The previous report concluded the shrinkage cavity became larger with the increase of SiO₂ as an inclusion when cast iron was oxidized at the lower temperature after melting-down. This report is also aimed to make clear the relation between the oxidizing melting and the casting defects in which the shrinkage cavity is a chief object. In the premise that SiO₂ related to the shrinkage cavity, the experiments were carried out, contrasting the defects with the analytical value of oxides by a chroline method under the following conditions :
1) when oxidized at a high temperature such as 1470°C at which SiO₂ is reduced by C, 2) when oxidized before melting-down, and 3) when raw material of high C and high Si is oxidized.
  The results obtained are the followings.
 1) If metal is oxidized at the high temperature, the defects are never occured.
 2) If metal is oxidized before melting-down, the oxide film gives an ill effect.
 3) The shape of defects by the super oxidizing melting becomes a shrinkage cavity, and at last an abnormal outer shrinkage.
 4) In a slight oxidation a defect which is chiefly a blow hole is apt to occur. This tendency is more remarkable in cast iron of high C and high Si.
 5) Sound castings are obtained at the medium oxidizing melting.
  Moreover, it was clarified that the defects by the super oxidizing melting related to the value of SiO₂ as an inclusion. The proof for this reason is now under experiment.

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  Recently many publications have described that the basic lined cupola has been operated commercially in many countries, In Japan, however, high price and poor production of magnesite refractories, in short, the difficulty of getting this kind of refractories has made us not to operate basic process in cupola melting.
  With the view of investigating if there are other better or inexpensive basic refractories for cupola lining, various lining materials-marble brick, alumina brick and dead-burned dolomite were utilized to linings of midget cupola in our foundries. Results obtained from these cupola operations are as follows :
  1) Increased carbon pick-up was obtained in basic operation using dead-burned dolomite lining.
  2) Silicon loss showed its maximum value in basic operation whilst its minimum in acid operation.
  3) Remarkable difference of manganese loss was not observed among basic, neutral and acid operation in our studies.
  4) No change of phosphorus contents was observed in most operation, whilst only 0.007 pct of phosphorus was decreaaed in alumina brick lining.
  5) Sulphur increase was not notable in basic operation.
  6) Test specimens cast from basic melts showed better mechanical properties.
  7) Maximum erosion of refractories was obtained in dead-burned dolomite lining, and minimum value in alumina brick.
  8) Numerous kish graphite were formed in the case of alumina brick and dolomite linings. Larger graphite flakes and cleaner matrix having no remarkable impurities were obtained in dead-burned dolomite operation.

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  This research is concerning cast iron strengthened by the core grid of mild steel. The volume ratio of the core grid to the casting is less than 11 per cent to solder the core grid to the casting completely. Cast iron of the tensile strength 15∼19 kg/mm² increased 20∼30 per cent in the strength by the steel grid of the volume ratio 4%. (M. I.)

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  By the research of green sand and its high temperature properties, we confirmed that good deformation of green sand and little high temperature expansion prevents high temperature cracking of the green sand mould.
  These characteristics are supposed to prevent scabbing, buckling and rat tail. To confirm these results, wooden flour is added in the green sand mould, and following are gained by the addition of wooden flour;
  1. Permeability decreases,
  2. Deformation increases,
  3. Porosity increases,
  4. High temperature expansion decreases and contraction increases,
  5. High temperature crack decreases.
  These results are applied in the foundry shop practice and proved successful.

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  The studies made by the authors are concerning the compression strength measurement of green sand molds.
  The strength of green sand molds shall be influenced, in general, by the surface tension and the viscosity of the binder mixed into sands when the same grain sized sands are used.
  Consequently it can be thought that the strength of green sand molds shall be changed corresponding to the variation of the compression velocity. At the time of measuring the compression strength of green and molds, the authors conducted the measurement with separating the two factors such as the surface tension and the viscosity of the binders while changing the compression velocity.
  It has ascertained through the experiment made by the authors that it is the surface tension of binder that effects the influence on the strength of green sand molds and the sorts of binders have nothing o do with the strength when the compression velocity is less than 0.04mm/sec. and the grain size of the silica sands is approximately 100 mesh.

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