Abstract
The hydrostatic packing characeristics on several kinds of powders, i.e. electrolytic copper, electrolytic iron, reduced iron, atomized iron, molybdenum and tungsten, are studied.
Both Kawakita's and Athy's equations that are used as the relations for the process of uniaxial die pressing have been examined to see whether they are applicable to the hydrostatic packing. Consequently, the process of hydrostatic compacting appears to support Kawakita's eq. in low pressure range, and Athy's eq. in high pressure range.
In Kawakita's eq., the characteristic constant“a”corresponds to initial porosity, and the constant“1/b”appears to relate with the particle strength.
On all the powders tested, three stages are recognized on the curve of (P/p)·(V-V∞)/(Vao-V∞) versus (Vao-V)/(Vao-V∞), where P is the compacting pressure, p the constant, V-V∞ the volume of residual porosity, Vao-V∞ the volume of initial porosity and Vao-V the volume of loss porosity. To substitute σt/P for the parameter (P/p)·(V-V∞)/(Vao-V∞) in the relation, the shape of the curve is made similer to that described above, where σt is the tensile strenght of compacts. These three stages appear to correspond to the different packing mechanismus, respectively.
