ResumoA campanha dos refratários à base de carbono aplicados como revestimento de trabalho de diversos equipamentos siderúrgicos depende da soma de diversos fatores como resistência à corrosão, resistência à oxidação do carbono, estabilidade termomecânica, entre outros. Durante a etapa de aquecimento inicial de revestimentos refratários novos ocorre a oxidação prematura do carbono presente no revestimento refratário, reduzindo a vida útil do revestimento precocemente. Para reduzir a oxidação precoce do carbono foi desenvolvido um novo coating cerâmico que atua como uma eficiente barreira física, reduzindo o contato do oxigênio da atmosfera de aquecimento com o carbono presente no refratário. O coating desenvolvido possui uma fase ligante com pega química ativada termicamente e possui como carga refratária um composto sílico-aluminoso com elevada estabilidade térmica. Os resultados laboratoriais de avaliação de desempenho revelaram que com a aplicação do novo coating desenvolvido reduz-se a oxidação prematura do carbono em até 77% e elevase a vida útil do revestimento em alguns casos em até 15%. O coating desenvolvido revelou possuir excelente desempenho quanto a proteção do refratário MgO-C contra a oxidação do carbono que ocorre durante a etapa de aquecimento de equipamentos com refratários novos, comprovando sua aplicabilidade em diversos equipamentos siderúrgicos que possuem revestimentos refratários à base de carbono. Palavras-chave:Coating cerâmico; Oxidação; Refratários à base de carbono. HIGH PERFORMANCE CERAMIC COATING TO REDUCE OXIDATION OF CARBON BASED REFRACTORIES AbstractThe campaign of the carbon-based refractories applied as working line of steel making equipment's depends on many factors, such as corrosion resistance, oxidation resistance carbon, thermo-mechanical stability, among others. During the initial heating stage of new refractory lining, the premature oxidation of the carbon present in the coating occurs, reducing the refractory's lifespan. Aiming to reduce this oxidation's effects, a new ceramic coating was developed, that acts as an efficient physical barrier, reducing the contact of atmosphere's oxygen with the carbon in the refractory. This new coating has a binder phase with a thermally activated chemical handle and has as refractory load a silico-aluminous compound with high thermal stability. Laboratory results of performance evaluation revealed that with the application of this new coating, the premature oxidation of carbon reduces up to 77% and the lifespan rises up to 15%. This coating was found to have an excellent performance regarding the protection of the MgO-C refractories' against the carbon oxidation that occurs during the heating stage of equipment's with new refractories, proving its applicability in various steel equipment that have carbon based refractory linings.
High quality materials are increasingly desired by consumers, and advances in technologies of steelmaking processes are closely linked to manufacturing suitable high performance refractories which do not interfere in the final properties of materials produced. Magnesia-carbon refractories are widely used in several steelmaking plants, both for transportation and refining processes which makes the knowledge of the quality of raw materials is essential for manufacturing high quality refractories. In this work, the approach is the study of how the corrosion behavior of magnesia aggregates (sinterized and electrofused) by LD steelmaking slag occurs using a modified crucible testing. The magnesia aggregates were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS). The XRF analysis shows that the main impurities of magnesia grains is CaO and SiO2 and the SEM analysis showed their impurities are concentrate on grain boundary in electrofused magnesia, while it is found throughout the sinterized magnesia aggregates. The major phase found both magnesia aggregates is periclase. The largest grain sizes were found in ME3 samples, while the smaller sizes in ME1. The slag used comes from converter (BOF) and has high concentration of FeO. The corrosion tests showed that the attack on magnesia aggregates occurred, mainly by the infiltrating of iron compounds in the grain boundary, dragging the grains to the bath and dissolving them into slag. Among the electrofused, the performance could be estimated in ME3>ME2>ME1. The performance for sinterized would be as follows MS3>MS1>MS2.
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