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