铸态GCr15钢在连续加热过程中的奥氏体化动力学特征与组织演变

利用DIL805A热膨胀仪记录了铸态GCr15钢在不同的加热速率下(0.5、3、5、30、100 ℃/s)的线膨胀量,获得了不同加热速率下的热膨胀曲线和奥氏体体积转变分数曲线,研究了加热速率对奥氏体化的影响。采用高温光学显微镜对该钢在连续加热过程中的奥氏体转变过程进行了观察分析。研究表明:GC15钢在连续加热过程中的奥氏体转变可分为3个阶段:在760~790 ℃为珠光体向奥氏体的转变、(Fe, Cr)₃C_II向奥氏体中的溶解和奥氏体的成分均匀化温度分别为790~890 ℃及890 ℃以上。并且随着加热速率提高,相变临界温度提高,相变速率提高。在连续加热过程中,铸态GCr15钢的奥氏体转变是一个形核和长大交替进行的过程。

Austenitization kinetic characteristics and microstructure evolution of as-cast GCr15 steel during continuous heating

Linear expansion of the as-cast GCr15 steel with different heating rates (0.5, 3, 5, 30, 100 ℃/s) was recorded using DIL805A thermal dilatometer, and their respective thermal expansion curves and austenite volume transformation fraction curves were obtained. The effect of heating rate on austenitization of the as-cast GCr15 steel was studied. The austenite transformation process of the steel during continuous heating was observed and analyzed by means of a high temperature metallurgical microscope. The results show that austenite transformation of the GC15 steel during continuous heating can be divided into three stages: the transformation of pearlite to austenite (760-790 ℃), the dissolution of (Fe, Cr)₃C_II into austenite (790-890 ℃) and the austenite homogenization (>890 ℃). And as the heating rate increases, the critical temperature of phase transition increases, and the rate of phase transition increases. During the continuous heating process, the austenitic transformation of the as-cast GCr15 steel is an alternate process of nucleation and growth.