation for recommendations for further investigation for crackcrack--like imperfections.like imperfections.

Plate Inspection PointsPlate Inspection Points

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After you have observed an imperfection and After you have observed an imperfection and determined its type, you must be able to take determined its type, you must be able to take measurements and complete the thumb print report measurements and complete the thumb print report sketchsketchThe first thumb print report sketch should be in the The first thumb print report sketch should be in the form of a repair map of the weld. (i.e. form of a repair map of the weld. (i.e. AllAllobservations are Identified Sized and Located) observations are Identified Sized and Located)

The thumb print report sketch used in CSWIP exam The thumb print report sketch used in CSWIP exam will look like the following example.will look like the following example.

Plate Thumb Print ReportPlate Thumb Print Report

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After you have completed your thumb print report After you have completed your thumb print report sketch of your test plate the next step is to complete sketch of your test plate the next step is to complete your final report again the report must be your final report again the report must be completed in completed in ink (no pencil).ink (no pencil).The report must be completed to your thumb print The report must be completed to your thumb print sketch, do not leave any boxes empty, sketch, do not leave any boxes empty, every box must every box must be completed or dashed outbe completed or dashed out. You must also make any . You must also make any comments you feel are necessary regarding any comments you feel are necessary regarding any defects observed.defects observed.

The report form used in CSWIP will look like the The report form used in CSWIP will look like the following example.following example.

Plate Inspection Final ReportPlate Inspection Final Report

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Remember in the CSWIP 3.1 Welding Inspectors Remember in the CSWIP 3.1 Welding Inspectors examination your are required to conduct a examination your are required to conduct a practical examination of a pipe test weld, complete practical examination of a pipe test weld, complete a thumb print sketch and a final report on your a thumb print sketch and a final report on your findingsfindings

Time allowed 1 hour and 45 minutesTime allowed 1 hour and 45 minutes

The code is nominated e.g API 1104The code is nominated e.g API 1104

Pipe InspectionPipe Inspection

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Application & Control of Pre heatApplication & Control of Pre heatSection 23Section 23

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Welding TemperaturesWelding TemperaturesDefinitionsDefinitions

Preheat temperaturePreheat temperatureis the temperature of the workpiece in the weld zone immediatelyis the temperature of the workpiece in the weld zone immediatelybefore before anyany welding operation (including tack welding!)welding operation (including tack welding!)

normally expressed as a minimum normally expressed as a minimum Interpass temperatureInterpass temperature

–– is the temperature in a multiis the temperature in a multi--run weld and adjacent parent metal run weld and adjacent parent metal immediately prior to the application of the next runimmediately prior to the application of the next run

–– normally expressed as a maximumnormally expressed as a maximum

Minimum interpass temperature = Preheat temperatureMinimum interpass temperature = Preheat temperaturePre heat maintenance temperature = the minimum temperature in the weld zone which shall be maintained if welding is interrupted and shall be monitored during the interruption.

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PrePre--heat Applicationheat ApplicationFurnaceFurnace -- Heating entire component Heating entire component -- bestbest

Electrical elementsElectrical elements --Controllable; Portable; Site use; Clean; Controllable; Portable; Site use; Clean; Component cannot be moved. Component cannot be moved.

Gas burnersGas burners -- direct flame impingement; Possible local direct flame impingement; Possible local overheating; Less controllable;Portable; Manual operation overheating; Less controllable;Portable; Manual operation possible; Component can be moved.possible; Component can be moved.

Radiant gas heatersRadiant gas heaters -- capable of automatic control; No flame capable of automatic control; No flame impingement; No contact with component; Portable. impingement; No contact with component; Portable.

Induction heatingInduction heating -- controllable; Rapid heating (mins not hours); controllable; Rapid heating (mins not hours); Large power supply; Expensive equipmentLarge power supply; Expensive equipment

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Measuring pre heat in WeldingMeasuring pre heat in Welding

Parameters to be measured:Parameters to be measured:welding currentwelding currentarc voltagearc voltagetravel speedtravel speedshielding gas flow rateshielding gas flow rate

The purposes The purposes of measuringof measuring

Demonstration of Demonstration of conformance to conformance to

specified requirementsspecified requirements

preheat/interpass preheat/interpass temperaturetemperatureforce/pressureforce/pressurehumidityhumidity

Welding Welding process process controlcontrol

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PrePre--heat Applicationheat Application

Application Of PreheatApplication Of Preheat

Heat either side of jointHeat either side of joint

Measure temp 2 mins after heat removalMeasure temp 2 mins after heat removal

Always best to heat complete component rather than Always best to heat complete component rather than local if possible to avoid distortionlocal if possible to avoid distortion

Preheat always higher for fillet than butt welds due to Preheat always higher for fillet than butt welds due to different combined thicknesses and chill effect factors.different combined thicknesses and chill effect factors.

