Difference of ERW and EFW

ERW That first letter of the acronym ERW Electric resistance welding
ERW pipe and submerged arc welding pipe significantly different, with the pressure welding without filler metal, weld not filled with other ingredients, by high-frequency current skin effect and proximity effect, instantly heating the plate edge to welding temperature by squeezing rollers squeeze forging formed weld tissue. Require the use of high-quality steel pipe weld line 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 namely electric welding Electric fusion welding of the first letter abbreviation
Submerged arc welding (SAW) - Electric welded (EFW) one, is through one or more consumable electrode between the workpiece and the heating of the metal between the metal binding in a process, the arc of the metal and filling material sufficient to melt, no pressure, filling the metal part of work-all from the electrode.
Melting gas shielded arc welding (GMAW) - electric welded (EFW) in a similar process with such a SAW, but it's protected from the inert gas, the effect will be better.
Spiral submerged arc welding --- this is one with a spiral weld.

ERW pipe also known, is a steel plate or strip after curl forming welded steel. Welded steel pipe production process is simple, high production efficiency, different specifications, less capital equipment, but the general strength of less than seamless steel tubes. Since the 1930s, with the progress of high-quality steel rolling production and the rapid development of welding and inspection techniques, weld quality continues to improve, welded steel pipe increasing varieties and specifications, and in more and more areas instead of no pipe joints. Seam welded steel pipe in the form of divided Longitudinal and spiral welded pipe. Longitudinal production process is simple, high production efficiency, low cost, rapid development. The strength of the spiral welded pipe is generally higher than the Longitudinal, can narrow the billet production of large diameter pipe, you can also use the same width of the billet production of different pipe diameters. However, compared with the same length of straight pipe seam weld length of 30 to 100%, and lower production rate. Therefore, smaller diameter pipe were powered by straight seam welded, large diameter spiral welded pipe for the most