Search Results (21)

This study investigates the feasibility of producing low-carbon FeCr via metallothermic smelting of Cr concentrate and chromite spinel powder using a complex FeAlSiCa alloy as the reductant in an induction furnace. The proposed approach offers an alternative to conventional carbothermic and oxygen-blown technologies, reducing both the carbon footprint and airborne emissions. Three charge compositions were tested with varying FeAlSiCa additions (12, 14, and 16 kg per 100 kg of Cr source) and partial replacement of Cr concentrate with up to 20% CSP. Thermodynamic and microstructural analyses were conducted, and the effects of the slag basicity, temperature profiles, and holding time were assessed. In optimal conditions, Cr recovery reached up to 80% with minimal Cr₂O₃ losses in slag, and the resulting alloys met ISO 5448-81 requirements for nitrogen-containing low-carbon FeCr. Microstructural examination revealed the formation of Fe-Cr solid solutions and CrN phases, with V incorporation from the FeAlSiCa alloy. The process proved stable and energy-efficient, producing compact, non-disintegrating slag. This study highlights the potential of induction furnace smelting and chromite spinel powder valorization as a sustainable path for FeCr production. Full article

This study explored the feasibility of the carbon-free smelting of ferrochrome (FeCr) using a complex reducing agent—ferroaluminosilicalcium alloy (FeAlSiCa)—produced from industrial waste and ferrosilicochrome (FeSiCr) dust. Laboratory-scale smelting experiments were conducted with Cr concentrate and the addition of FeAlSiCa and FeSiCr dust under four different reducing agent contents: (1) 10% deficiency, (2) stoichiometric amount, (3) 10% excess, and (4) 20% excess. It was found that with a 10% excess, a nearly complete reduction of Cr₂O₃ was achieved (residual content in slag ≤ 0.9%), resulting in the formation of low-carbon FeCr (LC FeCr) with a high nitrogen content (up to 2.6%). Based on a thermodynamic analysis of the reduction reactions, the high reactivity of the FeAlSiCa and FeSiCr components (Ca, Al, and Si) at 1500 °C was confirmed. These reactions were exothermic, which demonstrates the energy efficiency of using these ferroalloys as reducing agents in FeCr smelting. The resulting slag is structurally stable and does not disintegrate over time, making it a promising candidate for potential reuse as a secondary raw material. The results demonstrate the promise of the proposed technology for both reducing the carbon footprint of ferroalloy production and lowering the cost of the metallothermic production of LC FeCr. Full article

This study presents the results of laboratory experiments on the processing of lateritic nickel ores mixed with coal and CaO, followed by the use of the obtained product for the smelting of nickel-containing ferroalloy by the metallothermic method. The study analyzed the thermodynamic effects of complex reductant concentration (silicon- and aluminum-containing alloy) on the reduction degree of nickel and iron. An experimental process resulted in a product containing Ni_total (2.60%) and Fe_total (60.52%), obtained through reduction roasting of lateritic nickel ore mixed with coal and an addition of 20 g of CaO at a temperature of 1150 °C. Under laboratory conditions, a nickel-containing ferroalloy was successfully obtained using the product after reduction roasting and a complex alloy as the reducing agent. The following optimal process parameters were determined: reductant consumption of 20 g per 100 g of the reduction roasting product, smelting temperature of 1600 °C, and slag basicity (CaO/SiO₂) of 0.5. In this case, a nickel-containing ferroalloy with 72% iron, 15% nickel, and up to 5% chromium was successfully obtained through silicon and aluminum reduction using a complex alloy. A microstructural analysis of the nickel-containing alloy was conducted using an electron probe microanalyzer (JXA-8230) in combination with scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results showed that silicon and iron were the dominant elements in all particles. Nickel was detected at concentrations of up to 15.02 wt. %, while chromium reached 3.47 wt. %. Depending on the silicon concentration, the nickel-containing ferroalloy is recommended for corrosion-resistant steel production (Si < 5%) and as a reducing agent for ferronickel production (Si > 5%). Full article

