Authors' computer program was employed in the simulation of the course of steel refining by means of simultaneously used aluminium and titanium. The mass and chemical composition of liquid steel and non-metallic precipitates, were calculated at constant or variable temperature. The influence of assumed nitrides form on the results of simulation was determined. Nitrides may be considered either as separate phases or as the components of non-metallic solution. The stoichiometry of titanium oxide obtained also influences the results of simulation. Parallel analysis of steel refining was carried out with the use of FactSage program. As a result of calculations the subsequent states of equilibrium between steel and non-metallic phase were determined. It was found that aluminium and titanium nitrides may exist only as the components of oxide-nitride solution, not as separate phases.Keywords: steel refining, computer simulation, aluminium, titanium, nitrides, oxides Przy pomocy własnego programu komputerowego dokonano symulacji przebiegu rafinacji stali przy pomocy glinu i tytanu, wyznaczając masę i skład chemiczny ciekłej stali i wydzieleń niemetalicznych dla ustalonej lub zmiennej temperatury. Rozpatrzono konsekwencje występowania dwóch możliwych form istnienia azotków glinu i tytanu: jako odrębnych faz i jako składników ciekłego roztworu. Również stechiometria tlenku tytanu uzyskanego w wyniku odtleniania wpływa na wynik obliczeń. Równoległą analizę tego samego przypadku przeprowadzono przy pomocy programu FactSage, wyznaczając kolejne stany równowagi między ciekłą stalą a fazą niemetaliczną. Stwierdzono, że azotki glinu i tytanu mogą występować tylko jako składniki roztworu tlenkowo-azotkowego., nie zaś jako odrębna faza.

The work analyses the possibilities of modeling the process of steel deoxidization from the view-point of thermodynamic equilibrium between liquid steel and oxide precipitates. Two calculation procedures were employed, which make use of WYK STAL authors' program and commercial software FactSage. Two kinds of steel were taken into account, one with considerable titanium addition and the second without titanium. The variation of chemical composition of non-metallic precipitates with titanium concentration, aluminum addition and temperature was determined. The apparent influence of assumed thermodynamic model on the composition of non-metallic precipitate was stated.Keywords: simulation, deoxidization, steel, titanium, aluminum, nitrides Praca analizuje możliwości modelowania procesu odtleniania stali w aspekcie równowagi termodynamicznej między ciekłą stalą a wydzieleniami tlenkowymi. Zastosowano dwie procedury obliczeniowe z wykorzystaniem komercyjnego pakietu FACTSage oraz własnego programu WYK STAL. Obliczenia wykonano dla dwóch gatunków stali, z których jedna posiada znaczny dodatek tytanu. Obliczono, jak zmienia się skład wydzieleń tlenkowych pod wpływem stężenia tytanu, dodatku glinu oraz temperatury. Stwierdzono wyraźny wpływ przyjętego modelu termodynamicznego procesu na uzyskany skład fazy niemetalicznej.

The current work deals with the phenomenon of non-metallic inclusions as a result of the addition of yttrium to the liquid steel as an alloying component. The order of introducing individual components determines their final content in steel, and this problem was analyzed using the WYK_Stal program developed at AGH. The study of Y 2 O 3 and Y 2 S 3 phase precipitation and the relationship between the addition of Y, Al, Ca, O, and S in molten steel was studied using the thermodynamic models based on Wagner's formalism. The introductions of yttrium prior to aluminum brought about huge losses, and it mainly occurred due to the formation of oxides. The low oxygen content in the metal bath promotes the formation of yttrium sulphide. When yttrium is introduced after aluminum and calcium, yttrium is used for the precipitation of its sulfide, and in this way the manganese sulfide formation is reduced.

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The research focused on the influence of cerium on the chemical composition and morphology of non-metallic inclusions in pre-oxidised steel to which Al, Ca, and Ce was added in different amount and order. Calculations were carried out using our own computer program. The simulation results obtained according to two calculation models helped identify precipitates from the Ce–O–S system. The possibility of CeN formation was also identified. The trace amounts of these inclusions were also found in the results. Consideration of the physicochemical phenomena at the boundary, as well as the interfacial partitioning and the sulfur partition coefficient, influences the favourable chemical composition of the inclusions, limiting it mainly to compounds from the Al2O3, Ce2O3, and CaS systems. It was found that the addition of Ce before Ca causes the elimination of MnS precipitates and Ca-containing inclusions in the steel.