35CrMo截齿材料热处理工艺优化研究

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1、密级公开分类号TG161XI’ANTECHNOLOGICALUNIVERSITY硕士学位论文题目:35CrMo截齿材料热处理工艺优化研究作者：黑体4号徐芳芳指导教师：程巨强教授申请学位学科：材料学2018年5月5日OptimizationofHeatTreatmentTechnologyfor35CrMoPickMaterialsDiscipline:MaterialScienceStudentSignature:SupervisorSignature:AbstractTheeffectsofdifferenth

2、eattreatmenttechnologiesonthemicrostructureandpropertiesofthe35CrMocuttingpicksteelwereresearchedthroughheattreatmentoptimizationexperiments,mechanicalpropertiesandmicrostructureanalysis,andthemorphologyobservationontheimpactspecimenfractionthroughtheScanning

3、ElectronMicroscopy(SEM).TheresultsshowthattheAc1andAc3phase-transitiontemperatureofthe35CrMosteelmeasuredbythehardnessmethodare750°Cand800°Crespectively.Withtheincreaseofthequenchingtemperature,thestrengthandhardnessoftheexperimentalmaterialsshowadownwardtren

4、dafterthehigh-temperaturetempering.Theoptimumquenchingtemperatureis800°C.Afterquenchingandhigh-temperaturetemperingforthe35CrMocuttingpicksteelbelow800°C,themicrostructureoftheexperimentalmaterialsaremainlycomposedofsorbiteandasmallamountoffinemassiveferrite,

5、afterquenchingandhigh-temperaturetemperingbeyond800°C,themicrostructureoftheexperimentalmaterialiscomposedofsorbite.Whenthequenchingtemperatureat800°Candholdingdifferenttime,thepeakoftheimpacttoughnessappearswhenholding40min,theoptimumheatingandquenchingtechn

6、ologyoftheexperimentalmaterialis800°C×40min.Whenquenchingat800°C,thetendencyoforganizationcoarseningoftheexperimentalmaterialsindifferentholdingtimeisnotobvious.Aftertemperinginhightemperature,alltheimpactfracturesoftheexperimentalmaterialsaretoughnessfractur

7、emorphology,andasmallamountofsulfideandoxideinclusionsexistontheimpactfractures.Whenquenchingat800℃andholding40min,andtemperingindifferenttemperatures,thehardnessandthetensilestrengthoftheexperimentalmaterialsshowadecreasingtrendwiththeincreaseoftemperingtemp

8、erature.Thetemperingbrittlenessappearswhentemperingtemperaturereaches300℃.Whentemperingat500°C,thehardnessandstrengthoftheexperimentalmaterialtendtodecreasewiththeincreaseoftheholdingtime