This study presents a metallothermic reduction mechanism for fabricating Nd and Nd–Fe alloys at 850–1050 °C using anhydrous NdCl₃ and Ca, which have relatively low melting points. Our method decreased the process temperature while improving the recovery rate of Nd using the thermodynamic parameters of the CaCl₂–KCl–NaCl and Nd–Fe liquid solutions. To reduce the activity of the product (CaCl₂), the optimal composition of the CaCl₂–KCl–NaCl molten salt was $X_{{CaCl}_2}=0.4(X_{KCl}:X_{NaCl}=6:4)$. The molten metal bath (Nd or Nd–Fe) that formed at the bottom of the reaction zone during Nd and Nd–Fe alloy production absorbed metal particles generated in the molten salt during the reaction, thereby facilitating ingot formation. In Nd produced at 1050 °C using 1.2× the stoichiometric amount (by mass) of Ca, the Nd recovery rate was 97.0%. Moreover, in the Nd–Fe alloys produced at 1050 °C targeting eutectic compositions, the Nd recovery rate was 96.3%. Increased Fe contents in the Nd–Fe liquid solution reduced the Nd recovery rates, and the Nd–Fe alloy (Nd recovery rate: 89.8%) was produced at 850 °C, suggesting the possibility of increasing the energy efficiency of the Nd production process. The Nd–Fe alloy produced through this proposed process could be used as a raw material in the NdFeB strip casting process. Full article

To overcome the problem of Cr₂O₃ and Al₂O₃ inclusions in CuCr50 alloy prepared by aluminothermic reduction method, in this paper, a novel methodology for strengthening metal–slag separation through in situ slagging is proposed. CuCr50 alloys were prepared by metallothermic reduction using Al and Al-Mg as reducing agents, and the physical properties of the slag, such as viscosity, density, and surface tension, were adjusted by controlling the proportion of CaO in the slagging agent in the raw material to achieve good separation of the slag–metal. The results show that with the ratio of CaO increased, CaO and MgO were coupled to make slag, which combined with Cr₂O₃ and Al₂O₃ to form CaCr₂O₄, MgCr₂O₄, and CaAl₄O₇ in the slag, thus reducing the content of impurities in the alloy. When RCaO/(CaO + Al₂O₃ + MgO) = 20%, the Cr content ranged from 46.61% to 47.09%, the inclusions accounted for 1.60%, the Cr particle size was refined to 20 µm, the number of Cr spherical crystals accounted for 9.88%, the conductivity reached 14.96 MS/m, and the hardness reached 100.23 HB. After heat treatment, the Cr phase was refined in the alloy, the conductivity increased from 14.96 MS/m to 18.27 MS/m, and the hardness increased from 100.23 HB to 103.1 HB. This method is expected to provide an effective method for the preparation of CuCr50 contact materials. Full article

In situ formation of TiB₂–Mg₂TiO₄ composites was investigated by combustion synthesis involving the solid-state reaction of Ti with boron and magnesiothermic reduction of B₂O₃. Certain amounts of MgO and TiO₂ were added to the reactant mixtures of Ti/B/Mg/B₂O₃ to act as the moderator of highly exothermic combustion and a portion of the precursors to form Mg₂TiO₄. Two combustion systems were designed to ensure that synthesis reactions were sufficiently energetic to carry on self-sustainably, that is, in the mode of self-propagating high-temperature synthesis (SHS). Consistent with thermodynamic analyses, experimental results indicated that the increase in pre-added MgO and TiO₂ decreased the combustion temperature and propagation velocity of the flame front. MgO was shown to have a stronger dilution effect on combustion exothermicity than TiO₂, because the extent of magnesiothermic reduction of B₂O₃ was reduced in the MgO-added samples. In situ formation of the TiB₂–Mg₂TiO₄ composite was achieved from both types of samples. It is believed that, in the course of the SHS progression, Mg₂TiO₄ was produced through a combination reaction between MgO and TiO₂, both of which were entirely or partially generated from the metallothermic reduction of B₂O₃. The microstructure of the products exhibited fine TiB₂ crystals in the shape of short rods and thin platelets that existed within the gaps of Mg₂AlO₄ grains. Both constituent phases were well distributed. A novel and efficient synthesis route, which is energy- and time-saving, for producing Mg₂TiO₄-containing composites was demonstrated. Full article

