It helps to give the weld metal a relatively large and round shape which is illustrated in the illustration below. The shape and size of the weld metal provides further resistance to lack of fusion and porosity in the weld metal.

Penetration performance of a shielding gas consisting of only CO2.

CO2 is normally added in relatively small amounts. If the CO2 content in the shielding gas is too high, it will obstruct the formation of spray arc welding. The maximum CO2 content under which spray arc welding is feasible in Ar/CO2 mixtures is approximately £ 25%.

The carbon dioxide in the Ar/CO2 shielding gas mixtures stabilizes the arc.