20CrMnTi渗碳齿轮钢中Ti(C,N)的粗化行为

基于第二相Ostwald熟化的相关理论,对5炉成分有细微差别的20CrMnTi渗碳齿轮钢中Ti(C,N)在930℃下的粗化规律进行了计算.结果表明,在930℃渗碳温度下分别保温1、2、4、8、16h,随着保温时间的延长,各炉钢中碳氮化钛颗粒均会发生一定程度的粗化,第二相的粗化速率系数m值越大,粗化行为越严重.在保温8h时,t时间后第二相的平均尺寸d_t变化范围为2.64~16.2nm,最大偏差在13nm左右;保温16h时,d_t变化范围为3.33~20.4nm,最大偏差约为17nm,表明Ostwald熟化作用对Ti(C,N)第二相颗粒尺寸的影响不大.对钉扎奥氏体晶界、阻止奥氏体晶粒长大起主要影响作用的是第二相颗粒的初始尺寸.

Ostwald ripening of Ti(C,N) in 20CrMnTi gear steels

Based on the theories of Ostwald ripening, the coarsening law of Ti(C, N) in 20CrMnTi gear steel was calculated at 930℃. The results show that when the holding time is 1, 2, 4, 8, 16 h, with the increase of holding time, the coarsening of Ti(C, N) particles would occur to some extent. While the coarsening rate coefficients m of second phase is greater, the coarsening is more serious. The range of d_t which is the average size of the second phase at t time is 2.64-16.2 nm and 3.33-20.4 nm when the holding time is 8 h and 16 h respectively with the maximum deviation 13 nm and 17 nm apart. So Ostwald ripening has little effect on the particle size of second phase Ti(C, N), and it is the original size of the particles that has the main influence on pinning the grain boundaries and preventing austenite grain growth.