Three-dimensional Heat Transfer Analysis of Two Wire Tandem Submerged Arc Welding

Abstract

Two wire tandem submerged arc welding process facilitates high rate of joint filling with little increase in the overall rate of heat input due to the simultaneous deposition from two electrode wires. Since the lead wire is usually connected to a DC welding arc and the trail wire to a pulsed AC arc, the tandem process requires appropriate selection of a large number of process variables. A quantitative understanding of the effect of the welding conditions on weld joint dimensions and weld thermal cycle is difficult through experimental studies only. Here we present a three-dimensional heat transfer analysis based on finite element method using two independent volumetric heat sources to account for heat input from two welding arcs. The shapes of the heat sources are estimated based on the original joint geometry and welding conditions. The results show that the trail wire current pulses significantly influences the reinforcement height and weld width while lead wire current affects the depth of penetration. For a constant trail wire effective current, increase in the negative pulse time results in greater reinforcement height and reduced weld width with very little influence on the cooling rate and weld strength. In contrast, increase in trail wire negative current pulse increases both reinforcement height and weld width while reduces cooling rate and weld strength.