Production of Chromium–Manganese Ligature from Low-Grade Chromium and Iron–Manganese Ores Using Silicon–Aluminum Alloys as Reductants

Abstract

This study investigates the production of chromium–manganese ligature by a metallothermic process using complex silicon–aluminum reducing agents. Low-grade chromium and iron–manganese ores from the Kempirsai and Kerege-Tas deposits in Kazakhstan were used as raw materials, while the reducing agents included alumosilicomanganese alloy (AlSiMn) and ferrosilicoaluminum (FeSiAl). Thermodynamic calculations were performed with HSC Chemistry 10 at 1400–1800 °C and reducing agent dosages of 10–100 kg per 100 kg of ore charge. Crucible smelting experiments were then carried out in a Tamman furnace, followed by large-scale laboratory trials in a 100 kVA refining electric furnace to verify reproducibility, with a total of 14 runs. The chemical composition of the ligatures varied depending on the reductant: with AlSiMn the alloy contained Fe—23.14%, Cr—53.74%, Mn—20.03%, and Si—3.06%; with FeSiAl, it contained Fe—42.01%, Cr—25.74%, Mn—27.15%, and Si—5.05%; and with FeSiCr dust, it contained Fe—34.45%, Cr—21.45%, Mn—39.82%, and Si—4.24%. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed the presence of α-(Fe,Cr,Mn), FeSi, and Cr₅Si₃ phases. The results demonstrate the efficiency of complex silicon–aluminum reducing agents and the ability to regulate the composition of chromium–manganese ligatures by the selected reductant.

1. Introduction

Global steel production demonstrates steady growth, driven by the development of mechanical engineering, construction, and the defense industry, as well as by global technological trends that increase the demand for high-quality metal products. Under these conditions, the demand for ferroalloys and alloying components, which directly determine the strength and performance characteristics of steel, is significantly increasing. Against this background, interest is growing in the development of multicomponent and complex ferroalloys that include not only traditional but also specially selected new elements. Such alloys possess improved physicochemical properties and allow for more efficient interaction with melts while reducing production costs [1,2,3,4,5,6]. As a result, they become more economically advantageous compared to conventional analogs, either by reducing raw material consumption or by improving its utilization efficiency. A special place among such alloys is occupied by chromium–manganese ligature, which can significantly enhance the properties of steel—strength, wear resistance, corrosion resistance, and resistance to high temperatures [7,8,9,10,11,12].

At present, chromium–manganese ligature is considered one of the most promising components for steel alloying, especially under conditions where the efficiency of alloying additives needs to be improved. Among the wide range of available alloys, it is distinguished by favorable technological characteristics, including an optimal density (about 6.8 g/cm³), which ensures its uniform distribution in the molten metal and a high dissolution rate [8,13,14]. Due to these advantages, chromium- and manganese-containing ligatures are widely used in the production of steels of various grades—from structural to heat-resistant and stainless—applied in critical industrial sectors.

The scientific novelty and the aim of the study lie in the development of a technology for producing chromium–manganese ligature through the combined utilization of domestic low-grade chromium and iron–manganese ores with the application of a new silicon–aluminum ferroalloy as a reductant. Unlike conventional production of separate ferroalloys (ferrochromium and ferromanganese), the proposed aluminosilicothermic technology makes it possible to simultaneously introduce chromium and manganese into steel, which significantly reduces production costs, energy consumption, and material usage. The resulting chromium–manganese ligature has a wide range of applications in steelmaking and can be further processed into specialized alloys, including Fe–Cr–Mn stainless steels [15], thereby giving the study high practical significance and a unique export potential. The objective of this work is the scientifically substantiated development of an efficient method of metallothermic smelting of chromium–manganese alloy with the production of material of a predetermined chemical composition and with high recovery of target components. Particular attention is paid to the processing of low-grade domestic ores characterized by high impurity content and low metallurgical potential, which necessitates the implementation of innovative technological solutions to ensure stable reduction of elements and consistent quality characteristics of the final product. Under the conditions of the Republic of Kazakhstan, which possesses significant but largely underutilized reserves of chromium and manganese ores, the development of such technologies is of particular relevance and opens up prospects for expanding the raw material base and enhancing the efficiency of the national ferroalloy industry [16,17,18,19,20,21,22,23,24,25,26].

One of the key aspects in developing a technology for producing chromium–manganese ligature is the rational selection of reductants that ensure efficient reduction of oxides and high quality of the final product. Silicon–aluminum-containing ferroalloys such as AlSiMn, FeSiAl, and FeSiCr dust have proven to be effective reductants, combining high reactivity with relatively low cost. Their application not only reduces energy consumption and improves the thermodynamic stability of the process but also broadens the possibilities for utilizing local mineral and technogenic raw materials.

The reductants used in this study, FeSiAl and AlSiMn, were obtained with the use of high-ash coal. For the first time, the possibility of obtaining such silicon–aluminum alloys based on cheap Kazakh coal with an ash content of 54–63% was demonstrated and implemented in studies carried out by researchers of the Zh. Abishev Chemical-Metallurgical Institute. Within these works [27] (pp. 14–17), FeSiAl was produced using coals from the Ekibastuz coal basin, while AlSiMn was obtained by reducing low-grade manganese ores with the same carbonaceous materials. These approaches enable the efficient utilization of local technogenic and mineral resources in metallurgy, thereby reducing dependence on imported reductants [28,29,30]. In addition, an auxiliary reductant in the present study is FeSiCr dust, generated during the crushing and processing of ferroalloys at the Aksu Ferroalloy Plant. According to production monitoring data, the crushing of FeSiCr produces on average 8–10% of dust fraction by mass of the final product [31]. This dust contains a significant amount of reducing components, making it a potentially valuable technogenic raw material.

In earlier preliminary stages of the research, the authors [32] obtained results of thermodynamic modeling as well as laboratory smelting experiments in a Tamman furnace using FeSiCr dust as a reductant. As a result of these experimental melts, a metallic alloy and slag with stable physicochemical characteristics were produced. The chemical composition of the obtained metal included the main elements Cr, Mn, Fe, and Si in corresponding concentrations. Structural–phase analysis by SEM, performed by the authors [32], revealed the presence of intermetallic compounds in the metallic phase based on Cr–Fe–Si and Mn–Si systems. These findings confirmed the possibility of efficient reduction of chromium and manganese from oxides using FeSiCr dust and the simultaneous alloying of the metal with silicon.

