Liquid inclusions are important to avoid nozzle clogging during continuous casting of steel. To minimize clogging tendency at a Brazilian steelworks for a low‐sulphur Ca‐treated peritectic steel, deoxidation technique is changed from only Al addition as deoxidant to Fe–Si ferroalloy followed by Al addition, reducing the amount of Al by 20 wt%. Calcium treatment procedure is not changed. According to steelworks data, clogging occurrences are drastically reduced with this process change. In this context, quenched steel samples are collected from the tundish before and after the aforementioned process change. Nonmetallic inclusions characterization is manually performed using scanning electron microscope. For both conditions—before and after the industrial process changes—the inclusions are typically globular ones. However, before the changes, the inclusion modification is not complete because the core of the inclusions is composed by polygonal spinel. After the changes, the inclusions become homogeneous. Computational thermodynamics is applied to calculate the castability windows; they show that the amount of calcium dissolved in liquid steel is too low before the process changes, and this fact explains the blockage of the tundish nozzles, which is observed at steelworks, due to the deposition of high melting point spinel inclusions.

ResumoA escória de convertedor LD desempenha papel fundamental no refino do aço, principalmente na remoção do fósforo. Muito se sabe sobre as características físico-químicas da escória e sua relação com a eficiência do processo de refino, porém poucos utilizam o aspecto microestrutural para tal análise. Neste sentido, este trabalho teve como objetivo analisar a microestrutura da escória formada nos convertedores da Usiminas e compreender aspectos importantes relacionados à reação de desfosforação, para atuar de maneira efetiva na melhoria do processo industrial. Foi verificado que a reação de desfosforação não ocorre junto às fases sólidas da escória. De acordo com estas observações, a quantidade de fundentes adicionada ao convertedor foi revista, alcançando-se uma expressiva redução no teor de CaO livre das escórias. Foi possível observar, também, uma redução de 10% no consumo de cal carregado nos convertedores, sem interferir no teor médio de fósforo do aço ao fim de sopro. Palavras-chave: Escória de convertedor; CaO livre; Microestrutura; Desfosforação. MICROSTRUCTURAL STUDY OF THE LD CONVERTER SLAG AND ITS RELATIONSHIP TO THE DEPHOSPHORISATION PROCESS AbstractThe LD converter slag plays an important role in the refining process, mainly in relationship to phosphorus removal. Much is known about the physicochemical characteristics of the slag and its relationship to the process efficiency; however few employ the microstructural aspect for such analysis. In this sense, the aim of this work was to analyze the slag microstructure formed at Usiminas converters and to understand important points relationed to dephosphorisation reaction, to act efficiently in the industrial process improvement. It was verified that dephosphorisation reaction does not occur in slag solid phases. According to this observation, the amount of fluxes added to the converter was reviewed, reaching a considerable reduction in the free CaO content of the slags. It was also observed a drop of approximately 10% in lime consumption at the converters, without influence in the mean phosphorus content at the end of oxygen blown. Keywords: Converter slag; Free CaO; Microstructure; Dephosphorization. INTRODUÇÃOO refino do aço em convertedor LD é aplicado para remoção de elementos indesejados, tais como carbono, silício e fósforo, presentes no gusa líquido e na sucata carregados no convertedor. A formação de uma escória adequada é essencial para a reação de desfosforação, pois ela deve ser capaz de absorver e reter o fósforo em sua estrutura.As composições química e mineralógica da escória podem ser uma referência importante para avaliar seu comportamento durante o refino do aço, principalmente em relação à desfosforação, quando analisadas em conjunto. Após a solidificação, as principais fases presentes na escória de convertedor são o silicato dicálcio (2CaO.SiO 2 ), a cálcio ferrita (CaO.FeO) e a magnésia--wustita (MgO.FeO), sendo a primeira presente em maior quantidade. O fósforo, na forma de fosfato tricálcio, encontra-se em solução sólida com o s...

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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(1) Background: Titanium dioxide (TiO2) consists of three polymorphs, including anatase, rutile and brookite. This work aimed to elucidate the influence of rutile and anatase forms in the performance of sunscreens formulated with green coffee oil (GCO) from coffee beans discarded in the agri-food industry. (2) Methods: TiO2 particles were characterized in terms of size and wettability. The sunscreens formulated with GCO were characterized regarding the droplet size, rheology, texture profile analysis (TPA), in vitro Sun Protection Factor and Water Resistance Retention. Topical delivery and permeation studies were performed to confirm caffeine release and skin penetration. (3) Results: Particle size distributions of rutile and anatase TiO2 particles were similar, however, smaller droplets as well as decreased viscosity and increased thixotropy were obtained for anatase TiO2 and GCO formulation compared to rutile form formulations. Notwithstanding, all formulations exhibited linear viscoelastic behavior. Regarding the TPA, a wide range of mechanical properties improved mainly by GCO rather than TiO2 form has been demonstrated. The influence of TiO2 form on UV protection was better evidenced in absence of GCO. The sunscreen formulations containing GCO presented a favorable topical delivery as confirmed by caffeine release and permeation. (4) Conclusions: Both TiO2 forms combined with GCO provided suitable properties including an effective ultraviolet (UV)-light protection.

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