Weld using MMAW process

• Routine MMAW in this unit is intended to apply in a manufacturing or maintenance environment where welding is not required to meet Australian Standards or other welding codes, licensing requirements, Occupational Health and Safety regulations relating to certificatedcoded welding. • Fillet and butt welds in all positions would typically be performed on low carbonmild steels. • Weld preparation would be minimal and generally restricted to cleaning, using files and grinders. • In circumstances where welding is required to meet Australian Standard 1554 General Purpose or equivalent codes, Occupational Health and Safety regulations andor licensing requirements then Unit 5.15A (Weld using manual metal arc welding process) should be selected.

MEM05012 & MEM05015 Weld using MMAW process

Introduction

Student organiserAssessment

Module sections

Section 1: Operating principles

Section 2: Pad weld shaft - rotated

Section 3: Pad weld plate - horizontal

Section 4: Fillet weld joint terminology and faults

Section5: Fillet weld - single run - horizontalSection 6: Fillet weld - 3 run 2 layer - horizontal

Section 7: Fillet weld - angle to plate - horizontal

Section 8: Corner fillet weld - horizontal

Section 9: Plug and slot welds

Section 10: Fillet weld - steel sheet - horizontal

Section 11: Fillet weld - vertical

Section 12: Fillet weld - rolled section to plate - vertical

Section 13: Fillet weld - steel sheet - vertical

Section 14: Butt weld joint terminology and faults

Section 15: Butt weld - 6 mm low carbon steel - flatSection 16: Butt weld - rolled steel section - flat

Section 17: Butt weld - steel sheet - flat

Answers to review questions

Sample assessment (theory)

Answers to sample assessment (theory)

Terms and definitions

3

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NFO] Manual MetalArc Welding] (MMAWJ) is the first in a specialisedseries of

modules on welding processes NFO1 Manual Metal Arc Welding 1 aims to provide you

with the knowledge and skills to weld a range of pad, fillet and butt joints to AS 1554

GP Specifically, NFO1 Manual Metal Arc Welding 1 enables you to:

outline the principle of operation for MMAW, relate the process to environmentaland personal safety requirements and discuss the safe operation of the process

o demonstrate pad welding to the standard specified

• demonstrate fillet welding to the standard specified

o demonstrate butt welding to the standard specified

identify common weld positions, weld joints and describe the methods of platepreparation

identify weld defects related to rutile electrode applications on fillet and butt jointsand discuss appropriate methods of reducing the incidence of these defects

The flow diagram below shows how Manual Metal Arc Welding 1 fits into the rianual

metal arc welding stream

Welding andThemial Cutting

NBBO9

Manual MetalWelding 1NFO 1

Material Science NFI5

Manual Metal Arc

The moduleNFOJ Manual Metal Arc Welding 1 is divided into sections that aredesigned around the techniques for welding low carbon steel sheet, plate and rolledsections.

We recommend that you complete each Section before moving on to the next, and thatyou study the theory before you attempt the practical work

Included in this workbook are a number of practical exercises (Skill practices) that willhelp you learn how to weld in the flat, horizontal and vertical positions You will alsolearn to use these techniques in industrial situations

Review questions

The review questions will help you understand and summarise what you are learning

and to revise the important points in each theoretical section They are not tests or

exams The answers to the review questions are at the back of this workbook

Terms and definitions

A short list of Manual Metal Arc Welding terms and their definitions is included in thisworkbook Add to this list, the terms that you learn in this module

Sample theory tests

A sample theory test is provided to give you an appreciation of the questions you will berequired to answer to pass the theory component of this module

Safety

Working safely is very important and an essential requirement for workers in the metaland engineering industries During this module you will learn to recognise weldingrelated hazards

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2 Pad weld shaft - rotated - Skill practice 1 2 hrs

3 Pad weld plate - horizontal - Skill practice 2

Assessment event I (practical)

