Slag Samples Research Articles

Effect of ZnO/EAF slag doping on removal of methyl red dye (MR) from industrial waste water

Zinc oxide doped with EAF slag (ZnO/ EAF slag) nanoparticles in different contents (10, 20) % of waste were synthesized in a controlled and reproducible way using spin-coater. The produced nanomaterial’s physicochemical and structural characteristics were ascertained by means of particle size distribution, TEM, SEM, UV-Vis spectroscopy, XRD, FTIR, and XRF. The role and effect of EAF slag with constant percent doping with ZnO on the ability to remove pollutants was determined by observing the methyl red (MR) elimination in an aqueous solution at λmax = 413 nm and MR dye removal concentration was evaluated from its optical density. Irradiation of the compounds in sunlight intensity 250 KW/nh.m2 and temperature 36 °c resulted in a larger degree of MR removal from the solution, resulting in ZnO/EAF slag samples exhibiting increased photo activity. As a conclusion ZnO nanoparticles saturated with 20% EAF slag as a waste material were the most efficient in removing methyl red (MR) achieving ~ 96% removal and a completely transparent solution after 2 h of testing.

Validated kinetic modelling of ladle furnace process for predicting inclusions in API steel grade

A kinetic model of ladle furnace (LF) process is developed in C++ format using the FactSage database and ChemApp subroutines. The model considers all the process parameters such as ferroalloy and slag dissolution, wire additions, electrical arcing, steel/slag reactions, reoxidation due to slag eye opening, heat exchange between metal/slag, and refractory dissolution. Further, a correlation for inclusion removal rate was developed as a function of argon flow rate, using discrete phase method (DPM) in Computational Fluid dynamics (CFD). Lollypop samples from steel bath and slag samples were collected from the plant for API steel grade for chemical analysis and inclusion characterisation. At LF_in, the inclusions found were mostly alumina spinel with very low amount of Mg (∼3%), followed by spinel at intermediate stage having ∼15 wt. % of Mg and after Ca treatment, inclusions transformed into CaS and Calcium Aluminate type of inclusions. Overall inclusion weight fraction varied from 136 ppm at LF_in to 93 ppm at LF_out. The model calculations were found to give very good prediction for steel and slag chemistry, and inclusion global composition as compared to the plant results. Predicted temperature was found with an accuracy of ± 5 oC, while the calculated inclusion weight fraction was having an accuracy of ±12 ppm.

Structural Changes in Copper Slags During Slow Cooling

The objects of the study were converter slags from the Balkhash copper plant in their initial state and after heat treatment. Using mineralogical and X-ray phase analysis, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA), it was found that the initial converter slag and its thermally treated samples have identical matrices with almost complete coincidence in mineral and phase compositions. The distinguishing feature is the quantitative ratio of mineral components in the slag mass. Almost all of the iron is oxidized and present in the form of fayalite, magnetite, and magnetite, with other elements (silicon, copper, zinc, and aluminum) incorporated into its lattice. The structure of all slag samples indicates an association of sulfur exclusively with copper. Copper in the slags was identified in both metallic and sulfide forms. Slow cooling of the converter slag after its remelting contributes to the reduction in the sulfide–metal suspension in the volume of the melt and its coarsening. During slow cooling, structural changes occur not only in the main oxide part of the slag but also in the polymetallic globules.

Determination of the Redox Ratio of Iron in a Diamagnetic Matrix Using Low-Field NMR Relaxometry.

