| 摘要 |
The present invention can be used to core a small hole that has a diameter of 18 mm or less and that has a favorable finished state. In the expression below, t (mm) is the thickness of a coating agent that is applied to a foam pattern 2, D (mm) is the diameter of a hole part 3, and σc (MPa) is the flexural strength of the dried coating agent at ordinary temperature. For the casting of a cast object that is provided with a hole that has a diameter of 18 mm or less and a length of l (mm), when a solidification end time te (sec) at which a molten metal finishes solidifying at a peripheral part of the hole part 3 is within a time t0 (sec) by which the coating agent finishes pyrolysis, a coating agent that satisfies the following expression is used: σc ≥ {t0/(t0-te)}×(1.5×10-4×l2/t2+160/D2). |
