25 ISSN 2409-9066. Sci. innov. 2021. 17 (4) https://doi.org/10.15407/scine17.04.025 BABACHENKO O. I. 1 (https://orcid.org/0000-0003-4710-0343) , KONONENKO, G. A. 1 (https://orcid.org/0000-0001-7446-4105) , and PODOLSKYI, R. V. 1, 2 (https://orcid.org/0000-0002-0288-0641) 1 Iron and Steel Institute of Z.I. Nekrasov, the NAS of Ukraine, 1, Sq. Ak. Starodubova, Dnipro, 49107, Ukraine, + 380 56 790 0514, okc.testcenter@ukr.net 2 National Metallurgical Academy of Ukraine, 4 ,Gagarina Ave., Dnipro, 49000, Ukraine, +380 56 713 5951, kaf.tom@metal.nmetau.edu.ua DEVELOPMENT OF A MODEL FOR CALCULATING CHANGES IN K76F RAIL STEEL TEMPERATURE TO DETERMINE THE HEAT TREATMENT PARAMETERS C i t a t i o n : Babachenko, O. I., Kononenko, G. А., and Podolskyi, R. V. Development of a Model for Calculating Changes in K76F Rail Steel Temperature to Determine the Heat Treatment Parameters. Sci. innov. 2021. V. 17, no. 4. P. 25—32. https://doi.org/10.15407/scine17.04.025 Introduction. The conditions of operation of the railways of Ukraine and the prospects for their entry into the international system of transport corridors require the development and modernization of railway tracks, inclu ding rails. Problem Statement. Given the necessity to ensure the main operational parameter of the rails (wear resistan ce), regulatory and technical documents standardize hardness. The most progressive European standard EN 1367412011 establishes that the hardness of the rail head at a depth of 20 mm shall be, at least, 321 HB, while DSTU 4344:2004 requires, at least, 321 HB at a depth of 11 mm. At the same time, according to EN 136741 2011, the rail surface hardness without the formation of needle structures shall be, at least, 405 HB. Purpose. To determine the possibility of achieving hardness without needle structures for rail head made of steel 0,80% C, 0,25% Si, 0,97% Mn, 0,055% V (hereinafter referred to as K76F), which complies with the world requirements, based on the calcination experiment and calculations with the use of the model; to determine the rational cooling rate for K76F steel during heat treatment. Materials and Мethods. K76F rail steel with 0.80% C, 0.25% Si, 0.97% Mn, 0.055% V. Techniques: metal lographic studies, hardness measurements, determination of calcination by end quenching, modeling by means of mathematical calculation with the use of QForm heat treatment software package. Results. The change in temperature, the formation of structure and hardness across the section of a K76F steel sample for calcination tests according to GOST5657 has been modeled. The changes in the hardness and micro structure has been experimentally established, depending on the distance to the heat sink surface; the cooling rate in the points where the hardness meets the requirements of EN 1367412011 for rails has been determined.