The main shielding gas used in MAG and MIG is argon, but not pure argon, because the following problems arise when using pure argon shielding.

①In the pure argon gas protection will produce a strong jet transition, easy to lead to finger melt depth.

②Welding low carbon steel and low alloy steel, liquid metal viscosity, high surface tension, easy to lead to porosity, edge biting and other defects.

③Welding low carbon steel, low-alloy steel, the arc cathode spot instability, easy to lead to melt depth and welding seam forming uneven, serpentine welding channel.

Therefore, fusion electrode argon arc welding does not generally use pure argon gas for welding, usually according to the materials to be welded using the appropriate proportion of mixed gas.