简介:Precipitationstrengtheningaswellassolutionstrengtheningiskeymechanismforheatresistantsteels.Itisveryimportanttocharacterizetheprecipitatesin9%Crferriteheatresistantsteels,especiallytoshowthenanometer-sizedparticles.Bytransmissionelectronicmicroscopeattachedwithanenergydispersivespectrometeraswellasopticalmicroscope,scanningelectronicmicroscope,themicrostructureandchemicalcompositionofprecipitatesina9%Crheatresistantsteelafterdifferentheattreatmentswereinvestigated.ItwasfoundthatthemicrostructureofnormalizedsamplewasmartensitewithfineNbCandFe3C.Themicrostructureoftemperedsampleistemperedmartensite,andtheremainlyweretwotypesofprecipitates,M23C6withthesizerangeof50-300nmandMXwiththesizeof10-100nm.SuperfineM23C6precipitatedpreferablyonpriorausteniticgrainboundariesandmartensiticlathboundaries,whilenanometer-sizedMXprecipitatesweredistributedrandomly.Aftershort-termcreep,Lavesphaseformedalonggrainboundariesofthe9%Crsteel,andM23C6andMXprecipitateswerefoundtobecomecoarser.Moreinformationaboutprecipitatesinthe9%Crsteelhadbeenexhibitedbyatomicforcemicroscopy.Thereby,distribution,sizeandshapeoftheprecipitatesaswellastheircompositionsandstructureswererevealed.
简介:Theeffectsofthefinalelectromagneticstirring(EMS)onthesolidificationstructureof60Si2CrVAThighstrengthspring(HSS)steelofcontinuouscasting(CC)billetshasbeenstudied.Theanalysisofthesolidificationstructureisbasedonthecomparisonbetweenthemacrostructure,microstructure,carbonsegregationanddefectsofthe60Si2CrVATbilletwithmold-electromagneticstirring(M-EMS)andthosewiththeM+finalsolidificationzoneelectromagneticstirring(F-EMS).ItisfoundthatthesolidificationstructureofthebilletwiththeF-EMSisimprovedwiththetightnessofthebilletandtheincreaseintheratiooftheequiaxedstructure,theinnerporosityandtheshrinkageareremarkablyreduced,andthattheratioofcentralcarbonsegregationsharplydecreases.Meanwhile,thesecondarydendritearmspacing(SDAS)isimproved,andtheratioofcentralequiaxedgrainconsiderablyincreases,whichresultsinfinergrains.Therefore,thequalityofthebilletisenhancedwiththeF-EMS.