Статті КПММ

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Browsing Статті КПММ by Subject "accelerated cooling"

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    Structural Changes during Thermal Strengthening of the Railway Wheel
    (National University Zaporizhzhia Polytechnic, Zaporizhzhia, 2024) Vakulenko, Ihor O.; Plitchenko, Serhii O.; Gubarev, S.; Khlebnikov, A.
    ENG: Purpose. Justification of mechanism of the structure transformations in the carbon steel of the railway wheel during disk thermal strengthening. Research methods. The material for the study was carbon steel of a railway wheel with a content of 0.57 % C, 0.65 % Si, 0.45 % Mn, 0.0029 % S, 0.014 % P and 0.11 % Cr. The railway wheel was heated to temperatures higher than Ac3, kept at this temperature to complete austenite homogenization process, and disk was rapidly cooled to the specified temperature. Degree defectiveness structure of the metal after accelerated cooling was assessed using technique of X-ray structural analysis. Strength stress, yield stress and relative elongation of the carbon steel were determined at stretching at rate of deformation 10-3 s-1. Results. At accelerated cooling of the carbon steel, the sources of strengthening are the processes of blocking mobile dislocations due to the condensation of carbon atoms on them and dispersion strengthening from the formed particles of the carbide phase. At temperatures of termination of forced cooling of carbon steel above 300…350 °C, the reduction rate of strength properties is determined by the excess of total effect of softening from decomposition of the solid solution, acceleration of spheroidization and coalescence of cementite particles over the blocking of dislocations by carbon atoms and dispersion hardening. Scientific novelty. The level of strength and plasticity characteristics of carbon steel of the railway wheel disc, depending on the temperature end forced cooling, is determined by the ratio of the influence of degree super saturation of the solid solution and the dispersion strengthening by carbide phase. Practical value. For temperatures termination of accelerated cooling of 200…300 °C, degree of super saturation of the solid solution is the main factor that determines the level of strength and plasticity characteristics. When manufacturing an all-rolled railway wheel, the strength limit of the disc metal can be increased by accelerated cooling to the middle range of temperature.
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    Structure and Properties of the Steel Railway Wheel Disc After Forced Cooling
    (The Faculty of Transport The Silesian University of Technology, Katowice, Poland, 2018) Vakulenko, Igor A.; Grischenko, Nikolaji; Vakulenko, Leonid I.; Efremenko, Vasily G.; Proiydak, Svetlana V.; Perkov, Oleg N.
    EN: The technological use of accelerated cooling makes it possible to improve the carbon steel properties of the all-rolled railway wheel disc. The properties’ complex depends on the temperature of the accelerated cooling termination. This is determined by the ratio of the carbon atoms emitted from the supersaturated solid solution to the crystal structure defects and dispersion strengthening from carbide phase particles. If the cooling stops at a temperature above 350°C, the decline rate of the strength properties increases. This is caused by the excessive softening effect of the solid solution breakdown and cementite spheroidization during the processes of dispersion hardening.