| Abstract Scope |
Gas tungsten arc welding (GTAW) is widely used for joining metallic materials, but controlling weld penetration and fusion-zone geometry remains challenging, particularly under stationary heat input and in future dissimilar-metal applications. In conventional GTAW, the arc remains fixed relative to the workpiece, which can produce localized heating and limited control of weld-pool circulation. In this study, a rotating-electrode GTAW process is investigated numerically and experimentally to improve weld-pool convection, penetration, and fusion-zone development.
A three-dimensional transient model was developed in COMSOL Multiphysics® to simulate stationary spot welding of AISI 1018 steel. The workpiece was modeled as a solid domain with a localized liquid weld-pool region to reduce computational cost while capturing molten-metal flow. Heat transfer was solved in both solid and liquid regions, and fluid flow was solved in the weld-pool domain. Phase change was modeled using the apparent heat capacity method with liquid-fraction tracking. The momentum equation included buoyancy, Lorentz force, Marangoni force, and Carman–Kozeny damping in the mushy and solid regions.
The welding arc was represented by Gaussian heat-flux and normal-current-density distributions on the top surface. For rotating-electrode cases, the heat and current input centers rotated around the weld center at prescribed rotational speeds. The electric-current field was solved to obtain current density, and the Lorentz force was calculated from the interaction between current density and magnetic flux density. Temperature-dependent Marangoni shear stress was applied on the top free surface for 0.03 wt.% sulfur steel.
Results showed that electrode rotation transforms the weld-pool flow from nearly symmetric circulation to time-dependent rotating flow. The 600 RPM case produced stronger internal convection, deeper penetration, and a larger molten region than the stationary case. Experimental cross-sections from AISI 1018 and AISI 304 welds at 0, 300, and 600 RPM showed increased penetration with rotation, supporting the model predictions. |