According to methods of steel manufacturing, steel pipe is divided into two types: welding steel pipe and seamless steel pipe. Seamless steel pipe is made from high-quality carbon steel or alloy steel, which includes hot-rolled, cold-rolled pipe. Welded steel pipe is formed by rolled steel with the shape of a tube, which is welded together in the seam or spiral seam. As per manufacturing methods, it can be divided into welding steel pipe for transportation of low-pressure fluid, seam welding spiral steel pipe, welded steel pipe etc. Seamless steel pipes can be used for a variety of liquids, and gas pipelines, while welded pipe can be used for water pipes, gas pipes, heating pipes and so on.