Editing Wrought iron (section)

==Terminology==
The word "wrought" is an archaic past participle of the verb "to work", and so "wrought iron" literally means "worked iron".<ref>{{cite web |title=Wrought |url=https://www.merriam-webster.com/dictionary/wrought |website=Dictionary by Merriam Webster: America's most trusted on-line dictionary |publisher=Merriam-Webster |access-date=27 November 2020}}</ref> Wrought iron is a general term for the commodity, but is also used more specifically for finished iron goods, as manufactured by a [[blacksmith]]. It was used in that narrower sense in [[Great Britain|British]] [[Customs]] records, such manufactured iron was subject to a higher rate of duty than what might be called "unwrought" iron. [[Cast iron]], unlike wrought iron, is brittle and cannot be worked either hot or cold.

In the 17th, 18th, and 19th centuries, wrought iron went by a wide variety of terms according to its form, origin, or quality.

While the [[bloomery]] process produced wrought iron directly from ore, [[cast iron]] or [[pig iron]] were the starting materials used in the [[finery forge]] and [[puddling furnace]]. Pig iron and cast iron have higher carbon content than wrought iron, but have a lower melting point than iron or steel. Cast and especially pig iron have excess slag which must be at least partially removed to produce quality wrought iron. At [[foundry|foundries]] it was common to blend scrap wrought iron with cast iron to improve the physical properties of castings.

For several years after the introduction of Bessemer and open hearth steel, there were different opinions as to what differentiated iron from steel; some believed it was the chemical composition and others that it was whether the iron heated sufficiently to melt and "fuse". Fusion eventually became generally accepted as relatively more important than composition below a given low carbon concentration.<ref name="Misa1995">{{cite book |first=Thomas J. |last=Misa |title=A Nation of Steel: The Making of Modern America, 1865–1925 |url=https://archive.org/details/nationofsteelmak00misa |url-access=registration |location=Baltimore |publisher=Johns Hopkins University Press |year=1995|isbn=9780801849671 }}</ref>{{rp|32–39}} Another difference is that steel can be hardened by [[heat treating]].

Historically, wrought iron was known as "commercially pure iron";<ref name="Imhoff1917">{{cite journal |last=Imhoff |first=Wallace G. |title=Puddle Cinder as a Blast Furnace Iron Ore |journal=Journal of the Cleveland Engineering Society |volume=9 |issue=621.76 |pages=332 |year=1917 |url=https://books.google.com/books?id=OA_OAAAAMAAJ}}</ref><ref name="Scoffern1869">{{cite book |last=Scoffern |first=John |author-link=John Scoffern |title=The useful metals and their alloys |page=6 |publisher=Houlston & Wright |year=1869 |edition=5th |url=https://books.google.com/books?id=4Ik1AAAAMAAJ}}</ref> however, it no longer qualifies because current standards for commercially pure iron require a carbon content of less than 0.008 [[wt%]].<ref name="McArthur2004">{{cite book |last1=McArthur |first1=Hugh |last2=Spalding |first2=Duncan |title=Engineering materials science: properties, uses, degradation and remediation |page=338 |publisher=Horwood Publishing |year=2004 |url=https://books.google.com/books?id=7dwAaOqp69wC |isbn=978-1-898563-11-2}}</ref><ref name="Campbell2008">{{cite book |last=Campbell |first=Flake C. |title=Elements of Metallurgy and Engineering Alloys |publisher=ASM International |page=154 |year=2008 |url=https://books.google.com/books?id=6VdROgeQ5M8C |isbn=978-0-87170-867-0}}</ref>

===Types and shapes===
Bar iron is a generic term sometimes used to distinguish it from cast iron. It is the equivalent of an ingot of cast metal, in a convenient form for handling, storage, shipping and further working into a finished product.

The bars were the usual product of the [[finery forge]], but not necessarily made by that process:
* Rod iron—cut from flat bar iron in a [[slitting mill]] provided the raw material for spikes and nails.
* Hoop iron—suitable for the hoops of barrels, made by passing rod iron through rolling dies.
* Plate iron—sheets suitable for use as [[boiler]] plate.
* [[Blackplate]]—sheets, perhaps thinner than plate iron, from the black rolling stage of [[tinplate]] production.
* Voyage iron—narrow flat bar iron, made or cut into bars of a particular weight, a commodity for sale in [[Africa]] for the [[Atlantic slave trade]]. The number of bars per ton gradually increased from 70 per ton in the 1660s to 75–80 per ton in 1685 and "near 92 to the ton" in 1731.<ref name="Evans2007">{{cite book |first1=C. |last1=Evans |first2=G. |last2=Rydén |title=Baltic Iron in the Atlantic World in the Eighteenth Century |publisher=Brill |location=Boston, Mass. |year=2007 |url=https://books.google.com/books?id=GEh9PKIZl_4C |isbn=9789004161535}}</ref>{{rp|163–172}}

