arc welding

Metals and Engineering Industry 5.12AB Perform Routine Manual Metal Arc Welding

ContentsTraining Record Introduction Topics Prerequisites Instructions Competency 3 7 7 7 7 7 9 9 9 10 10

assessment

Section 1 - Introduction to Manual Metal Arc Wdding Aim Acti vity MMAWelding video response Arc welding

Section 2 - Operating Principles for Manual Arc Welding 13 Aim 13 Activity 13 Electricity 14 Hazards 14 Protective clothing 17 Maintenance of welding equipment.. 2021 Welding machines 23 Power source 26 Rating of power sources 29 Current range 29 Electrodes 30 Basic symbols 33 Welding symbols 33 \Velding procedures 35 Joint preparation 37 Review questions - Operating principles for manual arc welding38 Review questions - Weld symbols 42 Review questions - Electrode identification - Current settings .. 44 Section 3 - Manual Metal Arc Welding - Basic Welds Aim Acti vity Manual metal arc welding - basic welds Material preparation HOViT strike an arc to Laying down a weld bead Weld cleaning Review questions - Material preparation and weld cleaning 45 45 45 .46 46 47 48 49 50

5


Practical exercise 1 - Beads on plate - flat Procedure sheet 1 - Beads on plate - flat Practical exercise 2 - Pad welds - flat.. Procedure sheet 2 - Pad weld - flat Section 4 - Fillet Weld Joint Terms and Faults Aim Activity Fillet weld joint terminology and faults Fillet weld terminology Weld Defects Workshop tests Review questions - Fillet weld joint terminology and faults Practical exercise 3 - Fillet weld, single run - horizontaL Procedure sheet 3 - Fillet weld, single run - horizontal Practical exercise 4 - Fillet weld, 3 run 2 layer - horizontal.. Procedure sheet 4 - Fillet weld, 3 run 2 layer - horizontal. Practical exercise 5 - Outside corner fillet - horizontal Prooedure sheet 5 - Outside corner fillet - horizontaL Practical exercise 6 - Fillet weld - horizontal Prooedure sheet 6 - Fillet weld - horizontal Seotion 5 - Butt Weld Terminology and Faults Aim Activity Butt weld terminology and faults Weld preparation Preparation types Weld defects The principle of expansion and contraction in a metal Angular distortion Review questions - Butt weld terminology and faults Practical exercise 7 - Butt weld, flat sheet steel Procedure sheet 7 - Butt weld, flat sheet steel

52 54 55 57 59 59 59 60 60 62 67 69 78 80 81 83 84 86 87 89 90 90 90 91 91 93 96 101 101 102 108 110

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Metals and Engineering S.12AB Perform

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Routine Manual Metal Arc Welding

IntroductionThis training guide is designed to support training for the Metal and Engineering Training Package.

Topics Operating principles for manual arc welding Manual metal arc welding - basic welds Fillet weld joint terms and faults Butt weld terminology and faults

PrerequisitesNil

Instructions1. Study the information for each topic and complete review questions Complete the practical exercises.

2.note

The pr~ctical exercises are suggested only and may be replaced by any other suitable training activity. 3. The Training Record must be signed by your trainer on completion of each activity. Complete the theory test. (The test results may be recorded as part evidence of competency.)

4.

Competency assessmentTo achieve competency other approved activities must be entered in the Assessment and Evidence Record section.

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Routine Manual Metal Arc Weldiug

Section 1 - Introduction to Manual Metal Arc WeldingAimTo understand the operating principles, equipment, consumables and safety requirements for general purpose welding using the manual metal arc welding process.

Activity1. 2. View video No. 47 Arc Welding. Complete the video response questions immediately after watching the video. during or

3.

Ask your supervisor or teacher if the information is not clear to you. Ask your trainer to check and sign your Training Record. On completion of this section you must attempt the test on this topic and reach the required level of competence before proceeding to the next section.

4. S.

Safety Wear safety glasses at all times while in welding workshops. Follow safe working practices to avoid electric shock. Weld in well ventilated areas. Wear protective clothing.

9


Section 2 - Operating Principles for Manual Arc WeldingAimTo practice manual metal arc welding exercises in order for you to develop the manipulative skills for striking an arc and depositing weld metal on low carbon steel plate.

Activity1. 2. 3. Read and study the resource material following. Complete the review questions. Ask for assistance if the information or instructions are not clear to you. 4. Ask a teacher or your supervisor to check and sign your Training Record.

Safety Follow OHS workshop procedures. Protect your eyes from the welding arc and wear the proper eye protection. Wear suitable protective clothing including dry leather gloves.

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Metals and Engineering Industry S.12AB Perform Routine Manual Metal Arc Welding

The welding process uses electricity and generates heat and fumes. Safety precautions including wearing protective clothing are important. Maintenance of equipment and supplies and a thorough understanding of safety aspects of welding will minimise the risk of accident and injury.

ElectricityElectricity is the flow of electrons through a conductor at a certain pressure and speed. It's like water running through a hose. Some of the terms associated with electricity are explained here. Conductor In welding an electrical conductor is a metal through which electricity will easily flow. Copper is the most used conductor. Voltage This is the unit of electrical pressure. The voltage at the terminals of an AC welding machine is never more than 80 volts for safety reasons. This electrical pressure (or force) is responsible for the current flow in a welding circuit. Amperage This is the measurement of the electron flow,or current, through an electrical conductor. Amperage is measured in amps. An amp is a unit quantity of electricity passing through a given point per second. This is similar to the rate water flows through a pipeline. Electric arc welding process This is also called manual metal arc welding or MMA In MMA a high output amperage (low voltage) is passed W. W through a consumable flux coated electrode and the work piece. This sets up an electrical resistance between the tip of the electrode and the work which causes the electrode to melt off and form a weld bead.

HazardsWorking with electrical equipment can be hazardous. Youmust take proper precautions and follow the set safety procedures. Hazards in the welding workshop include electric shock, fumes, heat, glare and harmful rays.

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Electric shocks - low voltage Electric shocks are possible on the secondary welding circuit. They may be caused by: working on wet floors - a shock may be felt when putting an electrode in the holder. Always stand on insulated mats or wooden boards to reduce the risk and wear dry leather gloves working in a very humid climate or rainy weather - a shock may be felt when changing electrodes. gloves dry. Electrical shocks high voltage High voltage shocks shouldn't happen if precautions are taken such as Keep electrodes and (low voltage) side of the

ensuring welding machines are maintained by licensed electrical tradesmen and that you never interfere with the inside parts of the welding machines. Symptoms of electrical shock Often electric shock stuns but doesn't kill. However when electricity passes through the body it causes muscles to contract from beating or cause breathing to stop. Electricity can also cause serious burns. Fumes Fumes can result from: the production combustion of oxides and nitrous gases from incomplete and can stop the heart

or oxidation of nitrogen from the atmosphere cadmium

the surface coatings on steel such as galvanising, parts/degreasing elements solvents

or chrome plating and paints and solvents such as red oxide

within the parent metal

electrode flux coatings.

