This group of steels is specially designed for use as corrosion-resistant tool steels in plastics processing when corrosion and wear resistance are of primary importance, as is the case, for example, when processing fibre-reinforced and heavily filled, aggressive plastics. Experience shows that corrosion-resistant tool steels with hardnesses of over 50 HRC are then required. Under particularly critical operating conditions, however, steels with a higher carbide content and hardnesses above 60 HRC are often essential.
Steels in this product group are usually selected hardenable, martensitic stainless steels with approx. 13 to 20 % Cr , alloyed with Mo , W and V and a C content of approx. 0.40 to over 2%.
In general, the production of these steels with regard to purity, homogeneity and analytical balance takes special account of the needs of plastics processing with regard to polishability and corrosion resistance, and high-purity steels are frequently produced by remelting processes, e.g. electroslag (ISOPLAST), or extremely homogeneous, high-alloy steels are produced by powder metallurgy (MICROCLEAN).
A speciality is the highly nitrogenous steel BÖHLER M380 ISOPLAST, in which the high C content usual in this steel group has been reduced and part of the C has been replaced by N. This results in a hardness of approx. This achieves a hardness of approx. 58 HRC, the best corrosion resistance and optimum homogeneity, and prevents the excessive bonding of Cr in the form of carbides. Remelting of this steel takes place in the special pressure electroslag remelting process (DESU).
