Difference between ERW and EFW

ERW is the first letter abbreviation for electric resistance welding.
ERW steel pipe and submerged arc welding pipe significantly different, using a pressure-free filler metal welding, the weld is not filled with other ingredients, relying on high-frequency current skin effect and proximity effect, instantly heating the plate edge to welding temperature by squeezing rollers squeeze formed weld forging organizations. High-quality steel pipe welds require online or off-line heat treatment, welding zone structure refinement, quality ERW pipe welds and base metal can reach the same level of toughness, which is submerged arc welding process can not be achieved.
 
EFW steel pipe namely electric fusion welding of the first letter abbreviation.
Submerged arc welding (SAW) - Electric welding (EFW) one, is through one or more consumable electrodes between the workpiece and the heating of the metal between the metal binding of a process, the arc and the metal filling material melted sufficiently, no pressure, filling the metal part of work-all from the electrodes.
 
Melting gas shielded arc welding (GMAW) - Electric welding (EFW) A, similar to this process and submerged arc welding, but it is protected from the inert gas, the effect will be better.