ResumoOs pós fluxantes consistem de uma mistura de minerais que em contato com o aço líquido, devem fundir e gerar uma escória líquida com características específicas para cada condição de lingotamento. Possuem, como base, o sistema CaO-SiO2-Al2O3-Na2O-CaF2 e podem conter MgO, Li2O, K2O e B2O3. Este trabalho propõe caracterizar os pós fluxantes comerciais baixo carbono e peritético através da microscopia ótica de luz transmitida usando os mesmos procedimentos de descrição de lâminas delgadas para rochas e minerais. Os resultados mostraram a formação de grãos e fase cristalina bem definidas para o peritético e a fase amorfa para o baixo carbono. Em trabalhos futuros esta técnica melhor desenvolvida poderá servir para quantificar o nível de cristalinidade dos fluxantes com maior precisão. Palavras-chave:Pós Fluxante; Lâmina Delgada; Lingotamento; Microscopia óptica. TRANSMITTED LIGHT MICROSCOPY USE IN FLUXING CHARACTERISATION AbstractThe casting powder consists of a mixture of minerals in contact with the liquid steel must merge and produce a liquid slag with specific characteristics for each casting condition. Feature based on the CaO-SiO 2 -Al 2 O 3 -Na 2 O-CaF 2 system and may contain MgO, Li 2 O, K 2 O, B 2 O 3 . This work aims to characterize the post commercial low carbon fluxes and peritectic through the optical transmitted light microscopy using the same Description of thin sections of procedures for rocks and minerals. The results showed the formation of grains and well-defined crystalline phase to the amorphous phase and peritectic to low carbon. In future work best developed this technique may serve to quantify the level of crystallinity of the fluxes accurately.

Ornamental rock production, such as marble and granite plates, have great importance in the southeastern region of Brazil. Its residues are composed of some compounds used in continuous casting as mould fluxes. Therefore, the aim of this article was to study these residues to formulate mould fluxes. First, the raw materials were chemically characterized by energy dispersive X-ray spectroscopy (EDS) and two new fluxes were developed based on two different commercial fluxes used for peritectic and low carbon steels. All fluxes were analyzed for their ability to form crystalline phases, by performing the modified Stollberg test. The slag formed was analyzed by X-ray diffraction (XRD), thin section microscopy (TSM) technique, and a mathematical model for comparison. Also, sample fluidity was measured using the known "boat test" and viscosities were predicted by FactSage

Hybrid composites with synthetic and natural fibers are a good choice in the field of composites, as they combine the good mechanical performance of synthetic fibers with the advantages of natural fibers. In this work, polymeric hybrid composites associating glass fiber and natural fibers were developed. Three hybrid composites were developed: sisal/glass, coir/glass and Luffa/glass. The composites are five-layer laminate, three layers of E-glass interspersed with two layers of natural fibers that can be sisal, coir, or Luffa sponge (Luffa Cylindrica). In addition to hybrid composites, a five-layer fiberglass composite was also manufactured. The composites were manufactured by compression molding technique using orthophthalic polyester resin as matrix. Tensile and flexural tests were performed to characterize the composites. Considering the three hybrid composites, the best behavior was observed for the sisal/glass composite, being a potential replacement for fiberglass. The order of performance was the same in the tensile and flexural tests, sisal/glass, coir/glass, and luffa/glass, in this order. In the specimen’s fracture analysis, for both tests, it was observed that the fracture was quite located with no damage in regions far from the fracture. This behavior indicates good adhesion between the layers of natural and synthetic fibers, despite the discrepancy of their properties.

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ResumoUma das linhas de pesquisa de destaque na vasta área dos compósitos poliméricos é a da utilização de fibras naturais como agentes de reforçamento. Apesar das inúmeras vantagens essas fibras apresentam limitações, como alta absorção de umidade e baixo desempenho mecânico, que restringem sua utilização em aplicações estruturais. Buscando minimizar estes problemas foram desenvolvidos neste trabalho três compósitos híbridos associando uma fibra natural (sisal, coco e bucha vegetal), com a fibra de vidro. O objetivo foi avaliar o processo de absorção d'água e seu efeito nas propriedades mecânicas em tração dos compósitos. A técnica de fabricação foi a moldagem manual seguida de compressão. Os compósitos são laminados de cinco camadas; três camadas de fibras de vidro intercaladas com duas camadas de fibras naturais. A matriz é a resina poliéster ortoftálica. A caracterização destes compósitos foi feita por ensaios de absorção d'água e ensaios de tração em duas condições: seco e após saturação por água. O híbrido sisal/vidro foi o que apresentou o melhor desempenho mecânico, seguido dos híbridos coco/vidro e bucha/vidro. A absorção d'água causou redução das propriedades mecânicas. O híbrido bucha/vidro foi o que apresentou o menor percentual de redução após a saturação, apesar de absorver o maior percentual d'água. Palavras-chave: Compósitos híbridos; Fibras naturais; Absorção de umidade. EFFECT OF WATER ABSORPTION IN DEGRADATION OF HYBRID COMPOSITES WITH NATURAL FIBRES AbstractOne of the most important research lines in the vast area of polymeric composites is the use of natural fibers as reinforcement agents. Despite the many advantages these fibers have limitations, such as, high moisture absorption and low mechanical performance, restricting its use in structural applications. In order to minimize these problems have been developed in this work three hybrid composites combining a natural fiber (sisal, coir and loofah), with glass fiber. The aim is to evaluate the water absorption process and its effect on the tensile mechanical properties of the composites. The composites were made by hand lay-up followed by compression molding. They are laminates with five layers; three layers of glass fibers interspersed with two layers of natural fibers. The matrix was the orthophthalic polymeric resin. The characterization of these composites was made by water absorption test and tensile test on two conditions: dry and after water saturation. The hybrid sisal/glass presented the best mechanical performance, followed by coir/glass and loofah/glass composites. Water absorption causes reduction of mechanical properties. The hybrid loofah/glass presented the lowest percentage of reduction after saturation, despite having the highest level of water absorption.