Editing Steel

{{Short description|Alloy of iron and carbon}}
{{Other uses}}
{{Redirect|Steel worker}}
{{Good article}}
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{{Use dmy dates|cs1-dates=l|date=April 2024}}
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{{Steels}}
'''Steel''' is an [[alloy]] of [[iron]] and [[carbon]] that demonstrates improved [[mechanical properties]] compared to the pure form of iron. Due to steel's high [[Young's modulus|elastic modulus]], [[Yield (engineering)|yield strength]], [[Fracture|fracture strength]] and low raw material cost, steel is one of the most commonly manufactured materials in the world. Steel is used in structures (as concrete [[Rebar|reinforcing rods)]], in [[Bridge|bridges]], [[infrastructure]], [[Tool|tools]], [[Ship|ships]], [[Train|trains]], [[Car|cars]], [[Bicycle|bicycles]], [[Machine|machines]], [[Home appliance|electrical appliances]], [[furniture]], and [[Weapon|weapons]].

Iron is always the main element in steel, but other elements are used to produce various grades of steel demonstrating altered material, mechanical, and microstructural properties. [[Stainless steel]]s, for example, typically contain 18% [[chromium]] and exhibit improved [[corrosion]] and [[Redox|oxidation]] resistance versus its carbon steel counterpart. Under atmospheric pressures, steels generally take on two crystalline forms: [[Cubic crystal system|body-centered cubic and face-centered cubic]], however depending on the thermal history and alloying, the microstructure may contain the distorted [[martensite]] phase or the carbon-rich [[cementite]] phase, which are [[Tetragonal crystal system|tetragonal]] and [[Orthorhombic crystal system|orthorhombic]], respectively. In the case of alloyed iron, the strengthening is primarily due to the introduction of carbon in the primarily-iron lattice inhibiting deformation under [[Stress (mechanics)|mechanical stress]]. Alloying may also induce additional phases that affect the mechanical properties. In most cases, the engineered mechanical properties are at the expense of the [[ductility]] and [[Elongation (materials science)|elongation]] of the pure iron state, which decrease upon the addition of carbon.

Steel was produced in [[bloomery]] furnaces for thousands of years, but its large-scale, industrial use began only after more efficient production methods were devised in the 17th century, with the introduction of the [[blast furnace]] and production of [[crucible steel]]. This was followed by the  [[Bessemer process]]  in [[England]] in the mid-19th century, and then by the [[open-hearth furnace]]. With the invention of the Bessemer process, a new era of [[Mass production|mass-produced]] steel began. [[Mild steel]] replaced [[wrought iron]]. [[German Empire|The German states]] were the major steel producers in Europe in the 19th century.<ref>{{cite journal |first1=Robert C. |last1=Allen |title=International Competition in Iron and Steel, 1850–1913 |journal=The Journal of Economic History |volume=39 |issue=4 |date=December 1979 |pages=911–937 |publisher=[[Cambridge University Press]] |doi=10.1017/S0022050700098673 |jstor=2120336}}</ref> American steel production was centred in [[Pittsburgh]]; [[Bethlehem, Pennsylvania]]; and [[Cleveland]] until the late 20th century. Currently, [[List of countries by steel production|world steel production]] is centered in China, which produced 54% of the world's steel in 2023.

Further refinements in the process, such as [[basic oxygen steelmaking]] (BOS), largely replaced earlier methods by further lowering the cost of production and increasing the quality of the final product. Today more than 1.6 billion&nbsp;tons of steel is produced annually. Modern steel is generally identified by various grades defined by assorted [[standards organization]]s. The modern steel industry is one of the largest manufacturing industries in the world, but also one of the most energy and [[Greenhouse gas emissions|greenhouse gas emission]] intense industries, contributing 8% of global emissions.<ref>{{Cite web |title=Decarbonization in steel {{!}} McKinsey |url= https://www.mckinsey.com/industries/metals-and-mining/our-insights/decarbonization-challenge-for-steel |access-date=20 May 2022 |website=McKinsey.com}}</ref> However, steel is also very reusable: it is one of the world's most-recycled materials, with a [[Ferrous metal recycling|recycling rate of over 60% globally]].<ref name="encarta-recycling" />

==Definitions and related materials==
{{See also|Steel grades}}
[[File:Steel wire rope.JPG|thumb|upright|[[Steel cable]] of a [[coal mining|colliery]] [[headframe]]]]
The noun ''steel'' originates from the [[Proto-Germanic language|Proto-Germanic]] adjective {{lang|gem-x-proto|stahliją}} or {{lang|gem-x-proto|stakhlijan}} 'made of steel', which is related to {{lang|gem-x-proto|stahlaz}} or {{lang|gem-x-proto|stahliją}} 'standing firm'.<ref>{{OEtymD|steel}}</ref>

The carbon content of steel is between 0.02% and 2.14% by weight for plain carbon steel ([[iron]]-[[carbon]] [[alloy]]s). [[Alloy steel]] is steel to which other alloying elements have been intentionally added to modify the characteristics of steel. Common alloying elements include: [[manganese]], [[nickel]], [[chromium]], [[molybdenum]], [[boron]], [[titanium]], [[vanadium]], [[tungsten]], [[cobalt]], and [[niobium]].<ref name="EM2">{{cite book |author1=Ashby, Michael F. |author2=Jones, David R.H. |name-list-style=amp |title=Engineering Materials 2 |orig-date=1986 |edition=with corrections |date=1992 |publisher=Pergamon Press |location=Oxford |isbn=0-08-032532-7}}</ref> Additional elements, most frequently considered undesirable, are also important in steel: [[phosphorus]], [[sulphur]], [[silicon]], and traces of [[oxygen]], [[nitrogen]], and [[copper]].

Plain iron-carbon alloys with a higher than 2.1% carbon content are known as [[cast iron]]. With modern [[steelmaking]] techniques such as powder metal forming, it is possible to make very high-carbon (and other alloy material) steels, but such are not common. Cast iron is not malleable even when hot, but it can be formed by [[casting]] as it has a lower [[melting point]] than steel and good [[castability]] properties.<ref name="EM2" /> Certain compositions of cast iron, while retaining the economies of melting and casting, can be heat treated after casting to make [[malleable iron]] or [[ductile iron]] objects. Steel is distinguishable from [[wrought iron]] (now largely obsolete), which may contain a small amount of carbon but large amounts of [[slag]].

==Material properties==
===Origins and production===
[[File:FeC-phase-diagram--multilingual.svg|thumb|upright=1.75|An iron-carbon [[phase diagram]] showing the conditions necessary to form different phases]]
[[File:Blacksmithing at the 2015 Fort Ross Festival - Fort Ross State Historic Park - Jenner, California - Sarah Stierch.jpg|thumb|An [[Incandescence|incandescent]] steel workpiece in a [[blacksmith]]'s art]]
Iron is commonly found in the Earth's [[crust (geology)|crust]] in the form of an [[ore]], usually an iron oxide, such as [[magnetite]] or [[hematite]]. Iron is extracted from [[iron ore]] by removing the oxygen through its combination with a preferred chemical partner such as carbon which is then lost to the atmosphere as carbon dioxide. This process, known as [[smelting]], was first applied to metals with lower [[melting]] points, such as [[tin]], which melts at about {{convert|250|C|F|abbr=on}}, and [[copper]], which melts at about {{convert|1100|C|F|abbr=on}}, and the combination, bronze, which has a melting point lower than {{convert|1083|C|F|abbr=on}}. In comparison, cast iron melts at about {{convert|1375|C|F|abbr=on}}.<ref name="Smelting">{{cite book |chapter=Smelting |title=[[Encyclopædia Britannica]] |edition=online |date=2007 |chapter-url= https://www.britannica.com/technology/smelting}}</ref> Small quantities of iron were smelted in ancient times, in the solid-state, by heating the ore in a [[charcoal]] fire and then [[welding]] the clumps together with a hammer and in the process squeezing out the impurities. With care, the carbon content could be controlled by moving it around in the fire. Unlike copper and tin, liquid or solid iron dissolves carbon quite readily.{{Cn|date=January 2024}}

