| 摘要 |
PURPOSE:To extend the life of a protective pipe and heating means by providing the protective pipe which projects into a crucible and is built in with a heater and supplying a pressure fluid into the protective pipe as well thereby making pressurization. CONSTITUTION:The crucible 4 is housed and fitted into a heat insulated holding furnace 1 and the crucible 4 is communicated with the cavity 20 of a metallic mold 19 via a stalk 12. The protective pipe 21 which projects horizontally into the crucible 4 and consists of a refractory material is disposed. A heating coil 24 is provided to the pipe 21 to heat the molten metal A in the crucible 4. The pressurized air is supplied into the crucible 4 and at the same time the pressurized air is supplied into the protective cylinder 21 as well through a communicating passage 28 when the mold 19 is set. The difference between the inside and outside pressures of the cylinder 21 is thereby eliminated and the penetration of the metallic Na into the pipe 21 is suppressed. The cracking of the protective pipe 21 is prevented by the above-mentioned method and therefore, the life of the pipe 21 and the heating means therein are extended.
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