Technische Universität Bergakademie Freiberg

Permanent URI for this communityhttp://opara.zih.tu-dresden.de/handle/123456789/16

Research data repository of Freiberg University of Mining and Technology.

Browse

Browsing Technische Universität Bergakademie Freiberg by Subject "4::43"

Filter results by typing the first few letters
Now showing 1 - 10 of 10
  • ItemPublic Metadata
    GRK 2802: CHARACTERIZATION OF COMMERCIAL MgO-C REFRACTORY BRICKS BASED ON MgO-C RECYCLATE WITH VARYING TOTAL CARBON CONTENTS
    (Technische Universität Bergakademie Freiberg, 2025-11-26) Schramm, Alexander; Weidner, Anja; Biermann, Horst; Aneziris, Christos G.; Schemmel, Thomas
    In light of the increasing focus on the recycling of refractories, the properties of commercial MgO-C refractory bricks containing MgO C recyclate are of significant economic and ecological importance. It is essential to consider that incorporating MgO-C recyclate can lead to increased variation in the material composition and, consequently, in the properties of MgO-C grades. In the present study, two commercially available grades of MgO-C bricks containing 47.5 wt.% MgO-C recyclate were characterized. The MgO-C recyclates of both grades were taken from different sources and differed particularly in their carbon content, which resulted in different total carbon contents of both MgO-C brick grades. In addition to determining fundamental properties of both MgO-C brick grades (e. g., total carbon content, bulk density, open porosity, and cold crushing strength), XRD analysis, refractoriness under load (RUL) tests, and four-point bending tests at 1000 °C in an argon atmosphere were conducted. A lower total carbon content resulted in an increased bulk density, higher thermal expansion and increased strength. Compared to a commercial MgO-C grade made from entirely fresh raw materials, the results of the RUL and bending tests revealed no detrimental effects through the incorporation of MgO-C recyclate. Despite different total carbon contents, both MgO-C grades with recyclate exhibited improved refractoriness in the RUL tests compared to the material containing only fresh raw materials.
  • ItemPublic Metadata
    GRK 2802: Characterization of MgO-C recyclate and commercial MgO-C refractory bricks with and without Recyclate
    (Technische Universität Bergakademie Freiberg, 2025-11-13) Schramm, Alexander; Stadtmüller, Till M. J.; Hubálková, Jana; Schimpf, Christian; Wüstefeld, Christina; Schemmel, Thomas; Aneziris, Christos G.; Weidner, Anja; Biermann, Horst
    In light of the increasing focus on the recycling of refractories, the properties of commercial MgO-C refractory bricks containing MgO-C recyclate are of significant economic and ecological importance. In the present study, MgO-C recyclate and two commercially available MgO-C bricks – one grade consisting exclusively of fresh raw materials while the other containing 47.5 wt.% MgO-C recyclate – were comprehensively characterized. This involved the use of X-ray computed tomography, scanning electron microscopy, X ray fluorescence analysis, X-ray diffraction, as well as density and porosity measurements. The MgO C recyclate exhibited a heterogeneous composition consisting of MgO aggregates and contained an increased content of impurities compared to fresh MgO raw materials. The incorporation of MgO C recyclate as a raw material for commercial MgO-C bricks resulted in a decrease of the average MgO aggregate size, a higher porosity with a decrease in the median pore size and a reduced CaO/SiO2 ratio of the corresponding MgO-C brick grade. Furthermore, the MgO-C grade with 47.5 wt.% MgO-C recyclate exhibited a higher cold crushing strength, but a reduced oxidation resistance.
  • ItemPublic Metadata
    GRK 2802: Densities, Surface Tensions, and Viscosities of Molten High-Silicon Electrical Steels with Different Silicon Contents
    (Technische Universität Bergakademie Freiberg, 2025-10-24) Neubert, Lukas; Bellé, Matheus Roberto; Yamamoto, Taisei; Nishi, Tsuyoshi; Yamano, Hidemasa; Ahrenhold, Frank; Volkova, Olena