All of these temperatures could be reached with ancient methods used since the [[Bronze Age]]. Since the oxidation rate of iron increases rapidly beyond {{convert|800|C|F}}, it is important that smelting take place in a low-oxygen environment. Smelting, using carbon to reduce iron oxides, results in an alloy ([[pig iron]]) that retains too much carbon to be called steel.<ref name="Smelting" /> The excess carbon and other impurities are removed in a subsequent step.{{Cn|date=January 2024}}

Other materials are often added to the iron/carbon mixture to produce steel with the desired properties. [[Nickel]] and [[manganese]] in steel add to its tensile strength and make the [[austenite]] form of the iron-carbon solution more stable, [[chromium]] increases hardness and melting temperature, and [[vanadium]] also increases hardness while making it less prone to [[metal fatigue]].<ref name="materialsengineer">{{cite web |title=Alloying of Steels |publisher=Metallurgical Consultants |date=28 June 2006 |url= http://materialsengineer.com/E-Alloying-Steels.htm |access-date=28 February 2007 |url-status=dead |archive-url= https://web.archive.org/web/20070221070822/http://www.materialsengineer.com/E-Alloying-Steels.htm |archive-date=21 February 2007}}</ref>

To inhibit corrosion, at least 11% chromium can be added to steel so that a hard [[Passivation (chemistry)|oxide]] forms on the metal surface; this is known as [[stainless steel]]. Tungsten slows the formation of [[cementite]], keeping carbon in the iron matrix and allowing [[martensite]] to preferentially form at slower quench rates, resulting in [[high-speed steel]]. The addition of [[lead]] and [[sulphur]] decrease grain size, thereby making the steel easier to [[lathe|turn]], but also more brittle and prone to corrosion. Such alloys are nevertheless frequently used for components such as nuts, bolts, and washers in applications where toughness and corrosion resistance are not paramount. For the most part, however, [[Block (periodic table)|p-block]] elements such as sulphur, [[nitrogen]], [[phosphorus]], and lead are considered contaminants that make steel more brittle and are therefore removed from steel during the melting processing.<ref name="materialsengineer" />

===Properties===
[[File:Steel_Fe-C_phase_diagram-en.png|thumb|upright=1.5|Fe-C phase diagram for carbon steels, showing the A<sub>0</sub>, A<sub>1</sub>, A<sub>2</sub> and A<sub>3</sub> critical temperatures for heat treatments]]
The [[density]] of steel varies based on the alloying constituents but usually ranges between {{convert|7750|and|8050|kg/m3|lb/ft3|abbr=on}}, or {{convert|7.75|and|8.05|g/cm3|oz/cuin|abbr=on}}.<ref>{{cite web |last=Elert |first=Glenn |title=Density of Steel |url= http://hypertextbook.com/facts/2004/KarenSutherland.shtml |access-date=23 April 2009}}</ref>

Even in a narrow range of concentrations of mixtures of carbon and iron that make steel, several different metallurgical structures, with very different properties can form. Understanding such properties is essential to making quality steel. At [[room temperature]], the most stable form of pure iron is the [[body-centred cubic]] (BCC) structure called alpha iron or α-iron. It is a fairly soft metal that can dissolve only a small concentration of carbon, no more than 0.005% at {{Convert|0|C|F|abbr=on}} and 0.021 wt% at {{convert|723|C|F|abbr=on}}. The inclusion of carbon in alpha iron is called [[Allotropes of iron|ferrite]]. At 910&nbsp;°C, pure iron transforms into a [[face-centred cubic]] (FCC) structure, called gamma iron or γ-iron. The inclusion of carbon in gamma iron is called austenite. The more open FCC structure of austenite can dissolve considerably more carbon, as much as 2.1%,<ref>Sources differ on this value so it has been rounded to 2.1%, however the exact value is rather academic because plain-carbon steel is very rarely made with this level of carbon. See:
* {{harvnb|Smith|Hashemi|2006|p=363}}—2.08%.
* {{harvnb|Degarmo|Black|Kohser|2003|p=75}}—2.11%.
* {{harvnb|Ashby|Jones|1992}}—2.14%.</ref> (38 times that of ferrite) carbon at {{convert|1148|C|F|abbr=on}}, which reflects the upper carbon content of steel, beyond which is cast iron.<ref>{{harvnb|Smith|Hashemi|2006|p=363}}.</ref> When carbon moves out of solution with iron, it forms a very hard, but brittle material called cementite (Fe<sub>3</sub>C).{{Cn|date=January 2024}}

When steels with exactly 0.8% carbon (known as a eutectoid steel), are cooled, the [[austenitic]] phase (FCC) of the mixture attempts to revert to the ferrite phase (BCC). The carbon no longer fits within the FCC austenite structure, resulting in an excess of carbon. One way for carbon to leave the austenite is for it to [[precipitate]] out of solution as [[cementite]], leaving behind a surrounding phase of BCC iron called ferrite with a small percentage of carbon in solution. The two, cementite and ferrite, precipitate simultaneously producing a layered structure called [[pearlite]], named for its resemblance to [[mother of pearl]]. In a hypereutectoid composition (greater than 0.8% carbon), the carbon will first precipitate out as large inclusions of cementite at the austenite [[grain boundaries]] until the percentage of carbon in the [[Grain (metal)|grains]] has decreased to the eutectoid composition (0.8% carbon), at which point the pearlite structure forms. For steels that have less than 0.8% carbon (hypoeutectoid), ferrite will first form within the grains until the remaining composition rises to 0.8% of carbon, at which point the pearlite structure will form. No large inclusions of cementite will form at the boundaries in hypoeutectoid steel.<ref>{{harvnb|Smith|Hashemi|2006|pp=365–372}}.</ref> The above assumes that the cooling process is very slow, allowing enough time for the carbon to migrate.{{Cn|date=January 2024}}

As the rate of cooling is increased the carbon will have less time to migrate to form carbide at the grain boundaries but will have increasingly large amounts of pearlite of a finer and finer structure within the grains; hence the carbide is more widely dispersed and acts to prevent slip of defects within those grains, resulting in hardening of the steel. At the very high cooling rates produced by quenching, the carbon has no time to migrate but is locked within the face-centred austenite and forms [[martensite]]. Martensite is a highly strained and stressed, supersaturated form of carbon and iron and is exceedingly hard but brittle. Depending on the carbon content, the martensitic phase takes different forms. Below 0.2% carbon, it takes on a ferrite BCC crystal form, but at higher carbon content it takes a [[body-centred tetragonal]] (BCT) structure. There is no thermal [[activation energy]] for the transformation from austenite to martensite.{{clarify|date=April 2016}} There is no compositional change, so the atoms generally retain their same neighbours.<ref name="smith&hashemi">{{Harvnb|Smith|Hashemi|2006|pp=373–378}}.</ref>

Martensite has a lower density (it expands during the cooling) than does austenite, so that the transformation between them results in a change of volume. In this case, expansion occurs. Internal stresses from this expansion generally take the form of [[physical compression|compression]] on the crystals of martensite and [[tension (mechanics)|tension]] on the remaining ferrite, with a fair amount of [[shear stress|shear]] on both constituents. If quenching is done improperly, the internal stresses can cause a part to shatter as it cools. At the very least, they cause internal [[work hardening]] and other microscopic imperfections. It is common for quench cracks to form when steel is water quenched, although they may not always be visible.<ref>{{cite web |title=Quench hardening of steel |url= http://steel.keytometals.com/default.aspx?ID=CheckArticle&NM=12 |access-date=19 July 2009 |work=keytometals.com |url-status=dead |archive-url= https://web.archive.org/web/20090217103241/http://steel.keytometals.com/default.aspx?ID=CheckArticle&NM=12 |archive-date=17 February 2009}}</ref>

===Heat treatment===
{{Main|Heat treating}}
There are many types of [[heat treatment|heat treating]] processes available to steel. The most common are [[annealing (metallurgy)|annealing]], [[quenching]], and [[tempering (metallurgy)|tempering]].

