Theoretical Study of the Force Parameters of the ECAP-Linex Combined Process

The paper presents theoretical studies of a new deformation process combining the stages of equal-channel angular pressing (ECAP) and the Linex scheme. To analyse the resulting deformation forces, the stages of pressing in a matrix and compression by a chain conveyor are separately considered. Equations were provided for determining the forces acting on the drive pulley, ECA matrix, and chain element link. A trial calculation and comparative analysis with the previously known rolling-ECAP process showed that the new ECAP-Linex process allows for a stable deformation process with lower forces and a smaller channel junction angle in the matrix. The values obtained by equations are verified with computer simulation using the finite element method in the Deform program. A comparison of values showed that the force values in the calculation and simulation have a high level of convergence. For all three considered parameters, the difference value did not exceed 3%

Theoretical Study of the Force Parameters of the ECAP-Linex Combined Process

The paper presents theoretical studies of a new deformation process combining the stages of equal-channel angular pressing (ECAP) and the Linex scheme. To analyse the resulting deformation forces, the stages of pressing in a matrix and compression by a chain conveyor are separately considered. Equations were provided for determining the forces acting on the drive pulley, ECA matrix, and chain element link. A trial calculation and comparative analysis with the previously known rolling-ECAP process showed that the new ECAP-Linex process allows for a stable deformation process with lower forces and a smaller channel junction angle in the matrix. The values obtained by equations are verified with computer simulation using the finite element method in the Deform program. A comparison of values showed that the force values in the calculation and simulation have a high level of convergence. For all three considered parameters, the difference value did not exceed 3%

EFFECTIVE TECHNOLOGIES OF SEVERE PLASTIC DEFORMATION

Creation of new structural materials with new unique properties of metal remains one of the urgent tasks of modern materials science. In practice, it is possible to improve the properties of existing structural materials by grinding their structure to an ultra-fine-grained state. At the moment, one of the promising ways to obtain an ultra-fine-grained structure is the severe plastic deformation method (SPD). Most of the currently existing methods of implementation of the SPD have not been used in the real industrial sector due to the existing in this method of deformation of the disadvantage, which is the discreteness, i.e. the inability to process products of relatively long length and the need for a large number of processing cycles. And this determines the economic inexpediency of the introduction of this method in production. To solve the problem of introduction of the technology of production of ultra-fine-grained materials by SPD methods, we have developed a number of combined technologies of deformation, allowing to obtain rods of rectangular and circular cross-section of ferrous and non-ferrous metals with ultra-fine-grained structure. These processes include the following combined methods: "rolling-ECAP", “ECAP-drawing” "screw rolling-ECAP". As a result of numerous laboratory studies, to study the effect of the proposed methods of deformation on the microstructure evolution of various structural materials and change their properties, it was proved that the combined processes "rolling-ECAP" and "screw rolling – ECAP" have undeniable advantages over conventional equal-channel angular pressing, both in terms of more intensive grinding of grain and higher mechanical characteristics of the deformable metal in one cycle of deformation, and in terms of the possibility of obtaining long blanks

New approaches to the development of construction technologies

The paper presents data on the volume of materials consumed by builders and the carbon dioxide emissions that occur during this process. The reasons for the formation and volume of construction debris are considered. Recycling technologies currently used in the demolition of buildings are associated with crushing. The resulting concrete mix is used only for filling low-level earthworks due to the rapid carbonation of concrete surfaces. The scrap metal formed during crushing is used for remelting, polluting the atmosphere and requiring a large amount of energy. It is proved that due to the low economic and environmental efficiency, this method of recycling is a dead end. Studies have found that the constant increase in the strength of concrete and the absence of a decrease in the strength characteristics of reinforcing steels, stone materials, bricks, which are operated for a long time in favorable temperature and humidity conditions, allows them to be reused. General approaches have been developed that require changes in the existing technologies for the renovation of urban areas, the demolition of individual buildings and structures that currently exist. To reduce CO2 emissions and construction debris, it is enough to increase the volume of gentrification, reconstruction, major repairs, and re-profiling of the existing residential and industrial stock. When demolishing buildings, it is necessary to abandon the method of collapse of building structures with their further fragmentation. The method of piecemeal dismantling with repeated use of materials, products and structures (after determining their strength indicators by specialists), allows you to dramatically reduce the problems of construction debris and carbon dioxide emissions

Study of changes in microstructure and metal interface Cu/Al during bimetallic construction wire straining

This article investigates the effect of a new processing technology on the change in microstructure and mechanical properties of bimetallic aluminum-copper wire. This technology makes it possible to produce a new generation of wire for use in the construction of new overhead lines and reconstruction of old ones. The study was conducted using a transmission electron microscope, EBSD analysis, tensile tests, and determination of microhardness and electrical conductivity. The results of the study show that an ultrafine-grained copper-aluminum composite with a gradient structure is formed during straining by ECAP-drawing. Annealing after straining at 200 °C increases the strength of the interfacial connection between Cu and Al and improves the strength characteristics of the bimetallic aluminum-copper wire. The use of such aluminum-copper wires for overhead transmission lines allows to reduce the wire cross-section and, accordingly, wind loads, as well as to increase the strength properties without an additional increase in the total weight of the wire

