Talk about annealing, normalizing, quenching, and tempering [Video]

Annealing, normalizing, quenching, and tempering are several common processes in metal heat treatment, whose main purpose is to modify the properties of metal materials, such as hardness, strength, and toughness. Simply put: - **Annealing**: Heating a metal to a certain temperature and then cooling it slowly. This is done mainly to reduce hardness and eliminate internal stresses, making the material easier to process. - **Normalizing**: Also involves heating to a high temperature, but cooling naturally in the air. It can refine the metal grains, increasing strength and toughness, and is slightly harder than annealing. - **Quenching**: Rapid cooling after heating (for example, with water or oil) makes the metal extremely hard, but it also becomes brittle, so it generally cannot be used directly. - **Tempering**: This usually involves heating after quenching, and then cooling. The goal is to reduce brittleness, adjust hardness and toughness, so that the material is both hard and not prone to breaking. These various processing methods are often used in combination, with the choice depending on the required performance. For example, first quench the part to harden it, and then temper it to reduce brittleness; this way, a material that is both hard and tough can be obtained. .