Numerical research on melt pool dynamics of oscillating laser-arc hybrid welding

The melt pool dynamics of oscillating laser-arc hybrid welding (O-LAHW) remains unclear, slowing its process development and application. In this study, a three-dimensional transient numerical model considered the heat transfer and fluid flow characteristics is established to clarify the melt pool dynamics in O-LAHW, and the physical processes such as melt pool morphology, temperature field, and melt flow are investigated and analyzed. The results show that beam oscillation creates a small depth-to-width ratio and flat weld, the dynamic keyhole alleviates the heat accumulation and suppresses spatter and porosity. The temperature field is significantly improved by the energy coupling between the oscillating beam and arc and the dynamic keyhole-induced convection/vortex. The vortex is the common flow pattern in melt pool with beam oscillation and depends on the competition of driving forces. The mathematical model of oscillating shear force is proposed to quantify the beam stirring effect. At 150 Hz, the oscillating shear force drives a powerful vortex of 0.7 m/s flow velocity dominating the flow field and stabilizing the melt pool. The results clarify the physics aspects of melt pool dynamics and contribute to the development of O-LAHWs.