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Old 09-20-2004, 06:42 PM
Quenchcrack Quenchcrack is offline
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Join Date: Jun 2004
Location: NW Tennessee
Posts: 167
Cryo in the freezer

To put it into perspective, most high carbon steels achieve about 90% martensite when quenched down to room temperature. To get the other 10% you must cryo treat it. There is a somewhat linear relationship between the temperature at which you freeze it and the amount of martensite formed. LN is about -300F and your home freezer is about +32F. If you quench to say, 70F, there is a total of 370 degrees you need to get below. If you only freeze down 70-32 = 38 degrees, you have gone 38/370 or 10% of the remaining 10% or about a 1% improvement. Modest but better than a poke in the eye with a pointy stick.

Let me add my firm agreement with the comments regarding tempering and cryo treating. Austenite at room temperature is metastable; it does not want to be there! Tempering will cause the retained austenite to decompose to bainite or even pearlite. Once it has transformed, the cryo is not doing much. Quench it, snap draw it at 250F-300F for about 1/2 hr, cryo and retemper at your normal temperature.


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