Efeito do tipo de grafite no comportamento de prensagem de tijolos MgO-C

Abstract

Refractory ceramics are materials that withstand high temperatures without compromising their performance and structural characteristics. Due to their excellence when applied in severe conditions, refractories are extremely important products for the steel industry. With the increasing prices of raw materials, especially graphite from China, there is a need to evaluate the influence of this component on the processing and properties of refractories, aiming to optimize product performance and identify possible improvements. This study examined the effect of varying the type of graphite and the influence of particle size variation in MgO-C formulations on the pressing behavior and properties of these materials. For this purpose, the characterization of available raw materials was carried out through particle size distribution analyses and scanning electron microscopy (SEM) tests. The EMMA software (Elkem Materials Mixture Analyser) was used to assess three formulations in relation to the theoretical particle packing model. MgO-C bricks were pressed using pressures of 14, 16, 18, and 20 kN/cm2, and the produced samples were characterized for their density, porosity, and ultrasonic tests. It was observed that better compaction was achieved for Formulation 1 (which contained a mixture of two types of graphite), as this refractory exhibited pieces with higher geometric densities at all applied pressures. This behavior may be related to the improved packing of this composition, which closely approached the theoretical curve. On the other hand, the use of graphite 1 (with particles up to 1 mm) and the alteration of the particle size distribution of the MgO aggregates in Formulation 3 resulted in refractories with reduced apparent porosity (2-5%) after the curing stage. Therefore, the optimization of the processing and properties of the MgO-C bricks evaluated here could be achieved by employing a single carbon source and by adjusting the particle size distribution of the other materials contained in the formulation.