Nd, Pr and Dy are critical raw materials as major components for rare earth permanent magnets (REPM). These are integral for several components placed for example within electric vehicles and wind turbine generators. REE primary production is mainly realized in China (~80%) and no REPM recycling industry has been established. Hydrometallurgical recycling routes lead to iron dissolution (66 wt. % Fe in REPM), while pyrometallurgical approaches that utilize SiO₂ risk contaminating the produced iron phase. A two-step process is presented that (i) creates an FeO_x-CaO-Al₂O₃-REE₂O₃ molten slag at 1500 °C through oxidative smelting and (ii) separates an iron-depleted slag phase (CaO-Al₂O₃-REE₂O₃) and a molten iron phase via carbothermic or metallothermic reduction at 1700–2000 °C. The slag has been designed as a selective collector phase and the REE₂O₃ loading within the bulk slag can reach up 25 wt. % REE₂O₃ at 1700 °C. The contained minerals within the slag exhibit >40 wt. % REE (a higher REE concentration than in the initial REPM). The resulting phases are characterized via ICP-OES, CS and SEM-EDX. In addition, the first results with regard to the downstream hydrometallurgical processing of the CaO-Al₂O₃-REE₂O₃ slag are presented aiming at the recovery of REE₂O₃, as well as of CaO and Al₂O₃. The latter compounds are to be reused during the first process step, i.e., the oxidative smelting of REPM. Slag leaching with methane sulfonic acid (MSA) and separation with alternative methods, such as solvent extraction, seems promising. Future work will include slag filtration with the aim to separate REE-rich solid phases (minerals) from the slag and also molten salt electrolysis of the produced REE₂O₃ oxides. Full article

Fundamental studies have been carried out experimentally and theoretically on the magnesiothermic reduction of silica with different Mg/SiO₂ molar ratios (1–4) in the temperature range of 1073 to 1373 K with different reaction times (10–240 min). Due to the kinetic barriers occurring in metallothermic reductions, the equilibrium relations calculated by the well-known thermochemical software FactSage (version 8.2) and its databanks are not adequate to describe the experimental observations. The unreacted silica core encapsulated by the reduction products can be found in some parts of laboratory samples. However, other parts of samples show that the metallothermic reduction disappears almost completely. Some quartz particles are broken into fine pieces and form many tiny cracks. Magnesium reactants are able to infiltrate the core of silica particles via tiny fracture pathways, thereby enabling the reaction to occur almost completely. The traditional unreacted core model is thus inadequate to represent such complicated reaction schemes. In the present work, an attempt is made to apply a machine learning approach using hybrid datasets in order to describe complex magnesiothermic reductions. In addition to the experimental laboratory data, equilibrium relations calculated by the thermochemical database are also introduced as boundary conditions for the magnesiothermic reductions, assuming a sufficiently long reaction time. The physics-informed Gaussian process machine (GPM) is then developed and used to describe hybrid data, given its advantages when describing small datasets. A composite kernel for the GPM is specifically developed to mitigate the overfitting problems commonly encountered when using generic kernels. Training the physics-informed Gaussian process machine (GPM) with the hybrid dataset results in a regression score of 0.9665. The trained GPM is thus used to predict the effects of Mg-SiO₂ mixtures, temperatures, and reaction times on the products of a magnesiothermic reduction, that have not been covered by experiments. Additional experimental validation indicates that the GPM works well for the interpolates of the observations. Full article

In the present study, a powder of Ti-18Zr-15Nb biomedical alloy with spongy morphology and with more than 95% vol. of β-Ti was obtained by reducing the constituent oxides with calcium hydride. The influence of the synthesis temperature, the exposure time, and the density of the charge (TiO₂ + ZrO₂ + Nb₂O₅ + CaH₂) on the mechanism and kinetics of the calcium hydride synthesis of the Ti-18Zr-15Nb β-alloy was studied. Temperature and exposure time were established as crucial parameters with the help of regression analysis. Moreover, the correlation between the homogeneity of the powder obtained and the lattice microstrain of β-Ti is shown. As a result, temperatures above 1200 °C and an exposure time longer than 12 h are required to obtain a Ti-18Zr-15Nb powder with a single β-phase structure and uniformly distributed elements. The analysis of β-phase growth kinetics revealed that the formation of β-Ti occurs due to the solid-state diffusion interaction between Ti, Nb, and Zr under the calcium hydride reduction of TiO₂ + ZrO₂ + Nb₂O₅, and the spongy morphology of reduced α-Ti is inherited by the β-phase. Thus, the results obtained provide a promising approach for manufacturing biocompatible porous implants from β-Ti alloys that are believed to be attractive candidates for biomedical applications. Moreover, the current study develops and deepens the theory and practical aspects of the metallothermic synthesis of metallic materials and can be compelling to specialists in powder metallurgy. Full article

