Comparison between straight seam steel pipe and spiral steel pipe

Comparison between straight seam steel pipe and spiral steel pipe

Straight seam steel pipe and spiral steel pipe are two common types of welded steel pipe, they are different in the production process, structural characteristics, application fields and so on. The following is a comparison of the two steel pipes:

1. Production process
The production process of straight seam steel pipe is relatively simple. The main production processes are high frequency welded straight seam steel pipe and submerged arc welded straight seam steel pipe. Straight seam steel pipe has high production efficiency and low cost. It can be produced quickly and in large quantities.

The strength of spiral steel pipe is usually higher than that of straight steel pipe. The main production process is submerged arc welding. Spiral steel pipes can be welded with different diameters from billets of the same width, and can also be welded with narrower billets of larger diameters. However, compared with the straight steel pipe of the same length, the welding length of the spiral steel pipe is increased by 30% and 100%, respectively, and the production speed is slow. Therefore, large diameter steel pipes are mostly used spiral welding, and small diameter steel pipes are mostly used straight seam welding.

In the industrial production of large straight seam steel pipe, the T-shape welding technology is mostly used, that is, a small number of straight seam steel pipe butt connection to meet the required length of the project. The defects of T-shaped straight seam steel pipe will be greatly increased, and the welding residual stress of T-shaped weld is larger. Weld metal is usually under triaxial stress, which increases the likelihood of cracking.
In addition, according to the submerged arc welding technical regulations, each weld should be arc striking and extinguishing treatment. However, in the ring welding, not every steel pipe can meet this condition, so there may be more welding defects in the arc extinguishing process.

2. Weld characteristics
Straight seam steel pipe: the weld of straight seam steel pipe extends axially, generally there is only one straight seam weld, and a few cases will use the welding method of double-sided submerged arc welding, which will produce two straight welds. Its advantage is that the weld is concentrated and the quality is easy to control. The disadvantage is that because the weld is in a straight line, the pressure bearing capacity is low, which is suitable for small and medium caliber pipelines.
Spiral steel pipe: the weld is spiral, and the weld is long. The advantages are uniform distribution of welds, increased pressure capacity, suitable for pipelines with large diameters. The disadvantage is that the weld is longer, and the cost of detection and maintenance is high.

3. Performance comparison
Straight seam steel pipe: The weld seam of straight seam steel pipe is distributed along the longitudinal, and the bearing capacity is weak in the horizontal aspect, and it is easy to be squeezed by external force when using long distance. But it performs well in small caliber and low pressure environments.
Spiral steel pipe: The weld of spiral steel pipe is evenly distributed on the pipe body, which enhances its carrying capacity, helps to disperse stress, and is suitable for large caliber and high pressure occasions. The disadvantage is that there are many welds, which may produce defects.

The development trend of pipeline is large diameter and high strength. With the increase of steel pipe diameter and steel grade, the ductile fracture tip tends to expand steadily. Although the grade of spiral steel pipe and straight seam steel pipe is the same, the spiral steel pipe has higher impact toughness.

Read more: The difference between straight steel pipe and seamless steel pipe