It is very important in determining the capacity of the vacuum pump used for the vacuum sealed molding process that the air suction volume of mold by the process is determined. In the present work, the factors which affect the volume of air suction were examined.
  Air suction volume increased with the area of film melting and was especially marked in cases of rough sand and low pressure, but it decreased by coating the mold. It was mostly affected by sand but suction pressure also affected it greatly. If the mold was heated by radiation and spatter of molten metal and the mold covering film melted out widely before the mold was filled with metal, the volume of air suction increased remarkably.

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  In the earlier work¹⁾ on the fatigue strength of spheroidal graphite cast iron, the author has shown that the presence of wormlike graphite and inclusions may lower the fatigue strength of the cast iron. To confirm the influence of these two microstructural components, fatigue tests were carried out on the test specimens which contained different amounts of wormlike graphite and nonmetallic inclussions.
  The fatigue limit decreases in proportion to the amount of wormlike graphite. Inclusions remarkably lower the fatigue limit, especially at high matrix hardness. When the inclusions and wormlike graphite are present at the same time, the fatigue limit is decreased because of the added effect.

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  This study is concerned mainly with the relations between the moisture content at the plastic limit (PLM) of bentonite and the maximum green tensile strength (MGT) of molding sands for high pressure molding. Eleven kinds of domestic and foreign bentonite were sampled in the state they arrived and tested without drying.
  It was found that the MGT of molding sands obtained by high pressure molding was approximately obtained at the moisture content near the plastic limit of bentonite. Furthermore, PLM value rose as the sum of the area of endothermic peaks in D. T. A. of bentonite increased and as the ignition losses of bentonites increased. The PLM of Na-type bentonites was high when the molar ratio (SiO₂/Al₂O₃) was low. The PLM of bentonites with high molar ratio was also high when the ignition loss of bentonites was high.

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  The crystallization and growth of eutectic cells during solidification were taken note of and investigated to clarify the mechanism of emergence of internal shrinkage in cast iron.
  In inoculated and phosphoric cast irons, the amount of internal shrinkage increased by increasing the number of eutectic cells without regard to chemical components and pouring temperature. In non-inoculated cast irons, the emergence of internal shrinkage was not recognized because the number of eutectic cells were few. The cause of the emergence of internal shrinkage was considered to be in the fact that crystallizing and growing eutectic cells which surrounded the residual liquid metal during solidification prevented excess liquid metal to be supplied enough to fill up the cavity made by liquid metal shrinkage. The reason why the number of eutectic cells was maximum at the carbon equivalent of approximately 3.9 in non-inoculated cast iron and at phosphorous content of approximately 0.5% in phosphoric cast iron could not be clarified in the present work.

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  The distribution of Cr, Mn, Mo and V in hypoeutectic white cast iron was investigated with an electron probe microanalyser. The specimens were made from castings (30mmφ×70mm) solidified unidirectionally in exothermic molds on a water-cooled copper chill plate. The carbon content of the specimens varied from 1.8% to 3.8% and the content of each alloying element was about 1%.
  It was found that the concentration of each alloying element in dendrites took a minimum value at the core and went up gradually towards the outside, and that it was much higher in the eutectic cells. Microsegregation was more remarkable when carbon content was low. The effective distribution coefficients (K_e) of Cr, Mn, Mo and V against the primary austenite were an less than unity, and decreased proportionally with increase in carbon content. The K_e value became larger in the order of Mo, V, Cr, Mn. The concentration of Mo and V in primary austenite at larger solid fractions were remarkably lower than the value calculated from the nonequillibrium freezing equation⁵⁾. The main reasons could be the variation of K_e during solidification and the precipitation of their carbides.

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  Effect of pouring temperature on the solidification time of sand castings was studied theoretically. The former theory by R. W. Ruddle predicted that the dependence of solidification time on pouring temperature was related solely to the properties of the cast metal. By pointing out the negligence in that theory of sensible heat to be extracted from the casting before completion of solidification, a correction factor β was introduced in the present study.
  By numerical calculation, as well as by examination of the experimental data in past publications, it was found that β was nearly always less than unity, meaning that the ffect of pouring temperature was less pronounced than predicted by the former theory. The factor β was particularly small when the heat diffusivity of the cast metal was low, or when the heat diffusivity of the mold was high, or when the shape of the casting was chunky rather than flat. As an exceptional case, the effect of pouring temperature was more pronounced than predicted by the former theory when a core was used in the mold. With a casting of the shape of a hollow cylinder the most marked effect of the core was observed at the internal radius to external radius ratio of 0.35.
  Based on these results, effect of pouring temperature on the directional solidification of casting was discussed qualitatively.

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