Abstract: The metal transfer behaviors in consumable double-electrode gas metal arc welding(GMAW) process is analyzed based on the state force balance theory. In main torch, the bypass arc enlarges the main arc root area to promote the main metal transfer; in bypass torch with direct current electrode negative, because the electromagnetic force does not work and only gravity promotes the metal transfer, the droplet is large and not easy to transfer. In order to improve the bypass metal transfer, a scheme is proposed which adds CO2 to shielding gas. By using this scheme, an oxide film will be formed at the bypass droplet and the bypass arc will burn on the bypass droplet. In this condition, the electromagnetic force will promote the bypass metal transfer. Then, the welding experiment is carried out to test the effectiveness of this scheme. The results show that, with 80%Ar and 20% CO2 as shielding gas, the size of bypass droplet is decreased and the frequency of bypass metal transfer is also increased obviously.

Key words: Gas metal arc welding(GMAW), Metal transfer, Welding arc