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Metals and Engineering S.12AB Perform Routine

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Manual Metal Arc Welding

Safety

Welding should be carried out in well ventilated areas. When welding high fuming materials such asga1vanised steel, use extraction systems to carry away the fumes. If an extraction system is not available, an approved respirator should be used to filter out the fumes. Respirators should only be used as a secondary protection.Dangerous fumes

Gases, dusts and vapours are given off during welding. They can cause: gassing or asphyxiation because the oxygen has been used up in the work area (common in confined spaces) build up of poisonous metals in the body, such as lead, cadmium, zinc, beryllium or mercury respiratory disorders. Heat Heat is a form of energy. When a substance is heated the molecules vibrate or move more rapidly. Heat may be generated by various means. In manual metal arc welding it is generated by the passage of an electric current across an arc;: ap. g The electric arc (about 6000C) generates the heat to melt and fuse the metal surfaces. Heat is transferred in two ways, by conduction and by radiation. Conduction Solid bodies must be in physical contact for heat to travel through them. Some materials conduct heat more rapidly than others. Metals are generally good conductors but, because of their different properties, some have a greater conductivity rate than others, for example copper and aluminium are very good conductors while cast iron and stainless steel are poorer conductors. ailments from wheeziness to serious lung

16


Radiation This is the transfer of heat through space by wave motion. No

physical contact is needed. All bodies at a higher temperature than their surroundings radiate heat, for example, the sun radiates heat energy in the form of cosmic rays and an electric radiator transfers heat through space across a room.

Protective clothingProtective clothing will help to protect you from heat, hot metal and harmful rays.Helmet

Gauntlets

Leather apron

Gaiters,

'''-.

Spats ~--..~

Full protective clothingProtection against hot metal

Molten droplets have a way of getting into boots. You can avoid this by wearing proper protective clothing and footwear. When welding out of position wear spats over your boots and under overall legs.

17


Protection from harmful rays

The harmful rays given off from an electrical welding process are ultraviolet rays and infra-red rays. These rays can damage the skin. Ray burn is like very severe sunburn; your skin reddens and then peels. If the ray burn is very severe, there may be blisters and sores. Rays will also harm the eyes causing a condition called a flash or arc eye. The first symptom of a flash is an itchy feeling in the eye. Afterwards a throbbing pain (much like sand in the eye) may stop you sleeping. There are eye drops that relieve the pain. Continuos flashes may cause blindness. The use of Safety Glasses will help protect your eyes from these rays. Filter lenses These are specially designed glass lenses to filter out harmful rays and allow you to see what you're welding without causing any changes in the pupil size or damage to your eyes. Filters come in different shade numbers, according to the current range or type of welding.Recommended minimum protective filters

Process MMAW

Approximate Welding (AMPS) Up to 100 100 - 200 200 - 300 300 - 400 Over 400

Filter Recommended

81011

12 13

Safety Wear safety glasses at all times. Wear appropriate clothing to protect your eyes and skin, from welding rays. Prevention, is the best policy, avoid exposing eyes to harmful rays.

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Metals and Engineering Industry 5.12AB Perform Routine Manual Metal Are Welding

Wear a welding shield or helmet, fitted with the correct filter to protect you from arc rays, heat and the spatter from molten metal. The filter reduces the intensity of the radiation, but allows sufficient light through for you to see the weld pool and the end of the electrode.

Swivel filter

Clear glass

Head shield

hand held shield

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Metals and Engineering lndustry 5.12AB Perform Routine Manual Metal Arc Welding

Maintenance of welding equipmentBefore carrying out any maintenance on electrical equipment, it's important that you first switch off the power and remove the plug. If there isn't a plug, lock off the machine or danger tag the isolator switch.Transformer

Never do maintenance work inside the case of the welding machine. Operators can care for the machine by: keeping the case clean and dust free maintaining the secondary circuit in good condition sending the machine to a licensed electrician for any maintenance on the internal parts, the primary lead and plug.Machine terminals

Keep terminals clean and tight to ensure that the current will flow freely. If you don't check nut tightness now and then, you may get arcing and/or overheating of the terminal and lug connections. This will also be detrimental to weld quality and machine performance. This can lead to fire or cause burns.Joints

Loose joints or bad contacts cause cable, clamps and other parts of the welding plant to overheat and may give you unstable arcing. Use properly designed cable connectors when you make any joints in cables. Make sure that good electrical contact is made when you connect cables to the power source, electrode holder and the return work clampSecondary leads (electrode/return lead)

Damaged leads may cause the operator discomfort from overheating, and poor arcing characteristics. Maintain leads by: rolling them up after use unroll prior to using

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making electrode

sure that the ends are fixed correctly holder, work-clamp or terminal lugs

into the

covering lug connections with insulation tape when necessary. The size of the cable must suit the output of the welding power source at the maximum duty cycle (refer to Australian Standard AS 1995 on welding cables for the cable size).Electrode holders

Electrode

holders should suit the minimum

output current

being used.

The holder should be relatively light, comfortable holder should be rated to withstand the activity.Retumclamp

to hold, fully insulated current required for

and sturdy enough to withstand the wear and tear from constant use. The the maximum

This is fastened to the work or to the workbench type clamps are also available.Twist handle to grip electrode

to complete the welding

circuit. Spring pressure and screw type clamps are normally used. Magnetic

Insert electrode

Heavy duty type

Spring-loaded jaws to grip electrode

Electrode holders

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Metals and Engineering Industry5.12AB Perform Routine Manual Metal Arc Welding

Screw Clamp

Work cable attachments

~/-...,Cable attachments

.

-: /0'1

/-

a

/.

SafetyProtect yourself by wearing the following safety clothing: overalls or work clothes leather apron and/or coat welding gloves.

Machine locationWelding machines should always be in a dry protected area as close to the

power outlet as possible.

Protection of othersWelding should be done in special welding bays. When this is not possible, use portable screens to shield others working in the area from the rays generated from the arc. You should also put up signs to warn people that you are welding.

