Such steels have to withstand operating temperatures and pressures as well as corrosive effects of polymers and abrasive effects of fillers as occurring in the plastics processing industry. Long tool life and therefore low cost per plastic part is decisive. Good corrosion resistance and good surface finishing are critical. In particular in the latter regard, tungsten-containing PM steels have entered this market successfully. Plastic mould steels contain up to 1.2% W.