Narrow Groove Laser-Arc Hybrid Welding of Thick-Sectioned HSLA Steel Using Laser Beam Oscillation

In this study, a sine-oscillating laser was used to obtain narrow groove laser-arc hybrid welding (NGHW) of high-strength low-alloy (HSLA) steel. Then the effects of laser beam oscillation amplitude and space constraint on arc behavior, droplet transfer, weld geometry, and incomplete fusion of the weld beads were analyzed. Due to the minimum arc voltage principle and inherent arc self-regulation, when the laser did not oscillate, it was observed that the arc cathode spot was typically attached to one sidewall. As a result, the molten pool did not spread through the entire width of the gap, resulting in incomplete fusion. When the laser beam oscillated in a sinusoidal path, the energy density on both sides of the amplitude was higher than the centerline, and the aspect ratio of the weld decreased. The speed of the beam along the centerline was found to be much higher than the speed on both sides of the amplitude. The molten pool oscillated in the width direction under the action of the oscillating beam, forming a concave surface, which promoted melting of the sidewalls of the groove and suppressed incomplete fusion defects in the sidewalls. The technical feasibility of NGHW assisted by laser beam oscillation was verified using a 60-mm-thick weld, which was characterized by a smooth layer transition and the absence of visible defects.