The current paper studies the kinetics features of supercooled austenite decomposition in the pearlite temperature range (600-500 C) in chromiummanganese cast iron with the content of 2.2% carbon, 12.63% chromium, 5.7% manganese. The structure formation, phase composition, hardness as well as the distribution of elements between the phases and the structural constituents of the above-mentioned cast iron after isothermal soaking are investigated. The average size of secondary carbides after isothermal soaking is determined using JMicroVision v.1.2.7 free software.