Seamless steel pipe is perforated by the whole round steel, and the steel pipe with no weld on the surface is called seamless steel pipe. According to the production method, the seamless steel pipe can be divided into hot-rolled seamless steel pipe, cold-rolled seamless steel pipe, cold-drawn seamless steel pipe, extruded seamless steel pipe, pipe jacking and so on. According to the section shape, the seamless steel pipe is divided into two kinds of round and shaped, shaped pipe has square, oval, triangle, hexagonal, melon seed, star, fin tube and many complex shapes. The maximum diameter is 900mm and the minimum diameter is 4mm. According to different uses, there are thick wall seamless steel pipes and thin wall seamless steel pipes. Seamless steel pipe is mainly used for petroleum geological drilling pipe, petrochemical cracking pipe, boiler furnace pipe, bearing pipe and high-precision structural steel pipe for automobiles, tractors and aviation.
Generally used seamless steel pipe is made of 10, 20, 30, 35, 45 and other high-quality carbon bonded steel 16Mn, 5MnV and other low alloy structural steel or 40Cr, 30CrMnSi, 45Mn2, 40MnB and other bonded steel hot rolled or cold rolled. Seamless pipes made of low carbon steel such as 10 and 20 are mainly used for fluid transport pipelines. 45, 40Cr and other medium carbon steel seamless pipe to manufacture mechanical parts, such as cars, tractor parts. Generally use seamless steel pipe to ensure the strength and flattening test. Hot-rolled steel pipes are delivered in hot-rolled or heat-treated condition; Delivered cold rolled in heat-treated condition.
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General seamless steel pipe production process can be divided into two kinds of cold drawing and hot rolling, cold rolled seamless steel pipe production process is generally more complex than hot rolling, the tube billet first to carry out three roller continuous rolling, extrusion after sizing test, if the surface does not respond to the crack after the round tube to be cut by the cutting machine, cutting the growth of about one meter blank. Then enter the annealing process, annealing with acidic liquid pickling, pickling should pay attention to whether there is a large number of bubbles on the surface, if there is a large number of bubbles, indicating that the quality of the steel pipe can not meet the corresponding standards. The appearance of cold-rolled seamless steel pipe is shorter than that of hot-rolled seamless steel pipe, the wall thickness of cold-rolled seamless steel pipe is generally smaller than that of hot-rolled seamless steel pipe, but the surface looks brighter than that of thick-walled seamless steel pipe, the surface is not too rough, and the caliber is not too much burr.
