Since the 1930s, with the rapid development of high-quality strip steel continuous rolling production and the progress of welding and inspection technology, the quality of the weld seam is constantly improved, the variety of specifications of welded steel pipe is increasing, and in more and more areas to replace the seamless steel pipe. Welded steel pipe is divided into straight seam welded pipe and spiral welded pipe according to the form of weld seam. Classification by production method: process classification - arc welded pipe, resistance welded pipe, (high-frequency, low-frequency) gas welded pipe, furnace welded pipe.
Smaller diameter welded pipe using straight seam welding, large diameter welded pipe is more spiral welding; according to the shape of the end of the pipe is divided into round welded pipe and shaped (square, rectangular, etc.) welded pipe; according to the material and use of different types of welded steel pipe for fluid transport in mines, galvanized welded steel pipe for low-pressure fluid transport, welded steel pipe for belt conveyor rolls, and so on. According to the current national standard in the specification size table, according to the outer diameter * wall thickness from small to large order.