Steel

:See Steel (disambiguation) for other uses.

History of iron and steelmaking

Iron was in limited use long before it became possible to smelt it. The first signs of iron use come from Ancient Egypt and Sumer, where around 4000 BC small items, such as the tips of spears and ornaments, were being fashioned from iron recovered from meteorites (see ). About 6% of meteorites are composed of an iron-nickel alloy, and iron recovered from meteorite falls allowed ancient peoples to manufacture small numbers of iron artifacts.

Related Topics:
Ancient Egypt - Sumer - 4000 BC - Meteorite - Nickel

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Meteoric iron was also fashioned into tools in precontact North America. Beginning around the year 1000, the Thule people of Greenland began making harpoons and other edged tools from pieces of the Cape York meteorite. 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 1000 miles (1600 km) away. 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.

Related Topics:
North America - 1000 - Thule - Greenland - Harpoon - Cape York meteorite - American - Robert Peary - American Museum of Natural History - New York City - 1897 - Ton

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The name for iron in several ancient languages means "sky metal" or something similar. In distant antiquity, iron was regarded as a precious metal, suitable for royal ornaments.

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The Iron Age Beginning between 3000 BC to 2000 BC increasing numbers of smelted iron objects (distinguishable from meteoric iron by their lack of nickel) appear in Anatolia, Egypt and Mesopotamia (see ). The oldest known samples of iron that appear to have been smelted from iron oxides are small lumps found at copper-smelting sites on the Sinai Peninsula, dated to about 3000 BC. Some iron oxides are effective fluxes for copper smelting; it is possible that small amounts of metallic iron were made as a by-product of copper and bronze production throughout the Bronze Age.

In Anatolia, smelted iron was occasionally used for ornamental weapons: an iron-bladed dagger with a bronze hilt has been recovered from a Hattic tomb dating from 2500 BC. Also, the Egyptian ruler Tutankhamun died in 1323 BC and was buried with an iron dagger with a golden hilt. An Ancient Egyptian sword bearing the name of pharaoh Merneptah as well as a battle axe with an iron blade and gold-decorated bronze haft were both found in the excavation of Ugarit (see Ugarit). The early Hittites are known to have bartered iron for silver, at a rate of 40 times the iron's weigh, with Assyria.

Related Topics:
Anatolia - Hatti - 2500 BC - Egypt - Tutankhamun - 1323 BC - Ancient Egyptian - Sword - Pharaoh - Merneptah - Battle axe - Ugarit - Hittites - Barter - Silver - Assyria

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Iron did not, however, replace bronze as the chief metal used for weapons and tools for several centuries, despite some attempts. Working iron required more fuel and significantly more labor than working bronze, and the quality of iron produced by early smiths may have been inferior to bronze as a material for tools. Then, between 1200 and 1000 BC, iron tools and weapons displaced bronze ones throughout the near east. This process appears to have begun in the Hittite Empire around 1300 BC, or in Cyprus and southern Greece, where iron artifacts dominate the archaeological record after 1050 BC. Mesopotamia was fully into the Iron Age by 900 BC, central Europe by 800 BC. The reason for this sudden adoption of iron remains a topic of debate among archaeologists. One prominent theory is that warfare and mass migrations beginning around 1200 BC disrupted the regional tin trade, forcing a switch from bronze to iron. Egypt, on the other hand, did not experience such a rapid transition from the bronze to iron ages: although Egyptian smiths did produce iron artifacts, bronze remained in widespread use there until after Egypt's conquest by Assyria in 663 BC.

Related Topics:
1200 - 1000 BC - Hittite Empire - 1300 BC - Cyprus - Greece - 1050 BC - Mesopotamia - 900 BC - 800 BC - Egypt - Assyria - 663 BC

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Iron smelting at this time was based on the bloomery, a furnace where bellows were used to force air through a pile of iron ore and burning charcoal. The carbon monoxide produced by the charcoal reduced the iron oxides to metallic iron, but the bloomery was not hot enough to melt the iron. Instead, the iron collected in the bottom of the furnace as a spongy mass, or bloom, whose pores were filled with ash and slag. The bloom then had to be reheated to soften the iron and melt the slag, and then repeatedly beaten and folded to force the molten slag out of it. The result of this time-consuming and laborious process was wrought iron, a malleable but fairly soft alloy containing little carbon.

