01-02-2011, 12:13 PM
ABSTRACT:
The term Cryogenic is derived from the Greek word ‘Cryo’ which means ice, cold or frost ‘genics’ means born. Cryogenic deals with production & utilization of low temperature below 0oc. The oxygen was firstly liquified in 1877 by coilletet & pietet in USA. The research work is also start at that time.
Cryogenic is of great importance in our day to day life applications and also is specialized applications.
Space research, it is used as a fuels in rocket, commercial application, Cryobilogy, Cryosurgery, in computers and industries.
Cryogenic treatment is very benifited as computer to conventional heat treatment. In conventional heat treatment austenite is converted into martensite. The conversation percentage of martensite on range of 30% to 50%. The retained austenite forms cracks in metal which reduce tool life. But when we Cryotreat the tool below 0oc using liquid Nitrogen. The austenite completely converted into martensite and martensite is hard so tool life is increased.
Actual Cryogenic treatment on tools can be done by two methods
1. Shallow Cryogenic process
Cooling at –120oc by means of dry ice or ultra cold nitrogen.
2. Deep Cryogenic process
Deep Cryogenic process means cooling at -196oc by liquid nitrogen.
After Cryotreatment mechanical properties are improved like strength, fatigue strength, impact strength, hardness and wear properties and thermal conductivity with tool life and when we perform actual Cryogenic treatment on tool the life of tool increased by 44%.
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