低碳钢IQ&P工艺下元素配分行为及对组织性能影响

Effect of Element Partitioning Behavior on Microstructure and Properties of Low-carbon Steel in IQ&P Process

采用双相区再加热-淬火-碳配分(IQ&P)工艺,研究了双相区不同等温时间下低碳钢中元素配分行为,并分析其对组织形貌、残余奥氏体及力学性能的影响。结果表明:在IQ&P工艺中,在750℃随等温时间的延长,Mn元素向逆转奥氏体内富集现象逐渐明显,等温时间超过300s后,C元素在两相之间的配分效果不随时间的延长而改变;在750℃等温处理过程中,原奥氏体晶界生成块状逆转奥氏体,马氏体板条界间生成针状逆转奥氏体;随等温时间的延长,钢的最终组织中针状铁素体体积分数不断减小,而块状及针状马氏体体积分数不断增大,同样残余奥氏体体积分数也不断增大;在C、Mn元素的综合作用下,钢的抗拉强度不断增大,断后伸长率先减小而后增大,等温1800s时,钢的强塑积达到最大值21GPa%。

Effects of element partitioning behavior on morphology, retained austenite and mechanical property of low-carbon steel were studied by the intercritical reheating-quenching and carbon partitioning （IQ＆P） heat treatment. The results show that the phenomenon of Mn enrichment in the reversed austenite becomes clear with 750℃ isothermal time prolonging in IQ＆P process, while the effect of C partitioning between the two phases does not change with time increasing when the time is more than 300 s; The block of reversed austenite is generated in the boundaries of the prior austenite grains and the needle of reversed austenite is generated in the boundaries of the martensite laths; With the intercritical reheating time prolonging, the volume fraction of the needle ferrite in the final structure of the steel is decreasing, while the volume fraction of the block and needle martensite is increasing, and the volume fraction of the retained austenite is also increasing. Under the combined effect of C, Mn elements, the tensile strength of steels is increased while the elongation is first reduced and then increased, and the multiply of strength and elongation is the maximum 21 GPa% when the time is 1800 s.