This standard specifies the test method for residual stress of brass tubes used in heat exchangers using ammonia. This standard is applicable to the test of residual stress of brass tubes used in heat exchangers. GB/T 8000-2001 Test method for residual stress of brass tubes used in heat exchangers Ammonia fumigation test method GB/T8000-2001 Standard download decompression password: www.bzxz.net

GB/T 8000-2001
This standard is a revision of GB/T8000--1987 "Internal stress of brass tubes for heat exchangers" ISO6957:1988 (E) "Ammonia fumigation test of copper alloys against stress corrosion". This standard has made the following modifications and supplements to the original standard: 1 "Internal stress" is changed to "residual stress"; 2 A chapter "Scope" is added;
3 * The terms in the "Definition" refer to the term definitions in ISO6957; 4 Important supplements are made to the "Principle" chapter; Ammonia fumigation test method" is revised, and the revision mainly refers to 5 "Instrumentation" chapter. The magnification of the magnifying glass is changed from "5×~～10×" to "10×~15×"; 6 "Test specimen" chapter clearly stipulates that "the number of parallel test specimens is generally 2". And add "The test specimen shall not have defects such as bending, flattening, scratching, peeling, wrinkling, bumps, etc. When cutting the sample, there shall be no additional stress such as clamping or artificial breaking. 7 "Test conditions" chapter clearly stipulates that "the sample should be placed upright in the dryer", 8 "Test steps" chapter changes "wipe dry" to "air dry (or bake)" to avoid corrosion products embedded in cracks during wiping, affecting the observation results;
9 Some individual clauses in the original standard have been appropriately adjusted, rewritten and improved. From the date of implementation, this standard will replace GB/T8000-1987. This standard is proposed by the State Bureau of Nonferrous Metals Industry. This standard is under the jurisdiction of the China Nonferrous Metals Industry Standard Metrology and Quality Research Institute. This standard was drafted by Luoyang Copper Processing Group Co., Ltd. The main drafters of this standard are: Qin Yong, Zhang Jinghua, Mei Hengxing, Meng Huijuan, Yang Lijuan, Lu Junpan, Zhang Zhiqiang. 672
1 Scope
National Standard of the People's Republic of China
Residual stress test method for brass tubes for heat exchangers Ammonia fumigation test method
Brass tube in heat-exchanger-- Ammonial test for residual stress corrosion This standard specifies the test method for testing the residual stress of brass tubes used in heat exchangers using ammonia. This standard applies to the test of residual stress of brass tubes used in heat exchangers. 2 Definitions
This standard adopts the following definitions.
2.1 Stress corrosion cracking stress corrosion cracking Spontaneous damage caused by the cracking of metals under the combined action of corrosion and residual or applied stress. 2.2 Applied stress applied stress
Stress caused and existing inside an object during the application of external loads 2.3 Residual stress residual stress
Stress remaining inside an object as a result of plastic deformation. 3 Principle
GB/T 8000--2001
Replaces GB/T 8000---1987
Using the principle that brass is highly sensitive to stress corrosion cracking in an ammonia atmosphere, the sample is exposed to an ammonia atmosphere for a certain period of time, and then the cracks are inspected at a magnification of 10× to 15×. Reagents and Materials
Analytical pure reagents should be used in the test.
4. 1 Ammonia water [25%~28%] (m/m).
4.2 Nitric acid [(1+1) or (1+2)] solution. 4.3 Organic solvent (ethanol or acetone).
5 Instruments and devices
5.1 Sealed container: $240~$280mm dryer. 5.2 Pickling tank and water washing tank.
5.3 Magnifying glass: magnification 10×~15×. 6 Test specimens
6.1 The length of the test specimen is 150mm±10mm. For products with special requirements by users, the test specimen size shall be determined by negotiation between the supply and demand parties. Approved by the State Administration of Quality and Technical Supervision on March 26, 2001, implemented on August 1, 2001
GB/T 8000-2001Www.bzxZ.net
6.2 The number of parallel test specimens is generally 2. If there are other provisions on the product label or other requirements of the user, it can be determined through negotiation. 6.3 Each sample should be marked for easy identification (if necessary). However, external stress should be avoided in the sample. 6.4 The sample shall not have defects such as bending, flattening, scratching, peeling, wrinkling, bumping, etc. When cutting the sample, there shall be no external stress such as clamping and artificial breaking.
7 Test conditions
7.1 The sample shall not be in direct contact with ammonia water, let alone contact with each other. The sample shall be placed upright in the desiccator so that ammonia gas can pass through all surfaces as unimpeded as possible.
7.2 The test solution shall not be reused.
7.3 Pickling and ammonia fumigation shall be carried out in a fume hood. 7.4 The test temperature is room temperature. Under arbitration conditions, the test temperature is 25℃±1℃. 7.5 The nitrogen fumigation time is 4h.
8 Test steps
8.1 Degrease the sample with an organic solvent (4.3). 8.2 After degreasing and defatting, remove the oxide film directly in the pickling solution (4.2), then wash the residual acid on the surface of the sample with clean water and immerse it in water.
8.3 Move the sample to a sealed container (5.1), pour 200mL of ammonia water (4.1) into it, and immediately cover it. 8.4 After 4 hours of ammonia fumigation, take out the sample from the dryer, wash it with water, and then use the pickling solution (4.2) to remove the corrosion products according to the requirements of 8.2. After pickling, wash the sample with water, dry it (or bake it), and then use a magnifying glass (5.3) to check whether there are cracks on the surface of the sample (in order to eliminate the influence of local stress caused by cutting the sample, cracks within 10mm from both ends of the sample are not counted). 9 Test report
The test report should include the following contents:
a) Source of sample, alloy grade, state, specification, batch number; b) Number of parallel samples;
c) Test temperature;
d) Test result: crack or no crack;
e) Test date;
f) Signature of the tester and retester;
g) Number of this standard.
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