Self – regulated thermal process, its main characteristics and practical application

In the paper an overview on self – regulated thermal process and new its characteristics are provided. These specific characteristics of self – regulated thermal process are widely discussed concerning real and effective heat transfer coefficients and Kondratjev numbers Kn. It is underlined that the real heat transfer coefficients (HTCs) should be considered when calculating temperature fields during transient nucleate boiling process and they should refer to boiling point of liquid, not to bath temperature. It is shown that during recipes development for quenching technology, initial austenitizing temperature may be fixed at 850oC for all existing steel grades and irons with the accuracy of calculation . In this case the duration of transient nucleate boiling mode (self – regulated thermal process) is directly proportional to squared size of steel part, inversely proportional to thermal diffusivity of a material and depends on form of product and convective Biot number. Since in heat treating industry historically engineers are dealing with effective HTCs, the new data on effective Kondratjev number are provided to calculate approximately core cooling time and core cooling rate during quenching of steel parts. The obtained results of calculations can be used by engineers and scientists in the field of material and thermal sciences to predict processes within the transient nucleate boiling mode and convection.