The article presents theoretical substantiation of the influence of electroslag remelting technology with rotation of consumable electrode on physicomechanical properties of the formed casting (billet). The technology of electroslag remelting with rotation of consumable electrode around its own axis leads to formation of upward flow of heat in the slag bath, making hydrodynamic environment in mold more rational from the point of using generated heat. During rotation of consumable electrode, centrifugal forces act on liquid metal film formed at the end of the electrode, providing radial flow of molten metal droplets. Subsequent separation occurs from the outer perimeter of electrode. Thus, drops of electrode metal fall into the metal bath closer to the wall of the mold, aligning temperature front of the bath. Decrease in temperature gradient of bath over the cross section leads to a flatter crystallization front. Studied technology of electroslag remelting with rotation of consumable electrode should have an impact on physical and mechanical properties of resulting casting (billet). In order to establish effect of rotation of consumable electrode during electroslag remelting on properties of metal obtained, experimental remelting was carried out. The article presents data on experimental electroslag remelting of electrodes of 20Kh13 grade steel using various technologies at A-550 unit. In course of experiment, influence of rotation technology of consumable electrode on conditions of remelting process, billet crystallization, changes in mechanical and physical properties was established. The influence of remelting method on complex properties of resulting billet was analyzed. As the main research tool, processing of the obtained data on microhardness, density, dendritic cell size of experimental samples was used. Analysis of the research results of billets in transverse direction showed an increase in microhardness uniformity in implementation of electroslag remelting technology with rotation of consumable electrode along the course of smelting. It is also shown that use of the rotation technology reduces size of dendritic cell of billet and increases density of the ingot formed in comparison with traditional technology without rotating electrode.

Analysis of the main drawbacks caused by increased walls thickness of a lined crucible, presence of tubular copper single-layer inductor cooled from inside with standard water and absence or presence of core I-shaped magnetic circuits arranged around it forming a discrete ferromagnetic screen, was made for modern induction crucible furnaces. The first drawback is that a significant part of working electromagnetic flow Fwork is not used for effective heating, since it passes along the non-conductive lining of crucible, and not along the cage. Therefore, only 38.5  –  57.0  % of the flow Fwork is effectively used. The second drawback is increased cost and complexity of manufacturing of inductor coils from a special copper tube, which vibrate at twice the frequency, creating noise and weakening design of the furnace. Such inductors are characterized by reduced electrical efficiency and increased cost of preparation and cooling of conditioned water in systems that occupy an area several times greater than the area of furnace itself. The third drawback leads to the fact that a significant part of electromagnetic scattering flow of the Fconsupt does not participate in heating of charge and melt, but heats conductive elements of furnace, including surrounding magnetic inductor. Irrational use of total flow F, created by inductor, reduces its efficiency to almost 19  –  30  %, and the power factor cosφ to 0.03  –  0.10 and increases energy consumption. To reduce or eliminate disadvantages, three ways of improving these furnaces are proposed and justified: reducing thickness of crucible wall with its simultaneous hardening by installing a cylindrical shell between the crucible and the inductor, surrounding the inductor with an annular magnetic circuit and using a single or multiwire inductor instead of a tubular one. Combination of cylindrical shell, annular magnetic circuit, as well as the upper and lower plates of the furnace frame can form an annular closed cavity to accommodate wire inductor and circulating refrigerant, cooling the inductor and the magnetic circuit. As a result of the study, new design of induction crucible furnace with wire inductor and ring-type magnetic circuit developed at AltSTU is proposed, substantiated and patented. Based on experimental determination of effectiveness of the proposed structural elements, conclusion is made about the prospects for further research.

