Iron smelting—the extraction of usable metal from
oxidized iron ores—is more difficult than
tin and
copper smelting. While these metals and their alloys can be cold-worked or melted in relatively simple furnaces (such as the kilns used for
pottery) and cast into molds, smelted iron requires hot-working and can be melted only in specially designed furnaces. Iron is a common impurity in copper ores and iron ore was sometimes used as a
flux, thus it is not surprising that humans mastered the technology of smelted iron only after several millennia of
bronze metallurgy. This transition happened at different times in different places, as the technology spread. Mesopotamia was fully into the Iron Age by 900 BC. Although Egypt produced iron artifacts, bronze remained dominant until its conquest by Assyria in 663 BC. The Iron Age began in India about 1200 BC, in Central Europe about 800 BC, and in China about 300 BC. Around 500 BC, the
Nubians, who had learned from the Assyrians the use of iron and were expelled from Egypt, became major manufacturers and exporters of iron. The development of bloomery versus cast iron across regions may be due to influence by the applications demanded of iron within the respective socio-political environments In pre-Roman Britain, iron smelting was certainly firmly established during the Middle Iron Age in Yorkshire and may be linked to the
Arras culture. The large-scale, communal nature of the smelting at Thornton suggests it supported the significant demand for iron tools and funerary goods required by these communities.
Ancient Near East . Boxes colors:
arsenic in brown,
copper in red (the important mines of the
Arabah,
Timna and
Feynan, are missing from the map),
tin in grey, iron in reddish brown, gold in yellow, silver in white and
lead in black. The yellow area stands for
arsenic bronze, while grey area stands for tin
bronze. About 1500 BC, increasing numbers of non-meteoritic, smelted iron objects appeared in
Mesopotamia, Anatolia and Egypt. Nineteen meteoric iron objects were found in the
tomb of
Egyptian ruler
Tutankhamun, who died in 1323 BC, including an iron dagger with a golden hilt, an
Eye of Horus, the mummy's head-stand and sixteen models of an artisan's tools. An Ancient Egyptian sword bearing the name of pharaoh
Merneptah as well as a
battle axe with an iron blade and gold-decorated bronze shaft were both found in the excavation of
Ugarit. Although iron objects dating from the
Bronze Age have been found across the Eastern Mediterranean, bronzework appears to have greatly predominated during this period. As the technology spread, iron came to replace bronze as the dominant metal used for tools and weapons across the Eastern Mediterranean (the
Levant,
Cyprus,
Greece,
Crete, Anatolia and Egypt). Concurrent with the transition from bronze to iron was the discovery of
carburization, the process of adding carbon to wrought iron. While the iron bloom contained some carbon, the subsequent hot-working
oxidized most of it. Smiths in the Middle East discovered that wrought iron could be turned into a much harder product by heating the finished piece in a bed of charcoal, and then
quenching it in water or oil. This procedure turned the outer layers of the piece into
steel, an alloy of iron and
iron carbides, with an inner core of less brittle iron.
Theories on the origin of iron smelting The development of iron smelting was traditionally attributed to the
Hittites of Anatolia of the Late
Bronze Age. It was believed that they maintained a monopoly on iron working, and that their empire had been based on that advantage. According to that theory, the ancient
Sea Peoples, who invaded the Eastern Mediterranean and destroyed the Hittite empire at the end of the Late Bronze Age, were responsible for spreading the knowledge through that region. This theory is no longer held in the mainstream of scholarship, Bronze objects remained abundant, and these objects have the same percentage of tin as those from the Late Bronze Age.
Indian subcontinent The history of ferrous metallurgy in the Indian subcontinent began in the 2nd millennium BC. Archaeological sites in the
Gangetic plains have yielded iron implements dated between 1800 and 1200 BC. By the early 13th century BC, iron smelting was practiced on a large scale in India. and during a period of peaceful settlements in the 1st millennium BC. The Greek historian
Herodotus wrote the first
western account of the use of iron in India. The
Romans had high regard for the excellence of steel from India in the time of the
Gupta Empire.
