超高强度硼钢38MnB5的热冲压工艺研究

Study on hot stamping process of 38MnB5 ultra high strength boron steel

利用扫描电镜(SEM)、光学显微镜、万能拉伸试验机对2.2 mm厚的38Mn B5钢在不同加热温度和不同保温时间工艺参数下,对微观组织、原始奥氏体晶粒粒径和力学性能进行研究,制定出最佳的热冲压工艺参数。研究结果表明:当保温时间一定时,随着加热温度的升高试样抗拉强度逐渐增强,在950℃时达到峰值,随着温度继续升高,抗拉强度降低;当加热温度一定时,随着保温时间的加长,原始奥氏体晶粒不断长大,试样抗拉强度随时间增加而增加,在10 min时达到峰值,保温时间继续加长,抗拉强度降低;38Mn B5钢在加热温度为950℃和保温时间为10 min的工艺参数下,得到最佳力学性能。抗拉强度达到2 061 MPa,屈服强度达到1 421 MPa,断后伸长率为7%。

Microstructure and prior austenite grain size of 38MnB5 hot stamping steel were observed and investigated via scanning electron microscopy(SEM)and optical microscope.Mechanical properties were obtained via universal tensile testing machine.Hot stamping steels with different heating temperature and soaking time were performed and the optimal process was confirmed.The results show that the tensile strength increases at first and then decreases with the increase of temperature,peaking at 950℃.The prior austenite grain grows with the increase of soaking time while tensile strength increases at first and then decreases,peaking at 10 min.The 38MnB5 hot stamping steel with the most optimal mechanical properties is obtained at the heating temperature of 950℃and the soaking time of 10 min.The tensile strength is 2 061 MPa,the yield strength is 1 421 MPa and the elongation is 7%.