1. Definition of quenching and tempering

Quenching is a heat treatment method that changes the physical and chemical properties of a metal by heating it to an appropriate temperature and then cooling it quickly. Conversely, tempering is the process of heating the treated metal again to the appropriate temperature after quenching and keeping it cool for a period of time to achieve the desired hardness and toughness.

Second, the difference between quenching and tempering

The difference between quenching and tempering lies in the way the metal is heated. Quenching is the rapid cooling of metal at high temperatures to obtain high hardness and toughness, but the brittleness also increases. Tempering is the process of reheating the quenched metal and cooling it at the appropriate temperature and time. This eliminates the internal stresses that can arise during the quenching process and improves brittleness. In addition, tempering can also improve the strength of the quenched metal.

3. Application of quenching and tempering

Quenching and tempering are two processes commonly used in the heat treatment of metal materials. Quenching is mainly used to make parts with high hardness, high strength, high wear resistance and high toughness, such as steel shafts, hammers and knives. Tempering, on the other hand, is mainly used to improve the brittleness and internal stresses that can occur during the quenching process, and can also restore the original toughness and machinability of the metal, for example in the manufacture of spring steel and wheels.

4. Precautions for quenching and tempering

1. Temperature control: In the process of quenching and tempering, the temperature control of the metal is crucial. Different materials require different temperature and time parameters, and if they get out of control, they may not achieve the desired hardness and toughness, or cause them to fail.

2. Cooling medium: During the quenching process, it is necessary to use cooling medium to quickly cool the metal, and the commonly used media are water, oil and salt water. In the tempering process, appropriate hot plates or air cooling are used to cool down to achieve the required hardness and toughness.

3. Quenching habits: During the quenching process, it is necessary to avoid the occurrence of over-quenching or non-quenching. Overquenching may lead to precipitation and brittleness of some metals, while non-quenching will cause the material to be less hard or even lose its strength.

【Conclusion】

Quenching and tempering are two commonly used processes in the heat treatment of metal materials, quenching is mainly used to manufacture parts with high strength, high hardness and high toughness, while tempering is mainly used to eliminate brittleness and internal stress that may occur during the quenching process, and improve the toughness and machinability of metal. In practical applications, the appropriate process methods and parameters must be selected according to the characteristics of the material and the working requirements, and the temperature and cooling rate need to be strictly controlled to achieve the best results.