&Certification™: WeldingTraining Textbook …...Textbook Introduction Welding Training &...

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Welding Training & Certification™: Aluminum GMA (MIG) Welding (WCA03) Textbook Version: 2.4 © 2000 - 2015 Inter-Industry Conference On Auto Collision Repair WCA03-STMAN1-E

Transcript of &Certification™: WeldingTraining Textbook …...Textbook Introduction Welding Training &...

Page 1: &Certification™: WeldingTraining Textbook …...Textbook Introduction Welding Training & Certification : Aluminum GMA (MIG) Welding (WCA03) 8 Technicians are considered the experts

Welding�Training&�Certification™:Aluminum�GMA(MIG)�Welding

(WCA03)

Textbo

ok

Version:�2.4

©�2000�-�2015�Inter-Industry�Conference�On�Auto�Collision�Repair

WCA03-STMAN1-E

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Welding�Training�&�Certification™:�Aluminum�GMA�(MIG)�Welding�(WCA03)Textbook

Table�of�Contents 3

Contents

Introduction..............................................................................................................................7Obligations�To�The�Customer�And�Liability.......................................................................... 7

Module�1�-�Terminology,�Equipment,�And�Consumables........................................................13The�Welding�Event............................................................................................................. 13Aluminum�Vs.�Steel............................................................................................................ 15Transfer�Methods................................................................................................................ 19Electrode�Wire.................................................................................................................... 21Electrode�Wire�Feed�Systems.............................................................................................. 24Shielding�Gas......................................................................................................................27Aluminum�Welding�Machines............................................................................................ 28Module�Wrap-Up............................................................................................................... 29

Module�2�-�Welding�Preparation,�Tuning,�And�Techniques.................................................... 33Surface�Preparation.............................................................................................................33Technique�Variables............................................................................................................35Tuning�The�Welding�Machine.............................................................................................38Welding�Techniques........................................................................................................... 41Welding�Defects................................................................................................................. 44Practical�Application...........................................................................................................46Module�Wrap-Up............................................................................................................... 48

Module�3�-�Welding�Training�&�Certification™:�Aluminum�GMA�(MIG)�Welding...................51Test�Parameters................................................................................................................... 51Butt�Joint�With�Backing�Weld�2.5�mm............................................................................... 52Fillet�Weld.......................................................................................................................... 54Butt�Joint�With�Backing�Weld�1�mm.................................................................................. 55Plug�Weld...........................................................................................................................58Safety.................................................................................................................................. 59Module�Wrap-Up............................................................................................................... 60

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Introduction

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IntroductionTextbook

Welding�Training�&�Certification™:�Aluminum�GMA�(MIG)�Welding�(WCA03) 7

Obligations�To�The�Customer�And�Liability

The�collision�repair�industry�has�anobligation�to�correctly�repair�thecustomer’s�vehicle.�Collision�repairs�mustbe�performed�using:

• recommended�or�testedprocedures�from�vehicle�makers,I-CAR,�and�other�research�andtesting�organizations.

• quality�replacement�parts�andmaterials.

• repair�processes�and�parts�aswritten�and�agreed�upon�in�therepair�order.�If�items�on�the�repairagreement�are�not�consistentwith�the�repair�order,�it�can�beconsidered�fraud.

Performing�proper�collision�repairsrequires�using�parts�and�procedures�thatkeep�remaining�warranties�intact.

Collision�repairs�must�restore:

• safety.• structural�integrity.• durability.• performance.

• fit.• finish.

Throughout�the�damage�analysis�andrepair�process�the�repairer�and�insurermust:

• communicate�with�each�other.• maintain�constant�communication

with�the�customer.• be�in�agreement�with�each�other

and�the�customer�on�how�repairswill�be�performed.

• inform�the�customer�of�anychanges�in�the�repair�plan�fromthe�original�repair�agreement,�andexplain�the�changes�and�why�theyhave�to�be�made.

To�reduce�liability:

• make�sure�that�all�repairs�areperformed�thoroughly,�correctlyand�as�listed�in�the�damage�report.

• follow�proper�procedures.• have�documentation�of�required

repairs�with�detailed�recordkeeping�available�for�customers.

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Technicians�are�considered�theexperts�and�are�expected�to�beknowledgeable�on�how�to�performa�quality�repair.

Liability�insurance�that�covers�the�repairfacility�may�not�always�cover�all�damages.For�example:

• the�policy�may�not�coverfaulty�repairs,�leaving�liabilityresponsibility�completely�on�thefacility.

• a�shop�owner�may�find�that�repairfacility�liability�coverage�may�notcover�the�full�amount�awarded�ina�lawsuit.�The�shop�owner�wouldhave�to�pay�the�difference.

It�is�difficult�to�reduce�the�risk�of�liabilityexposure.�The�part�that�the�repairer�cancontrol�is�the�chance�of�being�found�atfault.�Chances�can�be�minimized�by:

• using�recommended�or�testedprocedures�from�the�vehiclemakers,�I-CAR,�or�other�researchand�testing�organizations.

• using�quality�replacement�partsand�materials�that�restore�fit,

finish,�durability,�and�perform�atleast�as�well�as�the�original.

• keeping�thorough�records.

Keeping�thorough�records�includes�morethan�recording�the�date,�mileage,�and�pre-existing�damage.�Record�keeping�alsoincludes:

• making�sure�all�notes�are�legible.• verifying�the�repairs�that�were

made�or�not�made.• having�the�customer�sign�a

waiver�for�repairs�that�they�donot�want�performed.�Repairersmust�determine�their�liability�onnot�repairing�safety�systems�suchas�restraint�and�anti-lock�brakesystems.

• keeping�computer�printouts�orworksheets�on�file�showing�wheelalignment�readings�or�vehicledimensions�before�and�afterrepairs.

• keeping�scan�tool�printouts�andrecords�of�computer�codes�forairbag,�anti-lock�brake,�emission,and�powertrain�control�module(PCM)�systems.

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• attaching�the�OEM�or�other�testedprocedure�printout�to�the�vehiclerepair�order.

• keeping�receipts�for�all�subletwork�performed.

Refer�to�"Video:�Topics�Off�Limits"�in�thepresentation.�This�video�identifies�topicsthat�should�not�be�brought�up�in�class.

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Module�1�-Terminology,

Equipment,�AndConsumables

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The�Welding�Event

Learning�objectives�for�this�moduleinclude:

• explaining�what�to�expect�duringthe�course�of�the�welding�event.

• identifying�the�differencesbetween�GMA�(MIG)�weldingaluminum�and�steel.

• identifying�the�different�transfermethods�used�for�GMA�(MIG)welding�aluminum.

• identifying�aluminum�GMA�(MIG)welding�equipment.

As�aluminum�becomes�more�prevalent�in�vehicles,such�as�with�this�2015�Ford�F-150,�it�is�important�toknow�how�to�safely�and�properly�weld�aluminum.

Welding�aluminum�is�not�necessarilyharder�than�welding�steel,�it�is�justsimply�different.�This�event�is�designed�tohelp�provide�a�foundational�skill�set�forwelding�aluminum.

Welding�during�collision�repairs�isnot�an�all-day�practice,�or�even�aneveryday�practice.�Having�the�properskills�to�make�sound�welds�is�criticalfor�maintaining�structural�integrity�and

future�crashworthiness�of�a�vehicle.�Thisevent�provides�an�opportunity�to�develop,improve,�and�verify�aluminum�weldingskills.

Students�can�expect�a�hands-on�coachingenvironment.

It�will�be�important�to�establish�what�thestudents�should�expect�for�the�day.�Themain�areas�that�will�be�covered�are:

• a�discussion�on�the�theoryinvolved�in�aluminum�welding.

• an�explanation�of�the�welds�andthe�test�criteria.

• an�overview�of�the�equipment.• the�hands-on�coaching

environment.�This�is�where�thepracticing�and�testing�of�the�sevenwelds�will�occur.

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What�are�your�goals?

Timely�completion�of�the�event�isexpected.�This�means�that�there�should�bea�reasonable�progression�of�improvementof�skills�throughout�the�event.

Ask�the�students,�what�are�your�personalgoals�for�today?

Examples:

• To�come�away�with�a�betterunderstanding�of�aluminum.

• Be�able�to�understand�variousaluminum�welding�techniques.

• Be�able�to�successfully�completeall�the�welds.

• To�refresh�aluminum�weldingskills.

• To�share�what�was�learned�withother�staff�members.

The�coaching�environment�should�be�viewed�as�asafe�place�for�continual�learning.

The�coaching�environment�should�beconsidered�a�safe�place for�continuallearning.�During�this�event,�the�instructorwill�be�observing�technique�and�providingguidance.�This�will�also�include�visuallyinspecting�and�destructively�testing�thewelds.

The�test�is�not�a�race,�not�a�competitiveevent,�and�it�is�not�a�game.�Instructors arehere�to�verify�the�participant's�skills�as�awelder�in�a�collision�repair�facility.

Explain�that�coaching�will�ideally�helpstudents�to:

• achieve�successful,�repeatableresults.

