THERMOCOUPLE FOR MOLTEN METAL

摘要

PROBLEM TO BE SOLVED: To provide a thermocouple for molten metal the response of which is improved by improving the durability of the thermocouple by making its protective tube of a graded material and the thermal conductivity of the thermocouple in a temperature measuring area. SOLUTION: A thermocouple for molten metal is manufactured by enclosing a pair of alloy element wires 5 and 6 having different compositions in a protective tube 1, one end of which is formed in an opened end 3 sealed with a sealing member 7 and the other end of which is formed in a closed end 2, in such a state that the ends of the wires 5 and 6 are coupled with each other and filling up the tube 1 with a filling member 4 composed of a porous heat- resistance ceramic. The protective tube 1 is made of such a graded material that the outside 1A is composed of an Mo-rich material and the outside 18 is composed an alumina-rich material and the Mo and alumina compositions are changed in such a way that they mutually interpolate each other toward the inside 1B from the outside 1A.