Arc characteristics and behaviour of metal transfer in pulsed current GMA welding of aluminium alloy

The variation in arc characteristics, stability in shielding of arc environment and behaviour of metal transfer with variation in pulse parameters have been studied by high speed video photography during GMA weld deposition using Al-Mg filler wire. The effect of pulse parameters has been studied by considering their hypothetically proposed summarised influence defined by a dimensionless factor phi= [(I-b/IIp)ft(b)], mean current and arc voltage. The arc characteristics studied by its root diameter, projected diameter and length, the instability of shielding environment reflected by its puncturing through vortex formation and the behaviour of metal transfer noted by the diameter and velocity of droplet at the time of detachment and deposition in weld pool have been found to vary significantly with the pulse parameters. At a given pulse parameter the experimentally measured values of the behaviour of metal transfer are found well in agreement to their corresponding theoretical values estimated through mathematical expressions. The observation may help in understanding the weld characteristics with respect to variation in pulse parameters which may be beneficial in using pulsed current GMAW to produce desired weld quality. (C) 2007 Elsevier B.V. All rights reserved.