There are some detailed differences in pressure bearing capacity between straight seam submerged arc welded steel pipes and spiral submerged arc welded steel pipes:

Weld angle and stress distribution

Spiral submerged arc welded steel pipe: The weld seam is spiral shaped, and the helix angle is usually 50-75 degrees. When subjected to pressure, spiral welds allow stress to be more evenly distributed on all sides of the pipe, and the stress they bear is smaller than that of straight seams, generally 60% -85% of the main stress of straight seam welded pipes. This means that under the same pressure conditions, spiral submerged arc welded steel pipes can better disperse pressure, reduce local stress concentration, thereby enhancing the strength of the pipe and making its pressure bearing capacity relatively high.

Straight seam submerged arc welded steel pipe: The weld seam is a straight strip, and when subjected to pressure, there is a relatively high possibility of stress concentration at the weld seam. Especially when there is a T-shaped weld seam, the welding residual stress at the T-shaped weld seam is relatively high, and the weld metal is in a three-dimensional stress state, which increases the risk of cracking and may affect its pressure bearing capacity.

Production process impact

Spiral submerged arc welded steel pipe: using spiral forming and automatic welding technology, the steel plate deforms uniformly during the forming process, with low residual stress and less surface scratches. Some spiral submerged arc welded steel pipes undergo overall mechanical diameter expansion, which can effectively improve the dimensional accuracy of the steel pipe and improve the distribution of internal stress, avoiding damage caused by stress corrosion. This is beneficial for on-site welding construction and also helps to improve the pressure bearing capacity.

Straight seam submerged arc welded steel pipe: using forming processes such as JCOE, a large number of T-shaped welds are inevitably generated during the production process. The welding residual stress at these T-shaped welds is relatively high. Under pressure, the weld metal is in a complex stress state, which increases the possibility of cracking and has a certain negative impact on the pressure bearing capacity. However, when welding straight seam submerged arc welded steel pipes, one weld seam is usually used (two straight welds are allowed when the diameter is greater than 914.4mm), and the length of the weld seam is relatively short. With good welding quality control, it can also ensure a certain pressure bearing capacity.

Wall thickness and pipe diameter range

Spiral submerged arc welded steel pipe: The production diameter can reach 3620mm, which has advantages in the production of large diameter steel pipes. But generally, the wall thickness does not exceed 26mm, and under high-pressure and large-diameter conditions, its pressure bearing capacity may be limited by the wall thickness. However, due to the characteristics of spiral welds, under the same working pressure, the wall thickness of spiral welded pipes with the same diameter can be reduced compared to straight seam welded pipes, and the material utilization rate is higher.

Straight seam submerged arc welded steel pipe: The production diameter is generally 426-1920mm, and the wall thickness can reach 60mm, which has advantages in producing thick walled steel pipes. By increasing the wall thickness, straight seam submerged arc welded steel pipes can improve their pressure bearing capacity, making them widely used in applications with high pressure requirements and relatively small pipe diameters.

Material and Strength

Spiral submerged arc welded steel pipe: Due to the rolling direction of the coil not being perpendicular to the axis of the steel pipe, its material has better crack resistance than straight seam steel pipe. For steel pipes of the same material and specification, the strength of spiral submerged arc welded steel pipes is generally higher than that of straight seam submerged arc welded steel pipes, which is more conducive to withstanding pressure. For example, in pipelines transporting high-pressure fluids such as oil and natural gas, spiral submerged arc welded steel pipes can better adapt to complex working conditions.

Straight seam submerged arc welded steel pipe: can be made of various materials, such as Q235, Q345, etc. Although the strength of the material itself can meet certain pressure requirements, its overall strength and crack resistance are slightly inferior to spiral submerged arc welded steel pipes due to factors such as production processes and weld characteristics. When selecting straight seam submerged arc welded steel pipes, it is necessary to choose the material and wall thickness reasonably according to the specific usage environment and pressure requirements to ensure that their pressure bearing capacity meets the engineering requirements.

Overall, spiral submerged arc welded steel pipes usually have certain advantages in terms of pressure bearing capacity, but straight seam submerged arc welded steel pipes can also meet many engineering applications with high pressure bearing capacity requirements through reasonable design, manufacturing, and quality control. In practical engineering, it is necessary to comprehensively consider factors such as specific engineering requirements, working pressure, pipe diameter, and environment to select the appropriate type of steel pipe.