Effect of microporous dolomite on properties of magnesia-calcia dry mix for tundishes
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 micro-porous 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 ap-parent 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 tra-ditional 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.
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维普
