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{{Short description|Process for producing steel}}
[[File:SteelMill interior.jpg|thumb|upright=1.2|[[Steel mill]] with two [[arc furnace]]s]]

'''Steelmaking''' is the process of producing [[steel]] from iron ore and/or [[scrap]]. Steel has been made for millennia, and was commercialized on a massive scale in the 1850s and 1860s, using the [[Bessemer process|Bessemer]] and [[open hearth furnace|Siemens-Martin]] processes.

Currently, two major commercial processes are used. [[Basic oxygen steelmaking]] (BOS) uses liquid [[Pig iron|pig-iron]] from a [[blast furnace]] and scrap steel as the main feed materials. [[Electric arc furnace]] (EAF) steelmaking uses scrap steel or [[direct reduced iron]] (DRI). Oxygen steelmaking has become more popular over time.<ref name="turkdogan">{{cite book |last1=Turkdogan |first1=E.T. |title=Fundamentals of Steelmaking |date=1996 |publisher=[[Institute of Materials]] |isbn=9781907625732 |location=London |oclc=701103539}}</ref> 

Steelmaking is one of the most carbon emission-intensive industries. In 2020, the steelmaking industry was reported to be responsible for 7% of energy sector [[greenhouse gas emissions]].<ref>IEA (2020), Iron and Steel Technology Roadmap, IEA, Paris https://www.iea.org/reports/iron-and-steel-technology-roadmap, Licence: CC BY 4.0 </ref> The industry is seeking significant emission reductions.<ref name=":1">{{Cite web |title=Decarbonization in steel |url=https://www.mckinsey.com/industries/metals-and-mining/our-insights/decarbonization-challenge-for-steel |access-date=2021-04-03 |website=McKinsey}}</ref>

{{Toclimit}}

== Steel ==
Steel is made from iron and carbon. [[Cast iron]] is a hard, brittle material that is difficult to work, whereas steel is malleable, relatively easily formed and versatile. On its own, iron is not strong, but a low concentration of carbon – less than 1 percent, depending on the kind of steel – gives steel strength and other important properties. [[Impurity|Impurities]] such as [[nitrogen]], [[silicon]], [[phosphorus]], [[sulfur]], and excess [[carbon]] (the most important impurity) are removed, and alloying elements such as [[manganese]], [[nickel]], [[chromium]], carbon, and [[vanadium]] are added to produce different [[Steel grades|grades of steel]].  

==History==
[[Image:Bethlehem Steel.jpg|thumb|upright=1.2|[[Bethlehem Steel]] in [[Bethlehem, Pennsylvania]], was one of the world's largest manufacturers of steel before its 2003 closure.]]{{Main|Ferrous metallurgy}}

=== Early history ===
Early processes evolved during the classical era in [[Ancient China|China]], [[Ancient India|India]], [[Ancient Rome|Rome]] and among hunter-foragers in northern Sweden. The earliest means of producing steel was in a [[bloomery]].  

For much of human history, steel was made only in small quantities. Early modern methods of producing steel were often labor-intensive and highly skilled arts. The [[Bessemer process]] and subsequent developments allowed steel to become integral to the global economy.<ref name="sass">{{cite book |last1=Sass |first1=Stephen L. |title=The Substance of Civilization: Materials and Human History from the Stone Age to the Age of Silicon |date=August 2011 |publisher=[[Arcade Publishing]] |location=New York City |oclc=1078198918 |url=https://www.skyhorsepublishing.com/arcade-publishing/9781611454017/the-substance-of-civilization/ |isbn=9781611454017}}</ref>

==== China ====
A system akin to the Bessemer process originated in the 11th century in East Asia.<ref name="need">{{cite book |last=Needham |first=Joseph |url=https://books.google.com/books?id=FAud8CE5stsC |title=Science and civilisation in China, Volume 5, Part 7 |publisher=Cambridge University Press |year=2008 |isbn=9780521875660 |edition=1. publ. |location=Cambridge, UK |pages=261–5}}</ref><ref name="tan">{{cite book |last=Tanner |first=Harold |url=https://books.google.com/books?id=VIWC9wCX2c8C&pg=PA218 |title=China: A History |publisher=Hackett Publishing |year=2009 |isbn=978-0-87220-915-2 |page=218}}</ref> Hartwell wrote that the [[Song dynasty]] (960–1279 CE) innovated a "partial decarbonization" method of repeated forging of [[cast iron]] under a cold blast.<ref name="hartwell 54">{{Cite journal |last=Hartwell |first=Robert |date=March 1966 |title=Markets, Technology, and the Structure of Enterprise in the Development of the Eleventh-Century Chinese Iron and Steel Industry |journal=The Journal of Economic History |volume=26 |issue=1 |page=54 |doi=10.1017/S0022050700061842 |issn=0022-0507 |jstor=2116001 |s2cid=154556274}}</ref> [[Joseph Needham|Needham]] and Wertime described the method as a predecessor to the Bessemer process.<ref name="need" /><ref>{{cite book |last=Wertime |first=Theodore A. |url=https://archive.org/details/comingofageofste00wert |title=The coming of the age of steel |publisher=University of Chicago Press |year=1962 |url-access=registration}}</ref><ref>{{cite book |last=Temple |first=Robert K.G. |url=https://archive.org/details/geniusofchina00robe_0 |title=The Genius of China: 3000 years of science, discovery and invention |publisher=Prion |year=1999 |isbn=9781853752926 |location=London |page=[https://archive.org/details/geniusofchina00robe_0/page/49 49] |url-access=registration}}</ref> This process was first described by government official [[Shen Kuo]] (1031–1095) in 1075, when he visited Cizhou.<ref name="hartwell 54" /> Hartwell stated that the earliest center where this was practiced was perhaps the great iron-production district along the [[Henan]]–[[Hebei]] border during the 11th century.<ref name="hartwell 54" />

