ぬか型の研究（第3報）

Abstract

As has already reported, the difference of the cooling velocity between the upper and lower part of a slab or billet will cause many defects, such as crack or streak upon cold working. Gases evolved on combustion of rice-bran during the pouring of melt attack the soldified skin, resulting in defective areas. Incorrectly by added moisture to a mould may be more deterimental than other faults, because if the added moisture is too low, a carbonization of rice-bran is promoted, particularly if a mould is subjected to high casting temperature. A slab or billet formed under such a condition has an undesirable property for cold working. To avoid this disadvantage, a close attention to the procedure of casting and moulding is required. The results obtained are as follows: (1) An amount of new rice-bran added to a mould has a remarkable influence upon solidification. (2) With high temperature casting, the volume of gases evolved during the pouring of melt increased. (3)A boundary between the pillar and the granular crystals appearing in a slab or billet is beyond control by a change of the thickness of rice-bran.