关键词: 镁钙质, 中间包, 干式料, 白云石, 隔热性能

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