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Steel is made through one of two dominant routes. The integrated blast furnace–basic oxygen furnace (BF–BOF) route reduces iron ore to liquid hot metal, then refines it with oxygen. The electric arc furnace (EAF) route melts mainly recycled steel with electricity, sometimes adding direct-reduced iron (DRI) or hot metal. Both routes produce crude steel, which is then cast, rolled and finished into products such as coil, plate, rebar, wire rod, sections and rails.
What “crude steel” means
Steel is an iron–carbon alloy containing less than 2% carbon, according to the World Steel Association. Crude steel is the steel produced immediately after primary refining and before it has been transformed into a market-ready shape. It is not unfinished in the sense of being unusable; it is the standard output that goes into casting and downstream rolling.
The phrase “from iron ore to finished steel” describes a complete production chain, but it does not describe every plant. A blast furnace route begins with ore. An EAF mill can begin chiefly with recycled steel and may use no newly mined ore in its metallic charge. The route, feedstock and plant configuration determine the exact sequence and material balance.
The two main steelmaking routes
| Feature | BF–BOF (integrated route) | EAF (electric arc route) |
|---|---|---|
| Primary metallic feed | Iron ore is reduced to liquid hot metal (pig iron); scrap is added to the BOF charge. | Steel scrap is melted; DRI or hot metal can supplement scrap, depending on supply and plant design. |
| Main energy or reducing input | Coke made from coking coal supplies heat and acts as a reducing agent in the blast furnace. | Electrical energy creates the arc that melts the charge. |
| Can it use 100% recycled steel? | No. World Steel Association describes scrap use of up to 30% in the BOF charge. | Yes. An EAF can operate with exclusively recycled steel, although many EAF operations use DRI or other iron units as well. |
| Primary refining vessel | Basic oxygen furnace, where oxygen removes excess carbon and impurities from hot metal. | Electric arc furnace, where melting and chemistry adjustment occur using electrical energy and alloy additions. |
| Downstream stages | Casting, reheating, rolling and finishing are broadly similar after crude steel is produced. | |
World Steel Association reports a rounded global mix of about 70% BF–BOF and 30% EAF production. Its separate explanation lists open-hearth production at about 0.4%, so the two headline shares should be read as rounded indicators rather than an exact, exhaustive partition of every tonne made worldwide.
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How the BF–BOF route turns ore into steel
1. Preparing the charge
The integrated route brings together iron ore, metallurgical coal, limestone and recycled steel. Coal is heated without oxygen to make coke. Coke is both the blast furnace’s main fuel and its reducing agent: it provides heat and helps remove oxygen from iron compounds in the ore. Limestone and other materials are included in the burden to support the furnace process and impurity removal.
The charge is introduced into a blast furnace in layers or controlled batches. Air is supplied to sustain the high-temperature reactions. As the ore is reduced, iron collects as a liquid. The resulting hot metal is also called pig iron and contains more carbon and other elements than finished steel.
2. Producing liquid hot metal
Inside the blast furnace, the key chemical change is reduction: oxygen is removed from iron ore so that metallic iron can form. The liquid iron absorbs carbon and other elements while moving through the furnace. The furnace therefore produces hot metal, not yet the low-carbon steel required for most products.
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Unlike an EAF charge that can be entirely recycled, the BF stage requires an ore-derived feed. Scrap does not replace the blast furnace; it is introduced later as part of the BOF metallic charge.
3. Refining in the basic oxygen furnace
Hot metal is transferred to a basic oxygen furnace. Scrap steel is also added. High-purity oxygen is blown into the vessel. Oxygen reacts with excess carbon and other unwanted elements, lowering their concentrations and converting the hot metal into crude steel. The BOF stage is therefore the principal refining step that changes ore-derived iron into steel chemistry.
Operators control the final composition by managing the hot-metal and scrap mix and by adding alloying materials where required. The exact additions depend on the grade being produced; a construction bar, a rail and a thin sheet do not require identical chemistry.
4. Casting the crude steel
When the chemistry and temperature are suitable, the BOF steel is tapped and cast into semi-finished shapes. World Steel Association identifies three principal forms: slabs, billets and blooms. These shapes are the bridge between primary steelmaking and the rolling mill.
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1. Charging scrap and other iron units
An EAF is charged mainly with steel scrap. Depending on the plant and available materials, direct-reduced iron or hot metal can be added to supplement scrap. The ability to use different combinations gives EAF producers flexibility, but the practical mix is constrained by scrap quality, metallic availability, the target grade and the furnace design.
2. Melting with an electric arc
Electrical energy creates an arc between electrodes and the metallic charge. The arc supplies the heat needed to melt the scrap and any DRI or hot metal. Unlike the blast furnace, the EAF does not depend on coke as the principal reducing agent for its melting step.
An EAF can use exclusively recycled steel. That does not mean every EAF heat uses 100% scrap: DRI and hot metal are often used when they improve chemistry control, compensate for insufficient scrap or meet a product specification.
3. Adjusting chemistry and tapping
Once the metal is molten, alloy additions are used to reach the required chemistry. The furnace crew also manages impurities and temperature before tapping the heat. The product at this point is crude steel, just as it is after BOF refining.
Electricity use is a defining input, but the environmental result depends on more than the furnace name. The electricity source, the proportion and quality of scrap, and any DRI or hot-metal addition all affect the route’s overall profile.
