s from the
Nong Shu, by
Wang Zhen in 1313 during China's
Yuan dynasty '', 1637 Cast iron has been found in
China dating to the 5th century BC, but the earliest extant blast furnaces in China date to the 1st century AD and in the West from the
High Middle Ages. They spread from the region around
Namur in
Wallonia (Belgium) in the late 15th century, being introduced to England in 1491. The fuel used in these was invariably charcoal. The successful substitution of coke for charcoal is widely attributed to British inventor
Abraham Darby in 1709. The efficiency of the process was further enhanced by the practice of preheating the combustion air (
hot blast), patented by British inventor
James Beaumont Neilson in 1828.
China Archaeological evidence shows that iron-smelting techniques and bloomeries were brought to China by nomadic peoples around 800 BC. Wrought iron artifacts were originally only found in the northwest, but by the 6th century BC, luxury items such as wrought iron swords and knives were widespread in China. Bloomery iron co-existed with blast furnaces and cast iron, which were invented shortly after wrought iron technology entered China, for quite some time. Cast iron pieces have been found alongside wrought iron in
Shanxi Province dating to the 9th-8th centuries BC, however it is uncertain if these cast iron pieces were accidental byproducts of the iron smelting process.
Adzes made using cast iron with a decarburised layer of steel have been found in
Luoyang dating to the 5th century BC. Cast iron farming tools that had undergone an annealing process to decrease brittleness were found in burials and smelting cites dating to the 4th century BC. Bloomery iron disappeared in China after the 3rd century AD with the exception of Xinjiang, where bloomery iron objects could be found as late as the 9th century AD. In China, blast furnaces produced cast iron, which was then either converted into finished implements in a cupola furnace, or turned into wrought iron in a fining hearth. employing workforces of over 200 men in iron smelters from the 3rd century onward, the earliest blast furnaces constructed were attributed to the
Han dynasty in the 1st century AD. These early furnaces had clay walls and used
phosphorus-containing minerals as a
flux. Chinese blast furnaces ranged from around two to ten meters in height, depending on the region. The largest ones were found in modern
Sichuan and
Guangdong, while the 'dwarf" blast furnaces were found in
Dabieshan. In construction, they are both around the same level of technological sophistication. The effectiveness of the Chinese human and horse powered blast furnaces was enhanced during this period by the engineer
Du Shi (c. AD 31), who applied the power of
waterwheels to
piston-
bellows in forging cast iron. Early water-driven reciprocators for operating blast furnaces were built according to the structure of horse powered reciprocators that already existed. That is, the circular motion of the wheel, be it horse driven or water driven, was transferred by the combination of a
belt drive, a crank-and-connecting-rod, other
connecting rods, and various shafts, into the reciprocal motion necessary to operate push bellows. Donald Wagner suggests that early blast furnace and cast iron production evolved from furnaces used to melt
bronze. Certainly, though, iron was essential to military success by the time the
State of Qin had unified China (221 BC). Usage of the blast and cupola furnace remained widespread during the
Song and
Tang dynasties. By the 11th century, the
Song dynasty Chinese iron industry made a switch of resources from
charcoal to
coke in casting iron and steel, sparing thousands of acres of woodland from felling. This may have happened as early as the 4th century AD. The primary advantage of the early blast furnace was in large scale production and making iron implements more readily available to peasants. Cast iron is more brittle than wrought iron or steel, which required additional fining and then cementation or co-fusion to produce, but for menial activities such as farming it sufficed. By using the blast furnace, it was possible to produce larger quantities of tools such as ploughshares more efficiently than the bloomery. In areas where quality was important, such as warfare, wrought iron and steel were preferred. Nearly all Han period weapons are made of wrought iron or steel, with the exception of axe-heads, of which many are made of cast iron. Blast furnaces were also later used to produce
gunpowder weapons such as cast iron
bomb shells and cast iron
cannons during the
Song dynasty.
