Pimanov V. Cold forging of hollow products made of low-plastic steels with differentiated backpressure

The thesis is devoted to research of the influence of differentiated backpressure (backpressure's magnitude increases proportionally to reduction of metal plasticity) on the laws of cold forging process of products with cavities, determination of final shapes and dimensions of cavities, determination of specific loads on the deforming tool and forging force, developing of engineering methods for calculating the parameters of extrusion of hollow products and reliable die tooling constructions. The work had set that obtaining of plasticity diagrams for low-plastic steels by stretching and stretching with torsion under the action of differentiated backpressure on a workpiece is possible to obtain by finite element method (FEM). The methodology of making was developed. Theoretical analysis of cold forging processes of cavities with constant diameter by spherical punch and axisymmetric cavities by stepped punch was carried out under the action of differential backpressure on the workpiece by the method of joint decision of the approximate differential equilibrium equations with the condition of plasticity and finite element method. Taking into account the friction, backpressure and strengthening the analytical dependence for determining the state of stress, specific stresses and deformation loads were obtained. Numerical simulation by FEM determined parameters of cold forging process with backpressure of axisymmetric cavities and cavities of complex shapes of workpieces made of steels P6M5 and 12ХН3А. The results had sufficient experimental and industrial verification and allowed to set new technological schemes, methodology of calculation and die tooling constructions which significantly increase the possibilities of cold forging of hollow products in direction of expansion of steels for cold forging and more complex geometrical shapes of workpieces.