临界区回火温度对Fe-4Mn-1.2Cr-0.3Cu-0.6Ni中锰钢微观组织和力学性能的影响

Effect of intercritical tempering temperature on microstructure and mechanical properties of Fe-4Mn-1.2Cr-0.3Cu-0.6Ni medium manganese steel

研究了临界区回火温度对Fe-4Mn-1.2Cr-0.3Cu-0.6Ni中锰钢组织与力学性能的影响。通过热轧后直接淬火+临界区回火的工艺制备试验钢。采用光学显微镜(OM)、电子探针显微分析仪(EPMA)的扫描功能、透射电镜(TEM)、拉伸试验及冲击试验等对轧后淬火态和回火态试验钢的显微组织及力学性能进行了表征。结果表明,试验钢热轧后淬火可获得较高位错密度的板条马氏体,经过临界区回火后获得在回火马氏体基体上分布残留奥氏体的复合组织。随着临界区回火温度的升高,试验钢的抗拉强度呈升高趋势,而屈服强度先下降后增加,伸长率的变化趋势与试验钢中的残留奥氏体含量相关,冲击性能随临界区回火温度的升高呈先升高后降低的趋势。630℃回火后试验钢的拉伸性能最佳,650℃回火后试验钢的冲击性能最佳,确定最佳临界区回火温度区间为630~650℃。

Effect of intercritical tempering temperature on microstructure and mechanical properties of Fe-4 Mn-1.2 Cr-0.3 Cu-0.6 Ni medium manganese steel was studied. The tested steel was prepared by direct quenching after hot rolling and intercritical tempering. The microstructure and mechanical properties of the quenched after rolling and tempered tested steels were characterized by means of optical microscope(OM), scanning function of electron probe microanalyzer(EPMA), transmission electron microscope(TEM), tensile test and impact test. The results show that the lath martensite with higher dislocation density can be obtained in the tested steel quenched after hot rolling, and the composite structure of retained austenite distributed on the tempered martensite matrix can be formed after intercritical tempering. With the increase of intercritical tempering temperature, the tensile strength of the tested steel increases, while the yield strength first decreases and then increases. The change trend of elongation is related to the content of retained austenite in the tested steel. The impact property first increases and then decreases with the increase of intercritical tempering temperature. The tensile properties of the tested steel tempered at 630 ℃ is the best, but the impact property of the tested steel tempered at 650 ℃ is the best, so that the optimum intercritical tempering temperature range is determined to be 630-650 ℃.