Ferroalloy refers to various alloys of iron with a high proportion of one or more other elements such as manganese (Mn), aluminium (Al), or silicon (Si).[1] They are used in the production of steels and alloys.[2][3] 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, South Africa, India, Russia and Kazakhstan, which accounted for 84% of the world production.[4] World production of ferroalloys was estimated as 52.8 million tonnes in 2015.[5]
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Ferroalloy Meaning
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Transcription
Compounds
The main ferroalloys are:
- FeAl – ferroaluminum
- FeB – ferroboron – 12–20% of boron, max. 3% of silicon, max. 2% aluminium, max. 1% of carbon
- FeCe – ferrocerium
- 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
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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 some ferroalloys by direct reduction processes. For example, the Krupp-Renn Process is used in Japan to produce ferronickel.[6]
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.[4]
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).[2]
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).[2]
Ferronickel
Density | 3.8 g/cm3 |
Melting point | 1500°C |
Boiling point | 2900°C |
In 2014, about 33% of the world’s annual new nickel was ferronickel,[8] an extensive review article of which was published by Swartzendruber et al in 1991.[9] Many of the meteorites that fall to Earth turn out to be ferronickel,[9] and take the form of kamacite and/or taenite.[citation needed] Ferronickel has a face-centred cubic crystal structure (via Ni).[10] It can take the form of ferrite, martensite, or austenite. 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.[11]
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.[12] According to 2003 data, the share of laterites in primary nickel production was reported to be 42%.[12] World annual production of ferronickel in 2014 was around 250,000 tonnes.[8] The two largest producers were BHP and Société Le Nickel.[8] Laterite ores are often used to supply the production process.[13][14] The RKEF process is often used.[15] 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.[16] Generally, over 90% of the furnace output is in the form of slag.[8] The technique of refining molten ferronickel is a topic for specialists,[17] and because of ore content variability the processes might even need to be tailored by source: for example the Larco process of Greek ores.[18] "The main reason for adding nickel in ferrous alloys is to promote an austenitic microstructure. Nickel generally increases ductility, toughness and corrosion resistance."[19] 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.[19]
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.[2]
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.[2]
The nickel pig iron is a low grade ferronickel made in China, which is very popular since the 2010s.