INTRODUCTION
Grey cast iron, vermicular cast iron and spheroidal graphite cast iron are three main types of cast iron used in engineering practice. Each type of cast iron has properties that make it suitable for specific engineering applications. The mechanical properties of these three cast iron materials will be discussed in this essay, including elastic behaviour, plastic behaviour, and strength at different temperatures.
GREY CAST IRON
Grey cast iron is the oldest and most common type of cast iron. As the name implies, grey cast iron is grey in colour and has a greyish-white cast surface. The structure of grey cast iron consists of graphite in the form of flakes, and iron carbide (cementite), which is embedded in a matrix of ferrite or pearlite.
Grey cast iron has good machinability and excellent vibration damping characteristics. These characteristics make it well-suited for a variety of engineering applications, including engine blocks, gears, shafts, and machine tool components.
Grey cast iron is relatively inexpensive and is often used to produce parts that require only moderate strength and wear resistance.
GREY CAST IRON MECHANICAL PROPERTIES
Grey cast iron has a relatively low tensile strength, but it is highly ductile. It exhibits good elastic behaviour at room temperature, with a modulus of elasticity of around 16 GPa. At high temperatures, however, its ductility decreases and its modulus of elasticity increases.
Grey cast iron exhibits plastic behaviour under load and has a yield strength of around 200 MPa. Grey cast iron is relatively brittle, especially at low temperatures, and its strength decreases rapidly with increasing temperature.
VERMICULAR CAST IRON
Vermicular cast iron is an alloy of iron and carbon that is similar to grey cast iron, but with a higher carbon content. The carbon forms globules of graphite rather than the flake-like graphite structure seen in grey cast iron.
Vermicular cast iron is more expensive than grey cast iron, but it is stronger and more wear-resistant. It is also more difficult to machine than grey cast iron.
VERMICULAR CAST IRON MECHANICAL PROPERTIES
Vermicular cast iron has a higher tensile strength than grey cast iron, with an ultimate tensile strength of roughly 250 MPa. It also exhibits higher elastic modulus and yield strength than grey cast iron.
Like grey cast iron, vermicular cast iron exhibits good elastic behaviour at room temperature, with a modulus of elasticity of around 18 GPa. However, at high temperatures its strength decreases more slowly than that of grey cast iron, making it more suitable for applications involving high temperatures.
SPHEROIDAL GRAPHITE CAST IRON
Spheroidal graphite cast iron is an alloy of iron and carbon that contains graphite in the form of spheres. This composition gives the material higher strength and wear resistance than grey and vermicular cast iron.
Spheroidal graphite cast iron is more expensive and difficult to machine than grey and vermicular cast iron. It is often used to produce parts that require higher strength and wear-resistance, such as rollers, gear housings, and turbine blades.
SPHEROIDAL GRAPHITE CAST IRON MECHANICAL PROPERTIES
Spheroidal graphite cast iron has a higher tensile strength than grey and vermicular cast iron, with an ultimate tensile strength of around 300 MPa. It also exhibits a higher modulus of elasticity and higher yield strength than the other two types of cast iron.
Like grey and vermicular cast iron, spheroidal graphite cast iron exhibits good elastic behaviour at room temperature, with a modulus of elasticity of around 20 GPa. At high temperatures, however, its strength decreases more slowly than that of grey and vermicular cast iron, making it better suited for applications involving higher temperatures.
CONCLUSION
Grey, vermicular and spheroidal graphite cast iron are three types of cast iron used in engineering practice. Each type of cast iron has properties that make it suitable for specific engineering applications. Grey cast iron is relatively inexpensive and is often used to produce parts that require only moderate strength and wear resistance. Vermicular cast iron is stronger and more wear-resistant than grey cast iron and is often used to produce parts that require higher strength and wear-resistance. Spheroidal graphite cast iron is the strongest and most wear-resistant of the three types of cast iron and is often used to produce parts that require the highest strength and wear-resistance. The elastic, plastic, and strength properties of these three cast iron materials will vary depending on the materials composition and temperature.
