Medium grain size ammonium paratungstate means the ammonium paratungstate that has apparent density under the range of medium particle size, such as at the range from 1.65g/cm3 to 1.90g/cm3.
It is necessary to control the particle size of ammonium paratungstate in the process of powder metallurgy to ensure the uniformity of tungsten powder. At present, ammonium paratungstate is often prepared by evaporative crystallization method at home and abroad. However, the APT produced by conventional evaporative crystallization process has relatively coarse and uneven grain size. And the apparent density is generally at the range of 2.2-2.5g/cm3.
The medium grain size ammonium paratungstate may be produced by controlling crystallization temperature, stirring time, end-point of crystallization and other process conditions in the process of crystallization, and combining with the characteristics of the existing processing equipment to fully control the number of grains, inhibit the growth of crystal nucleus. And purity of the product can be fully improved. The ammonium paratungstate produced by this method has the characteristics of high crystallization rate, stable quality and easy control of production process.
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