In Reply to: grain growth posted by Prasanna Kumar.K on 03/07/01 at 1:56 PM:
With 52100 (1% Carbon, 1% chrome) ensure that you have normalized (before machining) at a temperature ABOVE the austenitizing temperature. Harden at a temperature of 810 °C to 820ºC (1490 F to 1510F) Do not let the oil temeprature rise above 10°C on quench. If necessary, put the quench oil through a heat exchanger, then on removal from the oil, allow to cool to hand warmth and cryogenically treat. (use a solution of trichloroethylene and dry ice to make a freezing mixture, or use liquid Nitrogen)
Soakk for 4 (four) hours in the freeze mix. Allow to warm up freely to room temperature, then temper as soon as possible at the appropriate temperature.
The normalize will help to contain grain growth and the freeze will stabilize and transofrm any retained austenite.
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