车用双相钢激光焊接接头组织性能研究

为提高汽车车身用双相(DP)钢焊接构件在动态载荷下应用的可靠性,利用脉冲Nd:YAG激光器,对DP600进行激光对接焊,利用光学显微镜、扫描电子显微镜、显微硬度计、材料拉伸试验机等分析测试手段,研究了焊接接头的显微组织和高应变速率下的拉伸性能。结果表明,在合适的脉冲激光焊接参数下,DP600钢板可获得成形均匀的激光深熔焊缝。焊接接头的焊缝区(WZ)主要为马氏体组织,硬度高于母材;热影响区(HAZ)较窄但存在马氏体回火软化现象。焊接接头力学性能对应变速率较为敏感,随应变速率的增加,屈服强度和抗拉强度增加,而塑性均小于母材。不同应变速率下DP600对接焊拉伸断口均为韧窝形貌,呈典型的韧性断裂特征。

Study on Microstructure and Properties of Laser Welding Dual Phase Steel Joints for an Auto-Body

It is imperative to increase the service reliability of the laser welding dual phase (DP) steel joints for an auto-body which are subjected to dynamic loading during their manufacturing processes, as well as in an accident. Laser butt welding of DP600 is performed by using a pulsed NdYAG laser. Microstructures of the welding joints are analyzed. Microhardness and mechanical properties at various strain rates of the welding joints are tested. The results show that welds with good appearance can be obtained under the proper welding conditions. The microstructure of weld zone (WZ) is mainly martensite, and the microhardness is higher than that of base metal. And the heat affected zone (HAZ) is narrow, and there exists HAZ softening that occurs in welding because of the tempering of the martensite phase. The mechanical property of the DP600 welding joint is sensitive to the strain rates. After welding, the yield and tensile strength of DP600 increase as the strain rate increases, while the fracture elongations are all lower than that of the base metal. All tensile fracture of DP600 welding joints are typical ductile fracture characterized by dimples at various strain rates ranging from 10-3 to 103 s-1.