Seamless steel pipe is a kind of round, square and rectangular steel with hollow section and no joint around it. Seamless steel tube is made of steel ingot or solid billet through perforation and then hot-rolled, cold-rolled or cold-drawn. Seamless steel pipe has hollow section, which is widely used as pipeline for conveying fluid. Compared with solid steel such as round steel, steel pipe has lighter weight when its bending and torsion strength is the same. It is an economic section steel, and is widely used in manufacturing structural parts and mechanical parts, such as steel scaffolding for oil drills.

　　Seamless steel tube production has a history of nearly 100 years. The German Manisman Brothers first invented the two-roll cross-rolling piercing mill in 1885, and the periodic pipe mill in 1891. In 1903, the Swiss R.C. Stiefel invented the automatic pipe mill (also known as the top pipe mill). Later, various extension machines such as continuous pipe mill and pipe jacking machine appeared, which began to form modern seamless pipe workers. Industry. In the 1930s, three-roll pipe mill, extruder and periodic cold rolling mill were used to improve the quality of steel tubes. In the 1960s, with the improvement of continuous rolling mill and the emergence of three-roll piercing mill, especially the successful application of stretch reducing mill and continuous casting slab, the production efficiency was improved and the competitiveness between seamless pipe and welded pipe was enhanced. In the 1970s, seamless pipes and welded pipes were going hand in hand, and the world steel pipe production increased at a rate of more than 5% per year. Since 1953, China has attached great importance to the development of seamless steel tube industry, and has initially formed a production system for rolling various large, medium and small tubes. Copper tubes are also generally made by cross-rolling perforation of ingot billets, rolling of tube mills and stretching of coils.

　　Use and classification of seamless steel pipe: seamless steel pipe is a kind of economic section steel, which plays an important role in national economy. It is widely used in petroleum, chemical industry, boiler, power station, ship, machinery manufacturing, automobile, aviation, aerospace, energy, geology, construction and military industries.

　　Classification:

　　(1) According to the shape of the cross-section, it can be divided into circular cross-section pipe and special-shaped cross-section pipe.

　　According to material quality: carbon steel pipe, alloy steel pipe, stainless steel pipe, composite pipe

　　(3) According to connection mode, threaded connection pipe and welded pipe

　　(4) According to the mode of production: hot-rolled (extruded, top-rolled, expanded) and cold-rolled (drawn) pipes

　　(5) By use: boiler pipe, oil well pipe, pipeline pipe, structural pipe, fertilizer pipe...