The LSAW steel pipe adopts double-sided submerged arc welding welding technology, welded under static conditions, the weld quality is high, the weld seam is short, and the probability of defects is small. The steel pipe is expanded through the full length, the pipe shape is good, the size is accurate, the steel pipe wall thickness range and the pipe diameter range are wide, the pipe diameter range can reach 400-1829mm, the wall thickness range can reach 6.0-60mm, the automation degree is high, and seamless Compared with steel pipes, the production cost is lower, and it is suitable for steel structure bearing columns such as buildings, bridges, dams, and offshore platforms, ultra-long span building structures, and electric pole tower mast structures that require wind and earthquake resistance.
The welds of spiral submerged arc welded pipes are distributed in a spiral line, and the welds are long, especially when welding under dynamic conditions, the welds leave the forming point before they can cool down, and welding heat cracks are prone to occur. The direction of the crack is parallel to the weld seam and forms a certain angle with the axis of the steel pipe, generally between 30-70°. This angle is exactly the same as the shear failure angle, so its bending, tensile, compression and torsion resistance are far inferior to LSAW pipes. At the same time, due to the limitation of the welding position, the saddle-shaped and fish-ridged welds are affected. Beautiful. In addition, during the construction process, the intersecting line welds at the joints of the spiral welded mother pipe split the spiral seams, resulting in greater welding stress, which greatly weakens the safety performance of the components. Therefore, the non-destructive testing of the spiral welded pipe welds should be strengthened. Ensure the welding quality, otherwise the spiral submerged arc welded pipe should not be used in important steel structure occasions.
The strength of spiral steel pipes(ssaw) is generally higher than that of longitudinally welded pipes. A narrower blank can be used to produce welded pipes with larger pipe diameters, and a billet with the same width can also be used to produce welded pipes with different pipe diameters. But compared with the straight seam pipe of the same length, the weld length is increased by 30-100%, and the production speed is lower. Therefore, most of the smaller diameter welded pipes adopt straight seam welding, and the large diameter welded pipes mostly adopt spiral welding. Spiral steel pipes are mainly used in water supply engineering, petrochemical industry, chemical industry, electric power industry, agricultural irrigation, and urban construction.
In summary, we can see that the two different ways of welded pipes have their own characteristics and have different advantages according to different applications.
