Casting surface is not only influenced by the external facters, but also by the crystal structure of casting structure.
  In this report, the relation between crystal structure and cast metal was researched.
 1) Casting surface is covered with its dendritic structure, granular grain structure or its thick oxide film.
 2) The casting surface of dendritic structure always appears in the case of using the metal having the characteristics of a small ratio of supper cooling or in the case of the procedure making a ratio of supper cooling small.
  The casting surface of granular grain appears in the case of using the metal having the characteristics of a large ratio of supper cooling or in the case of procedure making a ratio of supper cooling large.
 3) The small unevennesses being appeared in the profile-curves which were measured by tracer method at the higher magnification than usual, indicate the surface roughness of the crystal structure of casting surface.
 4) Each surface roughness of cast metal due to crystal structure is decided according to the casting condition. And so it does not follow that the surface roughness of casting infinitely decrease according to the following formulla
    Sc = cs + b₁  or   Sc = cs
    (Sc = surface roughness of casting)
    (s = grain size of molding sand)
    (c, b₁ = coefficient)
 5) The crystal structure of casting surface is generally roughned in the case of a small ratio of supper cooling and a poor growth of crystal, but in the case of a large ratio of supper cooling and a rich growth of crystal, its surface is reversely fine.
 6) The roughness of granular grain structure is remarkablely finer than that of dendritic structure.
 7) The crystal structure of cast metal does not appear in pressure cast and the casting surface is mainly decided according to the mold surface.

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  Various mixture of the charge materials in the cupola melting were perfermed in our foundries. Consequently, it has been clarified that by applying the method as described later to the cupola operation the successful production of iron castings having the required composition can be obtained easily compared with the usual operation by empirical mixing.
  (1) In the first instance careful consideration was payed in the management of cupola charge materials. Namely, iron and steel scraps were divited into several classes by fracturing inspection, and the charge materials, pig-iron and returned scrap etc. were analysed chemically.
  (2) The actual calculation of the proportions of the charge was carried out easily by using a triangle diagram with three component as pig-iron, iron scrap and returned scrap of known analysis.
  (3) After mixing calculation was performed for getting the required carbon content, the additional controls of silicon and manganese contents were obtained respectively by adding ferro-alloys. (N. T.)

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  The method of analysis.
  (1) The chlorine method and the hot nitric acid method are examined, each value of which can be reappeared.
  (2) The value of oxides by the chlorine method is higher and also more reliable than the one by the nitric acid method.
  (3) The chlorine method can not be adopted to the gray iron, but to the white iron.
  The action of oxides during the melting time.
  (1) When the high-temperature melting, the molten metal decreases oxides and is deoxidized better.
  (2) The casting which has large shrinkage cavity contains much oxides composed of silica chiefly. There is no shinkage cavity below 0. 03% SiO₂, but the comparatively larger one over 0. 05% SiO₂.

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