ERW is high-frequency resistance welding straight seam welded pipe; LSAW is submerged arc welding straight seam welded pipe; Both belong to straight seam welded pipe, but the welding process are different. So you can't say one of them on behalf of the straight seam welded pipe. More common steel pipe is SSAW - spiral welded pipe. High frequency straight seam (ERW) according to the welding process is divided into different induction welding and resistance welding two forms, based on hot rolled wide volume as raw material, through the continuous forming, bending, welding, heat treatment, sizing, straightening, cutting process. Compared with the SSAW, high dimensional accuracy, uniform wall thickness, good surface quality, high pressure is all the advantage. But the disadvantage is that only product small diameter thin wall pipe, weld easy generation resistant, incomplete fusion, trench corrosion defects. Widely used such as city gas, crude oil transportation. The material of LSAW steel pipe is single thick steel plate,the steel in the mold or molding machine medium-voltage (volume), using double-sided submerged arc welding Its finished product specification range is wide, the toughness of the weld, plasticity, good uniformity and compactness, with large pipe diameter, wall thickness, strong resistance to high pressure, low temperature corrosion resistance, etc. In the construction of high strength, high toughness, high quality of long distance oil and gas pipeline, the steel tube are mostly large diameter thick wall straight seam submerged arc. According to the provisions of the API standard in large oil and gas pipelines, when the elevations, sea and city populated area in class 1, 2, straight seam submerged arc is the only designated for tube type. According to the forming methods of different can be divided into: UOE/JCOE/HME. Volumes of spiral submerged arc (SSAW) is in the direction with the center line of the pipe forming forming Angle (adjustable), forming and welding, the welding seam into spiral, advantage is that it can produce various specifications of steel pipe diameter of the same specification, raw material range is larger, the weld can avoid the principal stress, the stress condition is good, the disadvantage is that poor geometry size, weld length compared with straight seam length, easy to produce cracks, porosity, slag, weld defects such as welding, welding stress is tensile stress state. The rules and regulations of general oil and gas long distance pipeline design screw Spiral submerged arc can only be used for three classes, class area. 4 foreign this process will be improved raw materials instead of steel plate, forming and welding, then welding and lean, cold expanding, after welding, the welding quality is close to UOE tube, at home there is no such process, is the direction of our factory to improve. "West-east gas" is still used by traditional craft production, only the pipe hole enlargement. The United States, Japan and Germany, on the whole, negative SSAW, don't think it is proper to use SSAW trunk; Canada and Italy part use SSAW, Russian, a small amount of use of SSAW, and have made a very strict complementary condition, due to historical reasons, most domestic trunk also is to use SSAW.