Product Code: ICAL09_1403

Numerical Calculation of Laser Beam Path Influenced by High Temperature Gas Above Specimen during Laser Welding
Authors:
Masami Mizutani, Joining and Welding Research Institute, Osaka University; Ibaraki, Osaka Japan
Seiji Katayama, Joining and Welding Research Institute, Osaka University; Ibaraki, Osaka Japan
Presented at ICALEO 2009

It has been generally accepted that the laser beams of about 1 to 1.1 mm in wavelength, such as fiber, disk and YAG lasers have smaller interaction to the media such as plume and plasma between the optics system and the specimen than CO2 laser beam of 10.6 mm. However, we have recently found that weld bead formation is greatly affected by the state of the gas flow, the atmosphere, the ultrafine particles or the plasma plume above the specimen during fiber laser remote welding. The result showed that a laser beam tended to be deflected or refracted and focused on the far position without the positive elimination of the media above the specimen. In this paper, in order to understand why a laser beam is deflected, a numerical calculation about the laser trajectory in assumptive refractive index media by a temperature gradient was carried out. The calculation result suggested that the steep refractive index gradient above the specimen during welding should degrade the beam quality and shift the focal point far beyond the original position.