Related Topics:
Bloomery - Bellows - Charcoal - Carbon monoxide - Wrought iron

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Wrought iron can be carburized into a mild steel by holding it in a charcoal fire for prolonged periods of time. By the beginning of the Iron Age, smiths had discovered that iron that was repeatedly reforged produced a higher quality of metal. Quench-hardening was also known by this time. The oldest quench-hardened steel artifact is a knife found on Cyprus at a site dated to 1100 BC.

Related Topics:
Carburized - Cyprus - 1100 BC

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Developments in China

Archaeologists and historians debate whether bloomery-based ironworking ever spread to China from the West. Around 500 BC, however, metalworkers in the southern state of Wu developed an iron smelting technology that would not be practiced in Europe until late medieval times. In Wu, iron smelters achieved a temperature of 1130°C, hot enough to be considered a blast furnace. At this temperature, iron combines with 4.3% carbon and melts, creating steel. As a liquid, iron can be cast into molds, a method far less laborious than individually forging each piece of iron from a bloom.

Related Topics:
500 BC - Wu - Blast furnace - Cast - Mold

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Cast iron is rather brittle and unsuitable for striking implements. It can, however, be decarburized to steel or wrought iron by heating it in air for several days. In China, these ironworking methods spread northward, and by 300 BC, iron was the material of choice throughout China for most tools and weapons. A mass grave in Hebei province, dated to the early third century BC, contains several soldiers buried with their weapons and other equipment. The artifacts recovered from this grave are variously made of wrought iron, cast iron, malleabilized cast iron, and quench-hardened steel, with only a few, probably ornamental, bronze weapons.

Related Topics:
300 BC - Hebei

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During the Han Dynasty (202 BC–AD 220), Chinese ironworking achieved a scale and sophistication not reached in the West until the eighteenth century. In the first century, the Han government established ironworking as a state monopoly and built a series of large blast furnaces in Henan province, each capable of producing several tons of iron per day. By this time, Chinese metallurgists had discovered how to puddle molten pig iron, stirring it in the open air until it lost its carbon and became wrought iron. (In Chinese, the process was called chao, literally, stir-frying.)

Related Topics:
Han Dynasty - 202 BC - AD 220 - Henan - Puddle - Chinese

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Also during this time, Chinese metallurgists had found that wrought iron and cast iron could be melted together to yield an alloy of intermediate carbon content, that is, steel. According to legend, the sword of Liu Bang, the first Han emperor, was made in this fashion. Some texts of the era mention "harmonizing the hard and the soft" in the context of ironworking; the phrase may refer to this process.

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India

Perhaps as early as 300 BC, although certainly by AD 200, high quality steel was being produced in southern India by what Europeans would later call the crucible technique. In this system, high-purity wrought iron, charcoal, and glass were mixed in crucibles and heated until the iron melted and absorbed the carbon. The resulting high-carbon steel, called ????? (pulâd) in Persian and wootz by later Europeans, was exported throughout much of Asia.

Related Topics:
300 BC - AD 200 - India - Crucible technique - Persian - Wootz

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Middle East

By the 9th century, smiths in the Abbasid caliphate had developed techniques for forging wootz to produce steel blades of unusual flexibility and sharpness (Damascus steel). The secret of forging this kind of steel was lost, even in the Middle East, by around 1600, and only recently have metallurgists found methods for reproducing its properties.

Related Topics:
9th century - Abbasid caliphate - Damascus steel

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Ironworking in medieval Europe

The middle ages in Europe saw the construction of progressively larger bloomeries. By the 8th century, smiths in northern Spain had developed a style that become known as a Catalan forge, a furnace about 1 meter (3 feet) tall, capable of smelting up to 150 kg (350 lb) of iron in each batch. In succeeding centuries, smiths in the Frankish empire and later the Holy Roman Empire scaled up this basic design, increasing the height of the flue to as tall as 5 meters (16 feet) and smelting as much as 350 kg (750 lb) of iron in each batch. These larger furnaces required more draft than could be provided by human power, and forging the large blooms that resulted was also beyond the capabilities of a single man. To this end, waterwheels were employed to power the bellows and hammers.

