An urgent task facing the modern metallurgical industry is to increase the complexity of using mineral and technogenic raw materials by developing new technologies based on the principle of joint processing of raw materials from deposits that differ in the mineral composition of the ore component, for example, titanium-containing ores – ilmenite and perovskite. Joint processing of titanium-containing ores will improve the environmental and economic efficiency of processing domestic mineral raw materials, and will also create prerequisites for the development of titanium dioxide production in Russia. In order to scientifically substantiate the feasibility of joint processing of different types of titanium raw materials, the effect of temperature, reducing agent consumption and concentrate ratio on the phase formation process during carbothermic reduction of concentrate mixtures was established using thermodynamic modeling. The distribution of target metals by interaction products is consi­dered, optimal parameters for the process of formation of rich titanium slags are proposed. The authors assessed the prospects for the associa­ted extraction of rare and rare-earth metals. Thermodynamic analysis of the process of carbothermic reduction of mixtures, performed on model compositions of perovskite and ilmenite concentrates, showed that at low values ​​of the perovskite concentrate / ilmenite concentrate (PC/IC) ratio, one can expect the formation of high-titanium slags with a TiO2 content of more than 80 %. However, concentration of Nb extracted into the alloy and content of rare earth elements in the slag will decrease several times compared to their initial values ​​in the perovskite concentrate. At a PC/IC ratio of 1, it is possible to accumulate up to 2.5 % Nb in the alloy with a TiO2 content of up to 74 % in the slag. The advantage of joint processing of ilmenite and perovskite raw materials by the pyrometallurgical method is the ability to obtain rich titanium slags and selectively concentrate rare metals in the metallic phase, separating them from titanium, and rare earth metals in the slag within the framework of a single process flow sheet.

In modern electric arc furnaces (EAF), charge heating by natural gas (NG) combustion products with process oxygen is widely used to reduce the power consumption and intensify the thermal performance. In existing EAF burners, gas and oxygen are supplied separately through oxygen gas and refining burners, which ensures the diffusion combustion mode. The diffusion mode in conditions of EAF working space has a number of disadvantages, such as non-optimal distribution of temperature and concentration fields of combustion products, increased burn-off of iron-containing components of the charge. This paper presents the results of a computational study of the physico-chemical properties of combustion products along the torch length for the burners of VAI FUCHS, SMS DEMAG and NTPF Etalon Ltd. companies at oxygen concentration in the oxidizer of 95 wt. %. The results of computer modeling of temperature fields in the torches were analyzed in order to assess the risk of flame “slip” into the burner internal volume. The authors carried out a comparative study of the characteristics of torches in the burner devices with diffusion and kinetic combustion modes. Based on the data obtained, a transition from the diffusion mode of natural gas combustion to the kinetic mode is proposed, which can increase the energy efficiency of using burners, uniformity of temperature and concentration fields of combustion products, and reduce carbon monoxide of the iron-containing charge. The study was performed using computer modeling in ANSYS software package in CFX module. The obtained results can be useful for optimizing thermal processes in EAF working space, reducing power consumption and preventing emergency operation of burners.

Hot Briquetted Iron (HBI) or Direct Reduced Iron (Pellets) (DRI) is one of the most sought-after products in the steel industry because its use enables the environmentally friendly production of high grade steels. The purpose of this paper is to study the process of pellets carburization under the conditions of a shaft direct reduction (metallization) furnace in comparison with the carburization of pellets due to the preparation of an ore-carbon burden. Hot briquetted iron produced in the HYL-III process is different from Midrex briquettes in terms of carbon content. Difference in the amount of carbon is attributed to the processes of carburization and pyrolysis of natural gas in the shaft furnace workspace, as well as difference in composition of the gas phase and pressure in the workspace of the HYL and Midrex furnaces. As is known, the HYL-III process utilizes vapor conversion (higher H₂/CO ratio) at elevated gas pressures beneath the furnace top, in contrast to the Midrex process. An increase in the carbon monoxide (CO) content in the gas phase of the Midrex process (carbon dioxide conversion) results in intensification on the pellet surface that was reduced to metal. The findings of the study demonstrated that carburization of pellets to a greater than 4.5 % carbon content through the process of gas metallization (direct reduction) in shaft furnaces is indeed feasible. The Midrex process, which relies on the reducing agent, mostly carbon monoxide (CO), allows for the treatment of pellets with methane. In contrast, the HYL process, which utilizes hydrogen (H₂) mostly as the reducing agent, necessitates the addition of solid carbon, such as soot or coke breeze etc., to the burden for carburization. This finding suggests the potential for utilization of carbon-containing briquettes in metallization processes. Carbon, despite its presence in the form of a separate phase (soot), cannot be separated from the iron-containing components of pellets by magnetic separation or washing and does not pose any danger.

