The production process of straight seam steel pipes is relatively simple, mainly involving high-frequency welded straight seam pipes and submerged arc welded straight seam pipes. Straight seam steel pipes have high production efficiency, low cost, and rapid development. Spiral welded steel pipes generally have higher strength than straight seam steel pipes. The main production process is submerged arc welding. Spiral welded steel pipes can be produced from steel billets of the same width but with different diameters, and can also be produced from narrow steel billets with larger diameters. However, compared to straight seam steel pipes of the same length, the welding length increases by 30% and 100%, respectively, resulting in lower production speeds. Therefore, large-diameter steel pipes are mostly welded using spiral welding, while small-diameter steel pipes are mostly welded using straight seam welding. In industrial production of large-diameter straight seam steel pipes, T-welding technology is used, which involves butt-jointing a small portion of straight seam steel pipe to meet the required length for a project. T-welding straight seam steel pipes has significantly increased defects, and the residual stress in the T-weld is relatively large. Weld metal is typically under triaxial stress, which increases the likelihood of cracking.

Regarding welding technology, the welding methods for spiral welded steel pipes and straight seam welded steel pipes are the same, but a large number of T-welds are unavoidable, and the residual stress in these T-welds is very high. Therefore, the possibility of welding defects is also high. After improvement, the weld metal is typically under triaxial stress, which further increases the likelihood of cracking.

Furthermore, according to the technical specifications for submerged arc welding, each weld pass should undergo arc initiation and extinguishing treatments. However, this condition cannot be met for every steel pipe when welding circumferential seams, thus potentially leading to more welding defects during the arc extinguishing process.

When a pipeline is subjected to internal pressure, two main stresses are typically generated on the pipe wall: radial stress and axial stress. The combined stress at the weld is denoted by α, where α is the helix angle of the spiral weld in the spiral welded steel pipe.

The combined stress at the spiral weld is the principal stress of the straight seam welded steel pipe. Under the same working pressure, the wall thickness of a spiral welded steel pipe of the same diameter is less than that of a straight seam welded steel pipe.

When parallel defects occur near the spiral weld of a spiral welded steel pipe, the expansion risk of the spiral weld is lower than that of a straight weld due to the smaller force exerted by the weld. Since radial stress is the maximum stress on the steel pipe, the weld bears the maximum load in the direction perpendicular to the stress. The joint bears the largest load, the circumferential weld bears the smallest load, and the spiral weld bears a load in between.

The development trend of pipelines is towards larger diameters and higher strength. With the increase in pipe diameter and steel grade, the tendency for stable expansion at the ductile fracture tip is greater. Although spiral and straight seam steel pipes have the same grade, spiral steel pipes exhibit higher impact toughness.