经改进型和普通淬火-配分工艺处理的高强钢的显微组织和力学性能

Microstructure and Mechanical Properties of High-Strength Steel Treated by Modified and Common Quenching-and-Partitioning Processes

对1 mm厚含0.20%C、2.0%Mn和1.75%Si(质量分数)的钢板进行了普通和改进型淬火-配分(Q&P)工艺处理。检测了钢板的显微组织、力学性能,并对拉伸断口进行了分析。结果表明:经改进型Q&P工艺处理的钢的显微组织由铁素体、贝氏体、二次马氏体和残留奥氏体组成,残留奥氏体体积分数为13.6%,而经普通Q&P工艺处理的钢则为铁素体+回火马氏体+二次马氏体+残留奥氏体,前者的残留奥氏体体积分数为13.6%,后者为9.2%;经普通Q&P工艺处理的钢的屈服强度、抗拉强度分别为680和1070 MPa,断后伸长率为20%,而经改进型Q&P工艺处理的钢的屈服强度和抗拉强度分别为600和1015 MPa,断后伸长率为26%;经改进型Q&P工艺处理的钢为韧性断裂,而经普通Q&P工艺处理的钢为韧-脆性混合断裂。

1-mm-thick steel plates containing 0.20%C,2.0%Mn and 1.75%Si by mass were quenched-and-partitioned by modified and common processes.The steel plates were subjected to microstructure survey,mechanical property measurement and tensile fracture testing.The results showed that(a)the microstructures consisted of ferrite,bainite,secondary martensite and retained austenite in the steel treated by the modified Q&P process,and of ferrite,tempered martensite,secondary martensite and retained austenite in the steel treated by the common Q&P process,and the amount of retained austenite was 13.6%by volume(the same below)in the former and 9.2%in the latter;(b)the steel exhibited yield strength of 680 MPa,tensile strength of 1070 MPa and elongation of 20%after being treated by the common Q&P process,and yield strength of 600 MPa,tensile strength of 1015 MPa and elongation of 26%after being treated by the modified Q&P process;and(c)the steel treated by the modified Q&P process displayed ductile fracture,whereas the steel treated by the common Q&P process displayed ductile-brittle mixed fracture.