Nb-V复合弹簧钢60Si2CrVAT过冷奥氏体连续冷却转变

Continuous cooling transformation of under-cooled austenite for Nb-V microalloyed spring steel 60Si2CrVAT

利用DIL 805A淬火变形膨胀仪测定了提速列车用Nb-V复合微合金化弹簧钢60Si2CrVAT过冷奥氏体的连续冷却转变曲线,并结合金相-硬度法探讨了不同冷速下实验钢组织的变化,分析了Nb含量对60Si2CrVAT过冷奥氏体的连续冷却转变的影响.结果表明:Nb含量的增加,促进了高温、中温转变,且珠光体转变区间随之变宽,马氏体转变点由284.2℃降低到258.3℃;铁素体消失的冷速由0.3℃.s-1提高到0.5℃.s-1,珠光体消失的冷速由2℃.s-1提高到3℃.s-1,贝氏体消失的冷速也相应地由3℃.s-1提高到5℃.s-1,贝氏体开始出现的冷速由0.4℃.s-1提高到0.6℃.s-1,马氏体出现的冷速同为1℃.s-1.

The continuous cooling transformation curves of under-cooled austenite in Nb-V microalloyed spring steel 60Si2CrVAT were measured by using a DIL805A quenching deformation dilatometer.The microstructure changes of under-cooled austenite in the tested steels at different cooling rates were studied by the metallographic method coupling with the microhardness method.The effect of Nb content on continuous cooling transformation of the tested steels was analyzed.The experimental results show that with the increase in Nb content,the high-temperature and medium-temperature phase transitions were promoted,the range of pearlitic transformation was widened,and the temperature of Ms point decreased from 284.2℃ to 258.3℃.The cooling rate for ferrite disappearance increased from 0.3℃·s-1 to 0.5℃·s-1,for pearlite disappearance from 2℃·s-1 to 3℃·s-1,and for bainite disappearance from 3℃·s-1 to 5℃·s-1.The cooling rate for bainite transformation occurrence increased from 0.4℃·s-1 to 0.6℃·s-1,while for martensite occurrence kept the same cooling rate of 1℃·s-1.