Stål: Forskelle mellem versioner
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Most of the more commonly used steel alloys are categorized into various grades by standards organizations. For example, the [[Society of Automotive Engineers]] has a series of [[SAE steel grades|grades]] defining many types of steel.<ref name=bringas>{{Cite book|last=Bringas|first=John E.|title=Handbook of Comparative World Steel Standards: Third Edition|publisher=ASTM International|page =14|year=2004|edition=3rd.|url=http://astm.org/BOOKSTORE/PUBS/DS67B_SampleChapter.pdf|archiveurl=//web.archive.org/web/20070127135646/http://www.astm.org/BOOKSTORE/PUBS/DS67B_SampleChapter.pdf|archivedate=2007-01-27|format=PDF|isbn=0-8031-3362-6}}</ref> The [[ASTM International|American Society for Testing and Materials]] has a separate set of standards, which define alloys such as [[A36 steel]], the most commonly used structural steel in the United States.<ref>Steel Construction Manual, 8th Edition, second revised edition, American Institute of Steel Construction, 1986, ch. 1 page 1-5</ref> The [[JIS | Japanese Industrial Standards]] also defines series of steel grades that are being used extensively in Japan as well in third world countries.-->
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=== Ældre tid ===
I ældre tid brugtes, især til våben, ''[[damascere]]t'' stål (efter byen [[Damaskus]]). Det var en teknik, hvor rent jern opkulledes ved opvarmning i en lukket [[ovn]] sammen med kulstof. Dette kunne give helt op til 1,8% kulindhold. Ved at smede det sammen med rent jern kombinerede man de to materialers egenskaber til et materiale, der var hårdt og fleksibelt på samme tid, faktisk ligesom vores [[tand|tænder]]; en hård [[tandemalje|emalje]] udenpå og blødt [[ben (materiale)|ben]] indeni.▼
▲I ældre tid brugtes, især til våben, ''[[
=== Nyere tid ===
[[File:Bessemer Converter Sheffield.jpg|thumb|right|upright|En bessemer-converter i [[Sheffield]] (England).]]
Siden det [[17. århundrede]] har det første trin i europæisk stålproduktion været udsmeltning af råjern fra jernmalm i en [[højovn]]. Oprindelig bruges trækul, men moderne metoder bruger [[koks]], som er mere rentabelt. Før man kunne lave stål, måtte råjernet omdannes til [[smedejern]].<ref name="tyle">Tylecote, R. F. ''A history of metallurgy'' 2. udg., Institute of Materials, London 1992, 95–105.</ref>
<!--The modern era in [[steelmaking]] began with the introduction of [[Henry Bessemer]]'s [[Bessemer process]] in 1855, the raw material for which was pig iron.<ref>{{cite book|title=History of the Manufacture of Iron in All Ages|author= Swank, James Moore |isbn=0-8337-3463-6| year=1892}}</ref> His method let him produce steel in large quantities cheaply, thus [[mild steel]] came to be used for most purposes for which wrought iron was formerly used.<ref>{{cite book|title=Bessemer process|volume=2|page=168|publisher=Encyclopædia Britannica|year=2005}}</ref> The Gilchrist-Thomas process (or ''basic Bessemer process'') was an improvement to the Bessemer process, made by lining the converter with a [[basic (chemistry)|basic]] material to remove phosphorus.
Another 19th-century steelmaking process was the [[Siemens-Martin process]], which complemented the Bessemer process.<ref name="britannicaironandsteel"/> It consisted of co-melting bar iron (or steel scrap) with pig iron.
These methods of steel production were rendered obsolete by the Linz-Donawitz process of [[basic oxygen steelmaking]] (BOS), developed in the 1950s, and other oxygen steel making methods. Basic oxygen steelmaking is superior to previous steelmaking methods because the oxygen pumped into the furnace limited impurities, primarily nitrogen, that previously had entered from the air used.<ref>{{cite book|title = Basic oxygen process|publisher = Encyclopædia Britannica|year = 2007}}</ref> Today, [[electric arc furnace]]s (EAF) are a common method of reprocessing [[scrap|scrap metal]] to create new steel. They can also be used for converting pig iron to steel, but they use a lot of electrical energy (about 440 kWh per metric ton), and are thus generally only economical when there is a plentiful supply of cheap electricity.<ref>Jones, J.A.T. ; Bowman, B. and Lefrank, P.A. ''Electric Furnace Steelmaking'', in ''The Making, Shaping and Treating of Steel'', pp. 525–660. R.J. Fruehan, Editor. 1998, The AISE Steel Foundation: Pittsburgh.</ref>-->
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