Журнал «Вестник Южно-Уральского государственного университета. Серия „Металлургия“» основан в 2001 году. Основной целью журнала «Вестник ЮУрГУ. Серия „Металлургия“» является информирование научной и технической общественности о результатах исследований как южноуральских учёных-металлургов, так и коллег из других регионов Урала, России и мира в различных областях металлургической науки и технологии. Работы могут быть представлены в форме как обзорных, так и оригинальных статей, а также в форме кратких сообщений. Журнал выходит четыре раза в год. Все материалы публикуются бесплатно. И размещаются в открытом доступе в соответствии в лицензией Creative Commons «Attribution» (CC BY). Журнал «Вестник Южно-Уральского государственного университета. Серия „Металлургия“» включен в Перечень рецензируемых научных изданий, в которых должны быть опубликованы основные результаты диссертаций на соискание ученых степеней кандидата и доктора наук по следующим специальностям: 05.16.02 – Металлургия черных, цветных и редких металлов (технические науки); 05.16.04 – Литейное производство (технические науки); 05.16.05 – Обработка металлов давлением (технические науки)
FOCUSING THE LASER-SCANATOR MODULE OF THE SLM PRINTER USING AN OPTICAL CONTROL SYSTEM
Selective laser melting (SLM) is a promising technology for additive manufacturing of complex-shaped parts. Metal powder is used as a starting material, and a laser is used to melt and build up parts layer by lay-er. During the growth of parts, defects may occur that can only be detected after the manufactu¬ring process is completed using third-party equipment, but which have a strong impact on the quality of the parts. Therefore, methods of non-destructive in situ quality control of the product are being developed, e.g. optical methods. But the use of such tools is only possible when all machine components of the printer's SLM, on which the optical control (OCS) and feedback systems rely on, operate normally. This paper pre-sents a new technique for calibration laser-scanator systems using an optical tomography system, one of the optical control systems. Thus, a SLM printer equipped with OCS can become an automatically calibra-ting tool capable of operating with minimal involvement of a technologist.
Powder Metallurgy and Composite Materials
DEFORMATION HEATING CONSIDERATION WHEN SELECTING TEMPERATURE-SPEED MODES OF DEFORMATION FOR AMg6 ALLOY
The article presents the results of numerical and laboratory experiments on open-die forging of 20 mm di-ameter workpieces from a heating temperature of 20, 130, 260 and 390 °C. Simulation has shown that dur-ing cold open-die forging, the deformation heating can reach 90 °C, and during open-die forging from a temperature of 130 °C – 70 °C, which must be taken into account when selecting the temperature and speed conditions of deformation. During hot open-die forging (heating up to 260 °C), the deformation heating can reach 20–40 °C, which can be critical in terms of overburning and loss of plastic properties and corrosion resistance of finished products. Laboratory experimental studies on open-die for¬ging of workpieces heated to 20, 130 and 260 °C revealed better plasticity and deformability of the AMg6 alloy when heated to 130 °C. Metallographic analysis of deformed samples revealed that when heated to 260 °C, the microstruc-ture of the AMg6 grain undergoes recrystallization. Along with the recrystallized grains, traces of overburn-ing are observed in the structure. Along the grain boundaries, the pores form a virtually continuous network of intermetallic phases. Open-die forging of AMg6 alloy samples heated to 130 °C ensured preservation of the deformation texture and hardening from 86 to 133 HV1, while completely eliminating the formation of both external and internal cracks, pores and any signs of destruction. The deformation behavior of the AMg6 alloy at a heating temperature of the workpiece up to 130 °C, revealed in this study, indicates the prospects for conducting additional research on the study of changes in the microstructure and mechanical properties of this alloy during warm deformation.
Metal Forming. Technology and Equipment of Metal Forming
WORK AREAS OF THE TMK RESEARCH CENTER IN DEVELOPING TECHNOLOGIES AND EQUIPMENT FOR THE PRODUCTION OF SEAMLESS PIPES
This article presents an overview of the achievements of the Seamless Pipe Department of the TMK Re-search Center in the field of metal forming in the following areas: screw rolling, longitudinal rolling, draw-ing and pressing. Computer finite element modeling and digitalization of these processes is an integral part of the work. Most of the scientific developments are implemented in production at Russian pipe plants. This increases the competitive advantage and allows to master new types of pipe products and increase the technological sovereignty of the country.
INFLUENCE OF PIPE FORMING OPERATIONS ON FACTURE RESISTANCE PARAMETERS
The paper presents an analysis of the influence of pipe processing on fracture resistance (CTOD) parame-ters. Fracture resistance is an important indicator for assessing the strength of materials, especially in the case of metal structures subjected to long-term loads and impacts, such as high-pressure pipelines. The results of the analysis can be used to develop methods and technologies to improve the frac-ture resistance of pipelines. Further research in this area can be aimed at optimization of forming operations of pipe processing taking into account fracture resistance parameters.
