GB/T 5126-2001 Eddy current flaw detection method for cold drawn thin wall tubes of aluminium and aluminium alloys
Some standard content:
GB/T5126--2001
This standard is a revision of GB/T5126-1985 "Eddy Current Flaw Detection Method for Cold-drawn Thin-walled Tubes of Aluminum and Aluminum Alloys". On the basis of the original standard, the form is standardized, the test specifications are expanded, the subject content, referenced standards, and definitions are supplemented, the general provisions, standard specimens, flaw detection sensitivity, and flaw detection steps are revised, and the referenced technical terms are standardized. This standard is equivalent to ASTME215:1992 "Standard Implementation Method for Calibration of Electromagnetic Equipment for Seamless Aluminum Alloy Tubes" in terms of scope of application, instruments and equipment, and artificial standard defects. This standard also quotes GB/T12604.6-1990 "Non-destructive Testing Terminology Eddy Current Testing" based on the development status of domestic production, use, and testing.
This standard replaces GB/T5126-1985 from the date of implementation. This standard is proposed by the China Nonferrous Metals Industry Association. This standard is under the jurisdiction of the China Nonferrous Metals Industry Standard Metrology and Quality Research Institute. This standard was drafted by Northeast Light Alloy Co., Ltd. The main drafters of this standard are Chen Zhiqiang, Zhang Yuping, Lv Xinyu, Shao Yutian and Liu Yun.
1 Scope
National Standard of the People's Republic of China
Aluminum and aluminum alloy cold drawn thin wall tubes
Eddy current flaw detection method
Eddy current inspection method for cold drawn thin wall tubes of aluminum and aluminum alloyGB/T5126-2001
Replaces GB/T5126-1985
This standard specifies the eddy current inspection method for cold drawn thin wall tubes of aluminum and aluminum alloy using a single frequency excitation and external through-type coil detection system. The content includes general requirements for eddy current inspection, instruments and equipment, parameter selection, inspection steps, etc. This standard is applicable to the inspection of aviation high-pressure conduits, ordinary conduits and general-purpose aluminum and aluminum alloy cold drawn thin wall round tubes with an outer diameter of 6~38mm and a wall thickness of 0.5~～1.5mm. 2 Referenced standards
The clauses contained in the following standards constitute the clauses of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T9445-1999 Qualification and certification of non-destructive testing personnel GB/T12604.6—1990 Terminology of non-destructive testing Eddy current testing 3 Definitions
This standard adopts the following terms defined in GB/T12604.6. 3.1 Eddy current inspection method is a method of detecting whether there are defects in products by using the principle of electromagnetic induction to generate eddy currents on the surface and near the surface of conductive test pieces. 3.2 Encircling coil refers to the annular coil and components surrounding the outer wall of the test piece. 3.3 Exciting frequency refers to the fundamental frequency of the AC power supplied to the exciting coil in the detection coil. 3.4 Phase analysis method method phase analysis is an analytical method that identifies various variables in the test piece based on the different phase angles of the detection signal. 3.5 Modulation analysis method is an analysis method that uses the difference in modulation frequency of the modulation envelope on the carrier signal to identify various variables in the test piece. 3.6 Signal to noise ratio refers to the ratio of the amplitude of the defect signal at the output end of the eddy current flaw detector to the maximum noise amplitude. 3.7 Speed-sensitive instrument speed-sensitive instrument Instrument that produces a signal response to changes in the flaw detection speed. 3.8 Edge effect
When the detection coil is at the end of the pipe, the effect caused by the distortion of the eddy current flow path. National Quality and Technical Supervision Department 2001-05-29 approved 204
2001-11-01 implementation
3.9 Differential coil differential coil GB/T 5126—2001
Two or more coils are connected in reverse series, and the difference in adjacent areas on the test piece will cause the eddy current detection system to produce an unbalanced index coil. 3.10 Fill factor of the detection coil The ratio of the cross-sectional area of the test piece to the cross-sectional area of the coil. 3. 11 Difference of induced-potential The difference in induced voltage between the two output ends of the differential coil in the balanced state. 4 Principle
4.1 The basic principle of eddy current testing is electromagnetic induction. When an alternating magnetic field acts on a conductor, eddy currents are generated on the surface and near the surface of the conductor. The eddy current induced magnetic field reacts to the alternating excitation magnetic field, hindering its change. The degree and size of this hindering effect are related to the physical properties of the inspected pipe.