In continuation of the previously conducted studies, the present work involves thermodynamic analysis and laboratory smelting experiments in a Tamman furnace using AlSiMn and FeSiAl as reductants. The purpose of these experiments is to evaluate the reducing ability of these materials in the production of chromium–manganese alloy. To determine the optimal smelting parameters, thermodynamic modeling is applied, which serves as a modern tool for predicting the behavior of multicomponent systems. It is based on the fundamental laws of physics and chemistry and allows for the quantitative assessment of energy and phase transformations occurring during chemical reactions [33,34]. Particular attention in this work is paid to analyzing the mechanism of combined metallothermic reduction of chromium and manganese oxides within the complex multicomponent Fe–Cr–Mn–Si–Al–Ca–Mg–O system. This approach is essential for understanding the sequence and competitiveness of reduction reactions between various oxide compounds and the active components of the reductants—primarily silicon and aluminum [35]. Considering potential phase transformations involving calcium, magnesium, and other elements, it becomes possible to determine the most probable pathways for the formation of metallic and slag phases [36]. Based on the results of calculations and laboratory experiments, large-scale smelting trials in a 100 kVA refining electric furnace are planned under three technological schemes: using AlSiMn, FeSiAl, and FeSiCr dust as reductants. Such a comprehensive approach will provide a substantiated comparative assessment of the effectiveness of the reductants and will make it possible to establish the optimal conditions for producing chromium–manganese ligature from low-grade raw materials.

2. Materials and Methods

2.1. Preparation of Charge Materials

In the present study, domestic ores and reductants were used as the main charge components. Chromium ore from the Kempirsai deposit located in the Khromtau district of the Aktobe region served as the primary source of chromium, while the iron–manganese ore obtained from the Kerege-Tas deposit in the Zhanaarka district of the Karaganda region acted as the main source of manganese. As reductants, the previously described silicon–aluminum ferroalloys were applied, which are characterized by high reactivity and availability in Kazakhstan. The experimental work was carried out according to three charge composition variants with different reductants, allowing a comparative assessment of their efficiency in smelting chromium–manganese ligature. A detailed scheme of the experimental series is presented in Figure 1.

The scheme (Figure 1) illustrates three variants of charge compositions employed for the smelting of chromium–manganese ligature. These variants are based on combinations of chromium ore and iron–manganese ore with different types of reductants (AlSiMn, FeSiAl, and FeSiCr dust). In all cases, lime was additionally introduced as a fluxing agent to regulate slag formation, reduce slag viscosity, and improve the overall melting conditions. As shown in the scheme, regardless of the selected variant, the final outcome is the production of chromium–manganese ligature, which demonstrates the universality of the approach and the feasibility of achieving the same target product through different combinations of raw materials and technological routes.

The chemical composition of the initial ores and reductants is presented in

Table 1. Chemical composition of the initial charge materials.

Material	Content, %
	Cr2O3	Fe2O3	SiO2	Al2O3	MgO	CaO	P2O5	S
Chrome ore	40.49	12.03	11.10	8.99	28.29	0.65	0.0059	0.013
Material	Content, %
	Mntot	Fe2O3	SiO2	Al2O3	MgO	CaO	P2O5	S
Iron–manganese ore	26.62	21.78	16.74	2.57	0.15	2.34	0.43	0.17

and

Table 2. Chemical composition of the reductants.

Materials	Content, %
	Cr	Mn	Fe	Si	Al	C	S	P
AlSiMn	-	29.04	9.32	48.39	8.55	0.20	0.020	0.180
FeSiAl	-	-	34.00	48.62	10.82	-	0.010	0.024
FeSiCr dust	24.10	-	14.18	32.22	1.51	2.48	0.049	0.018

, serving as the baseline data for evaluating the role and influence of each charge component on the composition and quality of the final alloy. Such an approach makes it possible to compare the efficiency of different reductants and to identify the optimal charge design for smelting chromium–manganese ligatures.

According to the data in Table 2, all investigated reductants contain high concentrations of active reducing elements, primarily silicon and aluminum. In addition, they are characterized by low levels of harmful impurities (S, P), which makes them suitable for the production of high-quality ferroalloys.

2.2. Thermodynamic Calculation

In the present study, a phase analysis of the multicomponent Fe–Cr–Mn–Si–Al–Ca–Mg–O system was performed using thermodynamic data contained in the HSC Chemistry 10 database. This database forms part of a comprehensive software package designed for modeling chemical and metallurgical processes and is regularly updated in accordance with the standards of SGTE (Scientific Group Thermodata Europe), ensuring the reliability of the underlying thermodynamic parameters.

According to the literature [37,38,39], HSC Chemistry calculations typically result in high accuracy—often within a few percent—making it a reliable and widely recognized tool for addressing both scientific and applied problems in metallurgy. The software is extensively used in research practice, academic training, and industrial applications for performing equilibrium state calculations, evaluating thermodynamic stability of compounds, predicting phase transformations, and optimizing technological processes [40,41,42,43].

For determining the equilibrium phase composition, the Equilibrium Compositions module was employed. This module makes it possible to simulate in detail the behavior of system components under specified thermodynamic conditions, including temperature, pressure, and initial chemical composition of the charge. It allows the calculation of the quantitative distribution of elements between coexisting phases (metal, slag, and gas), which is particularly important for predicting the structure and properties of smelting products.

To identify the most stable state of the system, the GIBBS algorithm was applied, which determines equilibrium on the basis of minimizing the total Gibbs free energy. The use of this method makes it possible not only to evaluate the conditions of phase formation but also to trace the course of chemical reactions, the stability of oxide and metallic compounds, and the influence of temperature factors on reduction processes. Such an approach provides a reliable and accurate assessment of the thermodynamic conditions that control the formation of the target alloy and by-products in high-temperature metallurgical processes.

During the thermodynamic analysis, the following parameters were set for modeling the Fe–Cr–Mn–Si–Al–Ca–Mg–O system using AlSiMn and FeSiAl as reductants:

• Temperature regime. Calculations were carried out at 1400 °C, 1600 °C, and 1800 °C, which made it possible to perform a comparative analysis of the system behavior and to determine the most favorable conditions for element reduction, phase formation, and the stability of oxides and intermetallic compounds.
• Pressure. In all modeling cases, the pressure of the system was taken as 0.1 MPa, corresponding to the standard physical atmosphere [44,45]. This assumption ensures comparability with real metallurgical processes performed under near-atmospheric pressure.
• Volume. The system volume was determined by the thermodynamic parameters and the chemical composition of the components. A uniform distribution of all substances among the phases (metal, slag, and gas) was assumed, which is typical for equilibrium modeling.
• System type. The system was considered closed, i.e., without mass transfer or heat exchange with the external environment. This approach makes it possible to focus exclusively on the internal chemical and thermodynamic interactions, excluding external kinetic influences.
• Amount of reductant. The effect of reductant dosage was simulated in the range of 10 to 100 kg with an increment of 10 kg. Such variation allowed the evaluation of the degree of chromium and manganese reduction, as well as tracking the changes in the equilibrium phase composition of smelting products depending on the reductant input. The chemical composition of the initial charge mixture used as input data for thermodynamic modeling in HSC Chemistry is given in

  Table 3. Composition of the initial charge mixture, kg.

