Steel is an alloy of iron and carbon, and sometimes other elements. Because of its high tensile strength and low cost, it is a major component used in buildings, infrastructure, tools, ships, automobiles, machines, appliances, and weapons.

Iron is the base metal of steel. Iron is able to take on two crystalline forms (allotropic forms), body centered cubic and face centered cubic, depending on its temperature. In the body-centered cubic arrangement, there is an iron atom in the center and eight atoms at the vertices of each cubic unit cell; in the face-centered cubic, there is one atom at the center of each of the six faces of the cubic unit cell and eight atoms at its vertices. It is the interaction of the allotropes of iron with the alloying elements, primarily carbon, that gives steel and cast iron their range of unique properties.

In pure iron, the crystal structure has relatively little resistance to the iron atoms slipping past one another, and so pure iron is quite ductile, or soft and easily formed. In steel, small amounts of carbon, other elements, and inclusions within the iron act as hardening agents that prevent the movement of dislocations that are common in the crystal lattices of iron atoms.

The carbon in typical steel alloys may contribute up to 2.14% of its weight. Varying the amount of carbon and many other alloying elements, as well as controlling their chemical and physical makeup in the final steel (either as solute elements, or as precipitated phases), slows the movement of those dislocations that make pure iron ductile, and thus controls and enhances its qualities. These qualities include such things as the hardness, quenching behavior, need for annealing, tempering behavior, yield strength, and tensile strength of the resulting steel. The increase in steel's strength compared to pure iron is possible only by reducing iron's ductility.

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 production of blister steel and then crucible steel. With the invention of the Bessemer process in the mid-19th century, a new era of mass-produced steel began. This was followed by the Siemens–Martin process and then the Gilchrist–Thomas process that refined the quality of steel. With their introductions, mild steel replaced wrought iron.

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, steel is one of the most common manmade materials in the world, with more than 1.6 billion tons produced annually. Modern steel is generally identified by various grades defined by assorted standards organizations.

Definitions and related materials

The noun steel originates from the Proto-Germanic adjective stahliją or stakhlijan (made of steel), which is related to stahlaz or stahliją (standing firm).[1]

The carbon content of steel is between 0.002% and 2.14% by weight for plain ironcarbon alloys.[2] These values vary depending on alloying elements such as manganese, chromium, nickel, tungsten, and so on. Basically, steel is an iron-carbon alloy that does not undergo eutectic reaction. In contrast, cast iron does undergo eutectic reaction. Too little carbon content leaves (pure) iron quite soft, ductile, and weak. Carbon contents higher than those of steel make a brittle alloy commonly called pig iron. While iron alloyed with carbon is called carbon steel, 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.[3] Additional elements, most frequently considered undesirable, are also important in steel: phosphorus, sulfur, silicon, and traces of oxygen, nitrogen, and copper.

Plain carbon-iron 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.[3] 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.

Other Languages
Afrikaans: Staal
Alemannisch: Stahl
العربية: صلب (سبيكة)
aragonés: Acero
armãneashti: Cilechi
asturianu: Aceru
Avañe'ẽ: Kuarepotijy
azərbaycanca: Polad
বাংলা: ইস্পাত
Bahasa Banjar: Waja
Bân-lâm-gú: Kǹg-thih
башҡортса: Ҡорос
беларуская: Сталь
беларуская (тарашкевіца)‎: Сталь
български: Стомана
bosanski: Čelik
brezhoneg: Dir
буряад: Ган булад
català: Acer
čeština: Ocel
Cymraeg: Dur
dansk: Stål
Deutsch: Stahl
dolnoserbski: Stal
eesti: Teras
Ελληνικά: Χάλυβας
español: Acero
Esperanto: Ŝtalo
euskara: Altzairu
فارسی: فولاد
Fiji Hindi: Steel
français: Acier
furlan: Açâr
Gàidhlig: Stàilinn
galego: Aceiro
한국어: 강철
հայերեն: Պողպատ
हिन्दी: इस्पात
hornjoserbsce: Wocl
hrvatski: Čelik
Ido: Stalo
Bahasa Indonesia: Baja
interlingua: Aciero
Ирон: Æндон
íslenska: Stál
italiano: Acciaio
עברית: פלדה
Basa Jawa: Waja
Kabɩyɛ: Asiyee
ಕನ್ನಡ: ಉಕ್ಕು
ქართული: ფოლადი
қазақша: Болат
Kiswahili: Chuma cha pua
Kreyòl ayisyen: Asye
Кыргызча: Болот
лакку: Чаннан
Latina: Chalybs
latviešu: Tērauds
Lëtzebuergesch: Stol
lietuvių: Plienas
Limburgs: Staol
la .lojban.: gasta
lumbaart: Azal
magyar: Acél
македонски: Челик
മലയാളം: ഉരുക്ക്
मराठी: पोलाद
მარგალური: ბულათი
Bahasa Melayu: Keluli
Mirandés: Aço
монгол: Ган
မြန်မာဘာသာ: သံမဏိ
Nederlands: Staal (legering)
Nedersaksies: Stoal
नेपाली: लोहा
नेपाल भाषा: स्टील
Napulitano: Acciare
norsk: Stål
norsk nynorsk: Stål
occitan: Acièr
oʻzbekcha/ўзбекча: Poʻlat
ਪੰਜਾਬੀ: ਫੌਲਾਦ
پنجابی: فولاد
Patois: Stiil
Piemontèis: Assel
polski: Stal
português: Aço
română: Oțel
Runa Simi: Asiru
русский: Сталь
саха тыла: Ыстаал
Scots: Steel
sicilianu: Azzaru
Simple English: Steel
slovenčina: Oceľ
slovenščina: Jeklo
کوردی: پۆڵا
српски / srpski: Челик
srpskohrvatski / српскохрватски: Čelik
suomi: Teräs
svenska: Stål
Tagalog: Asero
தமிழ்: எஃகு
татарча/tatarça: Корыч
తెలుగు: ఉక్కు
Türkçe: Çelik
українська: Сталь
اردو: فولاد
ئۇيغۇرچە / Uyghurche: پولات
vèneto: Açal
Tiếng Việt: Thép
Võro: Teräs
West-Vlams: Stoal
Winaray: Asero
ייִדיש: שטאל
Yorùbá: Irin
žemaitėška: Plėins