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US 6,164,079 AGranted
Cryogenic treatment of silicon nitride tool and machine parts
OwnerChristian Clark Waldmann, Fred J. Waldmanninventors
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Abstract
This disclosure describes a cryogenic process for increasing the life of silicon nitride tool materials such as machining inserts used in the high-speed machining of cast irons and other materials. The process entails placing the tools in a cryogenic chamber where the temperature is lowered to about -320.degree. F. and held at that level for a period of time and then raised to ambient temperature. Both the lowering and raising of the temperature are at specifically controlled rates.
Claims1
A process for treating silicon nitride materials which comprises:
- holding a silicon nitride metal item to a sustained temperature of -20.degree. F. to -50.degree. F. for a period of time to effect temperature stabilization;
- applying gaseous nitrogen to said silicon nitride metal item to lower, at a rate no slower than one-half degree F. per minute, its temperature to a temperature within the range of -300.degree. F. to -320.degree. F.;
- holding said temperature for a period of 1 to 24 hours, depending on the volume and mass of the material being treated;
- and increasing the temperature of the item to ambient temperature .
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Dependencies are inferred from the claim text.