Browsing by Author "Song, Jinwen"

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GRK2802: Effect of microporous Al2O3-MgAl2O4 content on the thermal shock resistance and molten steel purification performance of β-SiC whisker-reinforced Al2O3-MgAl2O4-C ceramic filters
(Technische Universität Bergakademie Freiberg, 2026-04-27) Song, Jinwen; Yan, Wen; Volkova, Olena; Andrä, Stefan; Bellé, Matheus Roberto; Neubert, Lukas; Tian, Can; Li, Yuanbing
This study investigates the effect of microporous Al2O3-MgAl2O4 content on the phase composition, microstructures, mechanical properties, and purification performance for molten steel of Al2O3-MgAl2O4-C filters, conducted through XRD, SEM, EDS, immersion test with molten steel, and so on. The results indicate that the microporous Al2O3-MgAl2O4 raw material significantly promotes the formation of in-situ β-SiC whiskers within the filters, which intertwine among the particles and grow within the microporous structure, working synergistically with the MgAl2O4 phase to improve the strength and thermal shock resistance. Regarding molten steel purification, on the one hand, the microporous structure of Al2O3-MgAl2O4 particles enhances the filter’s contact area with molten steel, imparting a higher physisorption efficiency to the filter. On the other hand, MgAl2O4 has a greater tendency for carbothermal reactions, generating Mg vapor that has a strong chemisorption capability for [Al], [O], and Al2O3 inclusions in the molten steel. The microporous structure and MgAl2O4 facilitate the formation of a MgAl2O4 reaction layer at the interface during immersion test, contributing to the purification of the molten steel. The filter AM60, prepared with 60 wt% microporous Al2O3-MgAl2O4 powder, not only exhibits excellent thermal shock resistance (with a cold compressive strength of 0.54 MPa and a strength of 0.59 MPa after three thermal shock tests), but also demonstrates a high purification efficiency (reducing inclusions in steel by 68%, and lowering the total oxygen content from 56.3 ppm to 13.5 ppm). Finally, the formation mechanism of in-situ β-SiC whiskers, the role of microporous Al2O3-MgAl2O4 raw material in purification function, and the comprehensive molten steel purification mechanism were proposed.
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GRK2802: Effect of Surface-active Elements on the Wetting Behavior and Surface Tension of Steels: Assessing Sessile Drop and Maximum Bubble Pressure Techniques
(Technische Universität Bergakademie Freiberg, 2026-04-29) Bellé, Matheus Roberto; Neubert, Lukas; Baraka, Abdelrahman A.; Angelini, Alberto; Song, Jinwen; Volkova, Olena
This study investigates the influence of surface-active elements (Si, S, and B) on the surface tension (σ) and wetting behavior of molten steels and provides a direct comparison between the Maximum Bubble Pressure (MBP) and Sessile Drop (SD) measurement techniques. High-silicon electrical steels (ES) (3 - 6 wt% Si) and Mn-B steels (WS) with controlled B and S contents were examined at 1500 - 1650 °C. The results show that the increasing Si content decreases both σ and contact angle, enhancing the wettability on MgO. ES steels exhibit a characteristic parabolic temperature (T) dependence of σ, attributed to Si-O interactions and surface oxidation effects. In WS steels, S reduces σ, and the T coefficient becomes increasingly positive with rising S content. B displays an ambiguous effect: MBP measurements show a slight σ reduction with increasing B, whereas SD measurements indicate the opposite trend. Steel infiltration into porous MgO affects the contact line, causing reduced wetting angles and deviations in SD σ values. Across all compositions and temperatures, SD consistently yields higher σ values than MBP. This discrepancy is primarily linked to surface depletion of volatile species (Mn and S) during SD experiments, while the continuous surface renewal in MBP minimizes compositional changes. The findings demonstrate that both alloy chemistry and measurement technique significantly influence the determined interfacial properties. Overall, this work provides a comprehensive assessment of how surface-active elements govern wetting and σ in steel-MgO systems and highlights methodological considerations essential for interpreting high-temperature interfacial measurements in steelmaking research.
