Finery forge

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Hearth (left) and trip hammer (centre) in a finery forge. In the back room (right) is a large pile of charcoal. PSM V38 D183 A forge trip hammer.jpg
Hearth (left) and trip hammer (centre) in a finery forge. In the back room (right) is a large pile of charcoal.

A finery forge is a forge used to produce wrought iron from pig iron by decarburization. The process involved liquifying cast iron in a fining hearth and removing carbon from the molten cast iron through oxidation. [1] Finery forges were used as early as 3rd century BC, based on archaeological evidence found at a site in Tieshengguo, China. [1] The finery forge process was replaced by the puddling process and the roller mill, both developed by Henry Cort in 1783-4, but not becoming widespread until after 1800. [2]

Forge workplace of a blacksmith

A forge is a type of hearth used for heating metals, or the workplace (smithy) where such a hearth is located. The forge is used by the smith to heat a piece of metal to a temperature where it becomes easier to shape by forging, or to the point where work hardening no longer occurs. The metal is transported to and from the forge using tongs, which are also used to hold the workpiece on the smithy's anvil while the smith works it with a hammer. Sometimes, such as when hardening steel or cooling the work so that it may be handled with bare hands, the workpiece is transported to the slack tub, which rapidly cools the workpiece in a large body of water. However, depending on the metal type, it may require an oil quench or a salt brine instead; many metals require more than plain water hardening. The slack tub also provides water to control the fire in the forge.

Wrought iron iron alloy with a very low carbon content

Wrought iron is an iron alloy with a very low carbon content in contrast to cast iron. It is a semi-fused mass of iron with fibrous slag inclusions, which gives it a "grain" resembling wood that is visible when it is etched or bent to the point of failure. Wrought iron is tough, malleable, ductile, corrosion-resistant and easily welded. Before the development of effective methods of steelmaking and the availability of large quantities of steel, wrought iron was the most common form of malleable iron. It was given the name wrought because it was hammered, rolled or otherwise worked while hot enough to expel molten slag. The modern functional equivalent of wrought iron is mild or low carbon steel. Neither wrought iron nor mild steel contain enough carbon to be hardenable by heating and quenching.

Pig iron iron alloy

Pig iron is an intermediate product of the iron industry, also known as crude iron, which is obtained by smelting iron ore in a blast furnace. Pig iron has a very high carbon content, typically 3.8–4.7%, along with silica and other constituents of dross, which makes it very brittle and not useful directly as a material except for limited applications.

Contents

History

A finery forge was used to refine wrought iron at least by the 3rd century BC in ancient China, based on the earliest archaeological specimens of cast and pig iron fined into wrought iron and steel found at the early Han Dynasty (202 BC – 220 AD) site at Tieshengguo. [1] Pigott speculates that the finery forge existed in the previous Warring States period (403–221 BC), because of the wrought iron items from China dating to that period and there was no documented evidence of the bloomery ever being used in China. [1] Wagner writes that in addition to the Han Dynasty hearths believed to be fining hearths, there is also pictoral evidence of the fining hearth from a Shandong tomb mural dated 1st to 2nd century AD, as well as a hint of written evidence in the 4th century AD Daoist text Taiping Jing . [3]

Cast iron iron or a ferrous alloy which has been liquefied then poured into a mould to solidify

Cast iron is a group of iron-carbon alloys with a carbon content greater than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its colour when fractured: white cast iron has carbide impurities which allow cracks to pass straight through, grey cast iron has graphite flakes which deflect a passing crack and initiate countless new cracks as the material breaks, and ductile cast iron has spherical graphite "nodules" which stop the crack from further progressing.

Steel alloy made by combining iron and other elements

Steel is an alloy of iron and carbon, and sometimes other elements. Because of its high tensile strength and low cost, it is a major component used in buildings, infrastructure, tools, ships, automobiles, machines, appliances, and weapons.

Warring States period Era in ancient Chinese history

The Warring States period was an era in ancient Chinese history characterized by warfare, as well as bureaucratic and military reforms and consolidation. It followed the Spring and Autumn period and concluded with the Qin wars of conquest that saw the annexation of all other contender states, which ultimately led to the Qin state's victory in 221 BC as the first unified Chinese empire, known as the Qin dynasty.