In steelmaking, the refractory material used as a lining is easily destroyed by slag, which not only decreases the service life of ceramics but also makes worse a production quality because of increase in the number of nonmetallic inclusions in metal. If the slag has good wettability, it tends to penetrate the refractory through pores and cracks. As a result, a boundary layer is formed, which has a structure and properties different from the initial material. The sessile drop method was used to study the interaction of Al₂O₃-based refractory ceramics with the liquid slag 45 % CaO – 40 % Al₂O₃ – 10 % SiO₂ – 5 % MgO. The substantial decrease in the wetting angle to 20° in the initial 5 min of experiment and the further small decrease to 13.5° in the next 115 min were observed. The microstructural examination and elemental mapping of the boundaries of cross sections of slag and ceramics were carried out. The slag consists of several phases, namely: Ca2(Mg_0.25Al_0.75)(Si_1.25Al_0.75O₇); CaAl₂O₄, CaAl₄O₇ and MgAl₂O₄. As was found, the slag–ceramics boundary layer consisted of calcium aluminate (CaAl₄O₇) and, at the grain bounda­ries of aluminum oxide in the refractory material, hibonite (CaAl₁₂O₁₉) was formed. X-ray diffraction analysis of initial ceramics showed that it contained ~8 % CaAl₄O₇, and after interaction with the slag ~32 % CaAl₁₂O₁₉. At a depth of 4 mm, the presence of calcium aluminates both in the central and peripheral zones of ceramics was observed. This indicates the slag penetration into the ceramics and their chemical interaction.

The paper reviews the studies on relationship between the structure, phase composition, and properties of ferroalloys, as well as their impact on the quality of treated metals. The requirements for ferroalloys include not only chemical composition but also a range of properties: optimal melting temperature, oxidation resistance, density, and time of dissolution in the treated melt. The structure and phase composition of the alloys are also crucial, as they affect friability, element segregation within the ingot, crushability, and formation of fine fractions. The study presents research findings aimed at addressing the issue of spontaneous disintegration of ferrosilicon caused by the eutectoid transformation of leboite and pre­sence of impurities. Methods to prevent ferroalloy disintegration are proposed, including rapid cooling, reducing impurity content, and stabilizing the structure through additives such as boron. The structural features of other alloys, such as silicocalcium, are also examined, where improved crushability is achieved by slowing crystallization and modifying phase composition. Approaches to modeling the phase composition of ferroalloys are discussed, including thermodynamic-diagram methods and polygonal phase diagram analysis. The results of studies on rapid cooling of modifiers demonstrate enhanced efficiency due to the fine-grained structure and uniform distribution of active elements. It was established that the structure of ferroalloys influences the primary crystallization of cast iron, determining graphite morphology and matrix structure. The impact of phase composition and non-metallic inclusions (oxides, sulfides) in ferroalloys on steel properties is also demonstrated. Based on the review, the necessity of considering the structural and phase characteristics of ferroalloys is highlighted, as this can improve metallurgical product quality, reduce material consumption, and minimize adverse effects.

The study analyzes the effect of laser power and velocity on the structural phase state and properties of complex-alloyed titanium alloy VT23 (Ti–Al–V–Mo–Cr–Fe) obtained by direct laser deposition. VT23 titanium alloy has a unique combination of strength, corrosion resistance, and biocompatibility, which makes it in demand in the aerospace and medical industries. However, traditional manufacturing methods (casting, stamping) often fail to provide the required accuracy and quality of complex parts. In this work, X-ray phase analysis and optical metallography revealed that the deposited samples consist of α- and β-phases (~20 % β-phase) with a typical “basket weave” structure. In macrostructure of the obtained samples, thermal bands and interlayer boundaries were recorded, the formation of which is associated with the peculiarities of crystallization process during direct laser deposition. The results of optical metallography showed that microstructure of the deposited material combines large columnar crystals in the overlap areas of two adjacent layers, as well as small equiaxed grains. Despite this distribution of structural components, the microhardness (~488 HV_0.2) remains homogeneous throughout the deposited samples in both the laser scanning and sample deposition directions. The results confirm that direct laser deposition can be used to produce VT23 titanium alloy parts with a controlled microstructure. Optimization of the process parameters of direct laser deposition minimizes the probability of defect formation and provides stable mechanical properties, which opens prospects for application of the technology in the production of critical parts.