NEURAL APPLICATION YOLO NETWORK FOR DEFECT DETECTION ON SEAMLESS RINGS
Currently, product quality control is the main focus for domestic enterprises. Timely product control allows to prevent potential losses, and also reduces the risk of claims from consumers. Unfortunately, due to the large volume of production and lack of qualified employees, not all domestic enterprises can provide one hundred percent product control. Foreign companies have long ago found a way out of this situation. Large enterprises such as “Porshe” and “BMW” use systems based on artificial intelligence to control products. For Russian enterprises, the introduction of artificial intelligence is relatively new, but popular direction. The purpose of the research is to study the possibilities of using neural networks to identify defective products. In the course of the study was studied AI.SEE technology, analyzed the production technology of seamless rings (highlighted the shortcomings of production), as well as the method of training neural network YOLO. Also, the following task was set and solved: to develop a model (based on computer vision) that will detect, and visualize the presence of a defect on seamless rings. The conducted research showed that the model trained on off-the-shelf YOLO scales can determine the presence of defects on ring forgings with a high accuracy of 80…90 %. But, it should be noted that, despite the high accuracy of defect detection, the model requires a number of modifications for more stable and qualitative work. The use of such a model can significantly improve the control processes in production. It is worth noting that the re-sults obtained can be useful for companies engaged in the production of rings, and contribute to improving the efficiency and reliability of production processes, for further implementation of such a system.
APPLICATION OF MATHEMATICAL MODELING IN THE DEVELOPMENT OF TECHNOLOGY FOR PROCESSING TECHNOGENIC RAW MATERIALS FOR ELECTRIC STEEL MELTING PRODUCTION
The production of steel in electric furnaces is a large-scale metallurgical production, which results in the formation of man-made waste – dust. This type of waste contains valuable metals (iron and zinc), which re-quires the development of technologies for its processing in order to extract valuable elements into inde-pendent products. When developing pyrometallurgical technology for processing dust, mathematical model-ing methods were used to analyze the physicochemical interactions of the charge components (dust and fluxes) during smelting in a ring furnace and select the optimal temperature regime and ratio of raw materi-als. The object of the research was samples of iron-zinc-containing dust from PJSC Magnitogorsk Iron and Steel Works. It has been shown that iron and zinc in dust are contained in the form of ZnO.Fe2O3, but most of the zinc is in the form of ZnO. The recovery process model was created using the Selector software package and is represented by 7 tanks simulating different zones of a ring furnace. 21 independent components (elements) were introduced into the model, corresponding to the chemical composition of raw materials, fluxes and air: Al, C, Ca, Fe, K, Mg, N, Na, P, S, Si, Ti, Mn, Cu, Pb, Ni, Cl, Cr, Zn, H, O. The results of laboratory studies confirmed the modeling data on the chemical composition of granulated cast iron and condensed zinc oxide and their extraction into these target products. A technologi-cal scheme for processing technogenic raw materials of electric furnace production was developed and pro-posed. The proposed technology will make it possible to use the resulting granulated cast iron as a substitute for metal scrap in the production of steel in electric furnaces, which meets the development strategy of the Russian ferrous metallurgy for the period 2014–2022 and for the future until 2030.
Металлургия чёрных, цветных и редких металлов
TO THE 70th ANNIVERSARY OF THE DEPARTMENT OF PROCESSES AND MACHINES FOR METAL FORMING (ROLLING). THE STATE AND PROSPECTS OF DEVELOPMENT OF THE ENERGY THEORY OF ROLLING
The theoretical basis for the development of new rolling processes at the Department of Processes and Ma-chines for Metal Forming is the energy theory. With its help, over the 70 years of the department's exist-ence, more than a dozen new technological processes of cold and hot sheet rolling, rolling of precise pro-files, including shaped ones, profiles from difficult-to-deform metals and alloys, wire, and pipes have been developed. At present, the energy theory of rolling is successfully applied outside the department, helping to solve new problems dictated by modern conditions.