The authors have studied the relation between wear intensity, average contact temperature and phase composition of the surface layers ofAISI 1020 steel, copper and NiTi alloy in dry sliding against the steel counterbody under electric current of density higher than 100  A/cm2 . These contact characteristics are considered carefully at the beginning of catastrophic wear, when the surface layers transit to the utmost state. It was noted that relaxation of stresses in the surface layers was due to the structural transformation in normal wear regime. It leads to tribolayers formation. The high strength of the copper tribolayer is first of all due to the formation of FeO oxide on the sliding surface, which prevents adhesion in contact. In addition, signs of a  liquid phase were observed on the copper contact surface. It promoted the low rate of formation and accumulation of structural defects. Emergence of areas of melt and FeO oxide on the sliding surface provides high contact wear resistance. These factors, combined with the high thermal copper conductivity, have caused the tribolayer transition to the limit state at high current density and low contact temperature. The absence of oxides on the sliding surface of the NiTi alloy has caused strong adhesion in the contact, high rate of formation and accumulation of structural defects. Therefore, the tribolayer quickly deteriorates and high wear intensity and rapid increase in the contact temperature are observed with current density increase. Therefore, the catastrophic wear of the NiTi alloy begins at a temperature about 350  °C and at low current density. The sliding surface of AISI 1020 steel contained FeO oxide, therefore strong adhesion is not manifested. Formation of FCC-Fe in tribolayer of AISI steel 1020 is detected, that promotes its accelerated deterioration. Therefore, the tribolayer of AISI steel  1020 transites to the utmost state at a relatively low current density and at a  higher temperature. The presented contact temperatures corresponding to the beginning stages of the utmost state of the tribolayer do not exceed 350  °С. Comparison of these temperatures with the known contact temperatures of other metals made it possible to assert that raising of the contact temperature of any metal higher than 400  °С leads to its utmost state. Therefore the characteristics of metals contact at temperatures of sliding contact higher than 500  °С is not of practical interest.

Presence of microvolumes most prepared for the martensite emergence in austenite is discussed. Aming many works dealing with martensitic transformations, rare works are devoted to the location of martensite origin. This aspect of transformation is important, since it allows us to obtain new knowledge about scenarios for γ  →  α transformation development during quenching of steel. The martensite embryos are submicron austenite volumes that are most prepared for phase transition and are characterized by increased energy. Experimental results were obtained by the methods of high-temperature metallography. Steel structure observed as a result of vacuum etching was studied, as well as the surface relief caused by shear during the martensitic transformation. The resulting structural patterns made it possible to observe most of the possible places for martensite emergence: nonmetallic inclusions, twins, high-angle and small-angle grain boundaries, previously formed martensite crystals, dislocations and elements of the disclination structure. It is shown that a high dislocation density is observed in the twin area, which facilitates nucleation of martensite as a result of disappearance of part of elastic energy of the dislocation when atoms inside the embryo are rearranged. When nucleation occurs on the grain boundaries, energy is released, which is used to construct a new interphase boundary and to compensate emerging elastic energy. The relative energy of the boundaries of different types was estimated by the method of multi-beam interferometry. The depth of the grooves that were formed on the surface by thermal etching was measured. Elements of disclination structure resulting from inhomogeneous deformation were observed, which are also sites of germinal centers formation. It is noted that nanoareas with ferromagnetic order, which are present in paramagnetic austenite, may not be observed with the help of the technique used in this work. However, magnetism plays a decisive role in realization of one or another scenario of the development of phase transformation in steels. Obtaining data on the interaction of ferromagnetic areas in austenite with each other, with crystal lattice defects, the magnetic field, and data on their lifetime, number and size is an important task for future research.

The paper presents experimental data on synthesis of finely dispersed powder of chromium carbide Cr₃C₂ . Chromium carbide was prepared by reduction of chromium oxide Cr₂O₃ with nanofibrous carbon (NFC) in induction furnace in argon atmosphere. NFC is a product of catalytic decomposition of light hydrocarbons. The main characteristic of NFC is high specific surface area (~150,000  m² /kg), which is significantly higher than that of carbon black (~50,000  m² /kg). Content of impurities in NFC is at the level of 1  wt  %. Based on analysis of state diagram of Cr – C system, composition of charge and the upper temperature limit of carbide formation reaction for obtaining chromium carbide in powder state are determined. Based on thermodynamic analysis, temperature of the onset of carbothermic reduction reaction of chromium oxide Cr₂O₃ was determined at various CO pressures. Characteristics of chromium carbide were studied using X-ray diffraction analysis, pycnometric analysis, scanning electron microscopy using local energy dispersive X-ray microanalysis (EDX), lowtemperature nitrogen adsorption followed by determination of specific surface area by means of BET method, sedimentation analysis, synchronous thermogravimetry and differential scanning calorimetry (TG/DSC). The material obtained at optimal parameters is represented by a single phase – chromium carbide Cr₃C₂ . Powder particles were predominantly aggregated. Average size of particles and aggregates equaled 6.5  μm within a wide range of size distribution. Specific surface value of the obtained samples was 2200  m² /kg. Oxidation of chromium carbide began at temperature of ~640  °C and practically ends at ~1000  °C. Optimum parameters of synthesis are provided by ratio of reagents according to carbide of Cr₃C₂ composition stoichiometry at temperature of 1300  °С and holding time of 20 minutes. It is shown that for this process nanofibrous carbon is an effective reducing agent and that chromium oxide Cr₂O₃ is almost completely reduced to carbide Cr₃C₂ .

