| 摘要 |
PROBLEM TO BE SOLVED: To prevent the crack of an inside part and the leakage of a magnetic material by forming a vapor diffusion control means of plural cylindrical layers laminated outward from the inside and specifying the porosity and coefft. of thermal expansion of the inside wall parts thereof to specific values. SOLUTION: The ferromagnetic material 10 for evaporation is packed into a cup-shaped refractory crucible 11a consisting of material MgO. A high-frequency induction heating coil 12 internally has a cooling water circulating pipe and is connected to the high-frequency power source on the outside of a vacuum chamber. This vapor diffusion control means consists of the plural cylindrical layers laminated outward from the inside and the inside wall parts are formed of the material having the porosity of 10 to 25% and the coefft. of thermal expansion of 0.8×10<-5> / deg.K to 1.4×10<-5> / deg.K. The deterioration in the innermost layer side by thermal impact is, therefore, eliminated and the penetration of the molten metal by crack is prevented. Further, the vapor flow diffusion control means is provided with an inside wall test piece 15d in the state of that this test piece is continuous with the crucible 11a in order to investigate the crack and the penetration. An outer peripheral part 15e of a cooling structural body is arranged on the rear surface thereof.
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