高强汽车钢温冲压成形工艺探讨

Study on warm stamping process of high strength automobile steel

热冲压成形汽车零部件的室温组织为全马氏体组织,虽然强度高,但延展性差。为此,提出了一种采用热轧后直接淬火获得马氏体组织,随后在冲压工序进行回火以提高冲压件延展性的温冲压成形工艺。采用热轧实验机和MMS-200热力模拟实验机模拟温冲压成形过程,并对实验钢力学性能和组织结构进行了分析。结果表明:随温冲压成形温度的升高及保温时间的延长,实验钢成形后抗拉强度和维氏硬度值不断下降,伸长率呈先上升后下降再上升的趋势。随成形温度的增加,实验钢组织由马氏体不断转变为回火马氏体、回火屈氏体和回火索氏体。在350℃保温120~180 s,实验钢成形后力学性能最佳,抗拉强度超过1500 MPa,伸长率大于8%,硬度值在425HV~440HV之间。冲压成形温度越高,对冲压设备所需求的力能参数越低。

The room temperature microstructure of automobile parts formed by hot stamping is full martensite structure.Although the strength is high,the ductility is poor.A warm stamping process was proposed,by which martensite structure is obtained by direct quenching after hot rolling and then tempering in stamping process to improve the ductility of stamping parts.The hot-rolling mill and MMS-200 thermal simulation machine were used to simulate the warm stamping process,and the mechanical properties and microstructure of experimental steel were analyzed.The results show that with the increase of warm stamping temperature and holding time,the tensile strength and Vickers hardness of the experimental steel decrease continuously,and the elongation increases first,then decreases and then increases.With the increase of forming temperature,the microstructure of experimental steel transforms from martensite to tempered martensite,tempered troostite and tempered sorbite.The best mechanical properties of experimental steel are obtained by holding at 350℃for 120-180 s.Its tensile strength is more than 1500 MPa,the elongation is more than 8%,and the hardness value is between 425HV-440HV.The higher the stamping forming temperature,the lower the force and energy parameters required for stamping equipment.