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LSAW – Longitudinally Submerged Arc Welding. LSAW pipes are produced by using single sheets of medium-thick steel as raw material; these sheets are pressed (rolled) into tube blanks in molds or forming machines, and then welded using the double-sided submerged arc welding method along with diameter expansion. Its finished products have a wide range of specifications; the welds exhibit good toughness, plasticity, uniformity, and density. It offers advantages such as large pipe diameters, thick wall thicknesses, as well as strong resistance to high pressures and low temperatures along with excellent corrosion resistance. When constructing high-strength, high-toughness, high-quality long-distance oil and gas pipelines, the steel pipes required are mostly large-diameter, thick-walled straight-seam submerged arc welded pipes. According to API standards, in large oil and gas transmission pipelines. Straight-seam submerged arc welded pipe is the only specified suitable pipe type. Depending on the forming method, it can also be classified as follows: UOE welded pipe: A single steel sheet is pre-bent at the edges, and then undergoes processes such as U-forming, O-forming, internal welding, external welding, and mechanical cold expansion ； JCOE welded pipe: That is, it goes through processes such as pre-welding, shaping, welding, and subsequent cold diameter expansion according to the “J-C-O-E” method ； HME welded pipe: formed by core rolling in the “C-C-O” pattern, and undergoes processes such as cold expansion after welding.