Types Of Cast Iron
Cast iron is a group of iron-carbon alloys with a carbon content greater than 2%. It is one of the oldest and most widely used materials in industry, dating back to ancient China and Egypt. Cast iron is known for its excellent casting properties, high wear resistance, and good machinability.
In this article, we will discuss the different types of cast iron and their properties. We will also explore the classification of cast iron based on carbon content. Understanding these types of cast iron is important for engineers and manufacturers who work with this material on a regular basis.
Gray Cast Iron
Gray cast iron is a popular type of cast iron that is known for its excellent machinability and good wear resistance. It is composed of graphite flakes in a matrix of ferrite and pearlite. Gray cast iron has a low melting point, making it easy to cast, and it can be easily machined due to its low hardness.
| Properties | Values |
|---|---|
| Melting Point | 1,150°C (2,102°F) |
| Density | 6. 9 g/cm³ (0. 25 lb/in³) |
| Hardness | 120-220 HB (Brinell hardness) |
The applications of gray cast iron are vast due to its excellent properties. It is commonly used in the manufacturing of engine blocks, pipes, pump housings, and other machinery components.
White Cast Iron
White cast iron is another type of cast iron that has high hardness and brittleness due to its composition of cementite and pearlite. It has a white appearance when fractured hence the name “white” cast iron.
| Properties | Values |
|---|---|
| Melting Point | 1,375°C (2,507°F) |
| Density | 7. 2 g/cm³ (0. 26 lb/in³) |
| Hardness | 350-600 HB (Brinell hardness) |
White cast iron is not commonly used in industrial applications due to its brittleness, but it can be used in the manufacturing of grinding balls and liners for crushing equipment.
Ductile Cast Iron (Nodular Cast Iron)
Ductile cast iron, also known as nodular cast iron, is a type of cast iron that has been treated with magnesium or cerium to produce nodules instead of graphite flakes. This results in a material that has improved ductility and toughness compared to gray cast iron.
| Properties | Values |
|---|---|
| Melting Point | 1,150°C (2,102°F) |
| Density | 6. 9 g/cm³ (0. 25 lb/in³) |
| Tensile Strength | 550 MPa (80 ksi) |
The applications of ductile cast iron are vast due to its excellent properties. It is commonly used in the manufacturing of gears, crankshafts, and other machinery components that require high strength and toughness.
Malleable Cast Iron
Malleable cast iron is a type of cast iron that has been heat-treated to produce a material that is both strong and ductile. It is composed of ferrite and pearlite, similar to gray cast iron, but it has been heat-treated to convert the carbon into graphite nodules.
| Properties | Values |
|---|---|
| Melting Point | 1,150°C (2,102°F) |
| Density | 6. 9 g/cm³ (0. 25 lb/in³) |
| Tensile Strength | 400-500 MPa (58-73 ksi) |
The applications of malleable cast iron are vast due to its excellent properties. It is commonly used in the manufacturing of pipe fittings, hand tools, and other machinery components that require high strength and ductility.
Based on Carbon Content
Cast iron is classified into different types based on its carbon content. The most common types of cast iron are grey cast iron, white cast iron, ductile cast iron, and malleable cast iron.
Grey Cast Iron
Grey cast iron is the most commonly used type of cast iron. It has a high carbon content (2. 5% to 4%) and a low melting point. Grey cast iron is known for its excellent machinability and wear resistance. It is used in the production of engine blocks, pipes, and other industrial components.
| Characteristics | Advantages | Disadvantages |
|---|---|---|
| Dull gray color | Inexpensive to produce | Brittle and prone to cracking under stress |
| Porous surface | Good wear resistance and machinability | Poor tensile strength and ductility |
White Cast Iron
White cast iron has a higher carbon content than grey cast iron (up to 4%). It is known for its hardness and brittleness. White cast iron is used in applications where high wear resistance is required, such as in grinding balls and liners for ball mills.
| Characteristics | Advantages | Disadvantages |
|---|---|---|
| Bright white color | Very hard and wear-resistant | Brittle and prone to cracking under stress |
| Smooth surface | Good for high-wear applications | Poor machinability and ductility |
Ductile Cast Iron (Nodular Cast Iron)
Ductile cast iron, also known as nodular cast iron, has a lower carbon content than grey or white cast iron (1. 8% to 2. 8%). It is known for its high strength, toughness, and ductility. Ductile cast iron is used in applications where high strength and toughness are required, such as in crankshafts and gears.
| Characteristics | Advantages | Disadvantages |
|---|---|---|
| Malleable surface with nodules of graphite | Toughness and ductility similar to steel | More expensive than grey or white cast iron |
| High tensile strength and impact resistance | Good machinability and wear resistance | Susceptible to heat damage during casting process |
Malleable Cast Iron
Malleable cast iron has a lower carbon content than grey or white cast iron (up to 2. 1%). It is produced by annealing white cast iron in a furnace at a temperature of around 900°C. Malleable cast iron is known for its ductility and toughness. It is used in applications where high strength and toughness are required, such as in pipe fittings and agricultural machinery.
| Characteristics | Advantages | Disadvantages |
|---|---|---|
| Malleable surface with nodules of graphite | Toughness and ductility similar to steel | More expensive than grey or white cast iron |
| High tensile strength and impact resistance | Good machinability and wear resistance | Susceptible to heat damage during casting process |