气流辅助增强匙孔激光焊熔深增加机理

Mechanism of penetration depth increase in gas-jet-assisted keyhole laser welding

采用直径为0.8 mm的气流喷嘴直吹匙孔,开展了不同吹气方向、气流入射点位置及流量下的激光焊试验,为获得增强的匙孔效应和增加的熔深.通过等值线图分析获得了优化的气流参数,最大熔深较传统激光焊增加了约38%.合适入射点位置和流量的增强匙孔气流,不仅压制了等离子体,还将匙孔口部的液态金属向下压,使得匙孔口部明显扩大、熔深增加、焊缝成形良好,匙孔内等离子体的流向发生了改变,因而熔池内液态金属的流向也发生了变化;入射点位置偏后时,其作用区域为匙孔后方熔池,将液态金属向熔池后方推,会导致驼峰焊道的产生.

0. 8 mm diameter of assisted gas jet nozzle was employed to straightly blow keyhole with the incidence angle of45° to deepen keyhole and weld penetration. A series of experiments of CO2 laser welding of stainless steel were carried out and the images of molten pool and keyhole were captured by high speed camera. The optimized range of incident point,nozzle positions and flow rates of assisted gas jet were obtained by using the contour map,and the maximum penetration depth increased by about 38% compared with the conventional laser welding.The experimental results shows that,when the gas jet is projected the keyhole center,the introduction of assisted gas jet with the suitable flow rate is not only to suppress the plasma,significantly expand the keyhole orifice,but also to change the flow direction of the plasma inside keyhole which leads to the change of the internal flow of the molten pool. When the gas jet is projected behind the keyhole with the incident area is away from keyhole,it extrudes the liquid metal to the keyhole orifice and the tail part of molten pool which would result in hump weld.