Editing Iron (section)

=={{visible anchor|Production of metallic iron|Industrial production}}==
[[File:Iron powder.JPG|thumb|right|[[Iron powder]]]]

===Laboratory routes===
For a few limited purposes when it is needed, pure iron is produced in the laboratory in small quantities by reducing the pure oxide or hydroxide with hydrogen, or forming iron pentacarbonyl and heating it to 250 °C so that it decomposes to form pure iron powder.{{sfn|Greenwood|Earnshaw|1997|p=1071}} Another method is electrolysis of ferrous chloride onto an iron cathode.<ref>Lux, H. (1963) "Metallic Iron" in ''Handbook of Preparative Inorganic Chemistry'', 2nd Ed. G. Brauer (ed.), Academic Press, NY. Vol. 2. pp. 1490–91.</ref>

===Main industrial route===
{{See also|Iron ore}}
{|class="wikitable floatright"
|+Iron production 2009 (million [[tonnes]])<ref>[https://web.archive.org/web/20120304124724/https://www.worldsteel.org/statistics/statistics-archive/yearbook-archive.html Steel Statistical Yearbook 2010]. World Steel Association</ref>{{dubious|reason=China+Australia+Brazil>World on iron ore???|date=January 2023}}
!Country!![[Iron ore]]!![[Pig iron]]!![[Direct reduced iron|Direct iron]]!![[Steel]]
|-
|{{flag|China}}|| 1,114.9||549.4 || || 573.6
|-
|{{flag|Australia}}||393.9|| 4.4|| ||5.2
|-
|{{flag|Brazil}}||305.0||25.1 ||0.011 ||26.5
|-
|{{flag|Japan}}|| || 66.9|| || 87.5
|-
|{{flag|India}}||257.4||38.2 || 23.4||63.5
|-
|{{flag|Russia}}||92.1|| 43.9|| 4.7||60.0
|-
|{{flag|Ukraine}}||65.8|| 25.7|| ||29.9
|-
|{{flag|South Korea}}|| 0.1|| 27.3|| ||48.6
|-
|{{flag|Germany}}||0.4 || 20.1||0.38 ||32.7
|-
!World!! 1,594.9!!914.0!! 64.5!! 1,232.4
|}
Nowadays, the industrial production of iron or steel consists of two main stages. In the first stage, iron ore is [[redox|reduced]] with [[coke (fuel)|coke]] in a [[blast furnace]], and the molten metal is separated from gross impurities such as [[silicate mineral]]s. This stage yields an alloy – [[pig iron]] – that contains relatively large amounts of carbon.<!--"Alternatively, it may be directly reduced." – what does this mean?--> In the second stage, the amount of carbon in the pig iron is lowered by oxidation to yield wrought iron, steel, or cast iron.{{sfn|Greenwood|Earnshaw|1997|p=1073}}<!--https://books.google.com/books?id=xkVPNtRagDkC--> Other metals can be added at this stage to form [[alloy steel]]s.

====Blast furnace processing====
{{Main|Blast furnace}}
The blast furnace is loaded with iron ores, usually [[hematite]] {{chem2|Fe2O3}} or [[magnetite]] {{chem2|Fe3O4}}, along with coke ([[coal]] that has been separately baked to remove volatile components) and [[Flux (metallurgy)|flux]] ([[limestone]] or [[Dolomites|dolomite]]). "Blasts" of air pre-heated to 900 °C (sometimes with oxygen enrichment) is blown through the mixture, in sufficient amount to turn the carbon into [[carbon monoxide]]:{{sfn|Greenwood|Earnshaw|1997|p=1073}}

:{{chem2 | 2 C + O2 -> 2 CO }}

This reaction raises the temperature to about 2000 °C. The carbon monoxide reduces the iron ore to metallic iron:{{sfn|Greenwood|Earnshaw|1997|p=1073}}

:{{chem2 | Fe2O3 + 3 CO -> 2 Fe + 3 CO2 }}

Some iron in the high-temperature lower region of the furnace reacts directly with the coke:{{sfn|Greenwood|Earnshaw|1997|p=1073}}
:{{chem2 | 2 Fe2O3 + 3 C -> 4 Fe + 3 CO2 }}

The flux removes silicaceous minerals in the ore, which would otherwise clog the furnace: The heat of the furnace decomposes the carbonates to [[calcium oxide]], which reacts with any excess [[silica]] to form a [[slag]] composed of [[calcium silicate]] {{chem2|CaSiO3}} or other products. At the furnace's temperature, the metal and the slag are both molten. They collect at the bottom as two immiscible liquid layers (with the slag on top), that are then easily separated.{{sfn|Greenwood|Earnshaw|1997|p=1073}} The slag can be used as a material in [[road]] construction or to improve mineral-poor soils for [[agriculture]].<ref name="Biddle" />