• recognize�weld�quality.• identify�and�correct�weld�defects

and�failures.• improve�welding�techniques.• attain�the�goal�of�being�better�and

safer�welders.

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Aluminum�Vs.�Steel

Vehicle�makers�recommend�GMA�(MIG)�welding.

Aluminum�can�be�welded�using�a�varietyof�processes.�There�are�several�advantagesof�the�Gas�Metal�Arc�(GMA),�or�MIG,welding�process�for�welding�aluminum.These�include�GMA�(MIG)�welding:

• is�widely�accepted.• is�the�process�being�recommended

by�vehicle�makers.• equipment�is�commonly�found�in

collision�repair�facilities.• can�be�used�on�a�wide�variety�of

aluminum�alloys�and�thicknesses.• has�a�good�production�rate.

Although�they�may�look�similar,�steel�and�aluminumhave�very�different�characteristics.

There�are�differences�between�GMA�(MIG)welding�aluminum�when�compared�tosteel.�Aluminum�has:

• a�lower�melting�temperature.Aluminum�melts�at�1,200°F.�Steelmelts�at�2,700°F.

• a�faster�heat�transfer.�Heat�travelsvery�rapidly�through�aluminum.It�will�spread,�rather�than�stayconcentrated�in�a�small�area.�Panelthickness�also�affects�the�heattransfer.

• a�greater�thermal�expansion�rate.When�aluminum�is�heated,�ittypically�expands�at�a�greater�ratethan�steel.

• no�color�change�when�heated.It�will�appear�to�change�statejust�before�it�melts.�There�is�noother�indication�that�the�surfacetemperature�is�rising.

Aluminum�oxide�has�a�higher�melting�temperature.

Aluminum�forms�a�protective�coatingcalled�aluminum�oxide.�This�is�whatmakes�aluminum�highly�corrosionresistant.�Aluminum�oxide:

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• is�self�healing�and�begins�to�re-form�instantly�if�it�is�removed�fromthe�surface.

• has�a melting�temperature�of3,725°F,�which�is�higher thanaluminum.

• must�be�removed�from�thealuminum�before�being�welded.

• will�lead�to�contamination�of�theweld.�This�contamination�is�calledporosity.

Cold�start�is�very�common�with�aluminum.

A�common�characteristic�of�aluminumGMA�(MIG)�welding�is�a�cold�start.Typically,�a�cold�start:

• is�at�the�beginning�of�the�weld.• is�caused�by�the�rapid�heat�transfer

of�aluminum.• will�cause�a�lack�of�penetration�at

the�beginning�of�the�weld.

A�crater�is�a�low�spot�at�the�end�of�the�weld.

Another�common�characteristic�ofaluminum�GMA�(MIG)�welding�is�craters.Craters�are�typically:

• at�the�end�of�the�weld.• caused�by�the�high�amounts�of

heat�generated�by�the�time�analuminum�weld�is�completed.

• seen�as�a�sunken�or�undercut�areaat�the�end�of�the�weld.�A�craterwill�commonly�be�a�weak�spot�inthe�weld.

Aluminum�welds�can�be�more�sensitive�to�crackingthan�steel�welds.

Cracks�may�occur�when�weldingaluminum.�Typically,�cracking�occurs:

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• from�overheating�the�aluminum.This�is�due�to�the�expansion�andcontraction�that�occurs.

• more�frequently�on�thickeraluminum.

• more�frequently�on�aluminumcastings.�Aluminum�castings�arecommonly�designed�with�varyingthicknesses�and�reinforcementsthroughout,�which�makes�themvery�rigid.

Shown�is�a�Miller�350P�welder.

Shown�is�a�Fronius�TransPulsSynergic�2700�welder.

Shown�is�an�Elektron�MultiMig�522�welder.

Shown�is�a�Car-O-Liner�Migatronic�welder.

Shown�is�a�Pro�Spot�Smart�MIG�welder.

Aluminum�has�a�greater�sensitivity�towelder�settings�when�working�withdifferent:

• alloys.• material�thicknesses.• joint�types.

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Changes�in�these�factors�will�typicallyrequire�adjustments�to�the�weldersettings.

This�Miller�350P�has�been�programmed�for�pulsespray-arc�welding.

This�Fronius�TransPulseSynergic�2700�has�beenprogrammed�for�1.2�mm�diameter�electrode�wire.

This�Elektron�MultiMig�522�has�been�programmedfor�aluminum�wire�and�is�set�up�for�pulse�mode.

This�Car-O-Liner�Migatronic�has�been�programmedfor�welding�on�aluminum.

This�Pro�Spot�Smart�MIG�display�panel�shows�howthe�welder�has�been�set�up�to�begin�welding�onaluminum.

Aluminum�GMA�(MIG)�welding�typicallyrequires�equipment�with�differentcapabilities�than�steel.�Typically,�GMA(MIG)�welders�used�for�aluminum:

• generate�more�amperage�(current).This�is�to�compensate�for�the�rapidheat�transfer.

• may�have�specific�settings�forwelding�on�aluminum.

• may�have�a�different�electrodewire�feed�system.

• may�use�a�spool�gun.• use�100%�argon�shielding�gas.• have�dedicated�parts�for�aluminum

electrode�wire�feeding.�Dedicated

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parts�may�help�reduce�thepossibility�of�cross�contaminationand�galvanic�corrosion.

It�is�important�to�reference�vehicle�repair�informationbefore�welding.

Vehicle�makers�may�have�repairinformation�that�will�specify�the:

• type�of�transfer�method�preferred.• electrode�wire�alloy�and�diameter

that�should�be�used�for�vehiclerepairs.

• weld�locations,�both�whereoriginally�located�and�where�tomake�replacement�welds.

• type�of�weld�joints�to�use�forrepairs.

• size�the�replacement�weld�shouldbe�and�how�far�apart�replacementwelds�should�be�spaced.

I-CAR's�Repairability�Technical�Support(RTS)�Portal�represents�the�next�erain�information�sharing�with�the�inter-industry.�The�user-friendly�website�isdesigned�to�link�repair�professionalswith�OEM�information�and�expertise,helping�to�enable�complete,�safe,�and

quality�repairs�with�the�click�of�a�button�atwww.i-car.com/rts.

Transfer�Methods

Shown�are�three�types�of�transfer�methods.

There�are�four�electrode�transfermethods:

• short-circuit.• globular.• spray-arc.• pulse�spray-arc.

The�most�often�recommended�foraluminum�is�pulse�spray-arc.

Globular�transfer�is�usually�notrecommended�for�aluminum�welding.Globular�transfer:

• produces�more�spatter�than�short-circuit�transfer.

• is�more�likely�to�produce�welddefects�in�aluminum.

• does�not�promote�goodpenetration.

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Short-circuit�transfer�uses�lower�amperage�than�othertransfer�methods.

Short-circuit�transfer:

• is�primarily�used�on�steel.• deposits�the�electrode�wire�as�it

touches�and�short�circuits�againstthe�base�metal�many�times�persecond.

• uses�lower�amperage�and�voltagethan�other�transfer�methods.

• makes�a�steady�crackling�soundwhen�correctly�adjusted.

Spray-arc�transfer�uses�higher�amperage�than�short-circuit�transfer.

Spray-arc�transfer:

• uses�higher�voltage,�amperage,and�wire�speed�than�short-circuittransfer.

• sprays�a�tiny�stream�of�moltendrops�across�the�arc,�from�theelectrode�wire�to�the�base�metal.The�molten�drops�are�muchsmaller�than�the�diameter�of�theelectrode�wire.

• makes�a�steady�humming�soundwhen�correctly�adjusted.

• produces�a�large,�more�fluid�weldpuddle�due�to�the�higher�heat�forthe�same�electrode�size.

• produces�little�or�no�spatter.• typically�requires�gun�travel�speed

to�be�increased�after�starting�theweld.�This�is�due�to�the�higherheat�generated�using�spray-arctransfer�compared�to�other�transfermethods.

• is�not�used�on�thin�aluminum.

Spray-arc�transfer�can�be�used�in�allpositions,�with�the�proper�size�electrodewire,�when�welding�aluminum.�It�isprimarily�used�on�heavier�metal,�typically4�mm�or�thicker.

Pulse�spray-arc�transfer�uses�two�types�of�weldingcurrent.

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Pulse�spray-arc�transfer�uses�a�backgroundcurrent�and�pulse�current.�It�is�requiredfor�automotive�aluminum�welding.�Duringpulse�spray-arc�transfer:

• the�background�current�maintainsthe�arc.

• the�pulse�current�“peaks”�at�higheramperages.�This�“peak”�detaches�adroplet�from�the�electrode�wire.

• the�high�current�pulses�rapidly.High�current�pulses�occurbetween�60�-�200�times�persecond.

• electrode�wire�transfers�onlyduring�the�high�current�pulses.

Pulse�spray-arc�transfer�allows�for�cooler�weldingwith�good�penetration.