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Manual Gas OperationManual Gas Operation

PrePre--Heat ApplicationHeat Application

Electrical Heated Electrical Heated ElementsElements

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Welding TemperaturesWelding Temperatures

Point of MeasurementPoint of MeasurementBS EN ISO 13916BS EN ISO 13916

t t < 50 mm < 50 mm

A = 4 x t but max. 50 mmA = 4 x t but max. 50 mm

the temperature shall be the temperature shall be measured on the surface measured on the surface of the workpiece facing the of the workpiece facing the welderwelder

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Welding TemperaturesWelding TemperaturesPoint of MeasurementPoint of Measurement

BS EN ISO 13916BS EN ISO 13916

t > 50mm t > 50mm

A = 75mm minimumA = 75mm minimum

the temperature shall be the temperature shall be measured on the face measured on the face opposite to that being opposite to that being heatedheated

allow 2 min per every 25 allow 2 min per every 25 mm of parent metal mm of parent metal thickness for temperature thickness for temperature equalisationequalisation

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Combined ThicknessCombined ThicknessThe Chilling Effect of the JointThe Chilling Effect of the Joint

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Combined ThicknessCombined ThicknessThe Chilling Effect of the JointThe Chilling Effect of the Joint

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Combined ThicknessCombined Thickness

Combined chilling effect of joint type and Combined chilling effect of joint type and thickness.thickness.

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The Chill Effect of the MaterialThe Chill Effect of the Material

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Heating Temperature ControlHeating Temperature Control

TEMPILSTICKS TEMPILSTICKS -- crayons, melt at set temps. Will not crayons, melt at set temps. Will not measure max temp.measure max temp.

Pyrometers Pyrometers -- contact or remote, measure actual temp.contact or remote, measure actual temp.

Thermocouples Thermocouples -- contact or attached, very accurate, contact or attached, very accurate, measure actual temp.measure actual temp.

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Temperature Test EquipmentTemperature Test EquipmentTemperature sensitive Temperature sensitive materials:materials:

••crayons, paints and crayons, paints and pillspills

••cheapcheap

••convenient, easy to convenient, easy to useuse

••doesndoesn’’t measure the t measure the actual temperature!actual temperature!

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Temperature Test EquipmentTemperature Test Equipment

Contact thermometerContact thermometer

••AccurateAccurate

••Easy to useEasy to use

••Gives the actual temperatureGives the actual temperature

••Requires calibrationRequires calibration

••suitable for moderate suitable for moderate temperaturestemperatures

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Temperature Test EquipmentTemperature Test EquipmentThermocoupleThermocouple

•• based on measuring the thermoelectric potential difference based on measuring the thermoelectric potential difference between a hot junction (on weld) and a cold junction between a hot junction (on weld) and a cold junction

•• accurate methodaccurate method

•• measures over a wide range of temperaturesmeasures over a wide range of temperatures

•• gives the actual temperaturegives the actual temperature

•• need calibrationneed calibration

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Temperature Test EquipmentTemperature Test EquipmentThermistorsThermistors

•• temperaturetemperature--sensitive resistors sensitive resistors whose resistance varies inversely whose resistance varies inversely with temperaturewith temperature

•• used when high sensitivity is used when high sensitivity is requiredrequired

•• gives the actual temperaturegives the actual temperature

•• need calibrationneed calibration

•• can be used up to 999can be used up to 999°°CC

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Temperature test equipmentTemperature test equipmentDevices for contactless measurementDevices for contactless measurement

•• IR radiation and optical IR radiation and optical pyrometerpyrometer

•• measure the radiant energy measure the radiant energy emitted by the hot bodyemitted by the hot body

•• contactless method, contactless method, can be can be used for remote measurements used for remote measurements

