In the steel industry, continuous casting and rolling technology (especially twin-roll casting and rolling) is a short-process method that directly and continuously casts molten steel into thin strip billets. Its core equipment is the steel continuous casting and rolling mill. Compared to the traditional “continuous casting + hot rolling” long process, steel casting mills significantly shorten the production flow and reduce energy consumption, making them a crucial technological direction for near-final-shape rolling of steel materials.
Steel Casting and Rolling Mill Key Stages and Components
1. Raw Material Preparation:
Scrap Metal/Iron Ore: The process begins with either scrap metal (recycled steel) or iron ore. Iron ore undergoes beneficiation to remove impurities and is then typically processed into pellets or sinter.
Coke: Coal is heated in the absence of oxygen to produce coke, which acts as a fuel and reducing agent in the blast furnace.
Flux: Limestone or dolomite is added to remove impurities as slag.
2. Steelmaking:
Blast Furnace (BF): If using iron ore, the blast furnace reduces iron ore with coke and limestone to produce molten "hot metal" (pig iron).
Basic Oxygen Furnace (BOF): Molten pig iron from the blast furnace (or a mix of pig iron and scrap) is refined in a BOF. Oxygen is blown through the molten metal to remove carbon and other impurities, converting it into steel.
Electric Arc Furnace (EAF): EAFs primarily use scrap metal as their raw material. Electric arcs melt the scrap, and then oxygen and other additives are used to refine the steel. EAFs are more flexible and have a smaller environmental footprint than BF-BOF routes.
3. Ladle Metallurgy:
After the primary steelmaking furnace, the molten steel is transferred to a ladle for secondary refining. This stage involves precise control of temperature and chemical composition to meet specific product requirements.
Degassing: Removal of dissolved gases like hydrogen and nitrogen.
Alloying: Addition of ferroalloys (e.g., ferromanganese, ferrochrome) to achieve desired steel properties (strength, corrosion resistance, etc.).
4. Continuous Casting:
This is a crucial stage where molten steel is solidified into semi-finished products like slabs, blooms, or billets.
Tundish: Molten steel flows from the ladle into a tundish, which acts as a reservoir and distributes the steel into molds.
Molds: The steel solidifies as it passes through water-cooled copper molds, forming a solid skin.
Withdrawal Rolls: The partially solidified strand is continuously pulled downwards by withdrawal rolls.
Sprays: Water sprays cool the strand further until it is completely solid.
Cutting: The continuous strand is cut into desired lengths (slabs for flat products, blooms for structural shapes, billets for long products).
The Combined Process
In a modern steel plant, casting and rolling are an integrated, continuous process. Molten steel is continuously cast into a semi-finished product (a billet, bloom, or slab) which, while still hot, is directly fed into the rolling mill. This integration significantly increases efficiency by eliminating the need to reheat the steel from a cold state, saving time and energy. The final products, whether they are I-beams, steel plates, or wire rods, are then cooled, cut to length, and prepared for shipment.