Steelmaking thus remains one of the largest industrial contributors of CO<sub>2</sub> emissions in the world.<ref>{{Cite journal |last1=Wang |first1=Peng |last2=Ryberg |first2=Morten |last3=Yang |first3=Yi |last4=Feng |first4=Kuishuang |last5=Kara |first5=Sami |last6=Hauschild |first6=Michael |last7=Chen |first7=Wei-Qiang |date=2021-04-06 |title=Efficiency stagnation in global steel production urges joint supply- and demand-side mitigation efforts |journal=Nature Communications |volume=12 |issue=1 |pages=2066 |doi=10.1038/s41467-021-22245-6 |issn=2041-1723 |pmc=8024266 |pmid=33824307|bibcode=2021NatCo..12.2066W }}</ref>

<gallery widths=200 heights=150>
File:Chinese Fining and Blast Furnace.jpg|17th century Chinese illustration of workers at a blast furnace, making wrought iron from pig iron<ref name="song">[[Song Yingxing]] (1637): The ''Tiangong Kaiwu'' encyclopedia.</ref>
File:Iron-Making.jpg|How iron was extracted in the 19th century
File:Geography of Ohio - DPLA - aaba7b3295ff6973b6fd1e23e33cde14 (page 111) (cropped).jpg|Iron furnace in Columbus, Ohio, 1922
</gallery>

====Steelmaking====
{{Main|Steelmaking|Ironworks}}
<!-- Several other articles cover the material that might go into this section: please do not expand it excessively. This article concerns all aspects of the element iron, and should thus NOT be overburdened with details of metallurgy... Agree. Should be a summary. -->
The pig iron produced by the blast furnace process contains up to 4–5% carbon (by mass), with small amounts of other impurities like sulfur, magnesium, phosphorus, and manganese. This high level of carbon makes it relatively weak and brittle. Reducing the amount of carbon to 0.002–2.1% produces [[steel]], which may be up to 1000 times harder than pure iron. A great variety of steel articles can then be made by [[cold working]], [[hot rolling]], [[forging]], [[machining]], etc. Removing the impurities from pig iron, but leaving 2–4% carbon, results in [[cast iron]], which is cast by [[foundry|foundries]] into articles such as stoves, pipes, radiators, lamp-posts, and rails.{{sfn|Greenwood|Earnshaw|1997|p=1073}}

Steel products often undergo various [[heat treatment]]s after they are forged to shape. [[annealing (metallurgy)|Annealing]] consists of heating them to 700–800 °C for several hours and then gradual cooling. It makes the steel softer and more workable.<ref name="Verhoeven">Verhoeven, J.D. (1975) ''Fundamentals of Physical Metallurgy'', Wiley, New York, p. 326</ref>
<!--why is this in production of iron?Steel may be hardened by [[cold working]]. The metal is bent or hammered into its final shape at a relatively cool temperature. Cold forging is the stamping of a piece of steel into shape by a heavy press. Wrenches are commonly made by cold forging. Cold rolling, which involves making a thinner but harder sheet, and cold drawing, which makes a thinner but stronger wire, are two other methods of cold working. To harden the steel, it is heated to red-hot and then cooled by quenching it in the water. It becomes harder and more brittle. If it is too hardened, it is then heated to a required temperature and allowed to cool. The steel thus formed is less brittle.

[[Heat treatment]] is another way to harden steel. The steel is heated red-hot, then cooled quickly. The iron carbide molecules are decomposed by the heat, but do not have time to reform. Since the free carbon atoms are stuck, it makes the steel much harder and stronger than before.<ref name="Biddle" />

Sometimes both toughness and hardness are desired. A process called [[case hardening]] may be used. Steel is heated to about 900 °C then plunged into oil or water. Carbon from the oil can diffuse into the steel, making the surface very hard. The surface cools quickly, but the inside cools slowly, making an extremely hard surface and a durable, resistant inner layer.

