Product Code: ICAL07_1601

High-Power Fiber Laser Welding of Thick Steel at Low Welding Speed
Authors:
Xudong Zhang, Hitachi Ltd.; Hitachi-Shi, Ibaraki-Ken Japan
Eiji Ashida, Hitachi Ltd.; Hitachi-Shi, Ibaraki-Ken Japan
Masami Mizutani, Osaka University; Osaka Japan
Seiji Katayama, Osaka University; Osaka Japan
Xiangjun Luo, Hitachi-GE Nuclear Energy, Ltd.; Hitachi-Shi, Ibaraki-Ken Japan
Yusuke Anma, Hitachi-Ge Nuclear Energy, Ltd.; Hitachi-Shi, Ibaraki-Ken Japan
Presented at ICALEO 2007

For butt-joint welding of thick section structure, low welding speed is preferred in order to get deeper penetration depth, and improve the gap tolerance by avoiding too narrow bead shape that is apt to be formed with high-power fiber laser at high welding speed. This paper investigates the weld bead formation in welding of thick section stainless steel at 0.2m/min-2m/min welding speeds with a 10kW fiber laser. The influence of shielding conditions, beam spot size and defocusing distance on weld bead shape at low welding speeds is studied. The result shows that meandering bead occurred at laser power of 10kW and welding speed of 0.3m/min is due to the severe oxidization of the molten pool. This bead meandering can be prevented by adjusting shielding conditions. Beam spot size has significant influence on the penetration depth, and the penetration depth at 0.1mm beam spot size is smaller than that of 0.2mm beam spot size. The defocusing distance where the maximal penetration could be obtained under 10kW laser power and 0.3m/min is about -7mm. In the final, the instability of penetration depth induced by thermal lens effect is also discussed.