The difference between ERW, SSAW and LSAW

Steel pipe manufacturing process according to different, can be divided into (SML), as the main oil gathering pipe and the small caliber high pressure natural gas pipeline, the number for the long oil pipeline is very few, most of the pipeline is the use of high-frequency straight seam (ERW), spiral submerged arc (SSAW), submerged arc (LSAW) three. The following table for several technological characteristics of the steel pipe and the quality of performance comparison: longitudinal high-frequency (ERW) according to different welding modes are divided into induction welding and contact welding in two forms, the hot rolled wide roll as raw material, after pre bending, continuous molding, welding, heat treatment, sizing, straightening, cutting and other processes, and the spiral compared with the short welding seam, high precision, uniform thickness, good surface quality, high pressure, but the drawback is the production of small diameter thin-walled tube only, weld is easy to produce gray spot and lack of fusion, groove corrosion defects. At present, the widely used fields are city gas, crude oil delivery and so on. Spiral submerged arc (SSAW) is the direction of rolling and forming tube center line forming angle (adjustable), side molding and welding, the welding seam of the spiral line, has the advantages of steel pipe of the same specifications can produce a variety of diameter specifications, raw materials to a large range, the weld can avoid stress, stress well, the disadvantage is poor compared to geometric size, the length of the weld seam length, cracks, porosity, slag, weld offset of welding defects, the welding stress is tensile stress. The general oil and gas pipeline design specification stipulates that the spiral buried arc can only be used in 3 types and 4 types of areas. This process improved the foreign raw materials will be changed into the steel, forming and welding separated by pre welding and lean, after welding cold expansion, the welding quality is close to UOE, currently there is no such process, our factory is the direction of improvement. The use of "west to East Gas Transmission" is still produced according to the traditional process, but the pipe end has been expanded. The United States, Japan and Germany's overall negative SSAW, that the main line is the use of SSAW; Canada and Italy part of the use of SSAW, Russia's use of a small amount of SSAW, and has formulated the supplementary conditions very strict, due to historical reasons, most of the domestic trunk or the use of SSAW. The longitudinal submerged arc (LSAW) is a single thick plate as raw materials, the steel plate in the mold or molding machine pressure (volume), using double-sided submerged arc welding and expanding into production. Its finished product specification range is wide. The toughness, plasticity, uniformity and compactness of the weld are good. It has the advantages of large diameter, thick wall, high pressure resistance, low temperature resistance and strong corrosion resistance. In the construction of high strength, high toughness and high quality long distance oil and gas pipelines, most of the steel pipes required are large diameter thick wall straight seam submerged arc. According to the API standard, in large oil and gas transmission pipeline, when passing through 1 or 2 kinds of areas, such as alpine region, seabed and urban densely populated area, the longitudinal submerged arc is the only specified pipe type. According to the different molding methods can be divided into: UOE: single steel plate at the edge of the pre bending, U molding, O molding, welding, welding, machinery in the cold expansion process; JCOE: according to the "J-C-O-E" pre welding, molding, welding after the cold expansion process; HME: by mandrel according to the "C-C-O" method of rolling forming and welding after the cold expansion process.