Thermal and mechanical properties of commercial MgO-C bricks

Abstract

MgO-C (magnesia-carbon) refractories are widely used in several steelmaking linings. These refractories are exposed to extreme stress due to high temperatures (T > 1600 °C) required to cause the metallurgical reactions. These working conditions produced refractory wear through various related processes. The different types of degradation that the material suffers can be from thermochemical or thermomechanical origin. In this work, the Young's modulus, the fracture resistance and the thermal expansion coefficient of three commercial magnesia-carbon bricks (A, B, and C) were measured to evaluate their resistance to thermomechanical degradation. These data provided an estimation of the thermomechanical stresses that they can withstand. According to the results, the lowest fracture toughness is developed by brick C. This behavior is associated to a higher porosity and quality of the binder and magnesia used. Furthermore, while the brick B has the highest resistance to crack initiation due to thermal shock, the brick A proves to be the most suitable, taking into account the relationship between resistance to the initiation and propagation of cracks. A greater degree of strain to the level of the fracture stress is also presented in the bricks A and B. This is connected to their higher content of graphite (9-12 %) compared to brick C (~ 4 %).