==== Europe ====
[[File:MandelsloJAC1228.JPG|left|thumb|[[Johan Albrecht de Mandelslo]] described the Japanese use of the Bessemer process.<ref name="wag">{{cite book |last=Wagner |first=Donald |url=https://books.google.com/books?id=FAud8CE5stsC&pg=PA363 |title=Science and Civilisation in China: Vol. 5, Part 11: Ferrous Metallurgy |publisher=Cambridge University Press |year=2008 |isbn=978-0-521-87566-0 |pages=363–5}}</ref>]]
In the 15th century, the [[Finery forge|finery process]], which shares the air-blowing principle with the Bessemer process, was developed in Europe.

High-quality steel was also made by the reverse process of adding carbon to carbon-free [[wrought iron]], usually imported from [[Sweden]]. The manufacturing process, called the [[cementation process]], consisted of heating bars of wrought iron together with [[charcoal]] for periods of up to a week in a long stone box. This produced [[blister steel]]. The blister steel was put in a crucible with wrought iron and melted, producing [[crucible steel]]. Up to 3 tons of (then expensive) [[Coke (fuel)|coke]] was burnt for each ton of steel produced. When rolled into bars such steel was sold at £50 to £60 (approximately £3,390 to £4,070 in 2008)<ref>{{Cite web |year=2009 |title=Purchasing Power of British Pounds from 1264 to Present |url=http://www.measuringworth.com/ppoweruk/ |access-date=14 January 2011}}</ref> a [[long ton]]. The most difficult and laborious part of the process was the production of wrought iron in [[Finery forge|finery forges]] in Sweden.

In 1740, [[Benjamin Huntsman]] developed the [[crucible technique]] for steel manufacture at his workshop in [[Handsworth, South Yorkshire|Handsworth]], [[England]]. This process greatly improved the quantity and quality of steel production. It added three hours firing time and required large quantities of coke. In making crucible steel, the blister steel bars were broken into pieces and melted in small crucibles, each containing 20&nbsp;kg or so. This produced higher quality metal, but increased the cost.

The Bessemer process reduced the time needed to make lower-grade steel to about half an hour while requiring only enough coke needed to melt the pig iron. The earliest Bessemer converters produced steel for £7 a [[long ton]], although it initially sold for around £40 a ton.

==== Japan ====
The Japanese may have made use of a Bessemer-type process, as observed by 17th century European travellers.<ref name="wag" /> Adventurer [[Johan Albrecht de Mandelslo]] described the process in a book published in English in 1669. He wrote, "They have, among others, particular invention for the melting of iron, without the using of fire, casting it into a tun done about on the inside without about half a foot of earth, where they keep it with continual blowing, take it out by ladles full, to give it what form they please." Wagner stated that Mandelslo did not visit Japan, so his description of the process is likely derived from other accounts. Wagner stated that the Japanese process may have been similar to the Bessemer process, but cautions that alternative explanations are plausible.<ref name="wag" />
[[File:Högbo_bruk_07.jpg|left|thumb|Bessemer converter at ''Högbo Bruk'', [[Sandviken]].]]
By the early 19th century the puddling process was widespread. At the time, process heat was too low to entirely remove [[slag]] impurities, but the [[reverberatory furnace]] made it possible to heat iron without placing it directly in the fire, offering some protection from impurities in the fuel source. [[Coal]] then began to replace [[charcoal]] as fuel. 

