Effect of tundish fluxes on the degradation of MgO-based refractory linings in continuous casting process

초록

The corrosion of MgO-based tundish refractory linings due to the addition of various fluxes, such as rice husk ash (RHA) insulation powder, and RHA + CaO-Al2O3 flux (RCA), were investigated using a finger rotating test (FRT) at 1773 K, which simulated the industrial tundish metallurgy process involved in producing stainless steel. FactSageTM (ver. 8.2) thermochemical computing software was used to reveal the degradation mechanism of MgO-based refractory lining. Local corrosion was observed at the slag-metal interface after 60 min of RHA insulator addition. However, the refractory rod was fractured after the addition of the RCA multi-flux. Olivine, (Mg,Fe,Ca)2SiO4, and chromium-spinel, (Mg,Mn,Fe)Cr2O4, phases were predicted to form at the slag-refractory interface when the refractory was corroded by the RHA insulator, while the aluminum-spinel, (Mg,Fe)Al2O4, phase was simulated when corroded by RCA multi-flux. The different physicochemical properties of the liquid slag significantly influenced the corrosion of the refractory lining. The liquid slag compositions after 60 min of RHA insulator and RCA multi-flux addition can be classified as the SiO2-MnO-MgO-10%Cr2O3 system (RHA-S) and the SiO2-Al2O3-CaO-10%MgO system (RCA-S), respectively. Interfacial tension between the RCA-S and liquid stainless steel was higher than that between the RHA-S and liquid stainless steel. Nevertheless, the RHA-S had a greater contact angle and viscosity compared with RCA-S. These results indicate that the penetration depth of the RCA-S into the refractory was larger than that of RHA-S under a fixed radius of the capillary and a fixed penetration time, creating the more severe corrosion of the refractory by RCA-S than RHA-S.

키워드