
Hardening and Tempering of Tool and Die Steels
Hardening involves controlled heating to a critical temperature dictated by the type of steel (in the range 760- 1300°C) followed by controlled cooling. Dependent on the type of material, appropriate cooling rates vary from very fast (water quench) to very slow (air cool). Tempering involves reheating the hardened tool/die to a temperature between 150-675°C, depending on the steel type. A process which controls final properties whilst relieving stresses after hardening, tempering can be com- plex; some steels must be subjected to multiple tempering operations.