中文摘要：

双丝旁路耦合电弧熔化极气体保护焊过程中,由于旁路电弧选择了直流正极性接法,采用常规纯氩气保护时旁路熔滴体积较大且过渡过程不稳定。为此,提出采用80%Ar＋20%CO2作为保护气体,通过改变熔滴表面的受力形式,改善旁路熔滴过渡过程。在此基础上,通过建立可以描述旁路熔滴过渡行为的动态数学模型,模拟分析不同受力形式下的旁路熔滴直径变化与过渡过程。结果表明：采用纯氩气保护时,不同旁路电流参数下的旁路熔滴直径为2.6～3.3 mm且难以过渡,采用80%Ar＋20%CO2混合气体保护时,旁路熔滴直径减小至0.6～1.1 mm且过渡频率加快;通过模拟分析不同保护气体成分下电磁力对旁路熔滴过渡的影响,发现采用80%Ar＋20%CO2混合气体保护时旁路熔滴直径减小了50%,与试验结果基本一致,证明了富氩保护气体中加入CO2可以使得电磁力重新促进旁路熔滴向熔池过渡,从而改善了旁路熔滴过渡过程。

英文摘要：

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 that：with 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.