Steel comes from iron ore, a rock found in the Earth’s crust that is rich in iron and oxygen. Turning that ore into steel requires stripping the oxygen away and adding a small amount of carbon, a process that has been refined over centuries but still relies on the same basic chemistry. The final product is over 99% iron, with carbon and trace elements like manganese and silicon making up the rest.
The Raw Materials
A traditional steel mill needs three main ingredients: iron ore, coal (processed into a fuel called coke), and limestone. Iron ore is mined from large deposits around the world, particularly in Australia, Brazil, China, and India. The ore itself isn’t pure iron. It’s a mineral compound of iron bonded with oxygen, and the entire steelmaking process revolves around breaking that bond.
Coal plays a dual role. Once converted into coke (by heating it in the absence of air), it serves as both a fuel source and a chemical partner. The carbon in coke is what pulls the oxygen out of the iron ore. Limestone acts as a cleaning agent, binding with impurities in the ore and floating them to the surface as slag, which gets skimmed off.
How Iron Ore Becomes Steel
The transformation happens in stages. First, iron ore and coke are loaded into a blast furnace and heated to extreme temperatures. At these temperatures, the carbon in the coke reacts with the oxygen in the ore, producing carbon dioxide gas and leaving behind molten iron. This molten iron still contains a few percent of carbon and other impurities, so it needs further refining to become steel.
That refining happens in one of two ways. The most common method worldwide uses a basic oxygen furnace, where pure oxygen is blown through the molten iron. This burns off excess carbon and impurities, bringing the carbon content down to roughly 1% or less. The result is steel. If the carbon content stays above about 2%, the material is classified as cast iron instead, which is harder but more brittle.
The second method uses an electric arc furnace, which works very differently. Instead of starting with iron ore, it melts down scrap steel (recycled metal from old cars, buildings, appliances, and industrial waste) using powerful electric currents. This approach skips the blast furnace entirely and requires no iron ore or coal as primary inputs. About 30% of the world’s steel is made this way.
What Makes Steel Different From Iron
The distinction between iron and steel comes down to carbon. Pure iron is relatively soft and bends easily. Adding a small amount of carbon, typically under 1%, changes the metal’s internal structure and makes it dramatically stronger and harder. That’s steel. Push the carbon content above 2% to 3% and you get cast iron, which holds its shape well and resists heat but cracks under impact rather than bending.
Steelmakers can also add other elements to create specialized varieties. Chromium produces stainless steel, which resists rust. Nickel and molybdenum improve strength at high temperatures. These alloy steels serve industries from aerospace to surgical equipment, but they all start from the same foundation of iron and carbon.
Where Steel Is Produced Today
Global crude steel production reached approximately 1.88 billion metric tons in 2024, according to the World Steel Association. China dominates the industry, producing about 1,005 million metric tons, which accounts for more than half of the world’s total. India came in second at roughly 150 million metric tons, followed by Japan (84 million), the United States (80 million), and Russia (71 million).
China’s share has grown enormously over the past two decades, driven by massive infrastructure and construction spending. India is the fastest-growing major producer, increasing output by over 6% from 2023 to 2024, while most other top producers saw slight declines.
The Environmental Cost
Steelmaking is one of the most carbon-intensive industrial processes on Earth, responsible for roughly 7% to 8% of global CO2 emissions. The biggest source of those emissions is the blast furnace, where carbon is literally the tool used to strip oxygen from iron ore. Every ton of steel produced through the traditional route releases close to two tons of CO2.
A growing alternative called hydrogen-based direct reduction replaces carbon with hydrogen gas as the agent that removes oxygen from iron ore. Instead of producing CO2, this reaction produces water. Research from Berkeley Lab found that using renewable hydrogen in this process can reduce direct CO2 emissions by up to 85% compared to conventional methods. The economics depend heavily on the cost of green hydrogen. Estimates suggest the approach becomes financially viable when hydrogen costs fall to around $1.70 per kilogram.
Electric arc furnaces already offer a lower-carbon path since they melt recycled steel rather than processing raw ore. When powered by renewable electricity, their emissions drop further still. The combination of hydrogen-based iron reduction feeding into electric arc furnaces represents the most promising route to producing steel without fossil fuels.