Product Code: ICAL08_707

Laser Absorption in High-power Fiber Laser Welding of Stainless Steal and Aluminum Alloy
Authors:
Naoyuki Matsumoto, Osaka University; Ibaraki Japan
Masami Mizutani, Osaka University; Ibaraki Japan
Yousuke Kawahito, Osaka University; Ibaraki Japan
Seiji Katayama, Osaka University; Ibaraki Japan
Presented at ICALEO 2008

High power and high brightness fiber lasers have been developed, and it is revealed that a deeper and narrower weld bead can be produced with the increase in the power density. Thus high absorptivity of laser energy is expected, but there are few systematic experimental researches of laser absorption in conjunction with a beam diameter and a keyhole diameter. Therefore, this study was undertaken by utilizing the calorimeter method and the observation technique of welding phenomena to obtain a fundamental knowledge of fiber laser absorption for stainless steal and aluminum alloy. The laser absorptivity of stainless steel was measured at various power densities depending upon the different defocused distances. Consequently, it was about 85 % within -7-+3 mm defocused distance. It increased with the increase in power density, and was about 85 % constant at more than 20 kW/mm2. The laser absorptivity of various aluminum alloys was lower than that of stainless steel at low power densities, but was about 85 % during deep penetration welding, which was the same as that of stainless steel. Moreover, a keyhole in the molten pool illuminated with a diode laser was observed with a high-speed video camera at the framing rate of 10,000-F/s. When the keyhole inlets were compared with the respective laser power density profiles, it was confirmed that the high laser absorptivty was attributed to the fact that the most part of laser energy was irradiated into the keyhole.