Rolling mill is the key equipment in the field of metal processing, which is widely used in the production of plate, profile and wire in steel, non-ferrous metals and other industries. The process varies according to product type (hot rolling, cold rolling) and material characteristics, but can be divided into the following core stages:
First, raw material preparation
Blank selection
According to the product needs to choose continuous casting billet, ingot or slab, common specifications include billet (150×150mm), slab (thickness 200-250mm).
Key index: chemical composition uniformity, no surface cracks and inclusions.
Pretreatment
Hot rolling: the billet needs to be heated by the heating furnace to 1100-1250℃ (steel) to achieve austenitizing.
Cold rolling: The hot rolled coil is pickled (hydrochloric or sulfuric acid) to remove the oxide sheet.
Two, rolling stage
(1) Hot rolling process
Descaling
High-pressure water (15-20MPa) jet clears the oxide layer on the surface of the billet to prevent rolling defects.
Rough rolling (blank rolling)
Using a reversible mill, the billet is rolled to an intermediate thickness (e.g. 30-50mm) in 5-7 passes.
Single pass deformation of 20-30%, rolling force up to 4000 tons or more.
Finishing rolling
Multi-stand continuous rolling (such as 7-stand four-high mill), the final rolling temperature is controlled at 850-950℃.
The thickness accuracy is ±0.1mm, and the crown of the plate is less than 1%.
Laminar cooling
The target metallographic structure (such as ferrite + pearlite) is obtained by controlled cooling at 10-30℃/s.
(2) cold rolling process
Annealing before rolling
Annealing in a shrill or continuous furnace (650-700 ° C) eliminates work hardening.
Multipass rolling
Using four/six high rolling mill, the total reduction rate of 60-90%.
Rolling oil lubrication reduces the coefficient of friction to 0.05-0.1.
Continuous annealing
Rapid heating (10℃/s) to 800℃ after quenching, improve deep drawing performance (such as automotive plate r value ≥1.8).
Third, post-processing process
Reel/cut
Hot rolling: hydraulic coiler coil (outer diameter 1.8-2.5m, tension 10-50kN).
Cold rolling: longitudinal cutting or transverse cutting length (tolerance ±0.5mm).
Surface treatment
Galvanizing: hot dip plating (zinc layer thickness 10-20μm).
Color coating: roll coating + baking (film thickness 15-25μm).
Quality inspection
On-line thickness measuring instrument (accuracy ±1μm), laser profile measuring instrument, eddy current testing (defect detection rate ≥99%).
Fourth, process optimization direction
Intelligent control
Applying rolling force-AGC (automatic thickness control), bending roll + channeling roll shape control technology.
Energy conservation and consumption reduction
The hot charge heat transfer process (DHCR) reduces energy consumption to 0.8GJ/t and increases the yield to 98.5%.
New material development
High strength steel controlled rolling and cooling (TMCP) to achieve tensile strength ≥1200MPa.
5. Typical equipment configuration
Process equipment type key technical parameters
Heating step heating furnace heating capacity 300t/h
Roll diameter of two high reversing roughing mill Φ1100mm
Finishing CVC six-high mill rolling speed 15m/s
The maximum roll weight of the underground coiler is 30 tons
Through the above process, the mill can efficiently transform raw materials into precision products to meet the industrial needs, and its process design directly affects the mechanical properties, surface quality and production costs of the products. In the future, with the application of new processes such as ultra-fast cooling (UFC) technology and digital twin, rolling technology will develop in the direction of higher precision and lower energy consumption.
