Abstract: The dual bypass metal inert gas (DB-MIG) arc welding method is presented and an experimental system is established. In this method, a conventional MIG welding arc is used as main arc and two symmetrical TIG welding arcs with controllable current are introduced as bypass arc. A coupled arc is formed by main and bypass arcs to carry out welding. Due to the shunt effect of bypass arc, base metal input current can be decreased effectively while wire melting current keeps high, and bypass arc force has great influence on metal transfer. A special narrow-band-filter system is built to realize high speed video of metal transfer behaviors without laser backlight, and high speed photographic images under different bypass current parameter conditions are obtained. Analysis results show that metal transfer mode changes with the change of current parameters of bypass arc. Then the changes in the forces acting on the droplet and the effects of these changes on the metal transfer behaviors are analyzed and the experimental phenomena are explained. Analysis shows that the bypass arcs and currents lower the critical current needed to achieve the desired spray transfer

Key words: Aluminum alloy, Dual bypass arcs, Metal transfer, MIG welding