Silicon Nitride Thermocouple Protection Tube

Silicon nitride ceramic is typically used as thermocouple protection tubes for measuring the temperature of molten aluminum and titanium. Silicon nitride ceramic tube has low wettability to molten aluminum and does not corrode with molten aluminum, and the surface does not adhere to molten aluminum, so on-site maintenance is basically unnecessary, and it is more conducive to the improvement of the quality of aluminum products. Compared with cast iron, graphite and other materials, the silicon nitride protection tube will not be corroded by the aluminum liquid, and the silicon nitride ceramic is also an excellent electrical insulating material, thus ensuring the accuracy and sensitivity of the measured temperature. Gas pressure sintered silicon nitride is a 100% dense material, and liquid aluminum cannot be immersed. The silicon nitride produced by the reaction sintering process has a short service life, and there are many pores in the material, and liquid aluminum will infiltrate for a long time. In addition, the silicon nitride thermocouple protection tube has strong oxidation resistance, and can be used for a long time in the air below 1,000 degrees Celsius without oxidation. In addition, among the dense ceramics, silicon nitride ceramic has excellent thermal shock resistance, resistance to extreme cold and heat, repeated alternately in molten aluminum and air without bursting, and can maintain consistent mechanical strength. Due to the remarkable high temperature performance of silicon nitride tube, it has a service life of at least 6 months in the aluminum industry, and the actual test is more than 1 year. It has a very high cost performance.

Material Properties

Note: Although we have no reason to doubt the accuracy of the data presented, this information is offered for comparison only. Exact properties will vary depending on the manufacturing method and part configuration, and can sometimes be tailored to meet specific requirements.

Production Process

The first is slurry preparation. The components in the raw materials are ball-milled using silicon nitride grinding media and alcohol to obtain a slurry with an average particle size of 0.1-2.0 dish. Next is spray granulation treatment. The prepared slurry is stirred and then spray-dried to obtain granulation raw material powder with an average particle size of 20-300WH and an alcohol content of 0.1-0.3%. The third step is cold isostatic pressing, in which the granulated raw material powder is subjected to cold isostatic pressing to form a compact body. The fourth step is the gas pressure sintering treatment in a high temperature environment. The uniformly pressed green body is put into an atmospheric pressure sintering furnace and sintered under an inert atmosphere pressure to obtain a compact product without pores. The last is surface treatment. The sintered product is subjected to surface mechanical grinding treatment with diamond tools to obtain the final product.

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