Wootz steel was produced in India and
Sri Lanka from around 300 BC. Wootz steel is famous from
Classical Antiquity for its durability and ability to hold an edge. When asked by
King Porus to select a gift,
Alexander is said to have chosen, over
gold or
silver, thirty pounds of steel. According to
Will Durant, the technology passed to the
Persians and from them to
Arabs who spread it through the Middle East. In the 16th century, the
Dutch carried the technology from South India to Europe, where it was mass-produced. Steel was produced in
Sri Lanka from 300 BC Steel made in Sri Lanka was traded extensively within the region and in the
Islamic world. One of the world's foremost metallurgical curiosities is an
iron pillar located in the
Qutb complex in
Delhi. The pillar is made of wrought iron (98%
Fe), is almost seven meters high and weighs more than six tonnes. The pillar was erected by
Chandragupta II Vikramaditya and has withstood 1,600 years of exposure to heavy rains with relatively little
corrosion.
China iron
ore to make wrought iron from pig iron. The righthand illustration shows men working a
blast furnace (
Tiangong Kaiwu encyclopedia, 1637). Numerous scholars have suggested that the
Afanasievo culture may be responsible for the introduction of
metallurgy to
China. In particular, contact between the Afanasievo culture and the
Majiayao culture and the
Qijia culture are considered for the transmission of bronze technology. In 2008, two iron fragments were excavated at the
Mogou site, in
Gansu. They have been dated to the 14th century BC, belonging to the period of
Siwa culture. One of the fragments was made of bloomery iron rather than meteoritic iron. Other than this one exception, the earliest known iron artifacts made from bloomeries in China date to end of the 9th century BC. Cast iron was used in
ancient China for warfare, agriculture and architecture. A mass grave in
Hebei province, dated to the early 3rd 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. , 1313 AD, during the
Yuan dynasty in China During the
Han dynasty (202 BC–220 AD), the government established ironworking as a state monopoly,
repealed during the latter half of the dynasty and returned to private entrepreneurship, 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 fine molten pig iron, stirring it in the open air until it lost its carbon and could be hammered (wrought). In modern Mandarin-
Chinese, this process is now called
chao, literally
stir frying. Pig iron is known as 'raw iron', while wrought iron is known as 'cooked iron'. By the 1st century BC, 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. The ancient city of Wan (
Nanyang) from the Han period forward was a major center of the iron and steel industry. Along with their original methods of forging steel, the Chinese had also adopted the production methods of creating Wootz steel, an idea imported from India to China by the 5th century AD. During the Han dynasty, the Chinese were also the first to apply
hydraulic power (i.e. a
waterwheel) in working the bellows of the blast furnace. This was recorded in the year 31 AD, as an innovation by the Chinese mechanical engineer and politician
Du Shi,
Prefect of Nanyang. Although Du Shi was the first to apply water power to bellows in metallurgy, the first drawn and printed illustration of its operation with water power appeared in 1313 AD, in the Yuan dynasty era text called the
Nong Shu. In the 11th century, there is evidence of the production of steel in
Song China using two techniques: a "berganesque" method that produced inferior, heterogeneous steel and a precursor to the modern Bessemer process that utilized partial decarbonization via repeated forging under a cold blast. By the 11th century, there was a large amount of deforestation in China due to the iron industry's demands for charcoal. By this time however, the Chinese had learned to use
bituminous coke to replace charcoal, and with this switch in resources many acres of prime timberland in China were spared. Eastern Europe, especially the Cis-Ural region, shows the highest concentration of early and middle Bronze Age iron objects in western Eurasia, though most of these are thought to consist of meteoric Iron. A knife blade from the Catacomb culture dated to c. 2300 BC is thought to have been made from smelted iron. Early smelted iron finds from central Europe include an iron knife or sickle from Ganovce in Slovakia, possibly dating from the 18th-15th century BC, an iron ring from Vorwohlde in Germany dating from circa the 15th century BC, and an iron chisel from Heegermühle in Germany dating from circa 1000 BC. Smelted iron objects are known from Eastern Europe dating from after 1200 BC. In the
Carpathian Basin there is a significant increase in iron finds dating from the 10th century BC onwards, with some finds possibly dating as early as the 12th century BC. Iron swords have been found in central Europe dating from the 10th century BC; however, the Iron Age began in earnest with the
Hallstatt culture from 800 BC. Steel was produced from circa 800 BC as part of the production of swords, Evidence for iron metallurgy in Britain dates from the 10th century BC, with the beginning of the Iron Age dated to the 8th century BC. The production of high-carbon steel is attested in Britain from circa 490 BC. Iron metallurgy began to be practised in
Scandinavia during the later
Bronze Age from at least the 9th century BC, with evidence for steel production from 800–700 BC. Iron and steel artefacts, including high-carbon steel, were manufactured in northern Sweden, Finland and Norway (in the
Cap of the North) from c. 200–50 BC. High-carbon steel tools were produced in Iberia (Portugal) from c. 900 BC. From 500 BC the
La Tène culture saw a significant increase in iron production, with iron metallurgy also becoming common in southern Scandinavia. The spread of ironworking in Central and Western Europe is associated with
Celtic expansion. By the 1st century BC,
Noric steel was famous for its quality and sought after by the
Roman military. The annual output of iron in the
Roman Empire is estimated at 84,750
tonnes. The production of ultrahigh carbon steel is attested at the
Germanic site of
Heeten in the
Netherlands from the 2nd to 4th/5th centuries AD, in the
Late Roman Iron Age.
