Using the orthogonal array with grey relational analysis to optimize the laser hybrid welding of a 6

982HRKimandKYLee

usedtoverifytheanalysisresults.Finally,usingan

analysisofvarianceapproachsignificantprocess

parametersforthehybridweldingareinvestigated.

2EXPERIMENTALPROCEDURE

Thebasemetalusedinthisstudyisa6061-T6alumi-

niumalloyandeachplateisofsize150·300·2mm

andusedforsquaregrooveweldingofabuttjoint.

Thechemicalcompositionofthealloyisgivenin

Table1andthemechanicalandthermalproperties

arelistedinTable2.Aschematicdiagramofthe

hybridweldingsystemisshowninFig.1andthe

experimentalset-upisshowninFig.2.Inthisstudy,

aNd:YAGdiodepumpedlaser(withamaximum

powerP0¼4.4kW)andagasmetalarcweldingmachine(withamaximumcurrentI0¼400A)intheDCarcmodeareused.

Basedontheorthogonalarrayapproachproposed

byTaguchi,18experimentswereperformedand

thengreyrelationalanalysiswasappliedtoinvesti-

gatetheperformancecharacteristicsofthehybrid

weldingapproach.

2.1Weldingparameterselection

Inordertoselecttheweldingparameters,theweld-

ingcodesforaluminiumrecommendedbythe

AmericanWeldingSociety[14,15]andthemanuals

forthelaserandgasmetalarcweldingequipment

wereconsulted.Eightweldingparameterswere

selected:theweldingwiretype,theshieldinggas,

Table1thelaserpower,thelaserfocus,thetravellingspeed,theweldingwirefeedrate,therootopeningtoler-ance,andthevoltage.Theseparametersdecidethequalityoftheweld-ing.ApreliminaryexperimentalweldingparameterwasdeterminedbyfollowingthestructuralweldingcodesobtainedfromtheAmericanWeldingSocietyandtheweldingequipmentmanuals.Afternumeroustrialexperiments,apreliminarysettingfortheweld-ingconditionswasobtainedwithouttheuseofgreyrelationalanalysis.ThepreliminarysettingsandweldtestresultsarelistedinTable3.However,theseresultssuggestthatitispossibletoobtainahigherweldqualityifanalternativeapproachsuchasgreyrelationalanalysisandDOEapproachareused.Thelevelofeachprocessparameterwaschosentobewithintheavailablerange.Theweldingexperi-mentswereperformedbysettingER5356orER4043solidweldingwire,withargonorheliumorwithoutashieldinggas,withthelaserpowerintherangefrom3to4kW,thelaserfocusintherangefrom0toÀ1mm,thetravellingspeedintherangefrom80to160mm/s,theweldingwirefeedrateintherangefrom4.5to6.5m/min,therootopeningtoleranceintherangefrom0to0.5mm,andthevoltageintherangefrom10to15V.Theselectedweldingpara-metersforeachlevelarelistedinTable4.2.2TheorthogonalarrayAfterselectionoftheeightparameters,theexperi-mentorderwasmadebycombiningweldingChemicalcompositionof6061-T6aluminiumalloy

Chemicalcomposition(wt%)

Si

0.40–0.8Fe0.7Cu0.15–0.40Mn0.15Mg0.8–1.2Cr0.04–0.35Zn0.25Ti0.15Alremainder

Table2Mechanicalandthermalpropertiesof6061-T6

aluminiumalloy

Mechanicalproperties

Density(·1000kg/m3)

Poisson’sratio

Elasticmodulus(GPa)

Tensilestrength(MPa)

Yieldstrength(MPa)

Elongation(%)

Hardness(Brinell)

Hardness(RockwellA)

Hardness(RockwellB)

Fatiguestrength(MPa)

Thermalproperties

Meltingpoint( C)

Thermalconductivity(W/mK)

5821672.70.3368.92902401695406096.5Fig.1Schematicdiagramofthehybridweldingsystem

JEM1070ÓIMechE2008Proc.IMechEVol.222PartB:J.EngineeringManufacture