  No.	Cr2O3	Mn2O3	Fe2O3	SiO2	Al2O3	MgO	CaO	Fe	Si	Al	Mn
  1	39.86	-	11.84	10.93	8.85	27.85	0.64	0.98	5.08	0.90	3.05
  								1.96	10.16	1.76	6.09
  								2.93	15.23	2.69	9.14
  								3.91	20.31	3.59	12.19
  								4.89	25.39	4.49	15.24
  								5.87	30.47	5.38	18.28
  								6.85	35.54	6.28	21.33
  								7.82	40.62	7.18	24.38
  								8.80	45.70	8.07	27.42
  								9.78	50.78	8.97	30.47
  2	19.93	23.21	19.13	15.61	5.98	14.08	1.74	3.64	1.16	5.20	-
  								7.28	10.41	2.32	-
  								10.92	15.61	3.47	-
  								14.55	20.81	4.63	-
  								18.19	26.02	5.79	-
  								21.83	31.22	6.95	-
  								25.47	36.42	8.11	-
  								29.11	41.63	9.26	-
  								32.75	46.83	10.42	-
  								36.39	52.03	11.58	-

  .

In the thermodynamic modeling, the following compounds are considered as associates:

-

metallic phase: Cr₅Si₃, FeSi, Fe, MnSi, Fe₃Si, Cr, Mn₃Si, Fe₅Si₃, Mn, CrSi, Mn₅Si₃, CrSi₂, Cr₃Si, Si, FeSi₂, Al, CaSi, CaSi₂, Mg, Al₂Ca, Ca₂Si, Al₄Ca, Mg₂Si, CaMg₂.

-

slag phase: SiO₂, Mn_0.9554Ca_0.0446SiO₃, Mn₂O₃, Fe₂O₃, Mn₂SiO₄, MnO₂, MnO, Cr₂O₃, MnSiO₃, CaSiO₃, Fe₂MnO₄, Mn₃O₄, CaO*Al₂O₃*2SiO₂, Al₂O₃, MnO*Al₂O₃, MnO*Fe₂O₃, Fe₃O₄, Cr₂FeO₄, MgCr₂O₃, (CaFe)_0.5SiO₃, Fe_0.945O, Fe_0.947O, FeO, CaAl₂SiO₆, CaO*Fe₂O₃, FeSiO₃, FeAl₂O₄, MgSiO₃, CaO*Cr₂O₃, CaO*Al₂O₃*SiO₂, FeO_1.056, (CaMg)_0.5SiO₃, *2CaO*SiO₂, MgO₂, CaMgSi₂O₆, CaO*Al₂O₃, CaO*MgO*2SiO₂, MgO*Al₂O₃, Ca₃Si₂O₇, CaO*MgO*SiO₂, MgFe₂O₄, *3CaO*2SiO₂, *2CaO*Al₂O₃*SiO₂, MgO, CaFe(SiO₃)₂, CaO, *3Al₂O₃*2SiO₂, *2FeO*SiO₂, CaMgSiO₄, FeO*SiO₂, CaO*2Al₂O₃, Fe₂MgO₄, Ca₃Fe₂Si₃O₁₂, *2CaO*MgO*2SiO₂, CrO₃, Mg₂SiO₄, *2CaO*Fe₂O₃, CrO₂, Ca₃SiO₅, Al₂O₃*2SiO₂, *3CaO*Al₂O₃*3SiO₂, *3CaO*MgO*2SiO₂, CaO*MgO, *3CaO*SiO₂, Ca₂MgSi₂O₇, Al₄Mg₂Si₅O₁₈, *2CaO*Al₂O₃, Mg₂Al₄Si₅O₁₈, Fe₃Al₂Si₃O₁₂, CaO*6Al₂O₃, *3CaO*Al₂O₃, Fe₂A_l4Si₅O₁₈, CaCrO₄, Mg₃Al₂Si₃O₁₂, MgCrO₄, MgMn₂O₄, Cr₂MgO₄, MgCr₂O₄, CaFeSiO₄.

2.3. Experimental Smelting

Based on the thermodynamic data and the physicochemical properties of the charge materials considered above, a series of laboratory experiments were carried out in a Tamman furnace (Figure 2). The purpose of these experiments was not only to determine the optimal temperature regime for the reduction processes but also to obtain experimental samples of chromium–manganese ligature under controlled laboratory conditions.

The Tamman furnace is a high-temperature laboratory unit designed for simulating and studying metallurgical processes under controlled conditions. The working chamber of the furnace consists of a cylindrical graphite tube, which simultaneously serves as both the heating element and the reaction zone due to the high electrical conductivity and thermal stability of graphite. Temperature control is carried out using a precision thyristor voltage regulator [46,47], connected to the primary winding of a step-down transformer. This configuration provides the supply of a high electric current—up to several thousand amperes—to the furnace electrodes at a low voltage in the range of 0.5 to 15 V.

The specified parameters ensure uniform and efficient heating of the graphite tube due to its electrical resistance, thereby creating stable thermal conditions throughout the working zone. The furnace is capable of reaching operating temperatures in the range of 1800–2000 °C with a maximum heating rate of up to 25 °C per minute. Precise temperature control inside the furnace is carried out using a high-temperature tungsten–rhenium thermocouple (WRe-5/20), enclosed in a protective alumina tube, which shields the sensor from the aggressive environment inside the furnace [48,49,50].

Such a design makes the Tamman furnace particularly suitable for conducting experimental smelting, reduction processes, and alloy production, especially under small-scale metallurgical research conditions where high precision of temperature control is required [49]. The ability to model high-temperature metallothermic reactions with reproducible parameters allows for the evaluation of phase formation, metal recovery degree, and slag behavior under realistic conditions. As a result, the furnace is an important tool for verifying thermodynamic models and optimizing technological process parameters.

Figure 3 shows a preliminary scheme of smelting carried out in the Tamman furnace. As can be seen, the entire process includes the stages of preliminary heating, achieving thermal stability, holding at the maximum temperature, and subsequent cooling until the crucible is removed. The total duration of smelting was about 170 min, including active heating at a rate of ~25 °C/min, holding at a temperature of about 1600 °C for 20 min, as well as the stage of controlled cooling. Characteristic reduction reactions involving silicon and aluminum begin at temperatures above 1200 °C.

Based on the obtained thermodynamic data and the results of preliminary laboratory smelting experiments in the Tamman furnace, a large-scale laboratory resmelting was carried out in a refining electric furnace with a rated capacity of 100 kVA (Figure 4). This stage of the research was intended to serve as a transition from small-scale modeling to conditions approaching industrial practice, thereby enabling the validation of the theoretically optimized parameters for metal reduction and phase formation. The primary objective of these experiments was not only to confirm the feasibility of the predicted thermodynamic trends but also to examine the behavior of the charge materials under prolonged exposure to high temperatures, to identify the optimal range of operational parameters, and to assess the stability of reduction reactions in a more representative metallurgical environment. For these purposes, the charge composition was prepared to match the proportions used during the laboratory-scale trials in the Tamman furnace, ensuring the possibility of direct comparison of results. The raw materials included low-grade chromium and manganese ores, while the reducing agents consisted of ferrosilicochrome dust, ferrosilicoaluminum, and alumosilicomanganese alloys, identical to those previously applied during the modeling and bench-scale experiments. Such consistency of charge composition was necessary to guarantee the reliability of scaling-up conclusions and to establish correlations between laboratory findings and large-scale smelting behavior.

