Magnesia-carbon (MgO-C) refractories are typically used in secondary metallurgy applications because of their excellent corrosion resistance against basic slags and high thermal strength. The contact area of the refractory and slag is usually the area of the refractory susceptible to corrosion during secondary metallurgy processes. In this master’s thesis work, the degradation mechanisms of different MgO-C refractory materials were investigated by using a lab-scale static crucible testing method. The major differentiating factor for the refractories is the different antioxidant composition of the refractories. Antioxidants are metallic additives like aluminium (Al) and silicon (Si) added to the MgO-C refractory to prevent carbon oxidation. Also, different slags with varying MgO slag content (wt. %) were used for the experiments. After the different experiments, samples from the reacted and infiltrated refractories were taken and used for the analysis of the main corrosion/ degradation phenomena.
Before structuring the design of the experiment, it was critical to have in-depth knowledge and understanding of different literature studies that had investigated similar topics. In chapter 2 of this thesis, a literature review was done to highlight various relevant topics ranging from steel cleanliness, non-metallic inclusions (NMIs) and their characterisation, secondary metallurgy processes, types of slags and refractory materials used in secondary metallurgy and the interaction between refractory (MgO-C) and slag/steel.
Based on the different inferences drawn from the literature review, an approach of the refractory/ slag interaction investigation was adopted, and the design of the experiment was done accordingly. Chapter 3 gives an overview of the research methodology used to perform the experimental part. Characterization and analysis of the experiment results was the main feature of chapter 4. The analysis was made on sub-topics on refractory and slag interaction at the interface, slag composition evolution and penetration of the slag into the refractory. Discussions on the various effects of the different parameters like dwelling time, slag composition and antioxidant composition of the refractory were done in chapter 5.