The Bessemer process allowed steel to be produced without fuel, using the iron's impurities to create the necessary heat. This drastically reduced costs, but [[Raw material|raw materials]] with the required characteristics were not always easy to find.<ref>{{Cite journal |last=Peter Temin |date=1963 |title=The Composition of Iron and Steel Products, 1869–1909 |journal=The Journal of Economic History |volume=23 |issue=4 |pages=447–471 |doi=10.1017/S0022050700109179 |jstor=2116209 |s2cid=154397900}}</ref>

=== Industrialization ===
Modern steelmaking began at the end of the 1850s when the [[Bessemer process]] became the first successful method of steelmaking in high quantity, followed by the [[open-hearth furnace]].

==Processes ==
[[File:Evolution convertisseurs.svg|lang=en|thumb|upright=1.2|Distribution of world steel production by methods]]
Modern steelmaking consists of three steps: primary, secondary, and tertiary.

Primary steelmaking involves melting iron into steel. Secondary steelmaking involves adding or removing other elements such as alloying agents and dissolved gases. Tertiary steelmaking casts molten metal into sheets, rolls or other forms. Multiple techniques are available for each step.<ref name="ghosh" />

===Primary steelmaking===

==== Basic oxygen ====
{{main|Basic oxygen steelmaking}}

Basic oxygen steelmaking (BOS) involves melting carbon-rich [[pig iron]] that has been developed by [[smelting]] iron ore in a [[blast furnace]], and converting it into steel. Blowing oxygen through molten pig iron oxidizes some of the carbon into [[Carbon monoxide|{{Chem|CO|-}}]] and [[Carbon dioxide|{{Chem|CO|2}}]], turning the iron into steel. [[refractory|Refractories]] (materials resistant to decomposition under high temperatures)—[[calcium oxide]] and [[magnesium oxide]]—line the smelting vessel to withstand the heat, corrosive molten metal, and [[slag]]. The chemistry is controlled to remove impurities such as silicon and phosphorus.

The basic oxygen process was developed in 1948 by [[Robert Durrer]], as a refinement of the [[Bessemer converter]] that replaced air with (more efficient) pure [[oxygen]]. It reduced plant capital costs and smelting time, and increased labor productivity. Between 1920 and 2000, labour requirements decreased by a factor of 1000, to 3 man-hours per thousand tonnes.{{Citation needed|date=November 2024}} In 2013, 70% of global steel output came from the basic oxygen furnace.<ref>{{Citation |title=Remaking the global steel industry |date=June 2013 |url=https://www2.deloitte.com/content/dam/Deloitte/global/Documents/Manufacturing/gx_remaking%20the%20global%20steel%20industry_06_13.pdf |publisher=Deloitte}}</ref> Furnaces can convert up to 350 tons of iron into steel in less than 40 minutes, compared to 10–12 hours in an [[open hearth furnace]].<ref name="fruehan">{{cite book |editor1-last=Fruehan |editor1-first=Richard J. |title=The Making, Shaping and Treating of Steel: Steelmaking and Refining Volume |edition=11th |date=1998 |location=[[Pittsburgh]] |publisher=[[Association for Iron and Steel Technology|AIST]] |url=https://www.asminternational.org/technical-books/-/journal_content/56/10192/05162G/PUBLICATION |lccn=98073477 |oclc=906879016 |isbn=978-0-930767-02-0}}</ref>

==== Electric arc ====
{{main|Electric arc furnace}}

Electric arc furnaces make steel from scrap or direct reduced iron. A "heat" (batch) of iron is loaded into the furnace, sometimes with a "hot heel" (molten steel from a previous heat). Gas burners may assist with the melt. As with BOS, fluxes are added to protect the vessel lining and aid the removal of impurities. The furnaces are typically 100 tonne-capacity that produce steel every 40 to 50 minutes.<ref name="fruehan" /> This process allows larger alloy additions than the basic oxygen method.<ref>{{Cite web|url=https://www.britannica.com/technology/steel/Electric-arc-steelmaking|title = Steel – Electric-arc steelmaking &#124; Britannica}}</ref>

==== HIsarna ====
{{main|HIsarna ironmaking process}}

In HIsarna ironmaking, iron ore is processed almost directly into liquid iron or [[Pig iron|hot metal]]. The process is based around a ''cyclone converter blast furnace'', which makes it possible to skip the intermediary production of pig iron pellets required for BOS. Skipping this preparatory step makes the HIsarna process more energy-efficient and reduces the {{chem|CO|2}} emissions by around 20%.<ref>{{Cite web |date=February 2022 |title=HISARNA: Building a sustainable steel industry |url=https://www.tatasteeleurope.com/sites/default/files/tata-steel-europe-factsheet-hisarna.pdf |access-date=November 14, 2022 |website=Tata Steel}}</ref>

