Steelmaking is the second step in producing
steelSteel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
from
iron ore. In this stage, impurities such as
sulfurSulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
,
phosphorusPhosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
, and excess
carbonCarbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
are removed from the
raw ironPig iron is the intermediate product of smelting iron ore with a high-carbon fuel such as coke, usually with limestone as a flux. Charcoal and anthracite have also been used as fuel...
, and alloying elements such as
manganeseManganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
,
nickelNickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
,
chromiumChromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...
and
vanadiumVanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...
are added to produce the exact steel required.
Older processes
The earliest means of producing steel was in a
bloomeryA bloomery is a type of furnace once widely used for smelting iron from its oxides. The bloomery was the earliest form of smelter capable of smelting iron. A bloomery's product is a porous mass of iron and slag called a bloom. This mix of slag and iron in the bloom is termed sponge iron, which...
. Early modern methods of producing steel were often labour-intensive and highly skilled arts. See:
- finery forge
Iron tapped from the blast furnace is pig iron, and contains significant amounts of carbon and silicon. To produce malleable wrought iron, it needs to undergo a further process. In the early modern period, this was carried out in a finery forge....
, in which the German finery processThe following list is composed of items, techniques and processes that were invented by or discovered by people from Germany or German-speaking Europe.-Anatomy:* Ampulla of Vater * Auerbach's plexus * Brodmann's areas * Canals of Hering...
could be managed to produce steel.
- blister steel and crucible steel
Crucible steel describes a number of different techniques for making steel in a crucible. Its manufacture is essentially a refining process which is dependent on preexisting furnace products...
.
An important aspect of the
industrial revolutionThe Industrial Revolution was a period from the 18th to the 19th century where major changes in agriculture, manufacturing, mining, transportation, and technology had a profound effect on the social, economic and cultural conditions of the times...
was the development of large-scale methods of producing forgeable metal (bar iron or steel). The puddling furnace was initially a means of producing
wrought ironthumb|The [[Eiffel tower]] is constructed from [[puddle iron]], a form of wrought ironWrought iron is an iron alloy with a very low carbon...
, but was later applied to steel production.
The real revolution in steelmaking only began at the end of the 1850s. The
Bessemer processThe Bessemer process was the first inexpensive industrial process for the mass-production of steel from molten pig iron. The process is named after its inventor, Henry Bessemer, who took out a patent on the process in 1855. The process was independently discovered in 1851 by William Kelly...
was the first successful method of steelmaking in quantity, followed by the
open hearth furnaceOpen hearth furnaces are one of a number of kinds of furnace where excess carbon and other impurities are burnt out of the pig iron to produce steel. Since steel is difficult to manufacture due to its high melting point, normal fuels and furnaces were insufficient and the open hearth furnace was...
.
Modern processes
Modern steelmaking processes are broken into two categories: primary and secondary steelmaking. Primary steelmaking uses mostly new iron as the feedstock, usually from a
blast furnaceA blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally iron.In a blast furnace, fuel and ore and flux are continuously supplied through the top of the furnace, while air is blown into the bottom of the chamber, so that the chemical reactions...
. Secondary steelmaking uses scrap steel as the primary raw material. Gases created during the production of steel can be used as a source of power.
Primary steelmaking
Basic oxygen steelmaking is a method of primary steelmaking in which carbon-rich molten
pig ironPig iron is the intermediate product of smelting iron ore with a high-carbon fuel such as coke, usually with limestone as a flux. Charcoal and anthracite have also been used as fuel...
is made into steel. Blowing oxygen through molten pig iron lowers the carbon content of the
alloyAn alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...
and changes it into low-carbon steel. The process is known as
basic due to the
pHIn chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
of the
refractoriesA refractory material is one that retains its strength at high temperatures. ASTM C71 defines refractories as "non-metallic materials having those chemical and physical properties that make them applicable for structures, or as components of systems, that are exposed to environments above...
—
calcium oxideCalcium oxide , commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline crystalline solid at room temperature....
and
magnesium oxideMagnesium oxide , or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium . It has an empirical formula of and consists of a lattice of Mg2+ ions and O2– ions held together by ionic bonds...
