According to production methods can be divided into two categories: seamless steel pipe and seamed steel pipe.
1. Seamless steel pipe
The wall thickness of a seamless steel pipe is relatively thick and its diameter 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.
2. High-frequency welded steel pipe(ERW)
The high-frequency welded pipe has a good pipe shape and a uniform wall thickness. The inner and outer burrs produced by welding are scraped by corresponding tools, and the quality of the weld seam is strictly controlled through non-destructive testing. The degree of automation is high and the production cost is low. However, the wall thickness is relatively thin, the pipe diameter is relatively small, the wall thickness is generally not more than 12mm, and the pipe diameter is generally not more than 610mm, and the steel structure is particularly suitable for manufacturing a pipe truss structure.
3. Straight seam submerged arc welded pipe(LSAW)
LSAW pipe adopts double-side submerged arc welding process. Welding under static conditions, the quality of the weld is high, the weld is short, and the probability of defects is very small. The steel pipe expands through the full-length, has a good pipe shape, and is precise in size. The wall thickness range of the steel pipe and the pipe diameter range are wide. The pipe diameter can reach 406-1829mm, the wall thickness can reach 6.0-60mm, and the degree of automation is high and seamless. Compared with steel pipes, the production cost is relatively low, and it is suitable for pillars for steel structures such as buildings, bridges, dams, and offshore platforms, ultra-long span building structures, and pole mast structures that require wind and seismic resistance.
4. Spiral submerged arc welded pipe(SSAW)
Spiral submerged arc welded pipe spiral weld distribution, long weld, especially in the dynamic conditions of welding, the weld is too late to leave the molding point of cooling, easy to produce welding hot cracks. The direction of the crack is parallel to the weld and is at a certain angle to the axis of the steel tube, typically between 30-70°. This angle is just in line with the shear failure angle, so its bending, tensile, compressive and torsional resistance is far inferior to the LSAW pipe. At the same time, due to the limitation of the welding position, the resulting saddle shape and ridge-shaped welding seam influence Beautiful. In addition, during the construction process, the intersecting line welds at the spiral welded parent pipe joints split the spiral joints and generate larger welding stress, which greatly weakens the safety performance of the components. Therefore, the non-destructive testing of the spiral welded pipe joints should be strengthened. Ensure welding quality, otherwise, spiral submerged arc welded pipe should not be used in important steel structure occasions.