Abstract: The dense magnesia-calcia sand prepared with dolomite as the raw material by the two-step calcination method is a common refractory starting material of magnesia-calcia dry mix for tundishes.However,the two-step calcination method is complex and resource-consuming,and the dense magnesia-calcia sand is not conducive to improving the thermal insulation performance of the dry mix for tundishes.Magnesia-calcia dry mix samples were prepared using microporous dolomite calcined by the one-step method (1 400 ℃ for 3 h) and fused magnesia as the main raw materials and heat treating at 1 100 and 1 550 ℃,respectively.The effects of the microporous dolomite addition (0,15%,30%,45%,and 60%,by mass,respectively) on the properties of the samples were studied.The results show that with the microporous dolomite addition increasing,for the samples heat treated at 1 100 ℃,the linear shrinkage and bulk density show decreasing trends and the cold compressive strength increases first and then decreases;for those heat treated at 1 550 ℃,the linear shrinkage decreases first and then significantly increases,the apparent porosity increases,the thermal conductivity significantly decreases,however,the cold compressive strength and slag resistance decrease.With 60% microporous dolomite,the sample heat treated at 1 550 ℃ has the thermal conductivity at 800 ℃ of 2.410 W·m^-1·K^-1,decreasing by 51.9% compared with the traditional magnesia dry mix,and the cold compressive strength of 26.0 MPa,which shows excellent thermal insulation performance when the mechanical property is slightly reduced.

Key words: magnesia-calcia based, tundish, dry mix, dolomite, thermal insulation performance

摘要： 以白云石为原料,采用二步煅烧法制备的致密镁钙砂是镁钙质中间包干式料常用的耐火原料。然而二步煅烧法工艺复杂,资源耗费大,且致密镁钙砂不利于中间包干式料隔热性能的提升。以一步煅烧法(1 400 ℃保温3 h)制备的微孔白云石和电熔镁砂为主要原料,分别于1 100、1 550 ℃热处理后制备了镁钙质干式料试样,研究了微孔白云石加入量(质量分数分别为0、15%、30%、45%和60%)对试样性能的影响。结果表明:随着微孔白云石加入量的增加,1 100 ℃热处理后试样的线收缩率和体积密度呈减小趋势,常温耐压强度先增大后减小;1 550 ℃热处理后试样的线收缩率先减小后显著增大,显气孔率增加,热导率大幅降低,但常温耐压强度和抗渣性能降低。当微孔白云石加入量为60%(w)时,1 550 ℃热处理后试样在800 ℃下的热导率为2.410 W·m^-1·K^-1,与传统镁质干式料相比下降了51.9%,同时常温耐压强度为26.0 MPa,在力学性能略微降低的情况下表现出优异的隔热性能。

关键词: 镁钙质, 中间包, 干式料, 白云石, 隔热性能