Study of the effect of boron oxide and basicity of CaO – SiO₂–B₂O₃  – Al₂ O₃ slag system on MgO saturation concentration was carried out using the simplex lattice method of experimental design, which allows one to construct mathematical models describing dependence of studied property on composition as a continuous function. Synthetic slags, corresponding in composition to vertices of studied simplex, were smelted in graphite crucibles from previously calcined oxides of analytical grade. Slag compositions corresponding to the remaining points of local simplex plan were obtained by counterblending slags of simplex tops. Using experimental data, mathematical models adequately describing effect of slag composition on saturation concentration of MgO were constructed. Graphic image of mathematical modeling results is represented by the composition diagram – saturation concentration of MgO. Analysis of experimental data presented in diagram made it possible to obtain new information on the effect of boron oxide and basicity of CaO – SiO₂  – B₂O₃ slags system containing Al₂O₃ on MgO saturation concentration. It was established that in slags formed in basicity range of 2  –  3 and B₂O₃ content of 1  –  3  %, saturation concentration of MgO varies from 3 to 9  %. Increase in B₂O₃ content in slag to 4  % leads to an increase in MgO saturation concentration in slag of 11  –  13  %. Displacement of slags to area of increased basicity up to 3  –  4 is characterized by a decrease in MgO saturation concentration to 2  –  5  %, with 1  –  3  % of В₂О₃ content and an increase to 7  –  9  % at 3  –  4  % В₂О₃ in slag. Formation of slags in basicity range of 4  –  5 and B₂O₃ content of 1  –  3  % does not lead to a significant decrease in concentration of slag saturation with magnesium oxide. Saturation concentration of MgO in slag in this area of basicity varies from 2 to 4  % and practically does not reach 7  % with an increase in В₂О₃ content to 4  %. At the same time, there is an increase in cost of steel due to an increase in consumption of lime and material containing boron oxide.

Technology of arc surfacing using flux cored wire, in which tungsten oxide (WO₃) and aluminum are used as fillers, is of interest for practical application in order to save tungsten. Thermodynamic estimation of probability of 14 reactions between them under standard conditions was carried out using tabular thermodynamic data of reagents in temperature range 1500  –  3500  K. This interval includes temperature at the drop surface on the electrode at time of separation, so are temperatures at the arc periphery and in the upper layers of surfacing bath. The following states were considered as standard states for reagents: WO₃(solid), WO₃(liquid), WO₃(gas); Al(ref), Al(liquid), Al(gas), Al₂(gas), and as possible reaction products and standard states for them: W(ref), W(liquid), W(gas), Al₂O₃(solid), W; Al₂O₃(liquid), AlO(gas), AlO₂(gas), Al₂O(gas), Al₂O₂(gas). Reduction reactions of the oxide were recorded at 1 mole O₂ . Probability of reactions was evaluated using standard Gibbs energy of reactions. Calculations were carried out in four stages. Aggregate states of oxide, metal and structure of aluminum vapor, in which oxide and metal have the greatest chemical affinity for each other were established on the first and second stages. At the third and fourth stages, the most probable state was determined for metallic tungsten and the most probable composition, and aggregate state of aluminum oxide formed as a result of alumothermy of Al₂O₃(solid, liquid); Al₂O₃(liquid); AlO(gas); AlO₂(gas); Al₂O(gas); Al₂O₂(gas). According to Al – W system state diagram, there are a number of intermediates between tungsten and aluminum: W₂Al, WAl₃ , WAl₄ , WAl₅ , WAl₇ , WAl₁₂ ; however, a search for thermodynamic properties for them shows that data are available only on melting pattern (congruent or in-congruent) and temperature of transformation. No other thermodynamic data. At the same time, based on results of our previous work on restoration of tungsten oxide by carbon and silicon, it can be predicted that aluminides of a free-frame will necessarily be formed. Performed thermodynamic analysis shows that presence in flux-cored wire used for surfacing, along with tungsten oxide WO₃ as an aluminum reducing agent, will necessarily lead to occurrence of reduction reactions with formation of tungsten aluminides, and possibly tungsten itself. Tungsten oxide has the highest reactivity, being in state of WO₃(gas). Aluminum itself has the highest chemical affinity for WO₃(gas) in form of Al₂(gas) and Al(gas). Al₂O(gas) appears most likely as an oxidation product of aluminum.

