The different heat treatments that can be given to metals allow their characteristics to be modified. They are treatments of great importance in the different stages of manufacturing in the machining industry. At Mecanizados Delinte we use the tempering technique when shaping products such as swas frames, motor center cabinets, etc.
There are different types of heat treatments depending on the objective to be achieved and the reactions that are achieved are obviously also different. This type of treatment hardens or softens a product, modifies its structure or changes some of its characteristics so that the final result meets our needs.
The different heat treatments include carburizing, nitriding, tempering, carbonitriding, annealing, normalizing, isothermal annealing and quenching.
Tempering, the main treatment in the industry
Tempering is one of the most widely used heat treatments in the machining field. Basically, it consists of heating a material, usually steel, above its transformation point. We are talking about temperatures that may well exceed 800 or 900 degrees Celsius, and cool it quickly in water or oil. The purpose of this whole process is to obtain a much more resistant piece, in which its degree of fragility is reduced.
The tempering process seeks to achieve a balance between hardness and strength in the product.
Although it may seem strange, the use of tempered steel has been used for centuries. Already in feudal Japan, blacksmiths were in charge of making katanas, swords and other weapons with this material. To do this they smeared clay on specific parts of a steel blade and heated it in a forge, then cooled the blade in water.
Obviously today’s work processes have evolved, but at the core, the objective and principles remain the same.
Of course, steel is not the only metal that can be tempered, but it is one of the metals that offers the most possibilities, since by doing so, very attractive qualities can be achieved. For example, it is made to have a higher degree of hardness, to be less fragile, to withstand greater forces, to relieve stresses, etc.
How and why steel is hardened
To harden it, the steel must be heated to a temperature that exceeds its transformation point, which is called the quenching temperature. In this way it is possible to vary its structure, obtaining a crystalline structure that is ideal for rapid cooling of the piece. The cooling must be carried out in a certain way that will vary according to the composition of the steel in order to obtain the desired equilibrium.
To obtain different types of hardening , other elements such as carbon, nitrogen, cyanides or other compounds can be added.
The process of heating steel is called austenitization. What is achieved by heating it is to accommodate much more carbon in its structure, forming austenite, which is nothing more than a certain arrangement of iron and carbon atoms. Upon rapid cooling, martensite is formed, i.e., a crystal that gives the steel its maximum possible strength.
A complete part, including its core, can be hardened. Or only its external surface can be hardened, giving the core a different degree of hardness and flexibility.
In short, steel tempering provides this material with the properties we need to be able to manufacture parts that are resistant and suitable for the work for which they are intended, such as swas frames.