Why Does the Alumina Furnace Tube (Ceramic Tube) Easy to Break?

The alumina content of the ceramic tube is more than 99.6%, the bulk density (g/cm2) ≥ 3.80, and continuous working temperature is 1600°C. The alumina tube features high-purity and high-temperature high-quality characteristics, but most corundum materials have poor thermal shock resistance so need to be cautious and careful during operation.

The main reasons for easy to break are as follows:

  • Large temperature difference. The temperature difference is the direct reason of cracking. Because of its own characteristics of the tube furnace: the middle area is heating zone, and the two sides are non-heating zones. The temperature difference between the heating zone and the non-heating zone is at least above 1000°C.
  • Sample handling at high temperature. Sample loading and unloading at high temperatures may cause the furnace tube to break.
  • The heating material contains too much moisture.
  • The cooling rate is not set. Based on our many experimental data, it is shown that when the furnace was performed with natural cooling after heat treatment finished, it takes only 10-15 minutes (20℃~30℃/min) for temperature decreased from 1300℃ to 1000℃, while the furnace tube is suitable for heating rate 5~10°C/min.
  • The gas purging rate excessed too much.
  • No welding support frames on both sides of the furnace tube, and the tube deforms and breaks due to gravity under high temperature.

What are the matters needing attention in the use of alumina tube?

  • For the first time using, it needs to be preheated to eliminate stress and pollutants. Set the heating rate of 5~8℃/min, heat up to 1300℃, keep it for 30 minutes. The temperature rise speed should not be too fast, and the temperature cooling rate should be set. The temperature rise rate should not be higher than 10°C/min, and the temperature cooling rate should be lower than 10°C/min (5°C per minute is better).
  • When load and unload the samples, the furnace temperature should not be higher than 200 degrees. In addition, do not touch the furnace tube at high temperature with low temperature objects.
  • Make sure the heated material moisture less. For crystal water and samples with high water content generated during heating, it is recommended to dry the material firstly, and then put them in the corundum furnace tube for sintering.
  • When purging the atmosphere gases, pay attention to controlling the gas flow rate to avoid breaking due to the large temperature difference.
  • Furnace tube support frames are welded on both sides of the furnace to avoid deformation and crack because of gravity.
  • Put insulation ceramic plugs inside the tube.
  • After using it, keep the inside of the tube clean, make sure no sample remains.

Follow the above precautions can effectively extend the service life of the Alumina Furnace Tube, for more details, please click here to check our high purity alumina furnace tube.

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