To enable protecting of a crucible by providing a detector which detects a sound associated with the boiling of cooling water passed through a water passing hole to detect abnormality such as boiling in the cooling water of the crucible whenever it occurs.
An eddy current which is generated in a segment 2 generates Joule's heat for heating the segment 2 itself and cooling water is passed through the segment 2 to cool. The segment 2 is provided with a protruded part so as to minimize the inner diameter thereof at an outflow port 1a to form the outflow port 1a of the crucible 1. The eddy current concentrates near the outflow port 1a to apply a large floating force to molten metal 5 so that the molten metal 5 is kept from dropping at the outflow port 1a. When the eddy current generated in the segment 2 causes a partial overheating due to duckweeds, the accumulation of scale and the like to boil the cooling water, a sound detector 9 detects a sound accompanied by the boiling to be outputted to an alarm 10. The alarm 10 emits an alarm when detecting an abnormal sound accompanying the boiling from the detected sound.
TAKE TATSUO
FUJITA MITSURU
KAINUMA KENGO
SAKUMA MASAKI
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