Spiral welded pipe and straight seam welded pipe have different technical characteristics and production processes, resulting in significant differences and distinctions in their manufacturing. They offer different functions and applications, and demonstrate different value in use. The following is a comparison of the technical characteristics of spiral welded pipe and straight seam welded pipe:
Below, let’s briefly compare the technical characteristics of spiral welded pipe and straight seam welded pipe:
· First, the difference in the welding process.
In terms of the welding process, spiral welded pipe and straight seam steel pipe use the same welding method. However, straight seam welded pipe inevitably has many T-welds, which greatly increases the probability of welding defects. Furthermore, the residual stress at the T-welds is high, and the weld metal is often subjected to triaxial stress, increasing the likelihood of cracking. Furthermore, according to the submerged arc welding process specifications, each weld must have an arc start and an arc extinction point. However, this requirement cannot be met when welding the circumferential seam of straight seam welded pipe, resulting in a higher incidence of welding defects at the arc extinction point. Therefore, the quality of spiral welded pipes produced is guaranteed, ensuring they are free of defects such as cracks.
· Strength Characteristics of Spiral Welded and Straight Seam Welded Pipes
When subjected to internal pressure, pipes typically generate two primary stresses on the pipe wall: radial stress δY and axial stress δX. The resultant stress at the weld seam δ=δY(l/4sin²α+cos²α)1/2, where α is the helix angle of the spiral welded pipe weld. The helix angle of the spiral welded pipe weld is generally 50-75 degrees, so the resultant stress at the spiral weld seam is 60-85% of the principal stress of the straight seam welded pipe. Under the same operating pressure, spiral welded pipe of the same diameter can have a thinner wall than straight seam welded pipe.
· Metallurgical Properties of Spiral Welded and Straight Seam Welded Pipe Materials
Straight seam submerged arc welded pipes are produced from steel plate, while spiral welded pipes are produced from hot-rolled coil. The hot strip mill rolling process offers a range of advantages, enabling metallurgical processes to produce high-quality pipeline steel. For example, a water cooling system on the output gantry accelerates cooling, allowing the use of low-alloy compositions to achieve exceptional strength grades and low-temperature toughness, thereby improving the steel’s weldability. However, this system is rarely found in steel plate mills. The alloy content (carbon equivalent) of the coiled steel is often lower than that of similar-grade steel plate, which also improves the weldability of spiral welded pipe.
Furthermore, because the coiling direction of spiral welded pipe is not perpendicular to the pipe axis (the clamping angle is determined by the pipe’s helix angle), while the steel plate is rolled perpendicular to the pipe axis for straight seam steel pipe, spiral welded pipe exhibits superior crack resistance compared to straight seam steel pipe.
This article systematically compares spiral welded pipe and straight seam steel pipe in terms of welding process, metallurgical properties, and strength characteristics, focusing on the differences and key distinctions between the two. The welding process and methods, strength properties, metallurgical properties, and processes for each pipe type are detailed.
Post time: Aug-27-2025