Pulse�spray-arc�transfer:

• allows�for�cooler�weldingcompared�to�spray-arc.�This�is�dueto�the�time�between�low�currentand�high�current�pulses�where�theelectrode�wire�does�not�transfer.This�allows�cooling�while�stillmaintaining�the�arc.

• may�offer�less�chance�ofburnthrough�on�thin�aluminum,while�still�giving�good�penetrationon�thicker�aluminum.

• produces�little�or�no�spatter.• may�allow�a�larger�electrode�wire

to�be�used.• can�be�used�in�all�positions.

Video:�The�Sound�Of�Spray�ArcRefer�to�Video:�Transfer�MethodsSounds�in�the�presentation.�This�videodemonstrates�the�audio�differencesbetween�short-circuit,�spray-arc,�and�pulsespray-arc.

Electrode�Wire

Which�electrode�wire�to�choose�depends�on�thevehicle�maker.

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5000�series�electrode�wires�will�beused�for�the�purpose�of�this�weld�event.For�repairs,�follow�the�vehicle�makers'instructions�for�specific�electrode�wirerequirements.

Electrode�wires�are�alloys,�which�meansthey�are�aluminum�mixed�with�otherelements.�Electrode�wire�is�classified�inone�of�four�different�series,�either�1000,2000,�4000,�or�5000,�with�each�numberidentifying�a�specific�type�of�filler�alloy.

Using�the�correct�electrode�wire�is�criticalto�the�strength�and�integrity�of�the�weld.Electrode�wire�alloys�commonly�used�forcollision�repair�include:

• 4000�series,�usually�4043�or�4047.• 5000�series,�usually�5356�or�5554.

Electrode�wire�diameters�include:

• 0.8�mm.• 0.9�mm.• 1�mm.• 1.2�mm.

Electrode�wire�diameter�considerationsinclude:

• vehicle�maker�instructions.• metal�thickness.• amount�of�welding�current.• transfer�method.�Pulse�spray-

arc�transfer�can�allow�thinaluminum�to�be�welded�withthicker�electrode�wire.

• using�a�small�diameter�electrodewire�may�lead�to�problems�withsome�wire�feed�systems.

This�welding�machine�has�been�loaded�with�ER4047.

4000�series�electrode�wire:

• may�be�identified�as�AlSi,aluminum�silicon,�on�somewelding�machines.

• is�softer�wire�which�producesa�more�fluid�weld�puddle,�andprovides�a�better�weld�appearancethan�5000�series�electrode�wire.

• is�typically�used�for�cosmeticpanel�repairs.

• has�a�lower�tensile�strengthcompared�to�5000�series�electrodewire.

4043�alloy�electrode�wire�is�notcompatible�with�some�alloys�used�onvehicles.�The�Aluminum�Associationrecommends�using�4043�electrode�wirewhen�welding�6000�series�alloy�to�6000series.

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Mercedes-Benz�recommends�using�4043,1.2�mm�electrode�wire�for�welding�on2006 -�2015�SLS�models.

Audi�recommends�using�a�4047,�1.2�mmdiameter�electrode�wire�for�welding�onthe�2007�-�2015�vehicles.

General�Motors�recommends�4043,�0.9mm�diameter�electrode�wire�for�weldingon�the�hinge�pillar�casting�on�the�2014and�2015�Chevrolet�Corvette�Stingray.

Use�the�electrode�wire�required�by�the�vehiclemaker.

5000�series�electrode�wire:

• may�be�identified�as�AlMg,aluminum�magnesium�onsome�welding�machines.�Themagnesium�will�become�blacksoot�as�it�is�exits�out�of�theshielding�gas�and�burns.

• provides�a�higher�strength�weldthan�4000�series�electrode�wire.

• is�common�in�structural�repairs.• may�have�some�cosmetic�repair

usage.

Ford�recommends�using�5554,�1.2�mmdiameter�electrode�wire�for�welding�onthe�2015�F-150.

Jaguar�Land�Rover�recommends�using5554�electrode�wire�for�sectioning�5000series�structural�parts�on�their�aluminumvehicles.

General�Motors�recommends�5554,�0.9mm�diameter�electrode�wire�for�weldingstructural�repairs�on�the�2014�and�2015Chevrolet�Corvette�Stingray.

Refer�to�Video:�Electrode�Wire�ProgramSetup�in�the�presentation.�This�videodemonstrates�the�importance�of�makingsure�the�welder�is�programmed�for�thecorrect�electrode�wire�that�is�loaded�intothe�welder.

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Electrode�wire�should�be�stored�properly�when�notin�use.

The�best�welding�results�are�obtained�byusing�clean�electrode�wire.�When�not�inuse,�electrode�wire�should�be�stored�toslow�oxidation�in�a:

• warm,�dry�area.�Condensationmay�form�on�cold�wire�when�itmeets�warmer�air.

• sealed�plastic�bag.

Like�all�aluminum,�avoid�contaminatingthe�electrode�wire.�Using�clean�electrodewire�will�help�reduce�weld�porosity.

Aluminum�electrode�wire�has�nospecifications�for�the�amount�of�cast�andhelix.�Cast�is�the�curvature�of�a�length�ofwelding�wire�caused�by�winding�on�thespool.�Helix�is�how�much�a�cut�length�ofwelding�wire�springs�up�when placed�on�aflat�surface.

Electrode�Wire�Feed�Systems

The�wire�spool�attaches�directly�to�the�gun.

A�spool�gun:

• has�a�spool�of�wire�attacheddirectly�to�the�welding�gun.

• uses�one�motor�and�drive�roll�setattached�directly�to�the�gun�body.

• has�a�short�liner,�contained�insidethe�gun.

• may�have�limited�access�towelding�areas�due�to�its�size.

• may�have�a�flexible�end�to�helpincrease�accessibility.

Push-pull�feeders�are�able�to�use�longer�cables.

A�push-pull�feeder:

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• has�two�motors�and�two�sets�ofdrive�rolls.�One�set�of�each�is�inthe�power�source�cabinet�and�inthe�welding�gun.

• allows�for�a�longer�cable�length.• works�well�with�soft�electrode

wire.�A�push-pull�feeder�alsoprovides�uniform�feeding�for�smalldiameter�electrode�wire.

Push�feeders�may�use�two�sets�of�drive�rolls.

A�push�feeder,�similar�to�what�is�usedfor�most�steel�GMA�(MIG)�weldingapplications:

• has�the�feed�motor�and�drive�rollslocated�in�or�on�the�power�sourcecabinet.

• pushes�the�electrode�wire�througha�flexible�gun�liner�and�into�thewelding�gun.

• uses�a�liner�that�is�usually�limitedto�less�than�3�m.�Aluminum�wiretends�to�buckle�and�bind�at�thedrive�rolls�when�using�long�liners.This�can�cause�birdnesting.

Setting�drive�roll�tension�correctly�iscritical.�Some�welding�machines�usetwo�sets�of�drive�rolls�inside�the�powersource�cabinet�to�help�cut�down�onbirdnesting.

Shown�is�the�U-shaped�drive�roll�that�is�used�in�pushfeeders.

Shown�is�a�V-shaped�drive�roll�which�typicallycompresses�aluminum�electrode�wire.

Wire�feed�drive�roll�designs�vary�with�thetype�of�wire�feed�system�being�used.

Knurled�drive�rolls�are�typically�usedin�spool�guns�and�pull�feeders.�Knurleddrive�rolls�are�not�recommended�forpush�feeders.�The�knurling�may�causealuminum�to�flake�off�the�wire,�causingresistance�in�a�long�liner.

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U-shaped�drive�rolls�are�typically�used�inpush�feeders.

V-shaped�drive�rolls�are�not�recommendedfor�push�feeders.�V-shaped�drive�rollstypically�compress�aluminum�electrodewire.�Compressing�the�electrode�wire maycause�birdnesting.

Gun�liners�must�be�dedicated�for�aluminum.

The�welding�gun�liner�for�aluminumelectrode�wire:

• may�be�nylon�or�Teflon,�whichhelps�the�wire�slide�with�lessresistance.

• must�be�dedicated�for�aluminum.• should�be�blown�out�with�clean,

dry�compressed�air�to�removealuminum�particles.�Electrode�wiretends�to�leave�small�particles�thatcan�build�up�and�affect�electrodewire�feed�and�possibly�weldquality.�Follow�the�equipmentmaker's�maintenance�instructions.

Contact�tips�may�be�marked�with�AL�or�ALU�(left)and�should�be�slightly�recessed�in�the�nozzle�outlet(right).

The�contact�tip:

• is�usually�made�of�copper�orcopper�alloy.

• should�be�recessed�about�3�-�5mm�in�the�nozzle�outlet.�Somewelding�guns�may�be�recessedmore�than�that.

• may�become�worn,�reducingcurrent�transfer�efficiency�andcausing�the�electrode�wire�towander.�Change�the�contact�tipwhen�the�hole�diameter�becomesworn.

• may�be�oversized.�This�is�done�toprevent�the�wire�from�seizing�inthe�tip�due�to�expansion�from�heatduring�the�welding�process.