22


Welding machinesWeldingmachines operate with either alternating current or direct current.Alternating current (AC) welding machines

Alternating current welding machines are transformers which step down line voltage (240 or 415 volts) to provide a safe welding voltage. The welding current supplied by the secondary circuit of the transformer is set by the operator to suit the type and size of electrode and its use. Transformer welding machines are less complex and slightly less expensive than other types.Direct current (DC) welding machines

The direct current output may be supplied by a transformer/rectifier or generator power source.Transformer/rectifiers

An efficient and reliable transformer/rectifier is a machine designed to transform AC input current to DC output current suitable for welding. Transformer/rectifiers have no moving parts and like the transformer are quiet to operate, convenient and cost less than motor generated units. If an AC current is needed from this type of machine, all the operator has to do is to select the AC output switch. Transformer/rectifiers are often designed to provide either DC or AC outputs. DC is normally preferred because of its greater arc stability but AC may be required at higher currents to avoid arc blow.

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Arc welding power source - AC transforrner

Arc welding power source - mobile engine driven DC generator

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Metals and Engineering lndustl)' 5.12AB Perlorm Routine Manual Metal Arc Welding

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Metals and Engineering 5.12AB Perform Routine

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Power sourceA welding source provides enough current (heat energy) to melt the electrode and the parent metal. Manual metal arc welding machines have a variable (adjustable) current output that can be set to suit the job and type of electrode.Power source terminals and polarity

Electrical connections for a welding machine are illustrated below. Output terminals on AC machines are marked electrode and work. On a DC machine the terminals are marked positive (+) and negative (-) except in the case where the polarity can be changed by means of a polarity reversing switch. In such cases the terminals are marked electrode and work with electrode terminal polarity indicated at the polarity switch. Most electrodes designed for DC operate on DC electrode terminal positive (+) while some types of electrodes should be operated on DC electrode negative (-). Refer to the manufacturer's instructions for polarity selection.

Main voltage 415 or 240 volts

45-80V Weld M/C

Open circuit 'Voltage (no currentjlowing)

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Mctals and Enginccring Industry S.12AB Perform Routine Manual Mctal Arc Welding

Main voltage 415 or 240 volts

Arc voltage (currentjlowing) Welding cables

A multiple-strand, insulated flexible copper or aluminium lead conducts the welding current from the power source to the work. A return cable is needed to complete the welding circuit between the work and the power source.

Power source

Electrode holder

Cable connections (secondary circuit side)

27


Open circuit voltage - arc voltage Power sources may supply direct current (DC) or alternating current (AC) to the electrode. AC transformers and DC generators supply only one type of current, but many transformer/rectifiers can be switched between AC and DC output. AC power supply is used more often because the cost is lower and the welding machines are simpler in design. However, DC current has some advantages. The DC arc is much more stable with certain types of electrode. DC is better for working with sheet metal because a stable arc is produced. Engine driven DC models provide welding power where there are no electrical supply lines available, for example on site work. The current should remain nearly constant during welding where the operator's movements tend to vary the arc length. These movements may be accidental, or deliberate, to control the weld pool. An increase in arc length win increase the voltage across the arc, however the machine is designed to control the current close to the amperage set by the operator. Melting of the electro 0 Amps

60

200 100 250 150 SO

20:l!!

60 40 0

Output curvefor constant current power source, adjustedfor minimum current 'Variation

Rating of power sourcesAustralian Standard AS1966 rates the output (duty cycle) of electric arc welding power sources. The machines are classified according to the type of service for which they are designed, for example: continuous duty, heavy duty, light industrial or limited output cycles. The standard defines each of the classes according to the output (load current, load voltage) needed for a nominated duty cycle. The duty cycle allows for the Jact that in any five minute period, current for welding may be drawn for only part of that time. For example, if welding is for a maximum of three minutes in any five minute period, the machine only operates up to 60% duty cycle (3/5 of 5 minutes). A much lower current must be selected for continuous (100%) operation. All power sources must display a name plate stating the equipment class and the rated output and duty cycle for its class (eg 300 amps, 32 volts, 60%duty cycle). The 100% duty cycle output current must also be noted.

Current rangeThe manufacturer's recommendations on the range of current for different types and sizes of electrodes will only give you their lower and upper current range.

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Metals and Engineering 5.12AB Perform

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Routine Manual Metal Aro Welding

Typical current ranges for the electrode

classifications

4.0

130-160 75-125

130-190 90-140

140-200 95-150

130-170 100-130

140-200 105-150

185-235 130-170

3.25

You should use the recommended amperage and electrode type and size as stated in the procedure sheets for the practical exercises. This will help you gain the experience to select the electrode type and size for future welding exercises.

4113~

The choice of current will depend on such factors as weld position, thickness of the joint parts, root gap and access to the structure.Packet of electrodes

ElectrodesElectrodes are available in different types.EXX12 Electrodes These have rutile coatings with other constituents

added to form a gaseous shield and slag modification. These electrodes are easy to use in any positions (including vertical do\'\rn).They operate with a quiet, medium penetrating arc able to bridge gaps or misaligned sections. These electrodes are general purpose electrodes used for structural and sheet steel fabrication.EXX13 Electrodes These also have a rutile coating, similar to the EXX12

type, but they produce a more fluid and easily removed slag (not suitable for vertical down) with a very neat and flat profile. They are generally

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Metals and Engineering 5. 12AB Pertonn

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more suited to overhead and vertical welding in an upwards direction than EXX12. They have good X-ray and impact qualities. (these qualities vary dependant on the impact grading number)The effect of moisture on electrodes

Any electrode that absorbs excessive moisture into the coating may cause one or more of the following problems: porosity excessive spatter arc instability poor weld contour undercut difficulty in slag removal cracking through hydrogen embrittlement.Storage

All types of electrode should be stored in their original packaging in a weather proof area on racks clear of the floor. They should be stored away from moistvre and high humidity and possible damage. Storage in an unheated room is satisfactory for a period of less than six months. If storing for more than six months, or if in tropical or very wet climates, all electrodes except cellulose types (EXXIO,EXXll) should be stored in a room or insulated building heated to 15C to 20C room (or ambient) temperature, but at no time more than 40C. Electrodes stored in hermetically sealed (airtight) boxes need not be kept in such an environment.

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Never tear electrode information data from the boxes. This can lead to confusion and/or improper use of electrodes.Storing electrodes

Welders are responsible for the care and handling of electrodes on the shop floor or work site. Electrodes should be kept clean and dry. Defective electrodes should not be used. Discard electrodes or which are wet or seek manufacturer's advice. Don't use electrodes showing signs of rust or of damaged coating. Only remove from the packet the number of electrodes you need for the next few hours or the immediate job in hand. This reduces the risk of contamination and waste.

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Unseal packets of electrodes just before you use them and not before.

Basic symbolsBasic symbols which are used to denote the type of weld are illustrated in

FieldSurface weld roundor Weld Convex Backing strip site Flush all shape

~

C\.symbols used

the table below. Also shown are a number of instructional to impose certain requirements

on the actual welding operation.

