Browsing by Author "Gunasekar, Dinesh Kumar"

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Open Access
GRK 2802: MgO-C Ladle Bricks based on Recyclates and Lignin-Collagen-Fructose Binder System
(Technische Universität Bergakademie Freiberg, 2026-09-25) Gehre, Patrick; Gunasekar, Dinesh Kumar; Hubálková, Jana; Aneziris, Christos
Every year, approx. 28 million tons of used refractories accrue worldwide. After their break out, the majority of them are used in subordinate application fields such as aggregates for road construction (downcycling) or deposited in landfills. Their recycling in the field of refractory materials played an underpart so far. For ecological and economic reasons, an increased research potential was identified in the last years consecrated to increasing the recycling rate of refractories and finding new markets and application fields with higher value for them. The study presents current findings of a long-term research training group addressing (amongst others) the development of MgO-C ladle bricks containing MgO-C recyclates and being bonded with pitch- and resin-free environmentally friendly binders. So far, the favored batches contained an oxidic grain fraction composed of 40.5 wt.-% fused MgO raw material, 40.5 wt.-% MgO-C recyclates, 14 wt.-% sintered magnesia (DBM) raw material together with 5 wt.-% graphite and optional antioxidants (TiO2, Al, SiO2). A binder system composed of a mixture of lignin, collagen, and polyethylene glycol (PEG) was developed. The latter served as a pressing aid and was necessary due to the absence of liquid resin in the batch. Even after a considerable and auspicious optimization during previous studies, this basic batch containing recyclates and no pitch or resin does not meet the physical and mechanical properties of standard industrial bricks. Hence, in the present study, the binder system was enhanced by using varying amounts of lignin, collagen, and tannin together with polyethylene glycol, fructose, and citric acid addition. The new developed MgO-C mixtures were pressed uniaxially, dried, cured, and carbonized at 1000 °C. It has been found that polyethylene glycol, which impairs the material properties, can be omitted using sufficient amounts of fructose. The addition of citric acid leads to a further increase in CCS. Consequently, actual optimized environmentally friendly MgO-C batches show a CCS of 85 % of the value of industrial pitch- and resin-bonded bricks without recyclates.
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GRK 2802: Population of Nonmetallic Inclusions in Liquid High-Silicon Electrical Steel in Contact With MgO–C Refractories Based on Recyclates and Environmentally Friendly Binders
(Technische Universität Bergakademie Freiberg, 2026-05-29) Neubert, Lukas; Bellé, Matheus Roberto; Kerber, Florian; Gunasekar, Dinesh Kumar; Weddige, Hans-Jörn; Aneziris, Christos G.; Volkova, Olena
Nonmetallic inclusions (NMIs) are integral constituents of ferrous materials, but almost always have a negative impact on their properties. Therefore, it is best to implement strategies during production to avoid NMIs as much as possible or at least control their formation. To gain a better understanding of these mechanisms, this study investigated the population of nonmetallic inclusions in liquid high-silicon electrical steel (Si 3 mass-%) depending on the contact with different MgO–C refractories. Both conventional refractory materials and those containing MgO–C recyclate and environmentally friendly binder systems, such as collagen, fructose, and lignin, were considered. Immersion tests were carried out for 30min at a temperature of 1600°C in accordance with DIN CEN/TS 15418. Surface phenomena, diffusions reactions, and corrosion mechanisms occurring in the refractory materials were characterized after the tests using SEM and EDX analyses. The change in the chemical composition of the steels was determined using spark spectroscopy, and the NMI population was evaluated after the tests using an automated feature analysis (AFA).
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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.