Effect of torch angle on arc properties and weld pool shape in stationary GTAW

摘要

In this paper, a three-dimensional (3D) numerical simulation is performed on a stationary arc to study the effect of torch angles in gas tungsten arc welding (GTAW) of SS304 stainless steel. A comparison has been made to investigate 90 and 70° torch angles and analyze the effect on arc and weld pool shape. Current density, heat flux, and gas shear stress are calculated in the arc region and are used as input to the workpiece to determine the weld pool. Also, both buoyancy and Marangoni shear affect the weld pool shape and are taken into account. The computed and experimental results are observed as symmetric for the 90° torch angle. For the 70° torch angle, current density and hence the heat flux from electron contribution is found to be the maximum behind the electrode tip in the welding direction. Heat flux from conduction and convection is found to be the maximum ahead of the electrode tip in the welding direction. This makes the maximum of total heat flux symmetric along the arc center. Heat flux from conduction and convection decreases as the torch angle decreases resulting in a shallow weld pool. The nonsymmetric w-shaped weld pool is developed by the combined effect of the gas shear and Marangoni convection. It is found that for the 70° torch angle, the weld pool becomes nonsymmetric, shallow, and wide ahead of the electrode tip in the welding direction. The numerical weld pool shapes are verified through experiments.