Preparation And Investigation Of High-density Sintering Magnesia

As the basic raw refractory, the bulk density of magnesia has an important effect on the properties of magnesia refractory, especially on the properties corrosion resistance and high-temperature strength. The service lives of metallurgical furnaces are remarkably extended with refractories produced by high-density and high-purity magnesia. The huge amount of market demand makes the research of magnesia become a hot spot.Taking the light calcined magnesia form south of Liaoning province as raw material, the process of preparing high-density sintering magnesia was surveyed. The effects of making conditions on properties of sintering magnesia were also investigated in this paper. Meanwhile, the microstructure of magnesia powder and sintering magnesia were observed. The conclusions are as follows:(1) Hydration treatment is one of important factors which affect the property of sintering magnesia. It reduced the impact of the magnesite pseudocrystal on the light-calcined magnesia and increased the bulk density of sintering magnesia. At the same time, the particles became more easily broken. So they reduced the grinding time and improved the production efficiency.(2) In order to get high-density sintering magnesia, the light calcination temperature in the process of magnesium hydroxide should be controlled. High temperature will reduce the activity of magnesia while low temperature is not conductive to the breakdown of magnesium hydroxide pseudocrystal. All of them will affect the properties of sintering magnesia. Taking into account the bulk density of sintering magnesia, the optmium calcination temperature was 850℃.(3) Forming pressure has a certain impact on the bulk density of the sintering magnesia. With the increase of the forming pressure, the bulk density of the sintering magnesia also increased correspondingly. The impact of the pressure on the density of sintering magnesia was not obvious when it is over 300MPa.(4) The process of grinding damaged the pseudocrystal of the powder particles and improved the bulk density of the sintering magnesia. Obviously two-step grinding processes seriously damaged the glomeration among the magnesium hydroxide crystals and the pseudocrystal of magnesia, which efficiently reduced the chance of the existence of secondary porosity and improved the bulk density of the sintering magnesia.(5) The magnesium hydroxide after hydration experienced the process of grinding-calcined-grinding-forming-sintering, then lightly calcined at the temperature of 850℃for an hour and formed at the pressure of 300MPa, finally sintered at the temperature of 1600℃for two hours. The high-density sintering magnesia would obtain with the bulk density of 3.46g/cm3.