| 摘要 |
An induction furnace capable of operation at temperatures of over 3100° C. has a cooling assembly ( 60 ), which is selectively mounted to an upper end of the furnace wall ( 76 ). The cooling assembly includes a dome ( 62 ), which is actively cooled by cooling water coils ( 68 ). During the cool-down portion of a furnace run, cooling initially proceeds naturally, by conduction of heat away from the hot zone through a furnace insulation layer ( 58 ). Once the temperature within the furnace hot zone ( 20 ) reaches about 1500° C., a lifting mechanism ( 80 ), mounted to the dome, raises a cap ( 16 ) of the furnace slightly, allowing hot gases from the hot zone to mix with cooler gas in the dome. This speeds up cooling of the hot zone, reducing cool-down times significantly, without the need for encumbering the furnace itself with valves or other complex cooling mechanisms which have to be replaced periodically. The life of a graphite furnace susceptor ( 10 ) at the high operating temperature is increased by surrounding the susceptor with a barrier layer ( 40 ) of flexible graphite, which inhibits evaporation of the graphite. Additionally, witness disks ( 154 ), placed within the susceptor, provide an accurate temperature profile of the hot zone.
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