Modeling of Austenitization Kinetics under Continuous Heating of Steels with Complex Microstructure

摘要

A quantitative mathematical model describing the austenitization kinetics of steels with complex microstructure and predicting austenite grain size in dependence on the heating rate, chemical composition, volume fractions of structural components (ferrite, pearlite, bainite, martensite) and ferrite grain size was developed. The set of empirical parameters of the model was obtained basing on the experimental data on kinetics of austenitization under continuous heating of various microstructures of 8 industrial steel grades with wide range of chemical compositions (C(0.08÷0.66), Mn(0.37÷1.55), Si(0.2÷0.56), Cr(0.10÷1.08), Ni(0.06÷1.94), Mo(0.01÷0.52), Nb(0.003÷0.041), V(0.002÷0.15), Ti(0.002÷0.063) (mass.%)), as well as on the final austenite grain size. In the initial state steels had pearlitic, ferritic-pearlitic, ferritic-bainitic, bainitic-martensitic and other more complex microstructures. Before studying austenitization under continuous heating from room temperature at rates of 0.5, 1, 3, 10, 50°C/s, steels samples were thermally pretreated to obtain the desired spectrum of microstructures. All experiments were performed using the Pocket Jaw unit of Gleeble 3800 complex. The kinetics of steels austenitization and austenite grain size predicted by the developed model are in good agreement with experimental data.