    Density, surface tension, and viscosity of various liquid electrical steels are measured at different temperatures, varying in their silicon content between 3 and 6mass%. Density and surface tension are determined using the maximum bubble pressure method, while viscosity is investigated comparatively using a vibrating finger viscometer and an oscillating crucible viscometer. The results are compared with models known from the literature. Based on this, the density of the steel [ρ] = kgm 3 and the surface tension [σ] =Nm 1 can be described as a function of temperature [θ] = °C and silicon content [Si] =mass% using the equations: ρðθ, SiÞ ¼ 1.28 θ 104.18 Si þ 9081.8, σðθ, SiÞ ¼ 10 4 ½ 0.00903 θ2 1.21494 Si2 þ 29.268 θ 1.987 Si 22334 . There is a lack of experimental data in the literature for high-temperature thermophysical properties for electrical steels. This underlines once again the novelty and significance of this study, as the determined thermophysical properties are essential for a wide range of applications. For instance, they are crucial in the production of metallic powders for additive manufacturing by atomization to adjust the properties of the powders precisely. The findings are also important for steelmaking itself, as the corrosion behavior of refractory material can be better determined.
  • ItemPublic Metadata
    GRK 2802: Effect of Oxygen on Thermophysical Properties of Molten High-Silicon Electrical Steels and Its Impact on Bubble Formation Behavior
    (Technische Universität Bergakademie Freiberg, 2025-10-24) Neubert, Lukas; Bellé, Matheus Roberto; Seetharaman, Sridhar; Volkova, Olena
    The presence of oxygen in liquid steels has a considerable influence on their properties. Higher oxygen concentrations are typical for unkilled melts, after tapping from the basic oxygen furnace (BOF) or during secondary metallurgy. This influences thermophysical properties, for instance, surface tension, due to the surface activity of dissolved oxygen. Processes in secondary metallurgy or the interaction of the melt with the refractory material will be different. In this study, density and surface tension of molten high-silicon electrical steels are analyzed dependent of different oxygen contents, which are comparable to industrial melts during secondary metallurgy. The maximum bubble pressure method was used, and total oxygen contents between 77 and 300 ppm were taken into consideration. The silicon content of the steels is varied between 3 and 6 mass-pct. The effect of oxygen on the bubble formation behavior during decarburization in a liquid steel melt is also discussed. The results make it possible to calculate the size of bubbles that form in a melt. These findings are transferred to the processing of electrical steels, to vacuum treatments like the RH or VOD process. Reactions such as decarburization and the dissolution behavior of alloying agents are described more precisely based on these insights.
  • ItemPublic Metadata
    GRK 2802: Extraction of Vanadium from CaO–SiO2–MgO–Al2O3 Slags Based on Vaporization of Vanadium Pentoxide
    (Technische Universität Bergakademie Freiberg, 2025-10-24) Neubert, Lukas; Shyrokykh, Tetiana; Tinkova, Nataliia; Seetharaman, Sridhar; Volkova, Olena
    Vanadium is an important micro-alloying element for various steel grades. Consequently, it is also present in the slags used in the production of those grades. During steelmaking, the vanadium vaporization from the slag is not desirable, as it increases vanadium consumption and at the same time releases toxic vapors of its higher oxides. However, the recovery of vanadium from the slag after the processing is worthwhile. In oxidic form as vanadium pentoxide (V2O5), vanadium can be extracted from the slag. In this research, the vaporization behavior of vanadium from CaO–SiO2–MgO–Al2O3 industrial slag is investigated at 1873 K. The effect of different process parameters, e.g., the pressure in the furnace chamber, the duration of the oxygen treatment of the slag, and the oxygen flow rate, is considered. The effect of P2O5 and Fe2O3 addition on the extraction of vanadium is studied. It is possible to induce formation of V2O5 gas bubbles in the slag due to the oxidation of vanadium. Thus, vanadium respectively V2O5 is extracted from the slag.
  • ItemPublic Metadata
    GRK 2802: Fracture mechanics behavior of coarse-grained MgO-C at room and high temperature
    (Technische Universität Bergakademie Freiberg, 2025-11-13) Solarek, Johannes; Schramm, Alexander; Henkel, Sebastian; Weidner, Anja; Aneziris, Christos G.; Biermann, Horst
    The fracture mechanical properties of coarse-grained MgO-C were investigated in four-point bending tests at single-edge V-notched beams (SEVNB) at room and high temperature. For measurement of the crack mouth opening displacement (CMOD) an optical system was used. Room temperature tests were accompanied with microstructural observations of the crack path with the use of digital image correlation to investigate the mechanisms of crack propagation and to determine the crack length. MgO-C showed stable crack propagation at room temperature as well as up to 1500°C. Increased fracture toughness KIc and work of fracture were observed in the temperature range from 700°C to 1200°C. This behavior was correlated with crack closure, quasi-plastic deformation as well as the activation of visco-plastic creep mechanisms above 1200°C. Additionally, the results were discussed in terms of Hasselman’s thermal shock parameters.
