Apparatus and method for measuring temperature of molten metal

An apparatus for measuring a temperature of a molten metal by disposing a nozzle penetrating through a wall of a vessel accommodating a molten metal, guiding out thermal irradiation light of the molten metal facing a distal end of said nozzle through an image fiber (image transfer fiber) and measuring the temperature of the molten metal from said thermal radiation light so guided out, wherein;

• said nozzle has a double pipe structure, said thermal radiation light of the molten metal is observed while a purge gas is passed through an inner pipe and a protective cooling gas for protecting melting loss of said nozzle is passed through an outer pipe;
• a construction of a fitting portion between said nozzle and said image fiber comprises four connectable portions of a nozzle portion, a purge/cooling gas introduction portion, an image fiber fitting portion with window glass and an image fiber protection tube;
• at least one joint portion is disposed on said purge/cooling gas introduction portion so that centering of an optical axis can be made for connecting said thermal radiation light of the molten metal to said image fiber;
• an imaging device such as a CCD camera for measuring the two-dimensional distribution of thermal radiation luminance is connected to a rear end of said image fiber;
• and
• said imaging device is accommodated in a sealed box having a cooling structure and is disposed in the proximity of an outer wall of the vessel for accommodating the molten metal.