The form of carbon in carbon steels
The solubility of carbon content when the iron carbon alloy than in the iron when the excess carbon can be in the form of carbide iron or elemental state (graphite) in alloy, which can form a series of carbide, Fe3C (cementite, 6.69%C) is a metastable phase, it is a compound complex structure gap. Graphite is a stable phase of iron carbon alloy with simple six - party structure. Fe3C has the potential to break down into iron and graphite stable phases, but the process is extremely slow at room temperature.
In solid solution, it is in the interstitial space of lattice, resulting in lattice distortion. The solubility of carbon in gamma -Fe is maximal, but not more than 2.11%; the solubility of carbon in alpha -Fe is not more than 0.0218%; and in Delta 6-Fe, no more than 0.09%.
There are three solid solutions of carbon in iron: alpha solid solution (Tie Suti), gamma solid solution (austenite) and delta solid solution (8 ferrite). The spatial distribution of iron atoms in these solid solutions is consistent with that of alpha -Fe, gamma -Fe and delta -Fe. The size of carbon atoms is much smaller than that of iron atoms.
