Research On Perparation Of Silicon Steel Magnesia By High-purity Magnesium Hydroxide

ABSTRACT:Silicon steels sheet, including non-oriented silicon steels sheet and oriented silicon steel sheet, have great potential for electrical appliances and device applications such as transformers and motor cores because of their high eletrical resistance, extremely low magnetostriction, and low magnetocrystalline anisotrpy. As a coating material used for preparing oriented silicon steel sheet, silicon steel grade magnesium oxide is mainly used in the process of high temperature annealing of oriented silicon steel sheet and serves as release agent, insulation layer to improve the insulation performance of silicon steel and reduce the degree of wear of silicon steel sheet.Silicon steel grade Magnesium Oxide also has important applications in precision ceramics industry, aerospace industry, eletronic industry and other fields. This paper studied three different methods to produce silicon steel grade magnesium oxide that magnesium hydrate was used as raw material.First, the silicon steel grade magnesium oxide was prepared by calcined magnesium hydroxide. During the calcination process, the smaller size of solid particles easily sintered together, when the calcination temperature is950℃above.Second, the silicon steel grade magnesium oxide was prepared by magnesium hydrate carbonation-calcination two-step process. The research results of carbonization of Magnesium hydroxide by ammonium acid carbonate show that the morphology of precursor is rod with a small amount of sheet surface, when the reaction temperature is40℃; the morphology of precursor is rod made of sheet, when the reaction temperature is60℃; the precursor is spherical particles with a amount of sheet surface, when the reaction temperature is80℃. this process was a dissolution-reprecipitation process. The impotant thing is that this carbonization process could reduce the proportion of small partickes sintering during the calcination process. Under the optimal conditions, the purity of magnesium oxide produced exceeded99%, the apparent specific volune was4.2mL/g, and the median diameter of particles is2.09μm.Third, the light burned magnesium hydroxide, hydration, carbonation, calcination four-step process, preparated tending to irregular spherical particles, was researched. During the hydration process, the particles could become smaller. The precursor particles, which was preparated by carbonating magnesium hydroxide that made by hydration process, tended to be irregular spherical consisting of thin slices,as the reaction temperature was80℃. Magnesium oxide was recrystallized, leading to particles into aggregates consistent grain orientation, when the presoma was calcinated under high temperature. Under the optimal conditions, the purity of magnesium oxide produced exceeded99%, the apparent specific volune was4.4mL/g, and the median diameter of particles is2.32μm.