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 two have different welding processes and different uses, so they cannot represent straight seam welded pipe alone. SSAW-spiral welding-spiral welded pipe is more common.
Straight seam high frequency (ERW steel pipe
) is divided into induction welding and contact welding according to different welding methods, using hot rolled wide coil as raw material, after pre-bending, continuous forming, welding, heat treatment, sizing, straightening, cutting Compared with the spiral, it has the advantages of short weld seam, high dimensional accuracy, uniform wall thickness, good surface quality, and high pressure. However, the disadvantage is that it can only produce small and medium-diameter thin-walled pipes. Fusion, groove-like corrosion defects. The currently widely used areas are urban gas and crude oil product transportation.
Straight seam submerged arc (LSAW steel pipe
) is produced by using a single medium-thick plate as the raw material, pressing (rolling) the steel plate in a mold or forming machine, using double-sided submerged arc welding and expanding the diameter. The finished product has a wide range of specifications, good toughness, plasticity, uniformity and compactness of the weld, and has the advantages of large pipe diameter, pipe wall thickness, high pressure resistance, high temperature resistance and corrosion resistance. When constructing high-strength, high-toughness, high-quality long-distance oil and gas pipelines, most of the steel pipes required are large-diameter thick-walled straight-seam submerged arcs. According to API standards, in large oil and gas pipelines, when passing through Class 1 and Class 2 areas such as alpine areas, seabeds, and densely populated urban areas, straight submerged arcs are the only designated pipe types. According to different molding methods, it can be divided into: U0E/JCOE/HME.
Spiral submerged arc (SSAW steel pipe
) is when the tube is rolled, its advance direction has a forming angle (adjustable) with the center line of the forming tube, and it is welded while forming, and its welding seam is formed into a spiral line. The advantage is that the same specification can produce a variety of diameter specifications Steel pipe, the raw material adapts to a larger range, the weld can avoid the main stress, and the stress is better. The disadvantage is that the geometric size is poor. The length of the weld is longer than that of the straight seam. It is prone to cracks, pores, slag inclusions, and welding deviation. For welding defects, the welding stress is in the state of tensile stress. -The design specifications of general oil and gas long-distance pipelines stipulate that spiral submerged arc can only be used in Category 3 and Category 4 areas. After the process is improved abroad, the raw material is changed to a steel plate to separate the forming and welding. After pre-welding and precision, the diameter of the welding is expanded after cold welding. The welding quality is close to the UOE tube. At present, there is no such process in China. It is an improvement of our factory. Direction. The "West-to-East Gas Pipeline" is still produced according to the traditional process, but the pipe end has been expanded in diameter. The United States, Japan and Germany generally reject SSAW, and believe that the main line should not use SSAW; Canada and Italy use SSAW in part, and Russia uses SSAW in a small amount, and they have formulated very strict supplementary conditions. Due to historical reasons, most domestic main lines still use SSAW.
1. Welded pipe refers to the ordinary "submerged arc welded steel pipe", which is represented by "SC" in electrical engineering.
2. The line pipe, which is the wire pipe, is relatively thin. It is indicated by "T" and can only be used as a threading pipe.
3. The ERW pipe is a "high-frequency resistance welded steel pipe", which is different from the ordinary welding pipe welding process. The welding seam is made of the steel strip body
The base material is melted and the mechanical strength is better than that of ordinary welded pipe.