Large-diameter spiral steel pipes and large-diameter straight seam steel pipes are both types of welded steel pipes. They play an important role in national production and life. Large-diameter spiral steel pipes and large-diameter straight seam steel pipes have many differences due to different production processes.
1. In terms of the welding process: the welding methods of large-diameter spiral pipes and large-diameter straight-seam pipes are the same. Large-diameter straight-seam pipes have T-shaped welds. The welding residual stress at the T-shaped welds is relatively large, and the weld metal is often in a three-dimensional stress state. , increasing the possibility of cracks. The strength of spiral steel pipes is generally higher than that of straight seam welded pipes. The main production process is submerged arc welding. Spiral steel pipes can use billets of the same width to produce welded pipes with different diameters, and narrow billets can also be used to produce welded pipes with larger diameters.
2. The helix angle of large-diameter spiral steel pipe welds is generally degrees, so the resultant stress at the spiral weld is the principal stress. Under the same working pressure, the wall thickness of spiral steel pipes with the same diameter can be smaller than that of straight seam welded pipes.
3. Toughness and fatigue strength: The development trend of pipelines is large diameter and high strength. As the diameter of the steel pipe increases and the grade of steel used increases, the tendency of the ductile fracture tip to expand steadily increases. Although spiral steel pipes and straight seam welded pipes are of the same grade, spiral steel pipes have higher impact toughness.
4. Compared with straight seam steel pipes of the same length, the weld length of spiral steel pipes is increased by 30~100%, and the production speed is lower. Therefore, smaller-diameter welded pipes mostly use straight seam welding, while large-diameter steel pipes mostly use spiral welding.
Post time: Apr-07-2024