Method for the production of plastic moulds made from martensitic chromium steel and plastic mould

The invention relates to a method for producing plastic molds made of a martensitic chromium steel and it relates to a plastic mold. In order to achieve equally high quality values of the mold material, it is provided according to the invention to produce a steel block having the composition in wt% of C = 0.22 to 0.26, Si = 0.01 to 0.35, Mn = 0.15 to 0.60, P = max. 0.025, S = max. 0.003, Cr = 12.0 to 14.0, Mo = 0.10 to 0.18, Ni =0.35 to 0.50, V= 0.15 to 0.25, W = traces up to 0.20, Cu = traces up to 0.30, Co = traces up to 0.20, Ti = traces up to 0.02, Hf = traces up to 0.02, Zr = traces up to 0.02, Al = 0.002 to 0.02, Nb = traces up to 0.04, B = traces up to 0.001, N = 0.08 to 0.15, Ta = traces up to 0.04, As = traces up to 0.005, with the condition: Mn+Ni = 0.55 to 0.95, Mo+W/2 = 0.11 to 0.20, Ti+Hf-FZr = traces up to 0.008, V+Nb+Ta = 0.15 to 0.30, Nb+Ta = traces up to 0.04, Fe and contaminants = the rest, and with a PRE(N) value for the corrosion resistance from more than 14.5 to approximately 15.7, and to subject said steel block to a primary forming at a temperature of more 1050 °C with a forming degree of more than 2.5 fold, optionally after an intermediate cooling, from the blank at a temperature of less than 1050 °C, a manufacturing of at least one basic mold part occurs, from which, optionally after a machining treatment, a plastic mold is produced, and said plastic mold or the basic mold part is austenized and hardened at a cooling rate with a value .lambda. of less than 24, preceded by a tempering treatment is carried out at least twice at a temperature in the range from 510 to 550 °C, resulting in a hardness of the material from 48 to 52 HRC and a toughness thereof, measured on impact bending specimens, of at least 60 J, after which finally a final machining processing occurs, and, if provided for, a polishing of the plastic mold occurs.