Why 20%CO2 gas & 80% ARGON gas used in MIG welding instead of 100% ARGON inert gas?
This is a bit complicated. 100% argon causes arc instability when MIG welding. “Arc blow” becomes much more of a problem. Arc blow refers to a wandering, erratic arc which is caused by complicated electromagnetic forces interacting with the arc plasma. The electrical conductivity of the pure argon plasma is relatively poor. This reduces the current and reduces the heat input of the arc, which can cause poor penetration and lack of fusion. Pure argon takes a lot of electrical energy to ionize. It is also a very good thermal insulator (it’s used in double-pane, insulating windows.) Therefore, the arc is very narrow and localized which, without the addition of a more reactive gas tends to aggravate instability and arc blow problems.. CO2 is a moderately reactive gas, as opposed to argon which is extremely inert. It takes much less energy to ionize it into a plasma, therefore adding CO2 makes the arc more conductive. Pure argon has very weak cleaning action compared to Ar+CO2 mixes. Cleani
