Special welding electrode consisting of a composite wire and adapted for use in CO2 shield gas arc welding, said welding electrode comprising a tubular outer casing of mild steel having a central hollow and a filler enclosed in said central hollow and composed of ferromanganese in an amount not less than 1.0 percent but not more than 2.2 percent based on manganese of the weight of the electrode, ferrosilicon in an amount not less than 0.3 percent but not more than 0.9 percent based on silicon of the weight of the electrode, ferroaluminum in an amount not less than 0.05 percent but not more than 0.8 percent based on aluminum of the weight of the electrode, an arc stabilizer consisting of a salt or oxide of alkali metal in an amount not less than 0.1 percent but not more than 3.0 percent of the weight of the electrode and the remainder of iron powder which may be added as required.