Seamless steel pipes are very versatile. Seamless steel pipes for general purposes are rolled by ordinary carbon structural steel, low-alloy structural steel or alloy structural steel, with a large output, and are mainly used as pipelines or structural parts for transporting fluids. According to different uses, it is supplied in three categories: a. Supply according to chemical composition and mechanical properties; b. Supply according to mechanical properties; C. Supply according to water pressure test. Steel pipes supplied according to class A and B, if used to withstand liquid motion, should also be subjected to hydrostatic test. 3. Seamless pipes for special purposes include seamless pipes for boilers, seamless steel pipes for geology and seamless pipes for petroleum.

Welded steel pipes, also known as welded pipes, are steel pipes made of steel pipes and steel pipes made of steel plates or steel strips after being curled and formed. The production process of welded steel pipe is simple, the production efficiency is high, there are many varieties and specifications, and the equipment is less, but the general strength is lower than that of seamless steel pipe. Since the 30s of the 20th century, with the rapid development of high-quality strip continuous rolling production and the progress of welding and inspection technology, the quality of welds has been continuously improved, and the varieties and specifications of welded steel pipes have increased day by day, and seamless steel pipes have been replaced in more and more fields.

Welded steel pipes are divided into longitudinal welded pipes and spiral welded pipes according to the form of welds. The production process of longitudinal welded pipe is simple, the production efficiency is high, the cost is low, and the development is fast. The strength of spiral welded pipe is generally higher than that of longitudinal welded pipe, and the welded pipe with a larger diameter can be produced with a narrower blank, and the welded pipe with different diameters can also be produced with a blank of the same width. However, compared with the longitudinal seam pipe of the same length, the weld length is increased by 30~100%, and the rental production speed is lower. Therefore, most of the welded pipes with smaller diameters are welded with straight seams, and most of the welded pipes with large diameters are welded with spirals.