Spheroidising treatment is a heat treatment process used to improve the hardenability of low carbon steels. It involves heating the steel to a specific temperature range, holding it at that temperature for a sufficient amount of time, and then cooling it slowly. This treatment modifies the microstructure of the steel, resulting in improved mechanical properties.


- Definition of spheroidising treatment: Spheroidising treatment is a heat treatment process that aims to convert the irregular carbide structures present in the microstructure of low carbon steels into spherical or globular shapes.
- Objective of spheroidising treatment: The main purpose of spheroidising treatment is to improve the hardenability of low carbon steels.
- Definition of hardenability: Hardenability refers to the ability of a steel to be hardened by heat treatment, particularly through the formation of martensite.
- Role of spheroidising treatment in improving hardenability: Low carbon steels typically have poor hardenability, meaning they cannot be hardened to a significant extent by conventional heat treatment methods such as quenching and tempering. This is due to the presence of irregular carbide structures, which hinder the formation of martensite. Spheroidising treatment helps to break down these irregular structures and transform them into spherical shapes, which promotes the formation of martensite during subsequent heat treatments.
- Effect of spheroidising treatment on microstructure: Spheroidising treatment involves heating the steel to a temperature range of approximately 700-900°C for a prolonged period of time, typically several hours. This allows for the diffusion of carbon within the steel, leading to the formation of spherical carbides. The resulting microstructure consists of a matrix of ferrite with dispersed spheroidal carbides.
- Advantages of improved hardenability: By improving the hardenability of low carbon steels, spheroidising treatment enables them to be hardened to a greater depth, resulting in increased strength and wear resistance. This makes them suitable for applications where high mechanical properties are required, such as in the manufacturing of gears, shafts, and springs.
- Comparison with other heat treatment processes: Spheroidising treatment differs from other heat treatment processes such as annealing or normalizing, which aim to refine the microstructure of steels without specifically targeting the improvement of hardenability.
- Conclusion: In summary, the main purpose of spheroidising treatment is to improve the hardenability of low carbon steels by converting irregular carbide structures into spherical shapes. This treatment enhances the ability of the steel to be hardened through subsequent heat treatments, resulting in improved mechanical properties.