Fundamental Investigations on the Corrosion of ZrO_2-C Refractories during Interaction with a Casting Mould Meniscus Slag

摘要

The degradation behavior of Zirconia - 20% carbon refractory was investigated during high temperature (1550℃) contact with a casting mould meniscus slag containing 50% MnO, 25% SiO_2, and 25% Al_2O_3. Using the sessile drop approach, the transient progress of corrosion reactions was investigated as a function of time; in-depth characterization and analysis of reacted assemblies was carried out using optical and scanning electron microscopy. Optical micrographs showed a significant penetration of slag within the refractory substrate, with very little slag remaining behind after 15 min of contact. In situ carbothermic reduction of zirconia and the presence of reducible oxides in the slag significantly depleted carbon from the substrate further aiding the penetration of slag. Interaction between slag and zirconia resulted in the depletion of phase-stabilizing Y_2O_3 from zirconia granules resulting in their fragmentation and subsequent diffusion in slag rich regions. An aggressive all-round corrosion was observed with extensive refractory degradation over a period of time; a number of reaction products such as Mn_5Si_3 were also observed. These experimental investigations were supplemented with thermodynamic investigations using FactSage.