It is so-called internal shrinkage cavities to cause very often hydraulic defects of a cylinder block casting for Nissan Motor after surrender. The author explained internal shrinkage cavities, investigated the chemical composition of materials, the casting temperature and the cupola operation, and obtained their most suitable values ; that is, the chemical composition is C 3.15∼3.25%, Si 2.00∼2.20%, P 0.10∼0.20, and a ordinary content of Mn and S. The casting temperature as high as possible is desireable (1450∼1470°C). The Operation of a 3t cupola is best at 50 m³⁄min of a blast volume and at 400∼500^mm water of a blast pressure. (M. I.)

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  The relations between gases generated in solidification of cast iron and its nonmetallic inclusions were investigated. The results obtained follow :
  1) The amount of gases generated during solidification of cast iron melted by the cupola was generally larger than that in the same operation by the electric furnace. In the Case of cupola the amount became greater as the melting temperature rose ; even in this case, however, it decreased when the molten metal was extremely oxidized. This amount is more influenced by the melting operation than by the melting temperature.
  2) The gases produced during solidification increased with the slower cooling rate near the solidification point.
  3) The composition of the gases was gradually enriched by CO and H₂ in the elapsed time of the gas emisson.
  4) The residual oxides as non-metallic inclusions in the metal melted by the electric furnace were more than those in the cupola operation.
    But even in the cupola the quantity of oxides extremely increased when the melting operation was inadequate.
  5) In general, when a greater amount of the oxides remained, the gas emission was smaller.
  6) In the product in which the shrinkage porosity ("Kusare" as it is called in Japanese shop jargon) was detected, the oxides reached a large amount but the gas emission was smaller. Development of pin-holes accompanied greater amuont of gas and relatively fast cooling rate in time of solidification.
  7) The cooling rate in solidification was minimum when the pouring temperature was proper.
  8) In order to obtain sound castings, the absorption of O₂ and H₂ in the melting period should be avoided and sufficient reactions should be promotd above 1500°C where the reducing reaction by C occurs before gases are released by killing and the pouring should be made at the temperature where the cooling rate in solidification becomes lowest.
  9) The relations between the surface figure and the properties of molten metal are very much complicated, requiring elaborate studies in the future.

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  Frommer's theory of die-casting process, especially of a gate is based on two-dimensional aspect, but the gate should be three-dimensionally thought. The authors investigated the gate size of a thin wall die-casting and Frommer's theory experimentally. The results obtained are as follow :
  (1) The most filling ratio (Apparent S. W. ⁄ Specific Weight × 100%) was obtained, when the gate area was 20∼60^mm2, or Gate Area ⁄ Cavity Section Area (177^mm2) = 1/9∼1/3. Moreover, the gate-width and-depth are limitted by (Ⅰ) and (Ⅱ) for a better metal flow and a surface of die-castings. (Ⅰ) The gate width is 40∼50^mm or Gate width ⁄ Cavity width = 4/6∼5/6. The wider the gate, the better the die-casting becomes. (Ⅱ）The gate depth is 0.5∼1.0^mm or Gate Depth ⁄ Cavity Thickness = 1/3∼1/6.
  (2) Frommer's theory of the gate size cannot be applied to a thin wall die-casting.
  (3) If the metal flow is not tarbulated, the better die-casting will be produced. Therefore, a further work on the metal flow is required.

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