In gas welding and tungsten gas shielded arc welding, the welding wire is replaced with filler metal; in submerged arc welding, electroslag welding and other molten electrode gas shielded arc welding, the welding wire is used as a filler metal or at the same time as a conductive wire welding material . , The welding wire is not only a filler metal, but also a conductive electrode. The surface of the welding wire is not coated with anti-oxidation flux.