一步淬火分配钢的工艺设计与微观组织演变

设计并研究了低碳硅锰系淬火分配(Q&P)钢的热处理工艺.利用SEM，TEM和XRD观察并分析了实验钢的微观结构和相组成.理论计算结果显示:Fe-021C二元合金的最佳淬火温度为290℃，最大残余奥氏体含量(摩尔分数)为179%.工艺模拟结果表明:实验钢残余奥氏体体积分数为67%~172%，残余奥氏体平均碳质量分数为102%~148%.残余奥氏体与相邻马氏体板条间晶体学位向符合K-S关系或N-W关系.实验所涉工艺中均存在新鲜马氏体的生成.随着配分时间的延长，残余奥氏体含量先增加后减少，残余奥氏体平均碳含量不断增加，最佳配分时间为50s.配分后期马氏体板条中出现的碳化物导致了残余奥氏体的减少.

Process Design and Microstructure Evolution of One Step Quenched and Partitioned Steel

The heat treatment processes of a low carbon Si Mn quenched and partitioned (Q&P) steel were designed and investigated. The microstructures and phase components were characterized and analyzed using SEM， TEM and XRD. Theoretical calculation results showed that the optimum quenching temperature for a Fe 021C binary alloy is 290℃ and the maximum amount of retained austenite is 179% (mole basis)， respectively. Process simulation results indicate that the volume fraction and the carbon concentration of the retained austenite in the tested steel are 67%~172% and 102%~148%， respectively. The orientation relationship between the retained austenite and adjacent martensite laths is identified as K S relationship or N W relationship. Fresh martensite forms in all the involved experimental processes. The amount of the retained austenite increases first and decreases after 50s and the carbon concentration of retained austenite rises monotonously with the increase of partitioning time. The optimum partitioning time is 50s. The carbides appear in the martensite laths during the later stage of the partitioning process and result in the decrease of the retained austenite.