steel pipes are seamless steel pipes, mainly manufactured through hot-rolled and cold-drawn processes. The raw materials used are carbon structural steel ingots, continuous casting billets. The chemical composition of the raw materials, including carbon, manganese, phosphorus, and sulfur, needs to be verified in advance through spectroscopic Hot Rolled Pipe Process
The hot-rolled pipe process is suitable for large-diameter, thick-walled steel pipes.
Production Process:
Billet Heating
The cut billets are sent into the ring heating furnace, where the temperature needs to reach 1200~1250°C. During the heating process, the metal structure of the billets gradually attains an austenitic state, thereby reducing deformation resistance and facilitating piercing and rolling. The heating stage requires strict control of the temperature throughout the process, ensuring the temperature remains uniform to prevent local overheating or burning.
Perforation forming
The heated billet is made into a hollow rough pipe through an inclined rolling piercer. During the piercing process, under the coordinated operation of the rolls and the mandrel, plastic deformation occurs in the center of the billet, forming the inner hole.
Pipe Rolling and Sizing
The pierced billets are sent into the tube rolling mill via a conveyor, where multiple rolling passes adjust the outer diameter and wall thickness of the billets. The rolled tubes then enter a sizing machine to control the outer diameter and roundness of the finished tubes, meeting standard tolerance requirements and bringing them close to the final product size.
Cooling and straightening
After the steel pipes are sized, they are air-cooled to room temperature to prevent structural hardening or cracking caused by rapid cooling. The cooled steel pipes are then straightened using a straightening machine to eliminate bending and other shape defects.
Cutting Size
After straightening, the steel pipe is cut at both ends, with a length tolerance generally controlled within ±10mm.
Inspection
Through dimensional inspection and quality inspection, remove defective products that have surface cracks or protrusions.
Cold-Drawn Pipe Manufacturing Process
The cold drawing pipe process is suitable for small-diameter, thin-walled steel pipes.
Production Process:
Capillary pretreatment
Hot-rolled billets are used as raw materials, and the billets need to undergo pickling and washing to remove surface oxide scale and prevent corrosion of the steel pipes. A special lubricant is applied to the inside and outside walls of the steel pipes, which can reduce friction during the cold drawing process.
Cold drawing forming
The prepared capillary is sent into the cold drawing machine, where the steel pipe passes through the die and is stretched at room temperature to produce plastic deformation, gradually reducing the outer diameter and wall thickness.
Heat Treatment
Cold-drawn steel pipes need to undergo normalizing treatment, heating the pipes to 890~940°C, controlling the holding time, and then cooling them in air.
Finishing
Steel pipes that have been heat-treated need to be straightened again to ensure straightness and roundness, and then cut to length. Finally, the surface needs to be polished.
Inspection
After size inspection and quality inspection, the qualified steel pipes are packaged.
