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An experimental investigation of the austenitization under continuous heating of various microstructures of 8 industrial steel grades with wide range of chemical compositions was carried out. A quantitative mathematical model describing the austenitization kinetics of the steels with complex microstructure and predicting austenite grain size in dependence on the chemical composition, volume fractions of structural components (ferrite, pearlite, bainite, martensite), ferrite grain size and heating rate, was developed. Values of the model empirical parameters were defined basing on the obtained data on kinetics of austenitization, as well as on the measured final austenite grain size. All experiments were performed using the Pocket Jaw unit of the Gleeble 3800 complex. The kinetics of austenitization and the austenite grain size predicted by the developed model are in good agreement with experimental data.

The effect of Thermomechanical Processing (TMP) using hot rolling on the structure, rolling pressure,mechanical properties of titanium and niobium alloyed 18Cr-10Ni austenitic stainless steels (type AISI 321)is presented. It has been found that the strengthening effect of TMP depends significantly on the kinetics ofdeformation accumulation schedule. The change in rolling pressure with an increasing number of passes followa similar pattern to the change in strength of the TMP treated rolling section. The basic factor determining thedifference in structure formation of studying steels is thermodynamic stability of the carbide phase under thedifferent rolling accumulation schedules. TEM and light microscopy have been used in structural investigations.TMP with a different accumulation schedule result in increasing of yield strength by 1,3-1,7 times compared toconventional heat treatment value. The short-term high-temperature tensile tests showed that the higher roomtemperature strength level of TMP treated steel was also retained at high temperatures.