Alumina‒ZnAl ₂ O ₄ spinel castable: Effect of in situ formed ZnAl ₂ O ₄ content

ABSTRACT Zinc aluminate spinel (ZnAl 2 O 4 , gahnite) is gaining importance as a spinel component in the alumina spinel refractory castables due to its excellent thermo‐mechanical and chemical properties. The present work investigates the effect of the amount of in situ formed ZnAl 2 O 4 spinel on the properties of cement‐bonded high‐alumina castable. ZnO was added in the castable composition at 4.4, 6.6, and 8.8 wt.% to form 10, 15, and 20 wt.% in situ ZnAl 2 O 4 spinel, respectively. The castable compositions were processed through conventional technique and heat treated at 110°C, 1000°C, and 1550°C. They were then characterized for various refractory properties, namely, bulk density, apparent porosity, strength at ambient and elevated temperatures, phase analysis, and microstructural study. The optimum ZnAl 2 O 4 ‐containing composition was further characterized for resistance against thermal shock and slag corrosion. The evaluated properties were compared against a high‐alumina castable (without ZnO), used as a reference. The results show that 10 wt.% in situ ZnAl 2 O 4 spinel‐containing castable has the optimum properties. The properties indicate that the Al 2 O 3 ‒ZnAl 2 O 4 spinel castables can substitute Al 2 O 3 ‒MgAl 2 O 4 spinel castables, especially for iron and steel industry applications.