Drawing (rolling) seamless steel pipe: round tube billet →heating→piercing→heading→annealing→pickling→oiling (copper plating)→multi-pass cold drawing (cold rolling) →Blank tube→Heat treatment→Straightening→Hydraulic test (flaw detection)→Mark→In storage.

Hot rolling (extruded seamless steel pipe): round tube billet → heating → perforation → three-roll skew rolling, continuous rolling or extrusion → tube removal → sizing (or reducing) → cooling →Blank tube→Straightening→Hydrostatic test (or flaw detection)→Mark→In storage.

The following is an overview of the two steel pipe processes:

The hot-rolled steel coil is used as the raw material for cold-drawn steel pipe, which is subjected to continuous cold rolling after pickling to remove the oxide scale, and the finished product is a hard-rolled coil. The increase and the toughness and plasticity index decrease, so the stamping performance will deteriorate, and it can only be used for parts with simple deformation. Hard-rolled coils can be used as raw materials for hot-dip galvanizing plants, because hot-dip galvanizing units are equipped with annealing lines. The weight of the rolled hard coil is generally 6~13.5 tons, and the inner diameter of the steel coil is 610mm.

Generally, cold continuous rolled sheets and coils should be continuously annealed (CAPL unit) or bell furnace annealing to eliminate cold work hardening and rolling stress, and reach the mechanical properties specified in the corresponding standards.

The surface quality, appearance and dimensional accuracy of cold-rolled steel sheets are superior to those of hot-rolled sheets, and the thickness of the products is thinned to about 0.18mm, so they are favored by the majority of users. Deep processing of products with cold-rolled steel coils as substrates has become a high value-added product. Such as electro-galvanizing, hot-dip galvanizing, anti-fingerprint electro-galvanizing, color-coated steel coils, vibration-damping composite steel sheets, and PVC-coated steel sheets, etc., these products have good quality such as beautiful appearance and high corrosion resistance, and have been widely used. After annealing, cold-rolled steel coils must be finished, including trimming, trimming, trimming, leveling, leveling, recoiling, or slitting. Cold-rolled products are widely used in automobile manufacturing, home appliances, instrument switches, construction, office furniture and other industries. The weight of each package after baling of steel plates is 3~5 tons. The weight of the flat roll is generally 3~10 tons/roll. The inner diameter of the steel coil is 610mm.

The hot-rolled steel pipe is made of continuous casting slab or pre-rolled slab as raw material, heated by a walking furnace, descaled by high-pressure water, and then enters the rough rolling mill. Computer-controlled rolling is implemented, and after final rolling, it is cooled by laminar flow and coiled by a coiler to become a straight hair coil. The head and tail of the straight hair curler are often tongue-shaped and fish-tail-shaped, with poor thickness and width accuracy, and the edges often have defects such as wave shape, folded edge, and tower shape. The coil weight is heavier, and the inner diameter of the steel coil is 760mm. (It is generally used in the pipe making industry.) After the straight hair roll is processed by cutting head, tail cutting, edge trimming and multi-pass straightening, leveling and other finishing lines, then cutting or re-rolling, it becomes: hot rolling Steel plates, flat hot rolled steel coils, slitting strips and other products. If the hot-rolled finishing coil is pickled to remove the oxide scale and oiled, it becomes a hot-rolled acid-washed coil. This product has the tendency to partially replace the cold-rolled sheet, the price is moderate, and it is deeply loved by the majority of users.