How is the Welded Steel Pipe Made?

Welded steel pipe is joint steel pipe. The production process is to bend the tube blank (steel plate and steel strip) into the tube with the required cross-section shape and size by various forming methods, and then weld by different welding methods. The process of obtaining steel pipes. Compared with seamless steel pipe, welded pipe has the characteristics of high product precision, especially high wall thickness precision, simple main equipment, small floor area, continuous production, flexible production and wide range of unit products.


From the perspective of production process, welded pipe is divided into: spiral submerged arc welding; LSAW (longitudinal submerged arc welding); ERW (resistance welding).


ERW steel pipe: high frequency straight seam resistance welded pipe, which is made of hot rolled wide rolled material, after pre bending, continuous forming, welding, heat treatment, sizing, straightening, cutting and other processes comparison, spiral shape, short weld, high standard accuracy, uniform wall thickness, good surface quality, high pressure, but the disadvantage is that only small and medium diameter thin-walled pipe may produce weld, and the weld is prone to gray spots Corrosion defects in fusion and similar grooves. Today, the most widely used areas are urban natural gas and crude oil products.


SSAW steel pipe: spiral submerged arc welded pipe. When the coil is rolled, the forward direction of the coil has an adjustable forming angle with the center line of the forming tube. When welding forming pipe, the weld is spiral, and the profit is the same standard. For the standard diameter steel pipe, material Xi has a larger conventional scheme. The main stress can be avoided and the stress is better. The defect is several standards. The length of the weld is longer than the straight pipe, and the crack slag is easy to crack. Welding defects such as welding deviation, welding stress is tensile stress. The spiral submerged arc of general oil and gas long-distance pipeline design standard rules can only be used in Level 3 and level 4 areas.


LSAW steel pipe: straight seam submerged arc welded pipe is made by pressing a single piece of medium thick plate in a mold or molding machine, and adopting double-sided submerged arc welding method and expanding its size. Diameter produced. The standard planning range of its products is wide, the weldability, plasticity, uniformity and fineness of the weld are good, and it has the advantages of large pipe diameter, thick pipe wall, high pressure resistance, low temperature resistance and corrosion resistance. When creating long distance oil and gas pipelines with high strength, high resistance and high quality, most of the steel pipes needed are large diameter thick wall straight seam submerged arc. According to API standard rules, in large oil and gas transmission pipelines, when passing through sub areas of alpine area and densely populated areas of cities, straight seam submerged arc is only the specified applicable pipeline type.