Lap welding characteristics of thin sheet metals with combined laser beams of different wavelength

Abstract

It is well known that arc welding of thin metallic sheets in difficult due to their easier distortion and deformation. On the other hand, in laser welding, such distortion and deformation is greatly reduced due to a smaller spot size and smaller heat input than in arc welding. Even in laser welding, thinner metallic sheets become more difficult to weld due to the loss of materials and the difficulty in supporting a shallow molten pool against evaporation and recoil pressure, leading to the formation of cut or drilled welds. In this study, therefore, lap welding characteristics of thin metallic sheets were investigated by utilizing combined beams or respective single beam of normal pulsed YAG laser and Q-switched SHG YAG laser. It was consequently found that the formation conditions for good lap welds in thin stainless steel sheets were broadened by using combined laser beams. Especially, lap welding of pure copper sheets was very difficult with single pulsed YAG laser; however, it was confirmed to be possible to weld them with combined laser beams of two different wavelengths in the air environment.