Annealing is the process of heating the steel to a sufficiently high temperature to relieve local internal stresses. It does not create a general softening of the product but only locally relieves strains and stresses locked up within the material. Annealing goes through three phases: [[recovery (metallurgy)|recovery]], [[recrystallization (metallurgy)|recrystallization]], and [[grain growth]]. The temperature required to anneal a particular steel depends on the type of annealing to be achieved and the alloying constituents.<ref>{{harvnb|Smith|Hashemi|2006|p=249}}.</ref>

Quenching involves heating the steel to create the austenite phase then quenching it in water or [[oil]]. This rapid cooling results in a hard but brittle martensitic structure.<ref name="smith&hashemi" /> The steel is then tempered, which is just a specialized type of annealing, to reduce brittleness. In this application the annealing (tempering) process transforms some of the martensite into cementite, or [[spheroidite]] and hence it reduces the internal stresses and defects. The result is a more ductile and fracture-resistant steel.<ref>{{harvnb|Smith|Hashemi|2006|p=388}}.</ref>

==Production==
{{Main|Steelmaking}}
{{See also|List of countries by steel production}}
[[File:LightningVolt Iron Ore Pellets.jpg|thumb|[[Iron ore]] pellets used in the production of steel]]
When iron is [[smelting|smelted]] from its ore, it contains more carbon than is desirable. To become steel, it must be reprocessed to reduce the carbon to the correct amount, at which point other elements can be added. In the past, steel facilities would [[casting (metalworking)|cast]] the raw steel product into [[ingot]]s which would be stored until use in further refinement processes that resulted in the finished product. In modern facilities, the initial product is close to the final composition and is [[continuous casting|continuously cast]] into long slabs, cut and shaped into bars and extrusions and heat treated to produce a final product. Today, approximately 96% of steel is continuously cast, while only 4% is produced as ingots.<ref>{{harvnb|Smith|Hashemi|2006|p=361}}</ref>

The ingots are then heated in a soaking pit and [[hot rolling|hot rolled]] into slabs, [[Billet (semi-finished product)#Billet|billets]], or [[Billet (semi-finished product)#Bloom|blooms]]. Slabs are hot or [[cold rolling|cold rolled]] into [[sheet metal]] or plates. Billets are hot or cold rolled into bars, rods, and wire. Blooms are hot or cold rolled into [[structural steel]], such as [[I-beam]]s and [[rail tracks|rails]]. In modern steel mills these processes often occur in one [[assembly line]], with ore coming in and finished steel products coming out.<ref>{{harvnb|Smith|Hashemi|2006|pp=361–362}}.</ref> Sometimes after a steel's final rolling, it is heat treated for strength; however, this is relatively rare.<ref>{{harvnb|Bugayev|Konovalov|Bychkov|Tretyakov|Savin|2001|p=225}}</ref>

==History==
{{Main|History of ferrous metallurgy|History of the steel industry (1850–1970)}}
===Ancient===
[[File:Bas fourneau.png|thumb|upright|[[Bloomery]] smelting during the [[Middle Ages]] in the 5th to 15th centuries]]
Steel was known in antiquity and was produced in [[Bloomery|bloomeries]] and [[crucible]]s.{{sfnp|Davidson|1994|p=20}}<ref name="materials.iisc.ernet.in">{{Cite news |author1=Srinivasan, S. |author2=Ranganathan, S. |url= https://materials.iisc.ernet.in/~wootz/heritage/WOOTZ.htm |title=The Sword in Anglo-Saxon England: Its Archaeology and Literature |date=1994 |publisher=Department of Metallurgy, Indian Institute of Science |location=Bangalore |isbn=0-85115-355-0 |archive-url= https://web.archive.org/web/20181119033451/http://materials.iisc.ernet.in/~wootz/heritage/WOOTZ.htm |archive-date=19 November 2018}}</ref>

The earliest known production of steel is seen in pieces of [[Iron ware|ironware]] excavated from an [[archaeological site]] in [[Anatolia]] ([[Kaman-Kalehöyük]]) which are nearly 4,000 years old, dating from 1800&nbsp;BC.<ref>{{cite journal |last=Akanuma |first=H. |title=The significance of the composition of excavated iron fragments taken from Stratum III at the site of Kaman-Kalehöyük, Turkey |journal=Anatolian Archaeological Studies |volume=14 |pages=147–158 |date=2005 |publisher=Japanese Institute of Anatolian Archaeology |place=Tokyo}}</ref><ref>{{cite news |title=Ironware piece unearthed from Turkey found to be oldest steel |url= http://www.hindu.com/thehindu/holnus/001200903261611.htm |access-date=13 August 2022 |location=Chennai |work=[[The Hindu]] |date=26 March 2009 |url-status=dead |archive-url= https://web.archive.org/web/20090329111924/http://www.hindu.com/thehindu/holnus/001200903261611.htm |archive-date=29 March 2009}}</ref> 

[[Wootz steel]] was developed in [[Southern India]] and [[Sri Lanka]] in the 1st millennium BCE.<ref name="materials.iisc.ernet.in" /> Metal production sites in [[Sri Lanka]] employed wind furnaces driven by the monsoon winds, capable of producing high-carbon steel. Large-scale wootz steel production in [[Ancient India|India]] using crucibles occurred by the sixth century&nbsp;BC, the pioneering precursor to modern steel production and metallurgy.{{sfnp|Davidson|1994|p=20}}<ref name="materials.iisc.ernet.in" />

High-carbon steel was produced in [[British Iron Age|Britain]] at [[Broxmouth|Broxmouth Hillfort]] from 490–375 BC,<ref>{{Cite news |title=East Lothian's Broxmouth fort reveals edge of steel |url= https://www.bbc.co.uk/news/uk-scotland-edinburgh-east-fife-25734877 |work=[[BBC News]] |date=15 January 2014}}</ref><ref>{{cite book |url= https://www.socantscot.org/product/an-inherited-place/ |title=An Inherited Place: Broxmouth Hillfort and the South-East Scottish Iron Age |date=2013 |publisher=Society of Antiquaries of Scotland |isbn=978-1-908332-05-9}}</ref> and ultrahigh-carbon steel was produced in the [[Netherlands]] from the 2nd-4th centuries AD.<ref>{{cite journal |url= https://www.sciencedirect.com/science/article/abs/pii/S0305440304000202 |journal=Journal of Archaeological Science |volume=31 |issue=8 |date=2004 |title=A Germanic ultrahigh carbon steel punch of the Late Roman-Iron Age |last1=Godfrey |first1=Evelyne |display-authors=etal |doi=10.1016/j.jas.2004.02.002 |pages=1117–1125 |bibcode=2004JArSc..31.1117G}}</ref> The Roman author [[Horace]] identifies steel weapons such as the ''[[falcata]]'' in the [[Iberian Peninsula]], while [[Noric steel]] was used by the [[Military of ancient Rome|Roman military]].<ref>"Noricus ensis", [[Horace]], Odes, i. 16.9</ref>

The [[History of China#Ancient China|Chinese]] of the [[Warring States period]] (403&ndash;221&nbsp;BC) had [[quench|quench-hardened]] steel,<ref>{{cite book |last=Wagner |first=Donald B. |date=1993 |title=Iron and Steel in Ancient China |edition=2nd |location=Leiden |publisher=E. J. Brill |isbn=90-04-09632-9 |page=243}}</ref> while Chinese of the [[Han dynasty]] (202&nbsp;BC&mdash;AD&nbsp;220) created steel by melting together wrought iron with cast iron, thus producing a carbon-intermediate steel by the 1st century&nbsp;AD.<ref name="needham volume 4 part 3 563g">{{cite book |last=Needham |first=Joseph |date=1986 |title=Science and Civilization in China: Volume 4, Part 3, Civil Engineering and Nautics |location=Taipei |publisher=Caves Books |page=563}}</ref><ref name="gernet 69">Gernet, Jacques (1982). ''A History of Chinese Civilization''. Cambridge: Cambridge University Press. p. 69. {{ISBN|0-521-49781-7}}.</ref>

