In iron and steel metallurgy, ledeburite is a mixture of 4.3% carbon in iron and is a eutectic mixture of

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 1000 K ...

and

cementite 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. It is a hard, bri ...

. Ledeburite is not a type of steel as the carbon level is too high although it may occur as a separate constituent in some high carbon steels. It is mostly found with cementite or

pearlite Pearlite is a two-phased, lamellar (or layered) structure composed of alternating layers of ferrite (87.5 wt%) and cementite (12.5 wt%) that occurs in some steels and cast irons. During slow cooling of an iron-carbon alloy, pearlite form ...

in a range of cast irons. It is named after the

metallurgist Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are known as alloys. Metallurgy encompasses both the sc ...

Karl Heinrich Adolf Ledebur (1837–1906). He was the first

professor Professor (commonly abbreviated as Prof.) is an academic rank at universities and other post-secondary education and research institutions in most countries. Literally, ''professor'' derives from Latin as a "person who professes". Professors ...

of metallurgy at the Bergakademie Freiberg and discovered ledeburite in 1882. Ledeburite arises when the carbon content is between 2.06% and 6.67%. The eutectic mixture of austenite and cementite is 4.3% carbon, Fe₃C:2Fe, with a melting point of 1147 °C. Ledeburite-II (at ambient temperature) is composed of cementite-I with recrystallized secondary cementite (which separates from austenite as the metal cools) and (with slow cooling) of pearlite. The pearlite results from the

eutectoid A eutectic system or eutectic mixture ( ) is a homogeneous mixture that has a melting point lower than those of the constituents. The lowest possible melting point over all of the mixing ratios of the constituents is called the ''eutectic tempe ...

al decay of the austenite that comes from the ledeburite-I at 723 °C. During more rapid cooling,

bainite Bainite is a plate-like microstructure that forms in steels at temperatures of 125–550 °C (depending on alloy content). First described by E. S. Davenport and Edgar Bain, it is one of the products that may form when austenite (the face-c ...

can develop instead of pearlite, and with very rapid cooling

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 ...

can develop.

External links

Names and SteelKarl Heinrich Adolf Ledebur
(in German)
Rostfreier Edelstahl
(in German) Metallurgy Ferrous alloys {{industry-stub