Introduction of the “Automated system for operational control of casts production (OCCP AS)” makes the basis of an integrated automated production control system (APCS). It performs three main tasks: control and recording (production, products, materials, etc.), improving quality of casts and operational management of technological processes. Solution of these tasks was accomplished through automating data collection in real time for all production operations, recording material flows, creating operational communication channels, as well as centralized collection, processing and representation of data by the process information server. The next step in building an effective automated control system is to stabilize product quality in changing external conditions, for example, quality of materials, and to optimize production (technology change in order to reduce costs for constant or higher product quality). The second stage is based on mathematical processing and analysis of data coming from OCCP AS, it allows to determine optimal ranges of parameters of technological processes  – “Automated system for optimization and analysis of production progress (OAPP AS)”. OAPP AS consists of two subsystems: quality analysis and technology management. The first solves the problem of data analysis and modeling, the second – calculation of real-time optimal process parameters and real time prediction. The stages tasks compete for access to different hardware resources. The most critical parameter for OCCP AS is performance of server disk arrays, for OAPP AS it is processor performance. In either case, system scaling is effectively solved by parallelizing operations across different servers, forming a cluster, and across different processors (cores) on the same server. To process defect images and to obtain cause-and-effect characteristics, you can use OpenCV software package, which is an open source computer vision library. In course of processing, Sobel operator, Gauss filter and binarization were used. They are based on processing pixels using matrices. Operations on pixels are independent and can be performed in parallel. The task of clustering is reduced to definition of an expert method or using various mathematical algorithms for defects belonging to a specific cluster (data block) through a set of values of dependent factors. Thus, data blocks are formed by the criterion of the defect cause. Calculation of a data block to which a product defect belongs can be very resource-intensive operation. To increase efficiency of image recognition systems and parallelization ofsearch operations, it makes sense to place data clusters on different servers. As a result, there is a need for a distributed database. This is a special class of DBMS, which requires appropriate software. Generation of OAPPAS based on a multi-node cluster with ApacheCassandra DBMS installed and using Nvidia video cards supporting CUDA technology on each node will be the cheapest and most effective solution. Video card is selected based on required number of graphics processors on the node.

Results of experimental evaluation of the fatigue characteristics of tested samples material are considered based on emission of stress waves. Using previously published data on synergistically organized acoustic emission, an experiment was prepared and performed. In experiments on different materials, possibility of using acoustic emission signal for operative determination of mechanical characteristics and, above all, the limit of endurance were demonstrated. Samples for strength testing of materials were made of five steel grades and one grade of Br AZh9-4 bronze. Five experiments were conducted on each of the materials. The samples in the experiment underwent a fine-step loading, at each step of it radiation of signal occurred simultaneously, and another series of dislocations was prepared, that could reach surface of crystal and emit a stress wave at the next moment of loading. Thus, the joint radiation of energy dislocations prepared for movement was already formed. A comparison of experimental data, obtained on the basis of acoustic emission, with calculated values of endurance limit, obtained by empirical formulas through the ultimate strength of this material, performed by the Fisher criterion, has shown their adequacy at a significance level of 5 %. Evaluation of the experimental results of endurance limit determination on basis of acoustic emission by the Cochran test indicates that variances of measurement results in experiment are uniform for all types of used materials. The results have shown that such method on the basis of synergistically organized acoustic emission allows us to quickly obtain experimental values of endurance limit of material with sufficiently high degree of accuracy.

