Thermal chemical erosion behavior of the burning-free Al2O3–C–Si bottom nozzle

Abstract

Burning-free Al2O3–C–Si bottom nozzle, a key refractory component connecting the intermediate ladle slide to the immersion spout, is always prone to failure under the extreme environment of repeated exposure to chemical attack and thermal shock of the steel. Here, an approach of adding Si powder and the change in Al2O3 aggregate aims to enhance the product's quality and performance of the burning-free Al2O3–C–Si bottom nozzle. And the different composition ratios effects on the chemical erosion behavior of the burning-free Al2O3–C–Si bottom nozzle were investigated based on the measured instantaneous thermal-expansion coefficient and young's modulus of the bottom nozzle materials in the high-temperature range of 300–1473 K. Moreover, the high-temperature folding resistance, thermal-shock resistance test and slag resistance experiments have also been probed. Obtained results reveal that the absence of 6 wt.% Si can promote the formation of SiC phases in the form of flakes and whiskers inside the bottom nozzles, which significantly improves the density, strength, thermal shock resistance and slag erosion resistance of refractory materials. Compared with the bauxite-Al sample, the slab corundum-Si-Al sample reduced the porosity by 7.8% and the erosion index decreased by 4.7% due to the formation of SiC and a thin protective layer of SiO2, as well as the mullite crystals structure. Here, an optimized bottom nozzle with a composite structure has also been proposed. This work can make significant contribution to improve the performance of burning-free refractory materials, bottom nozzles and reducing costs.