straight Co2 is not ideal, once apona it was widely used but was a real PITA because it freezes and thus needed a specially designed heater at the reg end.... In this weather laying out large beads it would still freeze..
Its also more active than argon rich mixes as is nigh on useless for thin material applications it dissociates at the high temperatures at the bottom of the weld pool, and causes a wider less controlled bead.....Argon Rich mixes will go into spray transfer at lower Voltages...
normally these days straight Co2 is not used, and is blended up to 25% depending on the use, the rest argon with a small bal of Air... this produces less finger like penetration and better wetting control..
However pub Co2 is NOT shielding gas it contains a high balance of O2 and Nitrogen, this will make the weld pool active and porous, It should NEVER be use for a structural joint....
All top end MIGs are now Inverter based, and probably over the next 10 years or so MIG plants will go the same way as TIG, Plasma and MMA with transformer based plants as a rarity rather than the norm..
The advantages of Inverter based MIGs are huge, giving a much wider range of materials that can be welded and the state of globular transfer can be eliminated with the pulsing fetures......
