International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

This work is devoted to the development and research of a new technology for processing bar scrap from 40X steel to obtain high-quality finished metal products in the form of a screw reinforcement profile. The developed technology included two stages. At the first stage, the round-section bar scrap is formed on a radial-shear rolling mill to obtain conventional bars of the desired diameter and create initial conditions for the formation of an ultrafine grained gradient structure in the resulting screw profile. The second stage is the direct production of a screw profile with a gradient ultrafine-grained structure on a combined installation. Metallographic studies have shown that after the implementation of the second stage of obtaining a screw reinforcement profile, a gradient structure is observed in 40X steel, with equiaxed grains, the size of which lies within 1.2-1.4 μm in the peripheral region and to a greater extent with elongated, directional-oriented grains in the central region of the resulting reinforcement.

This work is devoted to the study of a new technology for processing bar scrap – a precision shaft made of Cf53 structural steel (DIN 17212) that has proven its service life and produces high-quality finished metal products in the form of a screw reinforcement profile. The precision shaft used for recycling of its proven service life included two stages: preliminary deformation of the shaft on a radial shear rolling mill to obtain rods of the required diameter and create initial conditions for the formation of a gradient ultrafine-grained structure in the resulting screw profile; direct production of a screw profile with a gradient ultrafine-grained structure on a combined installation. The conducted research has shown that the new combined technological process of rolling bar scrap is feasible in practice and makes it possible to obtain a high-quality finished product from this scrap in the form of a screw reinforcement profile with a gradient ultrafine-grained structure.

The paper briefly discusses the main features of radial-shear rolling and provides an overview of its effect on the formation of an ultrafine-grained structure in various non-ferrous and ferrous metals and alloys. The conducted review showed that radial-shear rolling is the most promising way to form an ultrafine-grained structure in long bars made of both non-ferrous and ferrous metals and alloys, as well as from various composite materials.

In this paper, bars from carbon steel grade 45 deformed by a new technology are studied. This technology consists in drawing bars from medium carbon steel on a radial-shift rolling mill and subsequent drawing. As a result of deformation, bars with gradient microstructure were obtained. The surface zone of the bar is significantly crushed, the average ferrite size is 0.5 μm. In the neutral zone the deformation is not large enough, so the structure is not so strongly crushed, the ferrite grains are reduced to 2 microns. In the central zone, the microstructure consists of large grains with an average size of 7 μm. The quantitative ratio of large-angle boundaries in the surface zone is much higher than the central zone. To understand the relationship between strength and microstructure, the microhardness of the bar was determined. Thus for three deformation cycles the average value of microhardness in the central zone was 2085 MPa, in the neutral zone – 2505 MPa, and in the surface zone – 2915 MPa. As it can be seen, the hardness decreases as we move away from the surface zone to the central zone, this can be explained in terms of dislocation and boundary hardening.

One of the effective ways to control the properties of copper is to refine its structure to a nano- or ultrafine-grained level, and primarily with the help of severe plastic deformation. At the same time, radial-shear rolling is one of the promising methods for obtaining long-length rods with a gradient ultra-fine-grained structure. It is known from a number of scientific works that one of the main factors influencing the possibility of obtaining an ultrafine-grained structure in various ferrous and non-ferrous metals and alloys is the deformation temperature of these metals and alloys. The aim of the work is to study the influence of the deformation temperature at the radial-shear rolling mill on the microstructure evolution of copper. The following deformation temperatures of copper rods were selected for the planned studies: 20°C, 100°C and 200°C. The conducted studies have shown that the implementation of radial-shear rolling at ambient temperature compared with rolling at temperatures of 100°C and 200°C made it possible to achieve more intensive refinement of the initial structure. And first of all, this is due to the fact that with radial-shear rolling of copper, realized at ambient temperature, there are no dynamic return processes.

One of the effective ways to control the properties of copper is to refine its structure to a nano- or ultrafine-grained level, and primarily with the help of severe plastic deformation. At the same time, radial-shear rolling is one of the promising methods for obtaining long-length rods with a gradient ultra-fine-grained structure. It is known from a number of scientific works that one of the main factors influencing the possibility of obtaining an ultrafine-grained structure in various ferrous and non-ferrous metals and alloys is the deformation temperature of these metals and alloys. The aim of the work is to study the influence of the deformation temperature at the radial-shear rolling mill on the microstructure evolution of copper. The following deformation temperatures of copper rods were selected for the planned studies: 20°C, 100°C and 200°C. The conducted studies have shown that the implementation of radial-shear rolling at ambient temperature compared with rolling at temperatures of 100°C and 200°C made it possible to achieve more intensive refinement of the initial structure. And first of all, this is due to the fact that with radial-shear rolling of copper, realized at ambient temperature, there are no dynamic return processes.

The work is devoted to experimental studies of the influence of radial shear rolling on the microstructure evolution of the VT-1 titanium alloy and its gradient distribution over the cross section, as well as changes in mechanical properties. In the course of the conducted studies, two different types of microstructure were obtained. At the periphery of the bar near the surface, a relatively equiaxed ultrafine-grained structure with a grain size of 300-600 nm was obtained, while in the axial zone of the bar, an oriented striped texture was obtained. The resulting structure difference of the peripheral and central zones indicates the gradient nature of the structure distribution. This type of distribution is confirmed by the results of the microhardness study over the cross section of a bar rolled to a diameter of 15 mm. The ultimate strength after deformation increased by 58%, while the elongation decreased by 15%.

This work is devoted to the study of the use of radial-shear rolling mills for recycling bar scrap and some metal products from ferrous and non-ferrous metals that have served their service life to obtain a ready-made commercial product. In particular, the paper presents the results of computer modeling and experimental research of the process of scrap metal rolling in the form of rebar on a radialshear rolling mill into a round cross-section bar, which prove that some metal products that have served their service life after recycling using the proposed technology into finished commercial products in the form of bars can find further use without remelting.

In this paper the results of modelling of radial-shear rolling process of austenitic stainless steel AISI-321 are presented. The simulation in Simufact Forming program complex was performed. The conditions of simulation for radial-shear mill SVP-08 of Rudny industrial Institute were adopted. The various parameters of stress-strain state (effective plastic strain, effective stress, mean normal stress and Lode-Nadai coefficient) and also microstructure evolution with rolling force were considered. It is revealed that radial-shear rolling is an effective process for obtaining of high quality round billets from stainless steels of austenitic class.