Manufacturing process of thick wall steel pipe and seamless steel pipe:
Hot rolled (extruded seamless steel tube) round tube blank → heating → perforation → three roll cross rolling, continuous rolling or extrusion → pipe stripping → sizing (or reducing) cooling → straightening → hydrostatic test (or flaw detection) mark → warehousing.
The raw material for rolling seamless tube is round tube blank. And 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 ℃. The fuel is hydrogen or acetylene. Temperature control in furnace is a key problem. After the round tube billet is discharged from the furnace, it shall be perforated by the pressure piercer.
Generally, the more common piercer is the cone roll piercer. This kind of piercer has high production efficiency, good product quality, large perforation diameter 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 the steel pipe is determined by the outer diameter length of the sizing machine bit. After sizing, the steel pipe enters the cooling tower and is cooled by water spray. After cooling, the steel pipe will be straightened. After straightening, the steel pipe is sent to the metal flaw detector (or hydrostatic test) by the conveyor belt for internal flaw detection. If there are cracks, bubbles and other problems inside the steel pipe, they will be detected. Steel pipes should be strictly selected by hand after quality inspection. After the steel pipe is inspected, the number, specification, production batch number, etc. shall be sprayed with paint. And hoisted into the warehouse by crane.
Hot rolled seamless steel pipe: compared with cold rolling, cold rolling is rolling below the recrystallization temperature, and hot rolling is rolling above the recrystallization temperature. Hot rolling can destroy the casting structure of ingot, refine the grain of steel and eliminate the defects of microstructure, so as to make the steel compact and improve the mechanical properties. This improvement is mainly reflected in the rolling direction, so that the steel is no longer isotropic to a certain extent; Bubbles, cracks and looseness formed during pouring can also be welded under the action of high temperature and pressure.
Post time: Jan-21-2022