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Gray iron is the most versatile of all foundry metals. The high carbon content is
responsible for ease of melting and casting in the foundry and for ease of
machining in subsequent manufacturing. The low degree or absence of shrinkage and
high fluidity provide maximum freedom of design for the engineer.
The general composition of gray cast iron is 95% iron by weight with an
additional 2.1 to 4% being carbon and 1 to 3% silicon. Manganese and other
impurities are also commonly found in or added to molten iron as needed for the
diminishing or enhancement of specific properties. Sulfur, for example, is
commonly introduced to the molten metal in order to increase hardness, which is
otherwise low in most cast iron components.

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