Representative inputs for 1,000 kg of crude steel
The following figures are World Steel Association route averages for 1,000 kg of crude steel, reported on its current raw-materials page and accessed in 2026. They are representative averages, not a recipe that every plant must follow. Actual charges vary with plant configuration, product grade and available feedstock.
| Input | BF–BOF route average | Recycled-steel EAF route average |
|---|---|---|
| Iron ore | 1,370 kg | 586 kg |
| Metallurgical or other coal input | 780 kg metallurgical coal | 150 kg coal |
| Limestone | 270 kg | 88 kg |
| Recycled steel | 125 kg | 710 kg |
| Electricity | Not stated in this route average | 2.3 GJ |
The EAF column is called a recycled-steel route average, yet it still includes an average iron-ore quantity. That reflects the wider material balance represented by the source, not a rule that every EAF must consume ore. Individual EAF plants can run on 100% scrap, while others use DRI or hot metal to supply additional iron units.
What happens after crude steel is made
Continuous casting into semi-finished shapes
Molten crude steel is cast into slabs, billets or blooms. A slab is the usual starting shape for flat products. Billets and blooms feed long-product mills, although the exact division depends on dimensions and mill design.
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Cast shapes are reheated as needed and passed through rolling stands that reduce thickness or change the cross-section. Hot rolling produces flat products such as plate and coil, and long products such as rebar, bars, wire rod, structural shapes and rails.
Finishing for the application
Finishing operations tailor the rolled steel to its use. They can include cold rolling for tighter dimensions or surface requirements, painting, and metal coating for protection or performance. Tubes may be welded or seamless, depending on how they are made and the product specification.
The result is supplied in forms that fabricators and manufacturers can use: coil for forming and sheet operations, plate for heavy structures, rebar for reinforced concrete, wire rod for drawn products, sections for buildings and infrastructure, and rails for track.
Why the route choice matters
Metallic feedstock and scrap availability
BF–BOF production is anchored in iron ore and creates its own hot metal before refining. EAF production is anchored in scrap, but can add DRI or hot metal when scrap quality, quantity or chemistry makes that useful. Scrap therefore matters in both routes: it is a major EAF feed and can make up part of the BOF charge.
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Energy and reducing chemistry
The blast furnace needs coke made from coking coal because coke supplies both heat and chemical reduction. The BOF then uses oxygen to remove carbon and impurities. The EAF concentrates its melting energy in electricity and adjusts chemistry with alloy additions. Comparing only the furnace name misses the effect of electricity generation and the metallic feed used alongside scrap.
Product capability and downstream equipment
After primary steelmaking, the two routes converge on casting, reheating, rolling and finishing. A plant’s caster, rolling mills and finishing lines can therefore be as important to the products it sells as the upstream furnace. Route choice alone does not tell you whether a mill produces coil, plate, rebar or rails.
Emissions context
World Steel Association reports an industry average of 2.18 tonnes of CO2e per tonne of steel produced in 2024, covering scopes 1, 2 and 3. This is not a route-specific footprint and should not be assigned unchanged to every BF–BOF or EAF plant. The association notes that most emissions are associated with producing iron from ore and that ore-based and scrap-based profiles differ substantially. For an EAF, electricity generation and the use of DRI or hot metal can materially change the result; for an integrated route, ironmaking is a major part of the burden.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Common points of confusion
“Is all steel made from iron ore?”
No. The BF–BOF route starts with ore, but an EAF can melt recycled steel as its only metallic input. Many EAF operations use a combination of scrap and other iron units, so “steelmaking” is broader than “ore reduction.”
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“Is pig iron already steel?”
Pig iron, or hot metal, is the liquid iron product of the blast furnace. It contains too much carbon and too many other elements to be treated as the final steel grade. The BOF refines it into crude steel.
“Does an EAF simply melt scrap and stop?”
No. Melting is central, but the heat still requires chemistry control. Alloy additions and other refining practices bring the liquid metal to the specified composition before it is cast.
“Is crude steel a finished product?”
It is a finished output of primary steelmaking, but not usually the form purchased by a fabricator. Casting, rolling and finishing convert it into usable flat and long products.
How to read steelmaking statistics
- Check the route definition. A figure for BF–BOF is not interchangeable with an EAF figure, even when both are reported per tonne of crude steel.
- Keep the boundary attached to the number. The 2.18 t CO2e figure covers scopes 1, 2 and 3 and is an industry average for 2024.
- Treat material balances as averages. The listed ore, coal, limestone, scrap and electricity quantities vary by plant, grade and feedstock market.
- Separate crude steel from finished steel. Production tonnage at the caster is not the same thing as tonnes of coil, plate, rebar or other finished forms after rolling and finishing.
- Expect the technology mix to evolve. Process diagrams depicting common 2020s routes do not include every developing low-carbon process, so today’s two-route summary is important but not a permanent limit on how steel can be made.
The complete chain in one view
- Choose the metallic route: ore-derived iron through BF–BOF, or mainly recycled steel through EAF, with possible DRI or hot-metal additions.
- Prepare inputs: coke, ore, limestone and scrap for the integrated route; scrap and any supplementary iron units for EAF.
- Make liquid iron or melt the charge: the blast furnace reduces ore to hot metal, while the EAF uses an electric arc to melt its metallic feed.
- Refine the metal: the BOF blows oxygen through hot metal; the EAF manages the molten bath and adds alloys to meet the grade.
- Cast crude steel: form slabs, billets or blooms.
- Roll and finish: reheat, hot-roll and, where required, cold-roll, paint or coat the steel into products such as coil, plate, rebar, bars, wire rod, tubes, sections and rails.
That sequence explains why “how steel is made” has no single furnace answer. The dominant BF–BOF and EAF routes begin with different materials and energy systems, but both end at crude steel and share much of the conversion path that turns a cast shape into a finished product.
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