| 摘要 |
PROBLEM TO BE SOLVED: To provide refractory particles suitable as casting sand, which are composed of a spherical mullite sintered compact or a spherical mullite-corundum sintered compact in which the high melting point properties of mullite are not impaired, and having no burn-on defect even in the environments of the contact with high temperature molten metal and high pressure, having excellent heat resisting properties, and further having low thermal expansion. SOLUTION: The spherical particles have a particle diameter of 0.01 to 2.00 mm, which are composed of a mullite or mullite-corundum dense crystalline sintered compact including mullite as the main mineral and having a chemical composition of, by weight, 70.1 to 90.0% Al<SB>2</SB>O<SB>3</SB>and 10.0 to 29.9% SiO<SB>2</SB>, and in which the total content of the Al<SB>2</SB>O<SB>3</SB>and SiO<SB>2</SB>is≥97%. The spherical particles also have an apparent porosity of 1 to <5%. COPYRIGHT: (C)2011,JPO&INPIT |
