简介:ThehotrollingexperimentinvestigatesintotherelationshipbetweenthemicrostructuresandthemechanicalpropertiesofNb-TimicroalloyedsteelswithvariousTicontents.TheresultsindicatethattheeffectofthebainitefractionofNb-TimicroalloyedsteelsontheyieldstrengthofthesteelsisnotrelatedtoTicontent,whiletheslopeoftheHall-PetchrelationshipdecreaseswiththeincreaseofTicontent.Accordingly,theMisramodelfortheyieldstrengthofNb-Timicroalloyedsteelsismodified,andthefactorswhichcausethechangeintheslopeofHall-Petchrelationshiparediscussed.
简介:ThemorphologiesevolutionofvarioustypesofinclusionsinTi-IFsteelwereobservedbyaspecialdeptherosionmethod,andtheformationandevolutionprocesswerediscussed.TheresultsshowedthatthemaininclusionswereFeO·xMnObeforeAldeoxidizationandtheratioofintegratedoxygenandfreeoxygenwasinrangedof0.3to0.4.Inpresentstudy,themaineffectfactorsonthemorphologiesofAl2O3inclusionswere[Al]/[O]Free(solublealuminumdividefreeoxygen)andinitialfreeoxygen;clusterAl2O3wasformedeasilywithhighfreeoxygen([O]Free)andlow[Al]/[O](blew3inpresentstudy).Otherwise,thedendriticAl2O3wasformed;coral-likeAl2O3wasthemixtureofthedendriteAl2O3andsphericalAl2O3.SomeAl2O3·TiOxinclusionsappearedbecauseahigh[Ti]concentrationregionexistedaround70TiFe(containing70percenttitanium)particlesafter70TiFeaddition.ThemaximumsizesofAl2O3reached800μmwhen3minaluminumwasadded;asthetimepast,thelargesizeAl2O3decreasedsignificantly;themaximumsizeofAl2O3wasblew100μmand50μmincalmingsampleandtundishsamplerespectively.
简介:Thisstudyexaminesmechanismsforprovidingnucleitoequiaxedgrainsintheweldsofpureferriticstainlesssteel(FSS).TheadditionofthealloyelementTitopureFSS439causestheprecipitationofTiN,whichcanbenefitthecolumnar-to-equiaxedtransition(CET)ofgastungstenarcwelding(GTAW).Meanwhile,theinitialmorphologyoftheprecipitates,theconcentrationmultiplicationsofTi,N,etc.ofFSS439shouldbecontrolledtoinducetheformationofCETduringtheshortweldingprocess.
简介:InfluenceofdifferentcoolingratesonthemicrostructureandtheprecipitationbehaviorofNb-TimicroalloyedsteelwasinvestigatedbyCSLM,OM,SEMandEDS.Theresultsshowthattheprecipitationprocessofcarbonitridescanbein-situobservedbyCSLM,andwiththeincreaseofthecoolingrate,thedistributionofprecipitateschangesfromalongtheausteniticgrainboundariestowithinthegrains.Withtheincreaseofthecoolingrate,theproeutectoidferriticfilmbecomessmallerandsmallerandthendisappears,andtheoriginalausteniticgrainsbecomefinerandfiner.Inordertoobtainnon-filmlikeproeutectoidferritesornon-chainlikeprecipitatesalongtheausteniticgrainboundariesandfinerausteniticgrains,thecoolingrateshouldbeatleast5℃/s.
简介:Inordertoutilizetheadvantageofoxidesinstainlesssteel,theformationoftitaniumnitride(TiN)andoxide(TixOy)inthe17CrsteelwasinvestigatedbythecalculationofthefreeenergyofreactionandthermodynamiccalculationwithThermo-calcsoftware.Theresultindicatesthatthecompetitivereactionbetweenthedissolved[O]andthedissolved[N]withthedissolved[Ti]inmoltensteelresultsindifferentprecipitationsequencesofTiNandTixOy.TheprimaryprecipitationofTiNrequiresalow[O]andtheprimaryprecipitationofTixOyrequiresalow[N].Theincreaseof[Ti]causesahigherprecipitationtemperatureofTiNandTixOyinbothTi-NandTi-Oalloysystems.Equilibriumrelationsof[Ti]vs[N]and[Ti]vs[O]showthatthesolubilityproductsfallwiththedecreaseofthetemperature,andthentheprecipitationoftheinclusionsbecomeseasier.IntheTi-Oalloysystem,ahigh[O]andalow[Ti]arefavorabletotheprecipitationofTi3O5,andahigh[Ti]contentandalow[O]favorabletotheTi2O3precipitation.