  • ItemPublic Metadata
    GRK 2802: HIGH-TEMPERATURE COMPRESSION TESTS AND ACCOMPANYING SEM INVESTIGATIONS OF MgO-C REFRACTORIES BASED ON FRESH MgO AND RECYCLATE
    (Technische Universität Bergakademie Freiberg, 2025-08-27) Schramm, Alexander; Weidner, Anja; Biermann, Horst; Stadtmüller, Till M. J.; Aneziris, Christos G.; Schemmel, Thomas
    With regard to the increasingly desired recycling of refractories, the properties of MgO-C containing recyclate are of high economic and ecological relevance. Two commercially available grades were studied to evaluate the influence of recyclate in MgO-C materials: MgO-C consisting only of fresh MgO as well as MgO-C with 50 wt.% recyclate. In this study, compression tests on these MgO-C materials were performed at room temperature, 1000°C and 1300°C. In order to investigate the microstructure and to identify the occurring damage mechanisms, scanning electron microscopy (SEM) investigations were carried out. The compression tests provided higher strengths at room temperature and at 1000°C for the MgO-C grade with recyclate compared to the grade with only fresh MgO and comparable strengths at 1300°C. Thus, the use of recycled agglomerates had no negative effect on the compressive strength.
  • ItemPublic Metadata
    GRK 2802: Hochtemperatur-Biegefestigkeit von kohlenstoffgebundenem Magnesiumoxid (MgO-C) unter Einbindung von DIC
    (Technische Universität Bergakademie Freiberg, 2025-09-16) Schramm, Alexander; Knöchel, Lukas; Biermann, Horst; Weidner, Anja
    Kohlenstoffgebundenes Magnesiumoxid (MgO-C) als Vertreter der Feuerfestwerkstoffe ist als Zustellungsmaterial in Konvertern, Stahlgießpfannen und Elektrolichtbogenöfen unverzichtbar. Der Werkstoff ist in der Anwendung komplexen thermischen, mechanischen und korrosiven Beanspruchungen ausgesetzt. Die Bewertung der quasi-statischen Hochtemperaturfestigkeit ist daher von zentralem Interesse und Gegenstand der vorliegenden Studie. Vier-Punkt-Biegeversuche an kommerziellem MgO-C Feuerfestmaterial wurden in einer Hochtemperaturprüfmaschine unter Schutzgas bis 1300°C durchgeführt. Mittels digitaler Bildkorrelation (DIC) bei Raumtemperatur wurden Aussagen zu ablaufenden Schädigungsmechanismen gemacht. Die in dieser Studie durchgeführten Versuche lieferten bei erhöhten Temperaturen höhere Biegefestigkeiten als bei Raumtemperatur, was auf das Schließen von Rissen entlang der Grenzfläche zwischen MgO und kohlenstoffhaltiger Matrix zurückgeführt wird.
  • ItemPublic Metadata
    GRK 2802: Phosphorus Partition Between Liquid Crude Steel and High-Basicity Basic Oxygen Furnace Slags Containing V2O5
    (Technische Universität Bergakademie Freiberg, 2025-10-24) Neubert, Lukas; Kovtun, Oleksandr; Kreschel, Thilo; Volkova, Olena
    The influence of V2O5 on the phosphorus partition between liquid crude steel and heterogenous basic oxygen furnace (BOF) slag with CaO/SiO2 = 4.2 was investigated at a temperature of 1600 C in a middle frequency induction furnace. Thereby the phosphorus transfer from ‘‘steel to slag’’ as well as from ‘‘slag to steel’’ was studied over a holding time of 60 minutes. The measured results were shown as phosphorus partition and phosphorus capacity and compared with the experimental values from the literature. It was found that V2O5 in highly basic BOF slags decreases phosphorus partition and phosphorus capacity. In addition, the resulting slags were investigated using a scanning electron microscope (SEM).
  • ItemPublic Metadata
    GRK 2802: Vaporization of Vanadium Pentoxide from Iron and Steel-Making Slags
    (Technische Universität Bergakademie Freiberg, 2025-10-24) Neubert, Lukas; Volkova, Olena
    Vanadium is present in increased amounts in slag because of the production of certain steel grades and manufacturing technologies. In terms of circular economy, vanadium should be recovered from the slag, to use it again as an alloying element. Only a few studies on the extraction of vanadium have been carried out with synthetic slags. The core of this study is the characterisation of the extraction behaviour of vanadium by evaporation of its oxides from real iron and steel-making slags. The effect of various influencing factors on the evaporation behaviour of the slags should be demonstrated. The evaluation of the results should also take crucible wear into account. In addition, the phases formed in the slag are to be analysed. For this purpose, several melting tests are carried out with different blast furnace slags. To determine the vaporised components, the slags are analysed by an X-ray fluorescence spectrometer.