•• very complexvery complex

•• for measuring high for measuring high temperaturestemperatures

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CalibrationCalibrationSection 24Section 24

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Calibration, validation and monitoringCalibration, validation and monitoringDefinitions:Definitions:

MeasurementMeasurement = set of operations for determining a value of a = set of operations for determining a value of a quantityquantityRepeatabilityRepeatability = closeness between successive measuring = closeness between successive measuring results of the same instrument carried out under the same results of the same instrument carried out under the same conditionsconditionsAccuracy classAccuracy class = class of measuring instruments that are = class of measuring instruments that are intended to keep the errors within specified limitsintended to keep the errors within specified limitsCalibrationCalibration = checking the errors in a meter or measuring = checking the errors in a meter or measuring devicedeviceValidationValidation = checking the control knobs and switches provide = checking the control knobs and switches provide the same level of accuracy when returned to a prethe same level of accuracy when returned to a pre--determined determined pointpointMonitoringMonitoring = checking the welding parameters (and other = checking the welding parameters (and other items) are in accordance with the procedure or specificationitems) are in accordance with the procedure or specification

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Calibration and validationCalibration and validationFrequency Frequency -- When it is required?When it is required?

once a year unless otherwise specifiedonce a year unless otherwise specifiedwhenever there are indications that the whenever there are indications that the instrument does not register properlyinstrument does not register properlywhenever the equipment has been whenever the equipment has been damaged, misused or subject to severe damaged, misused or subject to severe stressstresswhenever the equipment has been rebuild whenever the equipment has been rebuild or repairedor repaired

See BS EN ISO 17662 for details!See BS EN ISO 17662 for details!

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Welding parameter calibration/validationWelding parameter calibration/validation

Which parameters need calibration/validation?Which parameters need calibration/validation?

depends on the welding processdepends on the welding processsee BS EN ISO 17662 and BS 7570 for detailssee BS EN ISO 17662 and BS 7570 for details

How accurate?How accurate?

depends on the applicationdepends on the applicationwelding current welding current -- ±±2,5%2,5%arc voltage arc voltage -- ±±5%5%wire feed speed wire feed speed -- ±±2,5%2,5%gas flow rate gas flow rate -- ±±20% (20% (±±25% for backing gas flow rate)25% for backing gas flow rate)temperature (thermocouple) temperature (thermocouple) -- ±±5%5%

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PAMS (Portable Arc Monitor System)PAMS (Portable Arc Monitor System)What does a PAMS measure?What does a PAMS measure?

Welding Welding current (Hall current (Hall effect effect device)device)

Arc voltage Arc voltage (connection (connection leads)leads)

Temperature Temperature (thermocouple)(thermocouple)

Wire feed Wire feed speed speed (tachometer)(tachometer)

Gas flow Gas flow rate rate (heating (heating element element sensor)sensor)

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PAMS (Portable Arc Monitor System)PAMS (Portable Arc Monitor System)

The purposes of The purposes of a PAMSa PAMS

For calibrating For calibrating and validating and validating

the welding the welding equipmentequipment

For measuring For measuring and recording and recording

the welding the welding parametersparameters

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Use of PAMSUse of PAMSWire feed speed Wire feed speed monitoringmonitoring

Incorporated pair of Incorporated pair of rolls connected to a rolls connected to a tachogeneratortachogenerator

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Use of PAMSUse of PAMSShielding gas flow Shielding gas flow rate monitoringrate monitoring

Heating element Heating element sensorsensor

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SummarySummarya welding power source can only be calibrated if it a welding power source can only be calibrated if it has meters fittedhas meters fitted

the inspector should check for calibration stickers, the inspector should check for calibration stickers, dates etc.dates etc.

a welding power source without meters can only be a welding power source without meters can only be validated that the control knobs provide repeatabilityvalidated that the control knobs provide repeatability

the main role is to carryout the main role is to carryout ““in process monitoringin process monitoring”” to to ensure that the welding requirements are met during ensure that the welding requirements are met during productionproduction

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Macro/Micro ExaminationMacro/Micro ExaminationSection 25Section 25

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Macro PreparationMacro PreparationPurposePurpose

To examine the weld crossTo examine the weld cross--section to give assurance that: section to give assurance that: --

•• The weld has been made in accordance with the WPSThe weld has been made in accordance with the WPS

