在Gleeble 1500热模拟试验机上对20CrMoNb齿轮钢进行了不同温度处理以及连续冷却相交实验.使用光学显微镜、透射电子显微镜以及膨胀曲线方法研究了齿轮钢20CrMoNb加热时奥氏体晶粒尺寸变化及连续冷却相交行为.实验结果表明,加热温度在1050 ℃以下时,奥氏体晶粒细小;超过此温度,NbC粒子数量因溶解而大大降低,对晶界的钉扎作用消失,奥氏体晶粒急剧粗化.20CrMoNb齿轮钢含有一定量的Mo、Nb元素,奥氏体比较稳定,出现先共析铁素体与珠光体的冷速很小.
Austenitizing at different reheating temperatures and continuous cooling transformation tests to 20CrMoNb gear steel were carried out using a Gleeble 1500 hot simulator. The evolution of austenite grain size after reheating and the continuous cooling transformation behavior were investigated by means of optical microscope, transparent electron microscope and dilatometry. The experimental results show that austenite grain grows slowly at the reheating temperatures lower than 1050 ℃. Exceeding this temperature, the amount of NbC particles is greatly decreased because of dissolution, and the pinning role of NbC particles on austenite grain disappears, which causes a rapid growth of austenite grain. The stability of austenite against the formation of proeutectoid ferrite and pearlite is high due to the addition of Mo and Nb, resulting in very low cooling rate of proeutectoid ferrite and pearlite microstructure.
参考文献
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