Effect On Properties Of Magnesia Calcium Refractory Materials Of Additives

In accordance with international standards, definition of refractory material which is inorganic chemistry and physical properties allow its use in high temperature environment such as non-metallic materials, or containing a certain proportion of metals, as well as metallic oxides which are a class of materials and products. At present, the refractory materials are widely used, such as continuous casting tundish lining, AOD, VOD furnace, furnace, electric furnace, converter and large dry process cement kiln burning zone and other high-temperature industrial equipment lining, etc.. Because of its high temperature resistance, slag resistance,thermal shock resistance, high temperature vacuum stability, purification of steel liquid and other advantages, it is widely paid attention to by iron and steel enterprises.MgO-CaO refractories have a series of excellent performances, but easy to be hydrated limits the application of the material.To vigorously develop the use of MgO-CaO refractories, adding a small amount of additives, high temperature firing or two step calcining, sealed packaging, production process control are needed. All of the above methods can reduce the hydration of magnesium calcium based materials in different degrees, and the additive method is widely adopted at present.My research project mainly uses light burning dolomite as raw materials,adding a certain proportion of Al₂O₃, Fe₂O₃ and ZrO₂ is to study the effect of alumina, iron oxide and zirconia on the properties of magnesia calcium refractory materials. The samples were prepared by high temperature sintering at different temperatures, and the bulk density, water absorption, open porosity, water weight gain rate and powder rate, XRD and scanning electron microscope, energy spectrum analysis and other physical tests were carried out. There are three aspects:（1） Fe₂O₃,Al₂O₃ as an additive to change the amount of Al₂O₃, Fe₂O₃ addition and change the temperature, the preparation of MgO-CaO-Fe₂O₃ and MgO-CaO-Al₂O₃ refractorymaterials.（2） Fe₂O₃+Al₂O₃ as a composite additive to change the amount of the compound additive and the change of the temperature.the MgO-CaO-Al₂O₃-Fe₂O₃ four binary system refractory materials are prepared.（3） Al₂O₃-Fe₂O₃-ZrO₂ as a additive, changing alumina and ferric oxide and zirconia addition and sintering temperature of MgO-CaO-Al₂O₃-Fe₂O₃-ZrO₂ five binary refractory material system.The test results show that:（1） for a single additive Al₂O₃,when sintering temperature is 1500 and the additive content is 30%, sampes are promoted to be sintered most.（2） for a single additive Fe₂O₃ and Fe₂O₃+Al₂O₃ composite additive,high sintering temperature and high additives content is more helpful to promote the sintering of samples.（3）for the composite additive Fe₂O₃+Al₂O₃+ZrO₂,when adding ratio is 1.2%Fe₂O₃+12%Al₂O₃+10%ZrO₂, the samples are promoted to be sintered most.（4） Hence properties of dolomite with composite additives are superior to the single additives.This topic is to solve the problems existing in the enterprise production, the dolomite refractories as the research object, the introduction of single and compound additives to improve the sintering properties of dolomite, water resistance,performance excellent mgocao refractory material was prepared, for preparing high performance dolomite based refractories provides useful reference. Through the above analysis and discussion, and experimental conditions in this paper, we can draw the following conclusions:（1） the single addition of Fe₂O₃ or Al₂O₃, can significantly improve the sintering of dolomite. At the same sintering temperature, the volume density increases with increasing the mass fraction of Al₂O₃. When the mass fraction of Al₂O₃ was 30%, the volume density reached the highest value and the porosity of the lowest water increase weight and powder rate is the lowest. Continue to increase the mass fraction of Al₂O₃, bulk density decreased, the porosity increases, increasing weight rate and the rate of powder of water also increases. This is due to the formation of relatively easy to be hydrated calcium aluminate results. Reasonable increase of sintering temperature can significantly improve the water resistance of the material;（2） Fe₂O₃-Al₂O₃ composite added when can more effectively improve the white jade of sintering and hydration resistance capability of material get furtherimprovement, and the third group is divided into the introduction of ZrO₂ additives can not only improve the material of hydration resistance, but also can improve the material of high temperature performance, but also may improve the material slag corrosion resistance performance;（3） the introduction of Fe₂O₃ and Al₂O₃ is a priority to the formation of Fe Ca or Al CA compounds with the CaO reaction of the decomposition products of dolomite.The main form of calcium aluminate three C₃ A alumina content is low, the content of Al₂O₃ will weaken the formation of hydration resistance ability of CA in 30-50%.Under the high temperature of Fe₂O₃ and Al₂O₃ will form a magnesium iron spinel MgFe₂O₄ or magnesium aluminate spinel MgAl₂O₄ and MgO reaction, is conducive to improve the materials at high temperature and hydration resistance. The introduction of the third components of additive ZrO₂ only react with calcium oxide to form CaZrO₃ to further improve the water resisting capability of material.