淬火工艺对高速列车车轴用DZ2钢组织性能的影响

Effect of quenching process on microstructure and properties of DZ2 steel for high-speed train axle

采用OM、SEM、EBSD、室温拉伸试验和低温冲击试验,揭示了淬火工艺对高速列车车轴用DZ2钢组织和性能的影响。研究结果表明,经850℃两次淬火和650℃回火后,DZ2钢获得了最佳的力学性能。抗拉强度、屈服强度、断后伸长率和-40℃冲击吸收能量分别为874 MPa、773 MPa、24%和222 J。该工艺条件下原始奥氏体晶粒、马氏体板条束和板条块最为细小,其尺寸分别为14.9、6.9和1.32μm,较经950℃淬火和650℃回火后的分别细化了14.3、5.2和0.35μm,可有效抑制裂纹的扩展,提高低温韧性,韧脆转变温度由-103℃显著降低至-136℃。

The effect of quenching process on the microstructure and properties of DZ2 steel used for high-speed train axles is revealed by means of OM,SEM,EBSD,room temperature tensile test and low temperature impact test.The results show that after twice quenching at 850℃and tempering at 650℃,the optimum mechanical properties of DZ2 steel were obtained.The tensile strength,yield strength,elongation after fracture and impact energy absorption at-40℃of DZ2 steel are 874 MPa,773 MPa,24%and 222 J,respectively.Moreover,the prior austenite grain,martensite packet and block are the finest,with the size of 14.9,6.9 and 1.32μm,respectively,which are 14.3,5.2 and 0.35μm finer than those after quenching at 950℃and tempering at 650℃,respectively.And it is found that finer prior austenite grain boundaries,packet boundaries and block boundaries can effectively inhibit the crack propagation and improve the low-temperature toughness,resulting in the ductile-brittle transition temperature of DZ2 steel significantly reduced from-103℃to-136℃.