Effects of Laser-Induced Plume in High-Power Fiber Laser Welding with Long-Focal-Distance Focusing Optics
Effects of Laser-Induced Plume in High-Power Fiber Laser Welding with Long-Focal-Distance Focusing Optics
复制标题
长焦距聚焦光学器件高功率光纤激光焊接中激光羽流的影响
DOI：
10.2207/qjjws.29.18
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
S. Katayama
中科院分区：
文献类型：
--
作者：
Y. Kawahito;S. Oiwa;M. Mizutani;S. Katayama
高光束质量的高功率光纤激光器已经开发出来，高功率光纤激光器远程焊接有望成为汽车行业高速焊接的新工艺之一。特别是长焦距聚焦光学器件有利于大面积的焊接。然而，这种焊接过程中激光诱导羽流的特征和影响尚不完全清楚。因此，本研究旨在研究去除或不去除激光诱导羽流的焊缝熔深特性，以阐明焊接现象，并开发使用焦距为 1,250 mm 的聚焦光学器件在 4 kW 高功率光纤激光焊接 1.5 mm 厚的镀锌钢板时稳定的焊接工艺。在没有去除羽流的情况下在焦点位置获得的焊缝非常不稳定，以至于在激光焊接过程中将完全熔透变为部分熔透。为了从根本上理解远程焊接现象，通过迈克尔逊干涉方法对激光照射区域上方的折射率分布进行可视化。通过高速摄像机对条纹图案的观察结果表明，入射激光束由于羽流高温金属蒸气产生的小折射率值的宽形成范围和复杂行为而被散焦和折射，导致形成不稳定的熔深焊缝。还证实，在使用长焦距聚焦光学器件的高功率光纤激光远程焊接中，使用风扇去除激光诱导羽流和相应的广泛的低折射率值场对于稳定生产全熔透焊缝至关重要。
High power fiber lasers of high beam quality have been developed, and remote welding with a high-power fiber laser has been expected to be one of new high-speed welding procedures in automobile industries. In particular a long-focal-distance focusing optics is beneficial to the welding of a wide area. However, features and effects of a laser-induced plume in such welding process are not fully understood. Therefore, the study was undertaken to investigate weld penetration characteristics with or without removal of a laser-induced plume, to clarify welding phenomena and to develop a stable welding procedure in 4 kW high-power fiber laser welding of a 1.5 mm-thick zinc-coated steel sheet using the focusing optics with a lens of 1,250 mm in focal length. The welds obtained at the focal position without removal of the plume were so unstable that the full penetrations were changed to partial penetrations during laser welding. To fundamentally understand the remote welding phenomena, refractive-index distribution above the laser-irradiated area was visualized by the Michelson interference method. The observation results of fringe patters through a high-speed video camera demonstrated that the incident laser beam was defocused and refracted by a wide formation range and complicated behavior of small refractive-index values derived from the high-temperature metal vapor of the plume, leading to the formation of an unstable penetration weld. It was also confirmed that the removal of the laser-induced plume and the corresponding widespread field of low refractive-index values by using a fan was essential to the stable production of fully-penetrated welds in the high-power fiber laser remote welding with the long-focal-distance focusing optics.