H13 Tool Steel Heat Treatment
H13 tool steel heat treatment including:
Heat uniformly to 845 to 900 °C (1550 to 1650 °F) in a controlled atmosphere furnace, or place the part in a neutral compound to prevent decarburization and hold to equalize temperature; Cool very slowly in the oven to approximately 480 °C (900 °F), then more rapidly to room temperature. This treatment should result in a fully spherical microstructure without grain boundary carbide networks.
Preheat to 790 to 815 °C (1450 to 1500 °F), then continue heat uniformly to 995 to 1025 °C (1825 to 1875 °F), soak for 20 minutes, plus 5 minutes per 25 mm (1 in) thickness (min. 25 minutes); cool in still air. For a few applications, oil quenching can be done from the low end of the hardening temperature, but there is a risk of distortion or cracking. Air cooling is preferred and is usually done from the high side of the hardening temperature range.
Temper at approximately 510 °C (950 °F) for maximum hardness and strength, but better tempered at higher temperatures to lower hardness or strength levels while increasing toughness and ductility.
Heat to 650 to 675 °C (1200 to 1250 °F) and soak for 1 hour or longer; cool slowly to room temperature. This treatment is typically used to achieve greater dimensional accuracy in heat-treated parts by stress-relieving rough-machined parts, followed by finish machining, and finally heat-treating to the desired hardness.
Finished and heat treated parts can be nitrided to produce a highly wear-resistant surface. Because it is carried out at normal tempering temperature, nitriding can serve as the second temper in a double-tempering treatment. The depth of the nitride layer depends on the time at temperature. Deeply nitrided parts are usually ground or lightly surface ground to remove the thin, brittle white layer. Selective nitridation is sometimes performed to produce a nitrided shell only where needed. Copper plating is best to seal off areas that do not require nitriding; stop-offs containing lead should be avoided as lead can make H13 steel brittle.