Andre Zimmer

Heat Transfer in Steelmaking Ladle

The heat transfer in a steelmaking ladle was studied. The evaluation of heat transfer of the steel was performed by measuring steel temperature in points including all refining steel process. In the ladle, the temperatures in the refractories and the shell were also measured. To evaluate the thermal profile between the hot and cold faces of the ladle in the slag line position, an experiment which shows the importance of thermal contact resistance was carried out. Higher heat losses in the tapping and the vacuum were verified. The temperature measurements of the ladle indicate distinct thermal profiles in each stage of steel refining. Moreover, as each stage of the process depends on the previous one, the complexity of the ladle thermal control is incremental. So a complete model of heat losses in the ladle is complex.

Use of Natural and Modified Natural Nanostructured Materials

The use of natural nanomaterials is environmentally friendly, socially responsible and cost effective. Hence, several industries are investing in cheap ways to explore and process natural resources to make natural nanomaterials available. Natural nanomaterials are abundant; however, certain drawbacks such as incompatibility and extraction are a challenge to make their use more advantageous. Montmorillonite is the most common natural nanomineral used in industry and nanocellulose could be extracted from the most important skeletal component in plants, cellulose. In this chapter a brief overview is given of natural and modified natural nanostructured materials, with emphasis on layered silicates (clays) and cellulose-based materials, followed by some industrial examples.

Avaliação de revestimentos para proteção contra a descarbonetação de tijolos refratários MgO-C durante o aquecimento de panelas de aciaria

This work aims to evaluate the utilization of different coatings to prevent the decarburization of refractory bricks MgO-C used in ladles. This oxidation causes the loss of thickness of the bricks and the reduction of its useful live. The three types of coatings A, B e C were prepared in laboratory and then were applied on MgO-C bricks. The samples were tested at temperatures of 850oC, 950oC and 1050oC. It was verified that the three tested coatings only minimize the decarburization, since they vitrify and become effective at temperatures higher to the beginning of the oxidation temperature. Moreover, it was noticed that the thickness of the decarburized layer is directly proportional to the firing temperature. The coating that presented better results was C, which showed better characteristics of flowing and viscosity. Besides that, it vitrified at lower temperature comparing to coatings A and the B.

Identificação e avaliação dos mecanismos de ataque da escória SiO2-CaO-Al2O3-MgO em tijolos refratários de MgO-C

The present work has as objective to identify and to characterize the responsible mechanisms for the degradation of magnesia-carbon refractory bricks of a metallurgical ladle, due to the attack of the SiO2-CaO-Al2O3-MgO slag. For that, MgO-C refractory bricks used in the slag line were compared with bricks after the use (post mortem). The microstructure of the interfacial region refractory brick/slag was evaluated by mineralogical analyzes (X-rays diffraction), scanning electronic microscopy (SEM) and thin sections for petrography analyses (optic microscopy). It was possible to evidence that the brick post mortem presents, beyond the existing phases already in natura, new phases such as alumina, calcium silicate and gelenite, due to its reaction with the slag. The results suggest that the main way of degradation of the brick was the infiltration of the slag in the matrix and grains boundaries of the refractory brick. This causes to the pulling out of grains, compromising the original microstructure of the refractory material, diminishing its time of useful life.