168 Forgings network: five basic structures of iron – carbon alloy!

1. The ferrite
Ferrite is a interstitial solid solution formed by carbon dissolved in -Fe. It is often expressed as or F.It maintains the bulk centered cubic lattice structure of alpha -Fe.Ferrite has low carbon content, and its mechanical properties are close to those of pure iron, high plasticity and toughness, and low strength and hardness.
2. The austenite
Austenite is A interstitial solid solution of carbon dissolved in -Fe, usually expressed as or A.It maintains the face-centered cubic lattice structure of gamma-Fe.Austenite has higher carbon solubility than ferrite, and its mechanical properties are characterized by good plasticity, low strength, low hardness and easy plastic deformation.

3. The cementite
Cementite is a compound formed by iron and carbon, whose chemical formula is Fe3C.It contains 6.69% carbon and has a complex crystal structure.The cementite has a very high hardness, poor plasticity, almost zero, and is a hard and brittle phase.Cementite plays a strengthening role in carbon steel.In iron-carbon alloys, the higher the carbon content, the more cementite, the higher the hardness and the lower the plasticity of the alloys.
4. Pearlite
Pearlite is a mechanical mixture of ferrite and cementite, usually denoted by P.The average carbon content of pearlite is 0.77%, and its mechanical properties are between ferrite and cementite, with high strength, moderate hardness and certain plasticity.By heat treatment, the cementite can be distributed in granular form on the ferrite matrix. This kind of structure is called spherical pearlite, and its comprehensive performance is better.
5. Ledeburite
Leutenite is a mechanical mixture of austenite and cementite, usually expressed as Ld.The average carbon content of Leutenite was 4.3%.When cooled to 727℃, the austenite in leustenite will be converted into pearlite.So below 727℃, leutenite consists of pearlite and cementite, called leutenite at low temperature, denoted by Ld '.The microstructure of Leutenite is based on cementite, so its mechanical properties are hard and brittle.