IN MEMORY OF GENNADIY GEORGIEVICH MIKHAYLOV
PRODUCTION OF INTERMETALLIDE COMPOUND Fe3Al BY LAYER-BY-LAYER ELECTRIC ARC GROWTH METHOD
Currently, additive technologies for layer-by-layer electric arc growth are being used. The main vector of development in this area is associated with the use of aluminum alloys. In this work, an experimental technique was tested for producing the Fe3Al intermetallic compound by layer-by-layer electric arc growth with the simultaneous supply of two dissimilar solid-section welding wires with diameters of 1.2 mm into the electric arc combustion zone. Methods for producing intermetallic compounds and their disadvantages are analyzed. Electric arc growing modes have been determined. The result of the experiment was the production of an iron-based alloy with an aluminum content of 13–16 %. The grown samples were subjected to heat treatment, after which the Fe3Al intermetallic compound was obtained.
ABOUT ECONOMICAL CONTROL OF METAL HEATING IN BROACHING FURNACES AND UNITS IS CONSIDERED
The current problem of optimizing the control of metal heating in broaching furnaces and units is considered. Purpose of the study. Develop an algorithm for calculating the temperature distribution of the working space by zones, ensuring the implementation of a control principle that is economical in terms of fuel or electricity consumption for heating. Materials and methods. The previously established principle of economical heating control is discussed, its validity is emphasized, and its features are indicated. The essence of the principle is to adapt the temperature level of the working space in the zones to the characteristics of the heated metal and the productivity of the furnaces. Results. Variants of the algorithm have been developed that are applicable both for furnaces without a preheating zone and for furnaces with such a zone. The resulting temperature distribution across zones is characterized by the fact that the region of highest temperatures shifts, as far as possible from the point of view of heating quality, towards the end of the furnace. Typical graphs of the optimal temperature distribution by zone and a specific calculation of the mode for a three-zone horizontal broaching furnace (without a preheating zone) for heating steel wire are given. It is indicated that using the corresponding functional dependencies, the calculation procedure is also applicable for broaching thermal units with electric contact heating of the wire. The economic efficiency of the principle in the industrial operation of the corresponding control systems is noted. Recommendations are given for solving the problem of parametric identification of the heating model used as part of the algorithm. Conclusion. The developed algorithm can be used as part of the algorithmic support for automated control systems for heating metal in broaching furnaces and units.
Metallurgical Heat and Power Engineering
ROLLING OF PIPE FROM STEEL GRADE 08Х18Н10Т ON A TPA 70-270 WITH A TWO-ROLL MILL FOR SQUASHING AND ROLLING
The development of the production of seamless pipes from stainless steel grades for power engineering companies that supply integrated solutions for nuclear and thermal energy, gas and petrochemical industries is today one of the important areas of technology development for manufacturers of pipe products. And modern economic realities and external sanctions pressure on Russia make this task a priority. The use of screw rolling mills for the production of hot-rolled pipes from stainless steel grades is today the most promising direction, in comparison with the traditional method - pressing. This technology can significantly increase productivity, improve the quality of manufactured pipes and reduce the metal consumption coefficient. The use of mills with double piercing and calibration on screw rolling mills, without the use of longitudinal rolling mills implemented on the TPA 70-270 mill, is currently insufficiently studied and used in practice, since this mill is the only one in the Russian Federation. The main disadvantage of the technology for producing stainless steel pipes is the low wear resistance of rolling tools, in particular piercing mill mandrels. The high rate of tool wear does not ensure consistency of the required quality of the products. One of the promising methods for increasing tool wear resistance is the use of lubricants. Currently, the market demand for stainless steel seamless pipes is 55 thousand tons per year, of which imports account for about 20 thousand tons. Using modern technologies and production capabilities of pipe rolling tools, as well as introducing new technical solutions into the technological operations of pipe production, it is possible to increase the wear resistance of pipe rolling tools, ensure consistently high quality of produced pipes and increase competitiveness. This paper presents the results of the pilot development of rolling pipes made of steel grade 08Х18Н10Т on the TPA 70-270 mill, where the piercing of the workpiece and the rolling of the liner are carried out on the same screw rolling mill.
IMPROVEMENT OF TECHNOLOGY FOR RADIAL FORGING OF RECTANGULAR PROFILES
Based on experimental studies of radial forging on RKM SKK-14 in strikers with smooth working surfaces, offset on pairs of mutually perpendicular strikers relative to each other along the forging axis by an amount exceeding the length of the working surface of the striker, a refined dependence has been proposed for determining the diameter of the workpiece when obtaining rectangular profiles. A new method of radial forging of rectangular profiles is described, in which the production of rectangular profiles is carried out by one pair of strikers with convex ridges, and a second pair of strikers with a smooth working surface, over several deformation cycles with the workpiece rotated after each deformation cycle by an angle of π/2. The effectiveness of using this method, confirmed by industrial experiments, is shown by increasing the transverse deformation of the metal, which makes it possible to reduce the compression and the displaced volume of metal when forming rectangular profiles from round initial blanks. A description is given of another method of radial forging of rectangular profiles, which eliminates the operation of turning the workpiece after each deformation cycle, with almost the same efficiency as the first method, which has been proven by industrial experiments. The essence of this method is to use one pair of strikers, forming a wide edge of a rectangular strip, with a special chevron shape of the working surface, and another pair of strikers with a smooth working surface. The proposed new technical solution is described with the implementation of an additional section on the strikers of a radial forging machine, adjacent to the working surface of the striker and located cantilever to its supporting surface, ensuring the direction of the deformable workpiece along the forging axis at the time of its insertion into the strikers. All developed technical solutions are applied in practice.
