奥氏体变形对22CrSH齿轮钢连续冷却相变的影响

Effect of deformation of austenite on continuous cooling transformation for 22CrSH gear steel

为了研究奥氏体变形对22CrSH齿轮钢连续冷却相变的影响,在Gleeble 1500热模拟机上,将 22CrSH钢在950℃变形0．4及未变形处理,然后连续冷却．利用膨胀曲线、光学显微镜、透射显微镜,结合各种腐蚀方法,分析了22CrSH钢相变行为及相变组织．研究表明:奥氏体变形使多边形铁素体加珠光体混合组织的临界冷速增大;当奥氏体变形及降低冷速时,大量的晶界仿晶型铁素体占据了奥氏体晶界,贝氏体相变向针状铁素体相变转变;变形使奥氏体在中温相变区稳定性增加,室温组织中M/A岛的数量增多．

In order to research the effect of austenite deformation on the continuous cooling transformation for 22CrSH gear steel, tested steel was deformed to the strain of 0 and 0.4, respectively, at 950℃ and followed by continuous cooling to room temperature using a Gleeble 1500 hot simulator. The transformation behavior and microstructure were investigated by means of dilatometric curves, OM, TEM and different etching methods. The experiment results show that the deformation of austenite increases the critical cooling rate of a polygonal ferrite plus pearlite microstructure. The grain boundary allotriomorphic ferrite decorates the austenite grain boundaries under the austenite deformation and the decrease in cooling rate, which causes a transition from bainite to acicular ferrite. The deformation enhances the stability of austenite against acicular ferrite reaction, resulting in the increase of M/A island.