TiB₂–MgAl₂O₄ composites were fabricated by combustion synthesis involving metallothermic reduction reactions. Thermite reagents contained Al and Mg as dual reductants and TiO₂ or B₂O₃ as the oxidant. The reactant mixtures also comprised elemental Ti and boron, as well as a small amount of Al₂O₃ or MgO to serve as the combustion moderator. Four reaction systems were conducted and all of them were exothermic enough to proceed in the mode of self-propagating high-temperature synthesis (SHS). The reaction based on B₂O₃/Al/Mg thermite and diluted with MgO was the most exothermic, while that containing TiO₂/Al/Mg thermite and Al₂O₃ as the diluent was the least. Depending on different thermites and diluents, the combustion front temperatures in a range from 1320 to 1720 °C, and combustion wave velocity from 3.9 to 5.7 mm/s were measured. The XRD spectra confirmed in situ formation of TiB₂ and MgAl₂O₄. It is believed that MgAl₂O₄ was synthesized through a combination reaction between Al₂O₃ and MgO, both of which can be totally or partially produced from the metallothermic reduction of B₂O₃ or TiO₂. The microstructure of the TiB₂–MgAl₂O₄ composite exhibited fine TiB₂ crystals surrounded by large densified MgAl₂O₄ grains. This study demonstrated an energy-saving and efficient route for fabricating MgAl₂O₄-containing composites. Full article

At present, magnesium master alloys with such rare earth metals (REM) as yttrium are used in the production of alloys of magnesium and aluminum. These alloys especially the system Mg-6Zn-1Y-0,5Zr are commonly used in the aircraft and automotive industries. The article is devoted to the exploration of the synthesis process features for ternary magnesium master alloys with yttrium and zinc. The authors used X-ray fluorescence analysis (XRF), differential thermal analysis (DTA), and X-ray spectral analysis (XRD). Optical microscopy was used to conduct microstructural studies. The thermal effects that occur during metallothermic reactions of yttrium reduction from the YF₃-NaCl-KCl-CaCl₂ salt mixture with a melt of magnesium and zinc were investigated, and the temperatures of these effects were determined. It has been confirmed that the metallothermic reaction of yttrium reduction proceeds from the precursors of the composition: Na_1.5Y_2.5F₉, NaYF₄, Na₅Y₉F₃₂, and KY₇F₂₂, and starts at a temperature of 471 °C. The results of experimental studies of the process of metallothermic reduction of yttrium from the salt mixture YF₃-NaCl-KCl-CaCl₂ are presented in detail. These experiments were carried out in a pit furnace at temperatures ranging from 650 to 700 °C, and it was found that, at a synthesis temperature of 700 °C, the yttrium yield is up to 99.1–99.8%. The paper establishes rational technological regimes for the synthesis (temperature 700 °C, exposure for 25 min, the ratio of chlorides to yttrium fluoride 6:1, periodic stirring of the molten metal) at which the yttrium yield reaches up to 99.8%. The structure of the master alloy samples obtained during the experiments was studied. That structure can be distinguished by a uniform distribution of ternary intermetallic compounds (Mg₃YZn₆) in the bulk of the double magnesium–zinc eutectic. Studies have been carried out on testing the obtained ternary master alloy as an alloying material in the production of alloys of the Mg-6Zn-1Y-0.5Zr system, while the digestibility of yttrium ranged from 91 to 95%. Full article

In this study, industrial lithium-ion battery (LIB) waste was treated by a froth flotation process, which allowed selective separation of electrode particles from metallic-rich fractions containing Cu and Al. In the flotation experiments, recovery rates of ~80 and 98.8% for the cathode active elements (Co, Ni, Mn) and graphite were achieved, respectively. The recovered metals from the flotation fraction were subsequently used in high-temperature Cu-slag reduction. In this manner, the possibility of using metallothermic reduction for Cu-slag reduction using Al-wires from LIB waste as the main reductant was studied. The behavior of valuable (Cu, Ni, Co, Li) and hazardous metals (Zn, As, Sb, Pb), as a function of time as well as the influence of Cu-slag-to-spent battery (SB) ratio, were investigated. The results showcase a suitable process to recover copper from spent batteries and industrial Cu-slag. Cu-concentration decreased to approximately 0.3 wt.% after 60 min reduction time in all samples where Cu/Al-rich LIB waste fraction was added. It was also showed that aluminothermic reduction is effective for removing hazardous metals from the slag. The proposed process is also capable of recovering Cu, Co, and Ni from both Cu-slag and LIB waste, resulting in a secondary Cu slag that can be used in various applications. Full article

