Behavior of Solid Wire's Copper Coating in Molten Droplet Formation and Transfer

—Surface Tension of Molten Droplets in MAG welding—

Abstract

High speed video image analysis, optical measurement, and sound pressure analysis were conducted to reveal the difference between Cu-coated solid wire's and non-Cu-coated solid wire's molten droplet formation and transfer. It was obvious that the molten droplet size of non-Cu-coated solid wire was smaller than that of Cu-coated solid wire in any welding conditions except for very slow droplet formation. As Cu coating diffusion time was similar to molten droplet formation and transfer time, Cu coating on solid wire surface influenced the formation and the transfer of molten droplet. Cu coating prevented oxidization on solid state wire surface, and reduced the amount of oxygen on the molten droplet surface. Non-Cu-coated solid wire was the ideal material for the formation of small molten droplets of the short-circuit and the spray transfer.