ESTUDO TERMODINÂMICO DE INCLUSÕES NÃO-METÁLICAS EM AÇO ACALMADO AO ALUMÍNIO E TRATADO COM CÁLCIO

Abstract

The main goal was the study of non-metallic inclusion formation in the continuous casting (CC) for Al-killed, calcium treated steel (SAE 8620). The specific goals were: 1) To obtain the phases and compounds formed in the inclusions as a function of composition and casting temperature adopted for the SAE 8620 steel. 2) To establish conditions of steel chemical composition for the formation of less harmful inclusions to the SAE 8620 castability. Based in the literature and previous work of the authors, were carried out simulations using the software FactSage and databases. The simulations were realized using the global chemical composition of SAE 8620 steel in the CC tundish. The results were steel and non-metallic inclusions (oxides and sulphites) composition in the aimed temperature. The results showed the formation of different solid oxides and the formation of liquid phase in the inclusions by the variation of calcium content in the steel. It was possible to determine the inclusion composition as a function of aluminum and calcium content of SAE 8620 steel. For the specific composition and temperature of SAE 8620 steel, it was possible to establish a range of calcium content were the inclusions are formed by predominant liquid phase. It was possible to calculate the percent of liquid and solid phase in the inclusions, as well the composition in terms of oxides.