高强镀锌钢激光填粉焊接的粉末输送研究

Study on Powder Delivery in Laser Welding of High Strength Galvanized Steel with Powder Filling

激光填粉焊接是一种高柔性化焊接加工技术,能有效降低激光焊接装配精度。使用自行开发的侧向送粉装置,基于粉末分布密度与图像灰度的相关性,测量分析粉束截面的粉末分布密度和粉末输送的有效性,并开展高强镀锌钢光纤激光填粉焊接的焊接工艺性及接头性能的研究。结果表明,粉末落点是决定粉末利用率的关键因素。以45°侧向送粉时,有效输送率最高的粉末落点为–1.75 mm。粉末落点过于靠近或远离激光束时均不利于金属粉末有效熔入熔池。粉末落点为–4 mm时,粉末利用率最高。焊缝中心铜的质量分数随着送粉速度的降低而线性减小。填充粉末能明显提高焊缝表面质量,细化热影响区晶粒,提高焊缝组织性能,同时提高了激光焊接间隙裕度,降低工件对激光焊接装配精度的要求。

Laser welding with powder filling is a highly flexible welding technology due to its effective reduction of the assembly accuracy of workpiece. Based on the correlation between the density of powder distribution and the image gray, the distribution density on the cross section of the powder beam is measured, and the effectiveness of the powder delivery with a self-developed lateral device for powder feeding is analyzed. Furthermore, the welding technological properties and the joint performance in fiber laser welding of high strength galvanized steel with powder filling are studied. The results show that： The powder position is the key factor of the rate of the powder utilization. When filling powder laterally in angle of 45~, the most effective delivery rate can be obtained with the powder position of-1.75 mm. The power would to be fed into the welding pool ineffectively when powder position is too close to or far away from the laser beam. The highest rate of the powder utilization can be realized with the powder position of --4 mm. The copper content on the weld center section decreases linearly with the reduction of the powder feeding speed. Powder filling can significantly improve the performance of the weld surface and refine the grains in the heat-affected zone, as well as the improvement of the weld properties. Laser welding with powder injection is able to improve the weld surface quality, create finer microstructure in the heat affected zone, improve the strength of the weld, as well as increase the gap tolerance and reduce the assemble accuracy of the workpiece.