Welding symbols

Number of stud, plug,slot, spot or projection welds Arrow connecting reference line to joint

Basic weld symbol area

Spacing between intermittent welds

I L1J WUJ

S rS4eld

r--t~'-lf

I _ ~_ I I t I U'} Ot/) I

0 :I:o

r

/::!Fi'eld or site of weld all round

I b Ow I I m ~0:::0 I 0:::_ I I :r: ~lflJ I L __

F(N)

Tail of reference line (omitted when reference P is not used)

The standard welding symbol used to represent welds on drawings is shown below. The symbol can be used in many ways.

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note Information relating to a particular weld, such as S, (N), F, W, (M) must be placed on the same side of the reference line as the symbol for that weld.

Symbol below reference line Symbol above reference line

Application of the standard welding symbol When applying the standard welding symbol, thought must be given as to whether the actual weld is situated on the same side of the joint as the arrow or on the other side. Arrow 1 W is called the arrow side of joint X is called the other side of joint Arrow 2 Z is called the arrow side of joint 2 Y is called the other side of joint 2 Arrow joints.

1 1

1 bears

no relation to arrow 2 as they refer to different

For weld A, the basic fillet symbol is placed underneath the reference line indicating that the weld is on the arrow side of joint 1. For weld B, however, the basic fillet symbol is placed above the reference line indicating that the weld is on the other side of joint 2. 34


Wherever possible, the arrow should be positioned adjacent to the weld, as with joint 1, with the symbol underneath the reference line.

Welding proceduresIt is sometimes necessary to specify certain procedures or requirements about a weld. The standard symbol used in such cases should be provided with a tail as shown on the previous page and the information inserted where shown, for example, at P. In order to control a welding process more fully, a procedure sheet may be added to the drawing. The sheet should contain the following general information. type of material being welded; form of weld (to include plate preparation such as angle of bevel, root penetration, root radius, etc.); set-up details such as welding position, alignment, gap required; number and order of runs; electrode size, type and make (consultAS1552, Classification of Covered Electrodes); electrical supply data such as polarity, current and voltage values; preheating requirements; pre- and post-weld cleaning procedures; treatment of joint after welding; preparation and/or procedures to apply in between runs. The arrow is cranked as shown below and points towards the plate which has to be prepared. The crank is omitted when the edge to be prepared is abvious, for example, a tee but joint.

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IOrll~""\.::'::::?

~

Symbol below the horizontal reference line. This indicates that the weld is to be placed on the same side as the arrow.

Symbol above the horizontal reference line. This indicates that the weld is to be placed on the opposite side to the arrow.

~;v;a the c joint the arrow the Weld Cross Explanationothera side I 1"- bIbflush Section c side Symbol Ibead arrow on I I I Drawing weld side Drawing Application the other I thethe jointside ground of arrow side with a c) Single V butt weld sides of Filet weld on both on c) Single bevel button a) Seal bead weld at the a) Single V butt weld on

Symbol below and above the horizontal reference line. This indicates that the weld is to be placed on both sides of the arrow.

ed

I'...'f~~

Jkt1 I~~ ,bk;~~

Cs VI ~\}m LE 11a

a) Filet weld at the arrow side b

b) Filet weld on the other side b) Single V butt weld on b) Bead weld at the arrow side

the other side

36


Joint preparationThe arrow may also be used to indicate when one plate only of a joint is to be prepared in welding single bevel and single J butt joints. The arrow is cranked as shown below and points towards the plate which has to be prepared. The crank is omitted when the edge to be prepared is obvious, for example, a tee but joint.

Cranked arrow

Plate to be bevelled

Actual weld

End view

Front view

~~:~~ooeclfue~o

~m~~~~u~d

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Manual Metal Arc WeWing

Section 3 Manual Metal Arc Welding Basic WeldsAimTopractice manual metal arc welding exercises in order for you to develop the manipulative skills for striking an arc and depositing weld metal on low carbon steel plate.

Activity1. 2. 3. Read and study the resource material following. Complete the practical exercises. Ask for assistance if the information or instructions are not clear to you. 4. Ask a teacher or your supervisor to check and sign your Training Record. These are skill practice exercises which are assessed. You must reach the required standards to enable progression to the section .

5.

Safety Follow OHS workshop procedures. Protect your eyes from the welding arc and wear the proper eye protection. Wear suitable protective clothing including dry leather gloves.

45


Manual metal arc welding - basic weldsThe following instructions will provide you with basic information about material preparation, striking an arc and laying down a weld bead. The cleaning requirements for a finished weld will also be identified along with the equipment used for this task. Read them carefully before attempting the four practical exercises in this section.

Material preparationCleaning

A welded joint on low carbon steel (mild steel) requires the material to be cleaned in such a way as to remove all matter that may contaminate the weld runs (beadlbeads). This can be in the form of Mechanical or Chemical cleaning. If chemical cleaning is to be carried out it is critical that all safety factors are adhered to as chemicals may produce dangerous substances when heated by the arc. Consult the Material Safety Data Sheet (MSDS) or the manufacturer/distributor if you are not sure about using any cleaning agents.Mechanical cleaning

The weld area may be machined. This preparation will generally require minimal cleaning. If the material is flame cut or hot rolled it will have an oxide skin that will need to be removed. This will usually require grinding as wire brushing may not be aggressive enough to bring the material back to bare metal. Aggregate blasting such as sand or other particles may be also used to clean the weld area.Tools used for cleaning

The hand held power tools that are used for material removal may include: Angle grinder Straight portable grinder Die grinder Belt sander Grinding or sanding Grinding or wire brushing

46

Aleta!s and Engineering 5.12AB Perform

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Routine Manual Meta! Arc Welding

These tools can be either pneumatic (air driven) or electric. A floor mounted pedestal grinder may also be used for material removal. The practical exercise in this module will require you to use an electric angle grinder.

How to strike an arcPreparation

1.

Select a piece of steel and after material preparation place it on the work bench. Select a 4.0 mm E4112 or E4113 Manual Metal Arc electrode. Set amperage on power source to approximately amps. 165

2.

3.

4.

It is important that you get yourself into a comfortable and relaxed position when welding to counter the effects of body sway, movement restrictions and heat generated by the arc. To get comfortable you can be seated, lean against the bcnch or lean against a wall in the welding bay.

Striking the arc

1. 2.

Turn on the power source. Lightly touch the end of the electrode on to the work and you will complete the circuit and current will flow. The electrode end rapidly heats, melting sufficiently to momentarily weld the electrode on to the work. Due to the low voltage current we are using the arc will not jump an air gap (as in a spark plug). We must therefore establish an arc by first touching the end electrode onto the work and then immediately, lengthen the distance between end of the electrode and work allowing droplets of metal and flux to cross the ARC GAP(3 mm approx.) to form a molten pool.

