Welded steel pipe is a steel pipe made by rolling a steel plate into a tube shape and then welding it. During the welding process, the edges of the steel plates are heated to a molten state and then joined together through pressure or filling with welding material to form a continuous tubular structure. There will be welded joints inside the welded steel pipe, which may cause some welding defects. Therefore, in some specific projects, the strength and pressure resistance of the welded steel pipe may be relatively low. Welded steel pipes are usually used in general engineering structures, construction, transporting liquids, gases and other fields.

Seamless steel pipe is a steel pipe manufactured through an integral heating and perforation process. It has a uniform internal structure and no welded joints. This kind of steel pipe has the characteristics of high strength and good pressure resistance. It is usually used under high pressure, high temperature and high strength working conditions, such as petroleum, chemical industry, aerospace and other fields. The manufacturing process of seamless steel pipes is relatively complex, so the production cost is high, but it has irreplaceable advantages in some special projects.