Abstract
Full penetration weld bead by one pass butt joint welding of 12 mm thick SM490 plate were produced using the hybrid welding system combined with 4 kW power class fiber laser and pulsed MAG arc. The fusion zone was believed to be formed by one weld pool. A sound one pass full penetration weld bead without inside defects was obtained at the groove angle of 20 degrees and the gap width of 0.7 mm. A gap width of 1.5 mm was bridged by the hybrid welding process, but underfilling occurred at the root gap width over 1.0 mm in all groove angles. In order to improve the underfilling, higher feeding rate of a filler wire was applied by increasing the arc current. However, it was not a successful method because more molten metal and higher arc pressure accelerated the melt-through on the bottom beads. According to microstructure observation and hardness profile on the cross section, there was no brittle phase caused by the laser welding.
