Today, metalworking has become more precise and sophisticated than before. Heat treatment is one of the many techniques that can be used for various purposes. This treatment process involves heating and cooling metals to alter their microstructure and bring out their mechanical and physical characteristics, increasing their desirability. The properties of metals are significantly changed by the temperature they are heated to and the rate of cooling.
Metals usually go through heat treatment to enhance their hardness, strength, ductility, toughness, and corrosion resistance. Below are heat treatment techniques used for heating metals:
Annealing
This technique is often used for softening steel, iron, silver, and brass. It includes heating the metal to a certain temperature and letting it cool slowly at a controlled rate. This technique changes a metal’s chemical and physical properties increasing its ductility and minimizing hardness. Also, annealing facilitates stamping, shaping, and forming processes as well as makes it easier to cut the metal.
Normalizing
This heat treatment process applied to alloys to ensure uniformed grain size and composition. The process involves heating the metal to a predefined temperature and cooling it by air. The final product does not have undesirable impurities and is harder and stronger. Usually, normalizing is used for the production of stronger and harder Houston steel. Typically, this process is carried out on materials which will be subjected to machining.
Hardening
This technique is applicable to steel and other alloys to enhance their mechanical properties. This treatment process involves heating the metal at a high temperature which is maintained until a part of carbon has been dissolved. Then, the metal undergoes quenching where it is being rapidly cooled in oil or water. Hardening is expected to produce an alloy with high strength and resistance to wear. But, as it can also increase brittleness, it is not ideal for engineering applications.
Stress Relieving
This heat treatment process involves reducing stress in metals after quenching, casting, and normalizing them. To relieve stress, a metal is heated to a temperature lower than the temperature required for transformation. The metal is then slowly cooled after this treatment process.
Tempering
This process is applied to steel where ductility maters. Untempered steel is expected to be extremely hard and too brittle for the majority of practical applications. Tempering involves treatment metals at a low temperature, often done after hardening to achieve the desired hardness ratio. In this process, steel is being heated to a lower temperature to minimize some of the excess toughness.
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