03 - overview of welding process

8/14/2019 03 - Overview of Welding Process

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TNB Integrated Learning Solution(ILSAS)

Engineering Maintenance & Services (GEN) Mac 2011 R0SLAN BIN ALI

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Overview of Welding Process


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Engineering Maintenance & Services (GEN) Mac 2011 R0SLAN BIN ALI2

Diversity of welding processesWELDING

Solid state welding Soldering and brazingFusion welding

Electrical energy Chemical energy

Other processesNon consumable

electrode

Consumable electrode

Resistance welding

Cold welding

Friction welding

Diffusion welding

Flash welding

Ultrasonic welding

Explosion welding

Gas metal arc welding

Shielded metal arc welding

Submerged arc welding

Flux cored arc welding

Electrogas welding

Electroslag welding

Gas tungsten arc welding

Atomic hydrogen welding

Plasma arc welding

Oxyacetylene gas welding

Oxyfuel gas welding

Laser beam welding

Thermit welding

Electron beam welding

Soldering

Brazing


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JOINING

Soldering Produces coalescence of materials by heatingto soldering temperature (below sol idus ofbase metal) in presence of filler metal withliquidus < 450C

Brazing

Same as soldering butcoalescence occurs at> 450C

Welding Process of achieving complete coalescence

of two or more materials through melting & re-solidification of the base metals and fillermetal


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Soldering & Brazing

Advantages

Low temperature heat source required

Choice of permanent or temporary joint

Dissimilar materials can be joined

Less chance of damaging parts

Slow rate of heating & cooling

Parts of varying thickness can be joined

Easy realignment

Strength and performance of structural joints needcareful evaluation


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Welding

Advantages

Most efficient way to join metals

Lowest-cost joining method

Affords lighter weight through better utilization ofmaterials

Joins all commercial metals

Provides design flexibility


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Weldability

Weldability is the ease of a material or acombination of materials to be welded underfabrication conditions into a specific, suitablydesigned structure, and to perform satisfactorily inthe intended service

Common Arc Welding Processes

Shielded Metal Arc Welding (SMAW) or MMA

Gas Tungsten Arc Welding (GTAW) or, TIG

Gas Metal Arc Welding (GMAW) or MIG/MAG Flux Cored Arc Welding (FCAW)

Submerged Arc Welding (SAW)


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Alternating Current

Alternating current:

The type of current where

the flow of electrons

reverses direction

(polarity) at regular

intervals.


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Direct Current Direct current: The type

of current where the

flow of electrons

(polarity) is in one

direction.

Controlling the polarity

allows the welder to

influence the location of

the heat.

When the electrode is

positive (+) DCRP orDCEP it will be slightly

hotter than the base

metal.

When the base metal is positive

(+), DCSP or DCEN, the base metal

will be slightly hotter than the

electrode.

DC current is required for some

electrodes and recommended for

out of position welding.


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Ampere

Amperes: the unit of measure for current flow.

Volt

The volt is the measure of electromotive force.

It is defined as the potential difference across a

conductor when a current of one ampere

dissipates one watt of power.

The voltage at the electrode determines the

harshness of the arc.

Voltage is only adjustable in dual control

machines.

Voltage


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Polarity


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Polarity

++

+

+

+

+

-

-

-

--

-

Electrode Negative Electrode Positive

Work Piece Positive Work Piece Negative

Ions IonsElectrons Electrons

Straight Polarity DCEN Reverse Polarity DCEP

(-) (+)

(-)(+)


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Type of welding

Manual Welding

SMAW

GTAW Semi automatic

GMAW

Automatic

Robotic welding

2 parameters:

Feed

Speed


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Shielded metal arc

welding (stick welding)

performed by a (human)

welder usingconsumable electrodes.

Also known as MMA

(Manual Metal ArcWelding).

Shielded Metal Arc Welding

(SMAW)


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Shielded metal arc welding (SMAW).



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Welding Rod Classification (ex. E-6010)

The E- stands for electrode.

The first two numbers indicate the tensile strength

The next-to-last number gives the welding positions

The last digit of the weld rod number indicates the typeof current for which the rod may be used (ac, dc straight,

dc reverse), the penetration, and the type of flux around

the rod.

Example: E-6010 would have a tensile strength of60,000 psi, could be used in all positions, has a

cellulose-sodium flux, could give deep penetration, and

must be used with dc reverse current.


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Video

Presentation ofSMAW


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Gas Metal Arc Welding

(GMAW)

Is a process where acontinuously fed metal electrode

(wire) contacts the base metaland produces heat .

The arc is shielded by an inertgas or active gas.

Also known as MIG/MAG (MetalInert Gas / Metal Active Gas)


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GMAW component diagram


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Gas metal arc welding (GMAW).

Gas Metal Arc Welding


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Video

Presentation ofGMAW


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Submerged Arc Welding

(SAW)


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- +

Power

supply

Filler wire spool

Flux hopper

Wire electrode

Flux

Slide rail


(SAW)


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Submerged arc welding.



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Video

Presentation ofSAW


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Is a process where a tungstenelectrode contacts the basemetal and produces heat andfiller rod were also utilized.

The arc is shielded by an inertgas (argon gas).

Also known as TIG (Tungsten

Inert Gas Arc Welding)

Gas Tungsten Arc Welding


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Gas tungsten arc welding.

Gas Tungsten Arc Welding


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Plasma arc welding (PAW).