The refining furnace used for this experimental series was specifically designed to withstand the thermal and chemical conditions required for high-temperature reduction smelting. Its construction includes two self-baking graphite electrodes, each with a diameter of 75 mm, which were mounted in electrode holders capable of controlled vertical movement. This arrangement provided stable regulation of the arc length and ensured reliable energy transfer into the furnace bath, thereby maintaining steady smelting conditions throughout the experimental campaign. The inner working zone of the furnace was lined with refractory bricks based on magnesite, which imparted excellent thermal resistance, chemical inertness, and structural stability during prolonged high-temperature operation. Such lining not only protected the furnace shell from thermal stresses but also minimized unwanted reactions with molten slag and metal. To facilitate the removal of products, the furnace design was equipped with a taphole, through which the liquid metallic and slag phases could be tapped in a controlled manner after the completion of smelting. The overall furnace configuration, therefore, provided a reliable experimental platform for simulating large-scale industrial smelting processes within a controlled laboratory environment, while enabling systematic observation of reduction dynamics, phase equilibria, and the efficiency of the selected reducing agents.

2.4. Phase and Microstructural Characterization

The phase composition of the obtained chromium–manganese ligature was determined by XRD using a DRON-2 diffractometer equipped with a copper anode (Cu Kα, λ = 1.5418 Å). The diffraction patterns were recorded in the 2θ range from 10° to 90° with a scanning step of 0.05°, which provided the required accuracy for qualitative phase analysis.

For a more detailed assessment of the alloy morphology and the distribution of elements in the microstructure, microstructural and elemental characterization was performed using the SEM “ZEM20” (ZEPTOOLS, Tongling City, China). The microscope was equipped with an energy-dispersive X-ray spectroscopy (EDS) system, which enabled the acquisition of high-resolution microstructural images and the execution of local elemental analysis of the studied area.

3. Results and Discussion

The DRON-2 X-ray diffractometer was employed to carry out XRD analysis of the initial charge materials—chromium ore and iron–manganese ore. According to the XRD results, the mineral composition of the chromium ore is represented by the following phases: ferrochromite (FeCr₂O₄), hematite (Fe₂O₃), spinel (MgCr₂O₄), silicon oxide (SiO₂), iron aluminate (FeAl₂O₄), magnetite (Fe₃O4), and chromium oxide (Cr₂O₃). In turn, the iron–manganese ore is characterized by the presence of MnO, Mn₃O₄, MnFe₂O₄, Fe₂O₃, SiO₂, and Al₂O₃ compounds. Based on the obtained diffractograms (Figure 5 and Figure 6), it can be concluded that both ores are polymineral in nature and contain not only oxides but also complex spinel-type phase compounds.

Thermodynamic modeling of the process of producing chromium–manganese ligature was carried out using the HSC Chemistry software package. As the initial components, low-grade chromium ore and iron–manganese ore were included in the model, with their mineral (X-ray phase) composition preliminarily established on the basis of XRD analysis results. As reducing agents, FeSiAl and AlSiMn dust were introduced into the calculation system in amounts ranging from 10 to 100 kg per 100 kg of the ore mixture. The modeling covered temperature points of 1400 °C, 1600 °C, and 1800 °C, which made it possible to trace the influence of temperature regime and reducing agent consumption on the reduction degree of Cr and Mn oxides, as well as on the formation of the target metallic phase.

The modeling results made it possible to trace the phase distribution of elements at different temperatures and reductant dosages, including the formation of the metallic phase. The obtained data, presented in

Table 4. Results of thermodynamic modeling of the chemical composition of metal and slag (using AlSiMn alloy as a reducing agent).

T = 1400 °C
AlSiMn, kg	Metal, %				Slag, %
	Fe	Cr	Mn	Si	SiO2	CaO	MgO	FeO	Al2O3	Cr2O3
10	51.47	25.75	17.02	0.02	16.93	23.97	27.74	0.56	10.70	27.07
20	32.06	38.77	16.89	0.11	21.44	36.40	24.64	0.12	12.32	10.45
30	25.40	39.30	17.65	3.24	23.55	33.77	22.86	0.02	14.01	8.00
40	23.25	33.06	19.65	9.16	21.08	33.29	22.61	0.01	16.40	8.50
50	21.67	28.28	21.16	14.11	18.51	33.46	21.29	0.00	18.82	9.00
60	20.54	24.86	22.32	17.76	15.99	32.80	18.70	0.00	21.03	9.20
70	19.61	22.16	23.21	20.58	13.52	31.70	18.50	0.00	23.37	9.50
80	18.88	19.81	23.96	22.96	11.14	30.44	18.66	0.00	26.23	9.80
90	18.28	17.96	24.56	24.91	8.36	29.59	18.61	0.00	27.89	10.10
100	17.78	16.00	25.00	26.59	6.16	29.39	21.46	0.00	30.14	10.45
T = 1600 °C
AlSiMn, kg	Metal, %				Slag, %
	Fe	Cr	Mn	Si	SiO2	CaO	MgO	FeO	Al2O3	Cr2O3
10	45.87	34.65	19.46	0.02	15.83	23.88	23.50	1.10	10.50	25.18
20	28.45	52.11	19.33	0.11	19.97	36.84	20.91	0.26	12.11	9.92
30	22.54	54.18	20.20	3.08	21.82	44.67	19.43	0.04	13.79	0.25
40	20.65	45.73	22.53	11.08	19.52	45.05	19.22	0.02	16.18	0.00
50	19.24	39.41	24.26	17.09	17.16	45.24	19.05	0.00	18.56	0.00
60	18.25	34.63	25.58	21.54	14.83	45.41	18.88	0.00	20.89	0.00
70	17.45	30.89	26.62	25.03	12.54	45.57	18.72	0.00	23.17	0.00
80	16.79	27.89	27.46	27.86	10.30	45.73	18.56	0.00	25.41	0.00
90	16.25	25.42	28.15	30.19	8.11	45.89	18.40	0.00	27.61	0.00
100	15.79	23.35	28.73	32.12	5.98	46.05	18.23	0.00	29.74	0.00
T = 1800 °C
AlSiMn, kg	Metal, %				Slag, %
	Fe	Cr	Mn	Si	SiO2	CaO	MgO	Cr2O3	Al2O3	MnO
10	42.80	56.35	0.78	0.08	15.15	27.27	22.70	20.36	10.95	2.04
20	27.30	69.34	2.01	1.35	20.60	37.08	21.91	2.47	14.13	3.47
30	23.65	58.40	4.88	13.07	19.61	35.31	22.59	0.03	18.25	4.07
40	21.06	47.60	10.32	21.02	18.17	32.71	23.64	0.00	22.95	2.49
50	19.37	40.10	14.01	26.52	16.50	29.70	24.80	0.00	28.10	0.89
60	18.23	34.99	15.60	31.15	14.26	25.67	26.02	0.00	33.72	0.32
70	17.65	31.47	15.74	35.11	11.84	21.32	27.10	0.00	39.54	0.20
80	16.70	28.12	17.07	38.06	8.75	15.75	28.78	0.00	46.64	0.08
90	16.15	25.64	17.55	40.58	5.63	10.13	30.28	0.00	53.92	0.04
100	15.72	23.60	17.97	42.55	2.63	4.74	31.58	0.00	61.03	0.02