Improvement of strength and performance properties of copper wire during severe plastic deformation and drawing process

The paper studies the evolution of microstructure and mechanical properties of copper wire during a new combined straining process. The main point of the technological process is to strain the wire in a rotating equal-channel step die and subsequent drawing. The die rotates around the wire axis and thereby creates tension due to equal-channel angular pulling and twisting in the die. Transmission electron microscopy and EBSD analysis, as well as tensile testing and microhardness determination investigated the strained copper wire. Ultra-fine grain gradient microstructure with a high component of high-angle grain boundaries was obtained as a result of straining. The tensile strength of the strained copper wire compared to the unstrained one increases more than twice from 302 to 635 MPa, and the yield strength increases from 196 to 406 MPa. The use of such hardened copper wire in construction will reduce the weight of the structure due to the reduction of diameter

Effect of thermomechanical processing of building stainless wire to increase its durability

A traditional use of high cumulative reduction ratios is not effective for manufacturing wire with high performance and mechanical properties, since cold plastic deformation reduces the wire diameter, while hot deformation has its own limitations. Thus, thermomechanical treatment of rolled steel has a huge potential to reduce costs and improve product quality when used in the construction industry. Such processing allows metalworking industries to increase the economic effect due to a more complete satisfaction of the requirements for the mechanical properties of finished rolled products. The article developed a new technology for thermomechanical processing of stainless steel wire, consisting of preliminary heat treatment to obtain an austenitic structure and traditional drawing followed by cryogenic cooling. As a result of such treatment, an ultrafine-grained structure was obtained, consisting of a mixture of austenite and α-martensite, with high strength and plastic properties. To analyze the features of the obtained microstructures, modern methods of metallographic analysis were used, such as scanning electron microscopy, transmission electron microscopy, and analysis of backscattered electron diffraction patterns. The microstructure is obtained after deformation at both temperatures and consists of a mixture of α-martensite and austenite. A structure with an average grain size of 0.5 µm was obtained by drawing using cryogenic cooling, and a microstructure of 1 µm was obtained at room temperature. The results obtained allow us to expect an increase in the performance and durability of stainless steel wire, which can be used for various purposes

Increasing strength and performance properties of bimetallic rods during severe plastic deformation

This study describes the evolution of the microstructure and mechanical properties of bimetallic aluminum-copper rods during straining by Equal channel angular pressing-drawing (ECAP-drawing). The study was conducted by means of a transmission electron microscope, EBSD analysis, tensile tests and determination of microhardness. The paper shows that an ultrafine-grained copper-aluminum composite with a gradient structure is formed during straining by ECAP-drawing. Microhardness of copper shell during 4 cycles of straining by ECAP-drawing increased from 57 to 165, and hardness of aluminum rod increased from 25 to 75 HV. This is associated with grain refinement and hardening of their boundaries by increasing the density of dislocations. Tensile test diagrams analysis has shown that straining leads to an increase in strength properties of bimetallic wire by 2 times, and as a result the plastic properties are also reduced by almost 2 times, but remain at a level applicable for further use. Application of such bimetallic rods in construction will allow reducing specific quantity of metal per structures without reduction of strength properties

Physico-Chemical Study of the Possibility of Utilization of Coal Ash by Processing as Secondary Raw Materials to Obtain a Composite Cement Clinker

A significant amount of energy waste has accumulated in the world, in particular, large-tonnage fine ash from central heating stations (coal ash), which can negatively affect the natural environment and the health of the population. However, at the same time, due to its chemical composition, this waste can be disposed of by complex processing as a secondary mineral component, thus reducing the anthropogenic load on the natural environment. This article presents a physico-chemical study of coal ash for its further use as a secondary mineral component, in particular, a component of a raw mixture with limestone to produce a composite Portland cement clinker. Coal ash and limestone were subjected to granulometric, chemical, differential thermal, scanning electron microscopy, elemental chemical and X-ray structural analyses, as well as modeling to assess the possibility of optimizing the raw material and mineralogical composition of the composite Portland cement clinker. During the research, the chemical and elemental compositions of the coal ash and limestone were determined and SEM images of the coal ash were obtained; it was found that 68.04% of the coal ash was represented by the fraction with granules <0.16 mm. Using X-ray diffraction analysis, the main limestone minerals were identified, which were represented by calcite and silica. Based on the results of mathematical modeling of the utilization of coal ash from a thermal power plant by processing with limestone, a two-component raw material mixture containing 23.66% fly ash and 76.34% limestone was optimized and the optimal mineralogical composition of the composite Portland cement clinker was determined. Utilization of coal ash by processing as a secondary raw material can be carried out at almost any ash storage facility anywhere in the world, taking into account the chemical composition of the processed ash. It was found that the replacement of natural raw materials with man-made raw materials in the form of coal ash contributed to a reduction in fuel consumption for firing (kg of conventional fuel) by 13.76% and a decrease in the thermal effect of clinker formation by 5.063%