• may�be�marked�with�an�AL�or�ALUto�indicate�that�it�is�a�contact�tipspecific�for�aluminum�GMA�(MIG)welding.

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Shielding�Gas

100%�argon�gas�is�recommended�when�weldingaluminum.

100%�argon�is�used�for�aluminum�GMA(MIG)�welding.�A�mixture�of�argon�andhelium�should�not�be�used�becauseit�typically�welds�hotter.�This�makespenetration�harder�to�control�on�thinaluminum.�Pure�argon�provides:

• good�cleaning�action.• a�stable�arc.• better�control�of�penetration�on

thinner�aluminum.

Shielding�gas�nozzles�are�typically�tapered.

The�nozzle�directs�the�shielding�gas�to�theweld�zone.�Tapered�shielding�gas�nozzlesare�commonly�used�for�welding�in�the

collision�repair�industry.�The�taperedends�allow�for�better�visibility�of�the�weldjoint.

Inspect�and�ensure�that�the�shielding�gasnozzle�is�clean.�This�will�help�keep�theshielding�gas�flow�unrestricted.

Straight�shielding�gas�nozzles�aregenerally�used�for�welding�on�thickaluminum�at�a�higher�amperage.�Straightnozzles�are�used�to�envelop�larger�beadand�joint�areas�and�deliver�more�gasflow.

Shielding�gas�flow�rates�are�generally�higher�whenwelding�aluminum.

Flow�meters�are�generally�set�to�25�-�50cfh�for�aluminum�collision�repair�welding.This�compares�to�25�-�30�cfh�for�steel.This�range�depends�on�the�type�of�transfermethod,�thickness�of�the�aluminum,�andnozzle�size�used.�Before�attaching�theregulator,�open�the�cylinder�valve�for�asecond�or�two�to�blow�out�any�dirt�orcontaminants�that�may�be�near�the�valveopening.

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Aluminum�Welding�Machines

Reverse�polarity�is�also�referred�to�as�DCEP.

Reverse�DC�polarity,�when�the�electrodeis�positive�and�the�workpiece�is�negative(DCEP),�is�used�almost�exclusively�foraluminum�GMA�(MIG)�welding.

With�reverse�polarity,�80%�of�the�arc�heatis�at�the�electrode.�Reverse�polarity�isused�for�aluminum�welding�because�itprovides:

• the�highest�concentration�of�heat,which�is�needed�for�aluminum.

• narrow�heat�focus�zones.

Aluminum-specific�machines�typically�have�pre-programmed�aluminum�settings.

For�improved�weld�quality�and�easeof�use�when�welding�aluminum,�someequipment�makers�have�GMA�(MIG)welding�machines�that�are�specificallydesigned for�aluminum�welding.Aluminum-specific�welding�machines:

• have�higher�amperage�capabilitiesto�allow�spray�transfer.�An�outputof�200�amps�at�30%�duty�cycle�isrecommended.

• typically�come�equipped�with�aspool�gun,�a�push-pull�feeder,�ora�dual-drive�roll�electrode�wirefeed�system.�This�allows�for use�ofa�wider�variety�of�electrode�wirediameters�and�alloys.

• may�have�pre-programmedsettings�for�welding�aluminum.Settings�for�different�alloys�anddiameters�of�electrode�wire�maybe�available.�Some�machinesmay�have�settings�for�differentthicknesses�of�aluminum�and�jointconfigurations.�Features�to�reducecold�start�and�crater�defects�arealso�programmed�in�some�weldingmachines.

• typically�use�pulse�spray-arctransfer.

The�Fronius�2700�welder�shown�on�thescreen�uses�a�liquid-cooled�torch.�Thewelder�can�run�at�100%�duty�cycle,�witha�maximum�output�of�400�amps.�TheFronius�2700�has�programs�for�specificjoints�on�specific�vehicles,�such�as�a�3mm�butt�joint�with�backing�on�a�2004�-2010�Jaguar�XJ.

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Module�Wrap-Up

Topics�discussed�in�this�moduleincluded:

• what�to�expect�during�the�courseof�the�welding�event.

• the�differences�between�aluminumGMA�(MIG)�welding�compared�tosteel.

• the�different�transfer�methodsused�for�aluminum�GMA�(MIG)welding.

• aluminum�GMA�(MIG)�weldingequipment.

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Module�2�-�WeldingPreparation,�Tuning,

And�Techniques

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Surface�Preparation

Learning�objectives�for�this�moduleinclude:

• identifying�how�to�properlyprepare�aluminum�alloys�for�GMA(MIG)�welding.

• describing�the�different�techniquevariables�when�aluminum�GMA(MIG)�welding.

• determining�how�to�tune�a�GMA(MIG)�welder�to�weld�aluminum.

• describing�techniques�specific�toaluminum�GMA�(MIG)�welding.

• identifying�weld�defects,�causes,and�correction�methods.

• describing�practices�used�incollision�repair�facilities�foraluminum�GMA�(MIG)�welding.

Aluminum�oxide�protects�aluminum�from�corroding.

Aluminum�oxide:

• forms�on�the�surface�of�barealuminum,�protecting�thealuminum�from�further�corrosion.Oxide�can�be�compared�to�thezinc�coating�on�steel,�in�that�the

oxide�protects�the�aluminum�fromdeterioration.

• will�begin�to�re-form�immediatelyon�the�surface,�if�removed.

• can�trap�moisture�and�dirt.�A�thicklayer�of�oxide�tends�to�hold�moredirt�and�moisture�than�a�thin�layer.

• can�cause�porosity�in�analuminum�weld�bead.

Every�area�of�the�weld�joint�must�have�coatings�andoxide�removed.

Poor�welds�occur�from�aluminumsurfaces�that�are�contaminated.�This�mayinclude�coatings�and�aluminum�oxide,which must�be�removed�about�30�-�40mm�from�the�weld�joint.�Every�area�of�theweld�joint�should�be�thoroughly�cleaned,including�the�backside�and�the�edges.

Leaving�coatings,�aluminum oxide,�or�anycontaminants too�close�to�the�weld�zonemay�cause�defects�in�the�weld.

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Shown�are�the�various�items�used�to�remove�coatingsand�aluminum�oxide.

The�coatings�and�aluminum�oxide�areremoved�using�a:

• wax�and�grease�remover�first�toremove�any�residue.�Sandingbefore�using�wax�and�greaseremover�smears�the�contaminantsinto�the�surface�of�the�aluminum.

• plastic�woven�pad�or�disc�sanderwith�80�-�120�grit�sandpaper.Sandpaper�can�also�be�used�byhand�to�access�small�hard-to-reachareas.

• stainless�steel�wire�brush.

Use�abrasives�dedicated�for�use�onaluminum.�Abrasives�used�for�steel�maycontaminate�an�aluminum�surface.

It�is�important�not�to�use�weld-through�primer�onaluminum.

If�a�disc�sander�is�used,�do�not�press�toohard.�Excessive�sanding�pressure�may:

• remove�too�much�aluminum,thinning�the�metal.�Thinning�themetal�may�also�lead�to�warpingfrom�overheating.

• clog�the�disc.�Using�a�cloggeddisc�on�aluminum�may�scratch�orgouge�the�surface.

• imbed�impurities�into�the�surface.

Do�not�use�mild�steel�brushes�for�oxideremoval.�Mild�steel�brush�particles�mayflake�off,�contaminating�the�aluminum.

Weld-through�primers should�not�be�usedon�aluminum.

After�cleaning,�avoid�handling�the�surfacesto�be�joined�with�bare�hands.�This�maycontaminate�the�clean�surface�andadversely�affect�weld�quality.

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Weld�as�soon�as�possible�following�part�fit-up�andcleaning.

After�cleaning�the�aluminum,�thealuminum�oxide�forms�relatively�quicklyon�the�surface.�This�is�the�self-healingfeature�of�aluminum�alloys.�Weldingshould�be�done�as�soon�as�possiblefollowing�part�fit-up�and�cleaning.�Theweld�joint�should�be�cleaned�again�witha�small�stainless�steel�brush�immediatelybefore�welding.�The�amount�of�time�thatcan�pass�before�complete�re-cleaning�isrequired�will�vary�with�temperature�andhumidity�levels.

Technique�Variables

The�welding�gun�is�pointed�and�pushed�away�fromthe�weld�puddle.

Welding�aluminum�requires�the�pushtechnique.�The�push�technique:

• is�when�the�welding�gun�ispointed�and�pushed�away�from�theweld�puddle.�The�push�techniqueis�also�called�forehand�or�leadangle�by�the�American�WeldingSociety�(AWS).

• helps�direct�the�shielding�gas�tothe�front�of�the�weld�puddle.

• provides�an�arc�cleaning�action�toremove�aluminum�oxide�from�thesurface.

• is�done�straight.�The�welding�gunis�not�weaved�back�and�forth�onthe�joint.�Weaving�will�changewhere�the�arc�is�being�focused.

