Babachenko Alexander Ivanovich, Dr. Sci., (Engin.), Senior Research Scientist, Director, Iron and Steel Institute named after Z.I. Nekrasov of the NAS of Ukraine, Academican Starodubova square, 1, Dnipro, Ukraine, 49107; e-mail: a_babachenko@i.ua, ORCID 0000-0003-4710-0343

Kononenko Anna Andreevna, PhD (Engin.), Senior Researcher, Iron and Steel Institute named after Z.I. Nekrasov of the NAS of Ukraine, Academican Starodubova square, 1, Dnipro, Ukraine, 49107;  e-mail: perlit@ua.fm, a_kononenko@inbox.ru  ORCID 0000-0001-7446-4105; ORSID 0000-0001-7446-4105

Klemeshov Eugene Sergeevich, Researcher, Iron and Steel Institute named after Z.I. Nekrasov of the NAS of Ukraine, Academican Starodubova square, 1, Dnipro, Ukraine, 49107

Podolskyi Rostislav Vyacheslavovich, engineer, , Iron and Steel Institute named after Z.I. Nekrasov of the NAS of Ukraine, Academican Starodubova square, 1, Dnipro, Ukraine, 49107;ORSID 0000-0002-0288-0641

 

Determination of the maximum permissible cooling rate of railway wheel rims to form a homogeneous structure

 

Summarу. Compliance with the new more stringent requirements for railway wheels is possible only with an integrated approach to improving their production technology with a reasonable choice of heat treatment modes, taking into account the chemical composition of steel. The purpose of the study is the experimental and analytical determination of the maximum permissible cooling rate of the rolling surface and the minimum required cooling rate of the central sections of the rim of a railway wheel to achieve a high level of hardness of the ferrite-pearlite structure. The studies were carried out on steels of grades ER8 and ER7 according to EN 13262, grade 2 according to GOST 10791: 2016, steel of class C according to AAR M-107 / M-208. Based on the hardenability test (GOST 5657) by the end hardening method (according to the Jomeni method), the distance from the surface from which one-sided cooling was performed, where the hardness met the requirements of the normative documentation for wheels made of the steel under study, the distance where the formation of needle-like structures did not occur, was determined, including bainite and widmanstatt according to the results of metallographic studies and determination of hardness. Based on the results of temperature changes during the cooling process, the cooling rates were determined in places that met the specified conditions. In the work, modeling was applied in the QForm VX 8.2 software package, as a result, a model was developed for the adaptation of which the results of the experiment were used. The high convergence of the results of calculation and experiment was confirmed. At the same time, the model made it possible to obtain the instantaneous cooling rate in a form that is more consistent with the physical meaning of the process and to avoid the scatter of actual values associated with the discreteness of data recording. It was found that the instantaneous cooling rate changes during the continuous uniform supply of the coolant. In some cases, a significant slowdown in cooling was recorded, or even negative values of the instantaneous cooling rate. This is due to the release of the heat of phase transformation, which occurs during the decomposition of austenite by the diffusion mechanism. The developed model can be used to construct thermokinetic diagrams during continuous cooling and to develop recommendations for heat treatment modes to achieve the specified mechanical properties at a certain structural state.

Keywords: railway wheels, hardness, cooling rate, hardenability, modeling