On casting, the molten metal flows into the mold cavity through the gate and runner, therefore it is necessary to know the characteristics of metal in fluid state. Metal flow at gate and runner may be similar to the flow of water in a pipe, so we worked out the coeff. of discharge at the gate and runner, and the pipe friction between metal and mold was also studied, using of water, Hg, molten Al and molten cast iron.
  The author has taken the following results. through the experiments.
  ① Coeff. of discharge of molten metal is nearly equal to that of water, but comparatively higher in Reynolds number. Metal can not flow out through the nozzle by its surface tention.
  ② Casting temperature of metal does not give serious effect.
  ③ Edge of an orifice gives bad effect, so a slight roundness is necessary.

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  Metal flow in a casting of piston was investigated by the lamp method same as before. With different design of gates and risers, the flow was traced and has shown in the flow diagrams respectively.
  In general, the lower gate makes the flow less disturbance, and the position of riser has some effects on metal flow.

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  To accomplish the greatest possible permeability, a few amount of frothing agent such as so-called soap-less-soap is being added to plaster tempering water and a mechanical device to enclose air bubbles into plaster slurries was also adopted. In preparing the suitable plaster slurries for making foamed plaster molds, proper amount of tempering water must be added to gypsum plaster. The amount of water which is to be added is considered preferable to define from 130 to 170% against plaster.
  To expel free water in plaster molds, about three hours of drying at the temperature of 105-110°C is sufficient, but in the actual performance in foundries, chemically combined water in plaster molds must be partly driven off at much higher temperature. Practical conditions such as water percent, amount of hardening acceralating agent and frothing agent, mixing time, mixing velocity of the whip and the pouring time should be strictly regulated to make desirable molds having good permeability and strength.
  Further investigations must be given to use this kind of plaster molds practically.

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  According to the previous reports, it was observed that the base sand Ⅲ having an optimum grain size distribution (4-screen sand) was superior in mouldability.
    This may not be said similarly, however, in the case of a finer grain sand.
    This paper is prepared especially to discuss this problem.
    The result of this experiment and discussion is summarized as follows :
  1) In a comparatively coarse sand having optimum grain size distribution, i.e., 4-screen sand (base sand Ⅲ), the mouldability was experimentally and practically good.
  2) Contrary to this in a comparatively fine sand having the type of 4-screen sand, the mouldability was bad.
  3) It seems that the former is due to the sub-angular shape of coarse sand and the latter is due to the sub-crystalline shape of fine sand. Consequently it will be reasonable to discuss the mouldability not only the optimum grain shape distribution but also the grain shape.
    Therefore, it is required to select the optimum base sand from this view point.

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    With the similar method mentioned in Rept. 1, the segregates of Mg, Si and Mn in spheroidal graphite cast iron of wedge-shaped section were investigated.
    The results were summarized as follows :
  (1) The local segregates were at random in the upper part of the specimen where a great number of shrinkage cavities existed.
  (2) The pecuIier local segregate existed in the vicinity of shrinkage cavity or in the part of inclusion.
  (3) From the result of the segregates detemination on the traverse across of the wedge-shaped section, “V” or “W” type segregation curve as mentioned in Rept. 1, were also obtained. From these characteristic curves, the mechanism of segregation was considered as follows :
  (a) The “V” type segregation is the inverse segregation caused by super-cooled solidification.
  (b) As the thickness of the wedge-shaped specimen became wider, normal segregation occured in the inner part of the super-cooled domain. Thus, the inverse segregation at the outer part of castings turned into normal segregation at the inner part. Hence the segregation curve was illustrated as “W” type.

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