DEVELOPMENT OF TECHNOLOGY AND MASTERING THE PRODUCTION OF PIPES WITH A DIAMETER OF 2520 mm
Strengthening coastlines in the Far North is a complex and technically difficult task. To minimize uncontrollable natural disasters and fairly severe weather conditions, as well as due to the large volumes of ports, the shoreline is strengthened with pipe sheet piles and piles with a diameter of 2520 mm. The products are in demand and have high margins. This assortment has not previously been produced on an industrial scale by PJSC TMK and in the Russian Federation in general. The only method that allows you to obtain the required workpiece is the JCOE method. This article describes the main stages of development of pipes with a diameter of 2520 mm. 1. Using modern engineering analysis methods based on the finite element method (FEM), the technical feasibility of pipe production was assessed, as well as the development of technological pipe bending and forming modes. 2. An analysis of the influence of mechanical properties on the geometric parameters of the finished product was carried out. A new technique for monitoring the geometry of a pipe blank during step forming with subsequent predictive analytics is proposed; Multiple regression equations have been obtained to evaluate the impact of changes in the controlled dimensions of the sheet blank during the step molding process. 3. Using modern CAD modeling packages, a new automated section for the assembly of workpieces was developed and designed. 4. A technological scheme for the production of pipes of a new range has been developed. 5. Experimental work on the production of pipes was carried out. The developed new method for producing pipes with a diameter of 2520 mm expanded the existing range of the enterprise, and also had positive economic efficiency due to the high marginal cost. The new production method has confirmed its efficiency and in practice (production of a pilot batch) has proven its feasibility.
INFLUENCE OF DYNAMIC CHANNEL-ANGLE PRESSING ON RELATIVE ENERGY OF GRAIN BOUNDARIES IN HAFNIUM BRONZE
The aim of the work is to evaluate the relative energy of grain boundaries of hafnium bronze deformed by dynamic channel-angle pressing (DCAP) using scanning tunneling microscopy. In the course of this work, the following studies were carried out. 1. The sample preparation technique of Cu-Hf samples subjected to severe plastic deformation (SPD) by DCUP for subsequent scanning tunneling microscopy studies was perfected, providing an averaged RMS surface roughness value of about 2 nm. 2. Scanning tunneling microscopy images of the hafnium bronze surface structure were obtained and processed using the Gwyddion application program. As a result, grain boundary profiles were calculated, on the basis of which the values of dihedral angles at the bottom of etching grooves were calculated and the relative energies of grain boundaries were calculated. 3. It was found that after deformation of DCUP, the average relative energy of grain boundaries is almost two times higher than the relative energy of grain boundaries of polycrystalline copper. Thus, nonequilibrium grain boundaries are formed in the samples as a result of DCUP. 4. It is shown that with the increase in the number of ACP passes there is an increase in the average relative energy of grain boundaries, which indicates an increase in the degree of their non-equilibrium.
THE ACTIVITY COEFFICIENTS OF THE NUCLEI COMPONENTS OF THE CHEMICAL REACTIONS PRODUCTS IN STEELMAKING PROCESSES
The chemical potentials of the nanoparticle components differ from the chemical potentials of the macro body components. Previously, the authors obtained a formula for its calculating based on the corresponding values in the bulk phases. The additional pressure in the nanophases and the dependence of the surface tension of the nanoparticle on its size were taken into account. This paper presents the results of research, based on the developed theory, on some aspects of the growth of non-metallic inclusions nuclei in steelmaking processes. It is shown that the surface effects play a fundamental role for particles smaller than 100 nm. The activity coefficients of the components of such particles can range from 0.001 to 600. A method for calculating them for growing nuclei of chemical reaction products in steel making process is proposed.
