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Ferroalloy refers to various
alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductili ...
s of
iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...
with a high proportion of one or more other elements such as
manganese Manganese is a chemical element with the Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of ...
(Mn),
aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...
(Al), or
silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...
(Si). They are used in the production of
steel Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistan ...
s and alloys. The alloys impart distinctive qualities to steel and cast iron or serve important functions during production and are, therefore, closely associated with the iron and steel industry, the leading consumer of ferroalloys. The leading producers of ferroalloys in 2014 were
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
,
South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun ...
,
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
,
Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-ei ...
and
Kazakhstan Kazakhstan, officially the Republic of Kazakhstan, is a transcontinental country located mainly in Central Asia and partly in Eastern Europe. It borders Russia to the north and west, China to the east, Kyrgyzstan to the southeast, Uzbeki ...
, which accounted for 84% of the world production. World production of ferroalloys was estimated as 52.8 million tonnes in 2015.


Compounds

The main ferroalloys are: *FeAl – ferroaluminum *FeB – ferroboron – 12–20% of boron, max. 3% of
silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...
, max. 2%
aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...
, max. 1% of
carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon ma ...
*FeCe –
ferrocerium Ferrocerium (also known in Europe as Auermetall) is a synthetic pyrophoric alloy of mischmetal (cerium, lanthanum, neodymium, other trace lanthanides and some iron – about 95% lanthanides and 5% iron) hardened by blending in oxides ...
*FeCr – ferrochromium *FeMg – ferromagnesium *FeMn – ferromanganese *FeMo – ferromolybdenum – min. 60% Mo, max. 1% Si, max. 0.5% Cu *FeNb – ferroniobium *FeNi – ferronickel (and nickel pig iron) *FeP – ferrophosphorus *FeSi – ferrosilicon – 15–90% Si *FeSiMg – ferrosilicon magnesium (with Mg 4 to 25%), also called nodulizer *FeTa – ferrotantalum *FeTi – ferrotitanium – 10..30–65..75% Ti, max. 5–6.5% Al, max. 1–4% Si *FeU – ferrouranium *FeV – ferrovanadium *FeW – ferrotungsten


Production, by processes

upright=1.5, lang=en, Evolution of the global ferroalloys production, by processes. Ferroalloys are produced generally by two methods : in a blast furnace or in an electric arc furnace. Blast furnace production continuously decreased during the 20th century, whereas the electric arc production is still increasing. Today, ferromanganese can be still efficiently produced in a blast furnace, but, even in this case, electric arc furnace are spreading. More commonly, ferroalloys are produced by carbothermic reactions, involving reduction of oxides with carbon (as coke) in the presence of iron. Some ferroalloys are produced by the addition of elements into molten iron. It is also possible to produce somme ferroalloys by processes. For example, the is used in
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...
to produce ferronickel.


Production and consumption, by ferroalloys


Ferrochromium

The leading world chromite ore-producing countries in 2014 were South Africa (12 Mt), Kazakhstan (3.7 Mt), India (3.5 Mt), and Turkey (2.6 Mt). Most of the chromite ore production was smelted in electric-arc furnaces to produce ferrochromium for the metallurgical industry. The leading world ferrochromium-producing countries in 2014 were China (4.5 Mt), South Africa (3.6 Mt), Kazakhstan (1.2 Mt) and India (0.9 Mt). Most of the 11.7 Mt of ferrochromium produced worldwide was consumed in the manufacture of stainless steel which totalled 41.7 Mt in 2014.


Ferromanganese

Two manganese ferroalloys, ferromanganese and silicomanganese, are key ingredients for steelmaking. China is the leading world producer of manganese ferroalloys (2.7 Mt), with output much larger than the combined output of the next three biggest producers—Brazil (0.34 Mt), South Africa (0.61 Mt) and Ukraine (0.38 Mt).


Ferromolybdenum

Major producers of ferromolybdenum are Chile (16,918 t), China (40,000 t) and the United States (which, in 2008, accounted for 78% of world molybdenite ore production. Canada, Mexico and Peru accounted for the remainder. Molybdenite concentrates are roasted to form molybdic oxide, which can be converted into ferromolybdenum, molybdenum chemicals, or molybdenum metal. Although the United States was the second leading molybdenum-producing country in the world in 2008, it imported more than 70% of its ferromolybdenum requirements in 2008, mostly for the steel industry (83% of ferromolybdenum consumed).


