Cast iron is a group of iron-carbon alloys with a carbon content greater than 2%. The different types of cast iron are differentiated by their composition, microstructure, and properties. The most common types of cast iron are:
- Gray iron: This is the most commonly used type of cast iron and is named for the gray color of the fracture surface. It contains flakes of graphite in a matrix of ferrite and pearlite. Gray iron is easily cast and machined, and has good wear resistance.
- Ductile iron: Also known as nodular cast iron or spheroidal graphite iron, this type of cast iron has nodules of graphite in a matrix of ferrite and pearlite. Ductile iron is more ductile and has higher tensile strength than gray iron, making it suitable for use in applications that require high strength and toughness.
- White iron: This type of cast iron is named for its white color and contains cementite instead of graphite. White iron is very hard and brittle, making it difficult to machine. It is often used in applications that require high wear resistance, such as in mining and crushing equipment.
- Malleable iron: This type of cast iron is heat-treated after casting to convert the carbon in the iron to graphite nodules. Malleable iron is more ductile than gray iron and can be bent or twisted without breaking. It is commonly used in pipe fittings, hand tools, and machinery.
- Compacted graphite iron: This type of cast iron has a microstructure that is intermediate between gray and ductile iron, with both graphite flakes and nodules. Compacted graphite iron has high strength and good thermal conductivity, making it suitable for use in diesel engine blocks and other high-stress applications.
