Editing Cast iron (section)

==History==
{{main|History of ferrous metallurgy}}
{{Missing information|history of cast iron use in cookware|date=May 2025}}
[[File:Chengqiao artifact no. 35 cast iron.png|thumb|Cast-iron artifact dated from 8th century BC found in Jiangsu, China]]
[[File:Eastern Han Blast Furnace Blower Model (10340434095).jpg|thumb|Diorama model of a [[Han dynasty]] blast furnace blower]]
[[File:Iron Lion of Cangzhou 2007.jpg|thumb|The [[Iron Lion of Cangzhou]], the largest surviving cast-iron artwork from [[China]], 953 AD, [[Later Zhou]] period]]
[[File:Cast fe and cu dwv piping.jpg|thumb|Cast-iron "no hub" [[drain-waste-vent system|drain waste and vent]] (DWV) piping]]
[[File:Fluegel-Rahmen.jpg|thumb|upright|Cast iron "harp" of a [[grand piano]]]]

Cast iron and [[wrought iron]] can be produced unintentionally when smelting copper using iron ore as a flux.<ref>{{cite book|title=A History of Metallurgy, Second Edition |last=Tylecote |first=R. F. |year=  1992|publisher =Maney Publishing, for the Institute of Materials |location= London|isbn=978-0901462886}}</ref>{{rp|47–48}}

The earliest cast-iron artifacts date to the 8th century BC, and were discovered by archaeologists in what is now modern [[Luhe County]], Jiangsu in China during the [[Warring States period]]. This is based on an analysis of the artifact's microstructures.<ref name="Wagner">{{cite book|author=Wagner, Donald B. |title=Iron and Steel in Ancient China|year=1993|publisher=BRILL|isbn=978-90-04-09632-5|pages=335–340}}</ref>

Because cast iron is comparatively brittle, it is not suitable for purposes where a sharp edge or flexibility is required. It is strong under compression, but not under tension. Cast iron was invented in China in the 8th century BC and poured into molds to make ploughshares and pots as well as weapons and pagodas.<ref name="Wagner2">{{cite book|author=Wagner, Donald B.|title=Science and Civilisation in China: Volume 5, Chemistry and Chemical Technology, Part 11, Ferrous Metallurgy|date= May 2008|publisher=Cambridge University Press|isbn=978-0-521-87566-0|pages=159–169}}</ref> Although steel was more desirable, cast iron was cheaper and thus was more commonly used for implements in ancient China, while wrought iron or steel was used for weapons.<ref name="Wagner"/> The Chinese developed a method of [[Annealing (metallurgy)|annealing]] cast iron by keeping hot castings in an oxidizing atmosphere for a week or longer in order to burn off some carbon near the surface in order to keep the surface layer from being too brittle.<ref>{{cite book|title=The Genius of China: 3000 years of science, discovery and invention |last1=Temple |first1= Robert |year= 1986|publisher = Simon and Schuster|location=New York}} Based on the works of Joseph Needham></ref>{{rp|43}}

Deep within the [[Congo Basin|Congo]] region of the Central African forest, blacksmiths invented sophisticated furnaces capable of high temperatures over 1000 years ago. There are countless examples of welding, soldering, and cast iron created in crucibles and poured into molds. These techniques were employed for the use of composite tools and weapons with cast iron or steel blades and soft, flexible wrought iron interiors. Iron wire was also produced. Numerous testimonies were made by early European missionaries of the [[Luba people]] pouring cast iron into molds to make hoes.<ref>{{citation |url=https://unesdoc.unesco.org/ark:/48223/pf0000133843/PDF/133843eng.pdf.multi |title=The Origins of Iron Metallurgy in Africa |editor-last=Bocoum |editor-first=Hamady |publisher=UNESCO Publishing |location=Paris |date=2004 |isbn=92-3-103807-9 |pages=130–131}}</ref> Metallographic analysis of Luba artifacts also indicates the use of cast iron.<ref>{{cite journal |last1=Childs |title=Style, technology and iron furnace in Bantu-speaking Africa |journal=Of Anthropological Archaeology |date=1991 |volume=10 |page=332-359|doi=10.1016/0278-4165(91)90006-J }}</ref>