Proton nuclear magnetic resonance (NMR) relaxometry is proposed to determine the iron redox ratio of slag samples. It depends on the paramagnetic effect on bulk water relaxation times. Experiments have been carried out to calibrate the relationship between the concentration of Fe3+ and Fe2+ ions and the measured relaxation times on prepared standard samples. It is shown that Fe2+ ions have very different effects on the relaxation times than Fe3+ ions. For the solid slag samples, digestion in an acid was used to produce solutions with a pH of 1.0. Hydrogen peroxide (H2O2) was then added to the digested samples to oxidize Fe2+ ions to Fe3+ ions. The concentration of Fe2+ and Fe3+ ions in solution can be calculated by measuring the relaxation times before and after oxidation. The Fe3+/∑Fe ratio of slag samples was also investigated by wet chemistry and 57Fe Mössbauer spectroscopy and calculated by FactSage at the equilibrium state. The results obtained from different methods are consistent, indicating that this NMR relaxometry method is reliable.

Slag Inclusions in Iron Artifacts from Cemeteries at Kichigino I and Krasnaya Gorka, and the Metallurgy of the Early Iron Age Itkul Culture

Silicate slag inclusions in iron artifacts from the Trans-Urals and in iron slags from sites of the Itkul culture were analyzed to assess the geochemical characteristics of iron ore sources exploited during the Early Iron Age. Slag inclusions were found in 19 out of 25 samples from Kichigino I and Krasnaya Gorka. For comparison, we used 12 iron slag samples from Early Iron Age and medieval sites near Lake Irtysh and from Zotino mine. Via statistical analysis, four geochemical groups were separated, each including one or more Kichigino artifacts, which suggests a variety of iron ore sources used by the nomads. Slags and artifacts of the first group are associated with infiltration-sedimentary ironstone ores of the Middle Trans-Urals. Smithing slag from the Itkul site of Shatanov V suggests that these ores were already smelted in the Early Iron Age. The fact that group 1 includes only one artifact from Kichigino I demonstrates that the nomads of the Southern Trans-Urals obtained iron mainly from other sources. Group 2 is characterized by a higher content of Mn and sometimes Ba and S in inclusions. This may attest to the use of Fe-Mn ironstone associated with barite-polymetallic deposits of Central Kazakhstan. Group 3 shows an elevated content of CaO and MgO, indicating the use of ironstone from platform carbonate strata. In the fourth group, the content of K2O is high, and that of MnO, low.

Stay with the green: New insights into ancient copper smelting in the Tonglüshan site, China

This paper presents new archaeometallurgical analyses from the Tonglüshan site, a famous ancient mining and smelting site in China. Results show that the primary phases in slag samples from two sites (Sifangtang and Lujia’nao) are all of a vitreous matrix, interspersed with fayalite crystals, wüstite, and hercynite. The trapped metallic particles in the slag are mainly raw copper with few sulfides present, which indicates a direct reduction process of oxidic ore. Iron-rich minerals were likely to be added as flux implied by the few unreacted inclusions in the slag samples. The extremely low copper content in the slag samples demonstrates a high rate of copper recovery, indicating that the copper smelting technology in the region had reached a considerably advanced level. In the meantime, the variations in metal content in slag samples from different periods reveal the diachronic changes in this copper smelting technology. The Tonglüshan site, with its millennia of ancient mining and metallurgical activities, provides an excellent material base for detailed studies on technological evolution.

Replacement of conventional aggregates and fillers with steel slag and palm kernel shell ash in dense-graded asphalt mixtures

Large quantities of steel slag and palm kernel shell ash (PKSA) – waste products from steel production and palm oil milling, respectively – are generated annually in several countries, and their disposal is challenging. Meanwhile, the over-reliance on conventional rock aggregates for asphalt mixture production poses increasing sustainability challenges. This study investigated the potential of entirely replacing granite aggregates with steel slag and PKSA in a dense-graded asphalt mixture. Two sets of asphalt mixtures were prepared; the control mixture contained crushed granite aggregate and hydrated lime, while the other set incorporated steel slag as coarse aggregate and PKSA as fine aggregate and filler. Both mixture types utilized AC-30 viscosity-graded asphalt binder. The properties of the waste materials met the quality standards required for aggregates in asphalt mixture production. Both mixture types were designed according to the Marshall design procedure and were evaluated for durability (Cantabro abrasion loss), fatigue cracking Resistance, rutting Resistance, and moisture damage susceptibility. The Cantabro abrasion loss test indicated that the waste-based mixture was 3% less durable than the control. However, the cracking Resistance of the waste-based mixture was approximately twice that of the control. Even though the rapid rutting test indicated that the control mixture was slightly superior in rutting Resistance, the Marshall quotient suggested otherwise. Both mixture types exhibited similar moisture damage resistance. Overall, the steel slag and PKSA samples have shown high potential to replace virgin granite aggregates and lime in asphalt mixtures fully and are, thus, recommended for field performance evaluation and possible adoption.

