2012 Volume 30 Issue 1 Pages 100-106
In this paper, metal transfer modes of mild steel wire of 1.2 mm in diameter, which were observed for welding variables of current, voltage and polarity in Gas shielded Metal Arc Welding process with four kinds of shielding gases (Ar, He, CO2 and mixture gas of Ar+20%CO2) are described. In electrode positive polarity, metal transfer transition from globular to spray occurs with use of shielding gas of Ar or Ar+20%CO2. But with shielding gas of He or CO2 only globular transfer was observed. In electrode negative polarity, mild steel wire added by a very small amount of Rare Earth Metal, which promotes electron emission at the cathode, makes globular to spray transition possible with shielding gas of CO2 or Ar+20%CO2. Other combinations of shielding gas and electrode wire result in globular transfer in the current range up to 400 A. In spray transfer mode, current density was estimated to be higher than 1×108 A/m2 at the surface of metal drop onto detachment.
