A computational investigation of different helium supplying methods for the improvement of GTA welding

A transient arc and weld pool model is developed, to study the effect of helium addition on the weld pool properties. Supplying mixtures of argon-helium, and alternate supply of pure argon and pure helium, are both studied. The arc characteristics are found to be highly dependent on the shielding gas composition. The addition of helium to argon increases the main governing forces in the weld pool, and more particularly the electromagnetic forces. This leads to the appearing of an electromagnetically induced vortex in the molten pool, which itself leads to an increase in the weld penetration by a factor that goes up to 3. The comparison between the numerical predictions and the experimental macrographs shows a good agreement as well as shape as dimensions. The numerical results reveal two main advantages of alternate supply of shielding gases; compared to the conventional mixtures supplying, the alternate method is more cost saving, and reduces the heat transfer to the workpiece for an equivalent weld penetration. (C) 2011 Elsevier B.V. All rights reserved.