| Abstrakt: |
The analysis of domestic and global regulatory and technical documentation for railway rails shows that pre-eutectoid medium-carbon and high-carbon as well as post-eutectoid steels are used for the production of serial rails in world practice. According to the degree of alloying, both carbon and microalloyed, alloyed alloys are used. Thus, the issue of developing railway rails of a new generation with the use of boron microalloying and the effect of heattreatment regimes on the structural component of steel to obtain a high complex of mechanical properties is an actual direction of research. Boron dissolved in the matrix increases the incubation period of the nucleation of a new phase, decreases the temperature of the beginning of ferrite formation, as a result, suppressing the decomposition of austenite by the diffusion mechanism. The goal of the work: the study of the microstructure and fine structure of finely dispersed pearlite in steels for high-strength rails with hardness at the level of world requirements. Samples of test steel, which were pre-deformed and heat-treated according to test regimes, which differed in terms of cooling from 0.52 to 5.1°C/s, are studied. Based on the results of xray phase analysis after heat treatment of the experimental steels, the presence of Fe3C, Mn7C3, and FeCr formation is revealed, which have maxima at the same angles as α-Fe (matrix). When comparing and analysing the obtained data, it is established that the formation of MnSi, CrMn is present in all experimental steels, thus, they do not have a significant effect on the mechanical properties. As established, during accelerated cooling from a temperature of 900°C followed by tempering at 200°C for 120 min in laboratory test steels, internal stresses are relieved. At the same time, the microstructure corresponds to a highly-dispersed pearlite that meets the requirements of foreign standards. Experimental rail steel with 0.90% С, 0.39% Si, 0.89%Mn, 0.09% Cr, 0.010% Mo, 00035% B, 0.0123% N and with an increased carbon content has the following mechanical properties: σв = 1295 MPa, σ0.2 = 816 MPa, δ5 = 9.8%, ψ = 11.4%, KCU = 17.25 J/cm², which meet the requirements of EN 13674:1-2011 (R400НТ). [ABSTRACT FROM AUTHOR] |