The�pull�technique,�also�called�the�drag�orbackhand�with�drag,�is�when�the�weldinggun�is�pointed�at�and�dragged�away�fromthe�weld�puddle.�This�type�of�technique�isnot�used�for�aluminum�because�it:

• increases�the�chance�of�porosityand�a�poor�weld�by�not�providingenough�shielding�gas�and�cleaningaction.

• may�cause�the�joint�to�be�rough,or�have�large�amounts�of�blacksoot�on�the�weld�bead.

• may�overheat�the�weld�area,causing�excessive�penetration.

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The�gun�angle�for�pushing�does�not�need�to�beexcessive.

Welding�gun�angle�for�the�pushtechnique:

• should�be�about�5�-�15°�fromvertical.

• does�not�need�to�be�excessive,such�as�45°�from�vertical.�Anglingthe�welding�gun�too�far�backmay�cause�a�loss�of�shielding�gaseffect�at�the�front�of�the�weld.Too�much�gun�angle�may�alsodraw�contaminants�in�from�thebackside�of�the�welding�gun,�dueto�a�vacuum�effect.

Work�angle�affects�where�heat�is�directed.

The�work�angle:

• affects�where�the�heat�is�directedto�the�joint.

• varies�by�different�welding�jointdesigns.

• for�butt�joints�or�butt�joints�withbacking�is�90°,�directed�at�thecenter�of�the�root.

• for�fillet�welds,�also�known�as�lapjoints,�using�the�same�thickness�ofaluminum,�is�45°,�directly�at�theroot.�When�a�fillet�weld�has�twodifferent�thicknesses�of�aluminum,the�work�angle�should�be�directingmore�heat�on�the�thicker�panel.This�may�help�reduce�burningaway�of�the�thinner�aluminum.

If�a�butt�joint�with�backing�is�being�madein�two�passes,�it�should�be�treated�as�twofillet�welds.�Students�may�do�the�butt�weldwith�backing�either�way�for�the�I-CARWelding�Training�&�Certification™.

Contact�tip-to-workpiece�distance�should�be�about10�-�16�mm.

The�contact�tip-to-workpiece�distance:

• should�be�about�10�-�16�mm.• may�help�control�bead�height.

Varying�the�contact�tip-to-

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workpiece�distance�may�also�affectpenetration�along�a�continuousweld.

• is�an�important�factor�for�pulsespray-arc�welding,�as�this�affectsthe�arc�length.

• will�affect�stick-out.�Contact-tip-to-workpiece,�wire�speed,�andvoltage�will�affect�stick-out.

Shown�is�the�result�of�a�travel�speed�that�is�either�tooslow�(top)�or�too�fast�(bottom).

Travel�speed:

• affects�penetration�and�overallweld�bead�dimensions.

• varies�by�the�transfer�methodbeing�used.�The�travel�speedtypically�needs�to�be�increased�asthe�weld�progresses�when�usingthe�spray-arc�transfer�method.This�is�from�the�constant�highamperage�being�used.�For�pulsespray-arc,�the�travel�speed�canremain�more�constant.�This�is�fromthe�cooler�welding�action�of�thepulsed�current.

Travel�speed�may�need�to�be�increasedno�matter�which�transfer�method�is�usedwhen�working�on�thinner�aluminum.

Body�positioning�can�affect�how�well�you�see�theweld.

Body�positioning�is�one�of�the�mostoverlooked�factors�with�all�types�ofwelding.�When�aluminum�GMA�(MIG)welding,�it�is�very�important�that�atechnician�can�fully�see�the�area�to�bewelded.�Reading�glasses�or�a�magnifyinglens�for�the�welding�helmet�may�improvea�technician’s�ability�to�see�the�joint�whilewelding.

Being�able�to�see�more�clearly�may�helpwith:

• better�gun�control.• arc�direction�to�focus�the�heat

where�it�is�wanted.

Magnifying�lenses�for�welding�helmets�arecommonly�referred�to�as�“cheater�lenses.”Cheater�lenses�are�typically�available�atwelding�supply�stores�and�are�available�indifferent�strengths�of�magnification.

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Tuning�The�Welding�Machine

The�Miller�350P�has�a�chart�on�the�welder�to�providean�initial�program�setting.

The�Fronius�TransPulseSynergic�2700�amperage�isbeing�adjusted.

Amperage�adjustments�are�being�made�on�theElektron�MultiMig�522.

The�Car-O-Liner�Migatronic�amperage�setting�isbeing�adjusted�for�the�material�thickness.

Once�the�material�thickness�has�been�adjusted,�thenew�amperage�/�voltage�setting�will�not�show�upon�the�welder�until�the�arc�is�struck�on�the�Pro�SpotSmart�MIG.

Amperage�and�voltage�settings�used�forGMA�(MIG)�welding�aluminum�varydepending�on:

• electrode�wire�diameter�and�alloy.Larger�diameters�and�higher�alloyseries�will�typically�require�higheramounts�of�amperage�and�voltage.

• material�thickness.�The�thickerthe�aluminum�is,�the�higher�theamperage�required.

• joint�type.�Different�joint�typestypically�require�different�amountsof�amperage�and�voltage.

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Some�welding�machines�have�charts�forthe�technicians�to�find�a�starting�point�thatcan�be�used�for�making�practice�welds.Determining�the�required�amperagesetting�is�important�to�determine�if�thewelding�machine�being�used�is�capableof�supplying�the�necessary�amperage�fora�given�thickness�of�metal.�For�thinnermetal,�it�will�help�to�know�that�maximumamperage�is�not�required�to�produce�aquality�weld.

Increasing�or�decreasing�amperage�affects�the�heatof�the�weld.

Adjusting�the�amperage,�or�current,�isthe�same�as�increasing�or�decreasing�thewire�speed.�An�increase�in�amperage�willmake�the�weld�hotter.�This�will�increasepenetration�and�make�a�larger�weldbead.

Decreasing�the�amperage�will�makethe�weld�cooler.�This�will�decreasepenetration�and�make�a�smaller�weldbead.

Adjusting�the�amperage�to�the�materialis�typically�the�first�step�in�tuning�thewelding�machine.

The�voltage�setting�is�automatically�adjusted�as�theamperage�is�set�on�synergic�welders.

Voltage�affects�the�rate�in�which�theelectrode�wire�burns.�Changes�made�tothe�voltage�when�aluminum�GMA�(MIG)welding�typically�affects�the�arc�length.The�arc�length�is�the�distance�that�theelectrode�wire�is�burning�from�the�surfaceof�the�workpiece.�Too�much�voltage�mayresult�in�burnback�to�the�contact�tip.

Synergic�welding�machines�adjust�voltageautomatically�when�the�amperage�ischanged.

Arc�length�affects�the�distance�the�electrode�wire�isburning�from�the�workpiece.

Arc�length�adjustment:

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• is�typically�an�independentadjustment�on�pulse�spray-arcwelding�machines.

• is�typically�a�fine-tuningadjustment.

• affects�weld�penetration�and�beaddimensions.

• negatively,�makes�the�electrodewire�burn�closer�to�the�surfaceof�the�workpiece.�A�decrease�inarc�length�will�result�in�increasedpenetration,�but�make�the�weldbead�narrower.

• positively,�makes�the�electrodewire�burn�farther�away�fromthe�surface�of�the�workpiece.Increased�arc�length�decreasespenetration,�but�makes�the�weldbead�wider.

Refer�to�Video:�Tuning�The�Welder�-�Miller350P�in�the�presentation.�This�videodemonstrates�that�initial�pre-programmedsettings�may�need�adjustments�and�thatthe�person�welding�needs�to�be�preparedto�make�those�determinations.

Refer�to�Video:�Tuning�The�Welder�-Elektron�MultiMig�522�in�the�presentation.This�video�demonstrates�how�to�makeadjustments�to�the�initial�setup�of�thewelder.

Refer�to�Video:�Tuning�The�Welder�-�ProSpot�Smart�MIG�in�the�presentation.This�video�demonstrates�how�to�makeadjustments�to�the�initial�setup�of�thewelder.

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Welding�Techniques

A�hot-start�function�on�some�welders�will�help�avoida�cold�start�(inset).

A�major�concern�when�welding�aluminumis�poor�penetration�at�the�beginning�ofthe�weld.�This�is�called�a�cold�start.�Coldstart�is�caused�by�the�rapid�heat�transfercharacteristic�of�aluminum.

If�the�welder�has�a�hot-start�function,�thiscan�be�avoided.�A�hot-start�function�willboost�the�amperage�at�the�beginning�ofthe�weld�to�heat�the�aluminum�quicker.Some�welders�that�have�a�hot-startfunction�use�a�time�setting�for�how�longthe�hot�start�stays�on.

With�most�welders,�it�is�necessary�tocompensate�for�the�cold�start.

Tailing�in�can�be�used�for�any�type�of�weld.

One�method�to�compensate�for�a�coldstart�is�to�start�the�weld�off�the�jointand�move�into�the�joint�after�the�arc�isestablished,�sometimes�called�“tailing�in.”This�can�be�used�for�any�weld.

