Ferroaluminum

Ferroaluminum (FeAl) is a ferroalloy, consisting of iron and aluminium. The metal usually consists of 40% to 60% aluminium and applications of ferroaluminum include the deoxidation of steel,[1] hardfacing applications, reducing agent, thermite reactions, AlNiCo magnets, and alloying additions to welding wires and fluxes.[2] The alloy is also known for the ability to manufacture low melting point alloys and its ability to carry out aluminothermic welding. Ferroaluminum does not currently have a CAS Registry Number. The presence of iron in aluminum helps in the decrease of casting defects. improves tensile, yield, hardness, and maintains strength at high temperatures.[3] The first recorded usage of the word "ferroaluminum" was in 1887.[4][5] Ferroaluminum is also used in the process of nitriding, which is a heat treating process that diffuses nitrogen into the surface of a metal to create a case-hardened surface. The aluminum provided in the alloy helps with this process.[6][7][8] The majority of the world's ferroaluminum is produced by Australia, China, Russia, the US and Canada, with the cost of electricity being the main factor in the aluminium obtaining process.[9][10]

For the iron-aluminium intermetallic alloy/compound, see Iron aluminide.

Manufacturing process

Ferroaluminum is manufactured in an electricity-intensive process that involves three steps. First, aluminium oxide (Al2O3) is obtained through the Bayer process by digestion of bauxite with sodium hydroxide (NaOH) at about 240 °C. Second, the aluminium oxide is subjected to a Hall electrolytic process together with cryolite to obtain aluminium that will then be combined with iron to create the ferroaluminum. Last, after the solidification of the metal, milling and sieving processes are carried out, which obtains the suitable particle size for its applications.[9]

Chemical composition
Chemical Composition of Ferroaluminum[1]
Element Content
Silicon, Si maximum of 2%
Aluminum, Al 40% to 60%
Carbon, C maximum of 0.50%
Sulfur, S maximum of 0.10%
Phosphorus, P maximum of 0.10%
Iron, Fe main constituent

Physical properties
Physical Properties of Ferroaluminum[1]
Properties Metric Imperial
Melting Point 1160 °C at 60% Al

1250 °C at 40% Al

 2120 °F at 60% Al

2282 °F at 40% Al

References
  1. "Ferro Aluminium". Miller and Co. Retrieved October 20, 2018.
  2. "Ferro Aluminum (FeAl) Powder". Reade Advanced Materials. Retrieved October 20, 2018.
  3. "30% Ferro Aluminum". Belmont. Retrieved October 20, 2018.
  4. "ferroaluminum". Dictionary.com. Retrieved October 20, 2018.
  5. "ferroaluminum". Merriam-Webster Dictionary. Retrieved October 20, 2018.
  6. Meka, S.R.; Chauhan, A.; Steiner, T.; Bischoff, E.; Ghosh, P.K.; Mittemeijer, E.J. (2015). "Generating duplex microstructures by nitriding; nitriding of iron based Fe–Mn alloy". Materials Science and Technology: 1743284715Y.000. doi:10.1179/1743284715Y.0000000098.
  7. "Ferro Aluminum". Aria Ferroalloy Co. Retrieved October 20, 2018.
  8. De Vries, Ralph P.; De Fries, Henry A. (June 25, 1929). "Patent US1718685A - Ferro-aluminum alloy and method of making it". Google Patents. Retrieved October 20, 2018.
  9. "Ferro Aluminium Description and Uses". Cometal. Retrieved October 20, 2018.
  10. "Ferro Aluminium". Westbrook Resources. Retrieved October 20, 2018.
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