Effect of the adhered ladle slag on the decarburization of MgO-C bricks

Reference Presenter Authors
14-059 Analía Gladys Tomba Martinez Moliné, M.N.(Instituto de investigación en Ciencia y Tecnología de Materiales); Galliano, P.(Center for Industrial Research); Tomba Martinez, A.G.(Instituto de investigación en Ciencia y Tecnología de Materiales); MgO-C bricks are widely used as working lining in steelmaking ladles due to their excellent in-service properties. However, they are susceptible to oxidation in contact with oxygen at high temperature when the empty ladle is thermally treated with vertical burners between heat and heat. Secondary steelmaking slag covers the steel and interacts with it, playing a critical role in ladle metallurgical process to promote both steel cleanliness and ladle thermal insulation. Particularly, ladle furnace slag (LFS) is mainly constituted by CaO, MgO, SiO2 and Al2O3. After ladle cooling, solid slag is removed for its final destination. The presence of certain components such as CaO, MgO and calcium aluminates, hydrate and carbonate by the environment (weathering), affecting the integrity of the slag. In a steelmaking ladle cycle, liquid steel is emptied from the bottom, leaving a thin slag layer on the refractory walls. Thus, the possibility of taking advantage of the adhered slag as a barrier to oxygen is considered, taking into account the degradation suffered by this layer. The objective of this work is to study the effect of slag adhered to MgO-C bricks on its oxidation in air at 1000°C (ladle preheating temperature). Additionally, as a continuation of previous work on the slag degradation, the effect of the weathering process on its protective capacity is evaluated. For the tests, slag layer is generated by treatment at 1400°C in graphite bed of MgO-C samples. These samples are placed in alumina crucibles, leaving only the face covered with slag exposed to air (unidirectional test). Variation in weight, depth of decarburization and reduction of graphite content by XRD are determined as oxidation indicators. To evaluate the effect of slag weathering, tests are carried out after 2 and 10 weeks from samples preparation. Obtained results are analyzed considering the characteristics of evaluated materials, the slag adherence, and its degradation process.
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