Types of seamless steel pipes and corresponding production processes
Seamless steel pipe is a long steel with a hollow section and no joints on the periphery. The thicker the wall thickness of a seamless steel pipe, the more economical and practical it is, and the thinner the wall thickness, its processing cost will rise significantly; its inspection and shaping must be processed offline. Therefore, it embodies its superiority in terms of high pressure, high strength, and mechanical structure materials.
 
 
Hot rolled seamless steel tube
Seamless steel pipes can be divided into many types, such as hot-rolled seamless steel pipes. Its production process is: round tube billet → heating → piercing → three-roll cross rolling, continuous rolling or extrusion → pipe removal → sizing (or reducing diameter) )→cooling→straightening→hydraulic test (or flaw detection)→marking→warehousing.
 
The raw material for rolling seamless steel pipes is round tube blanks. The round tube blanks are cut by a cutting machine into a billet with a length of about 1 meter and sent to the furnace for heating via a conveyor belt. The billet is fed into the furnace and heated at a temperature of approximately 1200 degrees Celsius. The fuel is hydrogen or acetylene.
 
The temperature control in the furnace is a key issue. After the round tube is out of the furnace, it must be pierced through a pressure punching machine. Generally, the more common piercing machine is the tapered roller piercing machine. This type of piercing machine has high production efficiency, good product quality, large perforation diameter expansion, and can wear a variety of steel types. After piercing, the round tube billet is successively cross-rolled, continuously rolled or extruded by three rolls. After squeezing, take off the tube and calibrate. The sizing machine uses a tapered drill to rotate at a high speed into the steel blank to punch holes to form a steel pipe. The inner diameter of the seamless steel pipe is determined by the length of the outer diameter of the drill bit of the sizing machine. After the steel pipe is sized, it enters the cooling tower and is cooled by spraying water. After the seamless steel pipe is cooled, it will be straightened.
 
 
Cold drawn seamless steel tube
There are also cold drawn seamless steel pipes: round tube blank → heating → piercing → heading → annealing → pickling → oiling (copper plating) → multi-pass cold drawing (cold rolling) → blank tube → heat treatment → straightening → water pressure Test (detection) → mark → put in storage.
 
The first three steps of the production process of cold-drawn and hot-rolled seamless steel pipes are basically the same. The difference starts from the fourth step. After the round billet is emptied, it needs to be headed and annealed. After annealing, use a special acid liquid for pickling. After pickling, apply oil. Then it is followed by multiple passes of cold drawing and re-blanking, and special heat treatment. After heat treatment, it is straightened. After straightening, the seamless steel pipe is sent to the metal flaw detector (or hydraulic test) by the conveyor belt for internal flaw detection.