==== Hydrogen reduction<span class="anchor" id="Hydrogen steel"></span> ====
Direct-reduced iron can be produced from iron ore as it reacts with atomic hydrogen. [[Renewable hydrogen]] allows steelmaking without [[fossil fuels]]. Direct reduction occurs at {{convert|1500|F}}. The iron is infused with carbon (from coal) in an electric arc furnace. Hydrogen [[electrolysis]] requires approximately 2600 [[Kilowatt-hour|kWh]] per ton of steel. Hydrogen production raises costs by an estimated 20–30% over conventional methods.<ref>{{cite web|author=<!--Not stated-->|date=2021-08-18|title=HYBRIT: The world's first fossil-free steel ready for delivery|url=https://group.vattenfall.com/uk/newsroom/pressreleases/2021/hybrit-the-worlds-first-fossil-free-steel-ready-for-delivery|access-date=2021-08-21|website=vattenfall.com|publisher=Vattenfall}}</ref><ref>{{cite journal|last1=Pei|first1=Martin|last2=Petäjäniemi|first2=Markus|date=2020-07-18|title=Toward a Fossil Free Future with HYBRIT: Development of Iron and Steelmaking Technology in Sweden and Finland|journal=Metals|volume=10|issue=7|pages=972|doi=10.3390/met10070972|doi-access=free}}</ref><ref>{{Cite magazine|last=Hutson|first=Matthew|date=2021-09-18|title=The Promise of Carbon-Neutral Steel|url=https://www.newyorker.com/news/annals-of-a-warming-planet/the-promise-of-carbon-neutral-steel|access-date=2021-09-20|magazine=The New Yorker|language=en-US}}</ref>

=== Secondary steelmaking ===
The next step commonly uses [[ladle (metallurgy)|ladles]]. Ladle operations include de-oxidation (or "killing"), vacuum degassing, alloy addition, inclusion removal, inclusion chemistry modification, de-sulphurisation, and homogenisation. It is common to perform ladle operations in gas-stirred ladles with electric arc heating in the furnace lid. Tight control of ladle metallurgy produces high grades of steel with narrow tolerances.<ref name="ghosh">{{cite book |last1=Ghosh |first1=Ahindra. |title=Secondary Steelmaking: Principles and Applications |date=December 13, 2000 |publisher=[[CRC Press]] |edition=1st |location=[[Boca Raton]], [[Florida|Fla.]] |url=https://www.crcpress.com/Secondary-Steelmaking-Principles-and-Applications/Ghosh/p/book/9780849302640 |oclc=664116613 |lccn=00060865 |isbn=9780849302640}}</ref>

=== Tertiary steelmaking ===
Tertiary steelmaking is a term given to a variety of processes used for shaping the liquid steel.

{{Expand section|date=December 2024}}

==Carbon dioxide emissions==
{{As of|2021}}, steelmaking was estimated to be responsible for around 11% of global {{chem|CO|2}} emissions and around 7% of greenhouse gas emissions.<ref>{{Cite web |last=Rossi |first=Marcello |date=2022-08-04 |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=2022-08-06 |website=Singularity Hub |language=en-US}}</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=2022-08-06 |website=Global Efficiency Intelligence |date=6 January 2021 |language=en-US}}</ref> Making 1 ton of steel emits about 1.8 tons of {{chem|CO|2}}.<ref>{{Cite web|url=https://www.iea.org/data-and-statistics/charts/direct-co2-intensity-of-the-iron-and-steel-sector-in-the-net-zero-scenario-2010-2030|title=Direct CO<sub>2</sub> intensity of the iron and steel sector in the Net Zero Scenario, 2010–2030 – Charts – Data & Statistics|website=IEA}}</ref> The bulk of these emissions are from the [[Industrial processes|industrial process]] in which coal provides the carbon that binds with the oxygen from the iron ore in a [[blast furnace]] in.<ref name="Formulae2">{{cite web|title=Blast Furnace|url=http://www.scienceaid.co.uk/chemistry/industrial/blastfurnace.html|url-status=dead|archive-url=https://web.archive.org/web/20071217143213/http://www.scienceaid.co.uk/chemistry/industrial/blastfurnace.html|archive-date=17 December 2007|access-date=2007-12-30|publisher=Science Aid}}</ref>

Additional {{chem|CO|2}} emissions result from mining, refining and shipping ore, [[basic oxygen steelmaking]], [[calcination]], and the [[hot blast]]. Proposed techniques  to reduce {{chem|CO|2}} emissions in the steel industry include reduction of iron ore using [[green hydrogen]] rather than carbon, and [[carbon capture and storage]].<ref name=":2">{{Cite journal |last1=De Ras |first1=Kevin |last2=Van De Vijver |first2=Ruben |last3=Galvita |first3=Vladimir V. |last4=Marin |first4=Guy B. |last5=Van Geem |first5=Kevin M. |date=2019-12-01 |title=Carbon capture and utilization in the steel industry: challenges and opportunities for chemical engineering |url=https://www.sciencedirect.com/science/article/abs/pii/S221133981930036X |journal=Current Opinion in Chemical Engineering |language=en |volume=26 |pages=81–87 |doi=10.1016/j.coche.2019.09.001 |issn=2211-3398 |s2cid=210619173|hdl=1854/LU-8635595 |hdl-access=free }}</ref>

===Mining and extraction===
Coal and iron ore mining are energy intensive, and damage their surroundings, leaving pollution, biodiversity loss, deforestation, and greenhouse gas emissions behind. 

