Pulsed eddy current device for distinguishing corrosion defects of inner and outer surfaces of metal and detection method

Abstract

The invention discloses a pulsed eddy current device and a detection method for distinguishing corrosion defects of inner and outer surfaces of metal, and the method comprises the following steps: placing an excitation coil above a lossless detected metal test piece, and recording a detection signal of a TMR sensor of each channel as a reference signal; placing an excitation coil above the metal test piece to be detected, and recording a detection signal of the TMR sensor of each channel as a detection signal; making a ratio of the detection signal of each channel to a corresponding reference signal to generate a ratio curve of each channel; all the ratio curves are placed in the same coordinate system to form a full-channel ratio change curve graph, and whether the metal test piece to be detected has internal defects or external defects or not is judged according to the change trend of the curves in the full-channel ratio change curve graph. The position of the corrosion defect can be accurately judged, particularly, the corrosion defects of the inner surface and the outer surface can be effectively recognized, and the detection accuracy and reliability are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of pipeline defect detection, and in particular to a pulse eddy current device and a detection method for distinguishing corrosion defects on the inner and outer surfaces of metal. Background Art

[0002] Pipelines, storage tanks, gas cylinders and other pressure-bearing equipment are exposed to corrosive environments for a long time, and corrosion defects are easily generated on the internal and external surfaces, which not only lead to equipment performance degradation, but also cause major safety accidents such as leakage and explosion. Therefore, timely detection and accurate assessment of corrosion conditions are crucial for the safe operation and life management of equipment.

[0003] Pulsed eddy current testing (PECT) is an efficient non-destructive testing technology with the ability to detect and penetrate the coating layer in a non-contact manner, and can effectively detect defects such as metal corrosion. It is suitable for high temperature and high pressure environments, and can be used for detection on workpieces of complex shapes. It mainly extracts characteristic quantities through time domain response signals, such as peak time, zero crossing point, slope and other signal analysis methods to achieve the detection and quantification of defects in the coating layer. At present, the characterization of defects by this technology is mainly achieved through the remaining wall thickness of the workpiece, and it mainly focuses on the detection and quantification of internal corrosion defects. However, under actual working conditions, there may be internal and external corrosion defects on the surface of the workpiece at the same time, which makes the existing signal analysis method limited and affects the detection results. For pulsed eddy current testing technology, there is currently no suitable means to distinguish between internal and external surface defects of metal at the same time. How to accurately distinguish internal and external corrosion defects without removing the coating is still a major difficulty in the existing technology.

[0004] At present, the pulse eddy current method retrieved for distinguishing internal and external surface corrosion defects is "A ferromagnetic pipeline flaw detection device based on pulse eddy current and an internal and external detection method (authorization announcement number CN 114965680 B, 2024.11.15)". It uses reverse pulse signals input into two excitation coils to form a uniform tangential magnetic field. First, multiple sets of reference signals are obtained by adjusting the height of the TMR sensor on a defect-free specimen; and the detection signal is obtained on the specimens with surface defects and internal defects respectively. The defect information is judged by whether the detection signal and the multiple sets of reference signals have intersections in the same coordinate system and the time period of the intersection. This method can distinguish the internal and external defect positions of the specimen. However, there are still some shortcomings. This method needs to adjust the position of the TMR sensor multiple times at the same lifting height to collect the initial reference signal group, which takes a lot of time and is complicated to operate. If the number of reference signals is too small, there will be misjudgment and omission of defect information.

[0005] Therefore, the pulsed eddy current device and method for distinguishing corrosion defects on the inner and outer surfaces of metals provided in the present application solve the current problems in which the operation is complex and the number of reference signals is too small, which may lead to misjudgment and omission of defect information. Summary of the invention

[0006] Therefore, the purpose of the present invention is to provide a pulse eddy current device and method for distinguishing corrosion defects on the inner and outer surfaces of metal. In the case of a coating layer, the corrosion defects on the inner and outer surfaces of metal can be distinguished, and simultaneous detection of corrosion defects on the inner and outer surfaces of metal can be achieved.