4.2 The eddy current test of pipes is to pass the inspected pipe through a coil with an alternating current, and use the principle that the impedance of the detection line changes with the change of pipe specifications, conductivity, and magnetic permeability. The detection instrument amplifies, converts, phase analyzes, modulates and analyzes the signal, and finally uses sound and light alarms to record, mark and sort the defective pipes. 5 General requirements
5.1 Personnel
Personnel engaged in eddy current testing shall hold qualification certificates issued by relevant competent authorities that comply with the technical methods specified in GB/T9445. Personnel at all levels can only engage in work that is consistent with their technical aspects and qualification levels. 5.2 Pipes
The surface of the pipe should be smooth, clean, and free of burrs at the ends. The curvature and ovality should meet the requirements of relevant standards. 5.3 Environment
5.3.1 There should be no strong magnetic field, vibration, corrosive atmosphere and other interference that may affect the normal operation of instruments and equipment near the inspection site. 5.3.2 The temperature and relative humidity of the inspection site should be controlled within the range of the instruments and equipment, with the temperature not higher than 40℃ and the relative humidity not higher than 80%.
5.3.3 The inspection site should be clean and ventilated.
5.4 Instruments and equipment
5.4.1 All instruments and equipment shall be accepted according to relevant standards before they can be put into use. 5.4.2 Equipment should be calibrated regularly
5.5 Power supply
The fluctuation of power supply voltage should not exceed ±10% of rated voltage. 6 Inspection system
The eddy current inspection system mainly includes eddy current flaw detector, detection coil, transmission and sorting device. 6.1 Eddy current flaw detector
Generally, it should have the functions of excitation, amplification, signal processing, signal display, sound and light alarm, and signal output. 6.2 Detection line waist
6.2.1 Generally, differential and external through-type coils should be used. 6.2.2 The inner diameter of the detection coil should match the outer diameter of the inspected pipe, and its filling factor should not be less than 0.6. 6.2.3 The zero potential of the detection line under no load and load should be similar. The difference between the no-load zero potential and the loaded zero potential and the ratio of the no-load zero potential should not be greater than 30%.
6.2.4 The adjustment range of the detection coil seat should be adapted to the specifications of the inspected pipe. 6.3 Transmission device
GB/T 5126 -- 2001
6.3.1 The transmission device mainly includes the feeding and discharging racks, the material discharging device, the transmission roller, the guide device, the finished and scrapped product sorting and other parts. The transmission device should be stable and make the inspected pipe pass through the detection coil concentrically under the condition of minimum vibration. 6.3.2 The eddy current transmission device should be able to reliably and stably transmit the inspected pipe and maintain the stability of the transmission speed. If a detection instrument that responds to the speed is used, the fluctuation range of the transmission speed should not exceed ±5%. 6.4 Sorting device
The electrical control system that performs the sorting should be able to distinguish between finished or scrap pipes and accurately mark the defects. Complete the clearing of the sorting signal, and at the same time, the defective and non-defective pipes are separated by mechanical and electrical devices. 7 Comparison sample tube
7.1 The comparison sample tube is a sample tube that is processed with artificial defects and is used to adjust the detection sensitivity, calibrate the performance of the detection instrument and equipment, and serve as a product acceptance standard.
7.2 The comparison sample tube should be a low-noise tube with the same alloy grade, specification, surface state, and heat treatment state as the inspected tube, and without natural defects. At the same time, its curvature and ovality should meet the relevant requirements. 7.3 The artificial defects on the comparison sample tube are all radial circular through holes perpendicular to the tube wall. 7.4 The length of the defective sample tube should be no less than 2m. Two groups of circular through holes are drilled vertically along the radial direction of the tube, and the group is d. Artificial through holes, group db. There are three artificial through holes in each group. The axial distance between two adjacent holes is 150mm±10mm. The circumferential distribution of the three holes differs by 120°±5. The minimum distance from the artificial through hole to any end of the tube is 500mm. 7.5 The pipe used to make the comparison sample tube should not have any noise greater than 80% of the artificial through hole indication. 7.6 The comparison sample tube size and through hole distribution are shown in Figure 1. 3 d.
