RESUMO A composição química das cerâmicas tem grande importância no entendimento das propriedades químicas e físicas desse material. Neste trabalho foram realizadas caracterizações química e mineralógica de misturas de argilas, incorporando um resíduo proveniente de uma indústria siderúrgica, para aplicar na produção de cerâmica. Dois tipos de argila foram misturados na proporção de 1:1 e o resíduo foi adicionado nas proporções de 5%, 10%, 15% e 20%. Avaliou-se a composição química de cada material puro e a composição mineralógica foi analisada após a etapa de queima, na qual 5 corpos de prova foram submetidos a uma temperatura de 800 °C. A caracterização foi realizada com os ensaios de Fluorescência de Raios X (FRX), Difração de Raios X (DRX), Termogravimetria (TG) e Calorimetria Exploratória Diferencial (DSC). A FRX mostrou os óxidos de silício (SiO2) e alumínio (Al2O3) como principais componentes das argilas e os óxidos de ferro (T-Fe, teor de ferro) como principais componentes do resíduo. A DRX mostrou o quartzo como o mineral mais abundante nas argilas, mas que à medida que a concentração de resíduo aumentava na amostra, aumentava também o teor de hematita, principal mineral encontrado no resíduo. A TG e a DSC confirmaram picos esperados nas argilas e identificou uma reação exotérmica nas amostras com resíduo. O aumento do percentual de resíduo provocou alterações na composição química das amostras, no entanto, não foram alterações significativas, o que indica a possibilidade do uso desse resíduo na produção de cerâmica vermelha.

Sliver defects were detected in galvanized and uncoated cold-rolled strips, and their causes were investigated. Most of these strips were produced from transition ladle slabs, which were obtained in a sequence of twenty heats of an ultra-low carbon Al-killed steel. A significant reduction in the steel level in tundish occurred during these slabs' casting. The strip defects, and as a comparative, a mould flux inclusion found in a first slab of the sequence, were analysed with a scanning electron microscope (SEM). Also, each of the twenty heats was sampled in tundish, quenched in water, and manually analysed with SEM to characterize its dominant inclusions. Regarding the sliver defects, mainly silica together with alumina or Al-Ti-O systems particles were found in them. The primary sources for these particles are likely tundish flux and reoxidation products. Finally, a mechanism was proposed for the formation of these inclusions.

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The present work is based on the characterization of nonmetallic inclusions in Ti stabilized ultra-low carbon steel, produced in a large steel mill. Due to a large incidence of submersed valve clogging in a continuous casting, the study is important in order to know the characteristics of the inclusions which are causing the problem. Total of 24 heats were sampled in the tundish and manually analyzed with a scanning electron microscope. The results revealed that 98.65% of the 3183 inclusions analyzed were solid in steelmaking temperature and 66.54% were alumina. The solid inclusions of alumina have low wettability for the iron bath, showing a high tendency of agglomeration in the submersed valves, affecting the castability. It has been concluded from the results and literature that some alternative measures such as the application of the treatment with calcium, precautions to avoid steel re-oxidation and the total or partial replacement of the pre-deoxidized element; would reduce the obstruction problem.

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