The technology of cast iron was transferred to the West from China.<ref name = "Wagner 2008">Wagner, Donald B. (2008). ''Science and Civilisation in China: 5. Chemistry and Chemical Technology: part 11 Ferrous Metallurgy''. Cambridge University Press, pp. 349–51.</ref> [[Zakariya al-Qazwini|Al-Qazvini]] in the 13th century and other travellers subsequently noted an iron industry in the [[Alborz|Alburz]] Mountains to the south of the [[Caspian Sea]]. This is close to the [[silk route]], thus the use of cast-iron technology being derived from China is conceivable.<ref name = "Wagner 2008"/> Upon its introduction to the West in the 15th century it was used for [[cannon]] and [[round shot|shot]]. [[Henry VIII]] (reigned 1509–1547) initiated the casting of cannon in England. Soon, English iron workers using [[blast furnace]]s developed the technique of producing cast-iron cannons, which, while heavier than the prevailing bronze cannons, were much cheaper and enabled England to arm her navy better.

Cast-iron pots were made at many English blast furnaces at the time. In 1707, [[Abraham Darby I|Abraham Darby]] patented a new method of making pots (and kettles) thinner and hence cheaper than those made by traditional methods. This meant that his [[Coalbrookdale]] furnaces became dominant as suppliers of pots, an activity in which they were joined in the 1720s and 1730s by a small number of other [[coke (fuel)|coke]]-fired blast furnaces.

Application of the steam engine to power blast bellows (indirectly by pumping water to a waterwheel) in Britain, beginning in 1743 and increasing in the 1750s, was a key factor in increasing the production of cast iron, which surged in the following decades.  In addition to overcoming the limitation on water power, the steam-pumped-water powered blast gave higher furnace temperatures which allowed the use of higher lime ratios, enabling the conversion from charcoal (supplies of wood for which were inadequate) to coke.<ref>{{cite book|title=A History of Metallurgy, Second Edition |last=Tylecote |first=R. F.|year= 1992|publisher= Maney Publishing, for the Institute of Materials |location= London|isbn=978-0901462886}}</ref>{{rp|122}}

The [[ironmaster]]s of the [[Weald]] continued producing cast irons until the 1760s, and armament was one of the main uses of irons after the [[English Restoration|Restoration]].

===Cast-iron bridges===
{{see also|The Iron Bridge}}
{{Unreferenced section|date=February 2021}}
The use of cast iron for structural purposes began in the late 1770s, when [[Abraham Darby III]] built [[The Iron Bridge]], although short beams had already been used, such as in the blast furnaces at Coalbrookdale. Other inventions followed, including one patented by [[Thomas Paine]]. Cast-iron bridges became commonplace as the [[Industrial Revolution]] gathered pace. [[Thomas Telford]] adopted the material for his bridge upstream at [[Buildwas]], and then for [[Longdon-on-Tern Aqueduct]], a canal trough [[Navigable aqueduct|aqueduct]] at [[Longdon-on-Tern]] on the [[Shrewsbury Canal]]. It was followed by the [[Chirk Aqueduct]] and the [[Pontcysyllte Aqueduct]], both of which remain in use following the recent restorations.

The best way of using cast iron for bridge construction was by using [[Arch bridge|arches]], so that all the material is in compression. Cast iron, again like masonry, is very strong in compression. Wrought iron, like most other kinds of iron and indeed like most metals in general, is strong in tension, and also tough – resistant to fracturing. The relationship between wrought iron and cast iron, for structural purposes, may be thought of as analogous to the relationship between wood and stone.

