Seamless steel pipes are a kind of economical steel that plays a very important role in the national economy. They are widely used in various industries including petroleum, chemical, boiler, power station, shipbuilding, machinery manufacturing, automobile, aviation, aerospace, energy, geology, construction, and military based on different production methods. Seamless steel pipes can be classified into hot-rolled pipes, cold-rolled pipes, cold-drawn pipes, and extruded pipes.
Hot-rolled seamless steel pipes are generally produced on automatic pipe mills. After inspecting and removing surface defects, the solid pipe blanks are cut into required lengths, then heated in furnaces and pierced on piercing machines using the end faces of the blank as the center. The blank keeps rotating and moving forward during the piercing process. The inside of the blank gradually forms a cavity, called a rough tube, because of the actions of the rollers and plugs. Then, the rough tubes are conveyed to automatic pipe mills for further rolling. Finally, the wall thickness is adjusted by a whole machine, and the diameter is determined by a sizing machine to meet the standard requirements. Using a continuous pipe mill to produce hot-rolled seamless steel pipes is an advanced production method.
Combination of cold-rolling, cold-drawing, or both methods should be adopted. Cold-rolling is usually carried out on two-roll mills. Seamless steel pipes are rolled in a ring-shaped hole consisting of a variable cross-section circular groove and a fixed taper plug. Cold-drawing is usually performed on single-chain or double-chain cold-drawing machines.
Extrusion is the method of placing heated pipe blanks in a closed extrusion cylinder, and piercing rods and extrusion rods move together to extrude the extrusion piece from a smaller die hole. This method can produce smaller diameter steel pipes.
Preparation and inspection of pipe blanks → heating of pipe blanks → piercing → rolling → reheating of billets → sizing (reducing) → heat treatment → straightening of finished pipes → completion → inspection (non-destructive, physical and chemical, and hydrostatic tests) → storage.
Blank preparation → pickling and lubrication → cold rolling (drawing) → heat treatment → straightening → completion → observation.
Above are the main production methods of seamless steel pipes. The seamless steel pipe is a circular, square or rectangular steel pipe with a hollow cross-section and no seams around its circumference. It is made from steel ingots or solid pipe blanks after piercing and being hot-rolled, cold-rolled, or cold-drawn. The seamless steel pipe has a hollow section and is widely used as a pipeline for conveying fluids. Compared with solid steel (such as round steel), steel pipes have the same bending and torsional strength and are lighter in weight. It is an economical steel and widely used for manufacturing structural components and machinery parts such as steel supports for drilling rigs.