简介:Abstract:Theeffectofstabilizingelements,suchasNbandTi,onthemicrostmctureandpropertiesoflowcarbonferriticstainlesssteel(FSS)hasbeeninvestigated.TheresultsoftheThermo-calcsimulationhaveshownthattheinterstitialelements,suchasCandN,maybecompletelystabilizedbytheadditionofNbandTi.WiththeincreaseofNbandTicontents,thea+γtwophasesgraduallytransfertoasingleα-phaseunderahightemperaturecondition,andthecontentofthecarbideM_(23)C_6graduallydecreases.ThemicrostructurehasindicatedthatthecombinedadditionofNbandTicanpromotetherecrystallizationofthebandstructureandformmoreuniformequiaxedgrains.Also,withtheincreaseofNbandTicontents,theelongation,ther-valueandthecorrosionresistanceofcold-rolledandannealedsheetsareimprovedprominently.IncomparisonwiththeeffectofTi,theadditionofNbismorebeneficialtotheincreaseofr-valueandthecorrosionresistance.
简介:Thepipelinesteelisusuallyproducedbyaddingniobiumandvanadiumalloyingelements.Thetitaniumalloyedpipelinesteelwasstudiedinthepapertoreducetheproductioncostandenhancethecompetitiveabilityofpipelinesteel.Thesteelcontaining0.070%Tiwasrefinedinthelaboratoryvacuumrefinefurnace.ThedynamicCCTcurveofdevelopedsteelwasconductedonGleeble-1500thermalsimulatorandmulti-passdeformationtestsofstudiedpipelinesteelwereperformedtosimulatetheCSPhot-rollingtechnology.Correspondingmicrostructureswereobservedandtheinfluencesofsuchtechnologyparametersasdeformationstrain,deformationtemperature,coolingrateandfinishingtemperatureetc.onmicrostructurewereanalyzed.ThedynamicCCTcurvewasobtained.ThetestresultsshowedthatthevolumefractionofacicularferriteinthemicrostructureofTi-microalloyedX70pipelinesteelincreasedobviouslywiththeincreaseofcoolingrateafterthermo-mechanicaldeformation.However,thevolumefractionofacicularferritevariesscarcelyafterthecoolingrateof20℃/s.InordertoobtainTi-microalloyedX70pipelinesteelwithexcellentcompoundmechanicalpropertieswhichhasacicularferriteasthemainidealmicrostructure,thecoolingrateshouldbecontrolledtobe20℃/sormore.Thehigherofthefinishingtemperature,themoreofthevolumeofacicularferriteandthelessofthevolumeofpolygonalferrite.Thequitefinemicrostructurecanbeobtainedbyloweringthefinish-coolingtemperature.TheresultshaveshownthatitispossibletoproducetheTi-additionX70pipelinesteelfromthepointofviewofmicrostructure.
简介:TheinfluenceofTiandNbonthemicrostructure,mechanicalproperties,andsecond-phaseprecipitationof430ferriticstainlesssteelwasinvestigated.Inadditiontoopticalmicroscopy,transmissionelectronmicroscopyandX-raydiffractionanalyses,tensiletests,andcarbonitrideextractionexperimentswereconductedtoinvestigatethemicroscopicmechanisms.TheresultsshowedthattheprimaryprecipitatesinSUS430ferriticstainlesssteelwereCr23C6,Mn23C6,andCr7C3,andtheprimarystrengtheningmechanismwasprecipitationstrengthening.WhenTiwasaddedseparately,themainprecipitateswereTiCandTiN.However,coarseTiCadverselyaffectedthemechanicalpropertiesofsteel.Whendouble-stabilizedwithTiandNb,coarseTiCwasreplacedbyfineNbC.Thetypeofprecipitationwasaltered,andprecipitationandsolidsolutionstrengtheningoccurred.Therefore,thetensilestrengthandplasticstrainratio(r-value)improvedto433.60MPaand1.37,respectively.