Related Topics:
Spain - Catalan forge - Frankish empire - Holy Roman Empire - Waterwheel

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Eventually, the scaling up of the bloomery reached a point where the furnace was hot enough to produce cast iron. Although the brittle cast iron may initially have been a nuisance to the smith, as it was too brittle to be forged, the spread of cannon to Europe in the 1300s provided an application for iron casting, cast iron cannonballs.

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The oldest known blast furnace in Europe was constructed at Lapphyttan in Sweden, sometime between 1150 and 1350. Other early European blast furnaces were built throughout the Rhine valley: blast furnaces were in operation near Liège (a city in modern-day Belgium) in the 1340s, and at Massevaux in France by 1409.

Related Topics:
Sweden - Rhine - Liège - Belgium - Massevaux - France - 1409

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The first English blast furnace was not built until 1496, when Henry VII commissioned a new ironworks at Newcastle, in a part of Sussex known as the Weald. Despite this late start, the production of English iron foundries rapidly grew, in no small part due to foreign craftsmen hired by Henry to bring the craft of iron casting to England. In 1543, William Levett, a Wealden ironmaster, and Peter Baude, a French craftsman in Henry VIII's employ, cast the Weald's first one-piece iron cannon. English iron cannons gained a reputation for being superior to, and less expensive than, the bronze cannons made elsewhere in Europe, and at least initially, efforts to copy them outside the Weald failed. The superiority of English cannons over Spanish ones has been credited as one factor in England's 1588 defeat of the Spanish Armada.

Related Topics:
1496 - Henry VII - Newcastle - Sussex - Weald - 1543 - William Levett - Peter Baude - French - Henry VIII - 1588 - Spanish Armada

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In 1619, Jan Andries Moerbeck, a Dutch ironmaster, began importing Wealden iron ore for comparison to the ore available on the Continent. One difference he observed was that the English ore contained some calcareous material, and soon after, Dutch ironmasters introduced the use of limestone as a flux in the blast furnace. This practice improved the separation of slag from the cast iron and improved the quality of Continental cast iron.

Related Topics:
1619 - Jan Andries Moerbeck - Dutch

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Ironworking in early modern Europe

Also by the early 1600s, ironworkers in western Europe had found a means (called cementation) to carburize wrought iron without individually forging each piece. Wrought iron bars and charcoal were packed into stone boxes, then held at a red heat for up to a week. During this time, carbon diffused into the iron, producing a product called cement steel or blister steel.

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For many years the best steels could be produced by buying expensive iron ore from Sweden. Although it was not understood at the time, Swedish ore had very low phosphorus content compared to most ores (notably those in England), which allowed for a finer and stronger crystal structure. Sales of Swedish ore generated considerable trade income, and local development helped the country become the industrial powerhouse it remains to this day.

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By the 18th century, deforestation in western Europe was making ironworking and its charcoal-hungry processes increasingly expensive. In 1709 Abraham Darby began smelting iron using coke, a refined coal product, in place of charcoal at his ironworks at Coalbrookdale in England. Although coke could be produced less expensively than charcoal, coke-fired iron was initially of inferior quality compared to charcoal-fired iron. It was not until the 1750s, when Darby's son refined the coking process to reduce the amount of sulfur in the coke that coke-fired furnaces became widespread.

Related Topics:
Deforestation - 1709 - Abraham Darby - Coke - Coal - Ironworks - Coalbrookdale - England - 1750

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Another 18th-century European development was the reinvention of the puddling furnace. In particular, the form of coal-fired puddling furnace developed by the British engineer Henry Cort in 1784 made it possible to convert cast iron into wrought iron in large batches, finally rendering the ancient bloomery obsolete. Wrought iron produced using this method became a major metal in the English midlands' emerging toy industry. The combination of the blast furnace and the puddling furnace allowed iron to be produced at either end of the carbon spectrum, depending on the user's needs.

