The production process of straight seam steel pipes is relatively simple, with the main production processes being high-frequency welded straight seam steel pipes and submerged arc welded straight seam steel pipes. Straight seam steel pipes have high production efficiency, low cost, and rapid development. The strength of spiral steel pipes is usually higher than that of straight seam steel pipes. The main production process is submerged arc welding. Spiral steel pipes can produce welded pipes of different diameters with steel billets of the same width, or welded pipes with larger diameters can be produced from narrow billets. However, compared with straight seam steel pipes of the same length, the welding length has increased by 30% and 100% respectively, resulting in a lower production speed. Therefore, large-diameter steel pipes are mostly welded through spiral welding, while small-diameter steel pipes are mostly welded through straight seam welding. When producing large-diameter straight seam steel pipes in industry, T-shaped welding technology is used, which involves docking and connecting a small portion of straight seam steel pipes to meet the required length of the project. The defects of T-shaped straight seam steel pipes will greatly increase, and the welding residual stress of T-shaped welds is relatively high. Welding metal is usually in a triaxial stress state, which increases the possibility of cracking.

In terms of welding technology, the welding methods for spiral steel pipes and straight seam steel pipes are the same, but inevitably there will be a large number of T-shaped welds, and the welding residual stress of T-shaped welds is very high. Therefore, the possibility of welding defects is also high. After improvement, the weld metal is usually in a triaxial stress state, which increases the possibility of cracking.

In addition, according to the technical regulations of submerged arc welding, each weld seam should undergo arc ignition and extinguishing treatment, but each steel pipe cannot meet this condition during circumferential seam welding, so more welding defects may occur during the extinguishing process.

When a pipeline is subjected to internal pressure, two main stresses are usually generated on the pipeline wall, namely radial stress and axial stress. The comprehensive stress at the weld seam, where α It is the spiral angle of the weld seam of the spiral steel pipe.

The comprehensive stress at the spiral weld is the main stress of the straight seam steel pipe. Under the same working pressure, the wall thickness of spiral steel pipes with the same diameter is smaller than that of straight seam steel pipes.

When parallel defects appear near the spiral weld, the expansion risk of the spiral weld is lower than that of the straight weld due to the smaller force of the spiral weld. Due to radial stress being the maximum stress on the steel pipe, the weld seam bears the maximum load in the vertical stress direction. The load borne by the joint is the highest, the load borne by the circumferential weld is the lowest, and the load borne by the spiral weld is between the two.

The development trend of pipelines is large diameter and high strength. With the increase of steel pipe diameter and grade, the trend of stable expansion at the ductile fracture tip is greater. Although spiral steel pipes and straight seam steel pipes have the same grade, spiral steel pipes have higher impact toughness.