Cast iron

Cast iron is an alloy of iron with carbon having a carbon content greater than its maximum solubility in austenite (i.e. 2.14%), with the exception of ledeburitic steels. Compared to steels, in addition to more carbon, they also contain more accompanying elements (for example, manganese, silicon, sulfur, phosphorus). Cast iron is produced by remelting suitable pig iron and scrap metal in foundry furnaces, most often in foundries.

Distribution of cast iron
The basic division is given by the method of crystallization:

cement cast irons crystallize according to the metastable Fe-Fe3C system.
white cast iron
graphite cast irons crystallize according to the stable Fe-graphite system.
gray cast iron
ductile iron (for example: bainitic ductile iron)
hardened cast iron is a special type of cast iron in which the composition and thermal conditions of cooling are chosen so that the surface crystallizes metastable and the core crystallizes stably
malleable cast iron crystallizes metastable, but with heat treatment, cementite breaks down into graphite.
with black refraction
with a white break
Another division is given by the presence of additional alloying elements:

alloy cast iron
with increased mechanical physical and technological properties
anti-corrosive
heat resistant
unalloyed cast iron