Practice�will�help�in�making�consistent�weld�beads.

Good�weld�bead�consistency�is�key�formaking�strong�aluminum�GMA�(MIG)welds.�Key�items�for�achieving�good�weldbead�consistency�include:

• keeping�the�same�work�angle�onthe�joint�throughout�the�weld.

• keeping�the�same�gun�distancefrom�the�joint�throughout�theweld.

• travel�speed.�Spray-arc�transfertypically�requires�an�increasedtravel�speed�while�making�theweld.�A�more�even�travel�speedcan�be�used�when�while�makingthe�weld�using�pulse�spray-arctransfer.

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Crater�Fill�Welder�Setting

A�welder�with�a�crater�fill�setting�decreases�thecurrent�at�the�end�of�the�weld.

There�are�techniques�to�fill�craters,�whichare�common�at�the�end�of�an�aluminumweld.�Techniques�for�avoiding�cratersinclude:

• speeding�up�slightly�whenapproaching�the�end�of�the�weld,and�then�backtracking�onto�theweld�bead.

• stopping�the�weld�and�pausing�tolet�the�weld�bead�cool�briefly,�thenrestriking�the�arc�and�filling�thecrater.

Some�welding�machines�have�settingsfor�a�crater�fill.�Crater�fill�settings�allowthe�welder�to�drop�the�amperage�downgradually�when�approaching�the�end�ofthe�weld�bead.

Refer�to�“Video:�Filling�Craters”�in�thepresentation.�This�video�shows�how�to�filla�crater�at�the�end�of�a�aluminum�weldbead.

Run-on�and�run-off�tabs�can�be�used�for�start�andstop�areas.

Besides�helping�to�align�a�joint�andprovide�strength,�a�backing�strip�may�beused�on�an�aluminum�butt�joint�to�provide“run-on”�and�“run-off”�tabs.

Run-on�and�run-off�tabs:

• may�be�an�extension�of�thebacking.

• may�be�separate�tabs�welded�on�atthe�ends�of�the�joint.

• are�used�as�areas�for�the�weld�tobe�started�and�stopped.

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• keep�the�cold�start�area�of�theweld�from�being�made�on�thepanel.

• moves�the�crater�out�of�the�repairarea.

• are�removed�after�welding.

A�visual�inspection�should�be�completed�on�allwelds.

Initial�visual�inspection�after�making�analuminum�GMA�(MIG)�weld�includeslooking�to�see�whether:

• the�joint�is�completely�filled.• the�crater�is�filled�at�the�end�of�the

weld.• the�weld�bead�has�good�width�and

height�dimensions.• penetration�is�evident,�but�not

excessive�melt-through�or�heatmark�on�the�backside.

Weld�appearances�can�be�deceiving.

This�butt�joint�with�backing�appearsto�be�a�good�weld.�There�is�a�flat�andconsistent�bead�on�the�face�and�evidenceof�penetration�on�the�backside�alongthe�full�length�of�the�joint.�This�does�notensure�that�the�weld�will�pass�destructivetesting.

A�destructive�test�of�this�weld�shows�there�was�nofusion�to�the�top�coupons.

Destructive�testing�of�practice�welds�willhelp�to�verify�if�changes�will�need�to�bemade�to�technique�and�/�or�if�adjustmentswill�need�to�be�made�to�the�welder.Practicing�on�like�material�thickness�andjoint�configuration�will�help�ensure�agood�repair.

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Welding�Defects

Cold�welds�may�appear�to�be�sitting�on�the�surface.

A�cold�weld:

• appears�as�too�much�weld�metalbuild�on�the�surface.

• has�little�or�no�evidence�ofpenetration.

• has�little�or�no�fusion�to�theworkpiece.

• is�usually�caused�by�the�amperageset�too�low.

• can�occur�from�using�a�travelspeed�that�is�too�fast.

Too�much�heat�can�weaken�the�surroundingaluminum.

Too�much�heat�can:

• cause�excessive�penetration.• cause�burnthrough�on�the

workpiece.• weaken�material�by�permanently

softening�the�surrounding�area.• be�caused�by�an�amperage�setting

that�is�too�high.• be�caused�by�a�travel�speed�that�is

too�slow.

Suck-back�looks�like�a�crater�on�the�backside.

Suck-back�is�when�the�weld�bead�shrinksback�during�cooling�to�form�a�crater�onthe�backside�of�the�weld.�Suck-back:

• is�usually�found�on�overheadwelds.

• can�result�in�weakening�the�weldbead�or�base�metal.

Some�techniques�to�prevent�suck-backinclude:

• reducing�the�settings�on�thewelding�machine.

• slightly�increasing�travel�speed.• on�butt�joints,�reducing�the�root

gap�during�fit-up.

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Incompatible�filler�alloys�may�cause�cracks.

Though�not�common�with�aluminumwelds,�cracks�or�fracturing�of�analuminum�weld�can�occur�if�there�is:

• too�much�amperage�or�voltageused.

• the�wrong�alloy�electrode�wire.• rapid�cooling.• improper�joint�fit-up,�causing

internal�stress.• inadequate�penetration,�causing

weld�failure�from�fatigue.• inadequate�weld�bead.

 

Undercut�welds�look�lower�than�the�edge�or�edgesof�the�top�workpiece.

An�undercut�weld:

• will�look�as�if�the�weld�bead�islower�than�the�edge�or�edges�ofthe�top�workpiece.

• typically�has�lack�of�fusion�to�thetop�workpieces.

• is�commonly�caused�by�a�travelspeed�that�is�too�fast.

• on�a�butt�joint�with�backing�weldcan�be�caused�by�a�root�gap�that�istoo�wide.

Improper�work�angle�affects�heat�focus.

Using�an�improper�work�angle:

• will�direct�the�arc�incorrectly.• will�not�focus�the�heat�where�it�is

wanted.• may�cause�a�lack�of�fusion

between�the�workpieces.• may�cause�excessive�penetration

and�suck-back.�For�example,�afillet�weld�where�the�work�angle�isfocused�on�the�bottom�piece maygive�the�weld�bead�a�very�shallow,almost�undercut�appearance�andhave�excessive�penetration�intothe�bottom�piece.

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Inconsistent�travel�speed�and�technique�can�causeinconsistent�beads.

A�weld�bead�that�is�varying�in�size�may�becaused�by�inconsistent:

• travel�speed.�Speeding�up�andslowing�down�will�change�thewidth�of�the�weld�bead.

• gun�distance.�Moving�the�gun�inand�out�will�change�the�height�ofthe�weld�bead.

Weld�beads�that�wander�off�the�jointare�commonly�caused�by�poor�bodypositioning.�A�technician�must�be�inposition�to�see�the�area�that�will�bewelded.

Porosity�will�appear�as�holes�or�pores.

An�aluminum�weld�that�has�porositywill�appear�to�have�excessive�soot�onthe�exterior�of�the�weld�bead. A�porousweld:

• will�appear�to�have�several�holesor�pores.

• may�appear�to�have�less�fillermaterial�than�required.

• will�be�weak.

Porosity�can�be�caused�by:

• the�workpiece�not�being�cleanedenough�to�remove�coatings�andaluminum�oxide.

• a�low�shielding�gas�flow�rate.• not�pushing�the�gun.• using�contaminated�welding�wire.• using�contaminated�shielding�gas.

Practical�Application

Vehicles�should�be�protected�while�welding.

To�avoid�damaging�the�vehicle�fromwelding�sparks:

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• cover�the�vehicle�with�weldingblankets�or�spark�paper.

• adjacent�parts�may�be�removed.

An�induction�of�current�or�voltage�spikescan�destroy�sensitive�electronic�parts.When�welding,�protect�computers�andother�electronic�parts�by:

• disconnecting�and�isolating�bothbattery�cables.�Remove�and�isolatethe�negative�battery�cable�first.

• removing�computers�or�othersensitive�electronic�parts�ifwelding�closer�than�300�mm.

• keeping�the�current�path�short�byplacing�the�ground�clamp�close�tothe�weld�zone.

• keeping�the�welding�machineas�far�away�from�the�vehicle�aspossible.

• not�allowing�welding�cables�topass�near�computers�or�sensors.Welding�cables�should�runperpendicular�to�wiring�harnesses.

Practice�welds�should�be�done�before�welding�on�avehicle.

Practice�welding�is�a�very�important�stepin�the�repair�process.�Practice�weldingmust�be:

• done�before�welding�on�a�vehicle.• done�using�the�same�thickness

and�alloy�of�aluminum�that�isused�on�the�vehicle.�Similar�jointstyles�should�be�constructed�andpracticed�in�the�same�position�aswill�be�done�on�the�vehicle.

• destructively�tested�after�passingvisual�inspection.

Aluminum�welding�may�not�be�doneevery�day�in�a�collision�repair�facility.�Awelding�logbook�is�one�way�to�keep�trackof�welder�settings�that�were�successfulfor�a�particular�application.�A�weldinglogbook�may�help�find�a�starting�point�forsimilar�repairs�that�need�to�be�done�in�thefuture.

