This group of steels is specifically intended for use as corrosion-resistant tool steel in plastics processing.
Pre-tempered steels are steels that are already quenched and tempered by the steel supplier, usually with hardnesses of 30 to 40 HRC, and are then delivered to tool production in this condition. By omitting the heat treatment in the course of tool production, the economic efficiency can be significantly improved. With the delivery hardness in the range of approx. 30 to approx. 40 HRC, there is a good compromise between machinability and wear resistance or compressive strength (edge stability), which is sufficient for many applications in plastics processing.
Steels in this product group are usually selected martensitic stainless steels with approx. 13 to 17 % Cr , alloyed with Mo and Ni and a C content of approx. 0.30 to 0.40%.
In the production of these steels, special consideration is given to the needs of plastics processing with regard to polishability and corrosion resistance in terms of purity, homogeneity and analytical balance.
In special cases, the microstructure is specifically optimised by a special analytical balance, as is the case with BÖHLER M315 EXTRA, for example, and sulphur is added in small proportions (0.10 to approx. 0.20%) to improve machinability. However, due to the addition of sulphur, losses in corrosion resistance and polishability have to be taken into account.
