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
Podolsky 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
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;
Safronova Elena Alexandrovna, engineer, Institute named after Z.I. Nekrasov of the NAS of Ukraine, Academican Starodubova square, 1, Dnipro, Ukraine, 49107; ORSID 0000-0002-4032-4275

Comparative analysis of methods of heat treatment of railway rails
and determination of further directions of increasing their operational reliability

Summary. The analysis of normative and technical documentation is
carried out, the characteristics influencing on wear resistance of railway rails
are established, various modes of thermal treatment are considered. The results
of measuring the hardness of the hot-rolled full-profile rail, made of steel,
which is classified as steel of the K76F brand in accordance with the regulatory
and technical documentation are given. The hardness of this rail corresponds to
the strength class R260 or NT260 according to EN 13674: 1-2011 and GOST R
51685-2013 respectively, that is, from unalloyed steel without thermal
hardening, intended for the production of turnouts and underground. On the
basis of comparative analysis of various ways and modes of railway rail
handling, further directions of increasing operational reliability are established
by means of working out methods of heating, cooling. The microstructure of
the experimental steel of the PCT after the furnace heating with cooling in
various cooling media was studied: Calm air (20C/s), fan (3.40C/s), compressor
(5.10C/s), water at a temperature of 800C (750C/s). It is established that at
cooling rate 5.10C/s we obtain an even structure of highly dispersed perlite with
220
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hardness at the level of requirements of foreign standards. On the basis of
technical sources and actual data it is established that volumetric heating with
subsequent immersion of investigated samples from the steel of the PCT into an
environment with a controlled cooling rate of ≈6.00C / s contributes to the
passage of the zone of transformation of austenite into perlite α → γ with the
reception of the structure of the perlite, as well as reaching a hardness of
415HB at a depth of 20 mm. It is shown that the use of furnace heating leads to
the complete diffusion process, in which the concentration of carbon and other
alloying elements is equalized throughout the volume of samples studied. The
possible directions of increasing the mechanical properties of rails to obtain an
even structure along the entire section of the rail head and to obtain hardness,
which is regulated by foreign standards, are shown.
Key words: railway rail, heat treatment, cooling rate, hardness,
microstructure
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