Welded steel pipe, also known as welded pipe, is a steel pipe welded with steel plate or strip steel after crimping. Generally, the length is 6m. Welded steel pipe has the advantages of simple production process, high production efficiency, many varieties and specifications and less equipment investment, but its general strength is lower than that of seamless steel pipe. Welded pipes with large or thick diameter are generally made of steel blank directly, while small welded pipes and thin-walled welded pipes only need to be welded directly through steel strip.