Steel pipes can be classified according to rolling processes, whether there are seams, and cross-sectional shapes. According to the rolling process classification, steel pipes can be divided into hot-rolled steel pipes and cold-rolled steel pipes, according to whether there are seams in steel pipes, 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 types of welds. Three kinds of straight seam submerged arc welded pipes and spiral submerged arc welded pipes. The advantages and disadvantages of various types of steel pipes are:
1, seamless steel pipe
The seamless steel pipe has a relatively thick wall thickness and a small diameter. However, the pipe diameter is limited, its application is also limited, and the production cost, especially the production cost of large-diameter seamless steel pipe is relatively high.
2, high frequency welded steel pipe
The high-frequency welded pipe has good shape and uniform wall thickness. The inner and outer burrs generated by welding are flattened by the corresponding cutters. The quality of the weld is strictly controlled by non-destructive testing on-line, with high automation and low production cost. However, the wall thickness is relatively thin, the pipe diameter is relatively small, the wall thickness generally does not exceed 12 mm, and the pipe diameter generally does not exceed 610 mm. The steel structure is particularly suitable for the pipe truss structure.
3, straight seam submerged arc welded pipe
The straight seam submerged arc welded pipe adopts the + double-sided submerged arc welding process and is welded under static conditions. The weld quality is high, the weld bead is short, and the probability of defects is small. The steel pipe has a full-length diameter expansion, good tubular shape, accurate size, wide wall thickness range and wide diameter of the steel pipe, diameter range up to 406-1829mm, wall thickness range up to 6.0-60mm, high degree of automation, and seamless Compared with steel pipes, the production cost is low, and it is suitable for steel structure supporting columns such as buildings, bridges, dams, and offshore platforms, super-long span building structures, and electric tower tower structures requiring wind and earthquake resistance.
4, spiral submerged arc welded pipe
Spiral submerged arc welded pipe welds are spirally distributed, and the welds are long. Especially when welding under dynamic conditions, the welds leave the forming point before cooling, and it is easy to produce welding hot cracks. The direction of the crack is parallel to the weld and is at an angle to the axis of the steel pipe, typically between 30 and 70 degrees. This angle is just the same as the shear failure angle, so its bending, tensile, compressive and torsional properties are far less than those of straight seam submerged arc welded pipes. At the same time, due to the limitation of welding position, the saddle and fish ridge welds are affected. Beautiful. In addition, during the construction process, the intersecting wire welds at the spiral welded parent pipe joints cut the spiral joints, resulting in large welding stress, thus greatly impairing the safety performance of the components. Therefore, the non-destructive testing strength of the spiral welded pipe welds should be strengthened. Ensure the quality of the welding, otherwise it is not suitable to use spiral submerged arc welded pipe in important steel structures.