Power conditions of rolling in universal calibers of modern rail-beam mills

Development of rolling stock, increase in the speed of transportation, load-bearing capacity of highways and their length requires constant improvement of the production technology for railway rails. Modern rail-beam mills have in their composition a continuously reversible group of stands, which includes universal stands. Rolling of rail profiles in universal calibers is radically different from rolling in two-roll calibers, and at the moment is not well studied, both theoretically and practically. The article defines the conditions for feasibility of the rolling process in universal calibers with a pair of non-drive rolls, taking into account the values of active (reserve friction forces) acting from the drive rolls and reactive forces from the non-drive rolls and roller fittings. The energy balance method solves the problem of determining the back-up force required for deformation in non-drive rolls. When solving the equation of equilibrium of forces in the deformation center formed by the drive rolls, the reserve of friction forces is defined, the magnitude of which largely determines the possibility of the rolling process. Theoretical dependences are obtained for estimating the power balance during rolling in universal calibers of modern rail-beam mills, taking into account the reserve of friction forces provided by the drive rolls and the support required for deformation in non-drive rolls. Information about the force conditions in a universal caliber is necessary to analyze the feasibility of the rolling process in it under various deformation modes and to clarify the drawing coefficients for elements of the resulting profile. Dependencies are proposed that allow estimating the consumption of the reserve of friction forces for the operation of roller fittings serviced by universal caliber. The well-known formula of A.I. Tselikov and A. I. Grishkov on the definition of broadening was clarified in relation to rolling in universal calibers with two non-drive rolls. The support from the non-drive rolls side effects the change in size of sole and head of the rail profiles.