等温温度对直接淬火配分超高强钢组织性能的影响

Effects of Isothermal Temperature on Microstructure and Mechanical Properties of Ultra High Strength Steel After Direct Quenching and Partitioning

对一种中碳低合金超高强钢进行直接淬火到马氏体区等温处理,采用场发射扫描电镜和X射线衍射仪等设备研究了等温温度对组织和力学性能的影响。结果表明:随等温温度升高,抗拉强度不断降低,屈服强度先降低后升高,冲击功先增加后降低,伸长率略有增加。在260℃等温处理,实验钢具有最好的综合力学性能,抗拉强度1600 MPa,伸长率13.8%,-20℃冲击功24 J。不同等温处理后组织均包含初生马氏体、新生马氏体和残余奥氏体。随等温温度升高,残余奥氏体含量先增加后降低,在260℃等温处理残余奥氏体含量最大,为9.3%。在300℃等温处理,组织中出现了尺寸较大的块状新生马氏体,导致韧性降低。

Effects of isothermal temperature on microstructure and mechanical properties of a kind of medium carbon low alloy ultra high strength steel after direct quenching and isothermal temperature treatment were investigated by means of SEM,XRD.The results show that with the increase of isothermal temperature,the tensile strength reduces while the yield strength decreases at first and then increases.The impact energy firstly increases and then decreases,and the elongation slightly increases with the increase of isothermal temperature.After direct quenching and isothermal treatment at 260 ℃,the tested steel can obtain the best comprehensive mechanical properties with tensile strength of 1600 MPa,elongation of 13.8%,and impact energy of 24 J.The microstructure of the tested steel is mainly composed of the initial martensite,fresh martensite and retained austenite.The retained austenite fraction of 9.3% is highest when temperature treatment at 260 ℃.The larger blocky fresh martensite has unfavorable effects on toughness,and the impact energy is the lowest when isothermal treatment at 300 ℃.