In Europe, the concept of the finery forge may have been evident as early as the 13th century. [4] However, it was perhaps not capable of being used to fashion plate armor until the 15th century, as described in conjunction with the waterwheel-powered blast furnace by the Florentine Italian engineer Antonio Averlino (c. 1400 - 1469). [5] The finery forge process began to be replaced in Europe from the late 18th century by others, of which puddling was the most successful, though some continued in use through the mid-19th century. The new methods used mineral fuel (coal or coke), and freed the iron industry from its dependence on wood to make charcoal.

Puddling (metallurgy) metallurgical process

Puddling was one step in one of the most important processes of making the first appreciable volumes of high-grade bar iron during the Industrial Revolution. In the original puddling technique, molten iron in a reverberatory furnace was stirred with rods, which were consumed in the process. It was one of the first processes for making bar iron without charcoal in Europe, although much earlier coal-based processes had existed in China. Eventually, the furnace would be used to make small quantities of specialty steels.

Coal A combustible sedimentary rock composed primarily of carbon

Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements; chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed if dead plant matter decays into peat and over millions of years the heat and pressure of deep burial converts the peat into coal. Vast deposits of coal originates in former wetlands—called coal forests—that covered much of the Earth's tropical land areas during the late Carboniferous (Pennsylvanian) and Permian times.

Coke (fuel) fuel

Coke is a grey, hard, and porous fuel with a high carbon content and few impurities, made by heating coal or oil in the absence of air — a destructive distillation process. It is an important industrial product, used mainly in iron ore smelting, but also as a fuel in stoves and forges when air pollution is a concern.

Types

Interior of the preserved Walloon forge in Osterbybruk, Uppland Vallonsmedjan interor.jpg
Interior of the preserved Walloon forge in Österbybruk, Uppland
Exterior of the remnants of a Basque forge Bolunburu burdinola.jpg
Exterior of the remnants of a Basque forge

There were several types of finery forges.

German forge

The dominant type in Sweden was the German forge, which had a single hearth that was used for all processes.

Sweden constitutional monarchy in Northern Europe

Sweden, formal name: the Kingdom of Sweden, is a Scandinavian Nordic country in Northern Europe. It borders Norway to the west and north and Finland to the east, and is connected to Denmark in the southwest by a bridge-tunnel across the Öresund Strait. At 450,295 square kilometres (173,860 sq mi), Sweden is the largest country in Northern Europe, the third-largest country in the European Union and the fifth largest country in Europe by area. The capital city is Stockholm. Sweden has a total population of 10.3 million of which 2.5 million have a foreign background. It has a low population density of 22 inhabitants per square kilometre (57/sq mi) and the highest urban concentration is in the central and southern half of the country.

Hearth brick- or stone-lined fireplace

In historic and modern usage, a hearth is a brick- or stone-lined fireplace, with or without an oven, used for heating and originally also used for cooking food. For centuries, the hearth was such an integral part of a home, usually its central and most important feature, that the concept has been generalized to refer to a homeplace or household, as in the terms "hearth and home" and "keep the home fires burning".

Walloon forge

In Swedish Uppland north of Stockholm and certain adjacent provinces, another kind known as the Walloon forge was used, mainly for the production of a particularly pure kind of iron known as oregrounds iron, which was exported to England to make blister steel. Its purity depended on the use of ore from the Dannemora mine. The Walloon forge was virtually the only kind used in Great Britain.

Uppland Place in Svealand, Sweden

Uppland is a historical province or landskap on the eastern coast of Sweden, just north of Stockholm, the capital. It borders Södermanland, Västmanland and Gästrikland. It is also bounded by lake Mälaren and the Baltic sea. On the small uninhabited island of Märket in the Baltic, Uppland has a very short and unusually shaped land border with Åland, an autonomous province of Finland.

Stockholm Capital city in Södermanland and Uppland, Sweden

Stockholm is the capital of Sweden and the most populous urban area in the Nordic countries; 965,232 people live in the municipality, approximately 1.6 million in the urban area, and 2.4 million in the metropolitan area. The city stretches across fourteen islands where Lake Mälaren flows into the Baltic Sea. Outside the city to the east, and along the coast, is the island chain of the Stockholm archipelago. The area has been settled since the Stone Age, in the 6th millennium BC, and was founded as a city in 1252 by Swedish statesman Birger Jarl. It is also the county seat of Stockholm County.

