Ledeburite

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Iron alloy phases
Austenite (γ-iron; hard) Bainite Martensite Cementite (iron carbide; Fe₃C) Ledeburite (ferrite - cementite eutectic, 4.3% carbon) Ferrite (α-iron; soft) Pearlite (88% ferrite, 12% cementite)
Types of Steel
Plain-carbon steel (up to 2.1% carbon) Stainless steel (alloy with chromium) HSLA steel (high strength low alloy) Tool steel (very hard; heat-treated)
Other Iron-based materials
Cast iron (>2.1% carbon) Wrought iron (almost no carbon) Ductile iron

Iron-carbon phase diagram, showing the iron-carbon phase diagram (near the lower left).

In iron and steel metallurgy, Ledeburite is the eutectic that results when a molten ferrite-cementite at 4.5% carbon concentration solidifies.

Ledeburite is named after Adolf Ledebur (1837-1916). He was the first professor of matellurgy at the Bergakademie Freiberg. He discovered ledeburite in 1882.

Ledeburite is some eutectic structures of iron-carbon alloys. It was named after its discoverer, the metallurgist Karl Heinrich Adolf Ledebur. Ledeburite arises when the carbon content is between 2.06% and 6.67%. The eutectic mixture is 4.3% carbon. Its melting point is 1.147°C. At 4.3% carbon the metal becomes 100% ledeburite. Ledeburite is not a phase, it is a phase mixture, of austenite and cementite.

Ledeburite has two forms: Ledeburite I and Ledeburite II.

Ledeburite I (close below 1.147 °C) is made of austenite and cementite.

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 eutectoidal decay of the austenite that comes from the Ledeburite I at 723 °C. During faster cooling, bainite can develop istead of pearlite, and with very fast cooling martensite can develop.