The characteristics of tungsten rhenium thermocouples are: high melting point of thermoelectric electrode wire (3300 ℃), low vapor pressure, and easy oxidation; Good chemical stability in non oxidizing atmospheres. The electromotive force is large and the sensitivity is high, mainly due to its cheap price.
At present, non-contact methods are commonly used to measure temperatures above 1600 ℃. However, this method has significant errors, and using contact rules can accurately measure the actual temperature. In high-temperature thermocouples, precious metal thermocouples are expensive and can only be used at temperatures below 1800 ℃, while tungsten rhenium thermocouples have a high temperature measurement limit and good stability. Therefore, tungsten rhenium thermocouples are widely used in industries such as metallurgy, building materials, aerospace, aviation, and nuclear energy. China has abundant tungsten resources, and tungsten rhenium thermocouples are cheap and can partially replace precious metal thermocouples (platinum rhodium thermocouples). They are very promising temperature measurement materials in the field of high-temperature testing. Its high usage temperature can reach 2800 ℃, but data is dispersed above 2300 ℃. Therefore, the optimal temperature for use is around 2000 ℃.
Tungsten rhenium thermoelectric dipoles are prone to oxidation and are suitable for use in inert or dry hydrogen gas, or can only be used by isolating them from oxygen with a dense protective tube. Cannot be used in carbon containing atmospheres (such as in atmospheres containing hydrocarbons, where temperatures exceed 1000 ℃ and corrosion occurs). Tungsten or tungsten rhenium is prone to generate stable carbides in a carbon containing atmosphere, which reduces its sensitivity and causes brittle fracture. In the presence of hydrogen gas, it accelerates carbonization.
The oxidation resistance problem of tungsten rhenium thermocouples has always been a topic of concern for scholars at home and abroad, and they are committed to researching and solving it. The assembled high-temperature and high-pressure tungsten rhenium thermocouple has a temperature measurement range of 0-1800 ℃ and is widely used in industries such as metallurgy, coking, chemical kilns, heat treatment, glass, etc. It has the advantages of high accuracy, low price, stable performance, and is not limited by working environment atmosphere. It is an ideal product to replace platinum rhodium thermocouples. The tungsten rhenium thermocouples produced by our company have been widely used in many units, and their performance has reached the level of similar foreign products. Its technical indicators are as follows:
1. Graduation numbers: W-Re3/25, W-Re5/26
2. Temperature measurement range: 0-1800 ℃
3. Temperature measurement accuracy:<± 1% t< ± 0.5% t
4. Time constant: ≥ 180 s
5. Insulation resistance:>5M Ω
6. Specification and size: 30050075010001100 (mm)
The tungsten rhenium rapid temperature measurement thermocouple is designed and manufactured specifically for measuring the temperature of molten steel, molten iron, and other metal melts. It has the advantages of small volume, fast thermal response speed, high accuracy, and low price. Its technical indicators are as follows:
1. * * * High temperature measurement: 1800 ℃
2. Temperature measurement accuracy: ≤ 0.5%
3. Insulation resistance: ≥ 30 M Ω
4. Completion rate: ≥ 98%
5. Reaction time:<5 s
At present, the tungsten rhenium thermocouples produced by our company are divided into three categories:
One type is the use of fine ceramic protective tubes. The specifications of ceramic tubes include: diameter of 8, Ф10，Ф12，Ф14，Ф16， The length is 300-11100mm, and this type of thermocouple is not limited by the working environment atmosphere and can be used for a long time in any atmosphere. The temperature measurement range is 0-1800 ℃
Another type is pure molybdenum protective tubes Molybdenum tubes and tungsten tubes have specifications of: diameter of ¥ 6, ¥ 8, ¥ 10mm, length of 500-700mm. These thermocouples can only work for a long time in vacuum, reduction, or inert gas protection environments. Molybdenum tubes are suitable for long-term use at temperatures below 1800 ℃, and can reach temperatures up to 2000 ℃ for short-term use;
Another type is tungsten protective tubes. As for tungsten tubes, they can work for a long time at 2100 ℃, but they are difficult to process, making them very expensive.
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