3.

4.

47


5.

If you fail to do this, droplets will bridge the arc gap, causing a short circuit and a freezing of the electrode end onto the work. If your action is incorrect and the electrode freezes onto the work, that is becomes welded or stuck to it, a sharp backward angling of the electrode should break it free. Keep your head shield over your face, as an arc flash will occur as the electrode breaks contact.

6.

7.

Laying down a weld bead1. Once the arc has been established, reduce the arc length to about 3 mm and note that molten metal is beginning to mount up under the end of the electrode. Start moving the tip of the rod slowly away to the right, (if you are left- handed, to the left) endeavouring to maintain a molten pool approximately 8mm wide behind the arc. You will have to feed in the electrode as it burns off, maintaining a steady rate across the plate using the correct arc length. Continue to deposit a beadlbeads across the plate. Remove the slag cover and wire brush and inspect your weld. A little more practice and some of these actions will begin to happen automatically. Remember, not all people are born natural welders. Welding requires practice to gain the necessary skills to lay down consistent welds. You only obtain these skills by running lots of electrodes and concentrating on what you are doing.

2.

3.

4. 5.

6.

7. 8.

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Routine Mauual Metal Arc Welding

Weld cleaningIt is important specifications that the finished weld is of an acceptable spatter. The finished appearance additional work. and may require standard free of slag and adhering may be given in job This may need to be

ca.rried out before the final finish is added to the completed job/component. Cleaning may just require you to use a chipping hammer and a wire brush. It could also require you to use the following tools. Angle grinder Straight portable grinder Die grinder Belt sander Chisel (hand, electric, air) File Peening gun (electric, air) used to remove slag. By the removal of slag and spatter many welds on fabrication work are left as cleaned. Additional treatment such as machining, sand blasting, grinding and sanding are after treatments in the manufacturing process. that may be carried out by other personnel The practical exercises in this module will Grinding or sanding Grinding or wire brushing

require you to use a chipping hammer, chisel and wire brush.

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Metals and Engineering IndustryS.12AB Perform Routine Manual Metal Arc Welding

Practical exercise 1 - Beads on plate -

flatAim To develop the skills to deposit uniform weld beads to the standards below.Material

1 piece low carbon steel 75 x 10 x 225 mmConsumables

Mild steel electrodes 4.0 mm E4112 or E4113 at approx. 165 amps.Instructions

Check the following points: Amperage setting and heat input, position of the plate on the bench, correct method of arc striking, correct arc length, correct welding speed arid travel, electrode angles. Your teacher will demonstrate if required. 1. Obtain your MMA welding board, safety equipment (head shield, gloves), material, and consumables (if necessary) from the store. Position the plate on the bench so that a right handed operator would weld across the body from left to right (left hand opposite direction). Deposit a weld bead along the plate length, maintaining the angles as shown, and an arc gap of approximately 2-3 mm. Deposit additional runs parallel to the plate edge approximately 10mm apart. When the top surface of the plate has been covered, turn the material over and repeat the exercise.

2.

3.

4.

5.


6.

Evaluate the weld exercise and complete the procedure sheet. Submit your completed weld and procedure sheet for assessment.

7.

Economy

Materials and consumables are expensive. Use electrodes to 50 mm maximum stub length. Standards Your work should have: uniform beads with consistent, even restarts, free from slag and spatter+2

bead height 3 -1 mm.

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Procedure sheet 1 - Beads on plate - flat

Electrode

View A

~B

A~,.

11- Start

VlewB Weld current data Electrode dataSize Type Brand Name Electrode Angles Lead Lateral Rutile

Run

1

2

3

60' 80

90

Material dataType Thickness Low carbon steel

10mmComplies

Assessment

Workshop safety

54


Practical exercise 2 - Pad welds - flatAim

To deposit a pad weld on low carbon steel plate in the flat position.Safety

Follow OHS workshop procedures. Use an approved shade 10 welding glass filter. Wear suitable protective clothing to stop ray burn. Always wear your safety glasses when removing slag.Material

1 piece low carbon steel 75 x 10 x 225 mmConsumables

Mild steel electrodes 4.0 mm E4112 or E4113 at approx. 165 ampsInstructions

Check the following points. Setting of amperage and heat input, position of the plate on the bench,' correct method of arc striking and arc length, correct welding speed and travel, electrode angles. Your teacher will demonstrate if necessary. 1. Obtain your MMAwelding board, safety equipment (head shield, gloves), material, and consumables (if necessary) from the store. Outline, with chalk, a rectangular shape 40 x 200 mm. Position the plate on the bench. Deposit a weld bead along the plate length, maintaining the angles shown.

2. 3. 4.

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5.

Remove all slag from each individual weld bead before depositing subsequent runs. Each run must have a staggered stop and restart. Build up the pad to the required dimensions and on completion, evaluate your weld with the given standards. Fill in all the relevant information on the procedure sheet. If it meets the standard, submit your work for assessment.

6.

7. 8.Economy

Use electrodes down to a stub length of SOmm maximum. Standards Your work should have:+2

pad weld height 3 -1 rnm a maximum of four significant surface defects on a unit area of 40 x 150 mm with the accumulative area not exceeding the square of the plate thiclmess no adhering slag or spatter.

56


Procedure sheet i-Pad

weld - flat

First run

Subsequent runs

View A

~B

View B

Weld current data

Run

1

Electrode data Size Type Brand Name Electrode Angles Lead Lateral.. .

2

3

Material data Type Thickness Assessment Low carbon steel 10mm Complies

Workshop safety

57

Metals and Engineering Industry 5.12AB Perform Routine Manua! Meta! Arc Welding

Section 4 - Fillet Weld Joint Terms and FaultsAimTo learn the basic terminology (technical language) used to describe weld positions, areas and locations of a welded joint, and common defects and their causes.

Activity1. 2. 3. 4. 5. Read and study the resource material following. Complete the review questions. Ask for assistance if the information is not clear to you. Complete the practical exercises at the end of the section. Ask a teacher or your supervisor to check and sign your Training Record. On completion of this section you must attempt the test on this topic and reach the required level of competence before proceeding to the next section.

6.

Safety

Wear the right clothing to protect you against rays and hot metal spatter.

59

Metals and Engineering Industry 5.12AB Perform Routine Manual Metal Are Welding

Fillet weld joint terminology and faultsIt is important for you to know the terms used to describe fillet weld joints and fillet weld defects so that you are able to talk to other trades persons, clients and inspection authorities in an informed way. An understanding of the technical terminology will also assist you to get the most out of your training.

