Abstract
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.