There is evidence that [[carbon steel]] was made in Western [[Tanzania]] by the ancestors of the [[Haya people]] as early as 2,000 years ago by a complex process of "pre-heating" allowing temperatures inside a furnace to reach 1300 to 1400&nbsp;°C.<ref name="SchmidtCS">{{Cite journal |last1=Schmidt |first1=Peter |last2=Avery |first2=Donald |date=1978 |title=Complex Iron Smelting and Prehistoric Culture in Tanzania |journal=Science |volume=201 |issue=4361 |pages=1085–1089 |jstor=1746308 |doi=10.1126/science.201.4361.1085 |pmid=17830304 |bibcode=1978Sci...201.1085S |s2cid=37926350}}</ref><ref name=":3">{{Cite journal |last1=Schmidt |first1=Peter |last2=Avery |first2=Donald |date=1983 |title=More Evidence for an Advanced Prehistoric Iron Technology in Africa |journal=Journal of Field Archaeology |volume=10 |issue=4 |pages=421–434 |doi=10.1179/009346983791504228}}</ref><ref name=":0">{{Cite book |title=Historical Archaeology: A Structural Approach in an African Culture |last=Schmidt |first=Peter |publisher=Greenwood Press |date=1978 |location=Westport, Connecticut}}</ref><ref>{{Cite book |title=The Culture and Technology of African Iron Production |last1=Avery |first1=Donald |last2=Schmidt |first2=Peter |publisher=University of Florida Press |date=1996 |location=Gainesville, Florida |pages=267–276 |chapter=Preheating: Practice or illusion}}</ref><ref>{{Cite book |title=A Companion to African History |last=Schmidt |first=Peter |publisher=Wiley Blackwell |date=2019 |editor-last=Worger |editor-first=W. |location=Hoboken, New Jersey |pages=267–288 |chapter=Science in Africa: A history of ingenuity and invention in African iron technology |editor-last2=Ambler |editor-first2=C. |editor-last3=Achebe |editor-first3=N.}}</ref><ref>{{Cite book |last=Childs |first=S. Terry |chapter=Technological history and culture in western Tanzania |title=The Culture and Technology of African Iron Production |publisher=University of Florida Press |date=1996 |editor-last=Schmidt |editor-first=P. |location=Gainesville, Florida}}</ref>

===Wootz and Damascus===
{{Main|Wootz steel|Damascus steel}}

Evidence of the earliest production of high carbon steel in [[South Asia]] is found in [[Kodumanal]] in [[Tamil Nadu]], the [[Golconda]] area in [[Telangana]] and [[Karnataka]], regions of [[India]], as well as in [[Samanalawewa]] and Dehigaha Alakanda, regions of [[Sri Lanka]].<ref>{{cite news |last=Wilford |first=John Noble |title=Ancient Smelter Used Wind To Make High-Grade Steel |work=The New York Times |date=6 February 1996 |url= https://www.nytimes.com/1996/02/06/science/ancient-smelter-used-wind-to-make-high-grade-steel.html?n=Top%2FNews%2FScience%2FTopics%2FArchaeology%20and%20Anthropology}}</ref> This came to be known as [[wootz steel]], produced in South India by about the sixth century&nbsp;BC and exported globally.<ref name="SR_IISc">{{cite book |last1=Srinivasan |first1=Sharada |last2=Ranganathan |first2=Srinivasa |title=India's Legendary Wootz Steel: An Advanced Material of the Ancient World |date=2004 |publisher=National Institute of Advanced Studies |oclc=82439861 |url= http://materials.iisc.ernet.in/~wootz/heritage/WOOTZ.htm |access-date=5 December 2014 |archive-url= https://web.archive.org/web/20190211082829/http://materials.iisc.ernet.in/~wootz/heritage/WOOTZ.htm |archive-date=11 February 2019 |url-status=dead}}</ref><ref name="ann">{{cite journal |last=Feuerbach |first=Ann |title=An investigation of the varied technology found in swords, sabres and blades from the Russian Northern Caucasus |url= https://www.es.ucl.ac.uk/iams/jour_25/iams25_Feuerbach.pdf |journal=IAMS |volume=25 |date=2005 |pages=27–43 (p. 29) |url-status=dead |archive-url= https://web.archive.org/web/20110430044256/https://www.es.ucl.ac.uk/iams/jour_25/iams25_Feuerbach.pdf |archive-date=30 April 2011}}</ref> The steel technology existed prior to 326&nbsp;BC in the region as they are mentioned in literature of [[Sangam literature|Sangam Tamil]], [[Arabic]], and [[Latin]] as the finest steel in the world exported to the Roman, Egyptian, Chinese and Arab worlds at that time – what they called ''Seric Iron''.<ref>{{cite journal |last=Srinivasan |first=Sharada |date=1994 |title=Wootz crucible steel: a newly discovered production site in South India |journal=Papers from the Institute of Archaeology |volume=5 |pages=49–59 |doi=10.5334/pia.60 |doi-access=free}}</ref> A [[Tissamaharama Tamil Brahmi inscription|200 BC Tamil trade guild in Tissamaharama]], in the South East of Sri Lanka, brought with them some of the oldest iron and steel artifacts and production processes to the island from the [[classical antiquity|classical period]].<ref>Hobbies – Volume 68, Issue 5 – p. 45. Lightner Publishing Company (1963)</ref><ref name="Mahathevan">{{cite news |url= http://www.hindu.com/2010/06/24/stories/2010062451701100.htm |archive-url= https://web.archive.org/web/20100701211040/http://www.hindu.com/2010/06/24/stories/2010062451701100.htm |url-status=dead |archive-date=1 July 2010 |title=An epigraphic perspective on the antiquity of Tamil |last=Mahathevan |first=Iravatham |date=24 June 2010 |work=[[The Hindu]] |access-date=31 October 2010}}</ref><ref name="Ragupathy">{{cite news |url= http://www.tamilnet.com/art.html?catid=79&artid=32303 |title=Tissamaharama potsherd evidences ordinary early Tamils among population |last=Ragupathy |first=P. |date=28 June 2010 |work=Tamilnet |access-date=31 October 2010}}</ref> The Chinese and locals in [[Anuradhapura]], Sri Lanka had also adopted the production methods of creating wootz steel from the [[Chera Dynasty]] Tamils of South India by the 5th century&nbsp;AD.<ref name="needham volume 4 part 1 282">{{cite book |last=Needham |first=Joseph |date=1986 |title=Science and Civilization in China: Volume 4, Part 1, Civil Engineering and Nautics |location=Taipei |publisher=Caves Books |page=282 |isbn=0-521-05802-3 |url= https://monoskop.org/images/7/70/Needham_Joseph_Science_and_Civilisation_in_China_Vol_4-1_Physics_and_Physical_Technology_Physics.pdf |access-date=4 August 2017 |archive-url= https://web.archive.org/web/20170703010030/https://monoskop.org/images/7/70/Needham_Joseph_Science_and_Civilisation_in_China_Vol_4-1_Physics_and_Physical_Technology_Physics.pdf |archive-date=3 July 2017 |url-status=dead}}</ref><ref name="Ancient and Mediaeval India. Vol.2 by Charlotte Speir Manning p.365">{{Cite book |url= https://books.google.com/books?id=nmESJR3a0RYC&pg=PA365 |title=Ancient and Mediæval India. Volume 2 |isbn=978-0-543-92943-3 |last1=Manning |first1=Charlotte Speir}}</ref> In Sri Lanka, this early steel-making method employed a unique wind furnace, driven by the monsoon winds, capable of producing high-carbon steel.<ref name="Juleff1">{{cite journal |last=Juleff |first=G. |title=An ancient wind powered iron smelting technology in Sri Lanka |journal=[[Nature (journal)|Nature]] |volume=379 |issue=3 |pages=60–63 |date=1996 |doi=10.1038/379060a0 |bibcode=1996Natur.379...60J |s2cid=205026185}}</ref><ref name="Herbert Henery Coghlan 1977 pp 99-100">Coghlan, Herbert Henery. (1977). ''Notes on prehistoric and early iron in the Old World''. Oxprint. pp. 99–100</ref> Since the technology was acquired from the [[Tamilians]] from South India,<ref name="Ancient and Medieval India. Vol.2 by Charlotte Speir Manning p.365">{{Cite book |last1=Manning |first1=Charlotte Speir |url= https://books.google.com/books?id=nmESJR3a0RYC&pg=PA365 |title=Ancient and Medieval India. Volume 2 |isbn=978-0-543-92943-3}}</ref> the origin of steel technology in India can be conservatively estimated at 400&ndash;500&nbsp;BC.<ref name="SR_IISc" /><ref name="Herbert Henery Coghlan 1977 pp 99-100" />

