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

In this article, a number of theoretical studies have been conducted on a new combined process of multicycle thermomechanical processing, including wire drawing and subsequent cooling in liquid nitrogen. When analyzing the deformation, it was found that the presence of intermediate heating to ambient temperature allows calculating the force according to the Krasilshchikov formula and the wellknown nomogram of the tensile strength of AISI-316 steel at 20°C with minimal errors. The lack of heating leads to the fact that the second and third drawing cycles take place at partially negative temperatures in the workpiece section. This leads to an increase in the difference in the force values obtained by calculation and during modeling. To be able to use the Krasilshchikov formula and the nomogram of the tensile strength of AISI-316 steel at 20°C, it is necessary to adjust the resulting force values by increasing by about 30% for a diameter of 6 mm and 20% for a diameter of 9 mm in the absence of heating of the workpiece and by 35% for a diameter of 6 mm and 25% for a diameter of 9 mm in in case of preheating the workpiece.

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.

The paper studies the evolution of microstructure and mechanical properties of copper wire during a new combined deformation process. The essence of the technological process is deformation of wire in a rotating equal-channel step matrix and subsequent drawing. The matrix rotates around the wire axis and thereby creates stress due to equal-channel angular drawing and twisting in the matrix. The deformed copper wire was investigated by transmission electron microscopy and EBSD analysis, as well as tensile tests and microhardness determination. The deformation resulted in an ultrafine-grained gradient microstructure having a high component of high-angle grain
boundaries. The tensile strength of the deformed copper wire compared to the undeformed one increases more than twice from 302 to 635 MPa, and the yield strength increases from 196 to 306 MPa, an increase of 56%. The use of such hardened copper wire in construction will reduce the weight of the structure by reducing the diameter.

The results of finite element modeling of a new method with an increased metal processing level were considered. The improvement of the drawing process was achieved by changing the usual scheme of metal movement during deformation, which made it possible to achieve large strains compared to the standard drawing scheme. It is established that step drawing has the advantage of an increased processing level, but it leads to the formation of an inhomogeneous gradient strain.