Thermal activation of basic oxygen furnace slag as a heterogeneous catalyst in transesterification: Characterization and catalytic activity studies

The valorization of industrial by-products has garnered significant attention in recent years due to its potential to enhance sustainability and economic efficiency within various sectors. Basic Oxygen Furnace slag (BOF-S), a by-product generated in the steelmaking process characterized by its complex composition, presents an opportunity for waste management and resource recovery. This study investigates the potential of BOF-S as a catalyst in converting waste cooking oil to biodiesel via the transesterification reaction. To improve its efficiency, BOF-S was calcined at 850 °C (BOF-S 850), and 1000 °C (BOF-S 1000), for 5 h. The BOF-S was characterized using XRF, N2 sorption, XRD, TGA-DSC, SEM-EDS and FTIR. The characterization techniques showed that the BOF-S 850 had superior characteristics as a catalyst: rough surface, increased pore size and more active basic sites compared to the BOF-S and the BOF-S 1000 slag samples. The transesterification reaction was conducted at a methanol: oil ratio of 20:1, a catalyst loading of 20 wt %, a reaction time of 12 h, a reaction temperature of 60 °C, and a stirring speed of 750 rpm. The findings established that the BOF-S 850 was the best catalyst, with a 90.77 % biodiesel yield and was able to sustain a maximum of two transesterification cycle runs.

Experimental Determination of Slag Emissivities for Enhanced Slag Control by Infrared‐Based Systems

For today's high‐quality steel production, good control of slag composition is essential in secondary steelmaking. However, the conventional slag analysis practice, involving sampling, sample preparation, and analysis, is very time‐consuming. This work is the first step toward an investigation of infrared (IR)‐based systems and can be used for online slag composition monitoring using the principle that different slag compositions have different emissivities in the IR wavelength range. Therefore, this work experimentally determines emissivity values of slags as a function of composition at steelmaking temperature, since available data for slags are very limited in the literature. The emissivities of three different slag compositions belonging to the Al2O3–CaO–SiO2–MgO system are investigated at 1773 K. The investigated emissivities are in the range of 0.75–0.87, with the best repeatability seen in the slag which is fully liquid at 1773 K. Variations in emissivities are observed within the other slags due to the presence of solid phases. Although the data clearly indicate a difference of emissivities as a function of slag composition, further experiments must be performed to evaluate the emissivities of other characteristic slags at different temperatures in order to further assess the applicability of IR‐based systems for slag composition control.

Gaps in predicting water quality impacts of unbound air-cooled blast furnace slag utilized for roadway construction