The manufacture of [[wootz steel]] and [[Damascus steel]], famous for its durability and ability to hold an edge, may have been taken by the Arabs from Persia, who took it from India. {{cns|It was originally created from several different materials including various [[trace element]]s, apparently ultimately from the writings of [[Zosimos of Panopolis]].|date=December 2023}} In 327&nbsp;BC, [[Alexander the Great]] was rewarded by the defeated King [[Porus the Elder|Porus]], not with gold or silver but with 30&nbsp;pounds of steel.<ref>{{cite book |last=Durant |first=Will |title=The Story of Civilization, Our Oriental Heritage |date=1942 |publisher=Simon & Schuster |isbn=0-671-54800-X |page=529 |url= https://archive.org/details/storyofcivilizat035369mbp/page/529}}</ref> A recent study has speculated that [[carbon nanotubes]] were included in its structure, which might explain some of its legendary qualities, though, given the technology of that time, such qualities were produced by chance rather than by design.<ref>{{cite journal |title=Sharpest cut from nanotube sword |first=Katharine |last=Sanderson |date=15 November 2006 |doi=10.1038/news061113-11 |journal=Nature News |s2cid=136774602 |doi-access=free}}</ref> Natural wind was used where the soil containing iron was heated by the use of wood. The [[ancient Sinhalese]] managed to extract a ton of steel for every 2&nbsp;tons of soil,<ref name="Juleff1" /> a remarkable feat at the time. One such furnace was found in Samanalawewa and archaeologists were able to produce steel as the ancients did.<ref name="Juleff1" /><ref>{{cite journal |last1=Wayman |first1=M. L. |last2=Juleff |first2=G. |title=Crucible Steelmaking in Sri Lanka |journal=Historical Metallurgy |volume=33 |issue=1 |date=1999 |page=26}}</ref>

[[Crucible steel]], formed by slowly heating and cooling pure iron and carbon (typically in the form of charcoal) in a crucible, was produced in [[Merv]] by the 9th to 10th century&nbsp;AD.<ref name="ann" /> In the 11th century, there is evidence of the production of steel in [[Song dynasty|Song China]] using two techniques: a "berganesque" method that produced inferior, inhomogeneous steel, and a precursor to the modern [[Bessemer process]] that used partial [[decarburization]] via repeated forging under a [[cold blast]].<ref>{{cite journal |last=Hartwell |first=Robert |title=Markets, Technology and the Structure of Enterprise in the Development of the Eleventh Century Chinese Iron and Steel Industry |journal=[[Journal of Economic History]] |volume=26 |date=1966 |pages=53–54 |doi=10.1017/S0022050700061842 |s2cid=154556274}}</ref>

===Modern===
[[File:Bessemer Converter Sheffield.jpg|thumb|upright|A [[Bessemer process|Bessemer converter]] in [[Sheffield]], England]]
Since the 17th century, the first step in European steel production has been the smelting of iron ore into [[pig iron]] in a [[blast furnace]].<ref name="Tylecote">{{cite book |last=Tylecote |first=R. F. |date=1992 |title=A History of Metallurgy |edition=2nd |publisher=Institute of Materials |location=London |pages=95–99, 102–105 |isbn=0-901462-88-8}}</ref>{{page needed|date=April 2024}} Originally employing charcoal, modern methods use [[coke (fuel)|coke]], which has proven more economical.<ref>{{cite book |last=Raistrick |first=A. |date=1953 |title=A Dynasty of Ironfounders}}</ref>{{page needed|date=April 2024}}<ref>{{cite book |last=Hyde |first=C. K. |date=1977 |title=Technological Change and the British Iron Industry |publisher=Princeton University Press}}</ref>{{page needed|date=April 2024}}<ref>{{cite book |last=Trinder |first=B. |date=2000 |title=The Industrial Revolution in Shropshire |edition=3rd |location=Chichester |publisher=Phillimore |isbn=9781860771330}}</ref>{{page needed|date=April 2024}}

====Processes starting from bar iron====
{{Main|Blister steel|Crucible steel}}
In these processes, [[pig iron]] made from raw iron ore was refined (fined) in a [[finery forge]] to produce [[bar iron]], which was then used in steel-making.<ref name="Tylecote" />

The production of steel by the [[cementation process]] was described in a treatise published in Prague in 1574 and was in use in [[Nuremberg]] from 1601. A similar process for [[case hardening]] armour and files was described in a book published in [[Naples]] in 1589. The process was introduced to England in about 1614 and used to produce such steel by Sir [[Basil Brooke (metallurgist)|Basil Brooke]] at [[Coalbrookdale]] during the 1610s.{{sfnp|Barraclough|1984a|pp=48–52}}

The raw material for this process were bars of iron. During the 17th century, it was realized that the best steel came from [[oregrounds iron]] of a region north of [[Stockholm]], Sweden. This was still the usual raw material source in the 19th century, almost as long as the process was used.<ref>{{cite journal |last=King |first=P. W. |title=The Cartel in Oregrounds Iron: trading in the raw material for steel during the eighteenth century |journal=Journal of Industrial History |volume=6 |issue=1 |date=2003 |pages=25–49}}</ref><ref name="britannicaironandsteel">{{cite book |chapter=Iron and steel industry |title=Encyclopædia Britannica |date=2007}}</ref>

Crucible steel is steel that has been melted in a [[crucible]] rather than having been [[forging|forged]], with the result that it is more homogeneous. Most previous furnaces could not reach high enough temperatures to melt the steel. The early modern crucible steel industry resulted from the invention of [[Benjamin Huntsman]] in the 1740s. Blister steel (made as above) was melted in a crucible or in a furnace, and cast (usually) into ingots.<ref name="britannicaironandsteel" />{{sfnp|Barraclough|1984b}}{{page needed|date=April 2024}}

