Industrial developed countries, such as the United States, Japan, Germany and so on, have a large number of modern hot rolling pipe equipment, mainly automatic pipe rolling machine and periodic pipe rolling machine, the production of steel pipe accounted for 92% of the world's hot rolling pipe output, the growth rate of steel pipe 7.5%. They produce about 15 per cent of the world's steel in hot-rolled tubes.
In recent years, billet continuous casting has made great progress and gradually replaced the rolled billet. So that the metal yield rate increased by 10%-15%, energy costs save more than 40%, cost greatly reduced. Since the 1980s, the conical roll penetration system, limited movement mandrel continuous rolling pipe sets and other efficient advanced rolling equipment have been widely adopted. The limited movement mandrel continuous rolling machine can produce steel tubes with diameters up to 426mm and lengths up to 50m. High production efficiency, the maximum output of single machine can reach 800,000 to 1,000,000 T /a; The product quality is good, the outer diameter tolerance can reach ±0.2%-0.4%, the wall thickness deviation is within the range of ±03%-6.5%. On the basis of the two - high limited moving mandrel continuous rolling machine, a three - high adjustable limited moving mandrel continuous rolling machine was developed abroad.
In recent years, the welded pipe output of each main steel-producing country exceeds seamless pipe output, such as Japan welded pipe in 1973 has accounted for 80% of steel pipe output. With the development of long distance industrial transportation routes, the proportion of large diameter welded pipe is increasing. In the 1970s, the maximum outer diameter of foreign U-O forming welded pipe was increased to 1626mm, the o-type press was up to 6000MN, and the maximum wall thickness was increased to 40mm. The annual production capacity of U-O forming pipe welding machine is 1.1 million tons.
The spiral welding pipe adopts a forming machine to spot weld the strip immediately after it is formed, and then it is sent to several welding machines for double-sided welding after it is cut to a certain size, so that a forming machine is used for several.
Due to the increasing demand for precision, thin wall and high strength special steel pipe, the production of cold rolled and cold drawn steel pipe develops rapidly.
There are periodic, multi - roll, vertical, planetary and continuous pipe rolling machines. The periodic cold tube rolling machine is the most widely used. Cold drawing is the main method of producing precision steel pipe. There are three kinds of cold drawing machines: pendulum type, rotary type and drum type. Drum type tube drawing machine occupies a small area, drawing speed is high, is being popularized and applied.
