Steels and metals are mostly leveraged by the manufacturing industries to produce numerous line of products. They’re a boon to engineering. Engineers tailor the mechanical properties of metals with these heat treatments. Might you think, What’s the benefit of tailoring the properties of the metal? Let’s brief you on the purpose of heat treatment:

Use of Heat Treatment on Metal

The fundamental reason for carrying heat treatment process on metals is to improve the mechanical properties of the metal, including hardness, elasticity, tensile strength, resistance to corrosion, and shock resistance.
To alter or refine the grain size.
Improve the machinability.
Increase the surface hardness.
Increase the resistance to corrosion.
To relieve the internal stresses, which may have been developed during the hot or cold working.

Types of Heat Treatment

The heat treatment processes can be categorized into eight different types, which are used to treat steel before manufacturing:

Annealing

Annealing (also referred to as softening process) is one of the most critical methods of heat treatment. Therefore, it’s one of the most widely used operations in treating metals such as steel and iron. In annealing, metal is heated 30 to 50-degree Celcius above the upper critical temperature. Then it is cooled at a prolonged rate. The process aims at making the steel more malleable, ductile, and remove internal stresses.

2. Hardening

The hardening process aims at making the steel hard and tough. During this process, the steel is heated 30 to 40-degree celsius above its upper critical temperature. It’s then followed by a cooling process to bring it to room temperature. The cooling process is done by quenching in water or oil. It can be considered as an opposite process to annealing.

3. Normalizing

Normalizing helps in getting rid of the internal stresses that develop after the cold working process. The metal is heated about 30 to 50-degree celsius above its upper critical temperature and then is left for cooling in air. It’s useful in improving machinability, mechanical, and electrical properties.

4. Cyaniding

The metal specimen is heated in the presence of sodium cyanide. Due to its presence in the environment, nitrogen and carbon atoms gets deposited on the surface of the steel and make it hard. The heat treatment increases the surface hardness and also increases the fatigue limit of the parts such as wrist pins, shafts, and gears.

5. Tempering

During the hardening process, the specimen might become brittle and may inhibit high residual stress. With tempering, the properties of the metal hardened by quenching can be made altered, and the sample can be made more useful. Many industry experts suggest considering tempering process after hardening.

6. Nitriding

In the nitriding process, the surface or case hardening is achieved with the help of nitrogen gas. During the procedure, steel is heated in the presence of an ammonia environment. As a result, nitrogen atoms get deposited on the surface and makes the material hard.

Note: An oxy-acetylene flame heats the specimens with flame hardening objects or Induction hardening.

7. Quenching

When the metal rapidly cools by immersing them into water or oil, it’s quenching process. It also helps in fixing the structure of the specimen in a hardened state.

8. Case Hardening

During this process, the surface of the metal being treated is hardened by first carburizing it and then quenching. So, the metal is treated to harden the case around the center, which remains relatively soft.

That’s all about it. We hope you have collected the necessary information about the heat treatment process employed in the manufacturing field. Share this article with your friends.