ДО ПИТАННЯ ПРО ВИЗНАЧЕННЯ ГРАНИЧНИХ УМОВ ПРОЦЕСУ ПРОКАТКИ-ВОЛОЧІННЯ У ЗДВОЄНИХ РОЛИКОВИХ ВОЛОКАХ

Abstract

There is a great demand in the world for steel strip profiles, which are widely used in mechanical engineering, instrument making and other sectors of the national economy. In Ukraine, the production of strip profiles is extremely limited. The production volumes of such products, if a wide range of sizes and brands are required, are relatively small. The creation of large specialized enterprises for the production of strip profiles in these conditions is economically unprofitable, the orientation towards the import of these profiles makes the economic and technological security of Ukraine dependent on foreign suppliers. For the production of high-precision profiles, various combinations of basic shaping and auxiliary processes are used, depending not only on the characteristics of the profile itself and the technical requirements of the supply, but also on the size of the ordered batch and the capabilities of the available equipment. This explains the high complexity of technological design. The aim of the work is to determine the boundary conditions of deformation in double roller dies, which ensure a stable flow of the drawing process according to the criterion of the safety factor of the deformed metal. It was found that when calculating the transitions of drawing strip profiles during deformation of the initial round billet with a diameter of 3.67 mm from steel St.70 with a width to thickness ratio of more than two, the maximum value of the relative reduction per transition should not exceed 40-50 % during deformation without counter tension, and 40 % – with tension. Analytical studies have shown that in the range of working reductions per transition (5-40 %), the safety factor that guarantees the process of metal deformation without breakage and does not allow local constrictions and distortion of the profile geometry is not exhausted. It was found that in the range of working reductions per transition (5-40 %), the deformation process of the initial round billet in a roller die with smooth rollers proceeds without exceeding the permissible values of the drawing forces. It has been determined that with an increase in the relative reduction in the first roller die, the range of working reductions in the second roller die, which affects the stability of the metal drawing process, decreases.