•• The weld is free from defectsThe weld is free from defects

Specimen PreparationSpecimen Preparation

•• Full thickness slice taken from the weld Full thickness slice taken from the weld (typically ~10mm thick)(typically ~10mm thick)

•• Width of slice sufficient to show all the weld and HAZ on both Width of slice sufficient to show all the weld and HAZ on both sides sides plus some unaffected base materialplus some unaffected base material

•• One face ground to a progressively fine finish One face ground to a progressively fine finish (grit sizes 120 to ~ 400)(grit sizes 120 to ~ 400)

•• Prepared face heavily etched to show all weld runs & all HAZPrepared face heavily etched to show all weld runs & all HAZ

•• Prepared face examined at up to x10 Prepared face examined at up to x10 (& usually photographed for records)(& usually photographed for records)

•• Prepared face may also be used for a hardness surveyPrepared face may also be used for a hardness survey

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Micro PreparationMicro PreparationPurposePurpose

To examine a particular region of the weld or HAZ in order to:To examine a particular region of the weld or HAZ in order to:--

•• To examine the microstructureTo examine the microstructure

•• Identify the nature of a crack or other imperfectionIdentify the nature of a crack or other imperfection

Specimen PreparationSpecimen Preparation

•• A small piece is cut from the region of interestA small piece is cut from the region of interest(typically up to ~ 20mm x 20mm)(typically up to ~ 20mm x 20mm)

•• The piece is mounted in plastic mould and the surface of intereThe piece is mounted in plastic mould and the surface of interest st prepared by progressive grinding (to grit size 600 or 800)prepared by progressive grinding (to grit size 600 or 800)

•• Surface polished on diamond impregnated cloths to a mirror finiSurface polished on diamond impregnated cloths to a mirror finishsh

•• Prepared face may be examined in asPrepared face may be examined in as--polished condition & then lightly polished condition & then lightly etchedetched

•• Prepared face examined under the microscope at up to ~ x 600Prepared face examined under the microscope at up to ~ x 600

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Macro / Micro ExaminationMacro / Micro ExaminationObject:Object:

•• Macro / microscopic examinations are used to give a Macro / microscopic examinations are used to give a visual evaluation of a crossvisual evaluation of a cross--section of a welded joint section of a welded joint

•• Carried out on full thickness specimensCarried out on full thickness specimens

•• The width of the The width of the specimenspecimen should include HAZ, weld should include HAZ, weld and parent plateand parent plate

•• They maybe cut from a stop/start area on a welders They maybe cut from a stop/start area on a welders approval testapproval test

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Macro / Micro ExaminationMacro / Micro ExaminationWillWill Reveal:Reveal:

•• Weld soundnessWeld soundness

•• Distribution of inclusionsDistribution of inclusions

•• Number of weld passesNumber of weld passes

•• Metallurgical structure of weld, fusion zone and HAZMetallurgical structure of weld, fusion zone and HAZ

•• Location and depth of penetration of weldLocation and depth of penetration of weld

•• Fillet weld leg and throat dimensionsFillet weld leg and throat dimensions

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•• Visual examination for Visual examination for defectsdefects

•• Cut transverse from the Cut transverse from the weldweld

•• Ground & polished P400 Ground & polished P400 grit papergrit paper

•• Acid etch using 5Acid etch using 5--10% 10% nitric acid solutionnitric acid solution

•• Wash and dryWash and dry

•• Visual evaluation under 5x Visual evaluation under 5x magnificationmagnification

•• Report on resultsReport on results

•• Visual examination for Visual examination for defects & grain structuredefects & grain structure

•• Cut transverse from a Cut transverse from a weldweld

•• Ground & polished P1200 Ground & polished P1200 grit paper, 1grit paper, 1µµm pastem paste

•• Acid etch using 1Acid etch using 1--5% 5% nitric acid solutionnitric acid solution

•• Wash and dryWash and dry

•• Visual evaluation under Visual evaluation under 100100--1000x magnification1000x magnification

•• Report on resultsReport on results

MacroMacro MicroMicro

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Metallographic ExaminationMetallographic Examination

Macro examinationMacro examination Micro examinationMicro examination

welding

Documents

welding gauges welding

visual inspection standard

welding procedures

good inspectors

magnification lens

good vision

measuring devices

surface viewing angle