1. Seamless steel pipe is a long strip of steel with no seams around it and has a hollow cross-section. It is widely used as a steel pipeline for transporting fluids. Compared with solid steel, it is lighter in weight when the bending and torsion strength are the same. An economical cross-section steel that is widely used in the manufacture of structural and mechanical parts, such as automobile drive shafts, oil drill pipes, bicycle frames, and steel scaffolding used in construction.

2. Welded steel pipe is a steel pipe made by welding steel plates or steel strips after being curled and formed. The production process of welded steel pipes is simple, with many varieties and specifications, less equipment investment, and high production efficiency, but its general strength is lower than that of seamless steel pipes. 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 continues to improve, the varieties and specifications of welded steel pipes are increasing day by day, and they have replaced seamless steel pipes in more and more fields. Welded steel pipes are divided into spiral welded steel pipes and straight seam welded steel pipes according to the form of the weld. ​

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