关键词: 刚玉浇注料, 氧化铝微粉, 多级配比, 常温抗折强度, 加热永久线变化率

Abstract: Corundum castables often exhibit a decline in strength during medium and low temperature stages of baking and field application,which adversely affects their overall performance.To solve this problem,an optimization of the particle gradation by using multi-graded alumina ultrafines was proposed to enhance the structural stability and mechanical properties of the castables after medium and low temperature heat treatment.With tabular corundum and six types of alumina ultrafines with varying particle sizes (d₅₀ of 3.910,1.885,1.362,1.104,0.798,and 0.524 μm,respectively) as the main raw materials,a five fraction gradation was designed.Its effects on the cold modulus of rupture (CMOR),permanent linear change on heating,and microstructure were systematically investigated.The results show that:(1)the samples with one-fraction or two-fraction gradation of ultrafines exhibit a significant decrease in cold modulus of rupture after heat treatment at 600 ℃ compared with those treated at 110 and 400 ℃;(2)the samples with a five-fraction gradation of ultrafines demonstrate stable performance in cold modulus of rupture within the 400-1 200 ℃ range,significantly mitigating the strength drop problem commonly encountered around 600 ℃ in traditional single-ultrafine systems.Meanwhile,the high-temperature-treated samples present a denser microstructure and more stable permanent linear change on heating.This study provides an effective strategy for optimizing the medium and low temperature performance of corundum castables,demonstrating a good engineering application value.

Key words: corundum castables, alumina ultrafines, multi-fraction gradation, cold modulus of rupture, permanent linear change on heating