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采用4000W盘片式Yb:YAG同体激光器,利用激光深熔焊原理对1.2mm厚的超高强钢DP780进行激光对接焊研究。利用光学显微镜、扫描电镜、透射电镜等分析测试手段,研究了DP780激光焊接头的微观组织特点及激光焊参数对接头组织与力学性能的影响规律。结果表明,焊缝组织主要由板条马氏体及贝氏体构成,其大大提高了焊接接头熔合区的显微硬度。在焊接接头存在有软化区,其不会因速度增加而消失,但较高的焊接速度能减小软化区的宽度。焊接接头的抗拉强度要高于母材,熔合区显微硬度的升高是造成接头杯突值下降的主要原因。
Using 4000W disc Yb: YAG laser, laser deep penetration welding principle of 1.2mm thick ultra high strength steel DP780 laser butt welding research. The microstructure and laser welding parameters of DP780 laser welding head were studied by means of optical microscope, scanning electron microscope and transmission electron microscope. The influence of laser welding parameters on the microstructure and mechanical properties of the joint was studied. The results show that the weld microstructure mainly consists of lath martensite and bainite, which greatly improves the microhardness of the weld zone. There is a softening zone in the welded joint that will not disappear as the speed increases, but a higher welding speed reduces the width of the softened zone. Tensile strength of welded joint is higher than that of base metal. The increase of microhardness of fusion zone is the main reason of the drop of joint cup suddenness.