Iron may be [[Passivation (chemistry)|passivated]] by dipping it into a concentrated [[nitric acid]] solution. This forms a protective layer of oxide on the metal, protecting it from further corrosion.<ref>{{cite book|url=https://www.euro-inox.org/pdf/map/Passivating_Pickling_EN.pdf |title=Picking and passivating stainless steel, Materials and Application Series, Volume 4 |publisher=Euro Inox |year=2007 |edition=2nd |isbn=978-2-87997-224-4}}</ref>-->
<gallery widths="200" heights="150">
File:LightningVolt Iron Ore Pellets.jpg|This heap of iron ore pellets will be used in steel production.
File:Melted raw-iron.jpg|A pot of molten iron being used to make steel
</gallery>

===Direct iron reduction===
Owing to environmental concerns, alternative methods of processing iron have been developed. "[[Direct reduced iron|Direct iron reduction]]" [[Sponge iron reaction|reduces iron ore]] to a ferrous lump called [[sponge iron|"sponge" iron]] or "direct" iron that is suitable for steelmaking.<ref name="Biddle" /> Two main reactions comprise the direct reduction process:

Natural gas is partially oxidized (with heat and a catalyst):<ref name="Biddle" />
:{{chem2 | 2 CH4 + O2 -> 2 CO + 4 H2 }}

Iron ore is then treated with these gases in a furnace, producing solid sponge iron:<ref name="Biddle" />
:{{chem2 | Fe2O3 + CO + 2 H2 -> 2 Fe + CO2 + 2 H2O }}

[[Silica]] is removed by adding a [[limestone]] flux as described above.<ref name="Biddle" />

===Thermite process===
{{Main|Thermite}}
Ignition of a mixture of aluminium powder and iron oxide yields metallic iron via the [[thermite reaction]]:

:{{chem2 | Fe2O3 + 2 Al -> 2 Fe + Al2O3 }}

Alternatively pig iron may be made into steel (with up to about 2% carbon) or wrought iron (commercially pure iron). Various processes have been used for this, including [[finery forge]]s, [[Puddling (metallurgy)|puddling]] furnaces, [[Bessemer converter]]s, [[open hearth furnace]]s, [[basic oxygen furnace]]s, and [[electric arc furnace]]s. In all cases, the objective is to oxidize some or all of the carbon, together with other impurities. On the other hand, other metals may be added to make alloy steels.{{sfn|Greenwood|Earnshaw|1997|p=1072}}<!-- why is this in production? The hardness of the steel depends upon its carbon content: the higher the percentage of carbon, the greater the hardness and the lesser the malleability. The properties of the steel can also be changed by several methods.-->

=== Molten oxide electrolysis ===
Molten oxide electrolysis (MOE) uses [[electrolysis]] of molten iron oxide to yield metallic iron. It is studied in laboratory-scale experiments and is proposed as a method for industrial iron production that has no direct emissions of carbon dioxide. It uses a liquid iron cathode, an anode formed from an alloy of chromium, aluminium and iron,<ref>{{cite journal |last1=Allanore |first1=Antoine |last2=Yin |first2=Lan |last3=Sadoway |first3=Donald R. |title=A new anode material for oxygen evolution in molten oxide electrolysis |journal=Nature |volume=497 |date=2013 |issue=7449 |issn=0028-0836 |doi=10.1038/nature12134 |pages=353–356|pmid=23657254 |bibcode=2013Natur.497..353A |hdl=1721.1/82073 |hdl-access=free }}</ref> and the electrolyte is a mixture of molten metal oxides into which iron ore is dissolved. The current keeps the electrolyte molten and reduces the iron oxide. Oxygen gas is produced in addition to liquid iron. The only carbon dioxide emissions come from any [[fossil fuel]]-generated electricity used to heat and reduce the metal.<ref>{{cite journal |last1=Wiencke |first1=Jan |last2=Lavelaine |first2=Hervé |last3=Panteix |first3=Pierre-Jean |last4=Petitjean |first4=Carine |last5=Rapin |first5=Christophe |title=Electrolysis of iron in a molten oxide electrolyte |journal=Journal of Applied Electrochemistry |volume=48 |issue=1 |date=2018 |issn=0021-891X |doi=10.1007/s10800-017-1143-5 |pages=115–126|doi-access=free }}</ref><ref>{{cite journal |last1=Fan |first1=Zhiyuan |last2=Friedmann |first2=S. Julio |title=Low-carbon production of iron and steel: Technology options, economic assessment, and policy |journal=Joule |volume=5 |date=2021 |issue=4 |doi=10.1016/j.joule.2021.02.018 |pages=829–862|doi-access=free |bibcode=2021Joule...5..829F }}</ref><ref>{{cite news |last1=Gallucci |first1=Maria |title=Boston Metal gets big funding boost to make green steel |url=https://www.canarymedia.com/articles/clean-industry/boston-metal-gets-big-funding-boost-to-make-green-steel |access-date=11 March 2024 |work=Canary Media |publisher=[[RMI (energy organization)|Rocky Mountain Institute]] |date=September 7, 2023}}</ref>