# Evaluation of Factors Affecting the MgO-C Refractory Lining Degradation in a Basic Oxygen Furnace
## 1 Introduction  
The global refractories consumption market is significantly influenced by the increase in steel production. The development and introduction of new steelmaking technologies are also reflected in the increasing demand for periclasc-carbon (MgO-C) refractories for basic oxygen furnace (BOF) linings [1]. The technological processes currently used for steel production place high demands on the refractory materials' quality parameters. The specific processes that take place during the steelmaking process, such as rapid temperature changes, changes in the composition of the slag, or the impact of heavy pieces of charged scrap, are destructive to the MgO-C refractory lining of the BOF [2]. This is why a great deal of emphasis is placed on maintaining the refractory lining during the campaign, which is associated with the ever-increasing consumption of refractory gunning material [3]. The internal working lining is not exposed to the same wearing factor at each point. For this reason, the BOF is equipped with a zonal lining containing several types of refractories. The properties of the refractories are dimensioned according to their specific use in each zone of the working lining. This ensures uniform wear and increases the life of the BOF refractory lining [4]. Nowadays, the main aspect of the basic refractories production program for the steel industry has shifted to unfired periclasc-shaped refractories bonded with organic binders with a carbon content of up to 7% and periclasc-carbon-shaped refractories with a carbon content of 7% to 30% [5]. In MgO-C building blocks, a carbon bond replaces the ceramic bond. This bond is provided by organic binders such as coal tar and syntheticresins. Pyrolysis leaves behind a carbon residue, which represents a high-temperature bond and part of the carbon component of the products. The specific feature of the carbon bond is that the graphite surface is not wetted by liquids, and the bond is formed through the periclase (MgO) component and the edges of the graphite crystals [6]. In addition, the MgO-C refractories are characterized by high refractoriness and excellent thermal shock and corrosion resistance, resulting from high thermal conductivity, low thermal expansion, low wettability of graphite, and high MgO refractoriness [7]. The basic MgO-C refractory lining of the BOF is chemically degraded by corrosion, slag penetration, and erosion. Among the mentioned chemical degradation methods, graphite oxidation (corrosion) contributes the greatest to the wear of MgO-C refractories. Oxidation increases porosity and decreases the strength and resistance of the MgO-C refractory to further exposure to the oxidizing agent [8]. Some authors have investigated the direct and indirect oxidation of graphite in MgO-C refractories [9; 10]. Direct oxidation (gas phase oxidation) is the main mechanism at temperatures below 1400 \({}^{\circ}\)C where carbon is consumed by gaseous oxygen (Equation (1)). The process of direct oxidation and decarburization of MgO-C refractory material with injected oxygen (O\({}_{2}\)) starts with the diffusion of oxygen through the gas layer to the decarburized MgO-O\({}_{2}\) phase interface, continues with the diffusion of oxygen through the decarburized MgO layer, followed by Equation (1) at the MgO-C-MgO phase interface, and finally the product of the CO reaction diffuses through the decarburized MgO towards the outer surface of the lining. It is true that with increasing temperature, the thickness of the decarburized layer increases, and the proportion of the total mass loss due to decarburization of the MgO-C refractory also increases. [11]. At temperatures higher than 1400 \({}^{\circ}\)C, indirect oxidation, or solid phase oxidation (Equation (2)), becomes the main mechanism, where carbon reacts with oxygen in solid MgO [12]. The gaseous products of the reaction diffuse through the pores of the lining to the refractory surface. Near the MgO-C surface, oxygen is at a higher partial pressure [11] than the products from Equation (2).