Effects of shielding gas composition on arc properties and wire melting characteristics in narrow gap MAG welding

At constant current, the arc voltage increases with increasing helium or CO2 content. At constant wire feed speed and constant voltage, as the helium or CO2 content increases, the welding current decreases. The arc length decreases significantly with the increase of CO2 content and arc core expands with the increase of helium content. When the shielding gas composition changes, arc properties and wire melting characteristics both change and the arc works at a new equilibrium point to keep the wire melting rate equal to wire feed speed. Shielding gas with the addition of helium presents a bowl weld bead profile. The depth of sidewall fusion increases as helium content increases. The welding process and weld quality are good when the shielding gas is 80%Ar10%CO210%He.