Brief Paper: Dynamic Keyhole Behavior and Fluid Flow in Multi-Laser Welding Process

Laser keyhole welding with multiple lasers in proximity has been an emerging technology in industrial applications. Compared with the commonly used single-laser system, the application of multi-laser welding provides different heat distributions to enable additional processing parameter manipulations, which can be particularly useful for certain applications. While experimental studies have revealed the keyhole geometries and molten pool dimensions in the multi-laser welding process, the dynamic behavior of multiple coexisting keyholes and the resultant fluid flow within the molten pool have not been well understood. In this work, a multi-physics numerical model is used to predict the transient and nonuniform distributions of laser absorption, temperature, and flow velocity in the tri-laser welding process. Two power settings that lead to different keyhole geometries are investigated. A detailed discussion is given to elucidate the effects of laser drilling within the high-temperature molten pool and its impact on enhanced overall laser absorption of the molten pool. A comparative analysis between single-laser and tri-laser keyhole welding is given to evaluate the significance of different driving forces acting on the molten pool to the keyhole dynamics.