Influencing mechanism of high speed on the droplet transfer and process stability during high-power laser-arc hybrid welding

Laser-arc hybrid welding technology (LAHW), being a promising joining method, has paid close attention to the shipbuilding manufacturing with high quality. The behavior of droplet transfer exerts enormous influence on the weld appearance and dynamic process stability. However, there has been controversy whether high speed ( v > 3 m/min) promotes or hinders the droplet transfer under high laser power. In this study, the influencing mechanism of the high speed (3~5 m/min) on the droplet transfer behavior based on a new droplet force theory was systematically investigated. Firstly, the welding speed affects the energy density, and the welding speed is inversely proportional to the amount of metal vapor. Metal vapor reaction force would decrease with the increasing of welding speed. In addition, the deviation of droplet was determined by the competition between metal vapor and surrounding gas. The exposure time between metal vapor and surrounding gas would be reduced as welding speed increased, which decreased the impact of metal vapor reaction force. Similarly, the droplet transfer frequency is related to the droplet force analysis. The droplet transfer period was shortened to 3.2 ms as welding speed increased to 5 m/min, and the transfer frequency was 312 Hz. This study can provide guidance on the process mechanism of high-power LAHW with high-speed, which will enhance process stability and improve weld quality.