Coupled Field Analysis of a Gas Tungsten Arc Welded Butt Joint—Part II: Parametric Study

Abstract

The process of welding has a direct influence on the integrity of the structural components and their mechanical response during service. Welding is an inherently multiphysics problem, encompassing a large array of physical phenomena—fluid flow in the weld pool, heat flow in the structure, microstructural evolution/phase transformations, thermal stress development, and distortion of the welded structure. The mathematical model to simulate the coupled fields of the welding process has been outlined in Part I of the present study. In Part I, the developed model have been validated with experimental results and the depth/width (D/W) predictions agree well. Part II documents the effects of welding parameters (welding current/speed, electrode gap, and electrode angle) on the weld D/W ratio, for both low (≤40 ppm) and high (≥150 ppm) surface active agent (oxygen) content. The parametric characterization of the weld D/W ratio is validated with published experimental data. They agree well. Results show that increasing the oxygen content beyond 150 ppm does not increase the weld D/W ratio. At high oxygen content of 150 ppm and under current variation, the weld D/W ratio increases and remains constant beyond 160 A. However, when the welding speed is varied, the weld D/W ratio decreases with increasing speed. Similarly, increasing the electrode gap under high oxygen content decreases the weld D/W ratio. The weld D/W ratio shows weak variation with electrode tip angle. The results from the present simulations have also been used to predict the modes of weld solidification. With increase in welding speed, finer dendritic microstructures are expected to be formed near the weld centerline. The variation of weld D/W with heat input per unit length of weld is also presented elaborately. The workpiece deformation and stress distributions are also highlighted. The present study shows the pertinence of coupled welding process simulation to delineate the underlying physical processes and thereby better predict the behavior of welded structures.