辅助增强匙孔激光焊接的等离子体特征

Characteristics of Plasma in Gas-Jet-Assisted Keyhole Laser Welding of 1Cr18Ni9Ti

等离子体的有效抑制是提高激光焊接能量吸收率、熔池小孔稳定性的重要途径，气流辅助激光焊接是通过控制等离子体行为增加激光焊接熔深的有效途径之一。采用1．5kW板条型CO2连续激光器，开展了不同气流参数下的激光焊接试验，同时采用高速摄像机拍摄等离子行为。通过图像处理方法提取了不同条件下的等离子云质心点坐标、质心方向、等离子云面积等参数。结果表明，激光焊接过程中等离子体的产生和喷发存在一定的周期性，等离子云的波动周期大致在2～10ms之间。无论是采用喷嘴在前或在后的布置，随着辅助气流流量的增加，等离子云的面积都有逐渐减少的趋势，并且减小的速度很快，当流量增加到6L／min时等离子体云几乎完全抑制。喷嘴在后布置时的辅助气流敏感性更强，在同样的气流流量变化时，其等离子云抑制更为显著。

Plasma control is valuable to improve the absorption ratio of laser energy and to stabilize the keyhole and molten pool. Gas-jet-assisted keyhole laser welding is one of the effective ways to increased penetration of laser welding by this way. A series of experiments of gas-jet-assisted keyhole laser welding were carried out with 1.5 kW SLAB continuous C02 laser. Furthermore, plasmas images were captured by a high speed camera during the above experiments. The coordinates, directions of the eentroid point and areas of the plasma cloud were extracted by using image processing algorithm under different conditions. The results show that the plasma induced in the laser welding fluctuates at a certain periodicity of 2~10 ms. Whether the nozzle of assisted gas jet is leading or rearing layout, size of the plasma cloud has a decreasing trend with the increase of flow rate of gas jet, and plasma cloud is almost completely suppressed when the flow rate increases to 6 L/min. The sensitivity of flow rate of the rearing assisted gas jet is higher than the leading one, and more plasma with the rearing assisted gas jet is suppressed in the same increase in flow rate.