THE INSTABLE DYNAMIC BEHAVIORS OF KEYHOLE AND MOLTEN POOL IN HIGH SPEED LASER WELDING

摘要

The dynamic behaviors of the keyhole and molten pool in the high speed laser welding are highly related to the weld formation quality and welded joints performance. A 3D numerical simulation method is proposed in this paper to explore the instable dynamic behaviors of the keyhole and molten pool in the high speed laser welding. The keyhole formation process and its effect on the molten pool are analyzed in details from the keyhole profile and instable dynamics behaviors based on the numerical calculation results. The analysis results show that the keyhole dynamic behaviors have great influence on the molten pool formation process and then the formed weld surface. The keyhole is moving forwards in the high speed and elongated and the rear wall of the keyhole is inclined. The interface between the keyhole and molten pool is kept in moving forwards and backwards induced by the instable dynamic behaviors. The molten metal is flowing along the inclined keyhole wall and collision with the molten pool surface greatly, which results in the oscillation and shrinking of the molten pool and the concave and convex surface formation in the weld. It is clearly seen that reducing the instable dynamic behaviors of the keyhole and molten pool is effective for improving formed weld quality in the high speed laser welding.