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Odsírenie v priebehu výroby ocele

Kijac J.

Prace Instytutu Metalurgii Żelaza

2009

T. 61, nr 5

83-85

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.

The solubility of sulphur in oxide inlusions in Si and Mn deoxidised steel

Kalicka Z., Kawecka-Cebula E., Wypartowicz J.

Archives of Metallurgy and Materials

2004

Vol. 49, iss. 3

585-593

The solubility of MnS in liquid oxide melts: MnO-SiO2, MnO-SiO2-Al2O3 MnO-SiO2-FeO and MnO-SiO2-TiO2 have been calculated from the values of MnO activity and sulphide capacity of these melts. The MnO activity in MnO-SiO 2 melt was based on the experimental data of Rao and Gaskell. The Ban-ya regular solution model was checked on the base of experimental data and it appeared inadequate to the MnO-SiO2 liquid solution. The sulphide capacity of oxide solutions was calculated from the model of Nzotta, Sichen and Seetharaman, with exception of MnO-SiO2-TiO2 melt, for which model parameters are incomplete. It appeared that replacement of SiO 2 with Al2O3 and FeO decreases MnS solubility, while introduction of TiO2 increases this solubility. The highest solubility, up to 80 mass % was obtained in binary MnO-SiO2 solutions.

Obliczono rozpuszczalność MnS w ciekłym roztworze tlenków: MnO-SiO2, MnO-SiO2-Al2O3, Mno-SiO2-FeO i MnO-SiO2-TiO2 na podstawie wartości aktywności MnO w tych roztworach i ich pojemnościsiarczkowej. Aktywności MnO w ciekłym roztworze MnO-SiO2 zostały wyznaczone z danych doswiadczalnych Rao i Gaskella. Na podstawie dostępnych danych doświadczalnych zweryfikowano również stosowalność modelu roztworu regularnego Ban-ya. Model ten okazał się nieodpowiedni dla opisu roztworu MnO-SiO2. Pojemność siarczkowa roztworów tlenkowych została obliczona na podstawie modelu Nzotta, Sichen, Seetharaman, za wyjątkiem roztworu MnO-SiO2-TiO2, dla którego niekompletne są parametry modelu. Stwierdzono, że zastąpienie SiO2 przez Al2O3 i FeO obniża rozpuszczalnośc MnS, podczas gdy wprowadzenie TiO2 podnosi rozpuszczalność MnS. Najwyższe wartości rozpuszczalności, do 80% masowych, występują w przypadku roztworu dwuskładnikowego MnO-SiO2.