GB/T 5778-1986 Test method for air tightness of expansion alloys

This standard is applicable to the qualitative test of the air tightness of iron-nickel, iron-nickel-chromium, iron-nickel-cobalt glass sealing alloys and iron-nickel, iron-nickel-cobalt ceramic sealing alloys with a diameter less than 15 mm. This method is a helium mass spectrometry leak detection method. GB/T 5778-1986 Expansion alloy air tightness test method GB/T5778-1986 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Test Method for Hermeticity of Expansion Alloys
Determi nation of hermeticityof expansion alloys
GB 5778-86
This standard is applicable to the qualitative test of the hermeticity of rods with a diameter of less than 15 mm, such as iron-nickel, iron-nickel-chromium, iron-nickel-cobalt glass-sealed alloys and iron-nickel, iron-nickel-cobalt porcelain-sealed alloys.
This method is the ammonia mass spectrometry leak detection method.
1 Terms and Definitions
1.1 Hermeticity
——Characterizes the ability of a material to prevent gas penetration. The amount of gas leaking into a vacuum container through a leak hole per unit time. The unit is Pa·m°/s. 1.2 Leakage rate——
1.3 Sensitivity
——The ratio of the change in the instrument output signal to the applied nitrogen leakage rate. 2 Test principle
The sample is mounted on a special test accessory to form a cavity, which is connected to the mass spectrometer chamber of the ammonia mass spectrometer leak detector. Ammonia is sprayed on the surface of the sample to be tested. If there is a leak in the sample, ammonia enters the mass spectrometer chamber through the leak, and part of the ammonia is ionized into positively charged ions. These ions move in a circle with a certain orbital radius under the action of the accelerating voltage and magnetic field. A collector is set at a specific position to receive only nitrogen ion flow. The intensity of the ion flow is proportional to the partial pressure of ammonia in the mass spectrometer chamber, and whether the sample is leaking or not is determined based on the ion flow intensity. 3 Test device and materials
3.1 Test devicebZxz.net
3.1.1 A hydrogen mass spectrometer leak detector of standardized production is used. Its sensitivity should meet the following requirements: when measured at 23℃, the leakage rate is 1×10-10Pa·m3/s, and at least 5% deflection should be displayed within the entire range of the instrument. 3.1.2 The test accessories are processed according to the provisions of Figure 1. Assemble the test accessories as shown in Figure 2. Issued by the National Bureau of Standards on January 14, 1986
Implemented on November 1, 1986
3.2 Materials
Ammonia: industrial pure,
Anhydrous ethanol: chemical pure;
Hydrochloric acid: industrial pure
GB 5778—86
Figure 1 Sample accessories diagram
Figure 2 Test accessories assembly diagram
1-Sample accessories, 2-Solder, 3-Conductor: 4-Sealing gasket Hexamethylenetetramine (corrosion inhibitor): chemical pure, distilled water
Sealing gasket and conduit: vacuum rubber.
Sample preparation and requirements
The sample should comply with the requirements of Figure 3 and the following table. 4.1
GB5778-
Figure 3 Sample
0.8± 0.1
For bars with a diameter not exceeding 60mm, the difference between the sample diameter and the bar diameter shall not exceed f10mm. For bars with a diameter exceeding 60mm, the sample diameter shall be 50mm. 4.3
After processing, the sample shall be degreased and slightly etched at 65℃ using a hydrochloric acid aqueous solution with a weight ratio of 1:1 and an appropriate amount of corrosion inhibitor, then rinsed with water, dehydrated with anhydrous ethanol, and baked at 105-110℃. 4.5 The sample is heated to 1050-1100℃ in a wet hydrogen (glass seal alloy) or hydrogen (ceramic seal alloy) atmosphere with a dew point of 20-30℃. After keeping warm for 30 minutes, it is cooled to below 200℃ and taken out of the furnace. 4.6 The heat-treated sample is picked up with tweezers or clean gloves, and leak tested within 24 hours after being taken out of the furnace. 5 Test steps
5.1 Start the leak detector and preheat it according to the manufacturer's regulations. 5.2 Adjust the leak detector according to the manufacturer's instructions to meet the requirements of 3.1.1. 5.3 Connect the test fitting to the leak detector, then place the sample on the sealing gasket of the test fitting, evacuate the sample, and open the vacuum valve.
GB5778-86
5.4 Use an ammonia nozzle to spray nitrogen on the surface of the sample, detect all exposed surfaces, and at a leakage rate of 1×10-10 Under the condition of Pa·m3/s, when the instrument output is greater than 5% of the full scale, ethanol is sprayed on the contact point between the sample and the sealing gasket. When it is determined that the gas leaks in through the sample, it is judged as a leak.
6 Test report
The test report should include the following contents:
Test standard number:
The brand, specification, sample number of the test material, and the test results;
Instrument model:
Test temperature;
Relative humidity;
Test unit,
Test personnel:
Test date.
Additional instructions:
This standard was proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard was drafted by Shaanxi Iron and Steel Research Institute and the 12th Institute of the Ministry of Electronics Industry. The main drafters of this standard are Guo Xianglin, Zhou Qingyun, Yuan Tong, and Yang Chensheng. 137
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