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== Ståltyper ==
[[File:Bethlehem Steel.jpg|thumb|[[Bethlehem Steel]] i [[Pennsylvania]] (USA) var en af verdens største stålfabrikanter inden værket blev lukket i 2003.]]
Legeringsgrundstofferne har stor indflydelse på stålets egenskaber; derfor opdeles stålene ofte løseligt i følgende grupper:
* Ulegeret stål: Stål med mindre end 1,5 % legeringsgrundstoffer
* Lavtlegerede stål: Stål med højst 5 % legeringsgrundstoffer
* Højtlegerede stål: Stål med mere end 5 % legeringsgrundstoffer
Der bliver bl.a. tilsat legeringsgrundstoffer for at få nye og bedre egenskaber for stålet, fx hårdheden, slidstyrken, hærdbarheden og mange andre.▼
===
Moderne stål fremstilles med forskellige kombinationer af legeringsmetaller til forskellige formål. [[Kulstofstål]], som ganske enkelt består af jern og kulstof, udgør 90% af al stålproduktion.<ref name=EM2/> Ofte [[galvanisering|galvaniseres]] kulstofstål med [[zink]], enten ved at dyppe det i smeltet zink eller ved [[elektrogalvanisering|elektrolytisk metalbelægning]].<ref>{{cite|title=Galvanic protection|encyclopedia=Encyclopædia Britannica|year=2007}}</ref>
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=== Lavtlegerede ståltyper ===
[[Low alloy steel]] is alloyed with other elements, usually [[molybdenum]], manganese, chromium, or nickel, in amounts of up to 10% by weight to improve the hardenability of thick sections.<ref name=EM2/> [[HSLA steel|High strength low alloy steel]] has small additions (usually < 2% by weight) of other elements, typically 1.5% manganese, to provide additional strength for a modest price increase.<ref>{{cite web|url=http://resources.schoolscience.co.uk/Corus/16plus/steelch3pg1.html|title=High strength low alloy steels|publisher=Schoolscience.co.uk|accessdate=2007-08-14}}</ref>
Recent [[Corporate Average Fuel Economy]] (CAFE) regulations have given rise to a new variety of steel known as Advanced High Strength Steel (AHSS). This material is both strong and ductile so that vehicle structures can maintain their current safety levels while using less material. There are several commercially available grades of AHSS, such as [[dual-phase steel]], which is heat treated to contain both a ferritic and martensitic microstructure to produce a formable, high strength steel.<ref>{{cite web|title=Dual-phase steel|publisher=Intota Expert Knowledge Services|url=http://www.intota.com/experts.asp?strSearchType=all&strQuery=dual%2Dphase+steel|accessdate=2007-03-01}}</ref> Transformation Induced Plasticity (TRIP) steel involves special alloying and heat treatments to stabilize amounts of [[austenite]] at room temperature in normally austenite-free low-alloy ferritic steels. By applying strain, the [[austenite]] undergoes a [[phase transition]] to martensite without the addition of heat.<ref>{{cite web|last=Werner |first=Ewald |title=Transformation Induced Plasticity in low alloyed TRIP-steels and microstructure response to a complex stress history |url=http://www.wkm.mw.tum.de/Forschung/projekte_html/transtrip.html |accessdate=2007-03-01 |deadurl=yes |archiveurl=https://web.archive.org/web/20071223184922/http://www.wkm.mw.tum.de/Forschung/projekte_html/transtrip.html |archivedate=December 23, 2007 }}</ref> Twinning Induced Plasticity (TWIP) steel uses a specific type of strain to increase the effectiveness of work hardening on the alloy.<ref>{{cite web|last=Mirko|first=Centi|author2=Saliceti Stefano |title=Transformation Induced Plasticity (TRIP), Twinning Induced Plasticity (TWIP) and Dual-Phase (DP) Steels|publisher=Tampere University of Technology |url=http://www.dimet.unige.it/resta/studenti/2002/27839/26/TWIP,TRIPandDualphase%20mirko.doc |archiveurl=//web.archive.org/web/20080307200557/http://www.dimet.unige.it/resta/studenti/2002/27839/26/TWIP,TRIPandDualphase+mirko.doc |archivedate=2008-03-07|accessdate=2007-03-01}}</ref>-->
=== Legerede ståltyper ===
▲Der bliver bl.a. tilsat legeringsgrundstoffer for at få nye og bedre egenskaber for stålet, fx hårdheden, slidstyrken, hærdbarheden og mange andre.
