What is the difference between a welded steel pipe and a welded spiral steel pipe

Welded steel pipe refers to a steel pipe with seams on the surface that is formed by bending steel strips or steel plates into round, square, and other shapes and then welding them. The billet used for welded steel pipes is steel plate or strip steel. Since the 1930s, with the rapid development of continuous rolling production of high-quality strip steel and the advancement of welding and inspection technology, the quality of welds has been continuously improved, the variety and specifications of welded steel pipes have increased, and they have replaced seamless steel pipes in more and more fields. Welded steel pipes have lower costs and higher production efficiency than seamless steel pipes.

Steel pipes are divided into seamless and welded pipes. Welded pipes are divided into straight seam steel pipes and spiral steel pipes. Straight seam welded pipes are divided into ERW (high-frequency resistance welding) and LSAW (straight seam submerged arc welding). The welding process of spiral steel pipes is also submerged arc welding (SSAW for short). The difference between LSAW and ERW is the weld form, and the difference between LSAW and ERW is the difference in the welding process. Submerged arc welding (SAW) requires the addition of a medium (welding wire, flux), but ERW does not require it. ERW is melted by medium-frequency heating. Steel pipes can be divided into two categories according to the production method: seamless steel pipes and welded steel pipes. Seamless steel pipes can be divided into hot-rolled seamless steel pipes, cold-drawn steel pipes, precision steel pipes, hot-expanded steel pipes, cold-spun steel pipes, and extruded steel pipes according to the production method. Seamless steel pipes are made of high-quality carbon steel or alloy steel and are divided into hot-rolled and cold-rolled (drawn).

The production process of straight-seam welded steel pipes is simple, with high production efficiency, low cost, and rapid development. The strength of spiral welded steel pipes is generally higher than that of straight-seam welded steel pipes. Narrower billets can be used to produce welded steel pipes with larger steel pipe diameters, and billets of the same width can also be used to produce welded steel pipes with different steel pipe diameters. However, compared with straight-seam steel pipes of the same length, the weld length increases by 30~100%, and the production speed is lower. Therefore, smaller-diameter welded steel pipes are mostly welded by straight-seam welding, while large-diameter welded steel pipes are mostly welded by spiral welding.