Expandable core for use in casting

摘要

A salt core ( 2 ) is formed by casting a mixed material of a salt material and a ceramic material. Any one of a chloride, bromide, carbonate, and sulfate of potassium or sodium is used as the salt material. As the ceramic material, granular one having a density falling within a range of 2.2 g/cm³ (exclusive) to 4 g/cm³ (inclusive) is used.