Cementite

Iron carbide

Iron carbide plates
Orthorhombic Fe3C. Iron atoms are blue
Names
IUPAC name
Iron carbide
Other names
Cementite
Identifiers
3D model (JSmol)
ECHA InfoCard 100.031.411 Edit this at Wikidata
EC Number
  • 234-566-7
  • InChI=1S/C.3Fe
    Key: TXAHJXBWFZQNQY-UHFFFAOYSA-N
  • [Fe]=[C]=[Fe].[Fe]
Properties
Fe3C
Molar mass 179.546 g/mol
Appearance dark gray or black crystals, odorless
Density 7.694 g/cm3, solid[1]
Melting point 1,227 °C (2,241 °F; 1,500 K)[1]
insoluble
Structure[2]
Orthorhombic, oP16
Pnma, No. 62
a = 0.509 nm, b = 0.6478 nm, c = 0.4523 nm
4
Thermochemistry[3]
105.9 J·mol−1·K−1
104.6 J·mol−1·K−1
25.1 kJ·mol−1
20.1 kJ·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Cementite (or iron carbide) is a compound of iron and carbon, more precisely an intermediate transition metal carbide with the formula Fe3C. By weight, it is 6.67% carbon and 93.3% iron. It has an orthorhombic crystal structure.[4] It is a hard, brittle material,[4] normally classified as a ceramic in its pure form, and is a frequently found and important constituent in ferrous metallurgy. While cementite is present in most steels[5] and cast irons, it is produced as a raw material in the iron carbide process, which belongs to the family of alternative ironmaking technologies. The name cementite originated from the theory of Floris Osmond and J. Werth, in which the structure of solidified steel consists of a kind of cellular tissue, with ferrite as the nucleus and Fe3C the envelope of the cells. The carbide therefore cemented the iron.

  1. ^ a b Haynes, p. 4.67
  2. ^ Herbstein, F. H.; Smuts, J. (1964). "Comparison of X-ray and neutron-diffraction refinements of the structure of cementite Fe3C". Acta Crystallographica. 17 (10): 1331–1332. Bibcode:1964AcCry..17.1331H. doi:10.1107/S0365110X64003346.
  3. ^ Haynes, p. 5.23
  4. ^ a b Smith & Hashemi 2006, p. 363
  5. ^ Verhoeven, John D. (2007). Steel Metallurgy for the Non-Metallurgist. ASM International. p. 35. ISBN 978-1-61503-056-9.