Medieval Europe The simplest
forge, known as the Corsican. Examples of improved bloomeries are the Stuckofen, sometimes called wolf-furnace, which remained until the beginning of the 19th century. Instead of using natural draught, air was pumped in by a
trompe, resulting in better quality iron and an increased capacity. This pumping of air in with bellows is known as
cold blast, and it increases the
fuel efficiency of the bloomery and improves yield. They can also be built bigger than natural draught bloomeries.
Oldest European blast furnaces The oldest known blast furnaces in the West were built in
Durstel in
Switzerland, the Märkische
Sauerland in
Germany, and at
Lapphyttan in
Sweden, where the complex was active between 1205 and 1300. At Noraskog in the Swedish parish of Järnboås, traces of even earlier blast furnaces have been found, possibly from around 1100. These early blast furnaces, like the
Chinese examples, were very inefficient compared to those used today. The iron from the Lapphyttan complex was used to produce balls of
wrought iron known as
osmonds, and these were traded internationally – a possible reference occurs in a treaty with
Novgorod from 1203 and several certain references in accounts of English customs from the 1250s and 1320s. Other furnaces of the 13th to 15th centuries have been identified in
Westphalia. The technology required for blast furnaces may have either been transferred from China, or may have been an indigenous innovation.
Al-Qazvini in the 13th century and other travellers subsequently noted an iron industry in the
Alburz Mountains to the south of the
Caspian Sea. This is close to the
silk route, so that the use of technology derived from China is conceivable. Much later descriptions record blast furnaces about three metres high. As the
Varangian Rus' people from
Scandinavia traded with the Caspian (using their
Volga trade route), it is possible that the technology reached Sweden by this means. The Vikings are known to have used double bellows, which greatly increases the volumetric flow of the blast. The Caspian region may also have been the source for the design of the furnace at
Ferriere, described by
Filarete, involving a water-powered bellows at Semogo in
Valdidentro in northern Italy in 1226. In a two-stage process the molten iron was tapped twice a day into water, thereby granulating it.
Cistercian contributions The General Chapter of the
Cistercian monks spread some technological advances across Europe. This may have included the blast furnace, as the Cistercians are known to have been skilled
metallurgists. According to Jean Gimpel, their high level of industrial technology facilitated the diffusion of new techniques: "Every monastery had a model factory, often as large as the church and only several feet away, and waterpower drove the machinery of the various industries located on its floor." Iron ore deposits were often donated to the monks along with forges to extract the iron, and after a time surpluses were offered for sale. The Cistercians became the leading iron producers in
Champagne, France, from the mid-13th century to the 17th century, also using the
phosphate-rich slag from their furnaces as an agricultural
fertilizer. Archaeologists are still discovering the extent of Cistercian technology. At
Laskill, an outstation of
Rievaulx Abbey and the only medieval blast furnace so far identified in
Britain, the slag produced was low in iron content. Slag from other furnaces of the time contained a substantial concentration of iron, whereas Laskill is believed to have produced cast iron quite efficiently. Its date is not yet clear, but it probably did not survive until
Henry VIII's
Dissolution of the Monasteries in the late 1530s, as an agreement (immediately after that) concerning the "smythes" with the
Earl of Rutland in 1541 refers to blooms. Nevertheless, the means by which the blast furnace spread in medieval Europe has not finally been determined.
Origin and spread of early modern blast furnaces Due to the increased demand for iron for casting cannons, the blast furnace came into widespread use in France in the mid 15th century. The direct ancestor of those used in France and England was in the
Namur region, in what is now
Wallonia (Belgium). From there, they spread first to the
Pays de Bray on the eastern boundary of
Normandy and from there to the
Weald of
Sussex, where the first furnace (called Queenstock) in
Buxted was built in about 1491, followed by one at
Newbridge in
Ashdown Forest in 1496. They remained few in number until about 1530 but many were built in the following decades in the Weald, where the iron industry perhaps reached its peak about 1590. Most of the pig iron from these furnaces was taken to
finery forges for the production of
bar iron. The first British furnaces outside the Weald appeared during the 1550s, and many were built in the remainder of that century and the following ones. The output of the industry probably peaked about 1620, and was followed by a slow decline until the early 18th century. This was apparently because it was more economic to import iron from
Sweden and elsewhere than to make it in some more remote British locations. Charcoal that was economically available to the industry was probably being consumed as fast as the wood to make it grew. The first blast furnace in
Russia opened in 1637 near
Tula and was called the Gorodishche Works. The blast furnace spread from there to central Russia and then finally to the
Urals.