1 hr 30 mins

30 mins

4 Fillet weld joint terminology and faults 1 hr

5 Fillet weld - single run - horizontal - Skill practice 3 2 hrs

6 Fillet weld - 3 run 2 layer - horizontal - Skill practice 4 3 hrs

7 Fillet weld - angle to plate - horizontal - Skill practice 5

Assessment event 2 (practical)

1 hr 40 mins

20 mins

8 Corner fillet weld - horizontal - Skill practice 6

Assessment Event 3 (practical)

1 hr 40 mins

20 mins

9 Plug and slot welds - Skill practice 7

Assessment event 4 (practical)

3 hrs 30 mins

30 mins

10 Fillet weld - steel sheet - horizontal - Skill practice 8

Assessment event5 (practical)

1 hr 40 mins

20 mins

11 Fillet weld - vertical - Skill practice 9 2 hrs

12 Fillet weld rolled section to plate - vertical - Skill practice 10

Assessment event 6 (practical)

1 hr 40 mins

20 mins

13 Fillet weld - steel sheet - vertical - Skill practice 11

Assessment event 7 (practical)

1 hr 40 mins

20 mins

15 Butt weld - 6 mm low carbon steel - flat - Skill practice 13 2 hrs

16 Butt weld - rolled steel section - flat - Skill practice 13

Assessment event 8 (practical)

2 hrs 40 mins

20 mins

17 Butt weld - steel sheet - flat - Skill practice 14

Assessment event 9 (practical)

1 hr 10 mins

20 mins _-

Assessment event 10 (theory)

To pass this module you must show competency in relation to underpinningknowledge (theory), as well as demonstrate that you can weld to AS 1554 GP orequivalent in the flat, horizontal and vertical positions (practical)

D The assessment scheme for this module comprises nine practical tests and onetheory test

The practical tests included in this workbook are based on material covered in thefollowing module sections

Section 3 Pad weld plate - horizontalSection 7 Fillet weld - angle to plate - horizontalSection 8 Corner fillet - horizontal

Section 9 Plug and slot weldsSection 10 Fillet weld - steel sheet - horizontalSection 12 Fillet weld - rolled steel section to plate - verticalSection 13 Fillet weld - steel sheet - vertical

Section 16 Butt weld - rolled steel section - flatSection 17 Butt weld - steel sheet - flat

The theory test included in this workbook is based on material covered in thefollowing modules sections

Section 1

Operating principlesSection 4

1 hour This section covers the operating principles, equipment,

30 minutes consumables and safety requirements for general purpose welding

using the manual metal arc welding process

Objectives

At the end of this section you will be able to:

revise the hazards directly related to the use of manual metal arc weldingequipment

o list the electrical safety requirements

° secondary and primary cablescurrent path

0 outline the setting up and operating procedures of MMAW plants

0 describe the following terms

• open circuit voltage

• arc voltage

0 define duty cycle and apply it to manual metal arc welding machines

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El state the current range for2.5, 3.2 and 4 mm diameter electrodes

El discuss the function and industrial application of rutile electrodes

• E4112

• E4113,

El discuss the storage and care requirements for rutile electrodes

Safeiy

• Avoid electric shocks

• Weld in well ventilated areas

• Wear protective clothing

• Protect your eyes from rays

NFOI Manual Metal Arc Welding I

Voltage is the unit of electrical pressure The voltage at the terminals of an alternating

current (a.c.) welding machine is never more than 80 volts for safety reasons Thiselectrical pressure (or force) is responsible for the current flow in a welding circuit

Current

Amperage (current) is the measurement of the electron flow through an electricalconductor An ampere can be described as a unit quantity of electricity passing through

a given point per second This is similar to the rate water flows through a pipeline

The manual metal arc welding process

In this process an arc is struck between a consumable flux coated electrode and the workpiece The heat of the arc melts the parent metal and causes the electrode tip to melt offand form a weld bead