Air-cooled blast furnace slag (ACBFS) is often used as road construction aggregate. Several incidences of adverse environmental effects have been reported in Indiana where unbound slag has been used. The aggregates that caused issues in the field had been previously approved for use by passing State of Indiana standard slag leaching procedures. The study goal was to test several hypotheses posed to the Indiana Department of Transportation and authors by the industry about slag leaching, and to better understand water quality impacts. Ten slags from two suppliers underwent leaching procedures adopted by two U.S. states, but additional test procedures and material and leachate chemical characterization were also conducted to better interpret results. Aggregates varied in size and age (24 h to 2 years old). Like prior literature reports, the chemical composition among the slag samples was similar. However, water quality impacts observed at the bench-scale in this study differed substantially across the slags. Results were consistent with those previously reported at Indiana field sites, but not with literature reported results from standardized leaching tests (i.e., TCLP, percolation, etc.). In the present study, no relationship was found between slag age and leachate composition. Leachate pH, conductivity, and color levels exceeded thresholds of regulatory and aquatic toxicity significance. For one slag, leachate pH reached 12.9, but the effluent was colorless. During both stagnation and rinsing tests, aqueous chloride, sulfate, and zinc concentrations sometimes exceeded regulatory water quality and aquatic toxicity levels. Repeated rinsing of the slag resulted in water conductivity and sulfate concentration differences. To better understand and predict the impacts of unbound ACBFS, additional fundamental studies and field investigations are recommended. Unbound ACBFS is not recommended for use near environmentally sensitive areas, drinking water sources, habituated areas, and where it may have water contact (i.e., waterways, wetlands, reservoirs, and groundwater).

Thermodynamic modelling of liquid steel tapping process to predict carryover slag amount

Control of carryover slag is essential during transfer of liquid steel from basic oxygen furnace to ladle to maintain preferred steel cleanliness. Carryover slag is oxidising in nature and its higher amount will lead to higher refractory wear rate, low alloy recovery and increased secondary steelmaking treatment time. Measuring the amount of carryover slag is essential for evaluating current tapping practices and implementing necessary precautions when needed. In the present study, a kinetic process model has been developed using FactSage macro processing code. Steel lollipop and slag samples were collected between tapping start and onset of ladle refining process for a medium carbon aluminium killed grade. Liquid steel-slag interaction, flux addition to slag, various metallic additions to steel and refractory dissolution to slag were taken into account in the model. Multiple simulations were performed with varying amounts of carryover slag and composition of steel and slag of initial samples from the ladle furnace were equated with the predicted values from FactSage kinetic model to determine the carryover slag amount. Apart from predicting the carryover slag amount, this model can be useful to understand the effect of tapping parameters on variations in liquid steel and slag chemistry during tapping.

Fluid Dynamics Studies on Bottom Liquid Detachment from a Rising Bubble Crossing a Liquid–Liquid Interface

The detachment regimes and corresponding detachment height of lower liquid from a coated bubble during the bubble passage through an immiscible liquid–liquid interface were studied. High-speed imaging techniques were used to visualize the lower liquid detachment from a rising bubble near the interface. Analysis of industrial slag samples by a scanning electron microscope (SEM) was also carried out. The results indicate that the detachment height of lower liquid from a rising bubble showed a distinct correlation to penetration regimes. Bubble size and a fluid’s physical properties exerted a significant influence on the detachment height of the lower liquid. The detachment height for medium bubbles (Weber number: 4~4.5; Bond number: 2.5~7.5) varied significantly with increasing bubble size, which contributes to the lower liquid entrainment in the upper phase due, significantly, to the higher detachment height and large entrainment volume. The maximum detachment height for large bubbles is limited to approximately 100 mm due to the early detachment with the liquid column at the interface though large bubbles transporting a larger volume of lower liquid into the upper phase.

The influence of the composition and origin of ash and slag waste from coal generation on the response of organisms used in biotesting

Introduction. Different conditions of origin of ash and slag wastes has a significant impact on their final properties. Material and methods. The work is devoted to the search and establishment of dependencies of the influence of the origin of ash and slag waste on their chemical and biological parameters by a comprehensive assessment of the results of the impact of ash and slag waste on the vital signs of hydrobionts. Results. The values of the responses of hydrobionts for ash and slag wastes formed from coals of various origins were investigated. The component composition of aqueous extracts from the studied ash slag samples was evaluated. The dependences of the influence of the conditions of origin of ash and slag wastes on their final chemical and biological properties were established. Limitations. An assessment of the biological and chemical properties of ash and slag waste generated during the combustion of coal from six different deposits was carried out. The total volume was 95 samples. Conclusion. Ash and slag wastes formed from the burning of brown coals have the most pronounced toxic effect on hydrobionts, unlike ash and slag from coal.

