Bessemer process
Henry Bessemer filed his first patent application in October 1855, securing the legal rights to his steel-making method a year later. The English inventor claimed inspiration from a conversation with Napoleon III during the Crimean War regarding better artillery materials. He described this moment as the spark that kindled one of the greatest revolutions of the century while riding in a cab from Vincennes to Paris. William Kelly, an American inventor working in the early 1850s, had experimented with similar methods before Bessemer's public announcement. Kelly stated in a letter to Scientific American that he believed his discovery was known in England three or four years prior. Several English puddlers visited his facility and may have spoken of his invention upon returning home. Bessemer licensed the process to four ironmasters for £27,000 but found their output failed to meet quality standards. His friend William Clay described the resulting steel as rotten hot and rotten cold. Bessemer eventually bought back these licenses for £32,500 after realizing technical problems lay within impurities in the iron. Robert Forester Mushet solved the issue by adding spiegeleisen to reintroduce carbon and manganese after burning off other elements. This alloy improved malleability and allowed the steel to withstand rolling at high temperatures. Mushet's patent lapsed due to unpaid fees and was acquired by Bessemer. The first commercial production began in Sheffield in 1858 using imported charcoal pig iron from Sweden.
The core mechanism involved blowing air through molten pig iron inside a large vessel called a converter. Oxygen in the air oxidized impurities such as silicon, manganese, and carbon contained within the raw material. These oxides escaped as gas or formed a solid slag that floated on top of the liquid metal. The refractory lining of the converter played a critical role depending on the phosphorus content of the ore. Bessemer himself used ganister sandstone linings for what became known as the acid process. When phosphorus levels were high, dolomite or magnesite linings were required instead. A single heat could treat between five and thirty tons of hot metal at once. Operators typically ran converters in pairs so one blew while the other filled or tapped. The conversion process took approximately twenty minutes compared to the full day previously needed for heating and stirring. Progress during the blow was judged by the appearance of the flame emerging from the mouth of the converter. Later improvements replaced human observation with photoelectric methods to increase precision. After the blow ended, carbon was readded to the liquid metal along with other alloying materials. This final step ensured the steel possessed specific properties suitable for construction or manufacturing.
Alexander Lyman Holley visited Bessemer's Sheffield works in 1862 and secured licenses for use in the United States. He returned to Troy, New York where he set up a mill with innovations improving productivity over the original English factory. The Pennsylvania Railroad funded Holley's second mill through its subsidiary Pennsylvania Steel after seeing the technology. Between 1866 and 1877, partners licensed eleven Bessemer steel mills across the country. Andrew Carnegie invested in the new technology after visiting Bessemer in 1872. Holley built the Edgar Thomson Steel Works which opened in 1875 and marked the start of US dominance in global production. Carnegie Steel reduced rail costs from $100 per ton to $50 between 1873 and 1875. By the 1890s, Carnegie sold rails for just $18 per ton. American output rose from around 157,000 tons annually before 1875 to 26 million tons by 1910. William Walker Scranton quadrupled his production at Lackawanna Iron & Coal Company using the process in 1876. A major dispute arose during Brooklyn Bridge construction when Abram Hewitt urged against using cheaper Bessemer steel. John A. Roebling's Sons submitted the lowest bid but lost the contract to J. Lloyd Haigh Co under Hewitt's direction.
Industrial chemist Sidney Gilchrist Thomas tackled the persistent problem of phosphorus creating low-grade steel. He contacted his cousin Percy Gilchrist who worked as a chemist at Blaenavon Ironworks. Manager Edward Martin provided test equipment and helped draft a patent issued in May 1878. The invention used dolomite or limestone linings instead of clay within the converter vessel. This modification became known as the basic Bessemer process or Gilchrist-Thomas process. An additional advantage was that the new processes formed more slag which could be recovered and sold profitably as fertilizer. The basic process remained in use longer especially in Continental Europe where iron ores contained high phosphorus levels. Almost all inexpensive construction steel in Germany utilized this method throughout the 1950s and 1960s. Open-hearth technology failed to remove all phosphorus from these specific ores making the basic Bessemer variant essential for local industries. The chemical shift allowed manufacturers to utilize previously unusable raw materials while maintaining structural integrity.
Scientific American published an 1890 speech by Abram S. Hewitt explaining the significant economic effects of increased cheap steel supply. Railroads expanded into sparsely inhabited regions leading to settlement and profitable trade of goods previously too costly to transport. Production costs dropped from £40 per long ton to between £6 and £7 per long ton. Steel rails lasted ten times longer than iron rails allowing heavier locomotives to pull longer trains. Freight capacity improved with car weight ratios shifting from one-to-one to two-to-one. Before the process introduction, steel was far too expensive for bridges or building frameworks so wrought iron dominated the Industrial Revolution. After adoption, steel and wrought iron became similarly priced though quality issues like britleness caused by nitrogen prevented many structural uses. Quality problems such as brittlement prevented Bessemer steel from being used for many structural applications until open-hearth methods emerged. The expansion enabled massive infrastructure projects that defined modern urban development during the late nineteenth century.
Commercial steel production using this method stopped in the United States in 1968 after decades of dominance. The Iron and Coal Trades Review noted in 1895 that the heyday of the process was over and it had entered a semi-moribund condition. One major cause of decline was the failure of giant companies like Bolckow Vaughan to upgrade their technology. Basic oxygen steelmaking eventually replaced the original method offering better control of final chemistry. The speed of the original process allowed little time for chemical analysis or adjustment of alloying elements. Conversion costs increased as low-phosphorus ores became more expensive and scrap steel usage remained limited. Electric arc furnace technology competed favorably resulting in total obsolescence for most applications. Henry Bessemer knew pure oxygen blast offered advantages but 19th-century technology could not produce large quantities economically. The basic oxygen Linz-Donawitz process decarburized by blowing oxygen gas rather than burning excess carbon away with air. This innovation provided superior control over the final product composition while maintaining efficiency.
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Common questions
When did Henry Bessemer file his first patent application for the steel-making method?
Henry Bessemer filed his first patent application in October 1855 and secured legal rights to the method a year later. The English inventor claimed inspiration from a conversation with Napoleon III during the Crimean War regarding better artillery materials.
How much money did William Kelly claim he had spent on developing similar methods before Bessemer's announcement?
William Kelly stated in a letter to Scientific American that he believed his discovery was known in England three or four years prior. Several English puddlers visited his facility and may have spoken of his invention upon returning home.
What specific alloy did Robert Forester Mushet add to solve impurity issues in the Bessemer process?
Robert Forester Mushet solved the issue by adding spiegeleisen to reintroduce carbon and manganese after burning off other elements. This alloy improved malleability and allowed the steel to withstand rolling at high temperatures.
Which company produced the first commercial steel using the Bessemer process in 1858?
The first commercial production began in Sheffield in 1858 using imported charcoal pig iron from Sweden. The core mechanism involved blowing air through molten pig iron inside a large vessel called a converter.
When did industrial chemist Sidney Gilchrist Thomas receive his patent for the basic Bessemer process?
Manager Edward Martin provided test equipment and helped draft a patent issued in May 1878. The invention used dolomite or limestone linings instead of clay within the converter vessel.