Effect of welding speed and wire feed rate on arc characteristics, weld bead and microstructure in standard and pulsed gas metal arc welding

Abstract

Standard and pulsed gas metal arc welding (GMAW) were performed at a constant welding speed of 300, 600, and 1000 mm/min with eight different wire feed rates (WFR). The effect of input parameters on arc stability, metal transfer mode, penetration depth, hardness, and microstructure was discussed. Voltage and current transients recorded by oscilloscope were used to analyse the arc stability and metal transfer mode by plotting probability density distribution (PDD) graphs of arc voltage and welding current. With an increase in WFR, standard GMAW transformed from bimodal to unimodal (due to the absence of short-circuiting mode and activation of pulsed mode) and the pulsed GMAW graph transformed from multimodal to bimodal (due to faster droplet detachment and lowered background current duration). In addition, a nonlinear mathematical model was generated to adequately predict bead profile parameters. For both standard and pulsed GMAW, maximum penetration depth was achieved at the lowest welding speed and highest WFR. But deeper penetration was achieved in pulsed G compared to the standard for the same input parameters. Hardness and the number of non-diffusional phases in the weld and heat-affected zone (HAZ) increased with welding speed.