Related Topics:
Puddling furnace - Henry Cort - 1784 - Toy industry

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As for alloys of intermediate carbon content (that is, steel), crucible steel was rediscovered in the 1740s by Benjamin Huntsman in Handsworth in England. In his process, wrought iron and cast iron were heated in small ceramic crucibles, melting together to form steel. While producing steel superior to cement steel, the crucible steel process remained relatively expensive in both time and fuel, and could not be used in any sort of modern industrial scale. The strong steels produced were however in high demand for specialty products such as cutlery and weapons. Sheffield's Abbeydale Industrial Hamlet has preserved a waterwheel powered, scythe-making works dating from Huntsman's times. It is still operated for the public, several times per year, using crucible steel made on the Abbeydale site.

Related Topics:
Crucible steel - Benjamin Huntsman - Handsworth - England - Cutlery - Sheffield - Abbeydale Industrial Hamlet

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Industrial steelmaking

The problem of mass-producing steel was solved in 1855 by Henry Bessemer, with the introduction of the Bessemer converter at his steelworks in Sheffield, England. (An early converter can still be seen at the city's Kelham Island Museum). In the Bessemer process, molten pig iron from the blast furnace was charged into a large crucible, and then air was blown through the molten iron from below, igniting the dissolved carbon. As the carbon burned off, the melting point of the mixture increased, but the heat from the burning carbon provided the extra energy needed to keep the mixture molten. After the carbon content in the melt had dropped to the desired level, the air draft was cut off: a typical Bessemer converter could convert a 25-ton batch of pig iron to steel in half an hour.

Related Topics:
1855 - Henry Bessemer - Bessemer converter - Sheffield - England - Kelham Island Museum

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In 1867, the German-British engineer Sir William Siemens introduced an improved puddling furnace – the regenerative furnace – that used brick heat exchangers to preheat the incoming air and conserve fuel. The next year Pierre and Émile Martin, French ironmasters who had licensed Siemens' furnace design, developed a method for measuring the carbon content of molten iron. Thus, the decarburization could be stopped at the steel stage rather than proceeding all the way to wrought iron. This open-hearth process coexisted in industrial practice with the Bessemer process for many years, but eventually proved more economical and displaced it. Reasons for this include its ability to recycle scrap metal in addition to fresh pig iron, its greater scalability (up to hundreds of tons per batch, compared to tens of tons for the Bessemer process), and the more precise quality control it permitted.

Related Topics:
1867 - German - British - Sir William Siemens - Regenerative furnace - Heat exchangers - Pierre - Émile Martin - Open-hearth process - Recycle - Scrap metal - Quality control

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Initially, only ores low in phosphorus and sulfur could be used for quality steelmaking; ores rich in those elements yielded brittle metals little better than cast iron. This problem was solved in 1878 by Percy Carlyle Gilchrist and his cousin Sidney Gilchrist Thomas at the ironworks at Blaenavon in Wales. Their modified Bessemer process used a converter lined with limestone or dolomite, and additional lime was added to the molten metal as a flux. This added basic material removed phosphorus and sulfur from the steel as insoluble calcium or magnesium phosphates and sulfates. This development expanded the range of iron ores that could be used to make steel, especially in France and Germany, where high-phosphorus ores abounded.

Related Topics:
1878 - Percy Carlyle Gilchrist - Sidney Gilchrist Thomas - Blaenavon - Wales - Limestone - Dolomite - Flux - Basic - France - Germany

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These developments increased the availability and decreased the price of steel; 22 thousand tonnes were produced in 1867, 500 thousand in 1870, 1 million in 1880 and 28 million by 1900. Today, worldwide annual production is around 850 million tonnes. This widespread availability of inexpensive steel powered the industrial revolution and modern society as we know it. It also led to the introduction of newer "niche" steels (such as stainless steel), all of them dependent on the wide availability of inexpensive iron and steel and the ability to alloy it at will.

Related Topics:
Industrial revolution - Stainless steel

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