Introduction
In the production of cast iron, many processes are utilised in order to achieve the desired final product. One of these processes is tempering, which is a method used to reduce the internal stresses that develop in a product during the hardening process. The effect of tempering on cast iron is to produce a largely uniform and improved product, while also increasing its strength.
Process Description
Tempering of cast iron is done by heating the material above its transformation temperature and then cooling it at a controlled rate. During the process, atoms and molecules that created internal stresses during the hardening process re-arrange themselves, resulting in fewer inconsistencies in the structure of the material. This re-arrangement of molecules also increases the strength of the material by decreasing the number of internal voids.
The most common way to temper cast iron is by using a furnace to bring the material to a temperature of 550 to 830 °C. The material is then cooled in an oven or by quenching, which involves quickly immersing the cast iron in water, oil or a special tempering solution to halt the tempering process and allow slow cooling of the material.
The tempering process can be modified in order to achieve different properties in the final product. For example, increasing the tempering temperature and/or decreasing the cooling time will result in a product with higher hardness and strength. Similarly, decreasing the tempering temperature and/or increasing the cooling time will result in a product with a lower hardness and strength.
Advantages
Tempering cast iron can be beneficial in a number of ways. The main benefits that it offers are: improved physical properties, greater ductility, increased strength and hardness, improved surface finish, and increased fatigue resistance.
Tempering can also be used to reduce the size and shape inconsistencies that occur in cast iron during the production process. This allows for increased accuracy and consistency in the final product.
Conclusion
Tempering cast iron is a process that is commonly used to improve the properties of the final product. It involves heating the material above its transformation temperature and then cooling it at a controlled rate. The process can be modified in order to achieve different levels of hardness and strength in the final product.
Tempering can be beneficial in a number of ways, including increased strength, ductility, fatigue resistance, surface finish, and accuracy. Overall, it is a process that can be used to produce a high-quality cast iron product.
