Cold drawn seamless steel pipe

　　Cold drawn seamless steel pipes include ordinary steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes and other steel pipes, as well as carbon thin-walled steel pipes, alloy thin-walled steel pipes, stainless thin-walled steel pipes and special-shaped steel pipes. Cold rolling shall be delivered in heat treatment state.

　　Production process of cold drawn seamless steel pipe: pipe blank → heating → piercing → heading → annealing → pickling → oiling → multi pass cold drawing → blank pipe → heat treatment → straightening → hydrostatic test → marking → warehousing. The rolling method of cold drawn seamless steel pipe is more complicated than that of hot rolling, and the first three steps of their production process are basically the same. The difference starts from the fourth step. After the blank is punched, the blank shall be headed and annealed. After annealing, special acid liquid shall be used for pickling. After pickling, apply oil. Then followed by multiple cold drawing. After heat treatment, it shall be straightened. After the steel pipe is straightened, it is sent to the metal flaw detector by the conveyor belt for internal flaw detection. If there is a crack in the steel pipe, the same amount of bubbles will also be picked out.

　　From the appearance, the length of cold drawn seamless pipe is generally shorter than that of hot rolled seamless pipe. In terms of wall thickness, cold drawn seamless tubes are more uniform than hot rolled seamless tubes. The precision of hot rolled tubes is lower and the surface is rough, while the precision of cold drawn tubes is higher and the surface roughness is better.