The hot-rolled steel pipe is continuously cast slab or slab slab as raw material, heated by a step-type heating furnace, descaled by high-pressure water, and then enters the rough rolling mill. The rough-rolled material passes through the cutting head and the tail, and then enters the finishing mill to implement computer control. After rolling, after the final rolling, it is subjected to laminar cooling and coiling, and becomes a straight hair roll. The head and tail of the straight hair roll are often in the shape of a tongue and a fishtail. The thickness and width are poorly accurate, and the side has frequent defects such as a wave shape, a folded edge, and a tower shape.
The weight of the coil is heavier and the inner diameter of the coil is 760 mm. (Generally, the tube industry likes to use it.) After the straight hair is wound through the cutting, cutting, trimming and multi-pass straightening, leveling and other finishing lines, then cutting or rewinding, it becomes: hot rolling Steel plates, flat hot rolled steel coils, slitting belts and other products. If the hot-rolled finishing roll is pickled to remove the scale and oiled, the hot-rolled pickled sheet roll is formed. This product has a tendency to partially replace cold-rolled sheets. The price of seamless steel tubes is moderate and is well received by users.
The cold drawn tube is made of hot-rolled steel coil as raw material, and is subjected to pickling to remove scale and then cold-rolled. The finished product is rolled hard roll. The cold work hardening caused by continuous cold deformation makes the strength and hardness of the rolled hard roll rise and tough. The plastic index is reduced, so the stamping performance will deteriorate and can only be used for parts that are simply deformed. Rolled hard rolls can be used as raw materials for hot-dip galvanizing plants because the hot-dip galvanizing units are equipped with an annealing line. The hard roll weight is generally 6~13.5 tons, and the inner diameter of the coil is 610mm.
Generally, cold-rolled rolled sheets and coils should be subjected to continuous annealing (CAPL unit) or hood furnace annealing to eliminate cold work hardening and rolling stress, and achieve the mechanical properties specified in the corresponding standards.