Effect of Glaze on the Corrosion Behavior of ZrO2-Graphite Insert of the Submerged Entry Nozzle in the Continuous Casting of Steel

摘要

We report an investigation on the corrosion behavior of ZrO2-graphite insert in submerged entry nozzles (SEN) during its high temperature interaction with the mould flux focused specifically on the role of glaze coating. A detailed metallographic examination of the representative samples collected at different stages of its usage was carried out to examine the transient progress of corrosion. The interaction between the glaze material and the base refractory at the typical preheating temperature of SEN initiated the degradation of the partially stabilized ZrO2 grains due to the formation of reaction products. Clear evidence is presented to show that the reaction product and the original layer of glaze coating survived after 90min of casting. Early stages of corrosion involved the progressive congruent dissolution of reaction products and the residual glaze phase into the mould flux. Due to the absence of the glaze layer in the later stages of operation (480min), corrosion was caused by the fragmentation of the aggregate phase and structural damage. This work highlights the importance of compositional control and coating thickness of the glaze material on the ZrO2-graphite refractory insert.