Traditionally, for stainless steel smelting in the process of argon-oxygen decarburization, fluorspar is used to liquefy the slag and ensure the normal course of the refining and reduction of chromium oxide. Fluospar is characterized by high volatility at high temperatures of the steelmaking process, while the resulting compounds are toxic and hazardous to the environment. For this reason, the paper considers the replacement of fluorspar with boron oxide, which is also capable of forming low-melting eutectics with the main components of slag, at the final stage of steel processing during the argon-oxygen decarburization process – during the desulfurization period. It was found that, despite an increase in the degree of slag polymerization as a result of the introduction of boron oxide to 6 %, due to its ability to form low-melting compounds, an increase in its content has a beneficial effect on the fluidity of slags of the studied СаО – SiO₂ – В₂O₃ – 2 % Cr₂O₃ – 3 % Аl₂O₃ – 8 % МgO system at a basicity of CaO/SiO₂ of 1.0 and 2.5. The content of 6 % B₂O₃ in slag with a high basicity of 2.5 makes it possible to achieve viscosity values ​​of 0.3 Pa·s, which are favo­rable for sulfur removal. In this case, the equilibrium sulfur content in the metal can reach 0.003 % according to the thermodynamic modeling. As a result of the experimental studies, the minimum sulfur content was 0.006 %, which is close to the equilibrium concentration. During the treatment of steel samples with slags, direct steel microalloying with boron in the amount of 0.002 – 0.003 % occurred. A small amount of boron transferred to steel during direct microalloying, according to literary data, has a beneficial effect on the ductility and corrosion resistance of the metal product. 

The Ural metallurgical enterprises compensate for the deficit of iron ore raw materials by supplying materials from Central Russia, the Kola Peninsula and Kazakhstan. Carbonate iron ores (siderites) of the Bakalskoye deposit are poor ores and, despite large reserves (about 1 billion tons), are not in great demand among metallurgists due to their low quality (low iron content and high magnesium content). The prospects for developing the Bakalskoye deposit depend on the availability of new technologies for processing siderites. There is a technology for processing poor iron ores using the coke-free metallurgy method, including reducing roasting in a rotary kiln, grinding and magnetic separation to obtain a highly metallized product suitable for steelmaking. Laboratory studies and industrial tests confirmed its suitability for processing siderites. A modernized technology for processing siderites is proposed, in which the operations of grinding and magnetic separation are excluded, and the product of reducing roasting in a rotary kiln is loaded hot into an electric furnace for separating melting. The process is carried out in the presence of colemanite containing boric anhydride to obtain liquid slag. During melting, part of the boron passes into the metal melt. By means of thermodynamic modeling, an assessment of the distribution of boron between the metal and slag as a result of separating melting is carried out. With a content of 5 and 10 % of colemanite in the charge, depending on the proportion of carbon, up to 60 % of boron passes into the metal. Such metal can be used as a ligature for obtaining boron-containing steel or cast iron. When bubbling the metal melt with oxygen, boron content can be reduced to 0.0001 %.

Based on the results of viscometric studies of the patterns of precision iron-carbon melts formation, the need to take into account the structural state of the initial iron melt and the carbon material when developing the optimal carburization technology is substantiated. Considering the kinematic viscosity value and stability of the values ​​of this structure-sensitive property as indicators of the non-equilibrium degree of the iron-carbon melt structural state, it is shown that the optimal solution should be considered to be the carburization of liquid iron with a predominantly fcc-like short-range order structure, which can be facilitated by introducing carbon into the charge composition, forced heating and melting with the formation of a melt with significant overheating above the liquidus temperature. Using the data of X-ray structural analysis, it was experimentally established that when using carbon materials subjected to graphitization for carburization, it is advisable to reduce the proportion of the amorphous phase, increase the size of crystallites and the graphitization degree, and improve the structural homogeneity. The experimentally determined difference in the nature of melt formation during carburization of pure iron and in the case of simultaneous deoxidation and carburization of highly oxidized metal is associated with the process of deactivation of the carbon material surface by oxygen, the development degree of which depends on reactivity of the carbon material and decreases with an increase in the degree of its graphitization and a decrease in the defectiveness of the crystal structure. During the simultaneous deoxidation and carburization of highly oxidized iron, a significant role of the deoxidizer type was established, which is associated with the different partial influence of the materials used on structural state of the iron melt and with the different neutralization degree of the effect of oxygen on deactivation of the surface of carburizer particles.

The temperature (up to 1700 °C) and concentration dependences of the viscosity of liquid binary alloys of cobalt with silicon and boron were studied using an oscillating-cup method. The viscosity polytherms of liquid cobalt and its melts with silicon and boron (up to 54 at. % of the metalloid) are monotonous character without any anomalies and are well described by the Arrhenius equation. Coincidence of the viscosity polytherms obtained in the heating and cooling modes and linear dependence of the viscosity logarithm on the inverse absolute temperature in the supercooled region indicate the preservation of the liquid alloy structure. Microheterogeneous structure of Co – Si and Co – B melts (up to 54 at. % metalloid), associated with the formation of microgroups based on silicides and borides of cobalt with stronger internal bonds, leads to a complex form of concent­ration dependences of their viscosity and activation energy of viscous flow. The prognostic capabilities of the Kozlov-Romanov-Petrov and Kaptay equations for describing the concentration dependences of the viscosity of liquid metal-metalloid alloys are discussed. Features associated with the application of these equations to the systems in which one of the alloy components (in this case, boron in the Co – B system) is in the solid state at the calculation temperatures are considered. It is shown that the correct way to solve the problem is to use the viscosity value of liquid boron at its melting point as an input parameter for calculating the viscosity isotherms of the Co – B melts. The Kozlov-Romanov-Petrov and Kaptay equations differ only in the coefficients before the melt mixing enthalpy, the physical meaning of which is discussed in the paper. The Kozlov-Romanov-Petrov equation can be recommended for predicting the concentration dependences of the viscosity of liquid alloys of cobalt with silicon and boron.