* [[Rustfrit stål]]
* [[Værktøjsstål]]
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<!--Stainless steels contain a minimum of 11% chromium, often combined with nickel, to resist [[corrosion]]. Some stainless steels, such as the [[Ferrite (iron)|ferritic]] stainless steels are [[magnetic]], while others, such as the [[austenite|austenitic]], are nonmagnetic.<ref>{{cite web|url=http://steel.org |title=Steel Glossary |publisher= [[American Iron and Steel Institute]] (AISI)|accessdate=2006-07-30}}</ref> Corrosion-resistant steels are abbreviated as CRES.
Some more modern steels include [[tool steel]]s, which are alloyed with large amounts of tungsten and [[cobalt]] or other elements to maximize [[solution hardening]]. This also allows the use of [[precipitation hardening]] and improves the alloy's temperature resistance.<ref name=EM2/> Tool steel is generally used in axes, drills, and other devices that need a sharp, long-lasting cutting edge. Other special-purpose alloys include [[weathering steel]]s such as Cor-ten, which weather by acquiring a stable, rusted surface, and so can be used un-painted.<ref>{{cite web|url=http://aisc.org/MSCTemplate.cfm?Section=Steel_Interchange2&Template=/CustomSource/Faq/SteelInterchange.cfm&FaqID=2311|archiveurl=//web.archive.org/web/20071222180444/http://aisc.org/MSCTemplate.cfm?Section=Steel_Interchange2&Template=/CustomSource/Faq/SteelInterchange.cfm&FaqID=2311|archivedate=2007-12-22|title=Steel Interchange|publisher= American Institute of Steel Construction Inc. (AISC)|accessdate=2007-02-28}}</ref> [[Maraging steel]] is alloyed with nickel and other elements, but unlike most steel contains little carbon (0.01%). This creates a very strong but still [[malleability|malleable]] steel.<ref>{{cite web|title = Properties of Maraging Steels|url = http://steel.keytometals.com/default.aspx?ID=CheckArticle&NM=103|accessdate=2009-07-19}}</ref>
[[Eglin steel]] uses a combination of over a dozen different elements in varying amounts to create a relatively low-cost steel for use in [[bunker buster]] weapons. Hadfield steel (after Sir [[Robert Hadfield]]) or manganese steel contains 12–14% manganese which when abraded strain-hardens to form an incredibly hard skin which resists wearing. Examples include [[Continuous track|tank tracks]], [[bulldozer#Blade|bulldozer blade]] edges and cutting blades on the [[jaws of life]].<ref>[http://answers.com/topic/hadfield-manganese-steel Hadfield manganese steel]. Answers.com. McGraw-Hill Dictionary of Scientific and Technical Terms, McGraw-Hill Companies, Inc., 2003. Retrieved on 2007-02-28.</ref>
In 2016 a breakthrough in creating a strong light aluminium steel alloy which might be suitable in applications such as aircraft was announced by researchers at [[Pohang University of Science and Technology]]. Adding small amounts of nickel was found to result in precipitation as nano particles of brittle B2 [[intermetallic]] compounds which had previously resulted in weakness. The result was a cheap strong light steel alloy—nearly as strong as [[titanium]] at ten percent the cost<ref name=pm20150204>
{{cite news |last1=Herkewitz|first1=William |title=Scientists Invent a New Steel as Strong as Titanium ; South Korean researchers have solved a longstanding problem that stopped them from creating ultra-strong, lightweight aluminum-steel alloys |url=http://www.popularmechanics.com/technology/news/a13919/new-steel-alloy-titanium/?1443670416676=1 |work=Popular Mechanics |date=2015-02-04 }}</ref>—which is slated for trial production{{when|date=October 2015}} at industrial scale by [[POSCO]], a Korean steelmaker.<ref>{{cite news|title=Wings of steel: An alloy of iron and aluminium is as good as titanium, at a tenth of the cost|url=http://www.economist.com/news/science-and-technology/21642107-alloy-iron-and-aluminium-good-titanium-tenth|accessdate=February 5, 2015|work=The Economist|date=February 7, 2015|quote=E02715}}</ref><ref name=Nature02515>{{cite journal|author1=Sang-Heon Kim, Hansoo Kim & Nack J. Kim|title=Brittle intermetallic compound makes ultrastrong low-density steel with large ductility|journal=Nature|date=February 5, 2015|volume=518|issue=7537|pages=77–79|doi=10.1038/nature14144|pmid=25652998|url=http://www.nature.com/nature/journal/v518/n7537/full/nature14144.html|accessdate=February 5, 2015|publisher=Nature Publishing Group|quote=we show that an FeAl-type brittle but hard intermetallic compound (B2) can be effectively used as a strengthening second phase in high-aluminium low-density steel, while alleviating its harmful effect on ductility by controlling its morphology and dispersion.}}</ref>
=== Standards ===
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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