Bessemer Steel
Henry Bessemer
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In 1856 Henry Bessemer announced a startling process: blow air through molten pig iron and the oxygen burns out the carbon and impurities, turning brittle iron into tough steel in minutes. He demonstrated it before the British Association at Cheltenham and patented the tilting converter — a pear-shaped vessel that roared like a volcano as it refined a whole heat of metal at once.
Steel had been precious, made in small crucibles and far too costly for rails or bridges. Bessemer's process cut the price of steel by more than three-quarters within two decades. Railways laid steel rails that outlasted iron tenfold, and engineers could suddenly dream in steel: the Brooklyn Bridge's cables in 1883, and the first steel-framed skyscrapers rising in Chicago.
The process itself was soon improved upon — the open-hearth furnace and later oxygen steelmaking refined the idea — but every one of them descends from Bessemer's blast of air. Sheffield, already the city of cutlery steel, became the city that taught the world to make steel by the ton.
Frequently asked
How does the Bessemer process work?
Air is blown through molten pig iron in a tilting converter; the oxygen burns out carbon and other impurities, turning brittle iron into tough steel in about twenty minutes.
Why was cheap steel so important?
Steel had been made in small crucibles and was too costly for rails or bridges. After Bessemer, steel rails lasted ten times longer than iron ones, and engineers could build bridges and skyscrapers in steel.
Who was Henry Bessemer?
A British inventor and engineer who announced his steelmaking process in 1856, was knighted in 1879, and made his base in Sheffield — the city of steel.
Why it matters today
Every steel skyscraper, suspension bridge, and railway line descends from Bessemer's 1856 blast of air — modern steelmaking, from the open hearth to today's furnaces, is his idea refined.
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