What is the composition of cast iron?


Quick Answer

Cast iron is mainly composed of iron, carbon and silicon, with a carbon content of 2 to 5 percent. Cast iron can also contain some sulphur, manganese and phosphorus.

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Full Answer

Cast iron is a term used to describe a range of metals that include certain elemental compositions. Because it contains a mixture of elements, cast-iron metals are considered alloys, with all cast irons containing more than 2 percent carbon.

Cast iron generally is brittle and cannot be bent easily. Cast iron breaks when it is loaded with significant pressure, although the carbon content in cast iron makes this metal good for casting. This type of cast iron is called grey cast iron, and its main characteristic is the grey-colored carbon flakes in its composition.

To produce cast iron, iron ore is deoxidized in a blast furnace. When the ore is melted, it is poured into molds. It cools and forms a scale on the surface that acts as a protective covering for the metal. However, cast iron is naturally prone to rusting because of its high iron composition. When iron comes into contact with oxygen and water vapor, a chemical reaction occurs, and rust is the visible result. Keeping cast iron in an environment with a humidity lower than 30 percent reduces corrosion.

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