| The use of MgO-Cr2O3 refractory is becoming more limited day-by-day with the raised environmental awareness of the whole society. It is an inevitable trend for developing chrome-free refracroty in the refractory industry. The fabrication and properties of MgO-ZrO2 refractory have been studied in this paper. Firstly, the reaction processes among each component and the phase composition in MgO-ZrO2 refractory have been investigated by mean of thermodynamic calculation and phase equilibrium diagram. The phase composition has been cleared under different condition. Secondly, the fused MgO-ZrO2 material has been synthesized by using electrofusion method with light calcined magnesia and zirconite as raw materials. The microstructure formation process of the fused MgO-ZrO2 has been studied. Thirdly, the effects of ratio of monoclinic zirconia and desiliconization zirconia, content of fused MgO-ZrO2 compound and particle size distribution on conventional physical and chemical properties, high temperature bending strength and slag corrosion resistance of MgO-ZrO2 refractory have been investigated. In addition, the effects of Y2O3 CaO additives on the properties of MgO-ZrO2 refractory have also been studied. And the fabrication process and properties of MgO-ZrO2 refractory have been cleared. At last, the erosion behaviors of high basicity and low basicity slag on MgO-ZrO2 refractory have been investigated by using the rotation slag corrosion method. The corrosion mechanism has been disscused. The main results are as follow.(1) CaZrO3 cannot exsit in the system of MgO-ZrO2 refractory when the ratio of CaO and SiO2 is greater than 2. The main phases are MgO, ZrO2 and its solid solution. The phase in combination area depends on the ratio of CaO and SiO2, including forsterite, monticellite, manganolite and dicalcium silicate. When the ratio of CaO and SiO2 is lower tha 2, CaZrO3 could be generated.(2) In the low content CaO area of fused MgO-ZrO2 material, which fabricated by using electrofusion method with light calcined magnesia and zirconite as raw materials, SiO2 exsits by the form of 2MgO·SiO2. But in the high content CaO area, SiO2 exsits as MgO-SiO2-CaO glass phase. MgO in the ZrO2 solid solution will be separated out in the process of cooling, and magnesia rich forsterite could be formed around the ZrO2 grains. When using fused MgO-ZrO2 material as the only combination phase to fabricate the MgO-ZrO2 refractory, the high temperature bending strength and slag corrosion resistance are lower than MgO-Cr2O3 refractory.(3) When the ratio of monoclinic zirconia and desiliconization zirconia is 8:2 and the content of fused MgO-ZrO2 compound is 24%, the high temperature bending strength of MgO-ZrO2 refractory is high and its slag corrosion resistance is good. But if the ratio of monoclinic zirconia and desiliconization zirconia is invariant, the quantity of cracks increase as the content of fused MgO-ZrO2 compound increasing. When its content is 12%, the high temperature bending strength and slag corrosion resistance index are high.(4) The compression strength and high temperature bending strength of MgO-ZrO2 refractory increase as the ratio of aggregate and fine powder increasing. But there are more surface cracks in the refractory which will affect its slag corrosion resistance property. As a result, the ratio of aggregate and fine powder should be 1.63.(5) When the content of Y2O3 additive is 1%, the apparent porosity and gas permeability of MgO-ZrO2 refractory will be reduced obviously, and its bulk density, compression strength, high temperature bending strength and slag corrosion resistance will be promoted. But if the content of Y2O3 additive increases continually, more cracks will be formed and its application properties will be reduced.(6) The use of MgO-CaO powder as additive to fabricate MgO-ZrO2 refractory could promote its bulk density and compression strength, but its high temperature bending strength reduced obviously. If using fused magnesia which CaO/SiO2>2 to replace commonly fused magnesia as raw materials, not only the bulk density and compression strength will be promoted, but also the high temperature bending strength, slag corrosion resistance and thermal shock ability.(7) The slag corrosion resistance ability of MgO-ZrO2 refractory is obviously higher than MgO-Cr2O3 refractory after high basicity molten slag corrosion. The slag corrosion resistance mechanism is that a dense slag film which containing high melting point compounds, such as 2CaOSiO2 and Mg(Al, Fe)2O4 can be formed firstly after the contact of molten slag and brick. When the molten slag permeates into the brick continually, the CaO in the molten slag will react with ZrO2 to form CaZrO3 dense layer.(8) The slag corrosion resistance ability of MgO-ZrO2 refractory is obviously lower than MgO-Cr2O3 refractory after low basicity molten slag corrosion. The main resons are that a dense slag film which containing low melting point MgO-CaO-SiO2 glass phase will be formed firstly after the contact of molten slag and brick. The slag film will be melted rapidly to the molten slag. And because the basicity of molten slag is low, the ratio of CaO and SiO2 in the brick will be lower than 2, the CaZrO3 dense layer will not be formed. |
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