Hazards

Working with electrical equipment can be hazardous You must take proper precautionsand follow the set safety procedures

Electric shocks: low voltage

Electric shocks are possible on the secondary (low voltage) side of the welding circuit.They may be caused by:

(a) 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 riskand wear dry leather gloves

(b) Working in a very humid climate or rainy weather - a shock may be felt when

changing electrodes Keep the electrodes and gloves dry

Electric shocks: high voltage

High voltage shocks shouldntt happen if:

welding machines are maintained by licensed electrical tradespersons

NFOI Manual Metal Arc Welding I

you never interfere with the inside parts of the welding machines

Symptoms of electrical shock

Electric shock often stuns, but doesn't kill However, when electricity passes throughthe body it causes muscles to contract This can stop your heart beating Electricity canalso cause serious bums

Fumes

Causes offumes

•

The production of oxides and nitrous gases

• Incomplete combustion or oxidation of nitrogen from the atmosphere

Dangerous fumes

Gases, dusts and vapours are given off during welding They can cause:

• Asphyxiation because the oxygen has been used up in the work

area (common in confined spaces)

it is generated by the passage of an electric current across an arc gap

The electric arc (about 6000°C) generates the heat to melt and fuse the metal surfaces

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example, copper and aluminium are very good conductors while cast iron and stainlesssteel are poorer conductors.

Radiation

Radiation is the transfer of heat through space by wave motion No actual contact isneeded All bodies at a higher temperature than their surroundings radiate heat Forexample, the sun radiates heat energy in the form of cosmic rays and an electric radiatortransfers heat through space across a room

Electrical safety Protection against hot ,neta4 heat and arc rays

HelmetMolten droplets have a way of getting into boots

You can avoid this by wearing properprotective clothing and footwear Whenwelding out of position, wear spats overyour boots and under the overall's legs

Full protective clothing

Filter lenses

Filter lenses are specially designed glass lenses to filter out harmful rays and allow you

to see what you are welding without causing damage to your eyes Filters come indifferent shade numbers, according to the current range or type of welding

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Gaiters

Leatherapron

Gauntlets

SpatsLeatherjacket

Wear a welding shield or helmet to protect

yourself 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

glass

Helmets

Filter

Maintenance on welding equipment

Before carrying out any maintenance on electrical equipment, it is important that you

first switch off the power and remve the plug If there is no plug available, lock off the

machine or danger tag the isolator switch

Transformer

Never do maintenance work inside the cabinet of a welding machine This is the

responsibility of a licensed electrician

Operators can care for the machine by:

Keep terminals clean and tight to ensure that the current will flow freely If you do not

keep the terminals in good condition, you may get arcing andlor overheating of the

terminal and lug connections This can lead to fire or unreliable welding conditions

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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

used duty cycle (refer to Australian Standard AS 1995 on welding cables for the cable

size ratings)

Joints

Loose joints or bad contacts cause cable, clamps and other parts of the welding plant tooverheat and may give you unstable arcing Use properly designed cable connectorswhen you make any joints in cables Make sure that good electrical contact is madewhen you connect cables to the power source, electrode holder and the return clamp

Electrode holder

The holder should be relatively light, comfortable to hold, fully insulated and sturdyenough to withstand the wear and tear from constant use The holder should be rated towithstand the maximum current required for the activity

Return clamp

This is fastened to the work or to the workbench to complete the welding circuit Springpressure and screw type clamps are normally used Magnetic type clamps are alsoavailable

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Insert electrode

Insulated and tighten

to grip electrode

Electrode holders

Screw clamp Cable•

Cable

Spring loaded

Work cable

, attachments

Cable attachments

Safeiv

Protect yourself by wearing the following safety clothing

• Overalls or work clothes

• Leather apron andlor coat

Welding 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 thearc You should also put up signs to warn people that you are welding

Welding machines

Alternating current ('a.c.) welding machines

Alternating current welding machines are transformers which step down line voltage

