Study on the effect of contact tube-to-workpiece distance on weld pool shape in gas metal arc welding

Computer simulations of the three-dimensional heat transfer and fluid flow in gas metal arc (GMA) welding have been studied for analyzing the effect of contact tube-to-workpiece distance on the weld pool shape by considering the driving forces for weld pool convection, the electromagnetic force, the buoyancy force and the surface tension force at the weld pool surface, and also the effect of molten electrode droplets. In the numerical simulation, difficulties associated with the irregular shape of the weld bead have been successfully overcome by adopting a boundary-fitted coordinate system that eliminates the analytical complexity at the weld pool and bead surface boundary. The method used in this paper has the capacity to determine the weld bead and penetration profile by solving the surface equation and convection equations simultaneously. The experiments are performed to show the variation of the weld bead geometry due to the change of the contact tube-to-workpiece distance. The calculated weld shapes correspond well with those of experiments, and both these results demonstrate that the contact of tube-to-workpiece distance exerts a considerable influence on the formation of the weld pool and the resulting weld shape by affecting the arc length and welding current.