轴承用8Cr4Mo4V钢稳定热处理期间相转变分析

Phase Transformation Analysis of 8Cr4Mo4V Steel for Bearing During Stable Heat Treatment

为了研究稳定热处理期间8Cr4Mo4V钢的组织转变及尺寸变化规律,采用热膨胀仪和差热分析仪测定经淬火和回火处理后的8Cr4Mo4V钢升温期间相变引起的尺寸及热流变化特征,分析了稳定热处理期间钢的相变特征,并采用扫描电镜观察了稳定处理后的微观组织。结果表明:在8Cr4Mo4V钢淬火后的回火升温期间,马氏体回火相变温度为132~243℃,残余奥氏体转变温度为215~303℃,马氏体分解为铁素体+碳化物的温度为278~420℃。随着稳定处理次数的增加,8Cr4Mo4V钢中的马氏体发生回火转变的温度及马氏体分解为铁素体+碳化物的温度逐渐升高,钢中亚稳相的稳定性增加。当进行3次稳定处理后,未检测到钢中发生马氏体回火相变,而马氏体分解为铁素体+碳化物的相变仍然存在。微观组织观察表明,随着稳定次数的增加,钢中析出的碳化物数量增多。

In order to study the microstructure transformation and dimensional change characteristics of 8Cr4Mo4V steel during stabili⁃zation heat treatment,the characteristics of dimension and heat flux changes caused by phase transformation during heating of 8Cr4Mo4V steel after quenching and tempering were measured by thermal dilatometer and differential thermal analyzer.The phase transformation char⁃acteristics of the steel during stabilization heat treatment were analyzed.The microstructure of the steel was observed by SEM.The results show that after quenching of 8Cr4Mo4V steel,during the temperature rise period of tempering,the tempering transformation temperature of martensite is 132-243℃,the transformation temperature of retained austenite is 215-303℃,and the decomposition temperature of martensite into ferrite and carbide is 278-420℃.As the number of stabilization treatments increases,the tempering transformation temper⁃ature of martensite and the decomposition temperature of martensite into ferrite and carbide gradually increase,and the stability of metasta⁃ble phase increases.After three stabilization treatments,no tempering transformation of martensite was detected,while the transformation of martensite into ferrite and carbide still existed.The microstructure observation shows that the amount of carbide precipitate increases with the increase of stabilization treatment numbers.