What is the basic process of steelmaking?

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The steelmaking process is the transformation of raw materials such as iron ore or scrap steel into steel through a series of physical and chemical reactions. It is mainly divided into two methods: the long-process method (blast furnace-converter process) and the short-process method (electric arc furnace process). The typical long-process steelmaking process (including the short process) involves the following steps: 1. Raw material preparation – Iron ore, whose main component is iron oxide (such as hematite and magnetite), needs to be crushed and processed through mineral processing. Coke: as a fuel and reductant for blast furnaces. Flux (limestone, dolomite): used to remove impurities and adjust the composition of the slag. Scrap steel (the main raw material in the electric furnace process): recycled steel that is remelted. 2. Iron smelting (blast furnace iron smelting) Blast furnace structure: a high-temperature vertical furnace with temperatures reaching up to 2000°C. Carbon monoxide enters the blast furnace after being mixed with air along with coal powder or coke, where it comes into full contact with iron oxide. Reaction process: Coke burns to produce CO, which reduces the iron oxide in iron ore: Fe2O3 + 3CO = 2Fe + 3CO2. Limestone decomposes into CaO, which together with impurities such as SiO2 and Al2O3 forms slag (silicates). Product: liquid pig iron (containing about 4% carbon, as well as impurities such as sulfur and phosphorus). See Figure 1. Figure 1 3. Steelmaking (converter or electric arc furnace) (1) Converter steelmaking (long process): Raw materials: liquid pig iron (70-80%) + scrap steel. Oxygen top-blowing (BOF): High-pressure oxygen is blown into the molten pool to oxidize elements such as carbon, silicon, manganese, and phosphorus. Lime is added (for desulfurization and dephosphorization) to form steel slag. The carbon content is reduced to 0.02%-1.5%, yielding molten steel. (2) Electric arc furnace steelmaking (short process): Raw material: scrap steel (accounting for over 90%). Electric heating: Graphite electrodes generate an arc, reaching a temperature of 3000°C to melt scrap steel. Deoxygenation alloying: Adding ferrosilicon, ferromanganese, etc. to adjust the composition. See Figure 2. Blast furnace steelmaking process flow Chart 2 4. Secondary refining Purpose: To improve the purity of the molten steel and precisely control its composition. Common methods: LF furnace (ladle refining): desulfurization, deoxidation, alloying. RH vacuum treatment: removes hydrogen and nitrogen, reducing inclusions. VD furnace: Vacuum degassing, used for high-end steels (such as bearing steel). 5. Continuous casting process: Molten steel is poured into a continuous caster, where it cools and solidifies to form slabs, billets, rounds, etc. Advantages: Replaces traditional casting, improves efficiency, and reduces segregation. See Figure 3. Taiyuan Iron and Steel: Technological innovation as the engine for the company’s sustainable development. Figure 3 6. Rolling (hot rolling/cold rolling): Heating to above 1100°C, followed by rolling to produce sheets, profiles (such as H-beams), and wires. Cold rolling: Rolling at room temperature to produce thin sheets and precision tubes (with a smoother surface). 7. Post-treatment and quality control: Heat treatment: annealing, quenching, etc., to improve mechanical properties. Surface treatment: galvanizing, anti-corrosion coating. Testing: composition analysis, mechanical property testing, non-destructive testing. Comparison of key processes: Process – Long process (blast furnace-converter) vs. Short process (electric arc furnace). Raw materials – Iron ore + coke vs. Scrap steel (≥90%). Energy consumption – Higher vs. Lower (depends on electricity). Carbon emissions – High (due to the use of coke) vs. Low (due to scrap steel recycling). Applicable scenarios – Large-scale production of plain steel | Special steels, small-batch production. In recent years, more emphasis has been placed on environmental protection and innovation. Emission reduction technologies: Recovery of blast furnace gas (CCUS), preheating of scrap steel in electric arc furnaces. Hydrogen metallurgy: Using hydrogen to replace coke in the reduction of iron ore (experimental stage). Through the above process, iron ore or scrap steel is ultimately processed into various types of steel required in industries such as construction, automotive, and machinery.