===Blast furnace===
{{main|Blast furnace}}

Blast furnaces remove oxygen and trace elements from iron and add a tiny amount of carbon by melting the iron ore at {{Convert|1700|C|abbr=on}} in the presence of ambient oxygen and [[Coke (fuel)|coke]] (a type of coal). The oxygen from the ore is carried away by the carbon from the coke in the form of {{chem|CO|2}}. The reaction:

{{chem|Fe|2}}{{chem|O|3}}(s) + 3 CO(g) → 2 Fe(s) + 3 {{chem|CO|2}}(g)

The reaction occurs due to the lower (favorable) energy state of {{chem|CO|2}} compared to iron oxide, and the high temperatures are needed to achieve the reaction's [[activation energy]]. A small amount of carbon bonds with the iron, forming [[pig iron]], which is an intermediary before steel, as its carbon content is too high – around 4%.<ref name="msts">{{cite book|last=Camp|first=James McIntyre|url=https://archive.org/details/makingshapingan00frangoog|title=The Making, Shaping and Treating of Steel|author2=Francis, Charles Blaine|publisher=Carnegie Steel Co.|year=1920|edition=2nd|location=Pittsburgh|pages=[https://archive.org/details/makingshapingan00frangoog/page/n218 174]|oclc=2566055}}</ref>

===Decarburization===
{{main|Decarburization|Basic oxygen steelmaking}}

To reduce the carbon content in pig iron and obtain the desired carbon content of steel, it is re-melted and oxygen is blown through in [[basic oxygen steelmaking]]. In this step, the oxygen binds with the undesired carbon, carrying it away in the form of {{chem|CO|2}} gas, an additional emission source. After this step, the carbon content in the pig iron is lowered sufficiently to obtain steel.

===Calcination===
{{main|Calcination|Slag}}

Further {{chem|CO|2}} emissions result from the use of [[limestone]], which is melted at high temperatures in a reaction called [[calcination]], according to:

{{chem|CaCO|3}}(s) → CaO(s) + {{chem|CO|2}}(g)

The resulting {{chem|CO|2}} is an additional source of emissions. [[Calcium oxide]] (CaO, [[quicklime]]) can be used as a replacement to reduce emissions.<ref>{{Cite web
|title=Reactivity and overburning tendency of quicklime burnt at high temperature|url=https://www.cimprogetti.com/K_2019_EN_042.pdf|location=Italy|first1=G|last1=Vola|first2=L|last2=Sarandrea|first3=M|last3=Mazzieri|first4=P|last4=Bresciani|first5=M|last5=Ardit|first6=G|last6=Cruciani|year=2019}}</ref> It acts as a chemical [[Flux (metallurgy)|flux]], removing impurities (such as [[sulfur]] or [[phosphorus]] (e.g. [[apatite]] or [[fluorapatite]])<ref>{{Cite journal|last1=Pereira|first1=Antônio Clareti|last2=Papini|first2=Rísia Magriotis|date=September 2015|title=Processes for phosphorus removal from iron ore – a review|journal=Rem: Revista Escola de Minas|language=en|volume=68|issue=3|pages=331–335|doi=10.1590/0370-44672014680202|issn=0370-4467|doi-access=free}}</ref>) in the form of [[slag]] and lowers {{chem|CO|2}} emissions according to reactions such as:

SiO<sub>2</sub> + CaO → CaSiO<sub>3</sub>

This use of limestone to provide a flux occurs both in the blast furnace (to obtain pig iron) and in the [[Basic oxygen steelmaking|basic oxygen steel making]] (to obtain steel).

===Hot blast===
{{main|Hot blast}}

{{chem|CO|2}} emissions result from the [[hot blast]], which increases blast furnace temperatures. The hot blast pumps hot air into the blast furnace. The hot blast temperature ranges from {{convert|900|to|1300|C|F}} depending on the design and condition. Oil, [[tar]], natural gas, powdered coal and [[oxygen]] can be injected to combine with the coke to release additional energy and increase the percentage of reducing gases present, increasing productivity. Hot blast air is typically heated by burning fossil fuels, an additional emission source.<ref name="AISI">American Iron and Steel Institute (2005). [https://web.archive.org/web/20070510164459/http://www.steel.org/AM/Template.cfm?Section=Home&template=%2FCM%2FHTMLDisplay.cfm&ContentID=5433 How a Blast Furnace Works]. steel.org.</ref>

