and processing of steels
Heat treatments for your products to impart them the desired mechanical properties.
Consists in a phase of heating and maintaining at high temperature followed by a rapid cooling with water (black finish which requires a subsequent pickling treatment) or inert gas (bright finish), designed to put back into solution (and therefore to avoid) the precipitates chromium carbides, which would otherwise have time to form in the case of a slower cooling. The chromium carbides are typically responsible for the intercrystalline corrosion.
It consists in heating the material at a temperature slightly higher than the austenitizing, then stay for about 15 minutes at this temperature, such as to reach the balance in the microstructural and cooling in still air.
This process is similar to the annealing, but in this case the cooling is more rapid.
The main objective is to refine the crystal grain size of the steel, uniform microstructure and mitigate the extent of layered bands of different phases (structure that is likely to emphasize the behavior of the weakest phase
During the quenching of steels is the formation of martensite, a structure with high hardness and considerable tensile strength, but with a quite low toughness that may result in breakage due to shocks. Subjecting the steel to a tempering thermal treatment, transforms the martensite into tempered martensite. In fact, the martensite is a metastable phase, that is formed only because the carbon atoms are not able to escape from the lattice due to the high cooling rate that prevents the diffusive motions .. Generally steels used in this treatment have 0, 4 to 0.6% of C and are precisely those steels. Is defined remediation this sequence of treatments only in the case where the tempering takes place at a temperature higher than 550 Â° C (except in the case of steel for springs which are found at about 450 Â° C). Bringing the martensite at this temperature it comes to, becoming sorbitol, a structure which combines a good tensile strength, even if lower than that of martensite, to a greater toughness.