Annealing : For annealing, the steel should either be packed in a suitable container, using a neutral packing compound, or placed in a controlled atmosphere furnace. Heat uniformly to 843 / 871 °C and cool very slowly in the furnace at a rate of not more than minus 1 °C per hour until the furnace is black. The furnace may then be turned off and allowed to cool naturally. This will produce a maximum hardness of 241 BHN.

Hardening : H-13 may be air treated or quenched in oil to harden. For air treating, heat the furnace to 1010 / 1024 °C, and then place the tool in the hot furnace near the thermocouple. Let the tool heat ‘naturally’ until it uniformly matches the color of the thermocouple, soak 20 minutes plus an additional 5 minutes per inch of thickness and air cool.

When oil treating H-13, follow the same procedure but drop the temperature to 996 / 1010 °C.

Control of decarburization can be accomplished by using any one of the modern heat-treating furnaces designed for this purpose. If endothermic atmosphere are used, dew point between +4 / 13 °C is suggested. In older type manually operated exothermic atmospheric furnaces, an oxidizing atmosphere is required. Excess oxygen of about 2 to 4% is preferred. If no atmosphere is available, the tool should be pack hardened or wrapped in stainless steel foil to protect its surface.