== Strategies for reducing carbon emissions ==<!---"Green steel" redirects here--->
The steel industry produces 7-8% of anthropogenic {{chem|CO|2}} emissions and is one of the most energy-intensive industries.<ref name=allen2023>{{cite web | last1=Allen | first1=Jessica | last2=Honeyands | first2=Tom | title='Green steel' is hailed as the next big thing in Australian industry. Here's what the hype is all about | website=[[The Conversation (website)|The Conversation]] | date=17 November 2023 | url=https://theconversation.com/green-steel-is-hailed-as-the-next-big-thing-in-australian-industry-heres-what-the-hype-is-all-about-160282 | access-date=23 April 2024}}</ref><ref>{{cite web  | title=Green steel: a material ready for industrial decarbonisation and widening the horizons of electrification | website=[[Iberdrola]] | date=22 April 2021 | url=https://www.iberdrola.com/sustainability/green-steel | access-date=23 April 2024}}</ref> Emissions abatement and decarbonization strategies vary by manufacturing process. Options fall into three general categories: using a non-fossil energy source; increasing processing efficiency; and evolving the manufacturing process. They may be used individually or in combination.{{citation needed|date=April 2024}}

"Green steel" describes steelmaking without [[fossil fuel]]s.<ref>{{cite web | title=What is green steel and how can it help us reach net zero? | website=World Economic Forum | date=11 July 2022 | url=https://www.weforum.org/agenda/2022/07/green-steel-emissions-net-zero/ | access-date=23 April 2024}}</ref> Some companies that claim to produce green steel reduce, but do not eliminate, emissions.<ref name= ssab>{{cite web | title=Not all green steel is fossil-free steel – here is why – Fossil free steel | website=SSAB | date=10 July 2023 | url=https://www.ssab.com/en/fossil-free-steel/insights/not-all-green-steel-is-fossil-free | access-date=23 April 2024}}</ref> 

=== Australia ===
Australia produces nearly 40% of the world's iron ore. The [[Australian Renewable Energy Agency]] (ARENA) is funding research projects involving direct reduced ironmaking (DRI) to reduce emissions. Companies such as [[Rio Tinto (corporation)|Rio Tinto]], [[BHP]], and [[BlueScope]] are developing green steel projects.<ref>{{cite web | title=Research centre lands $6.2 million for green iron and steel | website=[[InDaily]]| first= David| last=Simmons | date=22 April 2024 | url=https://www.indaily.com.au/business/companies/2024/04/22/lot-fourteen-based-research-centre-lands-6-million-for-green-iron-and-steel-research | access-date=23 April 2024}}</ref> 

The [[Whyalla Steelworks|Whyalla Hydrogen Project]], part of [[South Australia|South Australian]] Premier [[Malinauskas]]’ ''State Prosperity Project'', aims to produce [[Hydrogen economy|green steel]]. However, the project has been placed on hold due to financial and operational challenges of [[GFG Alliance]]. Both the federal and state governments have intervened in an effort to address these issues with the steelworks.<ref>{{Cite web |title=Industry backs Labor plans for 'pseudo-nationalisation' of Whyalla - ABC News |url=https://www.abc.net.au/news/2025-02-21/labor-whyalla-stake-steel-nationalisation/104962692 |access-date=2025-03-13 |website=amp.abc.net.au}}</ref>

=== Europe ===
European projects from HYBRIT, [[LKAB]], [[Voestalpine]], and [[ThyssenKrupp]] are pursuing strategies to reduce emissions.<ref name=":3" /> HYBRIT claims to produce green steel.<ref name="ssab" />

=== Top gas recovery in BF/BOF ===
Top gas from the blast furnace is normally expelled into the air. This gas contains {{chem|CO|2}}, H<sub>2</sub>, and CO. The top gas can be captured, the {{chem|CO|2}} removed, and the reducing agents reinjected into the blast furnace.{{citation needed|date=April 2024}} A 2012 study suggested that this process can reduce blast furnace {{chem|CO|2}} emissions by 75%,<ref>{{Cite book |last1=Afanga |first1=Khalid |last2=Mirgaux |first2=Olivier |last3=Patisson |first3=Fabrice |title=Carbon Management Technology Conference |date=2012-02-07 |chapter=Assessment of Top Gas Recycling Blast Furnace: A Technology To Reduce CO<sub>2</sub> Emissions in the Steelmaking Industry |chapter-url=https://onepetro.org/CMTCONF/proceedings/12CMTC/All-12CMTC/CMTC-151137-MS/589 |language=en |publisher=OnePetro |doi=10.7122/151137-MS}}</ref> while a 2017 study showed that emissions are reduced by 56.5% with carbon capture and storage, and reduced by 26.2% if only the recycling of the reducing agents is used.<ref>{{Cite journal |last1=Jin |first1=Peng |last2=Jiang |first2=Zeyi |last3=Bao |first3=Cheng |last4=Hao |first4=Shiyu |last5=Zhang |first5=Xinxin |date=2017-02-01 |title=The energy consumption and carbon emission of the integrated steel mill with oxygen blast furnace |url=https://www.sciencedirect.com/science/article/pii/S0921344915300410 |journal=Resources, Conservation and Recycling |series=Resource Efficiency in Chinese Industry |language=en |volume=117 |pages=58–65 |doi=10.1016/j.resconrec.2015.07.008 |issn=0921-3449|url-access=subscription }}</ref> To keep the carbon captured from entering the atmosphere, a method of storing it or using it would have to be found.