Wallonia Region of Belgium

Wallonia is a region of Belgium. As the southern portion of the country, Wallonia is primarily French-speaking, and accounts for 55% of Belgium's territory, but only a third of its population. The Walloon Region was not merged with the French Community of Belgium, which is the political entity responsible for matters related mainly to culture and education, because the French Community of Belgium encompasses both Wallonia and the majority French-Speaking Brussels-Capital Region.

The forge had two kinds of hearths, the finery to finish the product and the chafery to reheat the bloom that was the raw material of the process.

A chafery is a variety of hearth used in ironmaking for reheating a bloom of iron, in the course of its being drawn out into a bar of wrought iron.

Lancashire forge

Process

In the finery, a workman known as the "finer" remelted pig iron so as to oxidise the carbon (and silicon). This produced a lump of iron (with some slag) known as a bloom. This was consolidated using a water-powered hammer (see trip hammer) and returned to the finery.

The next stages were undertaken by the "hammerman", who in some iron-making areas such as South Yorkshire was also known as the "stringsmith", who heated his iron in a string-furnace. Because the bloom is highly porous, and its open spaces are full of slag, the hammerman's or stringsmith's tasks were to beat (work) the heated bloom with a hammer to drive the molten slag out of it, and then to draw the product out into a bar to produce what was known as anconies or bar iron. In order to do this, he had to reheat the iron, for which he used the chafery. The fuel used in the finery had to be charcoal (later coke), as impurities in any mineral fuel would affect the quality of the iron.

Slag

The waste product was allowed to cool in the hearth and removed as a "mosser". [6] In the Furness district they were often left as the capstone of a wall, particularly near Spark Bridge and Nibthwaite forges.

Mosser found near Newland Furnace Mosser 01.jpg
Mosser found near Newland Furnace
Mosser found near Newland Furnace Mosser, reverse side.jpg
Mosser found near Newland Furnace

Related Research Articles

Steelmaking process for producing steel from iron ore and scrap

Steelmaking is the process of producing steel from iron ore and/or scrap. In steelmaking, impurities such as nitrogen, silicon, phosphorus, sulfur and excess carbon(most important impurity) are removed from the sourced iron, and alloying elements such as manganese, nickel, chromium, carbon and vanadium are added to produce different grades of steel. Limiting dissolved gases such as nitrogen and oxygen and entrained impurities in the steel is also important to ensure the quality of the products cast from the liquid steel.

Blast furnace type of metallurgical furnace used for smelting to produce industrial metals

A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally pig iron, but also others such as lead or copper. Blast refers to the combustion air being "forced" or supplied above atmospheric pressure.

Cementation process

The cementation process is an obsolete technology for making steel by carburization of iron. Unlike modern steelmaking, it increased the amount of carbon in the iron. It was apparently developed before the 17th century. Derwentcote Steel Furnace, built in 1720, is the earliest surviving example of a cementation furnace. Another example in the UK is the cementation furnace in Doncaster Street, Sheffield.

Wealden iron industry

The Wealden iron industry was located in the Weald of south-eastern England. It was formerly an important industry, producing a large proportion of the bar iron made in England in the 16th century and most British cannon until about 1770. Ironmaking in the Weald used ironstone from various clay beds, and was fuelled by charcoal made from trees in the heavily wooded landscape. The industry in the Weald declined when ironmaking began to be fuelled by coke made from coal, which does not occur accessibly in the area.

Open hearth furnace historic steel producing technology

Open hearth furnaces are one of a number of kinds of furnace where excess carbon and other impurities are burnt out of pig iron to produce steel. Since steel is difficult to manufacture due to its high melting point, normal fuels and furnaces were insufficient and the open hearth furnace was developed to overcome this difficulty. Compared to Bessemer steel, which it displaced, its main advantages were that it did not expose the steel to excessive nitrogen, was easier to control, and it permitted the melting and refining of large amounts of scrap iron and steel.

