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Ferrous metallurgy involves processes and alloys based on iron. It began far back in prehistory. The earliest surviving iron artifacts, from the 4th millennium BC in Egypt, were made from meteoritic iron-nickel.〔 By the end of the 2nd millennium BC iron was being produced from iron ores from South of the Saharan Africa to China. The use of wrought iron (worked iron) was known by the 1st millennium BC. During the medieval period, means were found in Europe of producing wrought iron from cast iron (in this context known as pig iron) using finery forges. For all these processes, charcoal was required as fuel. Steel (with a carbon content between pig iron and wrought iron) was first produced in antiquity as an alloy. Its process of production, Wootz, was exported before the 4th century BC to ancient China, Africa, the Middle East and Europe. Archaeological evidence of cast iron appears in 5th century BC China.〔 New methods of producing it by carburizing bars of iron in the cementation process were devised in the 17th century. During the Industrial Revolution, new methods of producing bar iron without charcoal were devised and these were later applied to produce steel. In the late 1850s, Henry Bessemer invented a new steelmaking process, that involved blowing air through molten pig iron to burn off carbon, and so to produce mild steel. This and other 19th-century and later processes have displaced the use of wrought iron. Today, wrought iron is no longer produced. == Meteoric iron == Iron was extracted from iron-nickel meteorites, which comprise about 6% of all meteorites that fall on the earth. That source can often be identified with certainty because of the unique crystalline features ("Widmanstatten figures") of that material, which are preserved when the metal is worked cold or at low temperature. Those artifacts include, for example, a bead from the 5th millennium BC found in Iran〔 and spear tips and ornaments from Ancient Egypt and Sumer around 4000 BC.〔R. F. Tylecote, ''A History of Metallurgy'' (2nd edn, 1992), 3〕 Meteoric iron has been identified also in a Chinese axe head from the middle of the 2nd millennium BC. These early uses appear to have been largely ceremonial or ornamental. Meteoritic iron is very rare, and the metal was probably very expensive, perhaps more expensive than gold. The early Hittites are known to have bartered iron (meteoritic or smelted) for silver, at a rate of 40 times the iron's weight, with Assyria. Meteoric iron was also fashioned into tools in the Arctic, about the year 1000, when the Thule people of Greenland began making harpoons, knives, ulos and other edged tools from pieces of the Cape York meteorite. Typically pea-size bits of metal were cold-hammered into disks and fitted to a bone handle.〔 These artifacts were also used as trade goods with other Arctic peoples: tools made from the Cape York meteorite have been found in archaeological sites more than 1,000 miles (1,600 km) distant. When the American polar explorer Robert Peary shipped the largest piece of the meteorite to the American Museum of Natural History in New York City in 1897, it still weighed over 33 tons. Another example of a late use of meteoritic iron is an adze from around 1000 AD found in Sweden.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ferrous metallurgy」の詳細全文を読む スポンサード リンク
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