Stress-Strain State of the Metal at the Initial Stage of Railway Rail Rolling

Abstract: In this paper, we determine the distribution features of the Cockcroft–Latham criterion over the cross section of the roll for calibers of various shapes based on formation process studies of stress-strain metal during railway-rail rolling in roughing stands of a universal rail-and-beam mill that were performed using the DEFORM-3D software package. An extremely uneven distribution of the Cockcroft–Latham criterion over the roll section was established. According to the data obtained in the axial zone, the values of the specified criterion are minimal. In the near-surface layers, the greatest value of the Cockcroft–Latham criterion and, accordingly, the highest probability of the defect formation occurs near the vertical axis of the calibers. In calibers of complex shape (“trapezoid”, “recumbent trapezoid”, and rail calibers), the presence of local zones with the maximal value of the Cockcroft–Latham criterion that are located in the places of formation of the foot of the rail profile. For rolling in a trapezium-type caliber, the presence of such an area is characteristic also in the near-surface zone near the vertical axis of the caliber. When determining the formation features of the stress-strain state of the metal at the initial stage of rail rolling, a direct relation between the uneven temperature distribution over the cross section of the roll and the values (maximal and average over the cross section) of the Cockcroft–Latham criterion was established. In this case, the uneven temperature distribution over the cross section of the roll was shown to increase in the coefficients of extracts along the passes and in the frequency of tilting, regardless of the shape of the used calibers. For calibers of complex shape, in addition to the listed parameters, an increase in the similarity of the shape of the rolled stock and the used caliber was found to have a significant effect on reducing the temperature inhomogeneity as well. A new rolling mode of railroad rails was developed based on the results of the theoretical studies. Its pilot testing under the conditions of the universal rail-and-beam mill of JSC EVRAZ-JWSMP showed a decrease in the rejection of rails by 0.78% compared to the previously used rolling mode. © 2021, Allerton Press, Inc.