| In the early 17th century, ironworkers in | | | | iron produced using this method became a |
| western Europe had found a means (called | | | | major raw material in the English midlands' |
| cementation) to carburize wrought iron. | | | | iron manufacturing trades. |
| Wrought iron bars and charcoal were packed | | | | |
| into stone boxes, then held at a red heat for | | | | Industrial steelmaking |
| up to a week. During this time, carbon | | | | |
| diffused into the iron, producing a product | | | | The problem of mass-producing steel was |
| called cement steel or blister steel (see | | | | solved in 1855 by Henry Bessemer, with the |
| cementation process). One of the earliest | | | | introduction of the Bessemer converter at his |
| places where this was used in England was at | | | | steelworks in Sheffield, England. (An early |
| Coalbrookdale, where Sir Basil Brooke had two | | | | converter can still be seen at the city's |
| cementation furnaces (recently excavated). | | | | Kelham Island Museum). In the Bessemer |
| For a time in the 1610s, he owned a patent on | | | | process, molten pig iron from the blast |
| the process, but had to surrender this in | | | | furnace was charged into a large crucible, |
| 1619. He probably used Forest of Dean iron as | | | | and then air was blown through the molten |
| his raw material. | | | | iron from below, igniting the dissolved |
| | | | carbon from the coke. As the carbon burned |
| Soon after that it was found that the best | | | | off, the melting point of the mixture |
| steel could only be produced by buying | | | | increased, but the heat from the burning |
| expensive örgrund (or oregrounds) iron | | | | carbon provided the extra energy needed to |
| from Sweden. Although it was not understood | | | | keep the mixture molten. After the carbon |
| at the time, the ore from the Dannemora mine | | | | content in the melt had dropped to the |
| (from which it was made) had very low | | | | desired level, the air draft was cut off: a |
| phosphorus content compared to most ores | | | | typical Bessemer converter could convert a |
| (notably those in England), which allowed for | | | | 25-ton batch of pig iron to steel in half an |
| a finer and stronger crystal structure. Sales | | | | hour. |
| of Swedish iron generated considerable trade | | | | |
| income, and local development helped the | | | | In 1867, the German-British engineer Sir |
| country become the industrialised nation it | | | | William Siemens introduced an improved |
| remains to this day. This Swedish iron | | | | puddling furnace – the regenerative |
| provided the main basis for English | | | | furnace – that used brick heat |
| steelmaking until the 1850s | | | | exchangers to preheat the incoming air and |
| | | | conserve fuel. The next year Pierre and |
| Benjamin Huntsman in the 1740s found a method | | | | Émile Martin, French ironmasters who had |
| of producing a more homogeneous steel. This | | | | licensed Siemens' furnace design, developed a |
| was done by melting pieces of blister steel | | | | method for measuring the carbon content of |
| in crucibles. This was cast into ingots of | | | | molten iron. Thus, the decarburization could |
| crucible steel. He made this discovery at | | | | be stopped at the steel stage rather than |
| Handsworth in England. While producing steel | | | | proceeding all the way to wrought iron. This |
| superior to cement steel, the crucible steel | | | | open-hearth process coexisted in industrial |
| process remained relatively expensive in both | | | | practice with the Bessemer process for many |
| time and fuel, and could not be used in any | | | | years, but eventually proved more economical |
| sort of modern industrial scale. The strong | | | | and displaced it. Reasons for this include |
| steels produced were however in high demand | | | | its ability to recycle scrap metal in |
| for specialty products such as cutlery and | | | | addition to fresh pig iron, its greater |
| weapons. Sheffield's Abbeydale Industrial | | | | scalability (up to hundreds of tons per |
| Hamlet has preserved a waterwheel powered, | | | | batch, compared to tens of tons for the |
| scythe-making works dating from Huntsman's | | | | Bessemer process), and the more precise |
| times. It is still operated for the public, | | | | quality control it permitted. |
| several times per year, using crucible steel | | | | |
| made on the Abbeydale site. An improvement on | | | | Initially, only ores low in phosphorus and |
| crucible steel was the Cementation process. | | | | sulfur could be used for quality steelmaking; |
| | | | ores rich in those elements yielded brittle |
| References | | | | metals little better than cast iron. This |
| | | | problem was solved in 1878 by Percy Carlyle |
| * K. Barraclough, Steelmaking before Bessemer | | | | Gilchrist and his cousin Sidney Gilchrist |
| (2 vols, 1984). | | | | Thomas at the ironworks at Blaenavon in |
| | | | Wales. Their modified Bessemer process used a |
| * P. King, 'The cartel in oregrounds iron' | | | | converter lined with limestone or dolomite, |
| Journal of Industrial History 6 (2003), | | | | and additional lime was added to the molten |
| 25-48. | | | | metal as a Flux. This added basic material |
| | | | removed phosphorus and sulfur from the steel |
| Ironmaking in early modern Europe | | | | as insoluble calcium or magnesium phosphates |
| | | | and sulfates. This development expanded the |
| From the 16th century to the 18th century, | | | | range of iron ores that could be used to make |
| most iron was made by a two-stage process | | | | steel, especially in France and Germany, |
| involving a blast furnace and finery forge, | | | | where high-phosphorus ores abounded. |
| using charcoal as fuel. Production was | | | | |
| however limited by the supply of wood for | | | | Finally, the basic oxygen process was |
| making charcoal. | | | | introduced at the Voest-Alpine works in 1952; |
| | | | a modification of the basic Bessemer process, |
| By the 18th century, deforestation in western | | | | it lances oxygen from above the steel |
| Europe was making ironworking and its | | | | (instead of bubbling air from below), |
| charcoal-hungry processes increasingly | | | | reducing the amount of nitrogen uptake into |
| expensive. In 1709 Abraham Darby began | | | | the steel. The basic oxygen process is used |
| smelting iron using coke, a refined coal | | | | in all modern steelworks; the last Bessemer |
| product, in place of charcoal at his | | | | converter in the U.S. was retired in 1968. |
| ironworks at Coalbrookdale in England. | | | | Furthermore, the last three decades have seen |
| Although coke could be produced less | | | | a massive increase in the mini-mill business, |
| expensively than charcoal, coke-fired iron | | | | where scrap steel only is melted with an |
| was initially of inferior quality compared to | | | | electric arc furnace. These mills only |
| charcoal-fired iron. It was not until the | | | | produced bar products at first, but have |
| 1750s, when Darby's son, also called Abraham, | | | | since expanded into flat and heavy products, |
| managed to start selling coke-smelted pig | | | | once the exclusive domain of the integrated |
| iron for the production of wrought iron in | | | | steelworks. |
| finery forges. | | | | |
| | | | These developments increased the availability |
| Another 18th century European development was | | | | and decreased the price of steel; 22 thousand |
| the invention of the puddling furnace. In | | | | tonnes were produced in 1867, 500 thousand in |
| particular, the form of coal-fired puddling | | | | 1870, 1 million in 1880 and 28 million by |
| furnace developed by the British ironmaster | | | | 1900. In 2005, total world crude steel |
| Henry Cort in 1784 made it possible to | | | | production was 1,107.2 million metric tons |
| convert cast iron into wrought iron in large | | | | (mmt). The top three steel-producing |
| batches (without charcoal), rendering the | | | | countries were China (349.4 mmt), Japan |
| ancient finery forge obsolescent. Wrought | | | | (112.5 mmt) and the United States (93.9 mmt) |