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:309Lisakindofausteniticstainlesssteel.Thispaperdiscusses309L,whichwassmeltedandrolledinalab.Itsmicrostructuralcharacteristicsinstatesofas-cast,hot-rolling,cold-rollingandsolidsolutionwereinvestigatedrespectivelybyopticalmicroscope(OM).Itisfoundthat309Liscomposedofausteniteandresidualδ-ferriteundertheseconditions,andtheδ-ferritecannotbeeliminatedeasilybyheat-treatment.Itshotplasticityanddeformationresistancewereinvestigatedinaseriesofheatsim...
简介:Traditionally,austeniticstainlesssteels304and316havebeenemployedincoastalregionsasroofingmaterialsunfortunately,theyareexpensiveandnotfullyresistanttopittingcorrosionunderseverecoastalcorrosiveenvironment.AferriticstainlesssteelB445Rwasdeveloped.Comparedwithaustenitic316L,B445Ris①lesscostly;②uperiorcorrosionresistantwithminormaintenanceforlong-termservice;③insusceptibletothermaldistortionintheweldingseam.B445Rsheetshowsahigheryieldstrengthandlowertensilestrength,lowerelongationandlowerwork-hardeningthanaustenitic316L.Itcanbeeasilyfabricatedanddeformedjustlikeplaincarbonsteel.Afterbending180o,thereisnooccurrenceof'cracking'ornoticeable'orangepeel'.Theformabilityoftheweldingseamisalsosatisfactory.ThepittingpotentialofB445Ris650mV,largerthanthatof304and316L,asshowninFig.1.ThecorrosionrateofB445Rsubmergedin6%FeCl,solutionis0.3-0.56g/(m2?h-1),muchlowerthanthatof316L,asshowninFig.2.ThesuperiorpittingcorrosionresistanceofB445RcanbeascribedtosynergeticeffectofhigherCrandMo.Dull-finishedB445RsheetshavebeenemployedastheroofingmaterialsforGuangzhouAsianGamesArena,asshowninFig.3.About380tof1.0mmB445Rwithdullfinishwasusedforroofingpanels.About100tof0.8mmB445Rwithhairlineorfluororesinpaintfinishwasusedforsidewallpanels.Thecompositeroofbuild-up(fromuptobottom)includes:①shinglesofferriticstainlesssteelB445R;②Kalzip-typestandingseamofaustenitic304;③water-proofDFM;④structuralsteel;⑤75mmthickinsulation;⑥secondarypurlinof150mm×100mm×4.5mmofgalvaniziedQ235;⑦0.8mmthickprofiledeckofgalvaniziedQ235;⑧acousticinsulation.Theroofingshinglesorpanelswiththesamewidthbutdifferentlengthwereformedbybendingfoursidesandfixedtoa'L'shapereinforcingframesofstainlesssteelbyfasteners.The'L'frameswasconnectedtoribsofthestandingseambyacl
简介:Twothermo-mechanicalcontrolledprocesses(TMCP)includingcontrolledrollingandacceleratedcoolingareproposedfortheproductionofheavygaugeSUS304Lausteniticstainlesssteelplateswithdifferentstrengthsandothercharacteristics.BasedontherecrystallizationmechanismandcarbideprecipitationbehaviorofSUS304Lausteniticstainlesssteel,TMCPprovidesapowerfulmeanstocontrolthemicrostructureandprecipitationofthehotrolledsteelplatebythecontrolledrollingandacceleratedcoolingprocess.Thedislocationdensityandgrainsizearethemainfactorsindeterminingthestrengthofthestainlesssteelplates.Therefore,itisnecessarytostrictlycontrolthehotrollingparameters,includingparameterssuchasthefinishhotrollingtemperatureintherecrystallizationtemperatureregionandthetotalreductioninthenon-recrystallizationregion.Furthermore,inordertoavoidcarbideprecipitationandguaranteetheintergranularcorrosionresistanceofTMCPSUS304Lausteniticstainlesssteel,acriticalcoolingrateafterrollingisdetermined.
简介:Thedull-finishferriticstainlesssteel(FSS)sheetB445RforarchitecturalroofinghasbeendevelopedbyBaosteel.ThissteelproductexhibitsexcellentcorrosionresistancesuperiortothatofSUS316Lwithalowercost.Itcanbeeasilyformedintoroofingpanelsbyordinaryprocesses.Moreover,thethermalstrainofitislessthanSUS316Lbecauseofitslowerthermalexpansioncoefficient,anditsreflectivityislowerduetothedull-finishtreatment.Allofthesefeaturesmakeitcapableofbeingusedasarchitecturalroofingmaterialsincoastalregions.
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.