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GRK2802: Enhanced strength and high reactivity of Al2O3-MgAl2O4-C ceramic filters with in-situ β-SiC whiskers: Role of nano-Al2O3
(Technische Universität Bergakademie Freiberg, 2026-04-27) Song, Jinwen; Yan, Wen; Volkova, Olena; Cheng, Zhenyu; Neubert, Lukas; Angelini, Alberto; Bellé, Matheus Roberto; Li, Yuanbing
The role of nano-Al2O3 content on the phase composition, microstructure, mechanical properties, and purification performance for molten steel of Al2O3-MgAl2O4-C ceramic filters was investigated through XRD, SEM, EDS, as well as immersion test with molten steel. Results indicate that nano-Al2O3 firstly improves slurry retention performance, increases filter strut thickness, and ensures uniform distribution without cracks. Furthermore, during the sintering process, nano-Al2O3 accelerates the mass transfer (Mg2+ and Al3+) between microporous Al2O3-MgAl2O4 particle and nano-Al2O3 due to its high sintering reactivity, which promotes the development and growth of neck connections among the microporous Al2O3-MgAl2O4 particles, resulting in a substantial improvement in the mechanical properties. Regarding molten steel purification, on the one hand, its high reactivity significantly promoted the carbothermal reduction reaction, generating reductive gases that interact with and adsorb [Al], [O], and Al2O3 inclusions in the molten steel, quickly forming a continuous and uniform Al2O3-MgAl2O4 reaction layer at the interface. On the other hand, high mechanical strength also improves filter’s resistance to molten steel erosion and avoids contamination of the molten steel. Together, these two effects synergistically contribute to the purification of molten steel. The filter N5, with 5 wt% nano-Al2O3, not only exhibits excellent mechanical properties with a cold compressive strength of 1.41 MPa and 1.21 MPa after three thermal shock tests, but also demonstrates high purification efficiency, reducing inclusions by 44% and lowering the total oxygen content from 56.3 ppm to 26.1 ppm. Finally, the role of nano-Al2O3 in sintering behavior and purification function, as well as the comprehensive molten steel purification mechanism were proposed.
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GRK2802: Wetting behavior and interfacial reactions of molten steel in contact with the Al2O3-MgAl2O4-C substrate: Effect of porous Al2O3-MgAl2O4 raw material
(Technische Universität Bergakademie Freiberg, 2026-04-27) Song, Jinwen; Wen, Yan; Volkova, Olena; Wang, Qinghu; Bellé, Matheus Roberto; Neubert, Lukas; Andrä, Stefan
This paper investigates the wetting behaviors of molten steel in contact with the Al2O3-MgAl2O4-C (Abbreviated as AM) and Al2O3-C (Abbreviated as A) substrates respectively by the sessile drop wetting method, and thoroughly discusses the interfacial reaction mechanism. In the initial stage of the wetting experiment, the initial contact angle between the molten steel and substrate AM (121°) was significantly smaller than that with substrate A (129°). As the carbothermal reactions proceeded in the substrate, gaseous products accumulated in the micropores of substrate AM, rose into the molten steel and were subsequently expelled. This process caused the molten steel droplet to shake and move on the surface of substrate AM, leading to instability in the contact angle, which fluctuated with time but exhibited an overall increasing trend. In contrast, the contact angle between the molten steel and substrate A remained relatively stable, with no significant gas expulsion observed. During this period, the reducing gases generated by the carbothermal reactions in substrates rose and formed distinct reaction layers at the molten steel/substrate interfaces gradually. A MgAl2O4 layer was observed at the interface between the molten steel and substrate AM. Notably, this reaction layer exhibited a dense and continuous structure in the middle area but became porous and discontinuous in the edge area. By comparison, an Al2O3-Al6Si2O13 layer was detected at the interface between the molten steel and substrate A. Following the formation of reaction layers, the contact angle between the molten steel and substrate AM gradually increased and eventually stabilized at 139°, which was higher than the final stable contact angle (130°) between the molten steel and substrate A. Finally, the comprehensive wetting behavior and the interfacial reaction mechanism were proposed.