====Processes starting from pig iron====
[[File:Siemens Martin Ofen Brandenburg.jpg|thumb|An [[open hearth furnace]] in the Museum of Industry in [[Brandenburg]], Germany]]
[[File:Allegheny Ludlum steel furnace.jpg|thumb|White-hot steel pouring out of an electric arc furnace in [[Brackenridge, Pennsylvania]]]]
The modern era in [[steelmaking]] began with the introduction of [[Henry Bessemer]]'s [[Bessemer process|process]] in 1855, the raw material for which was pig iron.<ref>{{cite book |title=History of the Manufacture of Iron in All Ages |last=Swank |first=James Moore |isbn=0-8337-3463-6 |date=1892 |publisher=Burt Franklin}}</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 |chapter=Bessemer process |chapter-url= https://www.britannica.com/technology/Bessemer-process |volume=2 |page=168 |title=[[Encyclopædia Britannica]] |edition=online |date=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 1952,<ref name="zs">{{cite news |last1=Sherman |first1=Zander |title=How my great-grandfather's Dofasco steel empire rose and fell, and his descendants with it |url= https://www.theglobeandmail.com/business/rob-magazine/article-how-my-great-grandfathers-dofasco-steel-empire-rose-and-fell-and-his/ |work=[[The Globe and Mail]] |date=4 September 2019}}</ref> 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 |chapter=Basic oxygen process |title=[[Encyclopædia Britannica]] |date=2007}}</ref> and because, with respect to the open hearth process, the same quantity of steel from a BOS process is manufactured in one-twelfth the time.<ref name="zs" /> 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&nbsp;metric ton), and are thus generally only economical when there is a plentiful supply of cheap electricity.{{sfnp|Fruehan|Wakelin|1998|pp=48–52}}

==Industry==
{{See also|History of the steel industry (1850–1970)|History of the steel industry (1970–present)|Global steel industry trends|Steel production by country|List of steel producers}}
[[File:Steel production by country map 2023.png|thumb|upright=1.5|Steel production (in million&nbsp;tons) by country as of 2023]]
The steel industry is often considered an indicator of economic progress, because of the critical role played by steel in infrastructural and overall [[economic development]].<ref>{{cite web |title=Steel Industry |url= http://bx.businessweek.com/steel-industry/ |access-date=12 July 2009 |url-status=dead |archive-url= https://web.archive.org/web/20090618230340/http://bx.businessweek.com/steel-industry/ |archive-date=18 June 2009}}</ref> In 1980, there were more than 500,000 U.S. steelworkers. By 2000, the number of steelworkers had fallen to 224,000.<ref>"''[https://books.google.com/books?id=iOgfSDKecCcC&pg=PA4557 Congressional Record V. 148, Pt. 4, April 11, 2002 to April 24, 2002]''". [[United States Government Printing Office]].</ref>

The [[boom and bust|economic boom]] in China and India caused a massive increase in the demand for steel. Between 2000 and 2005, world steel demand increased by 6%. Since 2000, several Indian<ref>{{cite web |url= http://csmonitor.com/2007/0212/p07s02-wosc.html |title=India's steel industry steps onto world stage |access-date=12 July 2009 |work=Cristian Science Monitor |last=Chopra |first=Anuj |date=12 February 2007}}</ref> and Chinese<ref>{{cite web |title=Worldsteel &#124; World crude steel output decreases by −2.8% in 2015 |url= https://www.worldsteel.org/media-centre/press-releases/2016/--World-crude-steel-output-decreases-by--2.8--in-2015.html |url-status=dead |archive-url= https://web.archive.org/web/20170202084313/http://www.worldsteel.org/media-centre/Press-releases/2016/--World-crude-steel-output-decreases-by--2.8--in-2015.html |archive-date=2 February 2017 |access-date=26 December 2016}}</ref> steel firms have expanded to meet demand, such as [[Tata Steel]] (which bought [[Corus Group]] in 2007), [[Baosteel Group]] and [[Shagang Group]]. {{Asof|2017}}, though, [[ArcelorMittal]] is the world's [[List of steel producers|largest steel producer]].<ref>{{cite web |url= https://www.worldsteel.org/en/dam/jcr:1a0978ce-d387-4ce9-8d1b-5f929f343ac1/2017_2016+top+steel+producers_Extended+list.pdf |publisher=World Steel Association |title=Top Steelmakers in 2017 |access-date=22 August 2018 |archive-url= https://web.archive.org/web/20180823005844/https://www.worldsteel.org/en/dam/jcr:1a0978ce-d387-4ce9-8d1b-5f929f343ac1/2017_2016+top+steel+producers_Extended+list.pdf |archive-date=23 August 2018 |url-status=dead}}</ref> 

In 2005, the [[British Geological Survey]] stated [[China]] was the top steel producer with about one-third of the world share; [[Japan]], [[Russia]], and the [[United States]] were second, third, and fourth, respectively, according to the survey.<ref>{{cite web |title=Long-term planning needed to meet steel demand |work=The News |date=1 March 2008 |url= http://www.hellenicshippingnews.com/index.php?option=com_content&task=view&id=1576&Itemid=46 |access-date=2 November 2010 |archive-url= https://archive.today/20240525020105/https://www.webcitation.org/5twr3Sstf?url=http://www.hellenicshippingnews.com/index.php%3Foption=com_content&task=view&id=1576&Itemid=46 |archive-date=25 May 2024 |url-status=dead}}</ref> The large production capacity of steel results also in a significant amount of carbon dioxide emissions inherent related to the main production route. 

At the end of 2008, the steel industry faced a sharp downturn that led to many cut-backs.<ref>{{cite news |url= https://www.nytimes.com/2009/01/02/business/02steel.html?_r=1&partner=permalink&exprod=permalink |title=Steel Industry, in Slump, Looks to Federal Stimulus |last=Uchitelle |first=Louis |author-link=Louis Uchitelle |date=1 January 2009 |newspaper=The New York Times |access-date=19 July 2009}}</ref>

In 2021, it was estimated that around 7% of the global greenhouse gas emissions resulted from the steel industry.<ref>{{Cite web |last=Rossi |first=Marcello |date=4 August 2022 |title=The Race to Remake the $2.5 Trillion Steel Industry With Green Steel |url= https://singularityhub.com/2022/08/04/the-race-to-remake-the-2-5-trillion-steel-industry-with-green-steel/ |access-date=6 August 2022 |website=Singularity Hub}}</ref><ref>{{Cite web |title=Global Steel Industry's GHG Emissions |url= https://www.globalefficiencyintel.com/new-blog/2021/global-steel-industrys-ghg-emissions |access-date=6 August 2022 |website=Global Efficiency Intelligence |date=6 January 2021}}</ref> Reduction of these emissions are expected to come from a shift in the main production route using cokes, more recycling of steel and the application of [[carbon capture and storage]] technology.

==Recycling==
{{Main|Ferrous metal recycling}}
Steel is one of the world's most-recycled materials, with a [[Ferrous metal recycling|recycling rate]] of over 60% globally;<ref name="encarta-recycling">{{cite encyclopedia |last=Hartman |first=Roy A. |date=2009 |title=Recycling |encyclopedia=[[Encarta]] |url= http://encarta.msn.com/encyclopedia_761556346/Recycling.html |archive-url= https://web.archive.org/web/20080414215636/http://encarta.msn.com/encyclopedia_761556346/Recycling.html |archive-date=14 April 2008}}</ref> in the United States alone, over {{convert|82,000,000|metric ton|LT ST}} were recycled in the year 2008, for an overall recycling rate of 83%.<ref name="fenton-2008">{{cite book |last=Fenton |first=Michael D. |date=2008 |chapter=Iron and Steel Scrap |title=Minerals Yearbook 2008 |volume=1: Metals and Minerals |publisher=[[United States Government Publishing Office]] |editor=United States Geological Survey |editor-link=United States Geological Survey |isbn=978-1-4113-3015-3}}</ref>

As more steel is produced than is scrapped, the amount of recycled raw materials is about 40% of the total of steel produced – in 2016, {{convert|1,628,000,000|t}} of crude steel was produced globally, with {{convert|630,000,000|t}} recycled.<ref>{{Cite web |url= https://www.worldsteel.org/en/dam/jcr:16ad9bcd-dbf5-449f-b42c-b220952767bf/fact_raw%2520materials_2018.pdf |title=Steel and raw materials |last=The World Steel Association |date=1 March 2018 |archive-url=https://web.archive.org/web/20180809152848/https://www.worldsteel.org/en/dam/jcr:16ad9bcd-dbf5-449f-b42c-b220952767bf/fact_raw%20materials_2018.pdf |archive-date=9 August 2018 |url-status=dead }}</ref>

