Cast iron is one of the oldest ferrous metals used in construction
and outdoor ornament. It is primarily composed of iron (Fe),
carbon (C) and silicon (Si), but may also contain traces of sulphur
(S), manganese (Mn) and phosphorus (P). It has a relatively high
carbon content of 2% to 5%. It is hard, brittle, nonmalleable
(i.e. it cannot be bent, stretched or hammered into shape) and more
fusible than steel. Its structure is crystalline and relatively
brittle and weak in tension. Cast-iron members fracture under
excessive tensile loading with little prior distortion. Cast iron
is, however, very good in compression. The composition of cast
iron and the method of manufacture are critical in determining its
characteristics.