Manufacturing Method of Seamless Steel Pipe

　　Seamless steel pipe can be divided into hot rolled pipe, cold rolled pipe, cold drawn pipe and extruded pipe according to different production methods.

　　Hot rolled seamless tubes are generally produced on automatic tube rolling mills. After the solid tube blank is inspected and the surface defects are removed, it is cut to the required length, centered on the end face of the piercing end of the tube blank, then sent to the heating furnace for heating, and punched on the piercing machine. In the process of piercing, the continuous rotation and advance, under the action of the roll and the plug, a cavity is gradually formed inside the tube blank, which is called the blank. Then it is sent to the automatic pipe mill to continue rolling. Finally, the wall thickness is adjusted by the homogenizer, and the diameter is calibrated by the sizing machine to meet the specification requirements. It is an advanced method to produce hot rolled seamless steel pipe by continuous pipe rolling mill.

　　In order to obtain seamless tubes with smaller size and better quality, cold rolling, cold drawing or a combination of the two methods must be adopted. Cold rolling is usually carried out on a two high mill. The steel pipe is rolled in an annular pass consisting of a variable cross-section circular groove and a fixed conical plug. Cold drawing is usually carried out on 0.5~100T single chain or double chain cold drawing machine.

　　The extrusion method means that the heated tube blank is placed in a closed extrusion cylinder, and the piercing rod and the extrusion rod move together to extrude the extrusion part from the smaller die hole. This method can produce steel pipes with smaller diameters.