150150
3 d, hole
150150
Figure 1 Comparison sample tube specifications and corresponding artificial through hole positions 7.7 The comparison sample tube specifications and corresponding artificial through hole specifications and sizes shall comply with the provisions of Table 1. Table 1
Comparison sample tube
(wall thickness 0.5～1.50)
Outer diameter D
Artificial through hole (aperture deviation: ±0.05) d
Comparison sample tube
(wall thickness 0.5~1.50)
Outer diameter D
21～22
GB/T 5126—2001
Table 1 (end)
Artificial through hole (aperture deviation: ±0.05) Grade Abzxz.net
7.8 Appropriate methods should be used to number and identify the comparison sample tubes. 7.9 If the comparison sample tube produces signals other than those caused by artificial defects, it should be replaced. 7.10 If artificial defects of other shapes or sizes are used, they must be determined by negotiation between the supply and demand parties. 8 Inspection operation procedures
8.1 Before the eddy current inspection, the appearance size, surface and end quality of the pipe should be inspected. 8.2 The eddy current flaw detection instrument for pipes should be debugged and tested after preheating and stabilization. Class B
8.3 The detection frequency should be within the range of 1 to 125kHz. Select the appropriate excitation frequency to debug the detection sensitivity of the eddy current flaw detection instrument and equipment. 8.3.1 According to the specifications of the inspected pipe, select the appropriate detection coil. 8.3.2 Use d. Artificial through-hole to adjust the phase so that it provides the best signal-to-noise ratio on the recording curve for d. Artificial through-hole, that is, the ratio of the recording amplitude of da artificial through-hole to the recording amplitude of the noise signal is not less than 6dB. 8.3.3 Adjust the appropriate sensitivity level so that it provides a clearly recognizable indication with a certain amplitude for d artificial through-hole on the recording curve, and all three db artificial through-holes are displayed (alarm), three d. There is no display (alarm) for artificial through-holes. The eddy current flaw detection instrument and equipment are in the waiting-for-inspection operation state with this sensitivity calibration, and then the eddy current inspection can be carried out on each pipe. 8.3.4 At the end of each continuous inspection for 2 hours and at the end of the inspection, the sensitivity of the eddy current inspection should be calibrated according to 8.3.2 and 8.3.3. If the change in the sensitivity data is found to be greater than ±2dB, the pipes inspected after the last sensitivity calibration should be re-inspected. 8.4 The transmission speed of the equipment should meet the requirements of the comprehensive performance indicators of the eddy current detection system. Generally, 20~40 m/min is used. The maximum detection speed can be determined according to the passband allowed by the filter of the detection instrument. 8.5 Adjust the transmission equipment to ensure the concentricity of the pipe and the detection coil. 9 Evaluation and processing of inspection results
9.1 The final display equivalent value of the defect of the inspected pipe is less than the display value of the artificial through-hole or there is no alarm signal, which is a qualified product. 9.2 If the final display equivalent value of the defect of the inspected pipe is greater than or equal to the display value of the artificial through hole or the alarm signal, it is a defective product or the pipe section where the defect is located is a defective product. 9.3 If there is any doubt about the defect signal, a re-exploration or metallurgical and process analysis should be carried out to determine the cause and decide whether to accept it. 9.4 For acceptance without fixed length, the pipe after the defect is cut off should be re-inspected. 10 Inspection report
The inspection report shall be issued by personnel with eddy current testing technical qualification certificate of level 1 or above, and generally include the following contents: a) pipe manufacturer;
b) inspection date and report filling date;
c) alloy brand, specification, state, batch number, etc.; d) eddy current flaw detection instrument and coil, model and number; e) use and acceptance standards;
GB/T5126—2001
f) inspection quantity (weight) and acceptance quantity (weight); g) inspection personnel and review personnel;
h) comparison sample pipe specification and number.
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