简介：EffectsofalloyelementsonthemicrostructureandcrackresistanceofFe-C-Crweldsurfacinglayerwereinvestigated.Theresultsshowthatmicrostructuresofthelayermainlyconsistofcarbidesandaustenitematrix.IncreasingCandCrcontentsimpairthecrackresistanceofthelayerduetoincreasedamountofbrittlecarbides.TheadditionofNi,NborMoimprovesthecrackresistanceofFe-C-CrweldsurfacinglayerbyincreasingtheamountofausteniteandformingfineNbCorM7C3carbidesinthelayer.But,theexcessiveNb(>2.50wt%)orMo(>1.88wt%)impairsthecrackresistanceofthelayer,whichhasrelationwithincreasedcarbidesorcarbidecoarseningandaustenitematrixsolidsolutionstrengthening.ThepropercombinationofC,Cr,Ni,NbandMocanfurtherimprovenotonlythecrackresistanceofFe-C-CrweldsurfacinglayerbutalsotheerosionresistanceasaresultoffineNbCandM7C3carbidesdistributinguniformlyinaustenitematrix.Theoptimallayercompositionsare3.05wt%C,20.58wt%Cr,1.75wt%Ni,2.00wt%Nband1.88wt%Mo.

简介：Inthispaper,theweldpoolshapecontrolbyintelligentstrategywasstudied.Aneuronself-learningPSDcontrollerforbacksidewidthofweldpoolinpulsedGTAWwithwirefillerwasdesigned.ThePSDcontrolarithmeticwasanalyzed,simulatingexperimentbyMATLABsoftwarewasdone,andthevalidatingexperimentsonvariedheatsinkworkpieceandvariedgapworkpieceweresuccessfullyimplemented.Thestudyresultsshowthattheneuronself-learningPSDcontrolmethodcanattainaperfectcontroleffectunderdifferentsetvaluesandconditions,andissuitablefortheweldingprocesswiththevariedstructureandcoefficientsofcontrolmodel.

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简介：Thepapergivesananalysisontechnicalcharacteristicsofrepairtechniquesforfrictionstirweldingdefects.Toovercomethedefects,anewrepairtechnique,inertiafrictionpullplugwelding(IFPPW),wasresearchedanditsequipmentwasdevelopedaswell.ElementarydatumwasachievedbyinvestigatingtheinfluencesoftechnologicalparametersonmechanicalpropertiesandbyanalyzingthestructuralcharacteristicsofrepairjointwithIFPPW.ThestudyshowsthatthestabilityandreliabilityofweldingprocessofIFPPWcanbeguaranteedthroughtheconstantenergyfromtheflywheel.Integratedwiththeadvantagesoffrictionpullplugwelding,theIFPPW,freefrombackanvil,isconsideredasapromisingtechniqueinrepairofterminationkeyholeofbobbintoolfrictionstirweldingandpoint-likedefectsinaluminumalloywelding.

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简介：Thispaperstudiedthespotweldingstructureofultra-highstrengthsteel22MnB5.ANSYSsoftwarewasadoptedtosimulateitsstaticstrength;BS5400algorithmwasusedtocalculatethefatiguelife;andthegroupingmethodwasusedtotestthefatigueperformanceoftensileshearspotweldspecimens.Thesimulationresultswereingoodagreementwiththeexperimentalvalues.Basedonthevalidationofthesimulationmethod,influencesofdifferentstructuralparametersonstaticstrengthandfatiguelifewereexploredbyadoptingsinglefactor.Theresultsshowedthatwithintheselectedstructureparameterrange,increaseofthesheetthickness,nuggetdiameter,sheetwidthandoverlappinglengthcanleadtolongerfatiguelife.Besides,thefatiguelifeofspotweldtookonalinearrelationshipwiththeoverlappinglength,aDoseResprelationshipwiththesheetthickness,andasingleexponentialdecayrelationshipwiththesheetwidthandthenuggetdiameter.Moreover,inordertoestimatetheimpactfromvariousparametersonthefatiguelifeofthespecimens,theTaguchiorthogonaldesignmethodwasappliedinthesimulationdesign.Thesimulatingresultindicatedthatinfluenceofthesheetthicknessonfatiguelifewasthemostsignificant.Inaddition,theeffectsofnuggetdiameter,sheetwidthandoverlappinglengthonfatiguelifewerereducedinturn.

简介：Inthisstudy，theweldingthermalcyclecurveexhibitedtwotemperaturepeaksinhighheat-inputtwin-wireseparate-poolsubmerged-arcweldingandcoarse-grainedheataffectedzoneexistedintheweldedjoint.Theinclusionsofprimaryweldmetalandcoarse-grainedheataffectedzoneofCe-addedSAWshouldbeAl203,MnO,Si02,TiO,Ce2S3,CeS,Ce202SandCe203.Undertheeffectofweldingthermalcycle,oxy-sulfidesinclusionsofCe,thediameterofwhichwaslessthan2.0|Jim,slightlygrewlarger,butthecompositionandtypeoftheinclusionsdidn，tchange.ThemicrostructureofthelargeheatinputweldmetalhadacicularferritethatCeoxidesulphideparticlesinducednucleationandproeutectoidferrite.Inthecoarse-grainedheataffectedzoneofweldmetal,home-positionprecipitationofacicularferriteandsympatheticacicularferritewerebothobserved.Itwassupposedthatpreviouscrystalcellsofacicularferriteinaustenitegrainpromotedhome-positionprecipitationofacicularferrite.Meanwhile,sympatheticacicularferritetendedtonucleateattheprimaryacicularferritegrainboundaries,wherehighdislocationdensitywaslocated,andgrewinsidetheneighboringcarbon-depletedausteniticregions.Thegranularbainitenucleatedintheausteniticzonewithhighcarboncontentclosetoacicularferriteandsympatheticacicularferrite.

