Numerical simulation of arc characteristics in narrow gap TIG welding

Narrow gap TIG welding is a high-quality solution for joining thick structures with reduced costs. However, the matching between numerous parameters is required to achieve satisfactory weld quality since its nature of multi-layer and single pass welding makes the repair difficult. This study aims to lay the theoretical foundation for the process design by building a deep understanding of the arc characteristics during narrow gap TIG welding. The 3D MHD simulation is carried out to investigate the influence of arc weaving and anode surface shape on characteristics of steady arc plasma, and the results are validated by experiments. Results show that as the electrode weaves from groove center to the side wall, local concentration of current density leads to the climbing of arc root on the side wall. The flow pattern of arc plasma changes from reverse circulation to inclined downward, results in the decrease of heat efficiency. As the shape of anode surface changes from concave downward to convex upward, the arc root shrinks but with a decrease of heat efficiency.