Structure Control and Evaluation of Effective Fracture Energy on Alumina-Magnesia Monolithic Refractories Prepared with CaO·6Al₂O₃ Aggregate

Abstract

Alumina-magnesium castable refractories are used for the inner walls of molten steel ladles. The main cause of damage to these refractories is thermal shock caused by rapid temperature changes during the loading and unloading of molten steel. Therefore, the thermal shock damage resistance coefficient R'''' is a parameter that expresses the resistance of refractories to thermal shock, and the evaluation of effective fracture energy is important for improving R''''. In this refractory, CaO·6Al₂O₃ (CA6) is formed from the raw materials alumina and alumina cement; CA6 has the advantage of inhibiting crack propagation and improving mechanical properties. On the other hand, CA6 has the disadvantage of volumetric expansion during formation. Therefore, microstructural changes caused by the formation of CA6 significantly affect the mechanical properties of refractories. In this study, CA6 was used as raw material and replaced with CA6 generated in-situ. The amount of coarse-grained alumina added was adjusted to control the microstructure. The effect of the microstructure change on the effective fracture energy was then evaluated. As a result, the effective fracture energy was improved in the sample with more coarse-grained alumina added, due to the replacement of CA6 aggregate.