The Properties of moulding sand are highly influenced not only by the grain size of the sand, but also by its grain size distribution. However, the fineness number which is often used for measuring moulding sand does not express the grain size distribution given by the author as follows:
            log W=N log N−??N_i log N_i
log₁₀ W goes near zero when the grain size distribution shows a high peak height at a specified size, while it approaches 117 when the grains are distributed over wider ranges. If sand consists of grains of a single size, log₁₀ W is always zero regardless of the grain size. The apparent specific volume of moulding sand is changed by mixing and the change is given by
              Sm=S_A+K_s??N'_i log₁₀ N'_i
where S_A is the total of the apparent specific volumes of components of different sizes and N_i shows the weight ratio of those components. Constant K_s is determined by experiment. In case of binary sand, the formula becomes
      Sm=(0.663 N'_i+0.636 N'₂)+0.156(N'₁ log₁₀ N'_i+N'₂ log₁₀ N'₂)
Permeability of mixed sand is given by
            Fm=Km(D₁N'₁+D₂N'₂+D₃N'₃⋅⋅⋅)²
              Km=K_D+k??N'_i log₁₀ N'_i,
where D₁, D₂, ⋅⋅⋅ are the diameters of components. In case of the permeability of binary sand, the formula becomes
      Fm=(D₁N'₁+D₂N'₂)²(2,600+5,680(N'₁ log₁₀ N'₁+N₂ log₁₀ N'₂))
Wet permeability of green sand mixed with bentonite is similarly given by
      Fm=(D₁N'₁)²(2,600+9,300(N'₁ log₁₀ N'₁+(1−N'₁)log(1−N'₁)))
The validity of these equations is well proved by experiment.

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  When molten aluminium is cast into the sand mould, it absorbs gases produced by the mould reaction. These gases cause often the undesirable defects in cast materials.
  We studied on the mould reaction in the case of pure aluminium and reported already in the last paper that various factors have an effect on the gas absorption by the mould reaction. Moreover, in the present report, we made clear effects of silicon content on the gas absorption by the mould reaction.
  Results obtained are as follows:
  (1) Effects of casting temperatures (700-800°C) are the same as these in pure aluminium. Namely, gas content in samples increases as casting temperatures rise and defects are more remarkable.
  (2) The changes of moisture content in the moulding sand (8-16%) do not have any clear relative relations with the percentage porosity, but it decidedly has bad effects on cast materials.
  (3) Effects of silicon content in Al-Si alloys are as follows:
  (i) In comparison with pure aluminium, Al-5%Si alloy contains far less gas content. This shows that the mould reaction is not restrained chemically by silicon and that the liquidus-solidus interval in alloy promotes the escape of gases absorbed by the mould reaction.
  (ii) In Al-10%Si alloy, gas content increases. Because the escape of gases is restrained in order that this alloy, whose composition is near to the eutectic composition, has the same solidification type as that of pure aluminium.
  (iii) In Al-15%Si alloy, gas content increases more. In this alloy which has broad solidification interval, silicon primaries crystallize first and form the new interface. Accordingly some gases gather to this interface and cause voids, and some gases form volatile compounds as SiH₄. By this reason, gases rater remain in the sample without escape and gas content increases.
  (4) By the microscopic observation, in Al-5%Si alloy, the canal-like porosities along the grain boundaries are observed.
  On the other hand, in Al-10% and-15%Si alloys the spherical porosities are detected and in the case of the latter some porosities are found adjascent to primary silicons as if silicon primaries exert as nuclei.

