What is the difference between seamless steel tube and welded steel pipe?

Steel pipes can be classified according to the rolling process, whether there are seams or not, and the shape of the section. According to the classification of rolling process, steel pipes can be divided in hot-rolled steel pipes and cold-rolled steel pipes; according to whether the steel pipes have seams, steel pipes are divided into seamless steel pipes and welded steel pipes, among which commonly used welded steel pipes can be divided into high-frequency welded pipes according to the type of weld. , straight seam submerged arc welded pipe, spiral submerged arc welded pipe, etc.

The wall thickness of the seamless steel pipe is relatively thick and the diameter thickness is relatively small. However, the pipe diameter is limited, its application is also limited, and the production cost, especially the production cost of large-diameter seamless steel pipes, is relatively high.

The high-frequency welded pipe has good tube shape and uniform wall thickness. The internal and external burrs generated by welding are smoothed by corresponding tools, and the quality of the welding seam is strictly controlled through online non-destructive testing. The degree of automation is high and the production cost is low. However, the wall thickness is relatively thin and the pipe diameter is relatively small, which is especially suitable for making pipe truss structures in steel structures.

The straight seam submerged arc welded pipe adopts the double-sided submerged arc welding welding process, which is welded under static conditions, the weld quality is high, the weld is short, and the probability of defects is small. The steel pipe is expanded through the whole length, the pipe shape is good, the size is accurate, the steel pipe wall thickness range and the pipe diameter range are wide, the degree of automation is high, and the production cost is lower compared with the seamless steel pipe, suitable for buildings, bridges, dams, and offshore platforms Equal steel structure bearing columns, super-span building structures and pole tower mast structures that require wind resistance and earthquake resistance.

The welding seam of the spiral submerged arc welded pipe is spirally distributed, and the welding seam is long. Especially when welding under dynamic conditions, the welding seam leaves the forming point before cooling, and it is very easy to produce welding hot cracks. Therefore, its bending, tensile, compressive and torsional properties are far inferior to those of LSAW pipes, and at the same time, due to the limitation of the welding position, the saddle-shaped and fish-ridge-shaped welds produced affect the appearance. In addition, during the construction process, the intersecting line weld at the node of the spiral welded parent pipe split the spiral seam, resulting in a large welding stress, thus greatly weakening the safety performance of the component. Therefore, the non-destructive testing of the spiral welded pipe weld should be strengthened. Ensure the welding quality, otherwise the spiral submerged arc welded pipe should not be used in important steel structure occasions.

Post time: Mar-22-2022