Quenched and tempered steels have a chemical composition that has been specifically designed to guarantee the best performance after quenching and tempering heat treatment, consisting of a quenching and subsequent tempering: this process makes the pieces particularly hard and tough, making them suitable for use in even very severe conditions.
Temperability is the capacity of steel subjected to rapid cooling (usually in oil or water) to more or less completely transform its structure, even on larger pieces.
The quenching and tempering treatment is generally carried out on pieces during the final stage of finishing, after most of the mechanical processing. In this case, the semi-finished raw material can be provided in its natural rolling state or annealed for workability, depending on the type of steel.
Thanks to the technologies available, which are in accordance with the most advanced state-of-the-art, Rodacciai can also offer these products in the quenched and tempered state: the treatment is carried out on the rolled semi-finished product before drawing or peeling so that the delivered product has, in any case, the appearance and typical surface characteristics of the cold-finished product.
The complete range of quenched and tempered steels, diversified in terms of chemical composition and, therefore, temperability, allows both the metallurgic and mechanical needs of all customers to be satisfied.
The heat treatments available for this type of steel – to be checked on a case-by-case basis according to the different qualities – are: rolled natural, workable annealed, isothermal annealed, globular annealed, normalized, and quenched and tempered.
Carbon-only steels, temperable, i.e. without the addition of alloy elements, differ from one another in particular due to the greater or lesser presence of carbon - the higher the carbon content, the greater the hardness of the steel in question after the quenching and tempering treatment.
Non-alloyed quenched and tempered steels, in any case, have a limited temperability and do not allow, even when tempered in water, well-transformed structures to be obtained on pieces with elevated thickness.
Steels with alloy elements; contain alloy elements (manganese, chromium, nickel, molybdenum) in variable quantities and proportions that allow the desired temperability to be reached. In this way, larger pieces can be produced with structures transformed even to the core and suitable for the most demanding applications.
The alloy elements are chosen as a function of the type of characteristic that you wish to increase: for example, chromium improves hardness and toughness, while nickel has beneficial effects on resilience, even at low temperatures, and on resistance and fatigue; molybdenum, finally, reduces the phenomenon of fragility upon tempering.
These steels are usually quenched and tempered in oil, which allows the production of pieces with even very complex shapes. The fields of application are quite varied: shaft-type components, gears, linkages, and mechanical pieces of any type.