==Contemporary==
{{See also|Steel grades}}
[[File:Bethlehem Steel.jpg|thumb|[[Bethlehem Steel]] in [[Bethlehem, Pennsylvania]] was one of the world's largest manufacturers of steel before its closure in 2003.]]
===Carbon===
{{Main|Carbon steel}}
Modern steels are made with varying combinations of alloy metals to fulfil many purposes.<ref name="materialsengineer" /> [[Carbon steel]], composed simply of [[iron]] and [[carbon]], accounts for 90% of steel production.<ref name="EM2" /> [[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 |work=SchoolScience.co.uk |access-date=14 August 2007 |archive-date=21 September 2020 |archive-url= https://web.archive.org/web/20200921025905/http://resources.schoolscience.co.uk/Corus/16plus/steelch3pg1.html |url-status=dead}}</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 |access-date=1 March 2007 |archive-url= https://web.archive.org/web/20110525170931/http://www.intota.com/experts.asp?strSearchType=all&strQuery=dual%2Dphase+steel |archive-date=25 May 2011 |url-status=dead}}</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 |access-date=1 March 2007 |url-status=dead |archive-url= https://web.archive.org/web/20071223184922/http://www.wkm.mw.tum.de/Forschung/projekte_html/transtrip.html |archive-date=23 December 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 |last1=Mirko |first1=Centi |last2=Saliceti |first2=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 |archive-url= https://web.archive.org/web/20080307200557/http://www.dimet.unige.it/resta/studenti/2002/27839/26/TWIP%2CTRIPandDualphase%20mirko.doc |archive-date=7 March 2008 |access-date=1 March 2007 |url-status=dead}}</ref>

Carbon Steels are often [[hot-dip galvanizing|galvanized]], through [[Hot-dip galvanization|hot-dip]] or electroplating in [[zinc]] for protection against rust.<ref>{{cite book |chapter=Galvanic protection |title=[[Encyclopædia Britannica]] |date=2007}}</ref>

===Alloy===
{{Main|Alloy}}
[[File:Alcator C-Mod superstructure forging 1.jpg|thumb|upright|Forging a structural member out of steel]] 
[[File:Rust-AH-2022.jpg|thumb|Cor-Ten rust coating]]
[[Stainless steel]] contains a minimum of 11% chromium, often combined with nickel, to resist [[corrosion]]. Some stainless steels, such as the [[Allotropes of 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]] |access-date=30 July 2006}}</ref> Corrosion-resistant steels are abbreviated as CRES.

Alloy steels are plain-carbon steels in which small amounts of alloying elements like chromium and vanadium have been added. 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 |archive-url= https://web.archive.org/web/20071222180444/http://aisc.org/MSCTemplate.cfm?Section=Steel_Interchange2&Template=%2FCustomSource%2FFaq%2FSteelInterchange.cfm&FaqID=2311 |archive-date=22 December 2007 |title=Steel Interchange |publisher=American Institute of Steel Construction |access-date=28 February 2007 |url-status=dead}}</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 |access-date=19 July 2009 |url-status=dead |archive-url= https://web.archive.org/web/20090225211327/http://steel.keytometals.com/default.aspx?ID=CheckArticle&NM=103 |archive-date=25 February 2009}}</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. [[Mangalloy|Hadfield steel]], named after [[Robert Hadfield]], or manganese steel, contains 12–14% manganese which, when abraded, strain-hardens to form a very hard skin which resists wearing. Uses of this particular alloy include [[Continuous track|tank tracks]], [[bulldozer#Blade|bulldozer blade]] edges, and cutting blades on the [[jaws of life]].<ref name="auto1">{{cite book |title=Sheffield Steel and America: A Century of Commercial and Technological Independence |publisher=Cambridge University Press |date=1987 |editor-last=Tweedale |editor-first=Geoffrey |pages=57–62}}</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 |date=2004 |edition=3rd. |url= http://astm.org/BOOKSTORE/PUBS/DS67B_SampleChapter.pdf |archive-url= https://web.archive.org/web/20070127135646/http://www.astm.org/BOOKSTORE/PUBS/DS67B_SampleChapter.pdf |archive-date=27 January 2007 |isbn=0-8031-3362-6 |url-status=dead}}</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 pp. 1–5</ref> The [[Japanese Industrial Standards|JIS]] also defines a series of steel grades that are being used extensively in [[Japan]] as well as in developing countries.

==Uses==
[[File:Steel-wool.jpg|thumb|A roll of [[steel wool]]]]
Iron and steel are used widely in the construction of roads, railways, other infrastructure, appliances, and buildings. Most large modern structures, such as [[stadium#The modern stadium|stadiums]] and skyscrapers, [[Steel bridge|bridges]], and airports, are supported by a steel skeleton. Even those with a concrete structure employ steel for reinforcing. It sees widespread use in [[major appliances]] and [[automobile|cars]]. Despite the growth in usage of [[aluminium]], steel is still the main material for car bodies. Steel is used in a variety of other construction materials, such as bolts, [[nail (engineering)|nails]] and [[screw]]s, and other household products and cooking utensils.<ref>{{cite encyclopedia |last=Ochshorn |first=Jonathan |title=Steel in 20th Century Architecture |encyclopedia=Encyclopedia of Twentieth Century Architecture |date=11 June 2002 |url= http://www.ochshorndesign.com/cornell/writings/steel.html |access-date=26 April 2010}}</ref>

Other common applications include [[shipbuilding]], [[pipeline transport|pipelines]], [[mining]], [[offshore construction]], [[aerospace]], [[white goods]] (e.g. [[washing machine]]s), [[heavy equipment]] such as bulldozers, office furniture, [[steel wool]], [[tool]], and [[armour]] in the form of personal vests or [[vehicle armour]] (better known as [[rolled homogeneous armour]] in this role).

===Historical===
[[File:Carbon steel knife.jpg|thumb|A carbon steel knife]]
Before the introduction of the [[Bessemer process]] and other modern production techniques, steel was expensive and was only used where no cheaper alternative existed, particularly for the cutting edge of [[knives]], [[razors]], [[sword]]s, and other items where a hard, sharp edge was needed. It was also used for [[spring (device)|springs]], including those used in [[clock|clocks and watches]].<ref name="britannicaironandsteel" />

With the advent of faster and cheaper production methods, steel has become easier to obtain and much cheaper. It has replaced wrought iron for a multitude of purposes. However, the availability of plastics in the latter part of the 20th century allowed these materials to replace steel in some applications due to their lower fabrication cost and weight.<ref>{{cite book |chapter=Materials science |title=[[Encyclopædia Britannica]] |edition=online |date=2007 |chapter-url= https://www.britannica.com/technology/materials-science |last1=Venables |first1=John D. |last2=Girifalco |first2=Louis A. |last3=Patel |first3=C. Kumar N. |last4=McCullough |first4=R. L. |last5=Marchant |first5=Roger Eric |last6=Kukich |first6=Diane S.}}</ref> [[Carbon-fiber reinforced polymer|Carbon fibre]] is replacing steel in some cost-insensitive applications such as sports equipment and high-end automobiles.

===Long===
[[File:The viaduct La Polvorilla, Salta Argentina.jpg|thumb|A steel bridge]]
[[File:Steel tower.jpg|thumb|A steel pylon suspending [[overhead power line]]s]]
* As reinforcing bars and mesh in [[reinforced concrete]]
* [[Railroad tracks]]
* [[Structural steel]] in modern buildings and bridges
* [[Wire]]s
* Input to reforging applications

===Flat carbon===
* [[Major appliance]]s
* [[Magnetic core]]s
* The inside and outside body of automobiles, trains, and ships.