Physical Chemistry and Physics of Metallurgical Systems
CALCULATION OF THE CHEMICAL POTENTIALS OF NANOPARTICLES COMPONENTS
Simple and convenient expression for the calculation of the chemical potentials in isotropic condensed nanoparticles based on the corresponding value for the bulk phase has been obtained. In the first approximation, the dependence of surface tension on the particle size has been taken into account. For the recalculation, the surface tension and the molar volume of the corresponding bulk phase as a function of a composition should be set. Expression convenient to study composition changes during nanoparticle growth. The expression is useful for metallurgy (formation of nonmetallic inclusions), analytical chemistry (formation of precipitations), nanotechnology (formation of nanocrystals in amorphous metals), and other branches of science and technology. The proposed method can be easy generalized for anisotropic nanocrystals.
MODELING AND IDENTIFICATION OF THE COOLING AND SOLIDIFICATION PROCESS CONTINUOUSLY CAST SLAB BILLETS
Introduction. The problem of parametric identification of a mathematical model of the process of cooling and solidification of continuously cast slabs in the secondary cooling zone (SZZ) of continuous casting machines (CCMs) is considered. The relevance of the work is determined, first of all, by the fact that the quality of the product obtained in this way significantly depends on the operating mode of the air defense system. The technological process is quite complex, not fully studied and, as a result, still poorly managed. Purpose of the study. Develop a procedure for parametric identification of a model of the metal cooling and solidification process based on data available for direct measurement. Materials and methods. An analysis and synthesis of literature data on the problem was carried out. An acceptable structure of the mathematical model was determined, a criterion for the proximity of the object and the model was selected, and the problem of its parametric identification was posed and solved. Results. An acceptable formula has been determined to describe the real temperature field in the workpiece after the metal leaves the mold. A numerical study has established that the identification problem under consideration is solved stably and with almost any predetermined accuracy, and an increase in the number of surface temperature measurement points significantly increases the noise immunity of the solution. When describing external heat transfer in radiative-convective form, the identification problem was solved using a program that implements the coordinate descent method; the resulting one-dimensional minimization problems were solved using a subroutine using the golden section method. To numerically integrate the model equations, an implicit finite-difference scheme was used, which was solved by the sweep method. In the case where the external heat transfer of the workpiece is described only in convective form, a program using the golden section method has been developed and tested. The curves of changes over time of process variables calculated using the adjusted model are presented. Conclusion. A mathematical model tuned to the “real process” was used to identify the features of the metal cooling process in the production plant of the continuous casting plant of PJSC MMK; in particular, based on the results of the study, the coolant costs along the production line were adjusted.
PRODUCTION OF FOIL FROM LEAD AND TIN ALLOYS IN THE CONDITIONS OF SUSU AND RPA “R.O.S.Anticor“ LLC
Lead, tin and lead foil clad with tin are used in various branches of technology, medicine and the food industry. According to GOST 18394–2016, the thickness of the foil is in the range of 0.015–0.21 mm, and the width of the foil is 70–450 mm. The technology for manufacturing foil based on lead, tin and their alloys was developed quite a long time ago, in the 20s–30s of the last century. In the USSR and abroad in those years, due to the specific physical and mechanical properties of the rolled metals, cold rolling was used, implementing the roll and card rolling methods. The use of the roll or card rolling method at that time was determined, first of all, by the availability of appropriate equipment. Foil rolling was carried out on both reversible and non-reversible twin-roll rolling mills with work roll diameters of 230–700 mm. An analysis of the state of the technology and the equipment used for rolling foil made of lead, tin and lead foil clad with tin currently differs little from the technologies used in the USSR. In our opinion, this is explained by the small-tonnage orders, low yield (60–70 % of a strip billet 0.9 mm thick), low profitability and the disinterest of manufacturers in improving the technology. According to available information, the lead time for orders at some enterprises reaches up to 6 months. These shortcomings in meeting the demand for small-tonnage batches were noted in the Order of the Government of the Russian Federation No. 4260-R dated December 28, 2022. This paper presents the experience of manufacturing small-scale batches based on lead and tin in the conditions of RPA “R.O.S.Antiсor” LLC and SUSU. The research work carried out to develop the technology and test it for the conditions of the mentioned organizations made it possible to develop technological regulations for the production of foil and technical specifications for lead, tin and lead foil clad with tin.
