Influence of wire feeding speed on the melting behavior and formation of narrow-gap joint by laser welding with filler wire

The influence of wire feeding speed during laser welding with a filling wire was investigated by high-speed imaging and mechanical analysis of the droplet. A force relationship was found to analyze the droplet transition behavior at the end of the welding wire in the narrow-gap groove. Welding defects, mainly including nonfusion and porosity, were studied to reveal the formation mechanism and propose affective solutions. In this paper, it was found that the droplet transition was determined by the position of the melting end of the wire in the narrow-gap groove under the same parameters. The sidewall transition, the liquid bridge transition, and the spreading transition were found at different wire feeding speeds. As the wire feeding speed increases from 3 to 6 m/min, the weld depth increased 40%, the maximum weld width decreased 16%, and the minimum weld width increased 8%. More nonfusion and porosity defects and poor weld formation would appear at excessive wire feeding speed.