(220/240 or 415/440 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 typeand size of electrode

Transformer welding machines are less complex and slightly less expensive than othertypes

Direct current (d.c.) welding machines

The direct current output may be supplied by a transformer/rectifier or a generatorpower source

Transformer/rectifiers

An efficient and reliable transformer/rectifier is a machine designed to transform a.c.input current to d.c output current suitable for welding Transformer/rectifiers have nomoving parts and like the transformer are quiet to operate, convenient and cost less than

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Student Workbook May 1998

motor generator units If an a.c current is needed from this type of machine, all theoperator has to do is to select the a.c output switch.

Transformer/rectifiers are often designed to provide either d.c or a.c outputs d.c isnormally preferred for high quality work because of its greater arc stability, but a.c may

be required at highercurrents to avoid arc blow

Portable light duty

a.c transformer sets d.c motor generator sets

Portability These machines generally Most modern types have features

consist of a static step-down that allow portability (especiallytransfonner and they are the self contained types) Theyconsidered as stationary types have an undercarriage fitted with

Efficiency 70-90 per cent electrically 40-60 per cent electrically

efficient Many multi operator efficient but some modern typessets give higher efficiency compare with alternating current

efficiency

by a simple reversal of a switch(d.c - or d.c.+)

Arc blow

current and is difficult to controlabove 300 amperes

Maintenance As there are no moving parts to Revolving and wearing parts add

be considered, maintenance to running costs

costs are very low

Initial costs Cheaper plant as less More costly due to generator and

construction is involved, motor construction

Electrodes Restricted to the use of Suitable for all types of

electrodes that are suitable for electrodes

alternating current only

Running costs Cheaper running costs due to the Added costs due to the use of

use of an installed power supply electric motors or internal

combustion engines

Voltage Constant open circuit voltage A variation of open circuit

selection of electrode type andwelding technique

Arc length

_

Limited arc length Greater tolerance in arc length

due to the characteristics of themachine

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NFOI Manual Metal Arc Welding I

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Power source terminals and polarity Electrical connections for a welding machine are illustrated below.

Open circuit voltage (no current flowing)

Mains voltage

415 or24OV

Arc voltage (current flowing)

Output terminals on a.c machines are markedelectrode and work.

On a d.c machine, the terminals are marked positive (+) and negative (-) except in thecase where the polarity can be changed by means of a polarity reversing switch In suchcases, the terminals are markedelectrode andworkwith electrode terminal polarityindicated at the polarity switch

Most electrodes designed for d.c operate on d.c electrode terminal positive (+) whilesome types of electrodes should be operated on d.c electrode negative (-) Refer to themanufacturerts instructions for polarity selection

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Welding cables

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

Cable connections (secondary circuit side)

Open circuit voltage - arc voltage

Welding machines may supply direct current (d.c.) or alternating current (a.c.) to theelectrode a.c transformers and d.c generators supply only one type of current, butmany transformer/rectifiers can be switched between a.c and d.c output

a.c power supply is used more often because the cost is lower and the welding

machines are simpler in design However, d.c current has some advantages The d.c arc

is much more stable with certain types of electrodes, and is suited for welding

sheetmetal Engine driven d.c models provide welding power where there are no

electrical supply lines available for example, on site work

Welding machines are designed to control the current output despite variations in arclength caused by accidental or deliberate movements by the operator For example, tocontrol the weld pooi, the operator may increase the arc length which will greatly

increase the voltage across the arc and slightly decrease the welding current

The open circuit voltage (OCV) is located and measured at the power source terminalswith the machine switched on, but no welding current flowing The OCV must be highenough to establish an arc, but not so high that there is risk of dangerous electric shock

The welder makes the arc by striking the tip of the electrode on the work to cause amomentary short circuit This is at the point on the graph where VO (see below) Withcurrent flowing, the electrode is drawn away by the welder to establish the arc Theamperage and voltage for a typical arc length are shown at Point x For a longer arc

NFOI Manual Metal Arc Welding I

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Student Workbook May 1998

length, there is significant increase in arc voltage and a small decrease in weldingcurrent (Point y) The welding machine is designed to avoid noticeable changes incurrent output when the welder varies the arc length.