===Weathering (COR-TEN)===
{{Main|Weathering steel}}
* [[Intermodal container]]s
* Outdoor sculptures
* [[Architecture]]
* [[Highliner]] [[train car]]s

===Stainless===
{{Main|Stainless steel}}
[[File:Sauce boat.jpg|thumb|A stainless steel [[sauce boat|gravy boat]]]]
{{div col|colwidth=20em}}
* [[Cutlery]]
* [[Ruler]]s
* [[Surgical instrument]]s
* [[Watch]]es
* [[Gun]]s
* [[passenger car (rail)|Rail passenger vehicles]]
* [[Tablet computer|Tablets]]
* [[Waste container|Trash Cans]]
* [[Body piercing jewellery]]
* Inexpensive [[Ring (jewellery)|rings]]
* Components of [[spacecraft]] and [[space station]]s
{{div col end}}

===Low-background===
{{Main|Low-background steel}}

Steel manufactured after [[World War II]] is [[radioactive contamination|contaminated]] with [[radionuclide]]s, because steel production uses air, and the atmosphere is contaminated with radioactive dust produced by [[nuclear weapons testing]]. Low-background steel, steel manufactured prior to 1945, is used for certain radiation-sensitive applications such as [[Geiger counter]]s and [[radiation shielding]].

==See also==
{{Portal|Chemistry}}
{{Div col|colwidth=20em|small=yes}}
* [[Bulat steel]]
* [[Direct reduction]]
* [[Carbon steel]]
* [[Damascus steel]]
* [[Galvanizing]]
* [[History of the steel industry (1970–present)]]
* [[Iron in folklore]]
* [[List of blade materials]]
* [[Machinability]]
* [[Noric steel]]
* [[Pelletizing]]
* [[Rolling (metalworking)|Rolling]]
* [[Rolling mill]]
* [[Rust Belt]]
* [[Second Industrial Revolution]]
* [[Silicon steel]]
* [[Steel abrasive]]
* [[Steel mill]]
* [[Tamahagane]], used in Japanese swords
* [[Tinning|Tinplate]]
* [[Toledo steel]]
* [[Wootz steel]]
{{div col end}}

==References==
{{Reflist}}

===Bibliography===
* {{Cite book |last1=Ashby |first1=Michael F. |author1-link=Michael F. Ashby |last2=Jones |first2=David Rayner Hunkin |title=An introduction to microstructures, processing and design |publisher=Butterworth-Heinemann |date=1992}}
* {{Cite book |last=Barraclough |first=K. C. |title=Steel before Bessemer |volume=I, Blister Steel: The Birth of an Industry |date=1984 |publisher=Metals Society |location=London |ref={{sfnref|Barraclough|1984a}}}}
* {{Cite book |last=Barraclough |first=K. C. |title=Steel Before Bessemer |volume=II, Crucible Steel: The Growth of Technology |date=1984 |publisher=Metals Society |location=London |ref={{sfnref|Barraclough|1984b}}}}
* {{Cite book |last1=Bugayev |first1=K. |last2=Konovalov |first2=Y. |last3=Bychkov |first3=Y. |last4=Tretyakov |first4=E. |last5=Savin |first5=Ivan V. |title=Iron and Steel Production |publisher=Minerva Group |date=2001 |url= https://books.google.com/books?id=MJdIVtmwuUsC |isbn=978-0-89499-109-7}}
* {{Cite book |last=Davidson |first=H. R. Ellis |title=The Sword in Anglo-Saxon England: Its Archaeology and Literature |date=1994 |publisher=Boydell Press |isbn=0-85115-355-0 |location=Woodbridge, Suffolk}}
* {{Cite book |last1=Degarmo |first1=E. Paul |last2=Black |first2=J. T. |last3=Kohser |first3=Ronald A. |title=Materials and Processes in Manufacturing |publisher=Wiley |date=2003 |edition=9th |isbn=0-471-65653-4}}
* {{Cite book |last1=Fruehan |first1=R. J. |last2=Wakelin |first2=David H. |title=The Making, Shaping, and Treating of Steel |date=1998 |publisher=AISE Steel Foundation |isbn=0-930767-03-9 |edition=11th |location=Pittsburgh}}
* {{Cite book |last1=Smith |first1=William F. |last2=Hashemi |first2=Javad |title=Foundations of Materials Science and Engineering |edition=4th |date=2006 |publisher=McGraw-Hill |isbn=0-07-295358-6}}

==Further reading==
* {{cite book |last=Reutter |first=Mark |title=Making Steel: Sparrows Point and the Rise and Ruin of American Industrial Might |publisher=University of Illinois Press |date=2005 |isbn=978-0-252-07233-8 |url= https://books.google.com/books?id=bdkUfDoY24QC}}
* {{cite book |last=Burn |first=Duncan |title=The Economic History of Steelmaking, 1867–1939: A Study in Competition |publisher=Cambridge University Press |date=1961 |url= http://questia.com/PM.qst?a=o&d=3914930 |archive-url= https://web.archive.org/web/20120726170156/http://questia.com/PM.qst?a=o&d=3914930 |archive-date=26 July 2012}}
* {{cite book |last=Hasegawa |first=Harukiyu |title=The Steel Industry in Japan: A Comparison with Britain |publisher=Routledge |date=1996 |url= http://questia.com/PM.qst?a=o&d=108742046 |archive-url= https://web.archive.org/web/20120418193928/http://www.questia.com/PM.qst?a=o&d=108742046 |archive-date=18 April 2012}}
* {{cite book |last1=Carr |first1=J. C. |last2=Taplin |first2=W. |title=History of the British Steel Industry |publisher=Harvard University Press |date=1962 |url= http://questia.com/PM.qst?a=o&d=808791 |archive-url= https://web.archive.org/web/20120729081240/http://questia.com/PM.qst?a=o&d=808791 |archive-date=29 July 2012}}
* {{cite book |last=Scamehorn |first=H. Lee |title=Mill & Mine: The CF&I in the Twentieth Century |publisher=University of Nebraska Press |date=1992 |url= http://questia.com/PM.qst?a=o&d=94821694 |archive-url= https://web.archive.org/web/20120726043744/http://questia.com/PM.qst?a=o&d=94821694 |archive-date=26 July 2012}}
* {{cite book |editor=Verein Deutscher Eisenhüttenleute |title=Steel: A Handbook for Materials Research and Engineering |volume=1: Fundamentals |location=Berlin, Heidelberg / Düsseldorf |publisher=Springer-Verlag / Verlag Stahleisen |date=1992 |isbn=3-540-52968-3 }}
* {{cite book |editor=Verein Deutscher Eisenhüttenleute |title=Steel: A Handbook for Materials Research and Engineering |volume=2: Applications |location=Berlin, Heidelberg / Düsseldorf |publisher=Springer-Verlag / Verlag Stahleisen |date=1993 |isbn=3-540-54075-X }}
* {{cite book |last=Verhoeven |first=John D. |title=Metallurgy for the Non-Metallurgist |publisher=[[American Society for Metals|ASM International]] |date=2007 |isbn=9781615030569 |url= https://books.google.com/books?id=brpx-LtdCLYC&pg=PA26}}
* {{cite book |last=Warren |first=Kenneth |title=Big Steel: The First Century of the United States Steel Corporation, 1901–2001 |publisher=University of Pittsburgh Press |date=2001 |url= http://eh.net/bookreviews/library/0558 |archive-url= https://web.archive.org/web/20100501214026/http://eh.net/bookreviews/library/0558 |archive-date=1 May 2010}}

==External links==
{{Commons|Steel}}
{{Wikiquote}}
{{Wiktionary|steel}}
* [https://worldsteel.org/ Official website] of the [[World Steel Association]] (WorldSteel.org)
** [https://steeluniversity.org/ SteelUniversity.org] – online steel education resources, an initiative of World Steel Association
* [https://www.matdat.com/ MATDAT Database of Properties of Unalloyed, Low-Alloy and High-Alloy Steels] – obtained from published results of materials testing

{{Iron and steel production}}
{{Recycling}}
{{Authority control}}

[[Category:Steel| ]]
[[Category:2nd-millennium BC introductions]]
[[Category:Building materials]]
[[Category:Roofing materials]]