The paper presents the experimental data on the effect of amphoteric oxides content (Al₂O₃ and Fe₂O₃) in slags on the metallurgical slags properties. It is noted that the parameters of the electric arc valve effect, such as the constant component of the arc voltage or the constant component of the electrode current, can act as a criterion for assessing the slag basicity. Up to a slag content of 18 wt. %, aluminum oxide exhibits mainly basic properties, and above that, acidic properties. For Fe₂O₃, the threshold value is the content of 20 wt. %. The data obtained make it possible to more reasonably adjust the smelting slag mode. In particular, for the current trend on metallurgical enterprises to replace fluorspar in the out-of-furnace steel processing with other slag liquefiers, these data allow to determine the limit of aluminum oxide content at which the conditions of metal refining from sulfur will not be degraded. For arc steelmaking furnaces, this technique is one of the options for non-contact operational assessment of the metal bath state, the foaming slag quality to cover the arcs, and the metal oxidation degree at the melting end and its readiness for tapping. The use of constant components of the arc voltage and current in the electrode for operational control of the tendency of amphoteric oxides to basic or acidic properties during melting in industrial conditions is not possible due to a large number and multidirectional influence of the slag components. Nevertheless, this technique will be useful in control of steelmaking technological process with digital twin models and their accompanying databases.

The authors studied the behavior of slag inclusions in four samples taken during casting of austenitic corrosion-resistant steel grade 12Kh18N9TL. The samples for the study were taken under production conditions after melting the charge (1), introducing Ti and FeMn, slag induction and additional loading (2), re-introducing Ti, slag induction (3), slag induction (4). The elemental composition and temperature of the melt were determined under production conditions. The physicochemical properties of the melts obtained from the selected samples were measured under laboratory conditions: surface tension and kinematic viscosity. The measurements were carried out in the temperature range from 1370 to 1760 °C in the mode of heating and subsequent cooling of the sample. When observing the sample during the measurement of surface tension, the release of slag inclusions from the volume of the drop occurs in the heating mode. During subsequent cooling of the formed drop of liquid steel, slag particles flow from the slag bath under the action of the Marangoni force. Analysis of the dependence of the slag particle ascent rate on its size showed that only particles up to 10 μm in size can remain in the melt volume, while larger particles have time to float to the surface of the liquid bath. It was found that slag particles up to 4 mm in size can flow onto the surface of the sample under the action of the Marangoni force. The volume fraction of slag inclusions was determined, and a correlation was established between it and the element composition of the sample. The authors made a conclusion about the effect of Ti additives in the melt as the cause of increase in the volume fraction of slag inclusions in the casting.

The growth of steel production and consumption leads to the formation of a large amount of technogenic waste. One of the wastes is electric arc furnace (EAF) dust. In the Russian Federation, about 0.7 million tons of dust are annually generated. The paper studies the dust of one of the metallurgical enterprises, in which zinc is mainly contained in the form of ZnFe₂O₄, and also contains harmful compounds of Cl and Pb, which reduce the quality of Waelz oxide during subsequent processing. The studied dust was subjected to high-temperature oxidative roasting in a muffle furnace. The experiments were carried out in the temperature range of 300 – 1100 °C with roasting time of 1 h. In the temperature range of 900 – 1100 °C, the roasting time varied within 3 – 9 h. The composition was determined using XRD phase analysis and micro-X-ray spectral method. It was found that at temperature of 900 °C and roasting time of 9 h the degree of Cl removal reaches 78 %. At temperature of 1000 ℃ and roasting time of 9 h, the degree of Cl removal reaches 99.4 % with Zn losses of 19.8 %. At temperature of 1100 ℃ and roasting time of 3 h the degree of Cl removal is 91.2 %, and Zn losses reach 37.8 %; thereby, carrying out the oxidative roasting at this temperature is impractical. Experimental studies have shown that it is possible to effectively remove chlorine from EAF dust which predominantly contains zinc in the form of ZnFe₂O₄ using high-temperature oxidative roasting with relatively low zinc losses in the temperature range of 900 – 1000 °C.