Bloomery early form of iron smelter

A bloomery is a type of furnace once used widely for smelting iron from its oxides. The bloomery was the earliest form of smelter capable of smelting iron. A bloomery's product is a porous mass of iron and slag called a bloom. This mix of slag and iron in the bloom is termed sponge iron, which is usually consolidated and further forged into wrought iron. The bloomery has now largely been superseded by the blast furnace, which produces pig iron.

Trip hammer powered hammer

A trip hammer, also known as a tilt hammer or helve hammer, is a massive powered hammer used in:

Ironworks building or site where iron is smelted

An ironworks or iron works is a building or site where iron is smelted and where heavy iron and steel products are made. The term is both singular and plural, i.e. the singular of ironworks is ironworks.

Tuyere nozzle through which air is forced into a forge or blast furnace

A tuyere or tuyère is a tube, nozzle or pipe through which air is blown into a furnace or hearth.

Osmond process

Osmond iron was wrought iron made by a particular process. This is associated with the first European production of cast iron in furnaces such as Lapphyttan in Sweden.

Ferrous metallurgy

Ferrous metallurgy is the metallurgy of iron and its alloys. It began far back in prehistory. The earliest surviving iron artifacts, from the 4th millennium BC in Egypt, were made from meteoritic iron-nickel. It is not known when or where the smelting of iron from ores began, but by the end of the 2nd millennium BC iron was being produced from iron ores from Sub-Saharan Africa to China. The use of wrought iron was known by the 1st millennium BC, and its spread marked the Iron Age. During the medieval period, means were found in Europe of producing wrought iron from cast iron using finery forges. For all these processes, charcoal was required as fuel.

In metallurgy, refining consists of purifying an impure metal. It is to be distinguished from other processes such as smelting and calcining in that those two involve a chemical change to the raw material, whereas in refining, the final material is usually identical chemically to the original one, only it is purer. The processes used are of many types, including pyrometallurgical and hydrometallurgical techniques.

Cornwall Iron Furnace United States national historic site

Cornwall Iron Furnace is a designated National Historic Landmark that is administered by the Pennsylvania Historical and Museum Commission in Cornwall, Lebanon County, Pennsylvania in the United States. The furnace was a leading Pennsylvania iron producer from 1742 until it was shut down in 1883. The furnaces, support buildings and surrounding community have been preserved as a historical site and museum, providing a glimpse into Lebanon County's industrial past. The site is the only intact charcoal-burning iron blast furnace in its original plantation in the western hemisphere. Established by Peter Grubb in 1742, Cornwall Furnace was operated during the Revolution by his sons Curtis and Peter Jr. who were major arms providers to George Washington. Robert Coleman acquired Cornwall Furnace after the Revolution and became Pennsylvania's first millionaire. Ownership of the furnace and its surroundings was transferred to the Commonwealth of Pennsylvania in 1932.

Oregrounds iron

Oregrounds iron was a grade of iron that was regarded as the best grade available in 18th century England. The term was derived from the small Swedish city of Öregrund, the port from which the bar iron was shipped. The process to create it is known as the Walloon method.

Lancashire hearth

The Lancashire hearth was used to fine pig iron, removing carbon to produce wrought iron.

References

  1. 1 2 3 4 Pigott, Vincent C. (1999). The Archaeometallurgy of the Asian Old World. Philadelphia: University of Pennsylvania Museum of Archaeology and Anthropology. ISBN   0-924171-34-0, p. 186-187.
  2. Ayres, Robert (1989). "Technological Transformations and Long Waves" (PDF): 12.
  3. Wagner, Donald B. (2001). The State and the Iron Industry in Han China. Copenhagen: Nordic Institute of Asian Studies Publishing. ISBN   87-87062-83-6, pp. 80–83.
  4. Williams, Alan R. (2003). The Knight and the Blast Furnace: a History of the Metallurgy of Armor in the Middle Ages & the Early Modern Period. Leiden: Brill. ISBN   9789004124981, pp 883.
  5. Williams, Alan R. (2003). The Knight and the Blast Furnace: a History of the Metallurgy of Armor in the Middle Ages & the Early Modern Period. Leiden: Brill. ISBN   9789004124981, pp 883-84.
  6. http://www.fallingcreekironworks.org/Slagpage.html