Enhancing the Oxidation Resistance of Al2O3-SiC-C Castables via Introducing Micronized Andalusite

Abstract

Additions of andalusite aggregates (19 wt%) were shown in previous literature to enhance the antioxidation of Al2O3-SiC-C (ASC) castables. This work aims to investigate whether micronized andalusite has a greater influence on antioxidation improvement than andalusite aggregates. Various low contents (5 wt% and below) of micronized andalusite (≤5 μm) were introduced as a substitute for brown fused alumina in the matrix of ASC castables. The antioxidation of castable specimens was estimated by the oxidized area ratio on the fracture surface after a thermal shock test. The microstructure and phases of micronized andalusite and the castable specimens were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The results suggest that the antioxidation effects of ASC castables with a low addition of micronized andalusite are effectively enhanced. The heat-induced transformation of andalusite produces SiO2-rich glass, favoring the sintering of the castable matrix and impeding oxygen diffusion into the castable’s interior. Therefore, the castable antioxidation is enhanced without deteriorating the hot modulus of rupture.

Design, Manufacturing and Properties of Refractory Materials

“…Wang et al [12] tested the influence of 5 µm-andalusite addition on thermal shock resistance of Al 2 O 3 -SiC-C castables dedicated for the runners of blast furnaces. They found noticeably improved oxidation resistance and residual CMOR after 10 thermal cycles compared to castables without the addition.…”

Substitution of antioxidant Si by andalusite fine powder in Al2O3‐SiC‐C castables

“…7,8 In our previous work, the addition of a small amount of andalusite fine powder significantly improved the performance of castables, especially their oxidation resistance. 9,10 The silica-rich glass phase converted from andalusite can enhance sintering of the castables, and some of the silica-rich glass phase is extruded onto the surface of the particle to block the pores or react with Al 2 O 3 in the matrixes to form secondary mullite. These factors make the structure of the castable more compact, thereby preventing the intrusion of external oxygen and improving the oxidation resistance of the castables.…”