RESOURCE-SAVING TECHNOLOGY FOR MANUFACTURING LEAD-FREE SOLDER BY EXTRUSION
Increasing legislative requirements in the field of environmental safety and limiting the use of lead in new electrical and electronic equipment increase the relevance and economic justification of the search for new low-temperature alloys for solder. This article develops a technology for producing leadfree solder rods and wires using the direct extrusion method. Using a mathematical model of direct extrusion and a computer program, the deformation and energy-force parameters of the manufacture of rods ⌀8.0 and ⌀15.0 mm and wire ⌀2.0 mm from the 52In–48Sn alloy were determined. According to the calculation results, the maximum extrusion forces in the manufacture of the specified assortment are 106 kN. This must be taken into account when selecting direct extrusion equipment. Simulation in the QForm package determined the temperature and speed conditions for the extrusion of rods and wire. It was revealed that technologically the extrusion process can be implemented in the analyzed modes for all standard sizes of products. The alloy is not heated above its melting point. There are also no reasons for loss of process stability and reduction in the quality of the finished product. Strength analysis of technological equipment for the production of rods and wires showed a safety margin of more than 2.1, which is considered sufficient for metallurgical equipment. Using the developed technology, a pilot batch of 100 kg of solder wire ⌀2.0 mm wound on coils and 150 kg of solder rod ⌀8.0 mm was manufactured for JSC Chelyabinsk Zinc Plant.
DEVELOPMENT AND COMMISSIONING OF A CROSS-CUTTING SITE FOR FORGINGS FROM SPECIAL STEEL AND ALLOYS, BUILT INTO A RADIAL FORGING TECHNOLOGICAL LINE
A technological section for transverse cutting of forgings produced on a radial forging machine SKK-14 from the Austrian company GFM has been developed, which has no analogues in the composition of the equipment, its layout and design. A new design of a valve ejector for forgings is proposed, the distinctive feature of which is its compact integration into the existing roller conveyor of a radial forging machine, as well as counter-directional rotation of the valve levers. To reduce the cutting force and heating costs, it is proposed to heat or preheat only part of the length of the forging at the place of its cutting using a specially designed induction heater. Taking into account the peculiarities of the hydraulic system of the P-6332 press and the requirements for cutting conditions on shears with parallel knives, an original design of a die for cutting forgings was developed, the distinctive features of which are the perception of axial cutting forces by the die columns during cutting, as well as the synchronization of the clamping and cutting mechanisms. Taking into account the execution of forgings using a P6332 hydraulic press with a developed upper cutting stamp, a special compact swinging drive roller table with a pressure roller has been developed, the swing axis of which is aligned with the axis of the roller table drive roller and is offset relative to the roller table center of gravity, ensuring the roller table returns to its previous position after tilting. To enable the movement of measured forgings and their storage, designs of a transport roller table, a lever ejector and storage pockets have been developed.
FEATURES OF DEFECTS WHEN ROLLING THIN STRAPS AND FOILS
The authors analyze the main causes of their formation and methods preventing the appearance of scrap. Correct selection of necessary modes of strip rolling is complicated due to the peculiarities of the rolled material with shape memory – nitinol. Titanium nickelide has the ability to attach gases (nitrogen, oxygen) and is subject to oxidation. The article deals with defects formed during rolling on multi-roll mills. Among them are double-sided corrugations, boxiness, bubbles, waviness, different thicknesses. The main negative factors that are sources of these defects can be counteracted by correct roll profiling (waviness), setting the right modes of compression (double-sided corrugation), reassembly of the main units of the mill (runout, boxiness). When rolling hard-to-machine materials, sliver texture should be analyzed to identify sources of defects. Rolling equipment adjustment should include not only rolling modes (speed, compression value, tension on coiler drums), but also work with working rolls, including high-precision surface treatment of barrels and necks.
METHODS FOR IMPROVING THE PRODUCTION OF SORBITIZED HIGH-CARBON WIRE ROD WITH THE PURPOSE OF OBTAINING A GUARANTEED COMPLEX OF PERFORMANCE PROPERTIES
The article discusses options for modernization of existing small-section mills. An analysis of the current technology for cooling rolled products at mill 170 of PJSC MMK was carried out. The results of research and development work in 2020–2021 are considered, which showed the advantage of those developed at MSTU rolling modes over the current modes at the mill.
INFLUENCE OF BORON AND COOLING RATE DURING SOLIDIFICATION ON THE CHEMICAL COMPOSITION OF STRUCTURAL COMPONENTS OF COMPLEX-ALLOYED WHITE CAST IRONS OF THE Fe–C–Cr–Mn–Ni–Ti SYSTEM
It is possible to improve the technological and operational properties of white high-chromium cast irons by changing the ratio of basic chemical elements in castings, complex alloying, micro alloying and modification, conditions of crystallization of metals in castings and heat treatment methods, which makes it possible to control the process of formation of structure and properties of metal in castings. Structure stability and heat and wear resistance depend on the type and morphology of carbides and the corresponding metal base, chemical composition of structural components that determine the protective properties of oxide layers, since the authors have shown that scale resistance is a structure-sensitive property. The study of the influence of boron and cooling modes in the casting mold on the distribution of chemical elements in the phases of cast irons of the Fe–C–Cr–Mn–Ni–Ti system, ensuring the stability of structure and operational properties at operating temperatures is an urgent task.
