简介:309Lisakindofausteniticstainlesssteel.Thispaperdiscusses309L,whichwassmeltedandrolledinalab.Itsmicrostructuralcharacteristicsinstatesofas-cast,hot-rolling,cold-rollingandsolidsolutionwereinvestigatedrespectivelybyopticalmicroscope(OM).Itisfoundthat309Liscomposedofausteniteandresidualδ-ferriteundertheseconditions,andtheδ-ferritecannotbeeliminatedeasilybyheat-treatment.Itshotplasticityanddeformationresistancewereinvestigatedinaseriesofheatsim...
简介:Twothermo-mechanicalcontrolledprocesses(TMCP)includingcontrolledrollingandacceleratedcoolingareproposedfortheproductionofheavygaugeSUS304Lausteniticstainlesssteelplateswithdifferentstrengthsandothercharacteristics.BasedontherecrystallizationmechanismandcarbideprecipitationbehaviorofSUS304Lausteniticstainlesssteel,TMCPprovidesapowerfulmeanstocontrolthemicrostructureandprecipitationofthehotrolledsteelplatebythecontrolledrollingandacceleratedcoolingprocess.Thedislocationdensityandgrainsizearethemainfactorsindeterminingthestrengthofthestainlesssteelplates.Therefore,itisnecessarytostrictlycontrolthehotrollingparameters,includingparameterssuchasthefinishhotrollingtemperatureintherecrystallizationtemperatureregionandthetotalreductioninthenon-recrystallizationregion.Furthermore,inordertoavoidcarbideprecipitationandguaranteetheintergranularcorrosionresistanceofTMCPSUS304Lausteniticstainlesssteel,acriticalcoolingrateafterrollingisdetermined.
简介:选择可疑为急性胰腺炎患者50例,其中临床确诊有39例,分别用比浊法、碘-淀粉酶比色法进行血清脂肪酶、淀粉酶二种方法联合检测,结果39例患者中,脂肪酶和淀粉酶阳性率分别为92.3%、69.2%。观察39例确诊病例,8h内抽血检测脂肪酶、淀粉酶,二者都升高;12-24h内,血清淀粉酶达高峰,是参考值的3倍,脂肪酶继续升高;48h后,淀粉酶开始下降,脂肪酶达高峰,大于参考值3倍以上;第3天,淀粉酶降至正常,脂肪酶仍高于正常值上限;第6、8天,淀粉酶雏持正常水平,脂肪酶开始下降,但仍高于正常值上限;第10天后,脂肪酶降至正常。揭示急性胰腺炎时,血清淀粉酶增高时间较短,易漏诊,脂肪酶升高可持续10天,对诊断急性胰腺炎有较高特异性,将脂肪酶、淀粉酶二者联合检测有助于急性胰腺炎的诊断和预后的判断。
简介:FSWandTIGwereconductedon316Lstainlesssteel.Variationduringmicrostructureandpropertiesinjointsobtainedbydifferentweldingmethodswasstudied.TheresultsshowthattheeffectofseveremechanicalstirringandintenseplasticdeformationcreatafinerecrystallizedgrainintheweldingjointduringFSW.AsforTIG,thetemperatureofweldingjointexceedsthemeltingpointofweldedmaterialitself.Theentireweldingprocessbelongstothesolidificationofasmallmoltenpool;andthemicrostructureofthejointtakesonatypicalcastingstructure.Whentheweldingparameterswereselectedappropriately,theaverageultimatetensilestrengthofFSWjointscanreach493MPa,whichis83.6%ofbasemetal;theaverageelongationis52.1%ofbasemetal.TheaverageultimatetensilestrengthofTIGjointsis475MPa,whichis80.5%ofbasemetal;theaverageelongationis40.8%ofbasemetal.ThetensiletestofFSWjointsissuperiortotheTIGjoints.ThemicrohardnessofFSWjointcomparedtobasemetalandTIGjointhavingasignificantimprovement,whicharel95.5HV,159.7HVand160.7HV,respectively;grainrefinementstrengtheningplaysanimportantroleinenhancingthemicrohardness.TheelectrochemicalcorrosiontestsshowthatthejointofFSW316Lausteniticstainlesssteelhasagoodcorrosionresistance.
简介:ThegrainrefiningmechanismofC-Mnsteelsheetoncompactstripproduction(CSP)linewasinvestigatedinthisstudy.Thegrainwasabout100μmafterF1passanddecreasedallthewayoftherollingprocess(F2-F6)to15μm.Repeatedphasetransformationexperimentwasconductedtothesteelforgrainrefinement.Thephasetransformationat860℃and920℃canrefinethegrainsizeto7.5μm.
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:High-strengthsteelshavebeenwidelyappliedtoautomotivechassisparts.Inordertoformcomplexshapes,highholeexpansionratesandhighformabilityarerequired.Dualphase(DP)steelhasagoodformability,butapoorholeexpansionrate.Inthiscircumstance,anotherkindofsteelwhichhasamicrostructureofferrite-bainite,ratherthanferrite-martensite,hasbeenfoundtobeanalternativesolution.ItiscalledFBsteel.ThissteelwithSi,CandMnadditionsareappliedinthisstudy.Atwo-stepcooling...
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简介:A0.06%Clowcarbonsteelwasdeformedintorsionoverthetemperaturerange877-917℃ina2%H2-Argasatmosphere.Strainsof0.25-5.0wereappliedatstrainratesofε=0.04s-1andε=0.4s-1tostudytheformationofferritebydynamictransformation(DT)attemperaturesabovetheAe3.ThecriticalstrainforferriteformationbyDTwasaboutε=0.2anditsvolumefractionincreasedwithstrainanddecreasedwithtemperatureabovetheAe3.Averageferritegrainsizesof1.5μmto5μmwereproduced,whichdecreasedwithstrainrate.Atthelowerstrainrate(ε=0.04s-1)reversetransformation(RT)tookplaceduringdeformationonceanincubationtimeofabout40s,wasexceeded.Anincreaseinstrainratefromε=0.04s-1toε=0.4s-1arrestedRTduringtestingatalltemperaturesasthetotaltesttimesdidnotexceed13s.ThepresentworkshowsthatDTisfavoredathigherstrainratesbyincreasingthedrivingforce(i.e.storedenergy)andbysuppressingRT.