Application of a protective coating based on magnesium hydroxide to reduce oxidation of the side surface of graphitized electrodes in electric arc furnaces

Abstract

When steel is smelted in electric arc furnaces, and during its subsequent treatment in ladle-furnace units, a significant amount of power is required. This power is supplied through the use of graphitized electrodes, which are pivotal for achieving the required temperatures. However, these electrodes are costly, significantly affecting the overall production costs. Therefore, efforts to reduce the cost of steel by minimizing the consumption of graphitized electrodes are crucial for metallurgists.

The primary factor influencing the consumption rate of these electrodes is their surface oxidation by oxygen present in the furnace atmosphere. Recent studies have shown that a magnesium hydroxide-based coating can significantly mitigate this issue. When applied to the surface of graphitized electrodes, this coating was shown to reduce their weight loss by 30–40% at the test temperature in an oxidizing atmosphere. Notably, as the temperature increases, so does the benefit of this weight loss reduction.

The efficacy of the tested can be attributed to its unique properties. Upon application to a graphitized electrode’s surface, the coating material penetrates deeply into the pores, effectively sealing them and forming a protecting layer over the surface. As the temperature rises, water within the coating evaporates, leaving behind a highly adhesive residue. At 350 °C, the Mg(OH)₂ in the coating decomposes to form MgO, which has a melting point of 2850 °C. This results in a high-density coating that acts as a barrier against atmospheric oxygen, thereby significantly slowing down the rate of graphite oxidation in the electrodes.