Industrial steelmaking

In plain language

Steel is mainly iron with a small, controlled amount of carbon. Iron from a blast furnace contains too much carbon and other impurities to be useful as steel. Henry Bessemer's process, patented in 1856, solved this problem by blowing air through the molten iron. The oxygen in the air burns off the impurities, and the heat from that reaction keeps the iron liquid.

Over the following century, steelmakers developed other furnaces. The open-hearth furnace was widely used until most open-hearth furnaces were shut down by the early 1990s. The basic oxygen furnace, which blows nearly pure oxygen onto the metal, spread from the 1950s, and blast furnace and basic oxygen plants still make about 70% of the world's steel. The electric arc furnace melts steel scrap with electricity and can make steel from recycled material alone. The International Energy Agency (IEA) reports that the direct CO2 intensity of steelmaking has risen since 2021, so cutting its emissions is a current challenge.

Technical explanation

Blast-furnace iron, called pig iron or hot metal, typically contains about 4% carbon, with smaller amounts of silicon, phosphorus and sulphur. In the basic oxygen furnace, a lance blows 99% pure oxygen at a pressure of about 700 to 1,000 kilopascals onto the hot metal. The oxygen oxidises the carbon and other impurities. The Linz-Donawitz (LD) process, developed by VÖEST at Linz and ÖAMG at Donawitz, was first put into operation at Linz in November 1952 and at Donawitz in May 1953.

The electric arc furnace uses an electric arc to melt its charge. Because the furnace can run on scrap steel, it allows steel to be made from a feedstock of 100% scrap, although hot metal or direct-reduced iron can also be used where available. Historically, electric arc steel was mainly used for long products, while integrated mills using blast and basic oxygen furnaces dominated flat products.

The IEA reports that blast furnace and basic oxygen routes still make about 70% of world steel. It also reports that direct CO2 emissions intensity has risen since 2021. Low-carbon routes, such as hydrogen-based plants, are at an early commercial stage and, according to IEA estimates, cost more than conventional plants. The figures in this profile are taken from the sources listed, and no per-route emissions value is given where the sources reviewed did not state one.

What the evidence says

Each statement is typed by the strength of its evidence and linked to the source that supports it.

Limitations and open problems

• The sources reviewed do not give verified emissions figures for each steelmaking route, so this profile does not state them.
• The IEA estimates that early commercial plants using 100% hydrogen blends cost 50% to 140% more than BF-BOF plants today.
• The IEA reports that capacity for near-zero emissions iron by 2030 remains at about 10 Mt, unchanged from 2024.
• The IEA reports that direct CO2 emissions intensity of steelmaking has risen since 2021.
• Blast furnace and basic oxygen routes still make about 70% of global steel, according to the IEA.

Possible future uses

Timeline

1. 12 Feb 1856Henry Bessemer is granted British patent number 356, dated 12 February 1856, for the process that blows air through molten pig iron to make steel. Sources: [1]
2. 1865Pierre-Émile Martin takes a licence from Siemens and applies the regenerative furnace to steelmaking, giving rise to the open-hearth process. Sources: [4]
3. 3 Apr 1948Robert Durrer's converter, in Switzerland, produces its first steel, the starting point for the oxygen process. Sources: [3]
4. Nov 1952The first basic oxygen converter of the Linz-Donawitz process goes into service at the VÖEST works in Linz. Sources: [3]
5. May 1953The second Linz-Donawitz converter, at the ÖAMG works in Donawitz, starts production. Sources: [3]
6. 1992Open-hearth furnaces have stopped operating in the United States, and most open-hearth furnaces worldwide are shut down by the early 1990s. Sources: [4]

Glossary

Pig iron

Iron from a blast furnace that contains a high level of carbon and other impurities, and that is refined into steel.

Basic oxygen furnace

A steelmaking vessel in which a jet of nearly pure oxygen is blown onto molten pig iron to remove carbon and other impurities.

Open-hearth furnace

A steelmaking furnace that melts and refines a bath of metal in a hearth. The Siemens version uses a regenerative furnace design.

Electric arc furnace

A furnace that melts steel scrap or iron using an electric arc, and that can make steel from scrap alone.

Sources

1. other
   Henry Bessemer
   Paul F. Erwin. EBSCO Research Starters, 2024. Accessed 22 Oct 2026.
2. other
   Process: Bessemer Process
   National Iron & Steel Heritage Museum, 2012. Accessed 22 Oct 2026.
3. other
   Basic oxygen steelmaking
   Wikipedia, 22 Oct 2026. Accessed 22 Oct 2026.
4. other
   Open-hearth furnace
   Wikipedia, 15 Sept 2026. Accessed 22 Oct 2026.
5. other
   Electric arc furnace
   Wikipedia, 22 Oct 2026. Accessed 22 Oct 2026.
6. other
   The Ford Model T
   Ford Motor Company, 16 Sept 2020. Accessed 22 Oct 2026.
7. government report
   Steel
   International Energy Agency, 2025. Accessed 22 Oct 2026.

Revision history

3 changes since this profile was created.