and

Table 5. Results of thermodynamic modeling of the chemical composition of metal and slag (using FeSiAl alloy as a reducing agent).

T = 1400 °C
FeSiAl, kg	Metal, %				Slag, %
	Fe	Cr	Mn	Si	SiO2	CaO	MgO	Al2O3	Cr2O3	FeO
10	52.11	2.74	45.15	0.00	19.68	35.42	10.52	6.19	15.10	4.56
20	43.07	4.51	52.42	0.00	25.77	46.38	9.56	7.14	10.66	0.49
30	50.43	7.89	41.65	0.03	27.33	49.19	8.37	7.58	7.50	0.03
40	52.37	9.82	34.90	2.91	26.95	48.52	8.61	9.15	6.77	0.01
50	42.83	20.91	24.76	11.49	26.16	47.09	8.74	10.65	7.37	0.00
60	42.16	18.20	21.55	18.09	25.76	46.37	9.03	12.44	6.40	0.00
70	41.63	16.11	19.06	23.20	25.14	45.26	9.26	14.22	6.11	0.00
80	41.18	14.44	17.09	27.29	24.39	43.90	9.47	16.03	6.22	0.00
90	40.82	13.09	15.49	30.60	23.60	42.48	9.69	17.92	6.30	0.00
100	40.52	11.97	14.16	33.35	22.79	41.01	9.92	19.91	6.37	0.00
T = 1600 °C
FeSiAl, kg	Metal, %				Slag, %
	Fe	Cr	Mn	Si	SiO2	CaO	MgO	Al2O3	Cr2O3	FeO
10	46.56	3.69	49.71	0.03	19.39	34.90	8.19	6.07	14.78	8.92
20	49.25	8.83	41.89	0.04	26.01	46.82	8.18	7.20	10.39	1.40
30	43.56	24.40	29.12	2.93	29.84	53.71	7.98	8.28	0.10	0.09
40	42.71	20.88	24.72	11.69	29.25	52.65	8.16	9.92	0.00	0.03
50	42.06	18.17	21.51	18.26	28.57	51.43	8.34	11.64	0.00	0.01
60	41.51	16.10	19.05	23.34	27.86	50.15	8.54	13.44	0.00	0.00
70	41.03	14.46	17.12	27.39	27.12	48.81	8.75	15.32	0.00	0.00
80	40.61	13.14	15.55	30.71	26.34	47.40	8.97	17.29	0.00	0.00
90	40.23	12.04	14.25	33.48	25.52	45.93	9.20	19.35	0.00	0.00
100	39.87	11.13	13.16	35.84	24.66	44.38	9.45	21.51	0.00	0.00
T = 1800 °C
FeSiAl, kg	Metal, %				Slag, %
	Fe	Cr	Mn	Si	SiO2	CaO	MgO	Al2O3	Cr2O3	FeO
10	51.16	7.23	41.55	0.05	26.17	47.10	13.88	8.16	19.73	13.86
20	62.44	12.93	24.57	0.07	37.40	67.32	13.92	10.36	14.30	2.87
30	52.01	29.12	15.26	3.61	45.03	81.06	13.92	12.55	0.26	0.30
40	49.75	24.36	12.31	13.59	43.33	77.99	13.92	14.74	0.01	0.11
50	48.14	20.80	10.26	20.80	41.38	74.49	13.92	16.93	0.00	0.04
60	46.91	18.16	8.74	26.19	39.40	70.93	13.92	19.11	0.00	0.02
70	45.94	16.12	7.56	30.38	37.42	67.36	13.92	21.29	0.00	0.01
80	45.16	14.48	6.62	33.73	35.45	63.81	13.91	23.46	0.00	0.01
90	44.52	13.15	5.86	36.47	33.49	60.28	13.91	25.62	0.00	0.00
100	43.99	12.04	5.22	38.74	31.54	56.77	13.91	27.78	0.00	0.00

, allow for the evaluation of the influence of temperature and reductant amount on the completeness of oxide reduction and the formation of the target alloy.

As a result of thermodynamic modeling of the reduction process using the AlSiMn alloy (Table 4), the influence of temperature (1400–1800 °C) and reductant consumption (10–100 kg) on the distribution of the main elements between the metal and slag phases was established. At the initial stage of 1400 °C, the reduction of chromium from its oxide phase remains incomplete. According to thermodynamic modeling, between 10 and 27% of Cr₂O₃ persists in the slag phase, indicating only partial transfer of chromium from the ore into the metal. Under these relatively low-temperature conditions, manganese and iron are reduced much more effectively and form the main constituents of the metallic phase. As a result, the alloy composition reaches up to 25% Mn and about 50% Fe. Silicon, in turn, is more intensively introduced into the alloy at higher additions of AlSiMn due to the active reduction of SiO₂, which increases its concentration to approximately 26.6% Si.

When the temperature is raised to 1600 °C, the reduction reactions proceed much more completely and evenly. Chromium is almost fully reduced, with only a residual fraction of Cr₂O₃ not exceeding 0.25% left in the slag. Manganese and iron also undergo efficient reduction and transfer almost entirely into the metallic phase. The most balanced chemical composition of the alloy is obtained at an AlSiMn consumption of 30–40 kg, where the alloy contains 45–54% Cr, 20–23% Mn, and 20–22% Fe. At the same time, the silicon concentration remains moderate at 3–11%, which is technologically acceptable and ensures the required properties of the chromium–manganese alloy.

Under high-temperature conditions of 1800 °C, chromium is reduced completely, and no residual Cr₂O₃ is observed in the slag. However, the elevated temperature leads to a new limiting factor—intensive evaporation of manganese. This phenomenon causes a sharp decrease in its concentration within the alloy, dropping to as low as 0.78–1.53% at minimal reductant additions. Simultaneously, the enhanced reduction of SiO₂ occurs, which results in a significant increase in silicon concentration, reaching 26–27% Si. Such changes substantially affect the alloy composition and must be carefully considered when determining the optimal technological regime for industrial-scale smelting.