===Origin===
* Charcoal iron—until the end of the 18th century, wrought iron was smelted from ore using charcoal, by the [[bloomery]] process. Wrought iron was also produced from [[pig iron]] using a [[finery forge]] or in a [[Lancashire hearth]]. The resulting metal was highly variable, both in chemistry and slag content.
* [[Puddling furnace|Puddled iron]]—the [[puddling (metallurgy)|puddling process]] was the first large-scale process to produce wrought iron. In the puddling process, pig iron is refined in a [[reverberatory furnace]] to prevent contamination of the iron from the sulfur in the coal or coke. The molten pig iron is manually stirred, exposing the iron to atmospheric oxygen, which decarburizes the iron. As the iron is stirred, globs of wrought iron are collected into balls by the stirring rod (rabble arm or rod) and those are periodically removed by the puddler. Puddling was patented in 1784 and became widely used after 1800. By 1876, annual production of puddled iron in the UK alone was over 4 million tons. Around that time, the [[open hearth furnace]] was able to produce steel of suitable quality for structural purposes, and wrought iron production went into decline.
* [[Oregrounds iron]]—a particularly pure grade of bar iron made ultimately from [[iron ore]] from the [[Dannemora, Sweden|Dannemora]] mine in [[Sweden]]. Its most important use was as the raw material for the [[cementation process]] of steelmaking.
* Danks iron—originally iron imported to Great Britain from [[Gdańsk]], but in the 18th century more probably the kind of iron (from eastern Sweden) that once came from Gdańsk.
* Forest iron—iron from the English [[Forest of Dean]], where [[hematite|haematite]] ore enabled tough iron to be produced.
* Lukes iron—iron imported from [[Liège]], whose Dutch name is "Luik".<ref name="Childs1981">{{cite periodical |first=W. R. |last=Childs |title=England's Iron trade in the Fifteenth Century |periodical=Economic History Review |series=2nd |year=1981 |pages=25–47}}</ref>
* Ames iron or amys iron—another variety of iron imported to England from northern Europe. Its origin has been suggested to be [[Amiens]], but it seems to have been imported from [[Flanders]] in the 15th century and [[Holland]] later, suggesting an origin in the [[Rhine]] valley. Its origins remain controversial.<ref name="Childs1981" />
* Botolf iron or Boutall iron—from [[Bytów]] (Polish [[Pomerania]]) or [[Bytom]] (Polish [[Silesia]]).<ref name="Childs1981" />
* Sable iron (or Old Sable)—iron bearing the mark (a [[sable]]) of the [[Demidov]] family of [[Russia]]n [[ironmaster]]s, one of the better brands of [[Russia iron|Russian iron]].<ref>{{cite book |first=A. |last=Kahan |title=The Plow, the Hammer, and the Knout: an economic history of eighteenth century Russia |url=https://archive.org/details/plowhammerknoute0000kaha |url-access=registration |publisher=University of Chicago Press |year=1985|isbn=9780226422534 }}<!-- page needed --></ref>

===Quality===
;Tough iron: Also spelled "tuf", is not brittle and is strong enough to be used for tools.
;Blend iron: Made using a mixture of different types of [[pig iron]].
;Best iron: Iron put through several stages of piling and rolling to reach the stage regarded (in the 19th century) as the best quality.
;Marked bar iron: Made by members of the [[Marked Bar Association]] and marked with the maker's brand mark as a sign of its quality.<ref>{{cite periodical |first=Norman |last=Mutton |title=The marked bar association: price regulation in the Black Country wrought iron trade |periodical=West Midland Studies |edition=9th |year=1976 |pages=2–8}}</ref>

===Defects===
Wrought iron is a form of commercial iron containing less than 0.10% of carbon, less than 0.25% of impurities total of sulfur, phosphorus, silicon and manganese, and less than 2% slag by weight.<ref name="Marks'">{{cite book |last1=Baumeister |last2=Avallone |last3=Baumeister |title=Marks' Standard Handbook for Mechanical Engineers |edition=8th |publisher=McGraw Hill |isbn=978-0-07-004123-3 |pages=6–18, 17|year=1978 }}</ref><ref>{{cite encyclopedia |entry=wrought iron |encyclopedia=Encyclopædia Britannica |edition=2009 Deluxe |location=Chicago |year=2009}}</ref>

Wrought iron is ''[[redshort]]'' or ''hot short'' if it contains sulfur in excess quantity. It has sufficient tenacity when cold, but cracks when bent or finished at a red heat.<ref name="Gordon1996" />{{rp|7}} Hot short iron was considered unmarketable.<ref name="Tylecote1992" />

''Cold short'' iron, also known as ''coldshear'', ''colshire'', contains excessive phosphorus. It is very brittle when cold and cracks if bent.<ref name="Gordon1996" />{{rp|7, 215}} It may, however, be worked at high temperature. Historically, coldshort iron was considered sufficient for [[nail (engineering)|nails]].

Phosphorus is not necessarily detrimental to iron. Ancient Near Eastern smiths did not add lime to their furnaces. The absence of [[CaO|calcium oxide]] in the slag, and the deliberate use of wood with high phosphorus content during the smelting, induces a higher phosphorus content (typically <0.3%) than in modern iron (<0.02–0.03%).<ref name="Tylecote1992" /><ref>{{cite web |url=http://www.totalmateria.com/page.aspx?ID=CheckArticle&site=kts&NM=211 |website=Total Materia |title=Effect of Phosphorus on the Properties of Carbon Steels: Part 1 |date=October 2007 |access-date=27 October 2019}}</ref> Analysis of the [[Iron Pillar of Delhi]] gives 0.11% in the iron.<ref name="Tylecote1992" />{{rp|69}} The included slag in wrought iron also imparts corrosion resistance.

Antique [[music wire]], manufactured at a time when mass-produced carbon-steels were available, was found to have low carbon and high phosphorus; iron with high phosphorus content, normally causing brittleness when worked cold, was easily [[wire drawing|drawn]] into music wires.<ref name=sciphos>{{cite journal |first=Martha |last=Goodway |title=Phosphorus in antique iron music wire |journal=Science |volume=236 |date=May 1987 |pages=927–932 |issue=4804 |bibcode=1987Sci...236..927G |doi=10.1126/science.236.4804.927 |pmid=17812747 |s2cid=45929352 }}</ref> Although at the time phosphorus was not an easily identified component of iron, it was hypothesized that the type of iron had been rejected for conversion to steel but excelled when tested for drawing ability.<ref name=sciphos/>