TWI Industrial Member Report Summary 83/1978
By M Amin
For square wave pulsed MIG welding, it is shown that the entire range of parameters can be predicted for any wire feed speed and droplet volume. The relationship between wire feed speed and pulse parameters is based on the features that the wire feed speed must balance the burnoff rate to maintain a constant arc length, and that controlled metal transfer is maintained. Limiting conditions are set by an empirical isoparametric relationship between pulse current and duration, using data derived from the natural transfer characteristics with steady current.
This approach is confirmed experimentally for five electrode wire and shielding gas combinations, viz. 1.6mm diameter aluminium alloy NG61 in argon, 1.2 and 1.0mm diameter stainless steel in argon 2%02, 1mm diameter mild steel in argon 5%C02 and 1.2mm diameter Inconel in argon.
The general relationship for 'Synergic' pulse operation (whereby pulse repeat frequency, amplitude and duration, and background current, are related to the wire feed speed) is derived directly from the above parametric relationship. This is further extended to show that both the background current and the product of the pulse duration, repeat frequency and the excess of the pulse current over the background level, must vary proportionally with the wire feed speed.