Numerical and experimental study on spatter in oscillating laser-arc hybrid welding of aluminum alloy

Spatter serves as a crucial metric for assessing welding stability, with excessive spatter posing significant risks to weld quality, performance, and equipment integrity while also impacting the environment adversely. In oscillating laser-arc hybrid welding (O-LAHW), the spatter exhibits a distinct pattern: an initial sharp decline followed by a gradual increase as oscillation speed rises. Existing research struggles to fully explain this trend due to challenges in developing a precise numerical spatter model. This paper introduces a novel heat flow labeling model and establishes an O-LAHW spatter validation model with 90 % accuracy based on it. Combined with hydrodynamics, this model explores the mechanisms behind spatter formation and suppression based on laser beam oscillation. Firstly, high-speed photography and numerical analysis reveal a third type of spattering in O-LAHW, distinct from spatter caused by keyhole collapse and droplet impact—spatter occurs when liquid metal is expelled from the melt pool due to laser beam oscillation. Secondly, hydrodynamic insights show that laser beam oscillation significantly reduces steam-induced driving force and metal vapor resistance to droplets. Consequently, as oscillation speed increases, the prevalence of the first two spatter types diminishes while the third type becomes dominant. Large-particle spatters decrease while small-particle spatters increase. Finally, by analyzing spatter statistics across various oscillating parameters, we observe a competitive mechanism among the three types of spatters. In non-oscillating welding, Type I spatter predominates; under low-frequency oscillation, Type II gains dominance; in high-frequency oscillation, Type III takes over. Optimal spatter reduction occurs at low-frequency oscillation, achieving a 27.1 % decrease compared to non-oscillating conditions.