Welded steel pipes are made by flattening steel coils and then welding them through a welding machine. There are several types of welding, such as straight seam welding and spiral welding. The diameter of the produced pipe is large.

The seamless steel pipe is heated by heating the tube blank and using another barrel rod to thermally expand the tube blank. The tube blank is about 2 meters long and reaches a length of 5.8 meters through thermal expansion. Another method is graphite expansion, which simply uses alloy rods for cold expansion.