Quenching is a heat treatment that is carried out on carbon steel to modify certain physical characteristics such as its mechanical resistance.

Given the acquired properties, quenched and tempered steel is processed to create products that are subjected to continuous physical stress. Its use is therefore particularly widespread, for example, in the machinery manufacturing, automotive and surgical industries, which require a considerable degree of hardness for their products. Resistance to abrasion, on the other hand, is the property that makes quenched and tempered steel particularly suitable for making machine tools and components for means of transport.

One tree brandsreviews

The martensite that forms as a result of the cooling phase is a structure characterized by hardness and a considerable breaking load. The quenching, which allows its formation, gives the steel tensile strength, an increase in the elastic limit and hardness.

Cooling is performed by immersing the steel in a liquid or gas, called a “quenching medium”, which must cool it rapidly without producing steam, since this hinders the formation of martensite. There are three main quenching mediums used:

One tree brandsproducts

Once these procedures have been completed the quenched steel will be resistant to impact, traction, pressure, torsion and wear.

Not all steels can be quenched: to be subjected to this procedure the steels must have a high carbon content, or they must have a medium carbon content but they must contain some alloying elements that favour hardening.

After cooling the product must be cleaned to eliminate the impurities left on the surface by the quenching medium. This operation must be carried out before proceeding with the last phase, namely the one in which the steel is normalized: the product is heated again to refine its grain.

The procedure consists of heating the steel which is brought to high temperatures to modify its internal structure and then cooled.

The cooling phase is particularly delicate in the case of very thick steel pieces, as it is complex to maintain the same temperature stage for the whole piece with a single operation. This is why in this case the cooling is carried out gradually to avoid a significant difference in temperature between the outside and inside of the product, with consequent cracks due to the formation of martensite.

Furthermore, following cooling, a further treatment called “tempering” can be performed, which improves resilience, or rather resistance to impact. In this case the steels are defined as steels for “quenching and tempering” or “quenched and tempered” steels.

Heating aims to modify the internal structure of the steel, leading it to acquire that of austenite (hence the name of the maintaining temperature), while the rapid cooling serves to transform the structure again, bringing the steel to acquire the structure of martensite.

Steels with a carbon content lower than 0.4% however cannot be quenched but in some cases their resistance to impact can be improved with surface treatments.