稀土对x80管线钢拉伸性能与组织变化的研究

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1、内蒙古科技大学硕士学位论文AbstractThesolubilityofRareearthinthesteelisextremelylow,whenthequantityofrareearthinsteelchanges,microstructureandperformanceofsteelwillhavesignificantchange.Atthesametime,thequantityofrareearthelementsdissolvedinsteelaffectsthedissolutionandprecipitationofmicroelementaswell

2、astherecrystallizationprocess,asaresult,themechanicalpropertyofsteelvaries.ThisarticleisbasedonX80pipelinesteelandtheinfluenceofrareearthonmicrostructure, tensilepropertiesandmicroorientationarestudiedsystematically.Structurevariationin thicknessdirectionundertensionisstudiedwithopticalmi

3、croscope(OM)andscanningelectron microscope.Ansyssimulationsoftwareisusedtodescribingtheinfluenceofrareearthin tensionandcomparedwiththeexperimentsresults.Withthehelpofelectronbackscattered diffraction(EBSD),themacroscopictextureoffractureundertheconditionoftensionis analyzed.Therelationsh

4、ipbetweenfracturemicrostructure,macrotextureandmicro orientationsandhighgradepipelinesteelmechanicalpropertiesisobtainedwhichprovidea thoreticalandexperimentalbasisforengineeringapplication.MicrostructureobservationshowsthatthemicrostructureofX80pipelinesteelunder rollingstatechangesfroma

5、xialferritetransformstosmalluniformlydistributedflakebainite structureandthestructureisobviouslyrefined.TheImage-Proplusstatisticalresultsshowthat thegrainsrefinefrom13.26μmto12.94μm.Combiningtheresultsoftensionexperiments, conclusioncanbedrownthatthemechanicalpropertygetsanotableimprovem

6、entwiththe addingofrareearthelements,thetensilestrengthgets734MPawhichis13%higherthanthe steelwithoutrareearthelements.Thesimulationsshowthatthedistancethatequivalentstress declinegentlybecomeslargerform2.31mmto2.45mm.Astheincreaseofthisdistance, equivalentstressdeclinesandnearthecenterof

7、fracture,thelargestequivalentstainsare0.1、1.02744.Theobservationoffractureshowsthatcrackextensionedgebecomesserratedwithrareearthelements,pathchangesignificantly.Fractureanalysisshowsthattheadditionofrareearth II内蒙古科技大学硕士学位论文canimprovethefracturemorphologyofthepipel