简介:Abstract:TheeffectofTiandNbontherecrystallizationandtherecrystallizedgrainsizeofthehot-rolledplatesandcold-rolledsheetsofultralowcarbonandnitrogen(ULCN)Cr18ferriticstainlesssteel(FSS)isinvestigated.Theresultsshowthattherecrystallizationofhot-rolledplatesandcold-rolledsheetswith0.29%Nbisdelayed,andtherecrystallizedgrainsaresignificantlyrefined.
简介:TheFe-Ti-Nmateralloywaspreparedthroughthein-situreactionofnitrogengaswiththeFe-Timelt.ScanningelectronmicroscoperesultsshowthattheparticlesuniformlydistributedintheironmatrixwereTiN.ThedeliberatelypreparedFe-Ti-Nmasteralloywasemployedforthe409Lferriticstainlesssteelinanattempttorefinetheas-castsolidificationstructure.ItwasfoundthattheeffectivenessofFe-Ti-Nmasteralloyonrefiningoftheas-cast409Lferriticstainlesssteelwasaffectedbyadditionlevel,holdingtimeandmeltstemperature.Itwasfoundthattheaverageequiaxedgrainsizedecreasedfrom1503μmto303μm,theproportionofequiaxedgrainzoneincreasedfrom14%to100%withincreasingtheFe-Ti-Nmasteralloyadditionlevelto2.5%.Theproportionofequiaxedgraindecreasedfrom85%to4%asthesolidificationtemperatureincreasedfrom1803Kto1883K.Whentheholdingtimereachedto8min,thesolidificationstructuresof409Lferriticstainlesssteelshowextremepointsintheproportionofequiaxedgrain.Itisclearthatthegrainrefiningefficiencygraduallyfadeawaywiththeincreasingoftheholdingtimeattheverybeginning.However,whentheholdingtimecontinuestoincreaseandexceedstheextremepoint,thegrainrefiningefficiencyoftheFe-Ti-Nmasteralloyrecoveredtoacertaindegree.Theexperimentalresultsmentionedabovehavebeenanalyzedintermsofthermodynamics.Underappropriateconditions,theFe-Ti-Nmasteralloyusedforgrainrefinementofthesolidificationstructureof409Lferriticstainlesssteelmayhavegoodprospectsforindustrialapplications.
简介:Thecompositionandproductiontechnologyofthetypeofhot-rolledsteelplateusedintwo-sidedenamelingwerebrieflydescribed.Themicrostructureandmechanicalpropertiesbeforeandafterenamelingwerecontrastivelyinvestigated,andtheprecipitatesinthesampleswereanalyzedusingtransmissionelectronmicroscopeandenergydispersivespectrometer.Theresultsshowtheferritegrainsizeofthesteelplateafterhigh-temperatureenamelfiringtobefine,withalargenumberofTiCandTi4C2S2precipitatesdispersedthroughouttheferritematrix.Aftertworoundsofenamelfiringatatemperaturerangeof800-890℃,itsyieldstrengthcanstillreach342MPa.Theresultsofahydrogenpermeationtestshowthatthehydrogenstoragepropertiesofthesteelplatearemuchbetterthanthoseofordinarystructuralcarbonsteel.Abetterbubblestructureintheenamellayercanbeobtainedbythissteelplate,withnofish-scaledefectsontheenameledsteel-platesurface.
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.
简介:Hydrogen,asatemporaryelementintitaniumalloys,isverygoodincontrollingmicrostructure.ThemicrostructureandphasetransformationofTi6A14ValloyareaffectedbytheamountofTiH,addedintothemeltofTi6A14Valloyduringtheinductionskullmelting(ISM)process.Thisprocess,calledmelthydrogenation,wasstudiedinthispaperthroughtheuseofopticalmicroscopy,scanningelectronmicroscopy(SEM)andtransmissionelectronmicroscopy(TEM).Theresultsareasfollows:aftermelthydrogenation,boththesolidificationmacrostructureandmicrostructureofTi6A14Valloyarerefined;theαphaseprecipitatesinalamellarformwiththeresidualβphasefromthegrainboundaries;δ-hydridesprecipitateduringthesolidificationprocessasaresultoftheexistenceofhydrogen.TheSphasewithanF.C.C.structurecanbeobservedbyTEMintheαphaselaminaeofspecimenswith1.25%TiH2.Inaddition,thedependenceofthemicrohardnessofspecimensontheweightpercentageofTiH,addedtothemeltduringtheISMprocesswasalsostudied.