Particle Method Simulation of Blowhole Forming Process during Gas Metal Arc Welding

The blowholes caused by the entrainment of Ar as a shielding gas in gas metal arc welding have not been adequately studied because of the unknown occurrence mechanism and appropriate welding conditions. In this study, a computational model using a two-dimensional particle method was developed to simulate the gas–liquid two-phase fluid behaviors consisting of molten metal and Ar gas for elucidating the mechanism of the blowhole formation owing to shielding gas entrainment and for proposing appropriate welding conditions that can suppress the formation. To simulate two fluids with significant density differences, such as molten metal and Ar gas, a computational model using particle number density was developed to normalize the behavior of particles at the gas–liquid interface. The computational results obtained by the developed model exhibited good agreement with experimental observation, qualitatively verifying the model. Subsequently, the difference in the amount of Ar gas entrainment owing to the difference in surface tension was simulated using the model. The computational results showed that the amount of entrained Ar gas increased as the surface tension decreased, might be because of a change in the shape of the molten metal droplet caused by the decrease in the surface tension. This suggested that changes in the surface tension of the molten metal caused by shielding gas components may affect the amount of blowhole generated by the entrainment of shielding gas.