Steels of groups A and D as well as 8%Cr or High-V-PM steels are usually austenitized in vacuum furnaces or in various types of furnaces using gaseous atmospheres.
Whereas for conventionally produced cold-work tool steels the adjustment of the working hardness is usually done by a combination of different austenitizing and tempering temperatures, PM steels are typically tempered in a small tempering range, from about 550 to 560°C (1020 to 1040°F) with a variation in austenitizing temperature to adjust the hardness level , as shown in the graph.
This different procedure is explained by the toughness results, which increase when austenizing temperature is reduced. Furthermore, because of high content of fine dispersed stable carbides, grain growth at high temperatures does not take place in these steels. Typical austenitizing temperatures therefore range from 1000 to 1180°C (1830 to 2160°F).
Volume 4D, Heat Treating of Irons and Steels -> Tool Steels -> Heat Treating of Cold-Work Tool Steels—Medium-Alloy Air-Hardening, High-Carbon High-Chromium and High-Vanadium-Powder Metallurgy Steels -> Recommended Heat Treating Practices
