侧吹气流方向对大功率CO_2激光焊缝成形的影响

Effect of Side Assist Gas Orientation on High-Power CO_2 Laser Welding Formation

激光深熔焊过程中会在熔池上方产生等离子体云,若该等离子体云过密,将降低激光入射到工件表面能量密度。在工业应用中,常采用侧吹辅助气体来减弱等离子体云的影响。本文通过试验,研究了在不同气体流量下。侧吹气体方向不同对焊接过程稳定性和焊缝成形的影响。结果发现:使用大功率CO_2激光焊接AH32时,侧吹气体方向对焊缝成形有着明显的影响。从熔池和等离子体两个方面,解释了侧吹气体方向的影响机制。

CO2 laser welding is increasingly employed for high speed welds or welds on thick material. During the process, plasma may form near the fusion area due to ionization of metal vapor and surrounding gases. The plasma may dramatically reduce the efficiency and power of the laser beam in the weld zone, which is detrimental to achieving good penetration. Inert assist gases are utilized to minimize the effect of arc plasma formation and to blow away vaporized elements resulting from the welding process. Shipbuilding steel AH32 was welded using a high-power CO2 laser with forehand and backhand assist gas. The effects of the gas flow rate and direction on the stability of the welding process and the quality of the bead formation were examined. The orientation of assist gas influences greatly the welding process and performance. The increase of the flow rate leads to a deeper penetration and lower face reinforcement. In addition, forehand blowing gives a more stable welding process and deeper penetration compared to backhand blowing. Explanation was given using fluid dynamics principle.