The scholarly literature records information related to the performance increase of the cutting tools covered by the superficial layers formed “in situ” when applying thermochemical processing. In this context, information is frequently reported on the carbamide role in processes aiming carbon and nitrogen surface saturation. Sulfur, together with these elements adsorbed and diffused in the cutting tools superficial layers, undoubtedly ensures an increase of their operating sustainability. The present paper discusses the process of sulfonitrocarburizing in pulverulent solid media of high-speed tools steel (AISI T1, HS18-0-1) and its consequences. The peculiarity of the considered process is that the source of nitrogen and carbon is mainly carbamide (CON₂H₄), which is found in solid powdery mixtures together with components that do not lead to cyan complex formation (non-toxic media), and the sulfur source is native sulfur. The kinetics of the sulfonitrocarburizing process, depending on the carbamide proportion in the powdered solid mixture and the processing temperature, was studied. The consequences of the achieved sulfonitrocarburized layers on the cutting tools’ performance are expressed by the maximum permissible cutting speed and the maximum cut length. An interesting aspect is highlighted, namely the possibility of using chemically active mixtures. Their components, by initiation of the metallothermic reduction reaction, become able to provide both elements of interest and the amount of heat needed for the ultrafast saturation of the targeted metal surfaces. Full article

Rare earth metals (REM) with magnetic properties find application in the recently developed high-tech industries. Sensor magnetic systems based on neodymium are increasingly in demand in modern engineering and geological surveys due to their favorable combination of properties of magnetic materials based on rare earth metals. One of the problems is to obtain high-quality materials for the production of such magnetic sensors. It should be noted that the high activity of REM does not allow obtaining master alloys and REM-based alloys from metallic materials; it is advisable to use halide compounds. This work discusses a method for producing neodymium fluoride from its oxide. REM fluorides can be obtained by fluorinating the oxides of these metals. Various fluorine-containing compounds or elemental fluorine are usually used as fluorinating reagents, which have their own advantages and disadvantages. The thermodynamic and technological analysis of neodymium fluoride production processes has shown the most acceptable fluorinating agent is ammonium hydrofluoride, which was used in this work. In order to increase the productivity and degree of chemical transformation, it was proposed to perform heating stepwise; i.e., at the initial stage, heat at a speed of 3 degrees per minute, after which the heating speed was reduced to 2 degrees per minute, and finally the speed was reduced to 1 degree per minute. Due to proposed heating mode, the same productivity and yield of chemical transformation were achieved, with an increased efficiency up to 30%, which can significantly reduce the cost of production. The obtained product is used in the production of neodymium-based alloys by metallothermic reduction of a mixture of fluorides. The sensor material obtained in this way is characterized by a low (less than 0.05%) oxygen content. Full article

Aluminum master alloys with rare earth metals are widely studied by many scientists around the world, but research on the production of Al-Er master alloys is still limited. The purpose of this work is to study the microstructure parameters of aluminum-erbium master alloys obtained by metallothermic reduction of salt mixtures containing erbium oxide or fluoride. The structural features were investigated by optical and scanning electron microscopy, and the dependence of the microhardness of the eutectic and solid solution fields of obtained master alloys on the content of erbium in the master alloy was determined. Studies have shown that master alloys obtained by metallothermic reduction of erbium compounds from chloride–fluoride melts are characterized by a uniform distribution of Al₃Er intermetallic compounds in the volume of double eutectic [(Al) + Al₃Er] and have a strong grain refinement effect. The analysis of the microstructure showed that the structure of the master alloys varies depending on the content of erbium. When the content of erbium in the master alloy is up to 6 wt.%, the eutectic structure is preserved. When the content of erbium in the master alloy is 8 wt.% or more, the structure becomes a solid solution with individual inclusions of various shapes and intermetallic compounds. Full article