Fillet weld terminologyPositions of welds//Vertical

Horizontal Single v .,~ butt weld Intermittent fillet welds

Overhead Lap weldFillet weld,/

/

'.... Plug weld -

'-.--- Slot weld

-'--- Corner weld

Weld names

[vertic.al

\I... ~-

.]1~1 . r "--...

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Definition of a fillet weldA fillet weld is a weld of approximately triangular cross-section which is

formed in the corner between surfaces of two components.

Parts of a fillet weld

Fillet weld contours and

0--

Toe Root face Heat metal Penetration Weld metal Parent zone Fusion 12. 7. Nominal thickness thickness9. fillet) Reinforcement 11. 10. 8. Leg lengththroatzone(concave fillet) Throataffected (convex

measurements

13.

Parts of a welded structure

.

/penetration/fUSionWeld face

Parent metal

Fillet weld

61


Fillet weld dimensions

The size of a fillet weld is determined by the following dimensions. These can easily be checked with a fillet gauge. Note that the strength of a welded structure is determined by the type of metal, leg length and the effective throat thickness.

Fillet weld dimensions.

Fillet weld profiles

Weld DefectsWeld defects are either external or internal. External defects can be detected by visually inspecting the finished weld for plate misalignment, incomplete penetration, weld craters, blowholes, weld spatter and correct weld size. Internal defects can only be detected by destructive or non destructive testing, which may reveal slag inclusions, porosity, cracks and incomplete fusion or incomplete penetration.

62


Common weld defects The most common weld defects are:Undercut

A sharp groove at the toe of a ron between the weld and the parent metal or in previously deposited weld metal, due to welding. It may be continuous or intermittent. This is caused by using the wrong electrode current, incorrect operating technique angle, excessive welding

or excessive arc length.

~

~Undercut

Over roll (overlap)

Weld metal at the toe of a weld which covers the parent metal surface but is not fused to it. It is caused by overflowing molten weld metal on the surface of unmelted parent metal which leaves an unwelded area. This is or too slow welding speed, or by using caused by using too Iowa current too large an e!ectrode.

63


Misalignment

Misalignment is any variation from line or dimension of a welded joint. It is caused by faulty setting up of job, distortion or lack of tack welds.

Misalignment

Incomplete

penetration

Incomplete penetration may be classified as an internal or external weld fault. Incomplete penetration is the failure of the weld metal to fill and fuse the root of the joint. It is caused by faulty preparation of work, using too Iowa welding current or poor operating technique.

Incomplete penetration

Slag inclusions

Slag inclusions are non-metallic particles trapped in the weld metal. They may weaken the weld joint. Inclusions result from not removing slag from previous runs, using too Iowa current or using too long an arc length.

Inclusions

64

Metals and EngIneering 5.12AB Perform

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Porosity

Gaseous substances such as oxygen or nitrogen trapped in the weld metal leave a cluster of small holes in the weld. It is caused using wet or damp electrodes, welding over coated surfaces, over painted oily or greasy surfaces or by using the wrong type of electrode.

Cracking

A variety of different types of cracks may occur in the welded area of fabricated products. Identifying the type of crack helps to isolate the possible causes. Causes are using wrong type of electrode, not applying preheat to crack sensitive steel, using damp or wet electrodes or welding over oil, grease or a plated metal surface .

/I..

.....

Lack of fusion

Incomplete fusion between weld metal and weld metal or weld metal and parent metal is caused by not enough amperage, incorrect joint preparation and incorrect welding technique.

Lack of fusion

65


Undersized and oversize welds

Welded joints are designed by structural

engineers

to carry loads safely. weld might

The size and type of weld depends on its use. An undersized not be strong enough to carry the load it supports.

A weld that is reinforced

(over welded) too much can make other sections of the work too rigid and cause them to crack or break. You will be asked to weld to the designer's specification. For example

a 6 mm fillet weld requires a 6mm leg length and a 4.2 mm throat thickness a butt weld requires an even or slightly curved surface. You may not be given the weld size for all jobs. If no weld size is specified, deposit the weld in proportion to the plate thickness. For example:

a 10 mm plate requires a 10 mm weld thiclmess. Butt welds should always be built up to the thickness of the parent metal.

Oversize

Correct size

"\

\

Undersize

Weld assembly (undersized welds)

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Workshop testsThese are only some of the tests which call be carried out to check the weld quality. Visual Youcan do a visual check for external weld defects. Internal ones can't be seen.

Fillet break A fillet break shows satisfactory fusion, penetration, and inclusions or porosity. Summary of weld defects and how to fix them When preparing the plate, check that you have: correct edge preparation clean/smooth surfaces correct plate alignment. When welding, check that you have: correct electrode correct current (amperage) correct speed of travel

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correct arc length correct operation (welder). When checking the electrode for condition, check for damp or damaged electrodes. When inter-run cleaning remove all slag, rust, undercut, and excess weld spatter before depositing the next pass.

68

Metals and Engineering 5. 12AB Perform Routine

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Practical exercise 3 - Fillet weld, single run - horizontalAim

To deposit 6 mm fillet weld in the horizontal position on 10 mm low carbon steel plate.Note

This is a skill practice exercise which is assessed. You must reach the required standards to enable progression to the next section. Safety Youmust wear eye protection . Make sure that the centre of the press ram and the highest point of the exercise are in line when breaking welds.Material

2 pieces low carbon steel 75 x 10 x 225.Consumables

4 mm 4112 or 4113 electrodes at 160 to17S amps approximately.Instructions

Your teacher will demonstrate. 1. Wire brush the material to remove surface rust and loose scale. Tack both ends of the plate to ensure metal to metal contact. Complete approximately half the weld, stop, remove slag, restart and finish the weld. Remove all slag and spatter and submit the exercise for visual inspection.

2.

3.

4.

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5.

Break the weld and resubmit the exercise for internal inspection.

6.

Relocate the plates for further practice using all edges as shown. Evaluate the weld exercise and complete the procedure sheet. Submit your work for assessment.

7.

8.Economy

Consumables and materials are expensive. Relocate plates for maximum use. See chart (on earlier page) for suggested plate positioning sequence to obtain four or more fillet welds from one material unit. Use all electrodes down to a maximum stub length of 50 mm and return unused material to the store. Standards Your work should have: correct alignment and assembly smooth regular weld contour angular distortion 0 to 5 a maximum of two significant weld defects per 250 mm of weld length with an accumulative area of less than twice the square of the plate thickness weld size 8 mm complete fusion for the length of the weld joint.

