Abstract: With conventional pure argon gas shielded, the bypass droplet volume is big and the metal transfer process is unstable in consumable DE- GMAW process as the bypass arc is selected DC positive connection. A method which adds CO₂ to shielding gas is proposed to change stress form of the bypass droplet surface so that metal transfer behaviors can be controlled. Based on those, a dynamic mathematical model which can describe the bypass metal transfer process is established to simulate and analyze the changes of bypass droplet diameter and metal transfer process under different stress form. Both of simulation and experimental results show thatwith the pure argon gas shielded, the range of bypass droplet diameter under different current is 2.6-3.3 mm, and the metal transfer process is difficult. The range of bypass droplet diameter is decreased to 0.6-1.1 mm and the metal transfer frequency is increased obviously with the 80%Ar+20%CO₂ mixed gas shielded. Through the simulation and analysis the influence of the electromagnetic force under different shielding gas composition on the bypass droplets transfer, it is found that the bypass droplet diameter decreases by 50% when the shielded gas is 80%Ar+20%CO₂ mixed gas. The simulation result is consistent with the experimental result. It is proved that the electromagnetic force promote the metal transfer to the bypass weld pool with adding CO₂ to rich argon shielding gas and the bypass metal transfer process can be improved.

Key words: gas metal arc welding, metal transfer, simulation