Reducing carbonation degradation and enabling CO2 sequestration in alkali-activated slag using cellulose nanofibers

This study evaluated the role of cellulose nanofibers (CNF) in reducing the carbonation degradation of alkali-activated slag (AAS) samples. AAS samples prepared with different dosages of CNF (0 %, 0.10 %, and 0.80 % by weight of the binder) were exposed to natural and accelerated carbonation for up to 90 days. The effects of carbonation on the microstructure of AAS paste samples were monitored using FTIR, XRD, TGA, MIP, and BSE/SEM. It was observed that after 90 days of natural carbonation, the control batch exhibited a reduction in compressive strength, whereas the CNF batches showed an enhancement. Notably, the CNF-containing batches maintained consistent strength over time, with no reduction in strength. Similarly, after 90 days of accelerated carbonation, CNF 0.10 % and CNF 0.80 % showed an increase in compressive strength compared to the control batch. Despite this enhancement in compressive strength, microstructural studies indicated that the addition of CNF increased the extent of carbonation, leading to a higher amount of CaCO3 formation and C–S–H/C-A-S-H decalcification compared to the control batch. The beneficial effects of CNF on the strength despite increased C–A–S–H decalcification are attributed to their reinforcing effects and the ability to form composites with CaCO3.

Evaluating the efficacy of biogeochemical cover system in mitigating landfill gas emissions: A large-scale laboratory simulation.

Municipal solid waste (MSW) landfills are a significant source of methane (CH4) emissions in the United States, contributing to global warming. Current landfill gas (LFG) management methods, like the landfill cover system and LFG collection system, do not entirely prevent LFG release. Biocovers have the potential to reduce CH4 emissions through microbial oxidation. However, LFG also contains carbon dioxide (CO2) and trace hydrogen sulfide (H2S) depending on waste composition, temperature, moisture content, and age of waste. An innovative biogeochemical cover (BGCC) was developed to tackle these concerns. This cover comprises a biochar-based biocover layer overlaid with a basic oxygen furnace (BOF) steel slag layer. The biochar-based biocover layer oxidizes CH4 emissions, while the BOF slag layer reduces CO2 and H2S through carbonation and sulfidation reaction mechanisms. The BGCC system's field performance remains unexamined. Therefore, a large-scale tank setup simulating near-field conditions was developed to evaluate the BGCC system's ability to mitigate CH4, CO2, and H2S from LFG simultaneously. Synthetic LFG was passed through the BGCC in five distinct phases, each designed to simulate the varying gas compositions and flux rates typical of MSW landfill. Gas profiles along the depth were monitored during each phase, and gas removal efficiency was measured. After testing, biocover and BOF slag samples were extracted to analyze physico-chemical properties. Batch tests were also conducted on samples extracted from the biocover and BOF slag layers to determine potential CH4 oxidation rates and residual CO2 sequestration capacity. The results showed that the BGCC system's CH4 removal efficiency decreased with higher CH4 flux rates, achieving its highest removal (74.7-79.7%) at moderate influx rates (23.9-25.5g CH4/m2-day) and reducing to its lowest removal (27.4%) at the highest influx rate (57.5g CH4/m2-day). Complete H2S removal occurred during Phase 3 in the biocover layer of BGCC system. CH4 oxidation rates were highest near the upper (277.9µg CH4/g-day) and lowest in the deeper region of the biocover layer. In the tank experiment, CO2 breakthrough occurred after 156days due to drying of the BOF slag layer, with an average residual carbonation capacity of 46 gCO2/kg slag after moisture adjustment. Overall, the BGCC system effectively mitigated LFG emissions, including CH4, CO2, and H2S, at moderate flux rates, showing promise as a comprehensive solution for LFG management.

