Application of tungsten-rhenium thermocouple in cemented carbide process

In the manufacture of tungsten carbide, tungsten-rhenium thermocouples have become the core temperature measurement tools in key links (such as sintering and melting) due to their high temperature resistance, high precision and corrosion resistance. The following are the specific applications and technical highlights:

1. Temperature monitoring in the sintering process

- Application Scenarios:

- The carbide sintering temperature is typically 1400~1600 degree , which needs to be precisely controlled to ensure uniform carbide grain growth and adequate wetting of the binder phase (e.g. cobalt).

- Monitor the temperature distribution in the sintering furnace to avoid coarsening of the grains due to local overheating or under-burning leading to insufficient strength.

- Technical Advantages:

- Wide temperature measurement range: it can cover 1000~2300 degree to meet the needs of ultra-high temperature sintering.

- Fast response: Quickly capture temperature changes and support dynamic adjustment of sintering curves.

- Resistance to reducing atmospheres: Superior stability to platinum rhodium thermocouples in hydrogen or vacuum sintering environments.

2. Temperature control of the melting process

- Application Scenarios:

- Used to monitor the temperature of metal melts (e.g., cobalt-based alloys) in melting furnaces (e.g., intermediate frequency induction furnaces) to ensure composition uniformity.

- Control melt pouring temperature to avoid porosity or crack defects due to temperature deviations.

- Technical Highlights:

- Resistant to metal melt erosion: corundum or silicon carbide protective sleeve is required to prevent tungsten rhenium wire from direct contact with molten metal.

- Long-term stability: Maintains accuracy in high-temperature melts and reduces the frequency of calibration.

3. Key Benefits

- High temperature resistance: The maximum temperature measurement is up to 2300 degree , which far exceeds the temperature requirements of the cemented carbide process.

- High sensitivity: High thermoelectric potential rate (about 10~12μV/ degree ) can detect small temperature changes.

- Cost-effective: Less expensive than platinum rhodium thermocouples and eliminates the need for precious metal compensation leads.

- Anti-interference ability: Stable signal in strong magnetic fields (e.g., induction heating).

4. Installation and maintenance

- Mounting Position:

- Close to the workpiece in the sintering furnace but avoid contact to ensure that the true temperature is measured.

- The melt should be inserted vertically into the furnace to a depth of Greater than or equal to 100 mm to reduce the influence of ambient temperature.

- Protective measures:

- Use a double-layer protective sleeve (e.g. outer corundum + inner silicon carbide) to isolate corrosive atmospheres.

- Regularly inspect the sleeve for wear to prevent breakage that could lead to thermocouple failure.

- Calibration cycle: It is recommended to calibrate every 6 months to ensure accuracy (typically ±0.5%FS).

5. Precautions

- Oxidation susceptibility: It is easy to oxidize in air or oxidizing atmosphere, and needs to be protected by inert gas.

- Mechanical strength: tungsten rhenium wire is brittle and should avoid severe vibration or bending.

- Environmental compatibility: Avoid contact with substances containing sulfur, phosphorus and other elements to prevent chemical corrosion.



- A tungsten carbide tool manufacturer: used type B tungsten-rhenium thermocouple (index number WRe5-26) in a vacuum sintering furnace to control the temperature fluctuation at ±2 degree , increase the density of the product by 3%, and reduce the scrap rate by 1.5%.

- Tungsten carbide powder melting: The melt temperature is monitored in real time by the C-type tungsten-rhenium thermocouple (WRe5-26), which optimizes the pouring process and reduces the problem of product cracking caused by temperature deviation.

Through the rational selection of models, the optimization of installation methods and the combination of automatic temperature control system, tungsten-rhenium thermocouples can significantly improve the stability and yield of cemented carbide production. In practical applications, it is necessary to select the appropriate thermocouple type (such as type C, type B) and the material of the protective sleeve according to the specific process (such as sintering atmosphere, maximum temperature).