COMPUTER SIMULATION OF THREE‐DIMENSIONAL CONVECTION IN TRAVELLING MIG WELD POOLS

Mathematical models of the metal‐inert gas (MIG) welding process may be used to study the influence of various welding parameters on weld dimensions, to assist in the development of welding procedures, and to aid in the generation of process control algorithms for automated applications. A three‐dimensional model for convection and heat transfer in MIG weld pools has been formulated and solved using the finite difference technique. The energy exchange between the pool and the molten filler metal droplets via spray transfer, and the interaction of electromagnetic, buoyant, surface tension, droplet impact and plasma jet forces were considered. MIG welding was carried out using mild steel plate with heat input from 7 to 17.5 KJ/cm. The calculated and experimentally observed weld bead dimensions were compared. Occurrence of finger penetration phenomena only in MIG welds are adequately explained through the application of the proposed model. Good agreement is demonstrated between predicted weld dimensions and experimentally measured ones.