Physico-chemical characterization of cupola slag: Enhancing its utility in construction

Cupola slag is a waste material of the steel and iron industries. Its composition is determined by the cupola furnace and other elements used in steel and iron manufacturing. This paper investigates the characterization behavior of various cupola slag materials. As a result, x-ray fluorescence (XRF), x-ray diffraction (XRD), thermogravimetry differential thermal analysis, and scanning electron microscopy (SEM) methods were used to characterize three cupola slag samples from distinct origins. In addition, various physical properties were used to compare different cupola slags. The specific gravity values of CS-1 (cupola slag-1 sample), CS-2 (cupola slag-2 sample), and CS-3 (cupola slag-3 sample) are 1.36, 2.5, and 2.917, respectively. The density and water absorption for CS-1, CS-2, and CS-3 are 1414.86, 1477.71, and 1796 kg/m3, and 0.37%, 0.32%, and 0.26%, respectively. Cupola slag also includes a larger percentage of lime, according to XRF data, which contributes to its improved binding characteristics. A higher calcium oxide content in CS-3 could facilitate the pozzolanic process. The presence of angular particles that aid in material binding is seen in the SEM image. Compounds with a nanostructure are then flawlessly blended into the mixture and grouped with calcium alumina silicates formed by cement hydration. The XRD pattern of cupola slag exhibits high peaks, indicating that the material is crystalline in character and can be utilized as sand. It also shows the presence of other chemical compounds, such as silica, which ranges from 30% to 45%. CS-1 and CS-2 have comparable XRD patterns. However, CS-3 has a somewhat different pattern because of the greater CaO content. Weight loss begins at higher temperatures, which shows that the material is stable at higher temperatures, according to a thermo-gravimetric study. The differential thermal analysis curve of CS-3 indicates that the material remains stable up to a temperature of 600 °C. The physical characteristics of all cupola slag samples show that cupola slag may be utilized to make sustainable building materials because of its lower specific gravity, density, and water absorption.

Enhancement of Sustainable Recycling Systems for Industrial Waste in South Korea via Hazardous Characteristics Analysis

The South Korean government has implemented an acceptance system to promote the high-quality recycling of waste. Industrial waste generators must provide “hazardous characteristics data” to recycling operators. Nonetheless, ~80% of industrial safety accidents in South Korea occur during recycling, most involving fire or explosions. Moreover, a gap in safety management exists during ‘Circular Resource’ acceptance if the target substance is not regarded as waste. In this study collected data on hazardous waste characteristics. From 62 waste generators, 72 waste samples were collected, accounting for most of the resources accepted for recycling, including waste synthetic polymers, slag, dust, waste sand, and waste foundry sand. Then, the hazardous characteristics, as stated in the Ministry of Environment notifications, were assessed. Leaching toxicity was detected in one slag sample and six dust samples. The Cd, Cu, As, Pb, Zn, Ni, Hg, F, and CN levels dissatisfied the Soil Contamination Warning Standard in 31 samples. Explosivity was not detected in any sample, whereas flammability was detected in one waste synthetic polymer sample. The results revealed 15 cases of potential flammability. Flammability is legally defined as below the criteria if the combustion speed criterion is not met. However, in the case of flame ignition, which could cause large fires and safety accidents, the relevant notification should be revised. In this study, we aimed to improve the gap between the hazardous waste management systems and industrial fields through actual measurements of hazardous characteristics. By doing so, we seek to contribute to the prevention of environmental and safety accidents. By continuously accumulating data and utilizing actual measurements, we aim to revise and enhance relevant regulations, ultimately improving the hazardous characteristics of waste management systems.

