Numerical simulation of GMAW process using Ar and an Ar-CO2 gas mixture

The gas metal arc welding (GMAW) process involves arc plasma, metal transfer, and weld pool phenomena. In addition, metal vapor is formed by evaporation from the high-temperature metal and mixes with the arc plasma. These phenomena interact with each other and are very complicated. A numerical approach that includes their interaction is therefore important for clarifying the GMAW phenomena. We have developed a unified model and used the model to investigate the influence of the shielding gas on the metal transfer. When argon shielding gas was used, for an arc current of less than 230 A, globular transfer occurred. For higher currents, spray transfer occurred. On the other hand, when Ar + 18 %CO2 gas was used, the transition from globular to spray transfer occurred at around 280 A. This difference was caused by changes in the driving force exerted on the molten metal by the arc plasma. The arc pressure that lifts up the molten metal and interferes with its detachment from the wire tip becomes stronger when the gas mixture is used.