高速激光焊的多种典型缺陷形成都与熔池流动有关，深入了解熔池流动行为有助于理解高速焊缺陷的形成机理。采用光纤激光进行高速焊接试验，分别研究在功率和热输入一定的条件下焊接速度对熔池流动行为的影响。采用高速摄像实时观察熔池表面的流动行为，通过Ti示踪元素考察熔池内部的流动行为。结果表明，焊接速度提高，熔池表面液态金属向熔池尾部流动的距离增加，熔池内部的中心部位液态金属向熔池底部和尾部流动的距离增加，熔池内部边缘处液态金属流动受焊接速度的影响较小。提高焊接速度，金属蒸气喷出方向与熔池表面的夹角减小，金属蒸气对小孔后沿冲击力的水平分量增大，导致熔池表面液态金属向熔池尾部流动的驱动力增大，流动距离因而增加。

Typical welding defects of the high speed laser welding process have a close relationship with the melt flow of molten pool. The investigation of melt flow behavior can help to further understand the formation mechanism of defects in the high speed welding process. In this study, fiber laser is used to weld austenitic stainless steel sheet. The effect of welding speed on melt flow behavior has been investigated. The surface flow behavior is studied by high speed visual detection system. In addition, the inner flow is studied through Ti tracer method. The results show that with the welding speed increasing, the flow distance of surface flow from keyhole to rear goes up, the molten metal in the middle of molten pool moves to the bottom and rear of pool with a longer distance. The effect of the welding speed on melt flow near the edge of the molten pool is small. It can be accounted that, with the welding speed increasing, the angle between vapour plume and pool surface decreases, the horizontal component of the vapour force will improve, which causes the backward driving force to increase and the flow distance of the surface flow to increase.