Wear mechanism of a novel Al-Si-MgAl2O4-Al2O3 composite used in the low vessel of an RH secondary refining furnace

摘要

A novel Al-Si-MgAl2O4-Al2O3 composite brick was prepared and evaluated in the low vessel of an RH (the initials of Ruhrstahl and Hereaeus) secondary refining furnace; it was characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The results show that after use, the Al-Si-MgAl2O4-Al2O3 composite has a functional gradient with an erosion zone reinforced zone original zone phase distribution, in which the phases in the erosion zone (0-1.8 cm) are a Mg-hercynite spine] solid solution, alpha-Al2O3, and minor amount of Al3Fe5O12. Furthermore, the phases in the reinforced zone (1.8-5.0 cm) are gamma-AlON, 21R-SiAlON, SiC, Mg0.388Al2.408O4, and alpha-Al2O3; i.e., the Al and Si in the composite are completely converted into non-oxide reinforced phases. Finally, the phases in the original zone (> 5.0 cm) show no change. The reaction mechanism is as follows. During operation, a Mg-hercynite spine] solid solution is formed in the erosion zone due to a reaction between MgAl2O4 and FeO from a refinery operation. Therefore, the slag erosion of the material is improved. The Al and Si metals undergo active oxidation, and 21R-SiAION flakes are subsequently formed from the products of the metastable Al2O(g), SiO(g), and N-2(g) in the ambient. The gamma-AlON is formed by a carbothermal reduction nitridation of the alpha-Al2O3 and residual active carbon from the resin binder. The 21R-SiAION and gamma-AlON reinforce the composite brick and improve its high temperature performance accordingly. Its service life is 110% that of the magnesia-chrome bricks used in the same period. The reaction model was also established.