20 # seamless steel pipe refers to steel ingots or billets with a carbon content of 0.20%, which are punched into tubes and then hot-rolled, cold-rolled, or cold drawn. This type of steel pipe is produced and widely used in China. The main equipment in production is the steel pipe rolling mill, which belongs to the category of steel rolling.
The raw material for rolling seamless steel pipes is round billets, which are cut into billets with a length of about 1 meter by a cutting machine and sent to a heating furnace for heating through a conveyor belt. The billet is sent to the heating furnace for heating at a temperature of approximately 1200 degrees Celsius. The fuel is hydrogen or acetylene. The temperature control of the heating furnace is a key issue.
The next step is the centering process. Due to the irregular size of the billet after heating, it is necessary to determine the centerline of the tube, which is the centering process.
After the round billet is taken out of the furnace, it must be perforated with a pressure perforating machine. Generally speaking, the most common perforating machine is the conical roller perforating machine, which has high production efficiency, good product quality, large perforation volume, wide diameter expansion range, and can pierce various types of steel. There is currently no universally accepted conclusion on the magnitude of mechanical stress during the perforation process.
After perforation, the round tube blank is sequentially rolled, continuously rolled or extruded into shape by three rolls. The auxiliary rod in the middle of the steel pipe is called the core rod. There are three forms of motion of the core rod during the rolling process: fixed core rod, floating core rod, and semi floating core rod. Fixed core shaft refers to the core shaft not moving, floating core shaft refers to the core shaft freely moving during the rolling process, and semi floating core shaft refers to the core shaft not moving first, and then freely moving towards the end of rolling. Each method has its advantages and disadvantages.
After rolling is completed, heat is applied. The heating furnace in the production process diagram shown in the above figure is a stepper heating furnace. Simply put, the two cam mechanisms in the figure drive the steel pipe to perform a cyclic reciprocating motion.
Then reduce the diameter and take out the pipe blank for sizing. In fact, the production process and techniques for sizing and reducing the diameter are basically the same, except that the amplitude of the change in steel pipe diameter varies greatly. The sizing machine uses a conical drill bit to rapidly rotate and insert steel billets for drilling, thereby forming steel pipes. The inner diameter of the steel pipe is determined by the outer diameter of the drill bit of the sizing machine. After sizing the steel pipe, it enters the cooling tower and undergoes water spray cooling. After cooling, the steel pipe needs to be straightened. Straightening is completed by a straightening machine.
After straightening, the steel pipe is transported by a conveyor belt to a metal flaw detector (or hydrostatic test) for internal inspection. If there are cracks, bubbles, and other issues inside the steel pipe, they will be detected. After passing the quality inspection of steel pipes, they must also undergo strict manual screening. After passing the quality inspection of the steel pipe, it will be painted with the pipe number, specifications, production batch, etc., and lifted into the warehouse by a crane.
