Modeling of Transport Phenomena in Dissimilar GTA Weld Metals

A finite element simulation of spot gas tungsten arc welding (GTAW) of 2205 duplex stainless steel to 1018 carbon steel without consumable is proposed in this study. To predict welding parameters (that affect the weld quality) such as weld zone geometry (depth/width ratio), thermal stress residues and mixing rate (compositional homogeneity across the weld zone) especially in dissimilar metal welding, one needs to study fluid flow, heat transfer and mass transfer during the welding process.

 Finite element analysis software COMSOL Multiphysics is used for simulation of transport phenomena. 3-D modeling of fluid flow and heat transfer in weld pool leads to prediction of weld zone shape and accordingly the weld penetration. Various driving forces such as electromagnetic, buoyancy and Marangoni convective forces are considered in the simulation. Moreover, a 3-D model of mass transfer is developed to calculate the mixing rate of different alloying elements throughout the weld pool and consequently the compositional variation across the depth and width of the weld zone. Modeling simulation is repeated for different welding currents and times to determine the optimum penetration and mixing rate.

 Experimental tests are carried out to study the chromium and nickel concentrations in four different locations across the weld zone using x-ray and analytical microscopy. Results from modeling and experiment are compared and a good agreement is achieved.