Pulsed MIG/MAG welding is a variant of the conventional MIG/MAG welding process in which the current is pulsed. Pulsing was introduced originally for control of metal transfer at low mean current levels by imposing short duration high current pulses. The cycle consists of applying the repeated pulse current over a constant background current:
Modern welding sets permit the use of a wide range of pulse amplitudes, durations and waveforms at frequencies from a few Hertz to a few hundred Hertz. Pulse amplitude and duration are best combined to melt and detach a single droplet of the same/slightly smaller diameter as the electrode wire. Selection of pulse parameters for a given wire feed speed is a complex operation. Pulse height and duration are a function of wire composition, diameter and to alesser extent, shielding gas composition. This has lead to the advent of Synergic welding sets (see FAQ: "What is Synergic MIG/MAG welding and what are its advantages?" )
The principal advantages of pulsed MIG/MAG welding are:
- It allows the use of smooth, spatter free welding at mean currents (50-150A), which would otherwise be too low for all except dip transfer with its irregular transfer and associated spatter.
- Pulsing can extend spray operation below and through the natural transition (180-220A for 1-1.2mm mild steel wire) from dip to spray where globular transfer would normally occur.
- Pulsed transfer is midway between spray transfer and the dip transfer mechanism, which can be too 'cold' (due to non-continuous arcing; the arc effectively 'goes out' between each melting cycle). This makes it ideal for welding thicker sections where more heat is needed but for which spray transfer is still too 'hot'.
- Pulsed MIG allows welding at higher deposition rates in all positions where dip or spray transfer are not applicable.