关键词: La(OH)₃, 活性MgO, 刚玉质浇注料, LaMgAl₁₁O₁₉, 抗热震性

Abstract: To address the poor thermal shock resistance of MgO-bonded corundum castables,MgO-bonded corundum castable samples were fabricated using tabular corundum and reactive alumina micropowder as raw materials,reactive MgO powder as the binder,and La(OH)₃ as the precursor.The prepared samples were cured at room temperature for 24 h,dried at 110 ℃ for 24 h,and finally heat-treated at 1 600 ℃ for 3 h.The effects of La(OH)₃ additions (mass fractions of 0,1.12%,2.24%,4.48%,and 8.96%) on the properties of the corundum castables were investigated.The results show that:(1)after drying at 110 ℃,the cold compressive strength of the castables first increases and then decreases with the rising La(OH)₃ addition,while the apparent porosity shows a continuous increasing trend;(2)after the heat treatment at 1 600 ℃,the cold compressive strength of the castables decreases gradually with the increasing La(OH)₃ addition,the permanent linear change on heating increases steadily,and the thermal shock resistance of the castables is enhanced first and then weakened;(3)the castables achieve the optimal comprehensive performance at the La(OH)₃ addition of 2.24%.Specifically,the MOR retention ratio reaches the maximum of 98.8% after the heat treatment at 1 600 ℃ for 3 h.This is attributed to the in-situ reaction between the introduced La(OH)₃ and Al₂O₃/MgO in the castables,which generates lamellar LaMgAl₁₁O₁₉.An appropriate amount of such lamellar phases can effectively deflect cracks induced by thermal shock and thereby improve the thermal shock resistance of the castables.

Key words: La(OH)₃, reactive MgO, corundum castables, LaMgAl₁₁O₁₉, thermal shock resistance