Dependence of plastic deformation resistance of chromiumalloyed rail steels on the thermomechanical parameters of deformation (degree, speed, and temperature of deformation) and chemical composition of the steels under consideration was obtained by hot mechanical tests for torsion and compression. According to the obtained data, an increase in rate and a decrease in deformation temperature cause an increase in resistance to plastic deformation. Effect of relative deformation on resistance to

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... stic deformation is nonlinear with an expressed maximum at deformation degree of the order of 0.25. Analysis of influence of chemical composition of 76KhF, 76KhSF and 90KhAF rail steels and their resistance to plastic deformation was carried out using methods of multiple regression analysis. It has shown that increasing of content of carbon, manganese, vanadium, nitrogen, sulfur and phosphorus in the actual range of changes in their concentration leads to an increase in their plastic deformation resistance. Mechanism of this effect was revealed. Approximation of the obtained data allowed us to determine interval of changes in deformation resistance when chemical composition varies within the actual range of changes in elements content. Value of specified interval was up to 19 % of the absolute value of deformation resistance. When varying content of chemical elements in the interval specified in state standard for production of railway rails, value of deformation resistance interval was up to 30 %. Checking adequacy of the obtained dependences was performed by oscillographing the stands drives engines of rail mill of JSC "EVRAZ ZSMK" when rolling billets of different chemical composition. This checking made it possible to confirm the revealed patterns.