According to different production methods, seamless steel pipes can be divided into hot-rolled pipes, cold rolled pipes, cold drawn pipes, extruded pipes, etc.
Hot rolled seamless pipe is usually produced on automatic pipe rolling mill. The solid billet is inspected and cleared of surface defects, cut to the required length, centered on the end face of the billet piercing, then sent to the heating furnace for heating, and pierced on the piercing machine. At the same time of piercing, the pipe is continuously rotates and advances. Under the action of the roll and the plug, a cavity gradually forms inside the billet, which is called the capillary.
Then send it to the automatic tube mill and continue rolling. At last, the reeling mill reel wall thickness of the pipe, and the diameter is fixed by the sizing machine to meet the specifications. It is an advanced method to produce seamless steel pipe by means of continuous tube rolling mill.
If you want to get smaller size and better quality seamless pipe, you must use cold rolling, cold drawing or combination of the two methods.
Cold rolling is usually carried out on a two-high mill. The steel pipe is rolled in a ring pass consisting of a variable section circular groove and a stationary conical plug. Cold drawing is usually carried out on a single chain or double chain cold drawing machine of 0.5 ~ 100T.
In the extrusion method, the heated pipe blank is placed in an airtight extrusion cylinder, and the punch rod moves with the extrusion rod to extrude the extruded part from a smaller die hole. This method can produce smaller diameter steel pipes.