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简介：Duetothedisturbancesofspatters,dustsandstrongarclight,itisdifficulttodetectthemoltenpooledgeandtheweldlinelocationinCO2weldingprocesses.Themedianfilteringandself-multiplicationwasemployedtopreprocesstheimageoftheCO2weldinginordertodetecteffectivelytheedgeofmoltenpoolandthelocationofweldline.TheB-splinewaveletalgorithmhasbeeninvestigated,theinfluenceofdifferentscalesandthresholdsontheresultsoftheedgedetectionhavebeencomparedandanalyzed.TheexperimentalresultsshowthatbetterperformancetoextracttheedgeofthemoltenpoolandthelocationofweldlinecanbeobtainedbyusingtheB-splinewavelettransform.Theproposededgedetectionapproachcanbefurtherappliedtothecontrolofmoltendepthandtheseamtracking.

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简介：Metallurgicalmodelingofsynergisticmicrocrackself-repairmenduringweldingsinglecrystalandpolycrystallinesuperalloysofhigh-temperatureaerospacematerialshasbeenproperlyestablished.Theideaofimprovementofnickel-basedsuperalloysweldabilitythroughnon-equilibriumsolidificationbehaviorofbackfilltoself-repairarterialcracknetworkisusefullyproposed.Crystallographiccontrolstrategyofcrackself-repairmenoffusionzoneinterdendriticsolidificationcrackingandheat-affectedzone(HAZ)intergranularliquationcrackingistechnicallyachievable,indicatingthatoptimalniobiumalloyingbeneficiallyrefinesweldmicrostructure,stabilizestheprimarysolidificationpath,increasesthesolidificationtemperatureandconcomitantlydecreasestheweldpoolgeometry.High-carbongrainboundaryismorethermalstableandlesscontributestoincipientintergranularliquidfilmthanthatoflow-carbongrainboundary.Thetheoreticalpredictionsofcrackingsusceptibilityareindirectlyverifiedinarathersatisfactorymanner.Additionally,themetallurgicalmodelingenhancespredicativecapabilitiesandtherebyisreadilyapplicableforotheralloysystems.

简介：Basedontheoriesofheattransfer,physicalmetallurgyandhydro-mechanical,inordertoanalyzetheeffectofweldingparametersonspeciesanddistributionofreinforcingphasesvisuallyandlegibly,finiteelementsoftwareANSYSwasusedtosimulatetransienttemperaturefieldforSiC_p/AIin“in-situ”weld-alloying/plasmaarcwelding.Theresultsshowthatthecalculatedresultsapproximatelyagreedwiththeexperimentalmeasuredresults.Sothemodelisbasicallycorrectandcredible.Basedonthenumericalsolutionsandexperimentalresults,effectoftemperaturefieldindifferentweldingprocessparameters(weldingcurrent,weldingvelocity)onspeciesanddistributionofreinforcingphasesisanalyzed.Theresultsshowthatadjustingandoptimizingtemperaturefieldappropriatelyisaneffectivemethodtoobtainweldedjointwithbettermicrostructureandproperty.

简介：Themicrostructuresandprecipitatesinbasemetalsandheataffectedzones(HAZs)oftwoZr-Bmicroalloyedsteelswerecharacterizedbymeansofopticalmicroscopy(OM),transmissionelectronmicroscopy(TEM)andenergydispersivespectrum(EDS).Ithasbeenfoundthatprecipitatesoftensofnanometersinsizearepresentinthebasemetalsofbothsteels.Theaverageparticlesize,however,intheZr-BsteelwithTiislargerthanthatinthesteelwithoutTi.Afterthermalsimulations,inbothcases,theMnSsulfidescannucleateoncubic(Nb,Ti)(C,N)carbonitridesandnearlysphericalZr-bearingcompounds.TheprecipitatesintheHAZsofbothsteelsarecoarserthanthoseinthebasemetals,intherangesof150-200nmand50-100nmforTiaddedandTi-freesteels,respectively.

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简介：ToresearchtheeffectofZradditiononinhibitingaustenitegraingrowthofTi-bearinglowcarbonsteels,twosteelswithdifferentZrcontentswerepreparedusingalaboratoryvacuuminductionfurnace.TheperformanceofHAZunderweldthermalsimulationswasinvestigated.Theimpacttoughness,microstructureandthesecond-phaseparticleperformanceofHAZunderweldthermalsimulationswereinvestigated.TheHAZtoughnesswasimprovedfrom13Jto87Jbyadditionof0.010%Zrintothesteel,withthefracturemechanismchangingfromcleavagefracturetotoughnessfracture,whichwasmainlyattributedtothesecond-phaseparticlesthatwerepotenttonucleateacicularferriteinHAZduringwelding.Itwasconcludedthatthesecond-phaseparticlesTiOx+MnS,ZrO2+MnSorTiOx+ZrO2+MnSwerenucleatedonZrO2orTiOx(x=1.5,2).Thismethodcanbeappliedtograinrefinementbypromotingtheacicularferriteformationandgrowthduringlarge-scalewelding,asinthecasesofthicksteelplatesrequiringhigherheatinputsduringwelding.