During the self - regulated thermal process, the surface temperature of quenched steel part maintains at the level of boiling point of a liquid and cannot be below it until boiling is finished. Within the last three decades, the self - regulated thermal process was used for designing the original quenching processes to improve significantly mechanical properties of a material and use less alloy steels. However, the self - regulated thermal process is not familar to many engineers since it cannot be predicted when using effective heat transfer coefficients during hardening of steel.
The self - regulated thermal process can be used:
1. In forging industry to perform direct quenching under pressure.
2. In bearing industry to quench bearing rings and rollers in water and water solutions.
3. In metallurgy to enhance high temperature and low temperature thermo - mechanical treatment of different materials.
4. In tool industry to improve quality of tools.
4. It can be used to perform two step quenching to increase significantly strength, plasticity and tribological properties of materials.
Dear Nikolai, I thank you, practically you have introduced this quenching technique to our attention since it is not very well known outside of the industrial circles dealing with the manufacturing of super sensitive parts and tools.
I though by using certain additive to the liquid in question one may control the boiling points and this way one could perform isothermal quenching any desired temperature. As you have said the heat transfer coefficient may be the bottle neck in the estimation of the heat extraction rate to calculate the quenching time or the amount of liquid needed for the completion of the process. I am not very familiar how the boundary layer theory should be modified to cope with the surface, which is now acting as a substrate or heterogeneous nucleation site for the boiling, and loosing large amount of enthalpy of evaporation via bobbling liquids particles with variety of sizes. But it is quite clear, it is very interesting problem for the heat transfer people in ME. Best Regards
I am curious if you have tried using any of the interesting spectrum of liquid metals to control the cooling process. I am purely a spectator in this subject not an expert. Their huge thermal conductivity might allow some interesting controls on crystal growth rates and avoid cavitation but they also might infuse into the surface in produce more stress there. Maybe this is already done and tried but thought I would ask.
I think the biggest trouble to use liquid metal as a quenching media its potential ability to penetrate or better to say to diffuse into the test modulus thereby change its surface properties drastically, unless it has no solubility. I remember the time how our niobium test bar melted or completely dissolved in aluminum melt about 700o C which is much lower than the melting temperature of Nb, Tm= .2477o C
Dear Tarik,
Thanks ! You are absolutely correct. Yes, .. "one may control the boiling points and this way one could perform isothermal quenching any desired temperature". Here duration of transient nucleate boiling process is very important too.
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