—that line the vessel to withstand the high temperature of molten metal.
The process was developed in 1948 by
Robert DurrerRobert Durrer was a Swiss engineer who developed the basic oxygen steelmaking process...
and commercialized in 1952–1953 by Austrian
VOEST and ÖAMGVoestalpine AG is an international steel company based in Linz, Austria. The company is active in steel, automotive, railway systems, profilform and tool steel industries....
. The LD converter, named after the
AustriaAustria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...
n towns
LinzLinz is the third-largest city of Austria and capital of the state of Upper Austria . It is located in the north centre of Austria, approximately south of the Czech border, on both sides of the river Danube. The population of the city is , and that of the Greater Linz conurbation is about...
and Donawitz (a district of
LeobenLeoben is a Styrian city in central Austria, located by the Mur river. With a population of about 25,000 it is a local industrial center and hosts the University of Leoben which specialises in mining...
) is a refined version of the Bessemer converter where blowing of air is replaced with blowing
oxygenOxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
. It reduced capital cost of the plants, time of smelting, and increased labor productivity. Between 1920 and 2000, labor requirements in the industry decreased by a factor of 1,000, from more than 3 worker-hours per tonne to just 0.003. The vast majority of steel manufactured in the world is produced using the basic oxygen furnace; in 2000, it accounted for 60% of global steel output. Modern furnaces will take a charge of iron of up to 350 tons and convert it into steel in less than 40 minutes, compared to 10–12 hours in an
open hearth furnaceOpen hearth furnaces are one of a number of kinds of furnace where excess carbon and other impurities are burnt out of the pig iron to produce steel. Since steel is difficult to manufacture due to its high melting point, normal fuels and furnaces were insufficient and the open hearth furnace was...
.
Secondary steelmaking
Secondary steelmaking is most commonly performed in an electric arc furnace.
HIsarna steelmaking
The HIsarna steelmaking process is a process for primary steelmaking in which iron ore is processed almost directly into steel. The process is based around a new type of blast furnace called a
Cyclone Converter Furnace, which makes it possible to skip the process of manufacturing pig iron pellets that is necessary for the
basic oxygen steelmakingBasic oxygen steelmaking , also known as Linz-Donawitz-Verfahren steelmaking or the oxygen converter process is a method of primary steelmaking in which carbon-rich molten pig iron is made into steel. Blowing oxygen through molten pig iron lowers the carbon content of the alloy and changes it into...
process. Without the necessity for this preparatory step the HIsarna process is more energy-efficient and has a lower
carbon footprintA carbon footprint has historically been defined as "the total set of greenhouse gas emissions caused by an organization, event, product or person.". However, calculating a carbon footprint which conforms to this definition is often impracticable due to the large amount of data required, which is...
than traditional steelmaking processes.
See also
- Argon oxygen decarburization
Argon oxygen decarburization is a process primarily used in stainless steel making and other high grade alloys with oxidizable elements such as chromium and aluminum. After initial melting the metal is then transferred to an AOD vessel where it will be subjected to three steps of refining;...
- Decarburization
Decarburization is the process opposite to carburization, namely aimed at decreasing the content of carbon in metals . Decarburization occurs when Carbon in the metal reacts with gasses present in the atmosphere...
- FINEX
In finance, the term "Finex" is an acronym for "financial exchange."In the technology world, the term FINEX is the name for an innovative iron making technology developed by Siemens VAI and POSCO...
- Flodin process
Flodin process is a process for manufacturing steel developed by Henning Flodin from Sweden.Using a specially constructed electrical furnace a mixture of hematite and coal are smelted in a continuous process, with the reduced metal accumulating at the bottom of the furnace, where it can be tapped...
- Steel mill
A steel mill or steelworks is an industrial plant for the manufacture of steel.Steel is an alloy of iron and carbon. It is produced in a two-stage process. First, iron ore is reduced or smelted with coke and limestone in a blast furnace, producing molten iron which is either cast into pig iron or...
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