Simulation analysis of droplet action on keyhole during laser-MIG composite welding of aluminum alloy

In this paper, a coupled thermal flow model for 5A06 aluminum alloy laser-MIG hybrid welding is developed, which takes account of the driving forces such as recoil pressure, surface tension and droplet transfer behavior. The flow in the molten pool and the stability of the keyhole have an important impact on the welding performance, therefore, the influence of droplet and keyhole on the stability of molten pool is discussed systematically through numerical simulation with different droplet location. It is found that the impact of the melt drop on the keyhole is greater, the average velocity and wave frequency of the keyhole wall increase, and the keyhole bridge is more likely to be closed due to the periodic droplet transition, when the melting drop is close to the laser center. In addition, the location of melting drop will also affect the ratio of depth to width of the keyhole and thus affect the Fresnel absorption of laser energy.