Seamless steel pipe is a long strip of steel with hollow section and no joint around it. The thicker the wall thickness of seamless steel pipe is, the more economical and practical it is. The thinner the wall thickness is, the higher its processing cost will be; Its detection and shaping must be processed offline. Therefore, it embodies its advantages in high pressure, high strength and mechanical structure materials.
Seamless steel pipe can be divided into many types, such as hot rolled seamless steel pipe. Its production process is: round pipe blank → heating → perforation → three roll cross rolling, continuous rolling or extrusion → pipe stripping → sizing (or reducing) → cooling → straightening → hydrostatic test (or flaw detection) → marking → warehousing.
The raw material for rolling seamless steel pipe is round tube blank. The round tube blank shall be cut and processed by the cutter, and the blank with a growth of about 1m shall be sent to the furnace for heating through the conveyor belt. The billet is sent to the furnace for heating at a temperature of about 1200 degrees Celsius. The fuel is hydrogen or acetylene.
The temperature control in the furnace is the key problem. After the round tube billet is discharged from the furnace, it should be pierced through the pressure piercer. Generally, the more common piercer is the conical roll piercer. This piercer has high production efficiency, good product quality, large perforation expansion and can wear a variety of steel grades. After perforation, the round tube blank is successively rolled by three roll cross rolling, continuous rolling or extrusion. After extrusion, take off the pipe for sizing. The sizing machine rotates into the steel embryo at high speed through the conical drill to form a steel pipe. The inner diameter of seamless steel pipe is determined by the outer diameter length of sizing machine bit. After sizing, the steel pipe enters the cooling tower and is cooled by water spray. After cooling, the seamless steel pipe will be straightened.
There are also cold drawn seamless steel pipes: round tube blank → heating → perforation → heading → annealing → pickling → oiling (copper plating) → multi pass cold drawing (cold rolling) → blank tube → heat treatment → straightening → hydrostatic test (flaw detection) → marking → warehousing.
The first three steps of the production process of cold drawn and hot rolled seamless steel tubes are basically the same. The difference starts from the fourth step. After the round tube blank is emptied, it should be headed and annealed. After annealing, special acid liquid shall be used for pickling. After pickling, apply oil. Then, it is followed by multiple cold drawing and re blank pipe, and special heat treatment. After heat treatment, it will be straightened. After straightening, the seamless steel pipe is sent to the metal flaw detector (or hydrostatic test) by the conveyor belt for internal flaw detection.
