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 %).
Highlights
MgO-C refractory bricks are widely used in steel industry, the primary consumer of refractory linings, such as basic oxygen furnaces, electric arc furnaces, and ladle furnaces
The main properties which determine the resistance to the refractory thermomechanical degradation are the stiffness, the fracture resistance, the thermal expansion coefficient and the thermal conductivity
The antioxidants are added to MgO-C refractories in order to suppress their oxidation rate due to graphite content, which is oxidized in air atmosphere at high temperature, generating pores in the material structure
Summary
MgO-C (magnesia-carbon) refractory bricks are widely used in steel industry, the primary consumer of refractory linings, such as basic oxygen furnaces, electric arc furnaces, and ladle furnaces. The steelmaking requires extreme chemical, thermal and mechanical conditions that demand a high performance of materials, able to withstand the action of the steel bath and slag [1]. These working conditions produce refractory wear through various related processes. The main properties which determine the resistance to the refractory thermomechanical degradation are the stiffness (evaluated by the Youngs modulus), the fracture resistance, the thermal expansion coefficient and the thermal conductivity The properties of these materials are subject to the percentage, size and quality of raw materials from which they are manufactured. The compositions contain 80-93 wt% MgO, between 7-20 wt% graphite and 2-3 wt% of antioxidants [3]
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