30 kW光纤激光焊接铝合金离焦量对匙孔行为的影响

Effect of defocusing amount on keyhole behavior in 30 kW fiber laser welding of aluminum alloy

针对30 kW光纤激光焊接铝合金焊缝成形差的问题,采用高速摄像拍摄焊接过程中的熔池及匙孔图像,对比研究了不同离焦量对匙孔行为的影响。结果表明,离焦量对匙孔及熔池行为的影响较大;正离焦时,匙孔开口面积的波动程度较为剧烈,匙孔后壁易形成向上涌起的液柱,并伴随有大量飞溅的产生,匙孔开口面积的大幅度突变和液柱的回落过程会对液态熔池的稳定流动产生较大干扰,使焊缝表面出现凹陷和咬边等缺陷;负离焦时,匙孔开口面积在波动幅度和突变持续时间上均较小,-20 mm离焦量时,匙孔突变的扩大-收缩持续时间仅为正离焦量的1/3,且液态金属上涌形成液柱的趋势也较小,焊接过程更稳定,焊缝表面成形的质量得到了明显改善,单道激光焊缝熔深可达29 mm。

Aiming at the problem of poor formation of weld in 30 kW fiber laser welding of aluminum alloy,the images of weld pool and keyhole in the welding process were taken by high-speed camera,and effect of different defocusing amount on keyhole behavior was studied comparatively.The results showed that defocusing amount had a great influence on keyhole and molten pool behavior.In the case of positive defocusing amount,the fluctuation degree of keyhole opening area was more violent,and the back wall of keyhole was easy to form upward flowing liquid column,accompanied by a large number of splashes.The large-scale mutation of keyhole opening area and the falling process of liquid column would greatly disturb the stable flow of liquid molten pool,resulting in defects such as depression and undercut on the weld surface.In the case of negative defocusing amount,the area of keyhole opening was relatively small in both fluctuation amplitude and duration of abrupt change.In the case of-20 mm defocusing amount,the duration of sudden expansion contraction of keyhole was only 1/3 of that of positive defocusing amount,the tendency of liquid column formed by liquid metal upwelling was also small,the welding process was more stable,and the quality of weld surface forming was significantly improved.The penetration of single laser weld reached 29 mm.