[0007] In order to achieve the above object, the present invention provides a pulsed eddy current detection method for distinguishing corrosion defects on the inner and outer surfaces of metals, comprising the following steps: S1. Place the excitation coil above the non-destructive metal specimen to be tested, and record the detection signal of the TMR sensor of each channel as the reference signal; S2, placing the excitation coil above the metal specimen to be tested, and recording the detection signal of the TMR sensor of each channel as the detection signal; S3, the detection signal of each channel is respectively compared with the corresponding reference signal to generate a ratio curve of each channel; S4. All ratio curves are placed in the same coordinate system to form a full-channel ratio change curve diagram, and whether the metal specimen to be tested has internal defects or external defects is determined based on the change trend of the curves in the full-channel ratio change curve diagram.

[0008] Further preferably, in S4, judging whether the metal specimen to be tested has internal defects or external defects according to the change trend of the curve in the full channel ratio change curve diagram includes: S401, dividing all ratio curves in the full-channel ratio change curve diagram into three stages according to time periods, wherein the time section of the first stage is 0-0.005s, the time section of the second stage is 0.005s-0.02s; and the time section of the third stage is after 0.02s; S402. Analyze the change trends of all ratio curves in the second stage. When the ratio curves of different channels have no intersection in the second stage, it is judged as an external surface corrosion defect. When the ratio curves of different channels intersect in the second stage and the curve amplitude reverses in size, it is judged as an internal surface corrosion defect.

[0009] The present invention also provides a pulsed eddy current device for distinguishing corrosion defects on the inner and outer surfaces of metals, which is used to implement the steps of the pulsed eddy current method for distinguishing corrosion defects on the inner and outer surfaces of metals, and includes a detection module and an analysis module, wherein the detection module includes a shell and an excitation coil and a multi-channel TMR sensor arranged inside the shell; The excitation coil is parallel to the tested object and sends pulse excitation to the tested object; The multi-channel TMR sensor is used to receive the magnetic field detection signal parallel to the axis direction of the excitation coil fed back by the tested piece; The analysis module is used to receive the detection signal of the multi-channel TMR sensor.

[0010] The ratio curve of each channel is generated by comparing the received detection signal of each channel with the corresponding reference signal; all the ratio curves are placed in the same coordinate system to form a full-channel ratio change curve diagram, and according to the change trend of the curves in the full-channel ratio change curve diagram, it is judged whether the metal specimen to be tested has internal defects or external defects.

[0011] Further preferably, the multi-channel TMR sensor is composed of a plurality of identical TMR sensors arranged in a linear array, with a line perpendicular to the arrangement diameter of the TMR sensors as a dividing line, and the structures on both sides are symmetrical, thereby ensuring that the detection data acquired by the TMR sensors on both sides are the same.

[0012] Further preferably, in the multi-channel TMR sensor, one TMR sensor is arranged at the center of the two coils, and the other TMR sensors are evenly spaced along the diameter direction of the excitation coil, and the TMR sensor at the outermost edge is located at the outer edge of the excitation coil.

[0013] Further preferably, the uniform interval is calculated according to the following formula: The center-to-center spacing ΔS of the TMR sensor is: ΔS = D / (N-1); Wherein, D is the diameter of the excitation coil, N is the number of TMR sensor excitations, and N is not less than 5.

[0014] Further preferably, when obtaining the reference signal or the detection signal, A 2 Hz low-frequency square wave current is passed through the excitation coil, and the signal received by the TMR sensor of each channel is recorded and converted into a voltage signal, which is recorded as the reference signal U 0 or detection signal.

[0015] The present application discloses a pulse eddy current device and detection method for distinguishing corrosion defects on the inner and outer surfaces of metal. It does not require multiple adjustments to the position of the TMR sensor and can accurately determine the location of the corrosion defects. In particular, it can effectively identify corrosion defects on the inner and outer surfaces, significantly improving the accuracy and reliability of detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of a pulsed eddy current device for distinguishing corrosion defects on the inner and outer surfaces of metal provided in an embodiment of the present invention.

[0017] Figure 2 It is a flow chart of a pulsed eddy current metal inner and outer surface corrosion defect detection method provided in an embodiment of the present invention.

[0018] Figure 3 It is a position relationship diagram between the pulsed eddy current device and the metal specimen to be tested under the coating layer working condition provided in an embodiment of the present invention.

[0019] Figure 4 It is a curve diagram of the overall detection data of the external surface corrosion provided in the embodiment of the invention.

[0020] Figure 5 It is an enlarged graph of the detection data curve of the second stage of external surface corrosion provided in the embodiment of the invention.

[0021] Figure 6 It is a curve diagram of the overall detection data of the inner surface corrosion provided in the embodiment of the invention.

