To create cast iron, pig iron is remelted, usually with large amounts of scrap iron and steel. Other elements are also added before casting. Gray Iron—Commonly includes added silicon. The carbon content,

in the form of graphite flake, is distributed through the metal. Ductile Iron—Includes small amounts of magnesium or cerium to improve workability.

Material	Tensile Strength (psi)*	Yield Strength (psi)*	Hardness (BHN)*	Toughness	Wear Resistance	Formability	Machinability†	Weldability
Gray Iron
Class 40	40,000	—	197-301	Good	Good	Not Recommended	Good	Not Recommended
Ductile Iron
Alloy 80-55-06	80,000	55,000	187-255	Good	Good	Not Recommended	Excellent	Not Recommended
(*) Typical levels @ 1 diameter. (†) Compared to AISI 1212 which has 100% machinability.