Investigation upon the casting structure (1st. Report)

Relation betweer the caating structure and the recrystallized structure in 3S alloy

Abstract

This is the report on the study of the relation between the structure of 3S alloy as cast and that after recrystalized and the difference between the grain size in 3S sheet rolled from ingot non-pre-heated and that pre-heated. The findings obtained from the above-mentioned study are as follows:
(1) The hardness of the sheet before and after annealing is, regardless of the change in casting structures, almost unchanged, while in the case that it is pre-heated, the hardness after annealing is always lower.
(2) When preheated, the distribution of compounds were un-homogenized, while the compounds are changed into spheroidal particles. This phenomenon takes place more remarkably and quickly as the grain structure of ingot is finer.
(3) In case of slowly cooled ingot, the recrystalized grains does not change much when it is rolled, regardless of preheating, while in case of rapidly cooled ingot, if it is preheated, the grains becomes finer in outer part where the crystal is columner, and coarser in inner part where the crystal is granular. The pre-heating affects little the part of columnar crystal but much the part of granular crystal.
(4) Grain size of slowly cooled ingot becomes coarser when preheated, while that of rapidly cooled ingot becomes finer.