Difference between large-diameter SSAW steel pipe and LSAW steel pipe

Large-diameter spiral steel pipes and large-diameter straight seam steel pipes are both crucial types of welded steel pipes, playing a significant role in various national industries and everyday life. Despite their similarities, these two types of pipes differ notably due to their distinct production processes. Below, we will discuss these differences in detail.

Welding Process:

Similarity: Both types use similar welding methods, primarily submerged arc welding.

Differences:

Straight Seam Pipes: Feature T-shaped welds, which result in higher residual stress and a three-dimensional stress state in the weld metal, increasing the likelihood of cracks.

Spiral Steel Pipes: Generally have higher strength and can produce welded pipes of different diameters using billets of the same width. Narrow billets can be used to produce larger diameter pipes.

Helix Angle and Stress:

Spiral Steel Pipes: The welds have a helix angle that typically results in the principal stress being the resultant stress. For the same working pressure, the wall thickness of spiral steel pipes can be thinner than that of straight seam welded pipes of the same diameter.

Toughness and Fatigue Strength:

As pipeline diameters and steel grades increase, the tendency for ductile fracture tips to expand steadily also increases.

Spiral Steel Pipes: Tend to have higher impact toughness compared to straight seam welded pipes of the same grade, making them more suitable for applications requiring greater durability.

Weld Length and Production Speed:

Straight Seam Steel Pipes: For pipes of the same length, the weld length of spiral steel pipes is 30-100% longer, resulting in a lower production speed.

Spiral Steel Pipes: Due to the increased weld length and slower production speed, smaller diameter welded pipes often use straight seam welding, whereas larger diameter steel pipes predominantly use spiral welding.

In summary, while both large-diameter spiral steel pipes and large-diameter straight seam steel pipes share some welding techniques, they differ significantly in aspects such as stress distribution, toughness, weld length, and production speed. These differences influence their specific applications in various industries.