等温淬火对含铝无碳化物贝氏体钢组织和性能的影响

Effect of austempering on microstructure and mechanical properties of carbide-free bainitic steel with Al

通过对铝含量为0.60%、1.17%的两种含铝低合金钢进行不同工艺的等温淬火处理,获得了不同微观组织和力学性能的无碳化物贝氏体钢。利用光学显微镜、扫描电镜、透射电镜、X射线衍射仪以及冲击和拉伸试验研究了等温淬火工艺对无碳化物贝氏体钢组织性能的影响。结果表明,贝氏体未转变完成时,无碳化物贝氏体钢的微观组织由贝氏体型铁素体、残留奥氏体和较多马氏体构成;而贝氏体转变完成时,无碳化物贝氏体钢的微观组织由贝氏体型铁素体、残留奥氏和极少量马氏体构成;当贝氏体转变完成后,含0.60%Al钢中残留奥氏体尺度分布范围和含量均高于含1.17%Al钢,而1.17%Al钢则有比0.60%Al钢更加细小的贝氏体型铁素体板条;含0.60%Al钢的屈服强度略低于1.17%Al钢,但却表现出明显高于1.17%Al钢的冲击性能、抗拉强度和断裂总延伸率,综合力学性能更加优异。

Two carbide-free low alloy bainitic steels containing 0.60%and 1.17%Al were austempered with different processes and different microstructure and mechanical properties were obtained,and then the effect of austempering on the microstructure and properties of the tested steels was studied by using optical microscope,scanning electron microscope,transmission electron microscope,X-ray diffraction,as well as impact and tensile tests.The results show that when the bainitic transformation is incomplete,the microstructure of the carbide-free bainitic steels is composed of bainitic ferrite,retained austenite and a large amount of martensite,while the microstructure of the tested steels is composed of bainitic ferrite,retained austenite and a very small amount of martensite when the bainitic transformation is complete.And when the bainitic transformation is complete,the size distribution range and volume fraction of retained austenite in 0.60%Al steel are higher than those in 1.17%Al steel,while the bainitic ferrite lath of 1.17%Al steel is finer than that of 0.60%Al steel.The yield strength of 0.60%Al steel is slightly lower than that of 1.17%Al steel,but its impact property,tensile strength and total elongation after fracture are significantly higher than that of 1.17%Al steel,demonstrating much excellent comprehensive mechanical properties.