[0022] Figure 7 It is an enlarged graph of the detection data curve of the second stage of inner surface corrosion provided in the embodiment of the invention.

[0023] In the figure: 1. excitation coil; 2. TMR sensor; 3. shell; 4. metal test piece; 5. coating layer; 6. external surface corrosion defect; 7. internal surface corrosion defect; 2-1. first TMR sensor; 2-2. second TMR sensor; 2-3. third TMR sensor. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below through the accompanying drawings and specific embodiments.

[0025] Example 1 like Figure 1 As shown, an embodiment of one aspect of the present invention provides a pulse eddy current device for distinguishing corrosion defects on the inner and outer surfaces of metals, comprising a detection module and an analysis module, wherein the detection module comprises a housing 3 and an excitation coil and a multi-channel TMR sensor arranged inside the housing; It includes a detection module and an analysis module, wherein the detection module includes a shell, an excitation coil 1 and a multi-channel TMR sensor 2 arranged inside the shell; The excitation coil 1 is parallel to the device under test and sends pulse excitation to the device under test; the excitation coil 1 is set to one and is set in the center. Figure 1 As shown, the rectangles on both sides of the dotted line represent the cross-sectional views of the excitation coil on the left and right sides when the excitation coil is cut along the middle transverse axis. The excitation coil 1 is wound with enameled wire to form a circular coil, and a periodic pulse square wave signal is loaded. The excitation signal is transmitted to the excitation coil 1 through a power amplifier to generate a primary magnetic field.

[0026] The multi-channel TMR sensor is used to receive the magnetic field detection signal parallel to the axis direction of the excitation coil fed back by the test piece; further preferably, the multi-channel TMR sensor is composed of a plurality of identical TMR sensors arranged in a linear array, and a line perpendicular to the diameter of the TMR sensor arrangement is used as a dividing line, and the structures on both sides are symmetrical, thereby ensuring that the detection data obtained by the TMR sensors on both sides are the same.

[0027] In the multi-channel TMR sensor, a TMR sensor is arranged at the center of the two coils, and the other TMR sensors are evenly spaced along the diameter direction of the excitation coil, and the TMR sensor at the outermost edge is located at the outer edge of the excitation coil.

[0028] Further preferably, the uniform interval is calculated according to the following formula: The center-to-center spacing ΔS of the TMR sensor is: ΔS= D / ( N-1); Where D is the diameter of the excitation coil, N is the number of TMR sensors to be excited, and N is not less than 5. This arrangement ensures that the sensors are evenly distributed on the excitation coil, thereby improving the balance of signal acquisition and the accuracy of the detection results.

[0029] The excitation coil 1 and the TMR sensor 2 are packaged in a device housing 3 , and the device housing 3 is mainly made of engineering plastic material.

[0030] The analysis module is used to receive the detection signal of the multi-channel TMR sensor. According to the ratio of the received detection signal of each channel and the corresponding reference signal, a ratio curve of each channel is generated; all the ratio curves are placed in the same coordinate system to form a full-channel ratio change curve diagram, and according to the change trend of the curve in the full-channel ratio change curve diagram, it is judged whether the metal specimen 4 to be tested has internal defects or external defects.

[0031] The pulsed eddy current detection method provided in the following embodiment 2 is used to specifically determine whether the metal specimen to be tested has internal defects or external defects.

[0032] Example 2 like Figure 2 As shown, a pulsed eddy current detection method for distinguishing corrosion defects on the inner and outer surfaces of metals comprises the following steps: S1. Place the excitation coil above the non-destructive metal specimen to be tested, and record the detection signal of each channel TMR sensor as the reference signal; specifically, pass a 2Hz low-frequency square wave current into the excitation coil 1. At this time, record the signal received by each channel TMR sensor and convert it into a voltage signal. This signal is used as the reference signal U 0； S2. Place the excitation coil above the metal specimen to be tested, and record the detection signal of each channel TMR sensor as the detection signal; place the pulse eddy current device on the surface of the metal specimen to be tested, such as Figure 3 The inspected object includes a metal test piece 4 and a coating layer 5, the test piece thickness is 10 mm, and the coating layer thickness is 20 mm, wherein an outer surface corrosion defect 6 and an inner surface corrosion defect 7 are provided on the metal test piece 4.