The charge mixture in the temperature range of 1400–1800 °C and at a reducing agent consumption of 10–100 kg of FeSiAl alloy (Table 5) was investigated by means of detailed thermodynamic modeling. The purpose of this analysis was to evaluate the distribution of the main components between the metallic and slag phases under various conditions. At a relatively low temperature of 1400 °C, the degree of chromium reduction into the metallic phase was incomplete: on average, only about 85–90% of chromium passed into the alloy, while a significant portion of 8–12% remained bound in the slag phase as Cr₂O₃. Under such conditions, the produced metal became notably enriched in manganese (up to 45–50% Mn) and iron, which largely determined the chemical composition of the alloy.

When the temperature was increased to 1600 °C and the FeSiAl alloy consumption was optimized at 30 kg, the most favorable balance of phase distribution and chemical composition was observed. In this regime, chromium, manganese, and iron were almost completely reduced, with virtually no transfer of these elements into the slag. At the same time, the silicon content in the metallic phase remained at a relatively low level (approximately 2.9% Si), which ensured the required structural and physicochemical properties of the resulting chromium–manganese alloy.

At the highest temperature of 1800 °C, chromium was reduced fully into the metallic phase; however, the excessive thermal conditions led to intensive evaporation of manganese. The losses of this element amounted to about 10–15%, which resulted in a noticeable decrease in its concentration in the alloy. Therefore, despite the positive effect of high temperature on chromium recovery, the simultaneous manganese volatilization must be taken into account when developing and selecting the optimal technological regime for industrial smelting.

Based on thermodynamic calculations, the extraction of metals into the metallic phase was evaluated at the optimal charge composition and a temperature of 1600 °C. Figure 7 show the dependence of recovery on reductant consumption (10–100 kg). The analysis indicates that the most favorable regime, for both AlSiMn and FeSiAl alloys, is achieved at 1600 °C with about 30 kg of reductant (the area highlighted by the green dashed line in Figure 7). Under these conditions, chromium and manganese are almost completely transferred into the metallic phase, while silicon remains at an acceptable level, ensuring the required alloy properties. The modeling was performed for a closed system, which isolates the intrinsic chemical transformations of the charge but requires caution when applying the results to industrial processes.

Based on the results of thermodynamic modeling, two experimental smelting runs of chromium–manganese ligature was carried out at a temperature of 1600 °C. The total weight of each charge mixture was 100 g, with the ratio between the ore component, the reductant, and the fluxing additive (CaO) selected according to the results of preliminary calculations. This ensured the maximum possible degree of reduction of Cr, Mn, and Fe, minimized the formation of silicide phases, and promoted the formation of slag with the desired basicity.

In the first variant, the charge mixture consisted of chromium ore, AlSiMn alloy (used as the reductant), and CaO as the flux. In the second variant, a combined ore was used—chromium ore together with ferromanganese ore; the reductant in this case was FeSiAl alloy, also with the addition of CaO. Prior to smelting, all charge mixtures were thoroughly homogenized manually in a porcelain mortar and then loaded into alumina crucibles.

The smelting was performed in the Tamman furnace with holding at 1600 °C for 20 min, which ensured the completion of reduction processes and the formation of metallic and slag phases. Upon completion, the crucibles were removed and cooled in air to room temperature. Figure 8 shows the external appearance of the products obtained after smelting—chromium–manganese ligature and the corresponding slag produced using different reductants.

As can be seen in Figure 8, the metallic and slag phases are clearly separated. It should be noted that during smelting no intensive gas release was observed, which indicates a stable course of the reduction processes. The resulting slag was characterized by a solid, stone-like structure, evidencing its high density and low porosity. In all smelting variants, the slag-to-metal ratio was close to 2.

As a result of the experimental smelting tests in the Tamman furnace, metallic alloys with different chemical compositions were obtained depending on the reductant used. When AlSiMn alloy was applied, the chemical composition of the metal was: Fe—22.20%, Cr—53.00%, Mn—20.40%, Si—4.40%. When FeSiAl alloy was used as the reductant, the metal composition was: Fe—41.84%, Cr—25.73%, Mn—27.49%, Si—4.66%. In addition, when FeSiCr dust was applied, the resulting alloy had the following chemical composition: Fe—34.58%, Cr—21.96%, Mn—38.85%, Si—4.52%, which was obtained in a previous study [32].

Based on the obtained data, further large-scale laboratory smelting experiments were carried out in a 100 kVA refining electric furnace. The smelting was performed according to three different charge compositions, similar to those previously tested under laboratory conditions. Prior to the start of the process, the furnace was preheated for 5 h using coke as the heating material. This approach ensured gradual and uniform heating of the lining and the reaction zone. Upon completion of the preheating stage, the coke was completely removed from the working area, which prevented its influence on the composition and thermodynamics of the charge. After that, the charge materials were manually loaded layer by layer in accordance with the thermodynamically calculated proportions of reductant, ore, and flux.

The electrical parameters of the process were maintained at an operating current of 80–90 A and a voltage of 18–24 V, which ensured stable reduction reactions and uniform temperature distribution throughout the smelting volume. The electrodes were deeply immersed into the reaction zone, promoting efficient heat transfer and the formation of a stable melt zone. The smelting was carried out in a semi-continuous mode, with periodic tapping of molten metal and slag every 1.5–2 h. After each tapping, samples were taken for subsequent chemical and phase analysis. The results of the analysis of the metallic and slag phases are presented in

Table 6. Chemical composition of the products from experimental heats.

