Electromagnetic dual-mode detection device and method for metal internal and external defects

Abstract

The present invention provides an electromagnetic dual-mode detection device and method for internal and external defects of metal, the device includes a shell; an AC electromagnetic field excitation unit, fixed inside the shell; a pulse eddy current excitation unit, fixed at the bottom of the AC electromagnetic field excitation unit; the detection unit includes a plurality of detection modules wound with horizontal detection coils and vertical detection coils. The detection method includes enabling the plurality of detection modules to generate an amplitude image of a crack defect when the AC electromagnetic field excitation unit generates a surface eddy current on the surface of the metal specimen to be tested; when the pulse eddy current excitation unit generates a continuously decaying eddy current inside the metal specimen to be tested, the detection signal attenuation rate of the calibration position and the detection position is compared, so as to realize the detection of corrosion defects on the inner surface of the metal specimen to be tested, thereby realizing the detection of internal and external defects of the metal specimen to be tested, and reducing the detection cost and improving the detection efficiency compared with the existing non-destructive detection method.

Description

Technical Field

[0001] The invention relates to an electromagnetic dual-mode detection device and method for metal internal and external defects, belonging to the technical field of metal nondestructive detection. Background Art

[0002] Metals and alloy materials such as carbon steel, stainless steel, copper, and aluminum are widely used in the manufacture of special equipment to support the stable operation of the equipment under extreme conditions such as high temperature, high pressure, low temperature, and fatigue. Usually, the working environment of special equipment is relatively harsh. Under the combined effects of the external environment and internal media, cracks, corrosion, and thinning will form on the outer and inner walls of the equipment. These defects will gradually expand during the operation of the equipment, eventually causing the equipment to fail.

[0003] For the detection of crack defects on the outer wall of the equipment, the alternating current field measurement testing (ACFM) technology can be used. This technology excites the sensor to form a uniform induced current on the surface of the test piece, and the distorted magnetic field caused by the crack defect is detected to achieve the quantification of the defect. For the detection of corrosion thinning defects inside the equipment, the pulsed eddy current testing (PECT) technology can be used. This technology applies a pulsed square wave excitation to the coil to induce a continuously decaying eddy current in the test piece, and the wall thickness of the test piece is quantified by detecting the decay of the eddy current.

[0004] At present, the detection of surface defects on the inner and outer walls of equipment requires two detection technologies to work independently, and the two detection technologies correspond to different detection equipment, which makes the detection process time-consuming and labor-intensive, the detection cycle is long, and the detection efficiency is low. Therefore, it is necessary to invent a dual-mode probe and detection method, so that one probe has the detection functions of both PECT technology and ACFM technology, thereby realizing the simultaneous detection of defects on the outer and inner walls of the equipment and improving the detection efficiency. Summary of the invention

[0005] In order to solve the problems existing in the above-mentioned prior art, the present invention proposes an electromagnetic dual-mode detection device and method for internal and external defects of metals, which can realize simultaneous detection of defects on the outer and inner walls of equipment and improve detection efficiency.

[0006] In order to achieve the above object, the present invention provides an electromagnetic dual-mode detection device for metal internal and external defects, comprising:

[0007] case;

[0008] An AC electromagnetic field excitation unit is fixed inside the housing and is used to generate surface eddy currents on the surface of the metal specimen to be tested, wherein the scanning direction along the metal specimen to be tested is the X direction, the direction perpendicular to the scanning direction is the Y direction, and the direction perpendicular to the scanning surface is the Z direction;

[0009] The pulse eddy current excitation unit is fixed to the bottom of the AC electromagnetic field excitation unit and is used to generate attenuated eddy currents inside the metal specimen to be tested;

[0010] The detection unit includes a plurality of detection modules wound with horizontal detection coils and vertical detection coils, which are fixed to the bottom of the shell, wherein the horizontal detection coils are used to sense the distorted magnetic field generated by the surface eddy current in the Z direction and the attenuated magnetic field generated by the attenuated eddy current; and the vertical detection coils are used to sense the distorted magnetic field generated by the surface eddy current in the X direction.

[0011] Furthermore, the AC electromagnetic field excitation unit includes a first excitation coil and a U-shaped frame running through the first excitation coil.

[0012] Furthermore, the pulse eddy current excitation unit includes a second excitation coil, and the second excitation coil is fixed to the bottom of the U-shaped frame.

[0013] Furthermore, the plurality of detection modules are arranged in an array, and the detection modules include a cross frame, a horizontal detection coil horizontally wound around the cross frame, and a vertical detection coil vertically wound around the cross frame.

