Arc characteristics and behaviour of metal transfer in pulsed current GMA welding of stainless steel

The variation in arc characteristics, stability in shielding of arc environment and behaviour of metal transfer with a change in pulse parameters have been studied by high speed video-photography during pulsed current gas metal arc (P-GMA) weld deposition using austenitic stainless steel filler wire. A comparative study of similar nature has also been carried out during gas metal arc (GMA) weld deposition in globular and spray transfer modes. The effect of pulse parameters has been studied by considering their hypothetically proposed summarized influence defined by a dimensionless factor phi = [(I-b/I-p) ft(b)], mean current and arc voltage and correlation between welding parameters and arc characteristics have been established. The arc characteristics studied by its root diameter, projected diameter, length and stiffness measured in terms of arc pressure and the behaviour of metal transfer noted by the droplet diameter and velocity of droplet at the time of detachment have been found to vary significantly with the variation in phi. At a given phi the experimentally measured values of the behaviour of metal transfer are found well in agreement to their corresponding theoretical values estimated through mathematical expressions reported earlier. The increase of phi and the ratio of (I-b/I-P) have been found to adversely affect the stability of shielding jacket and arc profile especially at high arc voltage. (C) 2008 Published by Elsevier B.V.