INFLUENCE OF THERMAL STRESSES ON THE FORMATION OF THE PLASTIC FLOW ZONE IN THE BEGINNING OF HOT FORGING OF CYLINDRICAL WORKPIECE

The article presents the solution of the problem of plastic flow
modeling in the initial stage of hot drawing of a cylindrical workpiece in a forging press with combined strikers. The intensity stress fi eld for the tensor of total elastic stresses (load and thermal ones) has been received. The stress load has solved the problem of plane deformation for a workpiece of a circular cross section to which three lumped linear efforts were attached. The zone of a plastic fl ow was determined by the value of the yield strength of the material as a limitation of the elastic stress intensity. It has been shown that the tensile thermal stresses involve a near-surface layer of the workpiece into a zone of a plastic fl ow; that facilitates the process of forging. The numerical example of the formation of stress loads and thermal stresses during drawing after roughing-up of 7-ton ingot of 40KhN steel with the radius of average cross-section R = 0.35 m; its bottom (880 °C) boundary of the admissible
forging temperatures was reached in 20 minutes after removal from the furnace with a temperature of 1180 °С has been considered. The graphs of the component distribution of the tensor of stress loads and thermal stresses have been introduced, as well as the respective intensities of stresses in the cross-section of the workpiece.

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