Tundish is the last reactor where significant metallurgical operations can still be done. Calcium aluminate slags are able to positively contribute to metallurgy considering oxide separation, protection against reoxidation and preclusion of resulphurisation. However, these are poor insulators. When using low melting point slags it is necessary to use another covering material. The deviation from saturation can be used as a measure of absorption capacity. By utilizing computerized construction of ternary and quaternary diagrams it is possible to compare different slags and to find proper slag compositions with reasonable capacity to dissolve inclusions. Objective of the present technical contribution is to evaluate tundish slag capacity to absorb inclusions, considering a particular tundish industrial slag and the changes in its chemical composition during continuous casting of steel. It was observed that slag composition changed during the continuous casting process; this variation is possibly related to interaction between the CaO-Al2O3 liquid slag and the rice hull ash layer which is used above it. Computational thermodynamics was used to determine activity of alumina dissolved in liquid slag; it was observed that the variation in slag composition did not change slag capacity to absorb inclusions, since precipitation of Al2O3 solid phases is not predicted.
RESUMOA implantação de cemitérios sem projetos geoambientais e hidrogeográficos em solos sem propriedades estruturais e químicas necessárias para receber este tipo de atividade resulta que elementos tóxicos e lixiviados do cemitério percolem ao nível freático. Esta percolação leva a contaminação das águas subterrâneas, afetando drasticamente os recursos naturais e a saúde pública. Desta forma, a toxicidade de solos oriundos de cemitérios de Santa Maria foi avaliada. Paralelamente, as concentrações de Al, Ca, Cd, Cr, Cu, Fe, Mg, Ni, Pb e Zn foram determinadas e comparadas com os limites de tolerância estabelecidos na Resolução 420 de 2013 do Conselho Nacional do Meio Ambiente. Oligochaetas da espécie Eisenia andrei foram empregadas como organismos bioindicadores em bioensaios, no formato ensaio-limite (controle versus tratamento), completamente casualizado, com três repetições, composto por sete tratamentos e dois níveis. Ao final do período de exposição, foram avaliados os efeitos de toxicidade aguda em oligochaetas, sendo feita a concentração letal média (CL 50 ) respectivamente e interferência no processo reprodutivo das oligochaetas. Pela análise química se detectou concentrações de metais tóxicos superiores aos valores de prevenção estabelecidos legalmente.Palavras-chave: bioindicadores, oligochatas, metais tóxicos, toxicidade. Toxicological potential of metals found in soil of cemeteries in SantaMaria -RS ABSTRACTContamination with toxic elements and cemetery leachate may result when proper geoenvironmental and hydro geographic studies are not conducted and cemeteries are dug in soils
Fluorine is widely employed in mold powders used in continuous casting of steels. Although fluorine is important in the melting behavior, slag infiltration and crystallization of the slag film, it provides some disadvantages. Fluorine reacts within the slag, producing substances, such as NaF and SiF, which, in turn, react with the water in the secondary cooling, forming HF. These compounds lead to severe machinery corrosion and risk for the plant's personnel health and environmental impact. Fluorine free mold powder for slab casting is under development as result of the partnership between Imerys Group and ArcelorMittal Tubarão. Regarding to this, alternative raw-materials to substitute F in the mold powders composition have been investigated. Researches have indicated B 2 O 3 as potential substitutes of fluorine from mold slags. The industrial trials, performed in the Brazilian steelworks, ArcelorMittal Tubarão, were accomplished aiming to analyze its behavior during continuous casting operation of low carbon steel grade. Technological parameters like: heat flux in the mold, quality of coils, Fluorine and Boron contents in secondary cooling water, steel Boron pickup , mould flux consumption, behavior of mold sticker detection, SEN wear, environmental impact and personnel health were monitored during continuous casting with the objective of evaluating the performance of mould powder and to provide information about its influence on the surface quality of the steel. The preliminary industrials trials of low carbon steel casting revealed a good surface quality and reduction in the SEN erosion, not impact of plant's personnel health and environmental.
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