In the dry process of powder pressing, as described in several previous reports, physical and chemical properties of green body after pressing, have been observed to be affected by molding conditions and powder characteristics. In this report, we have further considered the changes of internal states of pressed green body on the hardness distributions and powder movements.
Flow of powder under pressing was investigated by photographs of the layer by layer method. Then the locus of individual powder translations was recognized to be accomplished as parabolic (surface) flow whose principal curvature increases with applied pressures and frictions between powder and the die wall. On representation of hardness applied in this experiment, degree of hardness (R^-1) would be proportional to the elastic deformation (δ) of body at the position of measuring and has been formulated as the following equation,
R^-1=2kt/p(δ)
where, p is the applied pressure on drilled edge, k the constant of elastic deformation of green body and t the width of drill teeth.
In hardness distribution, we pointed out existence of “Equi-flow of Hardness” along which the tendency of hardness distribution becomes contrary and that most of the defects of body, such as lamination and peel-off, would occur in general at the positions along this flow surface.
6 Figs, 2 Tables, 6 References.

抄録全体を表示

In the previous report, concerning with powder-pressing in ceramic industry, hardness distributions in pressed green bodies, Equiflow of hardness and physical meaning of drilling hardness were studied.
In this report, we have further investigated the effects of applied pressure on the hardness distributions in green bodies.
As the cylindrical specimens were pressed from one side, we have measured the hardness at the positions of center and circumference of press side surface, O₁ O₃ and that of bottom, U₁U₃ and then the ratio of γ33, γ11, respectively.
Keeping the charged powder weight in constant value but varying the applied pressures from 100kg/cm², we have formed relations between each hardness and height of green bodies. Moreover, such a group of curves were further established for several powder weights from 6g to 28.2g.
As a result of such experiments, we have distinctly found that the order of hardness O₃>O₁>U₁>U₃ which represents at the normal state of pressure and powder weight, gradually changed in the order O₃>U₁>O₁>U₃ with increase of pressure or decrease of powder amount, and finally all these hardness curves fall on the same line, which is the specific curve having an inflection point.
Moreover, the observation on the changes in hardness ratio, γ33 was made. 8 Figs., 2 Tables, 4 References.

抄録全体を表示

The new expansion coefficient factorsbased upon the cationic percentages are derived from the structural consideration of the random network theory on glass. Two sets of values are given, one for the temperature range from room temperature or 0°C to approx. 100°C and the other for the range from room temperature or 0°C to approx. 400°C. The new factors are compared in the lower temperature range with those of Winkelmann and Schott, English and Turner, Gilard and Dubrul, and in the higher temperature range with those of Danzin for various systems of glasses, such as Na₂O-CaO-SiO₂, Na₂O-Al₂O₃-SiO₂, Na₂O-B₂O₃-SiO₂, and with commercial glasses, such as metal sealing glasses. It is shown that the new factors can be applied to wider ranges of glass composition with smaller errors of calculation.

抄録全体を表示

In continuing the previous reports (This Journal, 60 [677], 476 (1952); 61 [683] 207 (1953)), in the present paper were reported the results of studies on comparative tests of silica refractories by mixing the Mikawa quartzite with (1) other quartzites: Fujimaki Akashiro quartzite and Akaba quartzite used in the former reports, and (2) some mineralizers used in the previous trials: dolomite, hematite, basic slag and sea-water magnesia. The Mikawa quartzite and other quartzite raw materials above mentioned, were used to make test silica bricks as following: (1) the Mikawa quartzite mainly in the fine grain part, and (2) the Fujimaki Akashiro quartzite and Akaba quartzite in coarse grain part, the latter quartzites being easily heat inversible. To these mixtures were added some parts of mineralizers above mentioned and the cherty part of the Akaba quartzite above used.
Many test samples of silica refractories were prepared by these two series of mixtures, and many comparative tests were carried out on variuos physical and thermal properties by discussing on the following points.
(1) From the special formation of the Mikawa quartzite and the test results obtained heretofore in the comparative studies on the refractories by graining only the Mikawa quartzite, it cannot be obtained suitable silica brick for steel industry.
(2) By using fine grains of the Mikawa quartzite to make matrix part, it can be succeeded to improve the refractoriness, resistance to slag corrosion, softening temperature under load, etc.
(3) In this case, it is desirable to use the coarse grain parts of the so-called Akashiro or Aoshiro quartzite, and the Mikawa quartzite cannot be used for mixing over a certain limiting amount.

抄録全体を表示