Investigation on droplet transfer behavior during fiber laser-flux cored arc hybrid welding

Abstract

This paper comparatively investigated the droplet transfer behavior between the flux-cored arc welding (FCAW) and laser-flux cored arc (FCA) hybrid welding for Q235 steel. The High-speed imaging technique assisted with electrical signal analysis was utilized to capture the arc morphology and droplet transfer behavior during FCAW and laser-FCA hybrid welding under different arc current conditions. A parameter of the coefficient of current variation was proposed to evaluate the welding stability. Short-circuiting transfer, globular transfer, and projected transfer were detected as three separate droplet transfer modes during FCAW and laser-FCA hybrid welding. The molten flux was either transferred directly to the molten pool or transferred converging with the molten sheath metal to the pool along the “flux pole” which appears owing to the lagging melt phenomenon. The magnitude and direction of the electromagnetic force and the plasma drag force acting on the droplet played a key part in deciding the droplet transferbehavior. Due to the altered arc force in the short-circuiting mode, the laser facilitated droplet transfer, and hybrid welding maintained a more stable welding process. The laser hampered droplet transfer in both the globular and projected modes, and there was little difference in process stability between hybrid welding and FCAW. In addition, a substantial amount of acicular ferrite was discovered in the laser-FCA weld joint.