Purpose. The work is directed at elaboration of softening effect of carbon steel of a railway wheel after the speed-up cooling to the different temperatures. Methodology. Material for the research was carbon steel of a disk railway wheel with content of 0,57 % C, 0,65 % Si, 0,45 % Mn, 0,0029 % S, 0,014 % P, 0,11 % Cr. Specimens as plates 3 mm thick were exposed to heating up to the temperatures higher than Ac3, the subsequent speed-up cooling was halted after achieving certain temperatures (200 - 450 °C). A structure was studied with the use of electronic and light microscopes. The estimation of degree of the structure defect after the speed-up cooling was carried out with the use of method of x-ray analysis. The strength and yield stresses of carbon steel were determined under tension. Speed of deformation at mechanical tests was 10^-3 s^-1. The microhardness of structural constituents of steel was estimated using the apparatus a PMT-3 type. Findings. The research results of the structural state and properties of carbon steel of a railway wheel are presented depending on the temperature of self-tempering after the irregular cooling. Within the investigated temperature interval of self-tempering, permanent soften character of carbon steel with growth of the temperature of completion of the forced cooling of wheel is conditioned by the correlation of qualitatively different processes structural transformations. Originality. The net effect of softening the metal by reducing the degree of supersaturation of solid solution, reducing the dislocation density and coalescence of cementite particles exceeds the strengthening due to the presence of fine carbide particles in the structure. Practical value. According to studies it is determined that in order to increase fracture toughness, the discrolled railway wheel can be subjected to accelerated cooling to temperatures of 300 - 350 °C without substantial metal embrittlement.

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• Вакуленко Ігор Олексійович (1949–) (технічні науки)

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