Plasma Arc Welding

TNB I d L i S l i
http://localhost/var/www/apps/conversion/tmp/Video/Robotic%20plasma%20powder%20welding%20(%20PTA%20).avi


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A typical oxyacetylene welding operation

Oxyacetylene Welding

TNB I t t d L i S l ti


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Maximum temperature reached at tip of inner cone,while outer envelope spreads out and shields work

surfaces from atmosphere

The neutral flame from an oxyacetylene torch indicating

temperatures achieved.

Oxyacetylene Torch

TNB I t t d L i S l ti


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TNB Integ ated Lea ning Sol tion


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Thermit welding: (1) Thermit ignited; (2) crucible tapped, superheated

metal flows into mold; (3) metal solidifies to produce weld joint.

Thermit Welding

TNB Integrated Learning Solution


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Thermit Welding



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Underwater Welding



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Resistance welding, showing the components in spot

welding, the main process in the RW group.

Resistance Welding



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(a) Spot welding cycle, (b) plot of squeezing force & current incycle (1) parts inserted between electrodes, (2) electrodesclose, force applied, (3) current on, (4) current off, (5)

electrodes opened.

Spot Welding Cycle



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Resistance seam welding

(RSEW).

Resistance Seam Welding

http://localhost/var/www/apps/conversion/tmp/Video/Seam%20Welding.flvhttp://localhost/var/www/apps/conversion/tmp/Video/Resistance%20Welding.flvhttp://localhost/var/www/apps/conversion/tmp/Video/Seam%20Welding.flv


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Friction welding (FRW): (1) rotating part, no contact; (2) parts

brought into contact to generate friction heat; (3) rotation stopped

and axial pressure applied; and (4) weld created.

Friction Welding



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Friction Welding

http://localhost/var/www/apps/conversion/tmp/Video/Pipe%20-%20Friction%20Stir%20Welding.flv


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Joints, Welds & Positions

Five (5) types of joints,

Five (5) types of welds and

Five (5) positions (plate)



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Butt Lap

T

Corner

Edge

Five (5) joints:



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1. Surface

2. Groove

3. Fillet

4. Plug

5. Slot

Five types of welds




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1. Surface Welds

Surface welds are welds were a material has

been applied to the surface of another

material.

Two common applications are

for hard surfacing and padding



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2. Groove Welds

Groove welds are used to fuse the sides orends of two pieces of metal.

The primary use of groove welds is to

complete butt joints.



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3. Fillet Welds

Fillet welds have a triangular cross section and are used tofuse two faces of metal that are at a 90 degree angle toeach other.

Lap JointOutside Corner T Joint



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4. Plug Welds

Plug welds are used to attach two surfaces

together when a complete joint is not

required and the design does not allow for

any weld bead outside the dimensions of

the metal.

The holes can be made with a drill bit or punch.

The weld is completed by establishing the arc on the bottom plate and then

continuing to weld until the hole is full.



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5. Slot Welds

Slot welds are identical to plug welds except for the shapeof the holes. For slot welds, slots are machined orstamped in the upper plate.

They are complete the same as plug welds.



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Positions

HorizontalFlat

Vertical Up

Overhead

Vertical Down

Five types of position



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Welding Positions

FLAT

HORIZONTAL

VERTICAL

OVERHEAD

INCREASING

DIFFICULTY



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FLAT POSITION

HORIZONTAL POSITION VERTICAL POSITION OVERHEAD POSITION

PLATES AND

AXIS OF WELD

HORIZONTAL

1G

PLATES VERTICAL

AND AXIS OF WELD

HORIZONTAL

2G

PLATES VERTICAL

AND AXIS OF WELD

VERTICAL

3G

PLATES AND AXIS

OF WELD

HORIZONTAL

4G

WELDING POSITIONS -- GROOVE WELDS -- PLATE.

UNDERSTANDING ABOUT WELDING POSITION

ON BUTT JOINTS.



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FLAT POSITION

1FHORIZONTAL POSITION

2F

VERTICAL POSITION

3F

AXIS OF WELD VERTICALAXIS OF WELD HORIZONTAL

AXIS OF WELD VERTICAL AXIS OF WELD HORIZONTAL

WELDING POSITIONS ---

FILLET WELDS ---

PLATE

OVERHEAD POSITION

4F



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PIPE OR TUBE HORIZONTAL FIXED

WELD FLAT, VERTICAL & OVERHEAD

POSITION:

5G.

45 0+ - 50PIPE INCLINED FIXED ( 45 0+ - 50) AND NOT

ROTATED DURING WELDING.

POSITION:

6G

WELDING POSITION -- PIPE WELDS.



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Weld Nomenclature

PenetrationBead

Base metal

Joint Angle Reinforcement

Bead

Root FaceExcessive

PenetrationRoot Opening



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Weld Nomenclature-cont.

Root

Throat

Face

Toe

Reinforcement

Leg

Leg

Toe

TNB Integrated Learning Solution(ILSAS)Weld Nomenclature cont


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Weld Nomenclature-cont.

In multiple pass welds, each pass has a specific function.

Tack Weld

Root Pass

Filler Pass

Cover Pass

A tack weld is used to hold thejoint at the desired gap.

If it is not used, the heat of

the weld will cause the joint

to close.

The filler pass is used to fill in the joint. A pattern bead or multiple stringer beads will be used.

The root pass is used to fuse the root

of the weld. If the root pass does not have

adequate penetration, it must be

cut or gouged out before the

weld is completed.

The cover pass doesnt add very much strength to the weld. It is used for

appearance and to fill in surface voids.



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Bead Patterns

Pattern beads are usedwhenever a wider bead is

needed.

Hardsurfacing

Filler pass

Cover pass

Reduce penetration

Common patterns:

Circle

Crescent

Figure 8


TYPICAL WELD DEFECTS


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03 - overview of welding process

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