Classification of Cast Iron
Cast iron has been used since ancient times, and has been an important material for construction and machinery for centuries. This versatile alloy of iron and carbon is malleable and relatively easy to shape, making it an ideal material for forming or casting into objects or shapes.
Due to its malleability, cast iron is divided into different categories, depending on its structural characteristics. This classification is based on the amount of carbon it contains, as compared to other elements such as silicon, manganese, phosphorus, and sulfur.
Some cast irons have higher carbon content, making them harder, and more brittle than those with less carbon. The four main classes of cast iron are white cast iron, grey cast iron, malleable cast iron and ductile cast iron.
White Cast Iron: This type of cast iron is characterized by high carbon content, usually over 2%, which makes the material brittle and hard. White cast iron is commonly used in applications that require wear resistance, such as agricultural equipment and railcars.
Grey Cast Iron: Grey cast iron contains less carbon than white cast iron, similar amounts of silicon and manganese, and smaller but significant amounts of phosphorus and sulfur. Grey cast iron is well suited for applications that require strength and fatigue resistance, such as engine blocks, pumps and valves.
Malleable Cast Iron: Malleable cast iron contains even lower levels of carbon, with silicon and manganese in similar amounts to grey cast iron. It is typically produced by heat-treating white cast iron, and is used for applications such as car frames and machine parts.
Ductile Cast Iron: This type of cast iron has the lowest carbon content, at less than 2%, and is also the most malleable, with high levels of silicon. Ductile cast iron can withstand higher loads and resist shock better than the other types of iron, making it ideal for car suspension components and motor housings.
Cast iron can also be treated to alter its mechanical properties and add additional strength. Common treatments include heat treatment, alloying, and coating. Heat treatment involves heating the iron to a specific temperature, then immediately cooling it in order to increase the strength and hardness. Alloying involves adding other elements, such as molybdenum or nickel, to the iron in order to increase the alloy’s strength and hardness. Coating involves a metal or synthetic material that is applied to the surface of the iron in order to provide additional protection against rust, corrosion, and chemicals.
Cast iron is an extremely versatile material and can be used in a variety of applications. Thanks to its malleability and relative ease of machining, it can be used for a wide range of components, from simple machine parts to complex items such as engine blocks. By understanding its various categories, it is possible to choose the right cast iron for the job, allowing for effective use and superior performance.