Influence of the chemical composition of leachates on the results of ecotoxicity tests for different slag types

In this study, four ecotoxicological tests on Vibrio fischeri bacteria, Sinapis alba L. (white mustard), Daphnia magna S. (daphnia's) and earthworms were performed for three types of aqueous slag (ladle, blast furnace and converter) leachates with two-grain sizes (<4 mm, <10 mm). Concentrations of toxic elements and concentrations of Cr(VI), Ca, Na, Al, and other ions were determined. The raw slags were analyzed using X-ray fluorescence spectroscopy (XRFS), and major substances were determined by X-ray powder diffraction (XRD). The aqueous slag leachates passed ecotoxicological tests and met the required criteria, showing no toxicity to Vibrio fischeri and complying with white mustard test criteria. According to the results of the ecotoxicity tests with daphnia, the blast furnace slag samples were not ecotoxic, while two other slag samples were found to be entirely compliant. Characterization of the slags showed that the effect of element/ion leachability and slag grain size is essential. Biplot principal component analysis (PCA) showed that grain size does not significantly affect the separation of individuals on the plane. A positive correlation on toxicity was found with pH, conductivity, calcium content, dissolved content, salinity and fluoride concentration, whereas a negative correlation was found with magnesium concentration, dissolved organic carbon and potassium concentration. The effective concentration at 50% inhibition (EC50) value for Vibrio fischeri correlated with the first dimension of bivariate assessment. In summary, it was found that the investigated slags can be effectively reused as they comply with regulations and do not endanger the environment.

Study of cast iron pots and slags from Salovka I settlement

The article presents the geometric size and shapes of cast-iron pots which were found at the Salovka I settlement in the Upper Sura region. Also the paper reflects the results of studies of one of the fragments of a cast-iron pots, repair plate and slag from the settlement. Slag samples were studied by chemical analysis using methods for the determination the iron content in ores, concentrates and agglomerates. The repair plate and a fragment of the cast iron pot were analyzed using an electron beam spectrograph. In results a noticeable amount of phosphorus was found in the studied samples. This is due to the use of marsh, lake and meadow ores as raw materials for the local ferrous metallurgy. In order to form a statistical database on iron casting and blacksmithing in the Upper Sura basin and other areas, it is necessary to conduct further analytical research.

Щодо взаємодії і захоплення металевих крапель доменним шлаком

The mechanism of capture of metal drops by the slag melt was investigated using blast furnace slag as an example. The role of the viscosity of the blast furnace slag in reducing iron loss at the output from the blast furnace is shown. Reducing the viscosity of slags contributes to the rapid settling of small drops of cast iron in the slag volume. It is noted that the CaO/SiO2 ratio is an important parameter that changes the viscosity of blast furnace slag. To ensure the minimum viscosity of blast furnace slag, it is necessary to establish the optimal chemical composition of the slag, in particular the CaO/SiO2 ratio. A study of the temperature dependence of the viscosity of blast furnace slag melts was carried out using the method of estimating the content of the solid phase in the melt during its cooling. Calculations of the volume fraction of the solid phase for blast furnace slags were performed. An increase in the CaO/SiO2 ratio in slags leads to an increase in their crystallization ability. The microstructure and chemical composition of individual phases of a blast furnace slag sample were studied using scanning electron microscopy (SEM). It was established that the experimental slag contained at least three phases. The main (matrix) phase was an amorphous phase, which contained mainly SiO2 and Al2O3. The volume of the matrix phase contained interspersions of the crystalline phase of different sizes, which mainly included CaO and SiO2. In the volume of the crystalline phase, a metallic phase was found, which consisted mainly of Fe and Mn and had a regular rounded shape. The mechanism of capture of a metal droplet by slag is described. The metal drop serves as a frame (center) for the nucleation of the crystalline phase in the slag volume, as its surface energy decreases at the "metal drop - slag" interface. An increase in the mass of the crystalline phase around the metal drop leads to an increase in its lifting force and capture of the metal drop. Keywords: blast furnace slag, viscosity, metal loss, crystallization, scanning electron microscopy.