Comparative analysis of the martensitic transformation kinetics in low-alloy structural steel by dilatometric and calculation methods

A comparative analysis of the athermal martensitic transformation kinetics in low-alloy 30CrMnSi structural steel using dilatometric and calculative methods was carried out. At the initial stage the evolution curve of shear transformation according to the Koistinen–Marburger (K–M) model corresponds well to the experimental dilatometric data, but with further temperature decrease the mathematical modeling causes a significant error in determining the volume fraction of the formed martensite. At the same time, the error in the calculations of the martensitic phase amount can reach 20 vol.%. The proposed method, which takes into account the temperatures of the beginning and completion of the shear transformation of austenite, allowed obtaining a closer correlation with the dilatometric data of 30CrMnSi steel compared to the Koistinen–Marburger model. The obtained results can be used to improve the existing modes of heat treatment, including interrupted quenching, to increase the accuracy of predictive determination of phase composition in low-alloyed structural steels.