Browsing by Author "Salpagarov, Eldar"

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DFG 465144480: Boron-free self-glazing Al₂O₃-C refractories
(Technische Universität Bergakademie Freiberg, 2026-04-01) Roungos, Vasileios; Gehre, Patrick; Salpagarov, Eldar; Aneziris, Christos G.
Al₂O₃-C refractories are extensively used as functional components in the continuous casting of steel. These high-duty products such as submerged entry nozzles, ladle shrouds, and monoblock stoppers contain up to 30 wt.-% carbon and present excellent mechanical, thermal and chemical properties, enabling the cost- and quality-effective implementation of the continuous casting process. Ceramic glazes are externally applied on Al₂O₃-C flow control refractory products to protect carbon from oxidation. These glazes typically contain boron. However, the increasing requirements for clean steel technology along with environmental- and health issues associated with boron compounds will make the utilization of boron-free glazes a necessity in the upcoming years. New boron-free self-glazing Al₂O₃-C formulations with sodium carbonate, wollastonite and magnesia additives were developed with the assistance of the FactSage software tool. These compositions presented a softening point in the range of 1000-1100 °C for self-glaze formation, which is the typical preheating temperature range for Al₂O₃-C functional refractory products. In addition, the influence of particle packing on their oxidation resistance was investigated, based on established particle size distribution models.
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GRK 2802: Interaction of Ladle Slag With Varying SiO2 Content and Recyclate-Based MgO–C Refractories
(Technische Universität Bergakademie Freiberg, 2026-09-23) Yehorov, Anton; Salpagarov, Eldar; Mospan, Anhelina; Stadtmüller, Till Manon Jannis; Schemmel, Thomas; Aneziris, Christos G.; Volkova, Olena
Industrial MgO–C refractories fabricated from either pure fuzed magnesia (R0) or 50 wt% recycled MgO–C (R50) were exposed to ladle slags (C/A = 1) with varying SiO2 content (1–20 wt%). Wetting and infiltration behaviors were investigated using the sessile drop method at 1600°C under an Ar atmosphere for different dwell times. Quenched slag–refractory interfaces were characterized by SEM-EDX and compared with phase equilibrium simulations using FactSage 8.1. Increasing SiO2 content at 1600°C reduced slag density and surface tension, increased viscosity, and shifted saturation from MgO to MgAl2O4 spinel. During heating, R50 samples exhibited more intense gas formation. This delayed wetting and significantly slowed the initial stage of slag infiltration. Upon contact with recycled-based refractories, the high-SiO2 slag formed a dense, 195 μm-thick MgAl2O4-rich layer, entrapping residual calcium-silicate slag and serving as an in situ protective barrier against further oxidation and corrosion. These results demonstrate that well-processed MgO–C recyclate can inhibit slag attack, first by delaying infiltration via transient gas release, and subsequently by promoting a protective spinel layer under suitable slag compositions. Furthermore, the findings highlight the influence of substrate carbon content and open porosity on the slag’s melting and infiltration behavior.
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GRK 2802: Thermophysical Properties of the Desulphurization Slags With Various CaS and CaO/Al2O3 Ratio
(Technische Universität Bergakademie Freiberg, 2026-09-25) Salpagarov, Eldar; Bellé, Matheus Roberto; Yehorov, Anton; Richter, Julia; Volkova, Olena
Low sulphur content is essential for high-quality steels and can be achieved by using desulphurization slag. During the desulphurization process the chemical composition of the slag changes leading to alteration in its thermophysical properties, such as surface tension, viscosity, and density. However, the influence of CaS on these thermophysical properties is poorly investigated nowadays. In this study, the influence of various CaS content (0-10 wt%) and CaO/Al2O3 ratio (1.87-1.36) on the viscosity, surface tension, and density of desulphurization slags is investigated. Measurements of surface tension and density are carried out using the maximum bubble pressure method, while viscosity is determined using the rotating bob method. The obtained results show that a decrease in viscosity value is observed with an increase in CaS content only up to 6 wt%, however, further addition of CaS sharply increases viscosity. In case of surface tension and density measurements, an increase in CaS content up to 10 wt% results in a reduction of both property values. Additionally, to study microstructure differences of the investigated slags, they were quenched and examined using Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX).
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GRK2802: Non-metallic Inclusion Evolution in Interaction of Al-killed Mn-B Steel with Desulfurization Slag and MgO-C Refractories Containing Environmentally Friendly Binders and Recyclates
(Technische Universität Bergakademie Freiberg, 2026-05-20) Bellé, Matheus Roberto; Neubert, Lukas; Yehorov, Anton; Kerber, Florian; Gunasekar, Dinesh Kumar; Salpagarov, Eldar; Aneziris, Christos G.; Volkova, Olena
The high-temperature interaction between Al-killed Mn-B steel, desulfurization slag, and carbon-bonded magnesia refractories containing conventional, environmentally friendly binders and recyclate systems was systematically investigated using finger immersion testing at 1600 °C for 30 minutes. Chemical analysis of steel and slag, combined with SEM/EDX characterization of refractory/steel/slag interfaces and non-metallic inclusions (NMIs), was performed to interpret reaction mechanisms and the evolution of inclusions. Significant slag modification occurred during testing, characterized by MgO enrichment, CaO and Al2O3 depletion, and the formation of Fe- and Mn-bearing oxides. In the steel, pronounced decarburization, sulfur increase, boron depletion, and enhanced oxygen and nitrogen contents were observed, indicating reoxidation and interfacial reactions. Independent of refractory condition, MgAl2O4 spinel and Ca2SiO4 phases were detected in the infiltrated refractory zone. Refractories containing recyclates and alternative binders chemically modified the inclusion population and significantly increased NMI number density, particularly Mn-Si-Ti-based inclusions. The results demonstrate that refractory composition strongly influences slag chemistry, inclusion characteristics, and steel cleanliness. These findings provide a new understanding of refractory-slag-steel interactions during secondary metallurgy and highlight the need for optimized slag/refractory formulations to ensure inclusion control and steel quality under increasingly sustainable material strategies.