THE DISSOLUTION OF THE RARE-EARTH PHOSPHATES IN CARBONATE-ALKALINE MEDIA
The article is dedicated to the dissolution process of some rare-earth phosphates in carbonatealkaline media. The object of the study are model sediments of rare-earth phosphates. Different groups of the rare earth elements (REE) have been researched according to their masses: heavy-weight – holmium and ytterbium; medium-weight – samarium and gadolinium; light-weight – neodymium and yttrium though it does not belong to lanthanoids. REE-phosphates are impurity and taken place into technogenic waste phosphogypsum (PG). It is considered to be the PG has being be produced from 10 to 15 million tons per year. Because of the PG goes to disposal site, it causes ecological issues. For the rational use of natural raw materials, it is necessary to develop a solution that allows the phosphogypsum process into commercially valuable products. Concentrate of rare earth metals may be one of these. REE are widely used in various industries: defense, energy, electronics, metallurgy, catalysis and others. However, there are low-level production and incomplete production cycle in the several REE industry, this it is in need of import. Therefore, the study is aimed at achieving economic stability and technological sovereignty of the Russian Federation. The article demonstrates an illustration of the influence of temperature, concentration of carbonate solution, liquid to solid ratio and intensity of mixing on the REE-phosphates solubility. In the concentration range under consideration at a temperature of 90 °C, the maximum equilibrium degrees of extraction into solution were: E(Ho) = 75.6 %; E(Yb) = 85.5 %; E(Nd) = 62.5 %; E(Gd) = 71.6 %; E(Y) = 73.1 %; E(Sm) = 46.1 %. The results of this research are part of the thermodynamic analysis of the REEPO4 – K2CO3 system, which can subsequently be used to model the process of associated REE extraction from industrial waste (phosphogypsum, for example) by liquid carbonating conversion method.
NUMERICAL STUDY OF STRESS-STRAIN STATE OF AMG6 ALLOY DURING OPEN-DIE FORGING
The article presents studies of the stress-strain and temperature-velocity states of the AMg6 alloy during free-die forging. Numerical experiments on free-die forging of samples with a diameter of 15.0; 20.0; 25.0 and 30.0 mm were carried out in the QForm program. During the experimental studies, the free-die forging speed was 0.1, 0.5, 1 and 5 mm/s and the workpiece temperature was 20, 130, 260 and 390 °C. The research results showed that the side surface of the sample is a zone of maximum average stresses, and the periphery of the contact surface of the sample with the die is a zone of minimum average stresses during free-die forging. The maximum values of the shear stress intensity are located at the periph-ery of the contact surface of the sample with the die. The stress state indicator σ/T, which characterizes the minimum plasticity of the material being processed, during free-die forging takes on its maximum values on the side face of the sample and does not change its position with a change in heating temperature. An increase in the temperature of the sample during free-die forging leads to a decrease in the average stresses and the intensity of the tangential stresses, but the patterns of distribution of their maximum and minimum values remain unchanged when the temperature of the sample changes. Increasing the free-die forging speed from 0.1 to 5 mm/s leads to a slight increase in stress intensity by 15–20 MPa. Deformation heating significantly depends on the free-die forging speed and the initial temperature of the sample. The maximum deformation heating is localized in the central part of the sample. The deformation rate during free-die for¬ging at a rate of 5 mm/s does not exceed 1.1 s–1. The distribution of strain rates over the cross section is uneven. During the free-die forging process, first the maximum stresses arise in the center of the workpiece, then they increase and spread along the forging cross. When the degree of deformation is more than 50 %, the maximum values move to the periphery of the contact of the sample with the dies and remain there until the deformation is completed. Free-die forging forces are largely determined by the size of the sample, its heating temperature, hardening during cold deformation and slightly depend on the forging speed.
