Effect of temperature on the slag/refractory interfacial reaction with directed reduced iron (DRI) addition in an electric arc furnace (EAF) process: Diffusional growth of magnesiowüstite layer by Boltzmann-Matano analysis

This study investigated the effect of temperature (1550–1650 °C) on the electric arc furnace (EAF) slag and magnesia refractory interfacial reaction with 20% direct reduced iron (DRI) addition as an alternative iron source in an Ar atmosphere. Variations in MgO content from initial to final stage were proportional to the temperature, indicating that MgO degradation by molten EAF slag was affected by the concentration gradient between initial and saturation conditions depending on temperature. In addition, the temperature affected MgO content more dominantly than DRI did. In other words, temperature control in an EAF process using DRI is relatively more important than the control of DRI itself for preventing MgO refractory degradation. The magnesiowüstite (MW) intermediate layer thickness and MgO refractory dissolution depth increased as the temperature increased because MgO solubility in molten EAF slag is proportional to temperature. Finally, the inter-diffusivity (D˜Fe−Mg, m2/s), which was estimated by Boltzmann-Matano analysis, ranged D˜Fe−Mg=10−12.0−10−12.5 and logD˜Fe−Mg generally decreased with decreasing temperature. The activation energy was found to be approximately 240 kJ/mol. Therefore, it can be concluded that suitable control of temperature in an EAF process using DRI is important to minimize refractory degradation.