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1

Odsírenie v priebehu výroby ocele

Kijac J.

Prace Instytutu Metalurgii Żelaza

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2009

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T. 61, nr 5

83-85

EN

The modern metallurgy of iron and steel is first of all oriented in quality improvement, effectiveness and competitiveness of its production. Generally speaking, sulphur is considered a harmful element for steel quality, reason why all the technological steps are being taken in order to eliminate it from the metal bath. Molten systems of inorganic oxides forming a slag phase, form already during their genesis a complex heterogeneous system with many multiple reactions in the forming phase alone, and then subsequently individual components separately and in different combinations enter the interactions with other phases. Metallurgical slag qualities must be defined by the whole complex of physico-chemical characteristics, such as an oxidative ability, optical basicity, sulphide capacity up to slag fl uidity, its surface tension etc. The understanding of regulation of basic physico-chemical qualities of molten metals and slag depending on a chemical structure and a temperature has its importance at the level of the metallurgical process control. Presented paper deals with the possibilities how to exploit the sulphidic capacity for the desulphurisation evaluation in course of the metal reafi ning in the oxygen converter, and the during ladle treatment based on the set of the operational data. The thermodynamic model describes the slag/metal equilibria between O, and S in the molten steel and CaO, Al2O3, SiO2, FeO, MnO and S in the slag. If the oxygen activity, the activity coefficient of sulphur and the sulphide capacity at a given instant and a given position are known, the sulphur partition ratio can be evaluated at that position. The integral part of the work is the process of the pig iron desulphurisation. Magnesium has a high chemical affinity for sulphur and unlike other desulphurising reagents, dissolves in the iron-carbon melt with the result that its reaction with sulphur is homogeneous.

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Application of the Iida model for estimation of slag viscosity for Al2O3-Cr2O3-CaO-CaF2 systems

Kalicka Z., Kawecka-Cebula E., Pytel K.

Archives of Metallurgy and Materials

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2009

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Vol. 54, iss. 1

179-187

EN

The half-empirical model of Iida was applied for estimation of slag viscosities for Al2O3-Cr2O3-CaO-CaF2 systems. The model is based on a hypothetical viscosity of a slag being a sum of viscosities of the components and the slag basicity index which is modified respectively. The model uses two temperature-dependent parameters which are fitted for each group of the slags on the base of experimental viscosity data. The slags considered in this work were composed of ca. 5% Cr2O3, 17-28%CaO, while % Al2O3 was dependent on %CaO, i.e., the %Al2O3/%CaO ratio was within 2.0 to 3.4 by %CaF2 up to 10%. Applicability of the Iida model for these slags was evaluated in two ways: (i) based on the typical slag basicity index, B and (ii) the optical basicity, Λ. Basing on experimental viscosity data for the slags for a 1873-1993K temperature range, the temperature parameters were established. For the case of the slags with no CaF2, a satisfactory aggreement between a semi-empirical formula and the experimental data was found, yet the parameters’ fitting was superior when the slag basicity index B was applied instead of the optical basicity, Λ. For the slags containing CaF2, in which viscosity distinctly goes down with increasing %CaF2, neither B nor Λ – computed from typically applied relationships – gave acceptable estimates of the viscosity. Therefore, the both indices are to be substituted by the modified ones, which – despite of the fact that they have some hidden physical meaning – are to be considered rather as model fitting parameters. The performed computations point out that the model of Iida is a convenient and a relatively simple tool for viscosity estimates, yet only within a particular group of slags.

PL

W pracy zastosowano półempiryczny model lepkości Iida do ciekłych żużli Al2O3-Cr2O3-CaO-CaF2. Model ten opiera się na hipotetycznej lepkości żużla bedącej sumą lepkości składników oraz na wskaźniku zasadowości żużli, który jest odpowiednio zmodyfikowany. Model zawiera dwa parametry bedące funkcją temperatury, które są dopasowywane, dla danej klasy żużli, na podstawie eksperymentalnych wartości lepkości. Rozważane w pracy żużle miały po ok. 5% Cr2O3, 17-28%CaO, % Al2O3 zależny był od %CaO, tzn. stosunek %Al2O3/%CaO był równy od 2,0 do 3,4, %CaF2 był równy od 0 do 10%. Porównano przydatność modelu Iida do tych żużli przeprowadzajżc dwa warianty obliczeń – w oparciu o typowy wskaźnik zasadowosci B oraz zasadowość optyczną Λ. W oparciu o znane eksperymentalne wartości lepkości tych żużli w zakresie 1873-1993K dobrano parametry temperaturowe w równaniu Iida. W przypadku żużli bez CaF2 uzyskano dobra zgodność półempirycznego równania z danymi eksperymentalnymi, jednak dopasowanie parametrów w przypadku wskaźnika zasadowości B okazało się bardziej efektywne niż w przypadku zasadowości optycznej Λ. Dla żużli zawierających CaF2, w których lepkość znacznie spada ze wzrostem %CaF2, ani wskaznik B ani Λ, obliczany wg ogólnie stosowanych zależności, nie daje poprawnego opisu lepkości. Konieczne jest zastąpienie ich przez wartości zmodyfikowane, które, choć mają ukryty sens fizyczny, należy raczej traktować jako parametr modelowy. Obliczenia wykazują, że model Iida jest wygodnym i w miarę prostym modelem do obliczania lepkości, lecz tylko w obrębie danej klasy żużli.

3

Correlation between spectral properties and optical basicity for oxide gels doped with chromium(II) ions.

Kłonkowski A.M., Widernik T., Biczkowski M.

Optica Applicata

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2000

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Vol. 30, nr 4

503-508

EN

For oxide xerogels of the types: Na/sub 2/O-B/sub 2/O/sub 3/-SiO/sub 2/ and SiO/sub 2/-TiO/sub 2/ prepared by the sol-gel procedure a correlation between one of the absorption bands of Cr/sup 3+/ ion (attributed to the /sup 4/A/sub 2g/(F) to /sup 4/T/sub 2g/(F) transition) and theoretical optical basicity has been found. The experimental results show that Cr/sup 3+/ ion can play the role of basicity probe in the Lewis sense for oxide xerogels. Additionally, its band position can be a relative measure of water content in the same material.