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Bessemer steel process
1856· Innovation· Innovations & industries
Mostly agreedGood evidence; some details uncertain.
A method of blowing air through molten iron to burn out carbon, making cheap steel in minutes instead of days.
See it on the Innovation & Wealth map →What happened
Englishman Henry Bessemer patented it in 1856; Kentucky ironmaster William Kelly claimed he got there first. A pear-shaped converter blasted air through molten pig iron, burning off excess carbon in about 20 minutes. The steel was brittle until Robert Mushet added manganese, and phosphorus-rich ores needed Sidney Gilchrist Thomas's 1878 lining. Bessemer earned about £1 million in royalties. US steel-rail prices fell from over $100 a ton in the early 1870s to under $20 by 1898.
Impact on society and the economy
Steel went from costly specialty to bulk commodity, making long-lasting rails, bridges, skyscraper frames and machines affordable. Skilled iron puddlers, who stirred iron by hand, lost their trade.
How we know
Bessemer's 1856 patents and his paper to the British Association, Kelly's 1857 US priority patent, mill cost records, and published price series for steel rails.
Still debated
How much credit Kelly deserves is debated; his early experiments are poorly documented. Mushet and Thomas also made the process workable.
Connections (2)
▸Bessemer steel process supplied cheap rails for Railways and the railway ageWell documented
The connection
Iron rails wore out fast under heavier, faster trains, sometimes within months on busy lines. Bessemer steel rails lasted many times longer and carried heavier loads, and as steel prices collapsed after 1870 railroads relaid their tracks in steel, cutting maintenance costs and freight rates.
When and how
Derby, England, 1857: Robert Mushet's trial steel rail lasted about 16 years where iron needed frequent replacing. US railroads switched mainly in the 1870s–1890s.
How we know
Railroad maintenance records and rail-price data document the switch; US steel rail output overtook iron rails by about 1880.
Debates
How much cheaper steel, rather than competition, falling wages and better management, drove the fall in freight rates is hard to separate.
▸Bessemer steel process was adopted at scale by Andrew CarnegieWell documented
The connection
After seeing Bessemer converters in Britain, Carnegie bet heavily on the process, opening the Edgar Thomson Works near Pittsburgh in 1875 to roll steel rails. He relied on experts like plant designer Alexander Holley and superintendent Bill Jones, ran the plant nonstop and tracked every cost, making his firm the world's low-cost producer.
When and how
Braddock, Pennsylvania, 1872–75, after Carnegie's 1872 trip to Britain; engineer Alexander Holley designed the plant.
How we know
Company records, Carnegie's letters and autobiography, and production data showing his firm's output and costs.
Debates
How far his success rested on the process itself versus cost accounting, tariffs shielding US steel, and squeezing labor is debated.