Introduction to Welded Pipe Technology
Welded pipes are categorized into two main types based on their forming process: spiral welded pipes and straight seam welded pipes. Additionally, they can be classified by the welding method used—high-frequency resistance welding (ERW) and submerged arc welding (SAW). Spiral welded pipes are typically produced using submerged arc welding technology. On the other hand, straight seam welded pipes can be either UOE (which refers to submerged arc welded pipes) or ERW (high-frequency resistance welded pipes). High-frequency resistance welded (ERW) steel pipes differ from those made using submerged arc welding in their welding process. Unlike SAW, which uses filler material, the ERW process does not require any additional welding materials. The weld is formed through a recrystallization process rather than melting, resulting in a weld that has the same chemical composition as the base metal. After welding, the pipe undergoes an annealing process to relieve cold working and welding stresses. As a result, ERW steel pipes generally exhibit superior overall mechanical properties compared to other types. Straight seam submerged arc welded pipes (UOE) use a post-weld cold expansion process to improve the dimensional accuracy of the pipe. This ensures better joint quality when connecting pipes, and it also helps reduce internal stresses. During the welding process, multiple wires (such as three or four) are often used, which leads to lower heat input and less impact on the heat-affected zone of the base metal. The first wire can help eliminate welding-induced stress, further enhancing the mechanical properties of the pipe. Compared to spiral welded pipes, straight seam submerged arc welded pipes have shorter welds, making them less prone to defects and damage. For high-pressure pipelines, the base material of straight-seam pipes can undergo 100% ultrasonic testing, meeting strict quality standards. However, despite their superior performance, UOE pipes tend to be more expensive, which may limit their use for budget-conscious users. Spiral welded pipes feature welds arranged in a helical pattern. The weld area includes the heat-affected zone, which usually has inferior mechanical properties compared to the rest of the pipe. Since the maximum internal stress in pressure pipes tends to occur along the axial direction, spiral welded pipes may be weaker in that region. However, the spiral weld orientation helps avoid this high-stress area, thereby improving the overall performance of the pipe. Another challenge with spiral welded pipes is the complexity of external corrosion protection due to the shape and height of the weld seams. There is also a risk of gaps forming between adjacent welds. To address this, some manufacturers now use horizontal winding techniques to apply three-layer PE or two-layer PE coatings, effectively solving the anti-corrosion issue for spiral welded pipes.Telescoping Truck Mounted Crane
Telescoping Truck Mounted Crane,Telescoping Boom Truck Mounted Crane,Cargo Crane Truck,Truck Cargo Crane
Hubei HuiLong Special Automobile co., LTD , https://www.huilongtruck.com