79


Procedure sheet 3 - Fillet weld, single run horizontal

View A Weld current data

ViewB Electrode data Size Type Brand Name Electrode classification Angles Lead Lateral

1 2

3

Material data Type Low carbon steel Thickness 10 mm Assessment Alignment and assembly Angular distortion Surface finish Weld size Surface defects Complete fusion Workshop Safety No. of units completed to standard

Complies: Complies: Complies: Complies: Complies: Complies: Complies: Complies:

80


Practical exercise 4 - Fillet weld, 3 run 2 layer - horizontalAim

To use the fillet welding technique necessary to deposit an 8 mm three run, two layer fillet weld to the requirements below.Material

2 pieces low carbon steel 75 x 10 x 225Consumables

Mild steel electrodes F4112 or E4113 at 160 to 175 amps approx.Instructions

Your teacher will demonstrate. 1. Wire brush or grind the weld fusion faces to remove the rust and mill scale. Tack both ends of the plate ensuring metal to metal contact with no gap. Tack only on the ends or side to be welded. Complete approximately half the first run, stop, remove slag, and examine the weld profile. Finish the run and subsequent runs using the sequence illustrated with at least one staggered stop and start per run. Submit the exercise for visual inspection then fracture the weld and resubmit it for internal inspection. Relocate the plates for further practice using all edges as shown. Evaluate the weld exercise and complete the procedure sheet. Submit your work for assessment.

2.

3.

4.

5.

6.

7.

8.

81

Metals and Engineering IndustryS.12AB Perform Routine Manual Metal Arc Welding

Economy

Consumables and materials are expensive. Relocate plates for maximum use. See chart (on earlier page) for suggested plate positioning sequence to obtain four or more fillet welds from one material unit. Use all electrodes down to a maximum stub length of 50 mm and return unused material to the store. Standards Your work should have: correct alignment and assembly smooth regular weld contour angular distortion 0 to 5 a maximum of two significant weld defects per 250 mm of weld length with an accumulative area of less than twice the square of the plate thickness weld size 8 mm complete fusion for the length of the weld joint.

82

Metals and Engineering Industry 5.12AB Petform Routine Manual Metal Are Welding

Procedure sheet 4 - Fillet weld, 3 run 2 layerhorizontal

Weld current data Amperage used

Run

1 2

Electrode data Size Type Brand Name Electrode classification Angles Lead

Lateral

3

Material data Type Thickness Assessment

Low carbon steel 10 cm Complies

Workshop safety

Complies

83


Practical exercise 5 - Outside corner fillet - horizontalAim

To deposit a multiple nm corner weld in the horizontal position using fillet welding techniques to the requirements below.Safety

Always wear safety glasses when chipping slag deposits away from the weld.Materials

Material from the single or 3 run fillet (crucifixes) exercises or 2 pieces 25 x lOx 225 111111 low carbon steel.Consumables

Mild steel electrodes E4112 or E4113 , 3.25 m at approx 120-130 amps. Mild steel electrodes E4112 or E4113 4.0 mm at approx 160-175 amps.Instructions

Your teacher will demonstrate if required. 1. A-ssemble and tack plates using a suitable spacer to maintain root gap. Position the plates and deposit approximately 50 mm of the root run. Examine the bead shape and penetration continuing the weld. before

2.

3.

4.

Completely fill the remainder of the weld using 3.2 diameter electrodes and a logical weld sequence. Seal the reverse side with a 6 mm horizontal vertical fillet weld.

5.

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6. 7.

Add additional plates as required and repeat the exercise. Evaluate the weld exercise and complete the procedure sheet. Submit your work for assessment.

8.Economy

Maximise the use of electrodes and return all unused material to the store. Standards Your work should have: correct alignment and assembly smooth regular weld contour angular distortion00

to 5

a maximum of two significant weld defects per 250 mm of weld length with an accumulative area of less than twice the square of the plate thickness weld size 8 ~6mm complete fusion for the length of the weld joint full radius weld.

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Procedure sheet 5 - Outside corner fillet horizontal



Lateral

Material data Type Thickness Assessment Complies

Workshop safety

86


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Practical exercise 6 - Fillet weld horizontalAim To fillet weld 3 mm low carbon steel sheet assembled in the horizontal position to the requirements below. Safety Always use tongs to position tacked and welded work. Never leave hot work unattended in the workshop. Material 6 pieces low carbon steel 50 x 3 x 225 mm. Consumables Mild steel electrodes E4112 or E4113 2.5 mm at approx 85-95 amps. Mild steel electrodes E4112 or E4113 3.25 mm at approx 110-115 amps. Instructions Your teacher will demonstrate. Students must attend this demonstration before beginning the exercise. 1. Clean, assemble and tack weld at three locations for each joint. Use E4112 electrodes and stop each run at least once. Weld both sides of the horizontal fillet. Repeat the exercise with E4113 electrodes.

2. 3. 4.

87


Economy

Materials and consumables are expensive. use electrodes down to a maximum total length of 50 mm. Standards Your weld should have: correct alignment and assembly smooth regular weld contour angular distortion 00 to 50 a maximum of two significant weld defects per 250 mm of weld length with an accumulative area of less than twice the square of the sheet thickness. weld size equal to the sheet thickness ::.~ mill complete fusion for the length of the weld joint.note

Watch for these points. Distortion tack at regular intervals, assembly and 'fit up' of cornerjoint.

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Industry


Procedure sheet 6 - Fillet weld - horizontal

Outside corner weld



Lateral

Material data Type Thickness Assessment Complies

Workshop safety

89

Metals and Engineering Indust/) 5.12AB Perform Routine Manual Metal Arc Welding

Section 5 - Butt Weld Terminology and FaultsAimTo learn the technical terms used for butt welds and to be able to identify typical weld defects.

ActivityL 2. 3. 4. Read and study the resource material following. Complete the review questions. Ask for assistance if the information is not clear to you. Ask a teacher or your supervisor to check and sign your Training Record. On completion of this section you must attempt the test on this topic and reach the required level of competence before proceeding to the next section.

5.

Safety Wear the proper clothing to protect your skin and eyes. Do nottry to take short cuts or risks

90


Butt weld terminology and faultsIn this section you will learn about the different types of butt welds and how to identify some of the faults which can occur in butt welds. Butt welds are used to join metal products such as sheet, plate, rolled and pressed sections. This type of joint has the advantage of giving high strength without changing the profile of the structure. Industrial uses for butt welds include: boiler and pressure ship building earth moving equipment aircraft and submarines. Butt weld joints can be designed for full penetration welding to give vessel construction

maximum strength or for partial penetration strength of the joint is not so important.

welding in places where the

Weld preparationReinforcement Toe Parent metal

Fusion zone

Root penetration

Weld components Joint edges have to be prepared before plates are welded together. Joint or edge preparation is essential for complete fusion and penetration.

