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 OLAHW, 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.