Abstract

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 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.

Keywords

railway rail, heat treatment, cooling rate, hardness, microstructure

References

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