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\

~

;

Root face: fa supporf fhe fltst run of weld

-JLWeld preparations multi-run fillet welds Double butt welds and U V preparations Single butt welds less difficult to distortion. maximum =strength. moreheat less prepare. On thick plate

~ _~_=========::~Roof gap: to allow complefe weld penetration

use gouge and U preparations. Less for needweld metal flametopreparations runweld less double V by than V cutting or machining. = back to done or joint a backing but are usually balance deposit minimise distortion.

{.~

'j(~L

)

Plate thickness

DCJ DCJ

92


Preparation typesThere are several preparation types and details are given below.

Closed butt jointThis is used when the edges do not need preparing. suitable for sheet up to 3 mm thick. They are placed

close together and single or double welded. The closed butt joint is

j~ -~-

Sr [Open butt joint

I~--~Sof material. An open butt

This is used when the edges do not need preparing. They are separated slightly to allow fusion of the full thickness joint is suitable for material up to 5 rom thick.

r~mm

~

JI -1L-'.S-2.S

s

Single V butt jointThis is commonly

used on material up to 12 rom thick.

1.5mmm~JL

?2\/,--~?1.5

o

mm

~12m~

f

93

Metals and Engineering S.12AI3 Perform Routine

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Manual Metal Are Welding

Double V butt jointThis is used on plate 12 mm to 38 mm in thickness are welded. when both sides

Single bevel butt jointUsed only when one member of the joint can be prepared a T joint. as in the case of

~5 ~Minimum

",

15M~imu~JLSingle U butt jointThe single U butt is used as an alternative to single V butt joint.

~inimum r-\1-'

\ \1I

~ __

r

Radius5mm Minimum

t

-~-UPto . II 3 mm Maximum--i+-- 3 mm

;'-1=V;r-

25mmtJ

94

Metals and Engineering Indnstry 5.12AB Perform Routine Manual Metal Arc Welding

Double U butt jointThis is used on material done from both sides. over 2S mm thick where welding can be

iO~

Minimum

Ll====---"~ 3 mm Maximum

___

"/_1_r -===RadiUS 5 mmMitm3 mm Up to 25mm

L L ;

r

When you need to butt weld two sections of different thickness, you should taper the thicker one to match the other. The length of the tapered section should be at least three times the difference in the thickness between the plates. This type of butt weld is used to join dished ends to pressure vessels.

Uneven section" butt joint

95

Metals and Engineering 5.12AB Periorm

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Weld defectsCommon weld defects are detailed below. Excesspenetration Definition Too much weld metal extending through the root of the weld .

---

u

u'-etration

Causes are: incorrect preparation amperage too high incorrect welding technique. Incomplete penetration Definition Failure of the weld metal to extend into the root of a joint.

."

;: :'-':.~ . .. ",:.,::" "

7S'//

..-

.

~ :-.. ;:, ..... ---------

~.,.

'1-'-

M'.

.

"_;1

Incomplete penetration

Causes are: incorrect preparation amperage too low arc length too long.

96


Lack of fusion Definition Incomplete fusion between weld metal and weld metal or weld

metal and parent metaL

)Lack of fusion

Causes are: not enough amperage incorrect joint preparation incorrect welding technique.Inclusions Definition Slag or other foreign matter trapped during welding.

Causes are: faulty joint preparation not enough amperage poor cleaning of prior runs.

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Porosity Definition A group of gas holes in the weld metal.

"

":.'? '. O';'~< Porosity ~., ~~t'

.. '~' ...,':.

..,

Causes are: damp or old electrodes composition of parent metal incorrect electrode type.Cracking

Definition Discontinuity produced from tearing of the weld metal while in a plastic condition when hot or a fracture when cold.

HAZ cracking

Causes are: insufficient weld deposit insufficient pre-heat incorrect electrode.

98


UndercutDefinition A groove or channel in the parent metal at the toe of the weld.Undercut

Causes are: too much current welding too fast incorrect welding technique. OverrallDefinition A section of unfused metal extending past the toe of the weld.

~verrOI1~w/ove~OIlCauses are: electrode too large welding speed too slow incorrect electrode angle.

99


Misalignment Definition Any variation from line or dimension of a welded joint.

Misalignment

Causes are: incorrect weld procedure careless preparation too few tack welds. Incompletely filled joint

~

~comPletelY filled joint

~~----( ~.=Causes are: not enough weld metal welding too fast too few beads.

-~

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The principle of expansion and contraction in a metalMetals expand when heated and contract when cooled. For example, a piece of low carbon steel, if not restrained in any way, will increase its dimensions in all directions for every degree Celsius the temperature rises. On cooling, the steel will return to its original size.

Angular distortionThere is distortion when unequal contractional forces cause angular change in the parent metal position.

j~ Outwardby expansion caused movement

i

Inward movement caused by contraction

Transverse distortion by butt weld

6

4

2

'3

5

7

Tack weld sequence

101

Metals and Engineering lndustry S.12AB Perfonn Routine Manual Metal Arc Welding

Practical exercise 7 - Butt weld, flat sheet steelAim

To deposit single run butt welds in the flat position on 3.0 mm low carbon sheet steel.Materials

4 pieces 40 x 3.0 x 150 mm low carbon flat bar.Consumables

Mild steel electrodes E4112 or E4113 2.5 mm at approx 85-95 amps. Mild steel electrodes E4112 or E4113 3.25 mm at approx 110-115 amps.Instructions

Your teacher will demonstrate. 1. Assemble and tack weld sheets using the sequence illustrated. Position the plates with a sligh t slope and weld approximately 50 mm of the joint. Examine weld profile and penetration before completing the weld. Complete the weld and submit for inspection. Cut sheets and relocate for further practice as illustrated. Evaluate the weld exercise and complete the procedure sheet. Submit your work for assessment.

2.

3.

4. 5. 6.

7.

108


Economy Cut and relocate sheets for maximum the store. use. Return all unused material to

StandardsYour work should have: correct alignment and assembly

smooth regular weld contour weld penetration angular distortion for a minimum00 to 50

of 20% of the weld length

a maximum

of two significant

weld defects per 250 mm of area of less than twice the

weld length with an accumulative square of the plate thickness.

109

Metals and Engineering S.12AB Perlorm Routine

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Procedure sheet 7 - Butt weld, flat sheet steel

Weld current data Amperage used 1.6mm 3.0mm

Electrode data Size Type Brand name Electrode classification Angles Lead Lateral

Material data Type

Thickness

Assessment

Workshop safety

110

arc welding

Documents

welding arc

depositing weld metal

manual metal arc weldingaimto

manual metal arc wdding

faults butt weld terminology

welding symbols

activity butt weld terminology

welding machines