Cast-iron beam bridges were used widely by the early railways, such as the Water Street Bridge in 1830 at the [[Manchester]] terminus of the [[Liverpool and Manchester Railway]], but problems with its use became all too apparent when a new bridge carrying the [[Chester and Holyhead Railway]] across the [[River Dee (United Kingdom)|River Dee]] in [[Chester]] collapsed killing five people in May 1847, less than a year after it was opened. The [[Dee bridge disaster]] was caused by excessive loading at the centre of the beam by a passing train, and many similar bridges had to be demolished and rebuilt, often in [[wrought iron]]. The bridge had been badly designed, being trussed with wrought iron straps, which were wrongly thought to reinforce the structure. The centres of the beams were put into bending, with the lower edge in tension, where cast iron, like [[masonry]], is very weak.

Nevertheless, cast iron continued to be used in inappropriate structural ways, until the [[Tay Rail Bridge]] disaster of 1879 cast serious doubt on the use of the material. Crucial lugs for holding tie bars and struts in the Tay Bridge had been cast integral with the columns, and they failed in the early stages of the accident. In addition, the bolt holes were also cast and not drilled. Thus, because of casting's draft angle, the tension from the tie bars was placed on the hole's edge rather than being spread over the length of the hole. The replacement bridge was built in wrought iron and steel.

Further bridge collapses occurred, however, culminating in the [[Norwood Junction rail accident]] of 1891. Thousands of cast-iron rail [[Glossary of rail terminology#U|underbridges]] were eventually replaced by steel equivalents by 1900 owing to the widespread concern about cast iron under bridges on the rail network in Britain.

<gallery mode="packed">
File:Ironbridge 6.jpg|[[The Iron Bridge]] over the [[River Severn]] at Coalbrookdale, England (finished 1779)
File:Eglinton Castle & Tournament Bridge 1884.jpg|The [[Eglinton Tournament Bridge]] (completed c1845), [[North Ayrshire]], [[Scotland]], built from cast iron
File:Image-Taybridge01.jpg|Original Tay Bridge from the north (finished 1878)
File:Tay bridge down.JPG|Fallen Tay Bridge from the north
</gallery>

===Buildings===
{{Main|Cast-iron architecture}}

Cast-iron [[column]]s, pioneered in mill buildings, enabled architects to build multi-storey buildings without the enormously thick walls required for masonry buildings of any height. They also opened up floor spaces in factories, and sight lines in churches and auditoriums. By the mid 19th century, cast iron columns were common in warehouse and industrial buildings, combined with wrought or cast iron beams, eventually leading to the development of steel-framed skyscrapers. Cast iron was also used sometimes for decorative facades, especially in the United States, and the [[SoHo, Manhattan|Soho]] district of New York has numerous examples. It was also used occasionally for complete prefabricated buildings, such as the historic [[Iron Building (Watervliet Arsenal)|Iron Building]] in [[Watervliet, New York]].{{Citation needed|date=March 2021}}

===Textile mills===
Another important use was in [[Cotton mill|textile mill]]s. The air in the mills contained flammable fibres from the cotton, [[hemp]], or [[wool]] being spun. As a result, textile mills had an alarming propensity to burn down. The solution was to build them completely of non-combustible materials, and it was found convenient to provide the building with an iron frame, largely of cast iron, replacing flammable wood. The first such building was at [[Ditherington]] in [[Shrewsbury]], Shropshire.<ref name="Historic England">{{cite web | title=Ditherington Flax Mill: Spinning Mill, Shrewsbury – 1270576 | website=Historic England | url=https://historicengland.org.uk/listing/the-list/list-entry/1270576 | access-date=2020-06-29}}</ref> Many other warehouses were built using cast-iron columns and beams, although faulty designs, flawed beams or overloading sometimes caused building collapses and structural failures.{{Citation needed|date=March 2021}}

During the Industrial Revolution, cast iron was also widely used for frame and other fixed parts of machinery, including spinning and later weaving machines in textile mills. Cast iron became widely used, and many towns had [[foundry|foundries]] producing industrial and agricultural machinery.<ref>{{Citation needed|date=March 2021}}</ref>