Cast iron is an alloy (mixture of metals) that contains about 90 percent iron, 2 to 4 percent carbon, 1 to 3 percent silicon, and smaller amounts of manganese, phosphorus, and sulfur. It is known for its strength, density, and ability to absorb shock and vibration. The high carbon content of cast iron decreases its melting point, making it easier to cast in complicated shapes. Casting is a process in which melted metal is poured into molds and allowed to solidify. All these qualities make cast iron especially useful in producing engine blocks, machinery frames, pipes, fire hydrants, and construction materials.
Gray cast iron contains flakes of a form of carbon called graphite. The graphite makes the alloy brittle. Nodular or ductile cast iron contains spherical graphite, increasing its strength and ductility (ability to be stretched or drawn).