Rating ofpower sources

Australian Standard AS 1966 rates the output (duty cycle) of electric arc welding powersources The machines are classified according to the type of service for which they aredesigned for example, continuous duty, heavy duty, light industrial or limited outputcycles The standard defines each of the classes according to the output (load currentand load voltage) needed for a nominated duty cycle

A welding machine's duty cycle is expressed as a percentage The duty cycle indicates

the percentage of time that the machine can operate at full current in any 5 minute;

period without overheating For example, a machine rated as having a 60% duty cycle

can be used at its maximum output for 3 minutes in any 5 minute period 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 ratedoutput 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 range

Selection of electrode size welding current

The welding operator must follow the manufacturer's recommendations on the range ofcurrent for different types and sizes of electrodes The following table gives sometypical electrode sizes and welding currents

Typical current ranges for the electrode classifications

Electrode

E4110 E4111

E4112 E4113

a EXXJ3 Electrodes

EXX13 electrodes' coating is rutile, similar to the EXX12, but they produce a morefluid and removable with a very neat and flat profile They are generally more suited tooverhead and vertical welding in an upwards direction than EXX12 They have goodX-ray and impact qualities

The effect of moisture on electrodes

Any electrode that absorbs excessive moisture into the coating may cause one or more

of the following problems

Storage in an unheated room is satisfactory for a period of less than six months Formore than six months or in tropical or very wet climates, all electrodes except cellulosetypes (EXX 10, EXX 11) should be stored in a room or container heated to 15° C to 20°Croom temperature, but at no time more than 40°C Electrodes stored in hermeticallysealed (airtight) boxes need not be kept in such an environment Keep electrodes inoriginal packets for identification purposes

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Storing electrodes

Responsibility

Welders are responsible for the care and handling of electrodes in the workplace

Condition

Electrodes should kept clean and dry

Deft dive electrodes

Do not use electrodes with damaged coatings Discard electrodes which are wet or seekthe manufacturer's advice Do not use electrodes showing signs of rust

Number of electrodes

Only remove from the packet, the number of electrodes you need for the next few hours

or for the immediate job in hand This reduces the risk of contamination and waste

Open ing:of containers

Unseal packets of electrodes immediately before you use them

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A welding process operates for 4 minutes of a 5 minute cycle State the duty cycle

appropriate for that welding process

4

State the welding current type (a.c or d.c.) for the following

(a) A current which enables polarity selection

(b) The current supplied from a transformer

(c) The current supplied from a rectifier

(d) •The current supplied from a generator

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Review questions

5.

State the names of the harmful rays generated by the electric arc and list their effects

on the human body

23May 1998

Identify the parts of a typical welding circuit by labelling the parts on the diagram shown below

Review questions

8

State the name of one weld defect that can occur if moist electrodes are used.

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May 1998

2 hours This section develops your knowledge and skills to build up a pad

weld on low carbon steel solid round bar

Objectives

At the end of this section you will be able to:

fl use pad welding techniques to build up 10 mm thick low carbon steelshaft to the following requirements

a smooth regular pad deposit 3 +2 -l mm high

o a maximum of four significant surface defects with an accumulative

defect area of less than 200 mm2

Li record the weld procedure

0 follow Occupational Health & Safety workshop procedures

Safety

You must wear eye protection

Make sure the work is cool before touching it with your bare hands

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Procedure sheet Pad weld shaft - rotated

Sketch welding runs on diagram

Complete the control data table below

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NFOI Manual Metal Arc Welding I

29 Student Workbook

A

Welding sequence View A

Skill practice 1 Pad weld shaft

-rotated

IF IN DOUBT ASK THE TEACHER

Objective

To use pad welding techniques in the workshop, to build up the surface

of a shaft to the requirements given below.

