H13 tool steel heat treatment
H13 tool steel heat treatment, including:
girdling
Heat evenly to 845 to 900°C (1550 to 1650°F) in a controlled atmosphere oven or place the part in a neutral compound to prevent decarburization and hold to equalize the temperature; Cool very slowly in the oven to approximately 480°C (900°F) and then more quickly to room temperature. This treatment should result in a fully spherical microstructure without carbide networks at the grain boundaries.
Hardening
Preheat to 790 to 815°C (1450 to 1500°F), then continue heating evenly to 995 to 1025°C (1825 to 1875°F), soak for 20 minutes, plus 5 minutes per 25 mm (1 in.) thick (minimum 25 minutes); fresh in the still air. For some applications, oil quenching can be done from the lower limit of the hardening temperature, but there is a risk of distortion or cracking. Air cooling is preferred and is usually done on the higher side of the hardening temperature range.
Temperament
Tempered at approximately 510°C (950°F) for maximum hardness and strength, but best tempered at higher temperatures to decrease hardness or strength levels while increasing toughness and ductility.
Stress relief
Heat to 650 to 675°C (1200 to 1250°F) and soak for 1 hour or more; cool slowly to room temperature. This treatment is typically used to achieve greater dimensional accuracy in heat-treated parts by relieving stress from rough machined parts, followed by finish machining and finally heat treatment to the desired hardness.
Nitride
Finished, heat-treated parts can be nitrided to produce a highly wear-resistant surface. Because it is carried out at normal tempering temperatures, nitriding can serve as a second temper in a double tempering treatment. The depth of the nitride layer depends on time at temperature. Deeply nitrided parts are usually ground or lightly surface ground to remove the thin, brittle white layer. Selective nitriding is sometimes performed to produce a nitrided shell only when necessary. Copper plating is best for sealing areas that do not require nitriding; Stops that contain lead should be avoided as lead can make H13 steel brittle.
Normalizing
Not recommended