Ferronickel

In 2014, about 33% of the world’s annual new
nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow t ...
was ferronickel, an extensive review article of which was published by Swartzendruber et al in 1991. Many of the meteorites that fall to Earth turn out to be ferronickel, and take the form of kamacite and/or
taenite Taenite is a mineral found naturally on Earth mostly in iron meteorites. It is an alloy of iron and nickel, with a chemical formula of and nickel proportions of 20% up to 65%. The name is derived from the Greek ταινία for "band, ribbon" ...
. Ferronickel has a face-centred cubic crystal structure (via Ni). It can take the form of ferrite,
martensite Martensite is a very hard form of steel crystalline structure. It is named after German metallurgist Adolf Martens. By analogy the term can also refer to any crystal structure that is formed by diffusionless transformation. Properties M ...
, or
austenite Austenite, also known as gamma-phase iron (γ-Fe), is a metallic, non-magnetic allotrope of iron or a solid solution of iron with an alloying element. In plain-carbon steel, austenite exists above the critical eutectoid temperature of 100 ...
. The binary Fe-Ni system has been investigated for analogic purposes to steel because the presence of nickel in high-alloy steels such as austenitic stainless steels and maraging steels is a key driver for the transition from body-centered cubic ferrite to face-centered cubic austenite. In the late 20th century, 60% of nickel production was based on the matte smelting of sulfide ores, this did not lend itself to ferronickel production. According to 2003 data, the share of laterites in primary nickel production was reported to be 42%. World annual production of ferronickel in 2014 was around 250,000 tonnes. The two largest producers were BHP and Société Le Nickel.
Laterite Laterite is both a soil and a rock type rich in iron and aluminium and is commonly considered to have formed in hot and wet tropical areas. Nearly all laterites are of rusty-red coloration, because of high iron oxide content. They develop by ...
ores are often used to supply the production process. The RKEF process is often used."Production of FeNi from high iron nickel ores" Svana, Erik and Ysteb, Roald (1983) Production of FeNi from high iron nickel ores. In: Proceedings of the Seminar on Problems and Prospects of Ferro-Alloy Industry in India, Oct. 24–26, 1983, NML, Jamshedpur. The energy consumption per tonne of product is high for laterite ores because of the low-grade feed, and hence produces a lot of waste slag and gaseous pollution. Generally, over 90% of the furnace output is in the form of slag. The technique of refining molten ferronickel is a topic for specialists, and because of ore content variability the processes might even need to be tailored by source: for example the Larco process of Greek ores.Zevgolis, Emmanouil. (2004)
The evolution of the Greek ferronickel production process
International Laterite Nickel Symposium. 619–632.
"The main reason for adding nickel in ferrous alloys is to promote an austenitic microstructure. Nickel generally increases ductility, toughness and corrosion resistance." Nickel pig iron is distinguished from ferronickel by the former's low weight fraction (4–10%) of nickel and high carbon content (>3%). In contrast, ferronickel is a relatively pure binary alloy. In 2008, the major ferronickel-producing countries were Japan (301,000 t), New Caledonia (144,000 t) and Colombia (105,000 t). Together, these three countries accounted for about 51% of world production if China is excluded. Ukraine, Indonesia, Greece, and Macedonia, in descending order of gross weight output, all produced between 68,000 t and 90,000 t of ferronickel, accounting for an additional 31%, excluding China. China was excluded from statistics because its industry produced large tonnages of nickel pig iron in addition to a spectrum of conventional ferronickel grades, for an estimated combined output of 590,000 t gross weight. The nickel content of individual Chinese products varied from about 1.6% to as much as 80%, depending upon customer end use. In the United States, the steel industry accounted for virtually all the ferronickel consumed in 2008, with more than 98% used in stainless and heat-resistant steels; no ferronickel was produced in the US in 2008. The nickel pig iron is a low grade ferronickel made in China, which is very popular since the 2010s.


Ferrosilicon

Silicon ferroalloy consumption is driven by
cast iron Cast iron is a class of iron– carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its color when fractured: white cast iron has carbide impuri ...
and steel production, where silicon alloys are used as deoxidizers. Some silicon metal was also used as an alloying agent with iron. On the basis of silicon content, net production of ferrosilicon and miscellaneous silicon alloys in the US was 148,000 t in 2008. China is the major supplier, which in 2008 produced more ferrosilicon (4.9 Mt) than the rest of the world combined. Other major manufacturers are Norway (0.21 Mt), Russia (0.85 Mt) and US (0.23 Mt).


Ferrotitanium

Titanium is used in steelmaking for deoxidation, grain-size control, and carbon and nitrogen control and stabilization. During steelmaking, titanium is usually introduced as ferrotitanium because of its relatively low melting temperature and high density. Steels with relatively high titanium content include interstitial-free, stainless and high-strength low-alloy steels. Ferrotitanium is usually produced by induction melting of titanium scrap with iron or steel; however, it also is produced directly from titanium mineral concentrates. The standard grades of ferrotitanium are 30% and 70% titanium. Ferrosilicon-titanium also is produced to allow the simultaneous addition of silicon and titanium. The leading ferrotitanium producing countries include Brazil, China, India, Japan, Russia, Ukraine, United Kingdom and the United States.


Ferrotantalum

Ferrotantalum is added to molten steel to create hardenable specialty steels. It is also used as welding material, spraying powder, and for powder metallurgy applications.


Ferrotungsten

Tungsten is an important alloying element in high-speed and other tool steels, and is used to a lesser extent in some stainless and structural steels. Tungsten is often added to steel melts as ferrotungsten, which can contain up to 80% tungsten. World ferrotungsten production is dominated by China, which in 2008 exported 4,835 t (gross weight) of the alloy. Ferrotungsten is relatively expensive, with the prices around $31–44 per kilogram of contained tungsten.


Ferrovanadium

In 2008, China, Russia (12,000 t) and South Africa (17,000 t) accounted for 98% of world vanadium mine production. In these three countries, vanadium was primarily recovered from titanium-bearing magnetite ore processed to produce pig iron. The process entails aluminothermic reduction of
vanadium(V) oxide Vanadium(V) oxide (''vanadia'') is the inorganic compound with the formula V2 O5. Commonly known as vanadium pentoxide, it is a brown/yellow solid, although when freshly precipitated from aqueous solution, its colour is deep orange. Because ...
, aluminium (as oxide getter), and scrap iron. This produces a slag containing 20% to 24% vanadium pentoxide, which can be further processed to ferrovanadium containing 40% to 50% vanadium. Of the 5,090 t of vanadium consumed in the United States in 2008, 84% came from ferrovanadium and nearly all of it (99%) went into steel manufacturing.


References

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