1 Draw chalk guidelines to indicate weld runs 1, 2, 3, 4.

2 Deposit the first run, then rotate the bar 1800 to deposit the second run in a flat position.

5 Deposit pad welds on both ends of the bar.

6 Evaluate the weld project and complete the procedure sheet.

7 Submit the weld and procedure sheet to the teacher.

Material and consumables are expensive Use electrodes to a stub length of 50 mm maximum.

Section 3: Pad weld plate - horizontal

DURATION

1 hour This section develops your knowledge and skills to build up a pad

30 minutes weld on low carbon steel plate in the horizontal position

Objectives

At the end of this section you will be able to:

El build up a pad weld on low 10 mm thick carbon steel plate to thefollowing requirements

• smooth regular pad deposit 3 +2 -1 mm high

• a maximum of four significant surface defects with an accumulativedefect area of less than 200 mm2

El record the weld procedure

El follow Occupational Health & Safety workshop procedures

Safety

• You must wear eye protection

• Wear suitable protective clothing

• Follow correct safety procedures

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Procedure sheet Pad weld plate - horizontal

Sketch welding runs on diagram

Complete the control data table below

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NFOI Manual Metal Arc Welding I

33 Student Workbook

Skill practice 2

Assessment event 1 (practical)

Pad weld plate horizontal

IF IN DOUBT ASK THE TEACHER

1 Outline with chalk, the required rectangular shape 60 x 200 mm.

2 Position the plate on the bench in the specified position.

3 Deposit weld beads along the plate length.

4 Remove all slag from individual weld beads before depositing subsequent runs Each run is to have a staggered stop and restart.

5. Build up the pad to the required dimensions and present the exercise for inspection.

6 Evaluate the weld project and complete the procedure sheet.

7. For assessment, repeat the pad weld to the requirements given below.

Things to note

a Setting of amperage and heat input

a Position of plate on the bench

• Correct method of arc striking

a Correct arc length

• Correct welding travel speed

• Correct electrode angles

Incorrect bead placement

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Section 4: Fillet weld joint terminology and faults

DURATION

1 hour This section introduces you to the technical terms that are used

to describe weld positions, areas and locations of a welded

joint, common defects and their causes

Objectives

At the end of this section you will be able to:

LI identify standard weld positions

• plug and slot

LI sketch and dimension mitre, convex and concave fillet welds

• leg length

• throat thickness

• weld toe i

LI identify typical weld defects associated with fillet welds

• under and over size welds

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

NFW Manual Metal Arc Welding I

Fillet welding

Fillet weld joints are the most commonly used method ofjoining welded structures.This type ofjoint does not require any preparation and is easily assembled

Industrial uses for fillet welds include:

structural steel workship building

earth moving equipment

Fillet welds can be welded in any position Welding positions and weld joint terms anddefinitions are included for your information

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Student Workbook May 1998

Fillet weld joint terminology and faults NFO1 Manual Metal Arc Welding I

37 Student Workbook

Types and positions of welds

VERTICAL Edge weld

HORIZONTAL

Intermittent fillet welds

Corner weld Slot weld Plug weld

Pad weld

OVERHEAD

Lap weld Fillet weld

Single V butt weld

uiiipone11Ls oi a HUeL weui NFOI Manual Metal Arc Welding 1

38 -

1 Parent metal

2 3 4 5 6

Heat affected zone

Root

Penetration

Leg length

Nominal throat thickness

Throat thickness (convex fillet)

Throat thickness (concave fillet)

Fillet weld dimensionsThe size of a fillet weld is determined by the following dimensions These can bemeasured with a fillet gauge.

Common weld defects

Weld defects are either externalorinternal.

External

Can be detected by visually inspecting the finished weld

• Undercut or overroll (overlap)

o Incomplete fusion andlor incomplete penetration

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