No.	Metal, %						Slag, %
	Fe	Cr	Mn	Si	P	S	CaO	SiO2	MgO	Al2O3	Cr2O3	MnO	FeO	P
with AlSiMn alloy (as a reducing agent)
1	21.07	55.47	19.84	3.58	0.03	0.02	44.55	28.23	15.81	8.44	1.23	0.95	0.78	0.01
2	21.77	54.89	19.90	3.40	0.03	0.02	44.44	27.96	15.96	8.70	1.06	0.72	1.15	0.02
3	22.46	54.30	19.97	3.23	0.03	0.02	44.85	27.89	15.71	8.75	1.51	0.66	0.60	0.02
4	23.15	53.73	20.03	3.05	0.03	0.02	44.92	28.05	15.81	8.44	1.23	0.95	0.57	0.02
5	23.83	53.16	20.10	2.88	0.03	0.02	44.78	27.67	16.02	8.70	1.15	0.35	1.31	0.01
6	24.50	52.59	20.16	2.71	0.03	0.02	44.27	27.77	15.87	8.50	1.60	0.96	1.01	0.02
7	25.17	52.03	20.22	2.54	0.03	0.02	44.10	28.24	16.01	8.56	0.96	1.15	0.96	0.02
with FeSiAl alloy (as a reducing agent)
8	39.44	27.49	27.27	5.75	0.03	0.01	56.36	27.24	7.40	7.03	0.92	0.40	0.62	0.02
9	40.31	26.89	26.27	6.46	0.04	0.03	54.98	27.69	7.45	6.85	1.26	0.94	0.82	0.01
10	41.19	26.30	27.29	5.17	0.04	0.02	55.74	27.33	7.29	7.23	1.22	0.94	0.24	0.01
11	42.04	25.72	27.29	4.90	0.04	0.03	56.39	27.86	7.37	7.14	0.37	0.66	0.21	0.01
12	42.88	25.15	27.32	4.60	0.04	0.02	55.53	27.85	7.00	7.44	1.34	0.56	0.26	0.02
13	43.71	24.59	27.32	4.34	0.03	0.01	55.80	27.52	7.35	7.22	0.85	0.46	0.79	0.02
14	44.52	24.03	27.30	4.10	0.03	0.02	55.11	27.45	7.35	7.14	1.29	0.93	0.73	0.01
with FeSiCr dust (as a reducing agent)
15	35.48	21.42	38.78	4.28	0.02	0.01	61.26	33.67	-	1.87	1.15	1.67	0.20	0.18
16	35.24	20.64	40.94	3.15	0.02	0.01	59.30	34.54	-	2.34	1.89	1.62	0.30	0.00
17	34.35	22.54	39.72	3.37	0.02	0.01	59.99	34.88	-	1.70	1.46	1.52	0.43	0.02
18	32.38	21.52	42.72	3.36	0.01	0.01	59.30	34.70	0.33	1.81	1.87	1.69	0.00	0.30
19	34.81	19.81	39.87	5.45	0.04	0.01	59.71	33.32	0.41	2.40	1.76	2.02	0.39	-
20	35.28	21.96	38.27	4.45	0.04	-	59.93	34.83	-	2.00	1.11	1.60	0.54	-
21	33.61	22.29	38.45	5.63	0.02	-	60.09	34.20	0.36	1.72	1.46	1.94	0.00	0.22

.

To evaluate the efficiency of each reducing agent, a series of experimental smelting tests were carried out in a refining electric furnace. For each variant of the charge composition, seven smelting runs were performed, amounting to a total of 21 melts. All experiments were conducted under identical conditions, with a stable electrical regime and a fixed dosage of components. After each run, samples of both the metallic and slag phases were taken, and the product yields were recorded.

The analysis of the data presented in Table 6 is of considerable significance for elucidating the mechanisms governing the formation of chromium–manganese ligature composition during bath reduction reactions, as well as for addressing applied tasks related to the production of chromium–manganese ferroalloys from low-grade chromium and iron–manganese ores using complex silicon–aluminum reductants. In addition, the relationship between the concentrations of Cr, Mn, and Si in the metal and the basicity of the slag was examined (Figure 9).

Figure 9 illustrates the dependence of the concentrations of the main elements (Cr, Mn, and Si) in the metallic phase on the slag basicity (CaO + MgO)/(SiO₂ + Al₂O₃) when using different types of reductants (AlSiMn, FeSiAl, and FeSiCr dust). The comparative analysis of regression equations and determination coefficients shows that, although certain weak tendencies can be noted for individual elements, the overall effect of slag basicity within the studied range (1.6–1.8) on the chemical composition of the chromium–manganese ligature is insignificant.

(a)

The behavior of Cr (~50–55%), Mn (~20%), and Si (~3–4%) demonstrates almost complete independence from the slag basicity. The regression slopes are close to zero, and the coefficients of determination (R² < 0.001) confirm the absence of a meaningful correlation. This indicates that, under these conditions, the alloy composition is practically unaffected by variations in slag basicity, reflecting the stability of the reduction process when AlSiMn is used.

(b)

In contrast, when FeSiAl is employed as a reductant, chromium and silicon show a slight positive trend, while manganese exhibits a more noticeable increase with basicity, as reflected by the regression coefficient (R² = 0.33). Although this correlation is not strong, it may suggest a partial sensitivity of Mn to slag conditions, which can be attributed to changes in crystallization dynamics and local redistribution of elements during smelting.

(c)

A different pattern is observed for FeSiCr dust. In this case, manganese content decreases slightly with increasing basicity (R² = 0.21), whereas chromium shows a moderate positive correlation (R² = 0.38). Silicon content remains practically stable (R² ≈ 0.006). Such tendencies may be linked to the interaction between slag components and alloying elements, particularly the preferential reduction of chromium over manganese under more basic slag conditions.

In summary, the analysis confirms that the effect of slag basicity on the composition of the chromium–manganese ligature is limited. While certain element-specific trends are observed depending on the type of reductant used, the low values of determination coefficients indicate that slag basicity is not a dominant factor in controlling the distribution of Cr, Mn, and Si. These findings highlight the robustness of the smelting process and the stability of the alloy composition across different reductants, thereby supporting the reproducibility of the proposed technology for producing chromium–manganese ligature.

The main parameters during the melting of chromium–manganese alloy in a 100 kVA refining furnace are presented in

Table 7. Smelting parameters of chromium–manganese ligature in a 100 kVA refining furnace under three charge composition variants.

Raw Charge Materials	Material Consumption, kg
	I	II	III
Chromium ore	98.0	49.0	-
Iron–manganese ore	-	49.0	84.0
AlSiMn alloy	35.0	-	-
FeSiAl alloy	-	35.0	-
FeSiCr dust	-	-	42.0
Lime	77.0	77.0	84.0
Average chemical composition of the metal, %
Fe	23.14	42.01	34.45
Cr	53.74	25.74	21.45
Mn	20.03	27.15	39.82
Si	3.06	5.05	4.24
Ptot	0.03	0.04	0.05
S	0.02	0.02	0.01
Mass of the obtained metal, kg	71.11	65.03	65.35
Average chemical composition of the slag, %
SiO2	27.97	27.56	34.30
CaO	44.55	55.70	59.94
MgO	15.88	7.32	0.15
Al2O3	8.58	7.15	1.97
MnO	0.82	1.04	1.27
Cr2O3	1.24	0.70	1.52
FeO	0.91	0.52	0.26
Ptot	0.01	0.01	0.10
Slag basicity	1.66	1.64	1.66
Mass of the obtained slag, kg	135.12	143.06	141.2
Slag-to-metal ratio	1.90	2.19	2.16

. These data reflect the technological regime and the quality characteristics of the obtained alloy.

This table summarizes the results of three experimental smelting variants using different reducing agents. When employing the AlSiMn alloy (Variant I), the metal composition was: Fe—23.14%, Cr—53.74%, Mn—20.03%, Si—3.06%. With the addition of the FeSiAl alloy (Variant II), the composition was: Fe—42.01%, Cr—25.74%, Mn—27.15%, Si—5.05%. In the case of FeSiCr dust (Variant III), the composition was: Fe—34.45%, Cr—21.45%, Mn—39.82%, Si—4.24%. The average slag basicity (CaO + MgO)/(SiO₂ + Al₂O₃) in all three variants remained nearly constant, within the range of 1.64–1.66, indicating stable slag-forming conditions. As a result of the three experimental heats, a total of 201.49 kg of chromium–manganese ligature and 419.43 kg of slag were obtained. The slag-to-metal ratio was 2.08. Figure 10 shows the release process during tapping, while Figure 11 presents the appearance of the obtained metal and slag after the experimental smelting runs.

