Effect of Hollow Corundum Microspheres Additive on Physical and Mechanical Properties and Thermal Shock Resistance Behavior of Bauxite Based Refractory Castable

Abstract

This paper analyses the effect of hollow corundum microspheres (HCM) on both physical-mechanical properties (density, ultrasonic pulse velocity, modulus of elasticity, and compressive strength) and thermal shock resistance behavior of refractory medium cement castable with bauxite aggregate. Moreover, the scanning electron microscopy (SEM) results of HCM and refractory castable samples are presented in the paper. It was found that the replacement of bauxite of 0–0.1 mm fraction by HCM (2.5%, 5%, and 10% by weight of dry mix) had no significant effect on the density and compressive strength of castable, while the modulus of elasticity decreased by 15%. Ultrasonic pulse velocity (Vup) values and the visual analysis of the samples after thermal cycling showed that a small amount of HCM in composition of refractory castable could reduce the formation and propagation of cracks and thus increase its thermal shock resistance.

Effect of hollow spheres on the properties of lightweight periclase‐magnesium aluminate spinel refractories

“…The MOR values of the samples also showed an increasing trend with increasing hollow spheres content. This was mainly because the mechanical strength of the samples was related to the sintering driving force between the raw materials, the combination state of the particles, and the strength of the hollow spheres 36 . The SEM analysis shown in Figure 8 demonstrates that pores appeared at the interface of sample M0 due to the difference in thermal expansion coefficients of the periclase and spinel phases.…”

Design, Manufacturing and Properties of Refractory Materials

“…αAl 2 O 3 hollow spheres with sizes 5-100 µm were introduced by Stonys et al [9] to bauxite refractory castables to check their influence on castable thermal shock resistance. In their study, additions of 2.5% and 5% of hollow Al 2 O 3 were found to improve the thermal shock resistance of castables, which withstood 30 thermal cycles, whereas a 10% addition caused their deterioration due to clustering, poor bonding of spheres with the surrounding matrix and formed irregular-shape voids.…”

A low bulk density, low thermal conductivity permanent lining castable for tundish obtained by adding pearlescent sand

“…In order to improve the thermal insulation performance of castables and reduce their heat storage loss, lightweight porous aggregates are often used instead of traditional dense aggregates. [4][5][6][7][8] At present, the representative high-strength lightweight aggregates include hollow corundum spherical aggregates, 9,10 lightweight microporous mullite aggregates, 11 and lightweight microporous bauxite aggregates. 12 The bulk density and thermal conductivity of the castables prepared with these lightweight aggregates are extremely low, but their key properties such as strength and thermal shock are still insufficient to meet the requirements of tundish permanent linings, and the prices of high-strength lightweight aggregates are much higher than that of traditional aggregates.…”