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GeneralWeldingDiscontinuitiesThefollowingdiscontinuitiesaretypicalofalltypesofwelding.Coldlapisaconditionwheretheweldfillermetaldoesnotproperlyfusewiththebasemetalorthepreviousweldpassmaterial(interpasscoldlap).Thearcdoesnotmeltthebasemetalsufficientlyandcausestheslightlymoltenpuddletoflowintobasematerialwithoutbonding.PorosityT istheresultofgasentrapmentinthesolidifyingmetal.Porositycantakemanyshapesonaradiographbutoftenappearsasdarkroundorirregularspotsorspecksappearingsingularly,inclustersorrows.SometimesporosityiselongatedandmayhavetheappearanceofhavingatailThisistheresultofgasattemptingtoescapewhilethemetalisstillinaliquidstateandiscalledwormholeporosity.Allporosityisavoidinthematerialitwillhavearadiographicdensitymorethanthesurroundingarea.ClusterporosityÆÆT iscausedwhenfluxcoatedelectrodesarecontaminatedwithmoisture.Themoistureturnsintogaseswhenheatedandbecomestrappedintheweldduringtheweldingprocess.Clusterporosityappearjustlikeregularporosityintheradiographbuttheindicationswillbegroupedclosetogether.ÀŒÀKáolJ¤QQ:68671554Slaginclusions9# arenonmetallicsolidmaterialentrappedinweldmetalorbetweenweldandbasemetal.Inaradiograph,dark,jaggedasymmetricalshapeswithintheweldoralongtheweldjointareasareindicativeofslaginclusions.Incompletepenetration(IP)orlackofpenetration(LOP)* occurswhentheweldmetalfailstopenetratethejoint.Itisoneofthemostobjectionablewelddiscontinuities.Lackofpenetrationallowsanaturalstressriserfromwhichacrackmaypropagate.Theappearanceonaradiographisadarkareawithwell-defined,straightedgesthatfollowsthelandorrootfacedownthecenteroftheweldment.Incompletefusion* isaconditionwheretheweldfillermetaldoesnotÀŒÀKáolJ¤QQ:68671554properlyfusewiththebasemetal.Appearanceonradiograph:usuallyappearsasadarklineorlinesorientedinthedirectionoftheweldseamalongtheweldpreparationorjoiningarea.Internalconcavityorsuckback…ù isconditionwheretheweldmetalhascontractedasitcoolsandhasbeendrawnupintotherootoftheweld.Onaradiographitlookssimilartolackofpenetrationbutthelinehasirregularedgesanditisoftenquitewideinthecenteroftheweldimage.Internalorrootundercut9謹 isanerosionofthebasemetalnexttotherootoftheweld.Intheradiographicimageitappearsasadarkirregularlineoffsetfromthecenterlineoftheweldment.UndercuttingisnotasstraightedgedasLOPbecauseitdoesnotfollowagroundedge.ÀŒÀKáolJ¤QQ:68671554Externalorcrownundercut¬¹ isanerosionofthebasemetalnexttothecrownoftheweld.Intheradiograph,itappearsasadarkirregularlinealongtheoutsideedgeoftheweldarea.Offsetormismatch¹ aretermsassociatedwithaconditionwheretwopiecesbeingweldedtogetherarenotproperlyaligned.Theradiographicimageisanoticeabledifferenceindensitybetweenthetwopieces.Thedifferenceindensityiscausedbythedifferenceinmaterialthickness.Thedark,straightlineiscausedbyfailureoftheweldmetaltofusewiththelandarea.ÀŒÀKáolJ¤QQ:68671554Inadequateweldreinforcement*á isanareaofaweldwherethethicknessofweldmetaldepositedislessthanthethicknessofthebasematerial.Itisveryeasytodeterminebyradiographiftheweldhasinadequatereinforcement,becausetheimagedensityintheareaofsuspectedinadequacywillbemore(darker)thantheimagedensityofthesurroundingbasematerial.ExcessweldreinforcementYØÇØ isanareaofaweldthathasweldmetaladdedinexcessofthatspecifiedbyengineeringdrawingsandcodes.Theappearanceonaradiographisalocalized,lighterareaintheweld.Avisualinspectionwilleasilydetermineiftheweldreinforcementisinexcessofthatspecifiedbytheengineeringrequirements.ÀŒÀKáolJ¤QQ:68671554Cracks¹ canbedetectedinaradiographonlywhentheyarepropagatinginadirectionthatproducesachangeinthicknessthatisparalleltothex-raybeam.Crackswillappearasjaggedandoftenveryfaintirregularlines.Crackscansometimesappearastailsoninclusionsorporosity.DiscontinuitiesinTIGweldsThefollowingdiscontinuitiesarepeculiartotheTIGweldingprocess.Thesediscontinuitiesoccurinmostmetalsweldedbytheprocessincludingaluminumandstainlesssteels.TheTIGmethodofweldingproducesacleanhomogeneousweldwhichwhenradiographediseasilyinterpreted.Tungsteninclusions9¨ .Tungstenisabrittleandinherentlydensematerialusedintheelectrodeintungsteninertgaswelding.Ifimproperweldingproceduresareused,tungstenmaybeentrappedintheweld.Radiographically,tungstenismoredensethanaluminumorsteel;therefore,itshowsasalighterareawithadistinctoutlineontheradiograph.ÀŒÀKáolJ¤QQ:68671554Oxideinclusionsareusuallyvisibleonthesurfaceofmaterialbeingwelded(especiallyaluminum).Oxideinclusionsarelessdensethanthesurroundingmaterialsand,therefore,appearasdarkirregularlyshapeddiscontinuitiesintheradiograph.DiscontinuitiesinGasMetalArcWelds(GMAW)ThefollowingdiscontinuitiesaremostcommonlyfoundinGMAWwelds.Whiskersareshortlengthsofweldelectrodewire,visibleonthetoporbottomsurfaceoftheweldorcontainedwithintheweld.Onaradiographtheyappearaslight,wirelikeindications.Burn-Throughç resultswhentoomuchheatcausesexcessiveweldmetaltopenetratetheweldzone.Oftenlumpsofmetalsagthroughtheweldcreatingathickglobularconditiononthebackoftheweld.Theseglobsofmetalarereferredtoasicicles.Onaradiograph,burnthroughappearsasdarkspots,whichare