Nitrogen in titanium alloys mainly exists in the form of nitrides, such as: TiN, VN, FeN, etc., only a small part of nitrogen exists in the form of atoms. If the nitrogen content in the titanium alloy is too high, it will lead to the loosening of its macrostructure and even the formation of bubbles. Decreased toughness and increased hardness, resulting in increased notch sensitivity, which greatly hindered the application of titanium and titanium alloys. Therefore, in the production of titanium and titanium alloys, it is necessary to accurately analyze the nitrogen content in sponge titanium, titanium and titanium alloys, and strictly control their content to ensure product quality. Because the melting point of the nitrides in titanium and titanium alloys is very high (eg, the melting point of titanium nitride is 2950 ° C), it is difficult to directly determine its content by pulse inert gas fusion method. Through the selection and combination of different graphite crucibles, fluxes, sample weights, and heating power, the scientific research personnel realized the pulse inert gas fusion-thermal conductivity method of LECO TC600 oxygen and nitrogen combined analyzer for sponge titanium, titanium and titanium alloy Determination of nitrogen content.
The experimental principle is as follows: put the sample into the flux into the graphite crucible, protect it with inert gas (helium), and release oxygen and nitrogen at a sufficient temperature. Oxygen combines with carbon to form CO, and nitrogen is released as N2. The gas released by the sample is carried by the rare earth copper oxide heated by the inert gas, so that CO is converted into CO2, H2 is converted into H2O, CO2 is absorbed by alkali asbestos, and H2O is absorbed by anhydrous magnesium perchlorate. Then, nitrogen enters the thermal conductivity measuring cell in the form of N2, and the output of the Huisitong bridge is integrated and compared with the reference substance to respond, and is displayed in the form of percentage of nitrogen.
The test results are as follows: using a graphite high-temperature crucible pre-loaded with 0.050g of high-purity graphite powder and using a high-purity nickel basket as the flux, the best measurement conditions of the combined analyzer are: degassing power 5600W, analysis power 5000W, degassing time 20s, cooling time 15s, flushing time 15s, integration time 65s. By measuring standard samples and comparing with other unit data, and putting them into production testing, it is proved that the method is easy to operate, fast in analysis, accurate in data and precise in meeting the needs of scientific research and production.