Heat treatment is one of the most preferred ways used by industries to make materials more flexible to be molded into their requirements. The reason for the popularity of heat treatment is that it affects multiple aspects of the metal, including the strength, hardness, toughness, formability, ductility, and elasticity. A metal that has undergone the heat treatment process also witnesses a change in its physical and mechanical properties.

Give below are the different types of heat treatment processes that industries use and how they affect the properties of the metal:

Hardening

To harden a metal, the heat treatment process is used by heating the metal to a temperature where the elements in the metals become a solution. Generally, the defects in the crystal lattice structure of metal are the primary source of its plasticity. By undergoing the heat treatment process, the metal is melted into a solution, and fine particles are added to strengthen the metal. After the metal has been heated to the right temperature required to produce a solid solution, it is quenched to trap the particles in the solution. During precipitation hardening, impure particles are added to the metal alloy to strengthen the metal further.

Case Hardening

In this heat treatment process, the external layer of the metal is hardened, while the interior layer of the metal is soft. Moreover, additional carbon is infused into the metal’s surface if it has low carbon content, for example, iron and steel. Case hardening is the last step after the metal has been processed through a machine, and it is used to make the metal more flexible with a durable wear layer. The metal is put through high heat along with other elements to create a hardened outer layer.

Annealing

This treatment process is generally used for metals like aluminum, copper, steel, silver, and brass, wherein the metal is heated to a specific temperature and kept at the same temperature to allow the properties of the metal to transform. After that, the metal is air-cooled. Industries make use of this heat treatment process to decrease the metal’s hardness and increase its ductility to make it more workable. While metals like copper, silver, and brass can be cooled quickly without hampering the treatment, ferrous metals like steel should be cooled gradually, to ensure the annealing takes place effectively.

Normalizing

A branch of annealing, normalizing, is specially used for steel, where the metal is heated to 150-200°F or higher and is held at this temperature to allow the transformation to occur. After being treated, the metal is air-cooled. Some industries may also conduct standardization to remove columnar grains and dendritic segregation, which could occur during the casting of a part.

Tempering

This heat treatment process is used to increase the resilience of iron-based alloys as these metals are usually very hard in nature, but extremely brittle to be used for more applications. Through tempering, the metal’s hardness, ductility, and strength can be changed, depending on what the requirement is. In this process, the metal is heated to a temperature that is below the critical point to reduce the brittleness of the metal, while maintaining the hardness.

Heat treatment processes are vital for industries to create products we use in our daily lives. With the advancement in technology and the introduction of advanced materials, the use of metals will soon dominate our lifestyle.