Coke blast furnaces in
Madeley, England , 1930 first commissioned in 1715 by order of
Peter the Great with the help of Holland masters. In 1709, at
Coalbrookdale in Shropshire, England,
Abraham Darby began to fuel a blast furnace with
coke instead of
charcoal. Coke's initial advantage was its lower cost, mainly because making coke required much less labor than cutting trees and making charcoal, but using coke also overcame localized shortages of wood, especially in Britain and elsewhere in Europe. Metallurgical grade coke will bear heavier weight than charcoal, allowing larger furnaces. A disadvantage is that coke contains more impurities than charcoal, with sulfur being especially detrimental to the iron's quality. Coke's impurities were more of a problem before hot blast reduced the amount of coke required and before furnace temperatures were hot enough to make slag from limestone free flowing. (Limestone ties up sulphur. Manganese may also be added to tie up sulphur.) Coke iron was initially only used for
foundry work, making pots and other cast iron goods. Foundry work was a minor branch of the industry, but Darby's son built a new furnace at nearby Horsehay, and began to supply the owners of
finery forges with coke pig iron for the production of bar iron. Coke pig iron was by this time cheaper to produce than charcoal pig iron. The use of a coal-derived fuel in the iron industry was a key factor in the British
Industrial Revolution. However, in many areas of the world charcoal was cheaper while coke was more expensive even after the Industrial Revolution: e. g., in the US charcoal-fueled iron production fell in share to about a half but still continued to increase in absolute terms until , while in
João Monlevade in the
Brazilian Highlands charcoal-fired blast furnaces were built as late as the 1930s and only phased out in 2000. Darby's original blast furnace has been archaeologically excavated and can be seen in situ at Coalbrookdale, part of the
Ironbridge Gorge Museums. Cast iron from the furnace was used to make
girders for the world's first cast iron bridge in 1779.
The Iron Bridge crosses the
River Severn at Coalbrookdale and remains in use for pedestrians. (1794-), depicted in a miniature in the
Deutsches Museum Steam-powered blast The steam engine was applied to power blast air, overcoming a shortage of water power in areas where coal and iron ore were located. This was first done at Coalbrookdale where a
steam engine replaced a horse-powered pump in 1742. Such engines were used to pump water to a reservoir above the furnace. The first engines used to blow cylinders directly was supplied by
Boulton and Watt to
John Wilkinson's
New Willey Furnace. This powered a
cast iron blowing cylinder, which had been invented by his father
Isaac Wilkinson. He patented such cylinders in 1736, to replace the leather bellows, which wore out quickly. Isaac was granted a second patent, also for blowing cylinders, in 1757. The steam engine and cast iron blowing cylinder led to a large increase in British iron production in the late 18th century. Hot blast was patented by
James Beaumont Neilson at
Wilsontown Ironworks in Britain in 1828. Within a few years of the introduction, hot blast was developed to the point where fuel consumption was cut by one-third using coke or two-thirds using coal, while furnace capacity was also significantly increased. Within a few decades, the practice was to have a "stove" as large as the furnace next to it into which the waste gas (containing CO) from the furnace was directed and burnt. The resultant heat was used to preheat the air blown into the furnace. Hot blast enabled the use of raw
anthracite coal, which was difficult to light, in the blast furnace. Anthracite was first tried successfully by George Crane at
Ynyscedwyn Ironworks in south Wales in 1837. It was taken up in America by the
Lehigh Crane Iron Company at
Catasauqua, Pennsylvania, in 1839. Anthracite use declined when very high capacity blast furnaces requiring coke were built in the 1870s. ==Modern applications of the blast furnace==