A concept on thermal equilibrium establishment to be widely used in heat treating industry and other technological processes

In the paper an universal correlation is proposed for calculating heating and cooling time of any steel part during its hardening. The equation contains Kondratjev form factor K, Kondratjev number Kn, average thermal diffusivity of a material and a function depending on how N - times core temperature of steel part differ from its initial temperature. It is shown that these parameters are enough to calculate recipes when heating and cooling the steel parts of any configuration. A tendency of thermal equilibrium establishment is considered which depends on size and configuration of objects, thermal diffusivity of a material and condition of cooling (heating) characterized by Kondratjev number Kn. The proposed generalized equation provides engineers with extremely simple and understandable parameters for calculating heating (cooling) soak time of any objects. According to proposed equation, the time of thermal equilibrium establishment is directly proportional to Kondrtajev form factor K, inversely proportional to thermal diffusivity of material and Kondratjev number Kn and depends on accuracy of thermal equilibrium measurement.