Sub-Saharan Africa Archaeometallurgical scientific knowledge and technological development originated in numerous centers of Africa; the centers of origin were located in
West Africa,
Central Africa, and
East Africa; consequently, as these origin centers are located within inner Africa, these archaeometallurgical developments are thus native African technologies. Iron metallurgical development occurred 2631 BCE – 2458 BCE at Lejja, in Nigeria, 2136 BCE – 1921 BCE at Obui, in Central Africa Republic, 1895 BCE – 1370 BCE at Tchire Ouma 147, in Niger, and 1297 BCE – 1051 BCE at Dekpassanware, in Togo. Inhabitants of Termit, in eastern
Niger, smelted iron around 1500 BC. In the region of the
Aïr Mountains in
Niger there are also signs of independent copper smelting between 2500 and 1500 BC. The process was not in a developed state, indicating smelting was not foreign. It became mature about 1500 BC. Archaeological sites containing iron smelting furnaces and slag have also been excavated at sites in the
Nsukka region of southeast
Nigeria in what is now
Igboland: dating to 2000 BC at the site of
Lejja (Eze-Uzomaka 2009) Similarly, smelting in bloomery-type furnaces appear in the
Nok culture of central Nigeria by about 550 BC and possibly a few centuries earlier. Iron and copper working spread southward through the continent, reaching the
Cape around AD 200. particularly in
Meroe where there are known to have been ancient bloomeries that produced metal tools for the Nubians and Kushites and produced surplus for their economy.
Medieval Islamic world Iron technology was further advanced by several
inventions in medieval Islam, during the
Islamic Golden Age. By the 11th century, every province throughout the
Muslim world had industrial mills in operation, from
Islamic Spain and
North Africa in the west to the
Middle East and
Central Asia in the east. There are also 10th-century references to
cast iron, as well as archeological evidence of
blast furnaces being used in the
Ayyubid and
Mamluk empires from the 11th century, thus suggesting a diffusion of Chinese metal technology to the Islamic world. One of the most famous steels produced in the medieval Near East was
Damascus steel used for
swordmaking, and mostly produced in
Damascus,
Syria, in the period from 900 to 1750. This was produced using the
crucible steel method, based on the earlier Indian
wootz steel. This process was adopted in the Middle East using locally produced steels. The exact process remains unknown, but it allowed
carbides to precipitate out as micro particles arranged in sheets or bands within the body of a blade. Carbides are far harder than the surrounding low carbon steel, so swordsmiths could produce an edge that cut hard materials with the precipitated carbides, while the bands of softer steel let the sword as a whole remain tough and flexible. A team of researchers based at the
Technical University of
Dresden that uses
X-rays and
electron microscopy to examine Damascus steel discovered the presence of
cementite nanowires and
carbon nanotubes. Peter Paufler, a member of the Dresden team, says that these nanostructures give Damascus steel its distinctive properties and are a result of the
forging process. ==Medieval and early modern Europe==