Vacuum-packaged ceramic-armored high temperature thermocouple and manufacturing method thereof

Abstract

The invention discloses a vacuum-packaged ceramic-armored high temperature thermocouple and a manufacturing method thereof. The thermocouple is composed of a conjunction box, a cover casing, terminals, a protection sleeve tube, a sealing strip, an insulation layer, a lead, a thermocouple wire and insulators. The protection sleeve tube is made of alumina based high temperature ceramic, the ceramic body is internally provided with a carbon fiber basket, and one surface, facing the internal of the protection sleeve tube, of the carbon fiber basket extends out of the insulation layer on the inner surface of the protection sleeve tube. The thermocouple is also provided with heat conducting block which is made of a silicon carbide based ceramic material, the working end of the heat conducting block is connected with the extending end of the carbon fiber basket, and the center of the opening end is connected with the lead. The sealing strip is made of a high temperature adhesive HN-767A. An enclosed space formed by the protection sleeve tube, the high temperature adhesive and the conjunction box is a vacuum environment of 1 Pa-10 Pa. The thermocouple wire is a nickel-chromium-silicon-nickel-silicon thermocouple wire. The thermocouple can replace the expensive platinum rhodium thermocouple, and is good in economy, high in reliability and long in service life.

Description

technical field [0001] The invention relates to the field of temperature sensors, in particular to a vacuum-encapsulated ceramic armored high-temperature thermocouple and a manufacturing method thereof. Background technique [0002] When used for heat treatment of heat-resistant tool steel such as heat-resistant steel and high-speed steel (the treatment temperature is generally between 1100 ° C and 1350 ° C), currently only platinum-rhodium thermocouples (B couple, S couple or R couple) can be used as heat treatment. Using a thermocouple, according to the requirements of the US military standard AMS2750E, a total of three thermocouples are required for high-temperature heat treatment as normal couples. As we all know, platinum-rhodium thermocouples are expensive (the wholesale price of armored platinum-rhodium couples is as low as 1,500 yuan per piece, Also only be containing rhodium 10% S even), therefore further increased economic cost. It should be pointed out that, in f...

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Problems solved by technology

[0002] When used for heat treatment of heat-resistant tool steel such as heat-resistant steel and high-speed steel (the treatment temperature is generally between 1100 ° C and 1350 ° C), currently only platinum-rhodium thermocouples (B couple, S couple or R couple) can be used as heat treatment. Using a thermocouple, according to the requirements of the US military standard AMS2750E, a total of three thermocouples are required for high-temperature heat treatment as normal couples. As we all know, platinum-rhodium thermocouples are expensive (the wholesale price of armored platinum-rhodium couples is as low as 1,500 yuan per piece, It is only S even containing 10% rhodium), so it further increases the economic cost

It should be pointed out that, in fact, the domestic platinum-rhodium thermocouple can only reach 1200°C in general, and its service life and performance will be greatly reduced if it is used for a long time at overtemperature; while the nickel-chromium-silicon- Nickel silicon, although cheap, durable, high reliability, high theoretical use temperature, but its easy oxidation failure characteristics at high temperature make it can not be used in conventional high temperature heat treatment, generally only used for temperature measurement below 1100 ℃

[0003] Among the relevant patents that have been applied in China, there is no patent information on the use of nickel-chromium-silicon-nickel-silicon wires for high-temperature measurement. Among similar patent documents, the patent "A High-temperature Thermocouple" (application number: 201610136518.7, publication date: 2016-07-20), disclosed a high-temperature thermocouple structure that is also a ceramic protective sleeve, but there are two problems: ① platinum-rhodium thermocouple is still used, and the economy is not good; ② the outer protective tube adopts Silicon carbide ceramics, although the thermal conductivity of silicon carbide ceramics is very good, only its high brittleness, difficulty in molding and large porosity make it easy to be damaged when used as a protective sleeve, and its reliability is poor. At the same time, it is easy for tiny particles to invade and damage its internal parts. Platinum-rhodium precious metal construction for short service life

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