High temperature furnace temperature uniformity test method and implementation points

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High temperature furnace temperature uniformity test method and implementation points

High temperature furnace temperature uniformity test method and implementation points

1. Test purpose and timing

The temperature uniformity test of high temperature furnace is to determine the effective working area of the furnace (charging space that meets the process temperature uniformity requirements) to ensure the quality consistency of workpieces after heat treatment2. The test timing is divided into two categories:

Initial test: Before the new furnace is put into production, after overhaul or process adjustment, the full working temperature range (lowest to highest temperature) needs to be verified.

Periodic test: Regularly carried out according to the furnace level, usually selecting common temperature points to ensure long-term stable operation of the equipment.

2. Main test methods and steps

2.1 Thermocouple method (core standard method)

Thermocouple arrangement

Arrange multiple thermocouples in the center, four corners, different heights and close to/away from the heating element of the furnace to ensure coverage of key areas.

Use a clamp or adhesive to fix the thermocouple to ensure close contact with the surface to be measured and reduce measurement errors.

Temperature measurement and data acquisition

Raise the furnace temperature to the set temperature and run it stably, and record the temperature of each point synchronously through a multi-channel thermometer or data acquisition system.

The test conditions need to simulate the actual production status, such as heating rate, atmosphere parameters (atmosphere furnace), circulation fan operation, etc.

Data analysis

Calculate the maximum temperature difference (difference between the highest point and the lowest point) and deviation (deviation of the temperature at each point from the set temperature).

Determine whether it is qualified according to the process standard. For example, high-precision heat treatment usually requires a temperature difference of ≤±5℃.

2.2 Temperature sensor array method

Array installation: Arrange sensor arrays evenly distributed in the furnace or in key areas, supporting wired/wireless data transmission.

Real-time monitoring: Generate temperature distribution diagrams through software, intuitively display the temperature field distribution in the furnace, and quickly locate hot spots or cold spots.

Advantages: Suitable for large furnaces or complex structure furnaces, with higher data resolution than traditional thermocouple methods.

2.3 Thermal imager assisted detection

External scanning: Scan the outside of the furnace during operation, and indirectly analyze the temperature distribution in the furnace through infrared radiation.

Image analysis: Judge the temperature uniformity based on the color difference of the thermal image (bright high temperature, dark low temperature), and assist in identifying heat leakage in the furnace wall or abnormal heating elements.

Limitations: It only reflects the surface temperature of the furnace body, and other methods need to be combined to verify the actual situation in the furnace.

2.4 Actual workpiece test method

Workpiece selection: Use samples with similar materials, shapes and sizes to the production workpieces to simulate the actual loading state.

Monitoring point layout: Paste thermocouples or temperature labels at key positions on the surface of the workpiece to record the temperature changes during the entire heat treatment process.

Result evaluation: Through the temperature difference of different parts of the workpiece, the adaptability of the furnace to actual production is directly verified.

III. Test system composition and implementation conditions

3.1 Core equipment

Temperature sensor: precious metal thermocouple (S type, 0-1600℃) or cheap metal thermocouple, accuracy ±0.5℃

Data acquisition system: multi-channel synchronous acquisition, sampling frequency ≥1 times/second

Temperature measuring frame high temperature resistant material: (such as ceramic) to avoid affecting the airflow in the furnace

3.2 Test conditions

No-load/loaded test: No-load test is the default, and loaded test is performed when necessary (load capacity ≥ 50% of the rated furnace load).

Environmental control: Keep the furnace door closed and the atmosphere in the furnace stable (such as vacuum degree, protective gas flow rate).

IV. Result evaluation criteria

Temperature uniformity index: The maximum deviation of the temperature of each test point relative to the set temperature is the core index, and the specific threshold must meet the process standard (such as aerospace standard AMS2750G).

Effective working area division: Determine the qualified loading area based on the test data. Exceeding the range may cause fluctuations in the quality of the workpiece.

V. Precautions

Thermocouples and data acquisition systems need to be calibrated before testing to ensure measurement accuracy.

Take the average value of multiple tests to reduce the impact of random errors.

Record test environment parameters (such as room temperature and humidity) to facilitate result traceability and abnormal analysis.

The above method can systematically evaluate the temperature uniformity of the high-temperature furnace and provide data support for process optimization and quality control.

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