Infrared thermography and two-exposure speckle interferometry have been used to study the plastic deformation of low-carbon steel under the action of pulsed electric current. It was established that external electric effect leads to an increase in velocity of plastic waves by 65  %. Analysis of the velocity distribution patterns showed that they have the profile of “shock transition”. At the origin, velocity of the material is zero (motionless gripping), and at the right end of the curve material velocity is equal to stretching speed specified by testing machine. The effect of electric current leads to splitting of the displacements velocities, both at moving and stationary ends of the samples. It is assumed that the observed splitting is related to the Stark splitting of energy levels of the deformed system. This splitting leads to a decrease in the potential barrier for the motion of defects in crystal lattice. Thermographic studies have shown presence of a temperature gradient directed from clamps to center of the sample, which does not coincide with pattern of displacement distribution. It was determined that during the primary treatment with high power current pulses in the central area of the sample, sample temperature reaches 351  K, and 330  K in the area adjacent to clamps. Subsequent treatments result in a slight increase in temperature. This behavior of temperature can be explained by the fact that heat does not dissipate at a repetition rate of 10  Hz. On an average, sample temperature increases by 30  K. Theoretical calculation has shown that the Joule effect leads to an increase in temperature of the sample by 21  K per pulse, which is practically in agreement with experimental results. Estimates of thermal energy and energy of elastic deformation have shown that the fastest channel for converting the energy of electric pulse is structural changes in deformable system, which lead to the observed decrease in deforming force.

High-nitrogen austenitic steels are promising materials, combining high strength, plasticity and corrosion resistance properties. However, to produce high-nitrogen steel by conventional metallurgical methods under high nitrogen pressure, powerful and complex metallurgical equipment is required. From energy-saving viewpoint, an alternative and simpler method for producing high-nitrogen steels can be aluminothermy (reduction of metal oxides by metallic aluminum) under nitrogen pressure. Thermodynamic modeling of aluminothermic reactions in a nitrogen atmosphere was carried out by the authors. Aluminothermy under nitrogen pressure was used to produce high-nitrogen nickel-free Cr – N and Cr – Mn – N stainless steels with a nitrogen content of about 1  %. Microstructure (X-ray diffraction, metallography and transmission electron microscopy techniques) and mechanical properties were examined. Thermodynamic analysis has shown that the aluminothermic reduction reactions do not go to the end. The most important parameter of the synthesis is the ratio of Al and oxygen in the charge, the correct choice of which provides a compromise between completeness of oxides reduction, content of aluminum and oxygen in steel (the degree of deoxidation), and its contamination with aluminum nitride. Cr – N steel ingots in the cast state had the structure of nitrogen perlite (ferrite-nitride mixture), and Cr – Mn – N steel – ferrite-austenite structure with attributes of austenite discontinuous decomposition with Cr2 N precipitations. Quenching resulted in complete austenization of both steels. The compliance of the austenite lattice parameter obtained from the diffractograms for quenched Cr – Mn – N steel with the parameter predicted from the known concentration dependence for Cr – Mn – N austenitic steels indicated that all alloying elements (including nitrogen) were dissolved in austenite during aging at quenching temperature and fixed in the solid solution by quenching. Study of the mechanical properties of quenched Cr – Mn – N steel has shown a combination of high strength and ductility. It is concluded that by the aluminothermic method a high-nitrogen steel can be obtained, which, by mechanical properties, is not inferior to industrial steel  – analog manufacted by electroslag remelting under nitrogen pressure.

Thermodynamic analysis of oxygen solutions in silicon-containing Ni – Co melts has been carried out. The equilibrium constant of interaction of silicon and oxygen dissolved in the nickel-cobalt melts, the activity coefficients at infinite dilution, and the interaction parameters characterizing these solutions were determined for melts of different composition. The dependences of the oxygen solubility on the contents of cobalt and silicon in the studied melts were calculated. With increasing cobalt content in melt deoxidation ability of silicon decreases. In Ni – Co alloys containing more than 20  % of cobalt, when the silicon content is less than 0.2  %, deoxidizing ability of silicon is almost the same. At silicon content more than 2  %, the higher is cobalt content in alloys, the more is decrease in deoxidizing ability of silicon.