Abstract: The laser incident angle affects the transient behaviors of a molten pool and keyhole in the process of laser welding. However, it is difficult to investigate its impact rule only by using technical experimental methods. Three processes of laser welding with the laser incident angle of 30°, 0°, -30° are respectively simulated by the numerical simulation technology to study the effects of laser incident angle on transient behaviors of a molten pool and keyhole. At the same time, the simulated results are validated through the laser welding experiments. The cross-section geometry of simulated welds agrees well with the experimental results, which indicates that the simulated results can represent the laser welding process. The variations of temperature field, flow field in a molten pool, recoil force on the rear keyhole wall, the depth of keyhole and static pressure on the rear keyhole wall are analyzed at different laser incident angles. The results show that when the laser incident angle is positive, the flow is slow in a molten pool, when it is negative, the flow is faster. Also it can be found that the positive incident angle welding is helpful to suppress the formation of spatters, while the negative promotes the generation of spatters. When the laser incident angle is positive, the stability of a keyhole increases. When it is negative, the stability of a keyhole decreases, and the collapse of a keyhole increases which raises the probability of bubbles generation. Thus, it is shown that the laser welding quality can be improved with a suitable positive laser incident angle.

Key words: laser welding, laser incident angle, molten pool, keyhole