Another way to use the top gas is in a top recovery turbine which generates electricity, which thereby reduces external energy needs if electric arc smelting is used.<ref name=":3">{{Cite book |last=European Parliament. Directorate General for Parliamentary Research Services. |url=https://data.europa.eu/doi/10.2861/01969 |title=Carbon-free steel production: cost reduction options and usage of existing gas infrastructure. |date=2021 |publisher=Publications Office |location=LU|doi=10.2861/01969|isbn=978-92-846-7891-4 }}</ref> Carbon could also be captured from coke oven gases. {{as of|2022}}, separating the CO<sub>2</sub> from other gases and components in the system, and the high cost of the equipment and infrastructure changes needed, have prevented adoption, but the emission reduction potential has been estimated to be up to 65% to 80%.<ref>{{Cite web |title=CCS: a necessary technology for decarbonising the steel sector |url=https://www.globalccsinstitute.com/news-media/insights/ccs-a-necessary-technology-for-decarbonising-the-steel-sector/ |access-date=2022-11-14 |website=Global CCS Institute |language=en-AU}}</ref><ref name=":3" />

=== Hydrogen direct reduction ===
Hydrogen direct reduction (HDR) using hydrogen produced from emission-free power (green hydrogen) offers emission-free iron-making, because water is the only by-product of the reaction between [[iron oxide]] and hydrogen.<ref>{{cite web |title=The Potential of hydrogen in decarbonising steel production |url=https://www.europarl.europa.eu/RegData/etudes/BRIE/2020/641552/EPRS_BRI(2020)641552_EN.pdf |publisher=European parliament}}</ref> 

As of 2021, [[ArcelorMittal]], [[Voestalpine]], and [[Tata Steel|TATA]] had committed to using green hydrogen to smelt iron.<ref>{{cite web |last1=Zhou |first1=Tuyu |last2=Gosens |first2=Jorrit |last3=Xu |first3=Hongzhang |last4=Jotzo |first4=Frank |date=2 Aug 2022 |title=China's green steel plans: Near-term policy challenges & Australia-China links indecarbonisation |url=https://iceds.anu.edu.au/files/ANU%20policy%20brief%20-%20China%27s%20green%20steel%20plans_1.pdf |publisher=[[ANU]] [[Crawford School of Public Policy]], with National Foundation for Australia-China Relations |page=4–5}}</ref> In 2024 the HYBRIT project in Sweden was using HDR.<ref>{{cite web |date=31 August 2023 |title=Hybrit |url=https://www.hybritdevelopment.se/en/ |access-date=23 April 2024 |website=Home}}</ref> 

For the European Union, it is estimated that the hydrogen demand for HDR would require 180 GW of renewable capacity.<ref>{{Cite web |date=December 2023 |title=How To Decarbonize The Steel Sector|url=https://renewablereads.com/2023/11/16/how-to-decarbonize-the-steel-sector/ |access-date=December 13, 2023 |website=Renewable Reads}}</ref>

=== Iron ore electrolysis ===
Another developing possible technology is iron ore electrolysis, where the reducing agent is electrons.<ref name=":3" /> One method is molten oxide electrolysis. The cell consists of an inert anode, a liquid oxide electrolyte (CaO, MgO, etc.), and molten ore. When heated to ~1.600&nbsp;°C, the ore is reduced to iron and oxygen. As of 2022 [[Boston Metal]] was at the semi-industrial stage for this process, with plans to commercialize by 2026.<ref>{{Cite web |title=Transforming Metal Production |url=https://www.bostonmetal.com/transforming-metal-production/ |access-date=2022-11-14 |website=Boston Metal |language=en-US}}</ref><ref>{{cite news |url=https://www.bostonglobe.com/2023/01/26/business/boston-metal-gets-120-million-boost-make-green-steel/ |title=Boston Metal gets $120 million boost to make 'green steel' |author=Ed Davey |agency=The Associated Press |date=January 26, 2023}}</ref>

