25CrMoA钢奥氏体冷却转变参数的确定

Determination of Austenite Cooling Transformation Parameters of 25CrMoA Steel

采用热膨胀法、末端淬火法与金相和硬度分析等试验手段对25Cr Mo A钢加热转变临界点和880℃奥氏体化后的连续冷却转变参数进行了确定.结果表明:25Cr Mo A钢加热转变的临界点Ac1和Ac3分别为758℃和841℃.经880℃奥氏体化的25Cr Mo A钢冷却后获得马氏体和贝氏体组织的临界冷却速度分别为127℃/s和44℃/s,而在冷却速度低于43℃/s时,将有铁素体和珠光体组织同时出现.相应地,880℃淬火时25Cr Mo A钢钢棒1/2半径处获得马氏体+贝氏体的临界直径约为48 mm.

The critical transition points of 25CrMoA steel in the heating process and the continuous cooling transformation characteristics of 25CrMoA steel austenite cooled from 880℃to room temperature are studied by thermal expansion method,end quenching method,metallographic analysis and hardness analysis methods.The results show that 25CrMoA steel critical transition points Ac 1 and Ac 3 are 758℃and 841℃respectively in the heating process.The critical cooling rates of obtaining martensite and bainite microstructure after austenitizing 25CrMoA steel heated at 880℃are 127℃/s and 44℃/s respectively.However,the ferrite and pearlite microstructures will appear when the cooling rate is lower than 43℃/s.Accordingly,the critical cooling diameter of the 25CrMoA steel bar 1/2 radius getting martensite+bainite when quenched at 880℃is about 48 mm.