Cast iron is a four-element alloy c

Cast iron is a four-element alloy containing iron, carbon (between 2 and 4 percent),
silicon, and manganese. Additional alloying elements are sometimes added. The
physical properties of an iron casting are strongly influenced by its cooling rate during
solidification. This, in turn, depends on the size and shape of the casting and on
details of foundry practice. Because of this (and unlike other engineering materials),
cast iron is usually specified by its mechanical properties rather than by chemical
analysis.
The distinctive properties of cast iron result largely from its carbon content.
(1) The high carbon content makes molten iron very fluid, so that it can be poured into
intricate shapes. (2) The precipitation of carbon during solidification counteracts normal
shrinkage to give sound sections. (3) The presence of graphite in the metal provides
excellent machinability (even at wear-resisting hardness levels), damps vibration,
and aids boundary lubrication at wearing surfaces. When “chilled,” that is, when
heat is removed rapidly from the surface during solidification, virtually all the carbon
near the surface remains combined as iron carbides, giving an extremely hard, wearresistant
surface.