钒及奥氏体化温度对Mn-Cr系贝氏体型非调质钢过冷奥氏体连续冷却转变行为的影响  

Effects of Vanadium and Austenitizing Temperature on Continuous Cooling Transformation Behavior of Mn-Cr Type Bainitic Forging Steels

作　　者：王占花 惠卫军[1] 陈祯 张永健[1] 赵晓丽 WANG Zhanhua;HUI Weijun;CHEN Zhen;ZHANG Yongjian;ZHAO Xiaoli(School of Mechanical,Electronic and Control Engineering,Beijing Jiaotong University,Beijing 100044,China)

机构地区：[1]北京交通大学机械与电子控制工程学院,北京100044

出　　处：《材料导报》2020年第18期18145-18151,18158,共8页Materials Reports

基　　金：国家重点研发计划项目资助(2016YFB0300100)。

摘　　要：为了研究V在贝氏体非调质钢连续冷却过程中的作用,运用热膨胀法测定了添加0.13%(质量分数,下同)V与未添加V的Mn-Cr系贝氏体非调质钢在不同奥氏体化温度(900℃、1050℃、1150℃)下的连续冷却相变行为,结合硬度法及金相法获得了实验钢的过冷奥氏体连续冷却转变曲线(CCT曲线)。结果表明,实验钢的CCT曲线受V及奥氏体化温度的影响,提高奥氏体化温度有助于获得贝氏体组织。当奥氏体化温度为900℃时,连续冷却过程中难以获得全贝氏体(≥90%贝氏体,体积分数)组织;当奥氏体化温度提高到1050℃和1150℃时,则可在较低的冷却速度下获得全贝氏体组织。奥氏体化温度为900℃时,V对CCT曲线具有较为显著的影响,贝氏体相转变的冷却速度范围和贝氏体含量增大;当奥氏体化温度提高到1050℃和1150℃时,V元素降低了获得全贝氏体组织的最低冷却速度,从0.83℃/s和0.26℃/s分别降低为0.43℃/s、0.16℃/s,且扩大了贝氏体相变范围,在低至0.08℃/s的冷却速度下即可获得贝氏体组织。添加V元素能够提高实验钢的硬度,但提高程度受奥氏体化温度及冷却速度的影响。在奥氏体化温度为900℃、冷却速度为0.88℃/s时硬度增量达到峰值(66HV5);在奥氏体化温度为1050℃和1150℃时,硬度增量明显降低,硬度增量峰值分别为38HV5和30HV5,且对应的冷却速度显著降低,分别为0.17℃/s和0.08℃/s。The present study was attempted to explore the effects of V and austenitizing temperature on continuous cooling transformation(CCT)beha-vior of bainitic forging steel.Mn-Cr type bainitic forging steels microalloyed with V(0.13wt%)and without V(0wt%)were austenitized at three different temperatures(900℃,1050℃and 1150℃)and then continuously cooled by using thermal dilatometer to study their CCT beha-vior.Microstructural observations and Vickers hardness measurements of the cooled samples were carried out as complements for the accurate plot of the CCT diagrams.The results show that both V and austenitizing temperature have significant influence on the CCT diagrams.It was difficult to obtain full bainitic(≥90vol%bainite)microstructure when austenitizing temperature was 900℃,while it could be obtained at relatively lower cooling rate when the austenitizing temperature was raised to 1050℃and 1150℃.When austenitizing temperature was 900℃,V showed notable effect on the CCT diagram and the cooling rate range obtaining bainite was broadened and the bainite fraction was enhanced.When the austenitizing temperature was increased to 1050℃and 1150℃,the lowest cooling rate obtaining full bainitic microstructure was lo-wered from 0.86℃/s to 0.43℃/s for austenitizing temperature of 1050℃and from 0.26℃/s to 0.16℃/s for austenitizing temperature of 1050℃,and the bainitic transformation range was broadened to as low as 0.08℃/s by the addition of V.It is also found that the hardness was increased by the addition of V and this increase degree depends on austenitizing temperature and cooling rate.A peak value of hardness increase as high as 66HV5 at cooling rate of 0.88℃/s could be obtained for austenitizing temperature of 900℃,while the peak value of hardness increase was significantly decreased to 38HV5 at cooling rate of 0.17℃/s for austenitizing temperature of 1050℃and to 30HV5 at cooling rate of 0.08℃/s for austenitizing temperature of 1150℃.

关 键 词：贝氏体型非调质钢 钒 奥氏体化温度 连续冷却转变曲线 微观组织 

分 类 号：TG142.1[一般工业技术—材料科学与工程]