To improve the durability of a thermocouple for measuring the temperature of molten metal by constituting its outside sleeve in a laminated structure and adding a molten-metal repellent BN to the outermost layer.
The thermocouple has a protective inner tube 2 which is provided with a heat receiving section 4 at its front end and is made of a heat- resistant material, a filler 8 which is packed in the tube 2 and composed of a heat-resistant ceramic, a pair of metallic element wires 6 and 7 of different compositions constituting a temperature measuring section 9 arranged in the filler 8. The thermocouple also has an outer sleeve 1 covering the external surface of the tube 2 except the heat receiving section 4. The sleeve 1 is formed by alternately or randomly laminating first layers 10 composed of a material containing silicon nitride as the main ingredient and second layers 11 composed of a material containing silicon nitride as the main ingredient and 10-40 vol.% molten-metal repellent BN upon another in a concentric or spiral state where the layers 10 and 11 are adhered closely to each other.
SUZUKI TAKAMOTO
KITA HIDENORI
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