Dress�welds�where�they�will�interfere�with�adjacentpanel�fit-up�(left).�Epoxy�primer�is�commonly�used�tocoat�bare�aluminum�(right).

Dressing aluminum�welds�may�be�doneusing:

• 50�grit�sanding�discs.

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• aluminum-specific�grinding�discs.• light�pressure.�Light�pressure�helps

prevent�clogging�of�the�discs�andsmearing�the�aluminum�fromoverheating.

Check�vehicle�maker�instructions�for�welddressing.

Finishing�aluminum�welds�typicallyrequires:

• using�caution�to�not�thin�thesurrounding�weld�area,�as�this�maylead�to�cracking.

• using�a�fine�tooth�body�file�or�P80grit�sanding�disc�to�remove�anycoarse�scratches�left�by�grinding.

• coating�the�bare�aluminum�witheither�a�primer�or�cosmetic�fillerif�it�is�a�cosmetic�part.�Vehiclemakers�typically�specify�productsfor�coating�bare�aluminum.

Module�Wrap-Up

Topics�discussed�in�this�moduleincluded:

• how�to�properly�preparealuminum�alloys�for�GMA�(MIG)welding.

• the�different�technique�variableswhen�aluminum�GMA�(MIG)welding.

• how�to�tune�a�GMA�(MIG)�welderto�weld�aluminum.

• techniques�specific�to�aluminumGMA�(MIG)�welding.

• weld�defects,�causes,�andcorrection�methods.

• practices�used�in�collision�repairfacilities�for�aluminum�GMA(MIG)�welding.

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Module�3�-�WeldingTraining�&

Certification™:Aluminum�GMA(MIG)�Welding

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This�page�is�intentionally�left�blank.

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Test�Parameters

Learning�objectives�for�this�moduleinclude�describing:

• test�parameters�of�the�I-CAR�Welding�Training�&Certification™:�Aluminum�GMA(MIG)�Welding.

• visual�inspection�criteria�of�buttjoint�with�backing,�fillet,�and�plugwelds.

• destructive�testing�criteria�for�thewelds.

The�I-CAR�Welding�Training�&�Certification™:Aluminum�GMA�(MIG)�Welding�requires�a�totalof�four�different�welds�to�be�completed,�Three�ofthe�welds�are�completed�in�both�the�vertical�andoverhead�positions.

The�Welding�Training�&Certification™: Aluminum�GMA�(MIG)Welding�event:

• is�a�method�to�verify�skills�ofcollision�repair�technicians�whoare�welding�aluminum�on�a�dailybasis.

• is�done�on�5000�and�6000�seriesalloy�aluminum�coupons�in�two

thicknesses.�All�coupons�are�76�x127�mm.

• requires�four�different�welds.�Thethree�welds�to�be�completed�inboth�the�vertical�and�overheadpositions�are�butt�joint�withbacking�2.5�mm,�fillet,�and�buttjoint�with�backing�1�mm.�Thefourth�is�the�plug�weld,�which�isto�be�completed�in�the�verticalposition�only.

Recognition�will�be�provided�when�all�welds�aresuccessfully�made.

Participants�who�pass�the�WeldingTraining�&�Certification™:�AluminumGMA�(MIG)�Welding�(WCA03)�eventreceive:

• a�letter�congratulating�them�onsuccessfully�passing�the�WeldingTraining�&�Certification™:Aluminum�GMA�(MIG)�Welding.

• a�Certificate�of�Completion.• an�I-CAR�Welding�Training�&

Certification™:�Aluminum�GMA(MIG)�Welding�magnet.

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This�is�the�I-CAR�Aluminum�GMA�(MIG)�WeldingGauge.

The�I-CAR�Aluminum�GMA�(MIG)Welding�Gauge�is�used�to�visually�inspectall�of�the�test�welds.�The�gauge�measuresminimum�and�maximum:

• face�and�melt-through�height.• bead�width.• nugget�diameter.• bead�length.

Butt�Joint�With�Backing�Weld�2.5�mm

The�butt�joint�with�backing�weld�is�done�using�three2.5�mm�coupons.

The�butt�joint�with�backing�weld�for�thetest�is�made�on�three�2.5�mm,�5052-H32alloy�coupons.�When�fitting�up�the�buttjoint,�butt�two�coupons�edge�to�edge,�and

center�the�third�coupon�behind�the�joint.Keep�a�root�gap�between�the�two�topcoupons�about�2�-�3�metal�thicknesses.Root�gap�will�depend�on�if�the�weld�isbeing�done�in�one�or�two�passes.

The�participants�are�required�to�make�acontinuous�weld,�centered�on�the�joint,�inthe�vertical�and�overhead�positions.�If�thebutt�joint�with�backing�is�being�made�withtwo�passes,�it�should�be�treated�as�twofillet�welds.�Tack�welds�are�not�allowed.Coach�the�butt�joint�with�backing�weldwith�the�participant�until�successful,repeatable�results�are�achieved.

The�I-CAR�Aluminum�GMA�(MIG)�Welding�Gauge�isused�when�doing�the�visual�inspection.

Visual�requirements�for�the�face�side�ofthe�butt�joint�with�backing�2.5�mm�weldinclude:

• no�cracks,�porosity,�skips,�orundercut.

• the�joint�and�crater�are�completelyfilled.

• a�bead�length�of�57�-�76�mm.• a�bead�width�of�10�-�16�mm.• a�bead�height�no�greater�than�2

mm.

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The�backside�of�the�weld�is�being�inspected�forexcessive�melt-through.

Visual�requirements�for�the�backside�ofthe�butt�joint�with�backing�2.5�mm�weldinclude:

• no�cracks.• no�suck-back,�except�at�the�stop

point.• a�melt-through�width�no�greater

than�3�mm.• melt-through�height�no�more�than

2�mm.

The�butt�joint�with�backing�weld�is�avisual�failure�if�any�of�these�requirementsare�not�met.

Welds�that�pass�visual�inspection�must�bedestructively�tested.

Destructively�test�the�butt�joint�with�backing�weldafter�it�passes�visual�inspection.

Destructively�test�the�butt�joint�withbacking�2.5�mm�weld�using�thisprocedure:

1. Clamp�the�weld�sample�in�a�viseso�one�of�the�top�coupons�facesthe�front�of�the�vise,�and�the�weldbead�is�slightly�above�and�parallelto�the�vise�jaw.

2. Use�a�wide,�flat-jawed�lockingpliers�to�bend�the�upper�couponback�and�forth�until�it�breaks�freefrom�the�backing.

3. Reverse�the�weld�sample�in�thevise�and,�similarly,�break�theremaining�coupon�from�thebacking.

4. Inspect�each�face�coupon�formetal�tearout.�Also�inspect�theweld�bead.�The�weld�is�good�ifthere�is�metal�tearout�on�each�ofthe�face�coupons�for�the�lengthof�the�weld�and�the�weld�holdsfirm�on�the�backing�piece.�Thecoupons,�and�not�the�weld,�shouldbreak�to�pass�the�butt�joint�withbacking�weld.

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Fillet�Weld

The�fillet�weld�uses�two�coupons�that�are�differentthicknesses.

The�fillet�weld�for�the�test�is�made�on�twothicknesses�of�coupons,�a�1�mm,�6061�T6alloy�coupon�and�a�2.5�mm,�5052�H32alloy�coupon.�The�1�mm�coupon�is�lappedabout�halfway�over�the�2.5�mm�coupon'slength.

The�participants�are�required�to�makefillet�welds�centered�on�the�lap�joint�inthe�vertical�and�overhead�positions.�Tackwelds�are�not�allowed.�Coach�the�filletweld�with�the�participant�until�successful,repeatable�results�are�achieved.

The�weld�bead�length�is�being�checked.

Visual�requirements�for�the�face�side�ofthe�fillet�weld�include:

• no�cracks,�porosity,�skips,�orundercut.

• the�joint�and�crater�are�completelyfilled.

• a�bead�length�of�57�-�76�mm.• a�bead�width�of�5�-�10�mm.• a�bead�height�no�greater�than�2

mm.

The�backside�of�the�weld�is�being�inspected�forexcessive�melt-through.

Visual�requirements�for�the�backside�ofthe�fillet�weld�include:

• no�cracks.• no�suck-back,�except�at�the�stop

point.• a�melt-through�width�no�greater

than�3�mm.• melt-through�height�no�more�than

2�mm.

If�the�weld�area�does�not�meet�thevisual�criteria,�it�does�not�have�to�bedestructively�tested.�The�fillet�weld�is�avisual�failure�if�any�of�these�requirementsare�not�met.

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Welds�that�pass�visual�inspection�must�bedestructively�tested.

Destructively�test�the�fillet�weld�after�it�passes�visualinspection.

