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VERSION:2.0
METHOD:PUBLISH
BEGIN:VEVENT
ORGANIZER;CN=ESTAD 2023:mailto:info@metec-estad.com
LOCATION:Room 18b
SUMMARY:Non-contamination related chromium pick-up in RH degasser: Chromium based refractory ternary phase diagrams, thermodynamic and kinect analysis
DESCRIPTION:As market demands and competitiveness increases worldwide, steelplants are constantly adapting and innovating to meet higher quality specifications, reach new market shares and achieve cost reductions. As such changes occur, we see renewal in the Steel Industry and gain room to find unprecedented and/or uncharted issues. It was observed at Ternium Brasil Steelplant the occurrence of Chromium Pick-up unrelated to charged materials (i.e. contamination) in the Ruhrstahl Heraeus Vacuum Degasser (RH) during the treatment of electric steels. The Chromium pick-up occurrences were sufficiently high to surpass the client’s specified residual level. As chromium oxides are present in the RH refractories, the present work aims to evaluate the thermodynamic stability and kinetic mass transfer aspects of MgO, Cr2O3, Al2O3, SiO2 systems in contact with Steel. The results indicated that chromium oxide is not stable in the presence of well deoxidized steels, including non-electric grades. Still, a strong influence of silicon on the chromium pick-up was observed. The thermodynamic analysis indicated that the silicon addition to MgO, Cr2O3, Al2O3 systems creates liquid-phases for the typical temperature ranges of steel treatment. This may impact on the kinetics of refractory wear and dissolution. Furthermore, the analysis indicated the high-silicon content of the electric steels lowers the oxygen potential in steel. Besides, silicon reduces the surface energy between steel and refractories, increasing the latter’s wettability. To control the occurrence of chromium pick-up, mass transfer models were formulated for solute transport in steel and for refractory erosion as rate-limiting steps. The models were then used to optimize both the acceptable charge composition and the RH processing time when refining electric steels with controlled chromium residuals. The introduction of these control measures dramatically reduced the deviations associated with high content of residual chromium in electric steels.


CLASS:PUBLIC
DTSTART:20230614T143000
DTEND:20230614T145000
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