Keywords: method, Castul, Castrol, quenching oil, cooling, quenching,

Castul (Castrol) index method
　　Castor proposed the Castor index for grading quenching oils and other cooling media and quenching intensity. The Castul index is defined as:

　　where: Ci is the Castro index; K ' is the equipment constant; CRmax is the maximum cooling rate; Tmax is the temperature at the maximum cooling rate; is the temperature of the quenching medium. The device constant is determined by the following formula:

　　In order to characterize the characteristics of the ability of quenching oil to harden steel, the V value (Tamura & rsquo;SV-value) is proposed. The advantage of the V value associated with the Grossman H factor is that the V value includes the transformation properties of the steel.
The V value can be calculated from the cooling curve of the medium and the continuous cooling transition diagram (CCT) of the steel:

　　where: Tc is the second cooling stage start temperature (characteristic temperature);Td is the third stage (convection stage) start temperature; Ts is the martensite transformation start temperature; Tf is the martensite transformation end temperature. This method is not suitable for characterizing the properties of polymer quenching media.

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