The Siderwin research project involved Arcelormittal was testing a different type of electrolysis.<ref>{{Cite web|title=Siderwin|url=https://www.siderwin-spire.eu/|access-date=2023-09-18}}</ref> It operates at around 110&nbsp;°C.<ref>{{cite news |last=Böck |first=Hanno |date=2023-03-24 |title=Making Steel with Electricity |url=https://industrydecarbonization.com/news/making-steel-with-electricity.html |work=Industry Decarbonization Newsletter |access-date=2023-09-18}}</ref>

=== Scrap-use in BF/BOF ===
[[Scrap]] steelmaking refers to steel that has either reached its end-of-life use, or is excess metal from the manufacture of steel components. Steel is easy to separate and recycle due to its magnetism. Using scrap avoids the emissions of 1.5 tons of {{chem|CO|2}} for every ton.<ref>{{Cite web |date=2021 |title=Fact sheet: Scrap use in the steel industry |url=https://www.saisi.org/wp-content/uploads/2021/06/Scrap-Fact-Sheet.pdf |access-date=November 14, 2022 |website=Wordsteel}}</ref> {{as of|2023}}, steel had one of the highest recycling rates of any material, with around 30% of the world's steel coming from recycled components. However, steel cannot be recycled endlessly,{{Clarify|reason=Because there are losses during use and also during recycling?|date=December 2024}} and the recycling processes, using arc furnaces, use electricity.<ref name=allen2023/>

=== H<sub>2</sub> enrichment in BF/BOF ===
In a blast furnace, iron oxides are reduced by a combination of CO, H<sub>2</sub>, and carbon. Only around 10% of the iron oxides are reduced by H<sub>2</sub>. With H<sub>2</sub> enrichment, the proportion of iron oxides reduced by H<sub>2</sub> is increased, consuming less carbon is consumed and emitting less {{chem|CO|2}}.<ref>{{Cite journal |last1=Lan |first1=Chenchen |last2=Hao |first2=Yuejun |last3=Shao |first3=Jiannan |last4=Zhang |first4=Shuhui |last5=Liu |first5=Ran |last6=Lyu |first6=Qing |date=November 2022 |title=Effect of H<sub>2</sub> on Blast Furnace Ironmaking: A Review |journal=Metals |language=en |volume=12 |issue=11 |pages=1864 |doi=10.3390/met12111864 |issn=2075-4701|doi-access=free }}</ref> This process can reduce emissions by an estimated 20%.{{citation needed|date=April 2024}}

=== Other strategies ===
One speculative idea is a project by SuSteel to develop a hydrogen plasma technology that reduces the ore with hydrogen at high operating temperatures.<ref name=":3" />

[[Biomass]] such as charcoal or wood pellets are a potential alternative blast furnace fuel, that does not involve fossil fuels, but still emits carbon. Emissions are reduced by 5% to 28%.<ref name=":3" />

=== China ===
German plantmaker SMS Group claims that Baosteel Desheng Stainless Steel Co., Ltd., a subsidiary of China Baowu Steel Group, has successfully completed the installation of a new vacuum oxygen decarburization (VOD) system at its Fuzhou plant with annual capacity of 417,000 metric tons of low carbon steel. Ultra-fine iron ore powder is injected into a superheated furnace using a specialized high-speed lance. The molten iron collects at the bottom of the furnace, creating a stream of high-purity iron.<ref>{{Cite web |date=2025-03-21 |title=China’s Revolutionary Coal-Free Steel Production: 3600 Times Faster and Transforming the Industry - LUX METAL |url=https://luxmetalgroup.com/chinas-revolutionary-coal-free-steel-production-3600-times-faster-and-transforming-the-industry/ |access-date=2025-05-13 |language=en-US}}</ref>

== See also ==
* [[Argon oxygen decarburization]]
* [[Basic oxygen steelmaking]]
* [[Blast furnace]] 
* [[Calcination]]
* [[Carbon additive]]
* [[Decarburization]]
* [[FINEX (steelmaking process)|FINEX]]
* [[Flodin process]]
* [[History of the steel industry (1850–1970)]]
* [[History of the steel industry (1970–present)]]
* [[Metallurgical coal]]
* [[Steel mill]]

==References==
{{reflist}}

==External links==
* {{Internet Archive short film|id=gov.archives.arc.12505|name=The Drama of Steel {{noitalic|(1946)}}}}
* [http://www.dlib.indiana.edu/collections/steel/ U.S. Steel Gary Works Photograph Collection, 1906–1971]
* [https://books.google.com/books?id=fScDAAAAMBAJ&pg=PA122 '"Steel for the Tools for Victory"], ''[[Popular Science]]'' (December 1943) large detailed article with numerous illustrations and cutaways on the modern basics of making steel

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

[[Category:Steelmaking| ]]
[[Category:Ancient Roman technology]]
[[Category:Chinese inventions]]
[[Category:English inventions]]
[[Category:Industrial Revolution in England]]