Abstract: To improve the performance of MgO-MgAl₂O₄-ZrO₂ refractories,the specimens were prepared by heat treatment at 1 650 ℃ for 3 h,using different magnesia raw materials as the aggregates and analytical pure MgO fine powder,α-Al₂O₃ micropowder,spinel fine powder and monoclinic zirconia micropowder as the matrix.The effects of different magnesia raw materials (97 sintered magnesia,97 fused magnesia,and 99 brine magnesia) on the mechanical properties,phase composition and microstructure of the specimens were studied.The results show that:(1)97 sintered magnesia and 97 fused magnesia contain high contents of impurities such as CaO and SiO₂,and generate liquid phases at 1 650 ℃,which promotes material sintering,resulting in high densification degree but reduced high-temperature performance;(2)compared with 97 fused magnesia,97 sintered magnesia has higher porosity,smaller grain size and higher activity,leading to excessive linear shrinkage of the material;99 brine magnesia has high purity,small grain size,high porosity,and large specific surface area and reactivity,which can react with the matrix to generate more in-situ spinel,reduce firing shrinkage,prevent crack propagation and improve the high-temperature mechanical properties of the material;(3)the specimen with 99 brine magnesia as the raw material has a bulk density of 3.04 g·cm^-3,an apparent porosity of 17.8%,a cold modulus of rupture of 7.4 MPa,a linear shrinkage of 0.73%,a hot modulus of rupture (held at 1 400 ℃ for 0.5 h) of 7.1 MPa,good thermal shock resistance,and the best comprehensive performance.

Key words: MgO-MgAl₂O₄-ZrO₂, brine magnesia, RH furnace, hot modulus of rupture

摘要： 为提高MgO-MgAl₂O₄-ZrO₂耐火材料性能,分别以不同镁砂原料为骨料,以分析纯MgO细粉、α-Al₂O₃微粉、尖晶石细粉及单斜氧化锆微粉为基质,经1 650 ℃保温3 h热处理制备MgO-MgAl₂O₄-ZrO₂耐火材料。研究了不同镁砂原料(97烧结镁砂、97电熔镁砂、99卤水镁砂)对试样力学性能、物相组成及显微结构的影响。结果表明:1)97烧结镁砂和97电熔镁砂中CaO、SiO₂等杂质含量高,并在1 650 ℃产生液相,促进材料烧结,使试样致密化程度高,但高温性能降低。2)97烧结镁砂原料较97电熔镁砂气孔率高、晶粒小、活性高,导致材料的线收缩率过大;99卤水镁砂原料纯度高、晶粒小、气孔率高,具有较大的比表面积和反应活性,与基质反应可生成更多的原位尖晶石,降低烧成收缩,且阻止裂纹扩展,提高了材料的高温力学性能。3)以99卤水镁砂为原料,试样体积密度为3.04 g·cm^-3,显气孔率为17.8%,常温抗折强度为7.4 MPa,线收缩率为0.73%,高温抗折强度(1 400 ℃保温0.5 h)为7.1 MPa,抗热震性良好,综合性能最佳。

关键词: MgO-MgAl₂O₄-ZrO₂, 卤水镁砂, RH炉, 高温抗折强度