Numerical Analysis of Fully Penetrated Weld Pools in Gas Tungsten Arc Welding

Abstract
Full penetration welding is widely used in metal joining, but it has been ignored in previous convective numerical models. In addition to the free surface on top of the pool, an additional free surface appears on the bottom of the workpiece. It can be shown that the top surface, temperature distribution and fluid flow field in the weld pool are all coupled with the pool's bottom surface. This complicates the numerical process and therefore no convective models have previously been developed for fully penetrated weld pools. In order to improve the numerical solution for the fully penetrated weld pool, a three-dimensional model is proposed. Free top and bottom pool surfaces have been included. The electromagnetic force, buoyancy force and surface tension gradient (Marangoni) are the three driving forces for weld pool convection. Welding parameters are changed in order to analyse their effects on weld pool geometry. It is found that the depression of the top surface contains abundant information about the full penetration state as specified by the back-side bead width.

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