Editing Cementation process

{{Short description|Obsolete steel-making process}}
{{Distinguish|Cementation (metallurgy)|Carburizing}}
[[File:Four cementation anglais.jpg|thumb|200px|Cementation furnace]]
The '''cementation process''' is an [[Obsolescence|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, Sheffield|cementation furnace in Doncaster Street, Sheffield]].

==Origins==
The process was described in a treatise published in [[Prague]] in 1574.  It was invented by Johann Nussbaum of [[Magdeburg]], who began operations at [[Nuremberg]] (with partners) in 1601.  The process was patented in [[England]] by William Ellyot and Mathias Meysey in 1614.<ref>K. C. Barraclough, ''Steel before Bessemer: I Blister Steel: the birth of an industry'' (The Metals Society, London, 1984), 48-52.</ref>  At that date, the "invention" could consist merely of the introduction of a new industry or product, or even a mere [[monopoly]].  They evidently soon transferred the patent to Sir [[Basil Brooke (metallurgist)|Basil Brooke]], but he was forced to surrender it in 1619.  A clause in the patent prohibiting the import of [[steel]] was found to be undesirable because he could not supply as much good steel as was needed.<ref name="King">P. W. King, 'The Cartel in Oregrounds Iron: trading in the raw material for steel during the eighteenth century' ''Journal of Industrial History'' 6(1) (2003), 25-49.</ref>  Brooke's [[Metallurgical furnace|furnace]]s were probably in his manor of [[Madeley, Shropshire|Madeley]] at [[Coalbrookdale]] (which certainly existed before the [[English Civil War]]) where two cementation furnaces have been excavated.<ref>P. Belford and R. A. Ross, 'English steelmaking in the seventeenth century: excavation of two cementation furnaces at Coalbrookdale' ''Historical Metallurgy'' 41(2) (2007), 105-123.</ref>  He probably used [[bar iron]] from the [[Forest of Dean]], where he was a partner in farming the King's ironworks in two periods.  

By 1631, it was recognised that Swedish iron was the best raw material and then or later particularly certain marks (brands) such as ''double bullet'' (so called from the mark OO) from [[Österbybruk|Österby]] and ''hoop L'' from Leufsta (now [[Lövstabruk|Lövsta]]), whose mark consisted of an L in a circle, both belonging to [[Louis De Geer (1587–1652)|Louis De Geer]] and his descendants.  These were among the first ironworks in [[Sweden]] to use the [[Walloon process]] of [[finery forge|fining]] iron, producing what was known in England as [[oregrounds iron]].  It was so called from the Swedish port of [[Öregrund]], north of Stockholm, in whose hinterland most of the ironworks lay.  The ore used came ultimately from the [[Dannemora, Sweden|Dannemora]] mine.<ref name="King"/><ref>{{cite book |last1=Barraclough |first1=K. C. |year=1990 |title=Swedish iron and Sheffield steel |series=[[History of Technology (book series)|History of Technology]] |volume=12 |pages=1–39 |isbn=0-7201-2075-6 |url=https://books.google.com/books?id=-jLSDAAAQBAJ&pg=PA1}}</ref>

==Process==
[[Image:Cementation_furnace,_Sheffield.jpg|thumb|right|The Doncaster Street cementation furnace in [[Sheffield]], [[England]]]]
The process begins with [[wrought iron]] and [[charcoal]].  It uses one or more long stone ''pots'' inside a furnace.  Typically, in [[Sheffield]], each pot was 14 feet by 4 feet and 3.5 feet deep.  Iron bars and charcoal are packed in alternating layers, with a top layer of charcoal and then refractory matter to make the pot or "coffin" airtight.  Some manufacturers used a mixture of powdered charcoal, [[soot]] and mineral [[salt (chemistry)|salt]]s, called ''cement powder''.  In larger works, up to 16 tons of iron were treated in each cycle, though it can be done on a small scale, such as in a small furnace or blacksmith's forge.

Depending on the thickness of the iron bars, the pots were then heated from below for a week or more.  Bars were regularly examined and when the correct condition was reached the heat was withdrawn and the pots were left until cool—usually around fourteen days.  The iron had gained a little over 1% in mass from the [[carbon]] in the charcoal, and had become heterogeneous bars of ''blister steel''.

The bars were then shortened, bound, heated and forge welded together to become ''shear steel''. It would be cut and re welded multiple times, with each new weld producing a more homogeneous, higher quality steel. This would be done at most 3-4 times, as more is unnecessary and could potentially cause carbon loss from the steel.   

Alternatively they could be broken up and melted in a crucible using a [[crucible steel|crucible furnace]] with a [[flux (metallurgy)|flux]] to become ''[[crucible steel]]'' (at the time also called ''cast steel''), a process devised by [[Benjamin Huntsman]] in Sheffield in the 1740s.

== Similar processes ==
===Brass production===
In the early modern period, [[brass]], an [[alloy]] of [[copper]] and [[zinc]], was usually produced by a cementation process in which metallic [[copper]] was heated with [[Calamine (mineral)|calamine]], a zinc ore, to make [[calamine brass]].

== Notes ==

{{refs}}

== References ==

{{refbegin}}
* K. C. Barraclough, ''Steel before Bessemer I: Blister Steel: The Birth of an Industry'' (1985).  
* K. C. Barraclough, "Swedish Iron and Sheffield Steel", ''History of Technology'' 12 (1990), 1–39.  
* Dorian Gerhold, "The steel industry in England, 1614-1740", in R.W. Hoyle (ed.), "Histories of people and landscape: essays on the Sheffield region in memory of David Hey" (2021), 65-86
* P. W. King, "The Cartel in Oregrounds Iron", ''Journal of Industrial History'' 6 (2003), 25–48.  
* R. J. MacKenzie and J. A Whiteman, "Why pay more? An archaeometallurgical examination of 19th century Swedish Wrought iron and Sheffield blister steel", ''Historical Metallurgy'' 40(2) (2006), 138–49.
{{refend}}

{{Iron and steel production}}

[[Category:Steelmaking]]
[[Category:Metallurgical processes]]
[[Category:Obsolete technologies]]