A corundum tube is a very important part of the tube furnace.
Since it is alumina material, thermal shock resistance ability is poor, the service life of it is very limited, usually, propose to keep up cooling rate under 5 ℃ / min, slowly is better, must be set in the process of cooling and cooling curve, can’t let its natural cooling to room temperature directly from high temperature so that the pipe is easy to crack and the temperature of the pipe generally easy to crack during the 800-1000 ℃.
1.New corundum tubes or long-unused corundum tubes need to be roasted at about 200-300 degrees for 5-6 hours to remove the water inside the corundum tubes, which is conducive to extending the service life of the corundum tubes. Water is an important reason for the rupture of the corundum tubes. In the tube furnace burned in the sample, especially to be burned to about 1300℃ sample, the best water content should be less (adsorption water, crystal water, water may be generated in the heating process, etc.), it is recommended that the sample is pre-burned, and then into the tube furnace.
2.Keep the furnace tube clean and sanitary, and no residual substances reacting with Al2O3 can be left in the furnace tube. When burning materials, to make the service life of the furnace tube longer, do not directly put the materials on the furnace tube, the use of a boat crucible.
3.When heating, please be sure to put alumina heat insulation furnace plug inside the furnace tube, 2 on one side, a total of 4, the position is between the hot zone and the cold zone. If the furnace plug is not put, the temperature at both ends of the furnace tube is high, the o-ring in the flange cannot bear the higher temperature, making the airtightness is not good, the furnace plug at both ends of the furnace tube is conducive to the formation of a balanced temperature field.
4.the flange at both ends of the corundum tube is recommended to be supported by a support frame, so as not to apply vertical stress to the corundum tube, and not to make the corundum tube bending at high temperature or because of the stress and fracture.
5.if the continuous use of the furnace, you can only reduce the temperature of the furnace to about 200℃ to maintain, do not need to reduce the room temperature, which is conducive to the service life of the furnace tube.
6.The temperature resistance of the corundum tube is related to its purity. The higher the purity, the higher the temperature resistance.
7.The excessive temperature difference between inside and outside the furnace and the excessive compressive stress on the screws at both ends together cause the easy fracture. One solution is to wrap the exposed part of the corundum tube in an insulating material. Of course, the cheapest one is asbestos, which is not recommended, but there is no way out. Other insulation materials are too expensive.
8.Do not strongly touch the corundum furnace tube, do not use low-temperature objects to touch the high-temperature furnace tube. It is best not to sample and add samples under high temperatures, which is easy to damage the furnace tube of corundum.
9.Recommended heating rate: ≤5℃/min below 500℃;500-800 ℃ to 10 ℃ / min or less;800-1000 ℃ to 5 ℃ / min or less;The 1000-1400 ℃ or less 3 ℃ / min;1400-1600 ℃, 2 ℃ / min or less.
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