The tapping was stable, with the metal showing good fluidity and the slag being discharged evenly. The observed behavior confirms the suitability of the chosen charge composition.

The obtained metallic and slag phases were well separated. The slag detached as a compact mass, did not crumble, and exhibited a dense, stony structure, which indicates normal shrinkage and sufficient fluidity during the smelting process. For further investigation of the structural and phase characteristics of the produced chromium–manganese ligature, one sample was selected from each series of experimental heats with different reducing agents. Each selected sample corresponded to a chemical composition close to the average value for the respective reducing agent. The collected samples were subjected to XRD and SEM analyses. The results of the XRD study of the chromium–manganese ligature, which provide insight into its phase composition, are presented below in Figure 12, Figure 13 and Figure 14.

As can be seen from the XRD results of the metallic samples obtained from the 3rd, 11th, and 16th smelting runs using different reducing agents (AlSiMn, FeSiAl, and FeSiCr dust, respectively), all samples exhibit a largely similar phase composition, with only minor variations in the positions and intensities of the diffraction peaks. This similarity indicates that, regardless of the reductant applied, the smelting process leads to the formation of a comparable crystalline structure in the alloy. In all cases, the primary phase was identified as a solid solution of α-(Fe,Cr,Mn) with a body-centered cubic (BCC) lattice. The stability of this phase suggests the formation of a uniform, single-phase metallic matrix predominantly composed of iron, chromium, and manganese, which serve as the fundamental structural components of the ligature.

In addition to the main solid solution, weak reflections corresponding to intermetallic compounds FeSi and Cr₅Si₃ were detected in the diffraction spectra. Their presence can be attributed to the alloying levels of silicon and chromium within the system, which tend to form secondary intermetallic phases under specific smelting conditions. Although their intensity is relatively low, these peaks confirm the incorporation of silicon into the metallic phase, reflecting its chemical activity and interaction with chromium and iron.

Slight variations in the interplanar spacings and peak intensities observed in the samples from different smelting runs can be explained by local differences in the chemical composition of the charge, the kinetics of crystallization, and the thermophysical environment of the furnace. These variations, however, remain within narrow limits and do not alter the general phase composition of the ligature, which highlights the reproducibility of the reduction process under the studied conditions.

For a more detailed investigation of the morphology and distribution of alloying elements in the obtained chromium–manganese ligature, a microstructural analysis was performed on the metallic sample selected for XRD. Prior to SEM observation, the specimens were subjected to standard metallographic preparation: they were cut to the required size, polished to a mirror-like surface, and subsequently etched to reveal the microstructure and grain boundaries. After preparation, the samples were carefully cleaned and dried, which ensured clear and informative imaging. Figure 15, Figure 16 and Figure 17 present the SEM images of the studied ligatures along with the corresponding elemental distribution maps (

Table 8. Content of major elements in different spectra (based on EDS analysis).

Spectra, No.	Content, Mass. %
	Fe	Cr	Mn	Si
1	48.12	7.15	39.14	5.59
2	40.35	18.96	35.24	5.45
3	43.12	6.38	40.00	10.50
4	30.21	33.67	30.51	5.61
5	36.45	17.32	41.36	4.87
6	42.30	15.17	37.88	4.65
7	53.20	17.50	20.00	9.30
8	34.90	13.57	46.28	5.25
9	39.61	21.43	34.18	4.78
10	42.51	16.94	37.14	3.41
11	52.89	6.29	25.67	15.15
12	34.56	28.40	25.03	12.01
13	18.73	42.91	35.00	3.37
14	40.95	19.08	25.89	14.08

).

Based on the EDS analysis results presented in Table 8 and the SEM images (Figure 15, Figure 16 and Figure 17), the microstructure of the obtained ligature was evaluated. The structural examination was carried out at magnifications up to 50 nanometers, which made it possible to observe in detail the elemental distribution and the surface morphology. In total, 14 spectra were analyzed, covering different areas of the surface. Spectra 1–4 correspond to the alloy obtained using the AlSiMn reductant. Spectra 5–10 relate to the alloy produced with the FeSiAl reductant. Spectra 11–15 represent the microstructure formed during reduction with FeSiCr dust.

The obtained data showed that the main elements—Fe, Cr, Mn, and Si—are generally uniformly distributed across the surface, indicating a sufficient level of component mixing. Minor fluctuations in Fe and Cr content were observed in certain spectra, which may be associated with microheterogeneity of the structure. In addition, small pores were present on the surface, likely related to residual products of ore preparation or specific features of the technological process.

4. Conclusions

Thermodynamic modeling of the reduction processes of chromium- and manganese-bearing ores using HSC Chemistry demonstrated that, at a reductant consumption of 30 kg per 100 kg of charge, both AlSiMn and FeSiAl alloys ensure a high degree of reduction of the main alloying elements, with effective extraction of Cr, Mn, and Fe into the metallic phase. Crucible smelting in a high-temperature Tamman furnace confirmed the efficiency of the selected charge and reductants.

Large-scale laboratory smelting in a 100 kVA refining electric furnace (21 runs in total: seven for each reductant—AlSiMn, FeSiAl, and FeSiCr dust) verified the correctness of the thermodynamic modeling and demonstrated the applicability of the proposed technology for producing chromium–manganese ligature. The resulting alloys were characterized by chemical analysis, XRD, and SEM.

The microstructural examination of the obtained metal revealed a single-phase metallic matrix based on a solid solution of α-(Fe,Cr,Mn) with a BCC lattice. Minor inclusions of FeSi and Cr₅Si₃ intermetallic compounds were also detected, which are associated with the presence of alloying amounts of Si and Cr. EDS mapping confirmed that Fe, Cr, Mn, and Si are uniformly distributed across the metallic surface, indicating sufficient mixing of the components during smelting.

The average chemical compositions of the obtained ligatures were as follows: with AlSiMn—Fe 23.14%, Cr 53.74%, Mn 20.03%, and Si 3.06%; with FeSiAl—Fe 42.01%, Cr 25.74%, Mn 27.15%, and Si 5.05%; and with FeSiCr dust—Fe 34.45%, Cr 21.45%, Mn 39.82%, and Si 4.24%. In all cases, the slag basicity remained within 1.64–1.66, confirming stable slag-forming conditions.

These results validate the proposed approach, confirm the feasibility of obtaining chromium–manganese ligature from low-grade ores using complex silicon–aluminum reductants, and provide detailed insight into its phase composition and microstructural features.