Destructively�test�the�fillet�weld�using�thisprocedure:

1. Clamp�the�bottom,�2.5�mmcoupon�in�a�vise�so�that�the�top,�1mm�coupon�is�above�and�parallelto�the�vise�jaws.

2. Bend�the�1�mm�coupon�untilit�breaks�off�from�the�2.5�mmcoupon.

3. To�pass�inspection,�there�mustbe�metal�tearout�from�the�1�mmcoupon�for�at�least�the�length�ofthe�weld�and�the�weld�holds�firmon�the�backing�piece.�The�coupon,and�not�the�weld,�should�breakto�pass�the�fillet�weld�on�lap�jointtest.

4. Inspect�the�weld�bead�on�thebottom,�2.5�mm�coupon.�The�weldshould�hold�firm�for�at�least�thelength�of�the�weld.

Butt�Joint�With�Backing�Weld�1�mm

The�butt�joint�with�backing�weld�is�done�using�three1�mm�coupons.

The�butt�joint�with�backing�weld�for�thetest�is�made�on�three�1�mm,�6061-T16alloy�coupons.�When�fitting�up�the�buttjoint,�butt�two�coupons�edge�to�edge,�andcenter�the�third�coupon�behind�the�joint.Keep�a�root�gap�between�the�two�topcoupons�about�2�-�3�metal�thicknesses.

The�participants�are�required�to�make�acontinuous�weld,�centered�on�the�joint,�inthe�vertical�and�overhead�positions.�Tackwelds�are�not�allowed.

To�achieve�the�required�penetration,�it�isimportant�to�begin�the�weld�by�using�thetailing�in�technique.�Tailing�in�will�placethe�cold�start�off�the�joint�and�allow�forproper�penetration�within�the�joint.�Thiswill�reduce�the�possibility�of�the�weldbead�separating�from�the�back�couponwhen�it�is�destructively�tested.

If�the�welding�machine�is�equipped�withthe�hot�start�feature�and�the participant�isfamiliar�with�it,�the�feature�may�be�used.

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Coach�the�butt�joint�with�backing�weldwith�the�participant�until�successful,repeatable�results�are�achieved.

The�I-CAR�Aluminum�GMA�(MIG)�Welding�Gauge�isused�when�doing�the�visual�inspection.

Visual�requirements�for�the�face�side�ofthe�butt�joint�with�backing�1�mm�weldinclude:

• no�cracks,�porosity,�skips,�orundercut.

• the�joint�and�crater�are�completelyfilled.

• a�bead�length�of�57�-�76�mm.• a�bead�width�of�5�-�10�mm.• a�bead�height�no�greater�than�2

mm.

The�backside�of�the�weld�is�being�inspected�forexcessive�melt-through.

Visual�requirements�for�the�backside�ofthe�butt�joint�with�backing�1�mm�weldinclude:

• no�cracks.• no�suck-back,�except�at�the�stop

point.• a�melt-through�width�no�greater

than�3�mm.• melt-through�height�no�more�than

2�mm.

The�butt�joint�with�backing�weld�is�avisual�failure�if�any�of�these�requirementsare�not�met.

Welds�that�pass�visual�inspection�must�bedestructively�tested.

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Destructively�test�the�butt�joint�with�backing�weldafter�it�passes�visual�inspection.

The�back�coupon�is�destructively�tested�further.

There�is�still�good�tearout�even�though�the�tailing�intechnique�was�not�used.

Further�testing�reveals�that�there�is�not�proper�weldpenetration.

Destructively�test�the�butt�jointwith�backing�1�mm�weld�using�thisprocedure:

1. Clamp�the�weld�sample�in�a�viseso�one�of�the�top�coupons�facesthe�front�of�the�vise,�and�the�weldbead�is�slightly�above�and�parallelto�the�vise�jaw.

2. Use�a�wide,�flat-jawed�lockingpliers�to�bend�the�upper�couponback�and�forth�until�it�breaks�freefrom�the�backing.

3. Reverse�the�weld�sample�in�thevise�and,�similarly,�break�theremaining�coupon�from�thebacking.

4. Inspect�each�face�coupon�formetal�tearout.�Also�inspect�theweld�bead.�The�weld�is�good�ifthere�is�metal�tearout�on�each�ofthe�face�coupons�for�the�lengthof�the�weld�and�the�weld�holdsfirm�on�the�backing�piece.�Thecoupons,�and�not�the�weld,�shouldbreak�to�pass�the�butt�joint�withbacking�weld.

5. Grasp�the�back�coupon�on�eachend,�bend�both�ends�back.�The

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weld�bead�should�not�lift�off�theback�coupon.

Plug�Weld

The�plug�weld�uses�two�1�mm�coupons.

The�plug�weld�for�the�test�is�made�on�two1�mm�6061-T6�alloy�coupons.�One�of�thecoupons�has�an�8�mm�punched�hole�inone�corner.�This�coupon�is�lapped�ontothe�corner�of�the�other�coupon,�at�90°�toeach�other.

The�participants�are�required�to�makean�8�mm�plug�weld�in�the�verticalposition.�Tack�welds�are�not�allowed.Coach�the�plug�weld�with�the�participantuntil�successful,�repeatable�results�areachieved.

The�I-CAR�Aluminum�GMA�(MIG)�Welding�Gauge�isused�to�measure�the�weld�nugget�size.

Visual�requirements�for�the�face�of�theplug�weld�include:

• no�cracks,�porosity,�skips,�orundercut.

• the�crater�and�hold�are�completelyfilled.

• a�nugget�height�no�greater�than�3mm.

• a�nugget�diameter�of�11�-�15�mm.

The�backside�of�the�weld�is�being�inspected�forexcessive�melt-through.

Visual�requirements�for�the�backside�ofthe�plug�weld�include:

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• no�cracks.• a�melt-through�diameter�is�at�least

3�mm�but�no�larger�than�8�mm.• a�melt-through�height�at�least�level

(no�suck-back)�with�the�bottom,but�no�higher�than�3�mm.

The�plug�weld�is�a�visual�failure�if�any�ofthese�requirements�are�not�met.

Welds�that�pass�visual�inspection�must�bedestructively�tested.

Destructively�test�the�plug�weld�after�it�passes�visualinspection.

Destructively�test�the�plug�weld�using�thisprocedure:

1. Clamp�the�bottom�coupon�in�thevise�so�the�face�of�the�weld�facesthe�front�of�the�vise.

2. Keeping�the�two�coupons�parallelto�each�other,�twist�off�the�topcoupon�until�it�breaks�free�fromthe�bottom�coupon.

3. There�must�be�a�tearout�hole�in�thebottom�coupon�at�least�5�mm�indiameter.

Safety

Appropriate�safety�gear�must�be�worn�while�welding.

For�this�event,�participants�must�have:

• a�welding�helmet�with�plastic�lenscover.

• welding�gloves.• safety�glasses,�which�must�be�worn

under�the�helmet.• a�welding�respirator.• leather-cape�welding�sleeves.

(optional)

Shown�are�some�of�the�required�tools.

Additionally,�participants�must�have:

• side-cutting�pliers.

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• regular�pliers.• locking�pliers.• an�I-CAR�Aluminum�GMA�(MIG)

Welding�Gauge.• a�stainless�steel�wire�brush.• auxiliary�lighting�(optional).

Q.�Why�wear�a�respirator?�Isn't�that�thepurpose�of�the�ventilation�system?

A.�It�is�a�necessary�piece�of�safetyequipment.�Welding�fumes�can�get�intolungs�and�cause�respiratory�problems.Breathing�the�fumes�in�for�a�length�of�timecan�lead�to�Parkinson's�disease.

Q.�What�about�the�helmet?�What�strengthof�filter�plate�should�there�be?

A.�At�least�11

Q.�Why�safety�glasses?�Doesn't�a�helmettake�care�of�that?

A.�Sparks�can�get�inside�a�helmet�and�intoyour�eyes.�Also,�wearing�safety�glasses�isan�OSHA�requirement�in�the�shop�area�foreveryone.

Q.�Why�say�"cover"�before�striking�anarc?

A.�This�makes�everyone�in�the�immediatearea�aware�to�take�safety�precautions.

Q.�What�is�the�purpose�of�hearingprotection?�Welding�isn't�that�loud,�is�it?

A.�Any�environment�where�you�haveto�shout�to�be�heard�requires�hearingprotection.�Also,�this�is�ear�protectionfrom�sparks�that�get�under�the�helmet.

Q.�What�about�in�your�pockets,�whatcan't�you�have?

A.�Matches,�lighters,�anything�a�sparkcould�set�off

Q.�What�should�be�nearby�the�weldingarea?

A.�A�fire�extinguisher

Refer�to�Video:�Safety�Overview�in�thepresentation.�This�video�provides�anoverview�of�safety�considerations�withinthe�repair�facility�environment.

Module�Wrap-Up

Topics�discussed�in�this�moduleincluded:

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• the�test�parameters�of�theI-CAR�Welding�Training�&Certification™:�Aluminum�GMA(MIG)�Welding�event.

• visual�inspection�criteria�for�thebutt�joint�with�backing,�fillet,�andplug�welds.

• destructive�testing�criteria�for�thewelds.

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