H21 HOT WORK TOOL STEEL
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STRESS
RELIEVING |
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| Heat to 600°C / 650°C. Hold for 2-4 hours and furnace cool. |
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HARDENING |
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| Before heat
treatment, sufficient machining should be carried out to remove surface decarburisation. Hardening should be carried out in controlled atmosphere furnaces or neutral salt baths. Preheat slowly to 800°C / 850°C then transfer to a bath or furnace at 1120°C / 1170°C allowing sufficient time for uniform heating. Quench into warm oil or salt bath operating at 520°C / 540°C. In the latter case ensure that the tools are allowed to equalise before completing the quench by cooling in air. * The hardening temperatures given above are for salt bath treatment. For atmosphere furnace hardening, there temperatures should be increased by 15°C. |