INFLUENCE OF CALCIUM-STRONTIUM CARBONATE AND COOLING CONDITIONS DURING SOLIDIFICATION ON STRUCTURE AND PROPERTIES OF COMPLEX-ALLOYED WHITE CAST IRONS OF Fe–C–Cr–Mn–Ni–Ti–Al–Nb SYSTEM
Under severe operating conditions, such as aggressive abrasives, high temperatures and harmful working environments, machine and equipment parts are favoured that are made mainly of white cast irons. The structure and the amount of carbide phase in these cast irons influence their mechanical properties and their ability to resist wear at elevated temperatures. White cast irons owe their particular wear resistance to the high content of primary MC carbides and eutectic carbides such as M7C3 in the mat¬rix, which is mainly composed of austenite or austenite and ferrite. There is a wide variety of technological methods that are designed to improve the special characteristics of cast irons, centred mainly on improving the structure of the materials. The most effective methods for improving the mechanical and special properties of foundry alloys are refining and complex modification. The heat resistance of cast iron is improved as a result of removal of harmful impurities from the melt and formation of refractory inclusions such as SrO and avail-able MgO, Al2O3, SiO2 in carbonate. These inclusions serve as crystallisation centres, which leads to melt supercooling and structure refinement. The modifying effect of carbonate is due to the formation of SrO oxide, these inclusions act as modifiers of the second kind. When cast iron is heated, an oxide film of stron-tium chromate (SrCrO4) is formed on the surface of castings, which has a higher density and better adhe-sion to the metal base than spinel oxide (FeO·Cr2O3). This results in better resistance to scale formation.
TO THE QUESTION OF STUDYING THE DISSOLUTION RATE OF ZINC FERRITE USING THE ROTATING DISK METHOD
Flotation processing of copper smelting slag results in the formation of flotation tailings containing approx-imately 0.5 % copper and 4 % zinc, which are present in primary and secondary mineral compounds. Ac-cumulated volumes of these wastes in Russia range from 120 to 140 million tons. Copper and zinc in the tailings are found in ferrites as separate mineral phases. This material can serve as a raw material for the extraction of copper and zinc. One of the components of this raw material, zinc ferrite, was investigated for its dissolution rate using the rotating disk method. To do this, zinc ferrite (ZnFe2O4) was synthesized using ceramic technology. The sample was characterized using X-ray diffraction analysis (XRD). The obtained ferrites were com-pressed into tablets and fixed in a Teflon holder for experiments. The kinetics of zinc ferrite dissolution in an aqueous solution of sulfuric acid were studied in the con-centration range of 7 to 300 g/dm3, at temperatures of 25, 45, and 65 °С (298, 318, and 338 K), and under hydrodynamic conditions. Activation energies were calculated using the Arrhenius equation, and experi-mental rate constants were determined. A conclusion was drawn regarding the kinetic regime of zinc ferrite dissolution.
PHYSICAL AND CHEMICAL CALCULATIONS OF STEELMAKING PROCESSES AND PREDICTIVE MODELS FOR THE PRODUCTION OF CLEAN STEELS
The results of physicochemical calculations of steelmaking processes for the production of clean steels de-oxidized with aluminum are presented. An approach is considered to improve the technology of clean steel production, including elements of mathematical and thermodynamic models, as well as algorithmic ap-proaches for building static models using machine learning technology, which make it possible to increase efficiency in steelmaking technologies. In order to obtain an applied application of the presented approach, it is necessary to prepare a data array in advance, as well as to interpret the results of machine learning, based on the fundamental laws and physical and chemical processes occurring in steelmaking. As a result of the thermodynamic calculations performed in the STM program, measures were developed for the production of clean steels. On the examples of the production of thin slabs and billets, bloom, the search and confirmation of significant technological parameters in the formation of steel-making de-fects due to non-metallic inclusions was carried out using methods of in-depth analytics and machine learning.
RESEARCH AND COMPARATIVE ANALYSIS OF CORROSION RESISTANCE OF COPPER-ZINC ALLOYS IN CHLORINE-CONTAINING ENVIRONMENTS
This work presents the results of studies of the electrode potential of α, β and α+β brasses, determined cor-rosion currents in chlorine-containing environments, and conducted tests on their dezincification in a copper chloride solution. In order to more deeply study the properties of brass, corrosion currents and electrode potential in chlorine-containing environments were determined for pure metals: copper and zinc. In the course of the work, graphs were constructed of the potential of copper, zinc, α, β and α+β bras-ses versus the etching time in sodium chloride solutions and a sodium chloride solution with the addition of ammonium chloride. Corrosion currents were determined in a sodium chloride solution: for copper (38 μA), α brass (70 μA), α+β brass (113 μA), β brass (88 μA) and in a sodium chloride solution with the addition of ammonium chloride: for copper ( 14 µA), zinc (71 µA), α brass (37 µA), α+β brass (44 µA), β brass (42 µA). Based on the results of a study of the resistance of alloys to dezincification, the following data were obtained: dezincification depth of brass α – 450–500 µm, α+β – 950–1000 µm, β – 600–700 µm. The results of studies of corrosion currents in chlorine-containing environments correlate with the results of dezincifica-tion experiments. The studies carried out confirm the assumption that in double brasses the α and β phases form a corrosion element due to the difference in chemical composition, and, consequently, different elec-trode potentials, which leads to the loss of zinc to a slightly greater extent than in β brass.