Product Code: ICAL08_705

Development of Ultra Deep Penetration Welding with 10 kW Fiber Laser
Authors:
Xudong Zhang, Materials Research Laboratory,Hitachi Ltd.; Hitachi-Shi, Ibaraki-Ken Japan
Eiji Ashida, Materials Research Laboratory, Hitachi Ltd.; Hitachi-Shi, Ibaraki-Ken Japan
Masami Mizutani, Osaka University; Osaka Japan
Seiji Katayama, Osaka University; Osaka Japan
Presented at ICALEO 2008

Wine-cup weld bead geometry with excessive wide bead surface is apt to form in high-power high-brightness laser welding in the range of low welding speeds (lower than 1 m/min), because the keyhole is unstable in the large molten pool, thus the metal plume/plasma ejects from the keyhole in all directions and pushes the melt to flow sideways at the molten pool surface. As a result, the decrease in welding speed induces considerable increase in bead width, but only a slight increase in penetration depth. The penetration will be increased greatly and the width of the bead surface reduced if the keyhole is stably opened and consequently the plume is suppressed. This paper presents a method for suppressing the plume/plasma and stabilizing the keyhole by using a gas jet nozzle, to get ultra deep penetration in high power fiber laser welding. The behavior of the molten pool and the plume/plasma was observed with two high-speed CMOS cameras, and the influence of the gas jet parameters on the weld bead geometry was investigated. The results showed that in laser welding of thick section stainless steel, the penetration depth was increased from 18.2 mm to 24.5mm in the conditions of the laser power of 10 kW and the welding speed of 0.3 m/min.