Influence of pulse parameters on bead geometry and HAZ during bead on plate deposition by MIG welding process

Beads of Al-4.5 Mg filler wire were deposited on extruded commercial aluminium plates with the help of continuous current and pulsed current MIG welding processes, where the mean welding current, peak current, pulse frequency and pulse duration are varied within a suitable range. In case of pulsed current deposition the effect of variation of any parameter on the consequent changes of pulse characteristic have been identified. Finally the pulse characteristics have been suitably classified so that the effect of any parameter on the bead geometry and heat affected zone (HAZ) can be evaluated under a given narrow range of other parameters. It was observed that the deposition characteristic was comparatively better when the pulsed MIG process was used at a mean current in the vicinity of transition current and above a pulse frequency beyond 25 Hz and duration of 4.52 ms. At given mean, peak and base currents and pulse frequency the increase in pulse duration in general has been found to enhance the bead width, penetration and dilution and to reduce the hardness of the HAZ close to the fusion line. The use of pulse current welding has been found to enhance the bead height, width and penetration over that observed when a continuous current was used.