This standard is applicable to the determination of the pore size of permeable sintered metal materials (filters, porous bearings, porous electrodes and other components with interconnecting holes) by the "bubble test" method. GB 5249-1985 Determination of pore size of permeable sintered metal materials by bubble test GB5249-1985 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Permeable sintered metal materials
Bubble test
Determination of pore sizebZxz.net
Permeable sintered metal materials -Determination of bubble test pore sizeUD( 621.762.11
:620.1:539
GB5249
This standard applies to the determination of the pore size of permeable sintered metal materials (filters, porous bearings, porous electrodes and other components with connecting holes) by the "bubble test" method. This standard is equivalent to the international standard ISO4003-1977 "Determination of pore size of permeable sintered metal materials - bubble test".
Bubble test pore size: The minimum pressure required for the formation of the first bubble on the surface of the sample by the test body passing through the sample placed in the test liquid is calculated as the minimum equivalent pressure of the sample. E is the diameter of the bubble. 2 Principle
Immerse the sample (sheet) in the test liquid and slowly pass gas (usually room temperature) into the sample. The sample aperture has a corresponding relationship with the force of escaping bubbles from the surface. Therefore, by measuring the force of escaping bubbles from the sample surface, the bubble test aperture can be calculated. The first bubble will be formed in the hole with the largest throat, which is the narrowest part of the hole. Assume that the bubble is formed at the end of an equivalent cylindrical button filled with the same liquid with known surface tension. The relationship between the diameter of the equivalent cylindrical hole and the pressure of the bubble is shown in formula (1) (2) (3): d =
Pr = 9.81ph
Formula: d-
equivalent diameter of the capillary of the bubble test hole, m; -surface tension of the test liquid, N/m;
-pressure difference on the sample under static condition, Pa; P,——test gas pressure, Pa,
-pressure of the test liquid on the horizontal plane where the bubble is formed, Pa; -test liquid density, kg/m\,
h--height from the surface of the test liquid to the surface of the sample, m. 3 Apparatus
3.1 A device capable of supplying filtered dry gas (usually air) at an appropriate pressure. (1)
(2)
3.2 A pressure regulator capable of providing stable and accurate force control. That is, a pressure regulator that gradually or step-by-step increases the pressure at a predetermined rate and can maintain a stable pressure at each step.
National Bureau of Standards 1985-0722 Issued
Implementation on 1986-07-01
3.3 Flow meter.
GB5249--85
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3.4 ​​Device for measuring gas (mechanical pressure gauge or water, mercury pressure gauge), accuracy +1%. Such devices are placed close to the bubble test tube to observe the appearance of bubbles and pressure values. 3.5 According to the shape of the sample, and to ensure that the sample is completely immersed in the liquid, the sample is immersed in a constant depth during the entire test (the height h from the liquid surface to the sample surface is greater than 10mm). A device that can more conveniently observe the appearance of bubbles on the sample surface. If the sample is convex or uneven, then in order to inspect the entire surface, the symmetry axis must be rotated horizontally. 4 Samples
Plate samples must be flat and of uniform thickness. The annular surfaces of the two ends of the tubular sample must be flat, with small deviations along the axial direction. The size and shape of the sample are shown in the figure below:
Bubble test device diagram
1-body; 2-regulating valve; 3-sample, 4-hydraulic pressure: 5P, 6-test liquid
5-test liquid
GB5249--85
Choose the test liquid according to the material of the sample. Among the pure liquids that can completely wet the metal, 95% ethanol, methanol, isocyanate, and carbon tetrachloride are commonly used liquids. The test is completed at room temperature. The parameters of the test liquid (20℃) for measuring the aperture of the bubble test of permeable sintered metal materials are shown in the following table: Test liquid
95% ethanol
Chenol
Carbon tetrachloride
Test steps
6.1 Prepare standard orifice plate
Density, 10\kg/m
Surface tension, A/m
Use laser, focused electron beam and other methods to punch holes in titanium alloy plate or stainless steel plate, and use phase analyzer, microscope, bubble test method to calibrate its aperture for calibration. 6.2 Cleaning and processing of samples
If necessary, clean and process the samples to ensure that they are clean, free of grease marks, free of substances that prevent the samples from being completely and evenly wetted, and free of any foreign matter. It is recommended to use carbon tetrachloride as the cleaning liquid and use ultrasonic cleaning. 6.3 Pre-saturation of the specimen
Usually, the specimen is pre-saturated with the test liquid for 10 to 15 minutes so that the entire pore of the specimen is filled with liquid. 6.4 Sealing and fixing the specimen
The specimen must be sealed and fixed and placed in the test tank at a certain depth of the test liquid. 6.5 Measurement
Slowly ventilate, starting from zero gas pressure drop, and gradually increase the pressure at a rate of 20 to 100 Pa/s (depending on the pore size). For tubular specimens, step-by-step pressure increase can also be used, with each step pressure of 50 to 500 Pa (depending on the pore size). The pressure must be maintained at each step, and the specimen is rotated around the symmetry axis. Carefully observe the surface of the specimen. When a string of bubbles appears from a distinct point (or several bubbles appear from several distinct points at the same time), record the initial bubble pressure, the height from the sample surface to the liquid surface, and the temperature of the test liquid. If bubbles appear near the seal, check whether it is sealed and gradually increase the pressure again.
Result expression
Calculate the bubble test pore size according to formula (1). Report the arithmetic mean of the results of the measurements, accurate to 5%. The measurement error is calculated using the standard deviation method. Test Report
The test report should include the following items:
a. Indicate the number of this standard;
Details necessary to identify the sample;
Liquid used;
Rate of rise;
The position of the first bubble;
Results obtained:
GB5249-85
Indicate all operations not specified by this standard or considered optional; Indicate any factors that may affect the results.
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GB5249---85
Appendix A
(Supplement)
A.1 The bubble test shall be used only as a quality control test and not as a test to determine the grade of porous materials or to accurately determine the pore size and pore size distribution.
A,2 The maximum pore size determined by the bubble test may be a single local defect and not represent the micropores of the porous material. A.3 When the gas pressure is increased to the point where the smallest bubbles appear, different forms of bubbles appear on the surface of the sample. A corresponding pore size can be obtained for each form of bubble pressure.
A,4 The bubble test cannot measure the maximum size of particles that pass through the sample pores. It can be expected that the filter can block particles larger than the maximum pore size determined by the bubble test, and also blocks particles much smaller than the maximum pore size. For ease of estimation, some useful empirical coefficients are used. For porous metals made of uniform spherical particles, it is about 0.4, and for porous metals made of irregular particles, it is about 0.2. These coefficients must be multiplied by the bubble test pore size calculated by equation (1). A.5 When the sample consists of a fine porous layer supported on a coarse porous substrate, the characteristic bubble test pore size measured is fine. In this case, the test should cause the bubbles to appear on the surface of the fine porous layer. 285
GB5249-85
Appendix B
(reference)
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Water is one of the cheapest useful substances in nature. It has stable performance and is non-toxic. Therefore, water is also an important test liquid. However, when choosing water as the test liquid, attention should be paid to the wettability of water on porous metals of different materials. The calculation formula is: d
Formula: Wetting angle of water on metal materials.
Additional instructions:
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This standard was proposed by the Ministry of Metallurgical Industry of the People's Republic of China and China Nonferrous Metals Industry Corporation. This standard was drafted by Baoji Rare Metals Processing Institute. The main drafters of this standard are Hu Guizhen and Shi Yongjin. 286
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