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  The eutectic cell count in cast iron is regarded as a measure of nucleation at eutectic solidification, and so this is one of the important factors determining the soundness and mechanical properties of casting. There are various methods proposed to delineate eutectic cells. However it is not always easy to reveal them, depending on the contents of sulfur and phosphorus or structure of matrix etc.
  The authors studied to etch eutectic cell structure in cast iron by means of potentiostatic technique. As a preliminary investigation, samples of Fe-Si and Fe-P alloys were prepared to determine the etching condition electrolytically. Each samples were polarized in 10 N-NaOH aq. solution and taken current density-potential curves by potential-sweep method and current density-time curves at constant potentials. From these results, it is known to be able to detect phosphorus and silicon segregation in ferritic cast iron by etching potentiostatically at +100mV and +600mV vs. Hg-HgO reference electrode respectively.
  Then the authors applied this technique to cast iron samples of different graphite structures and nearly eutectic composition.
  They observed;
  (1) Silicon in grey cast iron is concentrated in the core of eutectic cells. On the other hand, phosphorus is enriched at the cell boundaries.
  (2) It is shown that there is a tendency increasing cell count and reducing its size with increase of phosphorus contents.
  (3) It is able to reveal the cell structre of inoculated cast iron substaintially free from sulfur and phosphorus by etehing silicon segregation at +600mV.
  (4) Especially in inoculated sample, it is observed that some cells are interconnected and seen as only one cell at low magnification.
  (5) There are two types of fine graphitic structures classified with respect to silicon segregation. One is very remarkably uneven and other is rather uniformly distributed.
  (6) In spheroidal graphite cast iron, it is known that graphite nodules are randomly aligned. They are present not only in the dendritic but also in the interdendritic regions.
  From these observations the authors have opinion that eutectic cells in flaky or spheroidal graphite iron can not be really estimated by counting them at low magnification (in the case of flaky graphite iron) nor of graphite nodules, and hence eutectic cell models being proposed are not generally valid.

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  It goes without saying that considerations on the fracture phenomena of the structural components are the most important subjects for rationalization of their designs and prevention from their failures. Therefore many significant contributions have been made to the understanding of them. However, the laws governing fracture can not be extended over all the engineering materials as well as cast irons because of complexity of those meterials in nature and further no method for direct observation on the fracture surfaces microscopically.
  In these respects, this brief survey is made of the fracture phenomena of spheroidal graphite cast irons by the use of Scanning Type Electron Microscope, which can be achieved to focus more deeply than the optical microrcope and also to obtain high magnification and resolution without replica, as an aid in engineering interpretation.
  Graphites and matrixes in the fracture surfaces from tension, compression, torsion, bend, impact, and fatigue were observed at magnifications ranging from ×300 to ×3,000.
  In addition, inclusions which are responsible for initiation or propagation of cracks were partly observed by Electron Probe X-ray Microanalyzer.
  Results were summarized as follows;
  Few differences in appearance of graphites were observed between any fracture surfaces except those of compression and torsion. The shear loads made graphites fail through the spherules.
  The fracture surfaces of tension and bend exhibited similar in matrices, while the other surfaces showed some characteristic differences respectively.
  Cracks were initiated at the graphites and inclusions located at the cell boundaries. Straining speeds were also unavoidable factors for crack formation.

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  This report deals with the squeeze mechanism of the founding sand.
  The transfer of pressure for difftrent founding sands, the pressures, and their effect on the hardness of the mould are described.
  The following points can be concluded :
  (1) The pressure on the loading face, (the face where the pressure is applied,) is proportional to the pressure on the loaded face (the face underneath where the pressure is received). The pressure given to the loaded face is proportional to the sectional area and is inversely proportional to the height.
  (2) Even if the pressure on the loading face is constant, the pressure given to the loaded face varies with the quantity of water present in the clay.
  (3) The strain increases with the increase in the loaded force. The increment of the strain is large at low load and small at high load.
  Furthermore, the increase of strain is small where the quantity of water present is less and large where the quantity of water present is more.
  (4) The hardness of both the loading face and the loaded face increases with the increase in pressure, and is approximately proportional to the pressure.
  (5) The internal pressuse of the compressed sand satisfies the following formula :
        [Written in non-displayable characters.]
  where:
    σz : the pressure of any point, z, along the z axis,
    σ^* : the pressure on the loading face,
    α : a constant determined by the nature of the sand, quantity of water, compressive force, etc.,
    κ : the coefficient of friction between the sand and the wall of the mould,
    l₁l₂ : the length and width of the frame,
    π : the circular constant,
    z : an arbitrary point along the z axis,
    z^* : the height of the loading face.
  This formula is applicable with some errors at low pressures but agrees with experimental data well at high pressures.

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