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

Abstract

We report an investigation on the corrosion behavior of ZrO 2 -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 ZrO 2 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 90 min 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 (480 min), 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 ZrO 2 -graphite refractory insert.

Interface Wetting and Reaction Behavior between Mold Flux and Submerged Entry Nozzle under an External Electric Field

“…The commonly used methods to address the corrosion problem in the slag-line include optimizing the composition of mold flux, [7,11] using better corrosionresistant materials at the slag-line, [12,13] and adjusting the immersion depth of the nozzle continuously. However, the slag-line corrosion problem has never been resolved fundamentally.…”

“…Even with the increase in corrosion temperature and flow rate, the ZrO 2 particles in the slag‐line in CaO–Al 2 O 3 ‐based mold flux are not corroded or cracked severely. Kumar et al [ 13 ] improved the corrosion resistance of the slag‐line by adding an anticorrosion protective layer outside the slag‐line to prevent direct contact and reaction between mold flux and slag‐line materials.…”

Influence Factors of SEN Clogging of Rare‐Earth Steel Continuous Casting and Solve Ideas of Japanese Steel Enterprises

“…[11,12] In recent years, with the long-term unremitting efforts of metallurgical workers, the stability of RE-steel-smelting process has been greatly improved, and some steel enterprises have achieved stable production and application of high-performance RE steel. [13][14][15] Unfortunately, the inner-wall clogging problem of SEN has not been effectively solved in the process of RE steel continuous casting.…”

Optimisation of The Value in-use of The Refractory Submerged Entry Nozzle: Implication of preheating failures

“…Since refractories are high temperature resistant materials (i.e., good insulators), carbon is added into the material to improve its thermal conductivity and thermal shock resistance [10][11][12][13]. The carbon within the refractory SEN is protected by an outer glaze in the case of SEN at-least during its preheating stage heated correctly [1,14,15]. 2…”

“…The resolution used with μ-CT will be suitable for analysing the aforementioned pore structures [41]. For the purpose of profiling, the images will be preprocessed from the inner bulk material away from regions close to the protective coating which can chemically react with inner bulk material and affect the microstructure around it (i.e., on the edges closes to it) [14].…”