ERW is the first abbreviation of resistance welding.
ERW pipe is obviously different from submerged arc welded pipe. The weld seam is welded with no pressure filling metal and other components are not filled. Depending on the skin effect and proximity effect of high frequency current, the welding forging structure is extruded from the edge of heating plate to the welding temperature by extrusion roll. Welding of high quality steel pipe requires on-line or off-line heat treatment. The structure of welding zone is refined. The weld seam and base metal of high quality ERW pipe can reach the same level of toughness, which can not be achieved by submerged arc welding technology.
 
EFW steel pipe is the abbreviation of the first letter of electrofusion welding.
Submerged arc welding (SAW) - electric welding (EFW) is a metal bonding process between workpiece and metal heating between one or more consumable electrodes. The arc and metal filling materials are fully melted and pressure-free, and all working metal parts are filled from the electrodes.
 
Melting gas shielded arc welding (GMAW) - electric welding (EFW) A is similar to this process and submerged arc welding, but it can protect against the influence of inert gases, the effect will be better.