Product Code: ICAL09_708

Optical Properties of Laser-Induced Plume During High Power Laser Welding
Authors:
Shinpei Oiwa, Jwri, Osaka University; Osaka Japan
Yousuke Kawahito, Jwri, Osaka University; Osaka Japan
Seiji Katayama, Jwri, Osaka University; Osaka Japan
Presented at ICALEO 2009

During laser welding, laser-induced plume ejecting from a keyhole affects welding results greatly, and therefore this plume is generally removed with a shielding gas. In remote/scanning welding, however, a tall plume is generated in the case of a long focal length lens and no shielding gas, and the weld penetration is greatly reduced. This result is attributed to the Rayleigh scattering due to ultrafine particles and/or the variation in a beam mode and focal position caused by the interaction of an incident laser beam to the laser-induced plume with different refractive indexes. However, the details are hardly known. In this study, therefore, the laser-induced plume behavior and the variation in the fringe patterns obtained by Michelson interferometer were observed by high speed video camera. Fringe patterns were used to calculate the refractive index distribution. The experimental results confirmed that differential distributions of refractive index exerted a considerable effect on the incident laser beam and welding results, and that its focal point was spatially unstable and shifts downwards.