Straight seam high frequency (ERW) by welding and induction welding is divided into different forms of contact of two welding, hot-rolled wide coil as raw material, through pre-bending, continuous forming, welding, heat treatment, sizing, straightening, cutting, etc. step short compared to the spiral weld, high dimensional accuracy, uniform thickness, surface quality, under pressure advantages, but the disadvantage is that only the production of small diameter thin-walled tube, easy to produce gray leaf spot weld, incomplete fusion ditch-like corrosion defects. Currently wider field of application of city gas, crude oil and other oil products transportation.
Spiral submerged arc (SSAW
) pipe volume is the forward direction of its centerline forming tube forming angle (adjustable) while forming side welding, weld into a helix, the advantage of the same specifications can produce a variety of diameters steel, adapt to a wider range of raw materials, the main seam can avoid stress, stress better, disadvantage is poor geometry, straight seam weld length compared to the length of the tube, easy to crack, porosity, slag, weld misalignment such as welding defects, welding stress tension state. General Oil and Gas Pipeline design specification spiral submerged arc used only on class 3 and class 4 area. This process will improve foreign raw materials to the steel sheet, so that forming and welding separately, lean pre-welding and after welding cold expanding, its quality close UOE welded pipe, currently there is no such process, is the improvement of plant direction. "East" is still used in the traditional production process, but the pipe end has been expanding. Deny the United States, Japan and Germany in general SSAW, considered the main line should not be used SSAW; Canada and Italy partially used SSAW, Russia sparingly SSAW, and have developed a very strict additional condition, due to historical reasons, the domestic backbone majority still use SSAW .
Straight seam submerged arc (LSAW) is a single plate as the raw material, the pressure plate (volume) in a mold or a molding machine, using double-sided submerged arc welding and expanding the way from production. Its wide range of product specifications, weld toughness, ductility, uniformity and dense better, having a large diameter, wall thickness, high pressure, low temperature resistance, corrosion resistance and other advantages. When the construction of high strength, high toughness, high-quality long-distance oil and gas pipelines, the required large diameter thick wall pipe is mostly a straight seam submerged arc. According to API standards, in large oil and gas pipelines, when through the alpine zone, sea, densely populated urban areas such as Class 1, Class 2 area, straight seam submerged arc tube is the only designated applicable.