[0033] Place the pulsed eddy current device above the area with external surface corrosion defects on the specimen, and pass a 2Hz low-frequency square wave current into the excitation coil 1. Record the signal received by the TMR sensor of each channel and convert it into a voltage signal as the detection signal U x S3, the detection signal of each channel is respectively compared with the corresponding reference signal to generate a ratio curve of each channel; The formula is: in: is the ratio calculated for the i-th TMR channel; is the detection signal received by the i-th TMR channel above the corrosion defect area outside the specimen; is the reference signal received by the i-th TMR channel above the intact area of ​​the specimen.

[0034] Since the excitation coil 1 is circular, the TMR sensor 2 is arranged linearly, and the line perpendicular to the diameter of the TMR sensor 2 is used as the dividing line, the structures on both sides are symmetrical, so the detection data obtained by the TMR sensors on both sides are the same. Therefore, only the detection data on one side needs to be analyzed. The selected TMR sensors are numbered 2-1, 2-2 and 2-3.

[0035] S4. All ratio curves are placed in the same coordinate system to form a full-channel ratio change curve diagram, such as Figure 4 As shown, according to the change trend of the curve in the full channel ratio change curve diagram, it is judged whether the metal specimen to be tested has internal defects or external defects.

[0036] In S4, judging whether the metal specimen to be tested has internal defects or external defects according to the change trend of the curve in the full channel ratio change curve diagram includes: S401, dividing all ratio curves in the full-channel ratio change curve diagram into three stages according to time periods, wherein the time section of the first stage is 0-0.005s, the time section of the second stage is 0.005s-0.02s; and the time section of the third stage is after 0.02s; S402. Analyze the change trends of all ratio curves in the second stage. When the ratio curves of different channels have no intersection in the second stage, it is judged as an external surface corrosion defect. When the ratio curves of different channels intersect in the second stage and the curve amplitude reverses in size, it is judged as an internal surface corrosion defect.

[0037] The first stage (signal rapid decay stage): the signal shows rapid rise and decay, the time section is 0~0.005s; the second stage (eddy current expansion transition stage): the signal gradually spreads and tends to be stable, the time section is 0.005s~0.02s; the third stage (steady-state expansion stage): as the eddy current diffuses in the material to reach a stable state, the time section is the time period after 0.02s, such as Figure 4 shown.

[0038] Pick Figure 4 The second stage curve in the analysis is shown in the local enlarged figure. Figure 5 As shown in the figure, it can be seen that the ratio curves of each channel at this stage have no intersection with each other, and this feature is used as the basis for judging the corrosion defects of the external surface.

[0039] Embodiment 3: Different from the above embodiments, this embodiment detects metal specimens with internal defects.

[0040] Place the pulsed eddy current device above the inner surface corrosion defect area of ​​the test piece, and pass a 2Hz low-frequency square wave current into the excitation coil 1. Record the signal received by the TMR sensor of each channel and convert it into a voltage signal as the detection signal U y .

[0041] The ratio of the detection signal of each channel to the corresponding reference signal is calculated respectively, and the formula is: in: is the ratio calculated for the i-th TMR channel; is the detection signal received by the i-th TMR channel above the corrosion defect area in the specimen; is the reference signal received by the i-th TMR channel above the intact area of ​​the specimen.

[0042] Since the excitation coil 1 is circular, the TMR sensor 2 is arranged linearly, and the line perpendicular to the diameter of the TMR sensor 2 is used as the dividing line, the structures on both sides are symmetrical, so the detection data obtained by the TMR sensors on both sides are the same. Therefore, only the detection data on one side needs to be analyzed. The selected TMR sensors are the first TMR sensor 2-1, the second TMR sensor 2-2 and the third TMR sensor 2-3.

[0043] Furthermore, the obtained ratio curve is divided into time periods. The first stage (signal rapid decay stage): the signal shows rapid rise and decay, and the time period is 0~0.005s; the second stage (eddy current expansion transition stage): the signal gradually spreads and tends to be stable, and the time period is 0.005s~0.02s; the third stage (steady-state expansion stage): as the eddy current diffuses in the material and reaches a stable state, the time period is after 0.02s, such as Figure 6 shown.

[0044] Pick Figure 6 The second stage curve in the analysis is shown in the local enlarged figure. Figure 7 As shown. It can be seen that the ratio curves of each channel intersect at this stage, and the curve amplitude is reversed. This feature is used as the basis for judging the corrosion defects of the inner surface.

