In the 30s of 20th century, with the quick development of high-quality strip rolling production and improvement of welding and checking technologies; the constant increase of welding quality, the categories of welded steel pipe become increasingly more, and replace the seamless pipe in more and more areas. Welded steel pipe has lower cost and higher production efficiency.
The categories of welded steel pipe: According to the welding ways, it can be classified into arc welded pipe, high frequency or low frequency resistance welded pipe, gas welded pipe, furnace welded pipe etc. The electric welded steel pipe is mainly used for oil drilling and mechanical manufacturing industries etc. The furnace welded pipe is mainly applied into water gas pipe, according to weld shape, welded steel pipe can be classified into straight welded pipe and spiral welded pipe. The straight welded pipe has its own advantages: simple production techniques, higher production efficiency, lower cost and quicker development. The spiral welded pipe also has own advantages: generally speaking, it has stronger intensity, which can use narrower blank materials to produce welded pipe with bigger diameter, also produce welded pipes with different diameters by using blank materials with the same width. But compared to the straight welded pipe with same length, its welding seam should add 30%-1005m but the production efficiency becomes lower.
Spiral welded steel pipe is classified into automatic submerged arc and high frequency welded steel pipe. According to application, welded steel pipe is divided into general, zinc, oxygen blowing, electric line welded pipe as well as deep well pump, automobile-used pipe, spiral welded pipe etc. The general welded pipe is used for transporting low-pressure fluids. The zinc welded steel pipe: in order to increase the corrosion resistance property, the general steel pipe (black steel pipe) will be plated zinc. The zinc welded pipe includes hot-galvanize and electric steel zinc, the former has thick zinc; the latter has low-cost. Oxygen blowing welded steel pipe: is used for steel-making and oxygen blowing pipe, general has small welding caliber. Some need to be aluminum in order to prevent corrosion.
Spiral welded steel pipe: twists low-carbon structure or low-alloy structure into pipe billets in accordance with certain angles of spiral line, then produces the steel pipe with big diameter by using narrower band steel. Spiral welded steel pipe is mainly used for the transporting pipe line for oil and natural gas, whose specification is presented by diameter thickness. Transformer pipe: is used for producing transformer radiator. It adopts common carbon steel, and also has a requirement for steel pipe bending. Irregular steel pipe: is square pipe, triangle pipe etc that is made of common carbon structure and 16Mn steel belts, which are mainly applied into agricultural components and steel windows and doors.