[0045] In the actual metal equipment corrosion defect detection process, the second stage curve of the ratio curve calculated according to the steps of the present invention is analyzed. When the ratio curves of each channel have no intersection with each other, it can be judged as an external surface corrosion defect; when the ratio curves of each channel intersect and the curve amplitude is reversed, it can be judged as an internal surface corrosion defect.

[0046] Obviously, the above embodiments are only examples for clear explanation, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from them are still within the protection scope of the invention.

Claims

1. A pulsed eddy current detection method for distinguishing corrosion defects on the inner and outer surfaces of metals, characterized by: The steps include: S1. Place the excitation coil above the non-destructive metal specimen to be tested, and record the detection signal of the TMR sensor of each channel as the reference signal; S2, placing the excitation coil above the metal specimen to be tested, and recording the detection signal of the TMR sensor of each channel as the detection signal; S3, the detection signal of each channel is respectively compared with the corresponding reference signal to generate a ratio curve of each channel; S4. All ratio curves are placed in the same coordinate system to form a full-channel ratio change curve diagram, and whether the metal specimen to be tested has internal defects or external defects is determined based on the change trend of the curves in the full-channel ratio change curve diagram.

2. The pulsed eddy current detection method for distinguishing corrosion defects on the inner and outer surfaces of metals according to claim 1 is characterized in that In S4, judging whether the metal specimen to be tested has internal defects or external defects according to the change trend of the curve in the full channel ratio change curve diagram includes: S401, dividing all ratio curves in the full-channel ratio change curve diagram into three stages according to time periods, wherein the time section of the first stage is 0-0.005s, the time section of the second stage is 0.005s-0.02s; and the time section of the third stage is after 0.02s; S402. Analyze the change trends of all ratio curves in the second stage. When the ratio curves of different channels have no intersection in the second stage, it is judged as an external surface corrosion defect. When the ratio curves of different channels intersect in the second stage and the curve amplitude reverses in size, it is judged as an internal surface corrosion defect.

3. A pulsed eddy current device for distinguishing corrosion defects on the inner and outer surfaces of metals, characterized in that: The steps for implementing the pulsed eddy current detection method for distinguishing corrosion defects on the inner and outer surfaces of metals as described in any one of claims 1 to 2 above include a detection module and an analysis module, wherein the detection module includes a shell and an excitation coil and a multi-channel TMR sensor arranged inside the shell; The excitation coil is parallel to the tested object and sends pulse excitation to the tested object; The multi-channel TMR sensor is used to receive the magnetic field detection signal parallel to the axis direction of the excitation coil fed back by the tested piece; The analysis module is used to receive the detection signal of the multi-channel TMR sensor, and to generate a ratio curve for each channel by comparing the received detection signal of each channel with the corresponding reference signal; all the ratio curves are placed in the same coordinate system to form a full-channel ratio change curve diagram, and to judge whether the metal specimen to be tested has internal defects or external defects according to the change trend of the curves in the full-channel ratio change curve diagram.

4. The pulse eddy current device for distinguishing corrosion defects on the inner and outer surfaces of metals according to claim 3, characterized in that: The multi-channel TMR sensor is composed of a plurality of identical TMR sensors arranged in a linear array, and a line perpendicular to the diameter of the TMR sensor arrangement is used as a dividing line. The structures on both sides are symmetrical, ensuring that the detection data obtained by the TMR sensors on both sides are the same.

5. The pulse eddy current device for distinguishing corrosion defects on the inner and outer surfaces of metals according to claim 4, characterized in that: In the multi-channel TMR sensor, a TMR sensor is arranged at the center of the two coils, and the other TMR sensors are evenly spaced along the diameter direction of the excitation coil, and the TMR sensor at the outermost edge is located at the outer edge of the excitation coil.

6. The pulsed eddy current device for distinguishing corrosion defects on the inner and outer surfaces of metals according to claim 5, characterized in that: The uniform interval is calculated according to the following formula: The center-to-center spacing ΔS of the TMR sensor is: ΔS= D / ( N-1); Wherein, D is the diameter of the excitation coil, N is the number of TMR sensor excitations, and N is not less than 5.

7. The pulsed eddy current device for distinguishing corrosion defects on the inner and outer surfaces of metals according to claim 3, characterized in that: When obtaining the reference signal or detection signal, a low-frequency square wave current of 2 Hz is passed through the excitation coil, and the signal received by the TMR sensor of each channel is recorded and converted into a voltage signal, and the voltage signal is recorded as the reference signal U0 or the detection signal.

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