[0014] In a second aspect, the present invention further provides an electromagnetic dual-mode detection method for metal internal and external defects, using the electromagnetic dual-mode detection device for metal defects provided above, comprising:

[0015] Place the electromagnetic dual-mode detection device on the surface of the metal specimen to be tested, and establish a rectangular coordinate system about the metal specimen to be tested; wherein the scanning direction along the surface of the metal specimen to be tested is the X direction, the direction perpendicular to the scanning direction is the Y direction, and the direction perpendicular to the scanning surface is the Z direction;

[0016] Exciting the AC electromagnetic field excitation unit to generate surface eddy currents and obtain the magnetic field amplitudes in the X and Z directions;

[0017] Exciting a pulsed eddy current excitation unit to generate a decaying eddy current and obtain a decaying eddy current signal;

[0018] The surface crack defects of the metal specimen to be tested are detected according to the magnetic field amplitudes in the X direction and the Z direction, and the inner surface corrosion defects of the metal specimen to be tested are detected according to the attenuated magnetic field signal.

[0019] Furthermore, the magnetic field amplitudes in the X direction and the Z direction are obtained, specifically including:

[0020] Dividing the detection unit into a first detection sub-unit and a second detection sub-unit in the Y direction;

[0021] Extracting a first group of X-direction magnetic field amplitudes and a first group of Z-direction magnetic field amplitudes detected by the first detection subunit;

[0022] Draw a first annular butterfly diagram using a first set of X-direction magnetic field amplitudes and a first set of Z-direction magnetic field amplitudes;

[0023] Extracting a second group of X-direction magnetic field amplitudes and a second group of Z-direction magnetic field amplitudes detected by the second detection subunit;

[0024] A second annular butterfly diagram is drawn with a second set of X-direction magnetic field amplitudes and a second set of Z-direction magnetic field amplitudes.

[0025] Further, detecting the corrosion defects of the metal specimen to be tested according to the attenuated voltage signal specifically includes:

[0026] Using the attenuated magnetic field signal to obtain the baseline attenuation rate in the corrosion-free area;

[0027] Sequentially using the first detection subunit and the second detection subunit to obtain a first set of detection attenuation rates and a second set of detection attenuation rates obtained when the attenuated magnetic field signal is applied to the corrosion area;

[0028] The wall thickness of the corroded area is calculated according to the baseline attenuation rate, the first group of detection attenuation rates and the second group of detection attenuation rates.

[0029] By adopting the above technical scheme, the present invention provides an electromagnetic dual-mode detection device and method for internal and external defects of metal, which enables multiple detection modules to generate amplitude images about crack defects when the AC electromagnetic field excitation unit generates surface eddy currents on the surface of the metal specimen to be tested; when the pulse eddy current excitation unit generates continuously attenuated eddy currents inside the metal specimen to be tested, the attenuation rates of the detection signals at the calibration position and the detection position are compared, so as to realize the detection of corrosion defects on the inner surface of the metal specimen to be tested, thereby realizing the detection of internal and external defects of the metal specimen to be tested. Compared with the existing non-destructive testing methods, the detection cost is reduced and the detection efficiency is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 An assembly diagram of an electromagnetic dual-mode detection device for metal defects provided by the present invention;

[0031] Figure 2 A schematic diagram of the structure of a U-shaped frame connected to an excitation coil in an electromagnetic dual-mode detection device for metal defects provided by the present invention;

[0032] Figure 3 A schematic diagram of the structure of a detection module in an electromagnetic dual-mode detection device for metal defects provided by the present invention;

[0033] Figure 4 A positional relationship diagram of an electromagnetic dual-mode detection device for metal defects provided by the present invention and a metal specimen to be tested;

[0034] Figure 5 A flow chart of an electromagnetic dual-mode detection method for metal defects provided by the present invention;

[0035] Figure 6 A flow chart of detecting crack defects in an electromagnetic dual-mode detection method for metal defects provided by the present invention;

[0036] Figure 7 A flow chart of detecting corrosion defects of a metal specimen to be tested in an electromagnetic dual-mode detection method for metal defects provided by the present invention.

[0037] In the figure: 1. Shell; 2. AC electromagnetic field excitation unit; 3. Pulse eddy current excitation unit; 4. Detection unit; 5. Horizontal detection coil; 6. Vertical detection coil; 7. Detection module; 8. First excitation coil; 9. U-shaped frame; 10. Second excitation coil; 11. First joint; 12. Second joint; 13. Third joint; 14. Cross frame. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below through the accompanying drawings and specific implementation methods. Usually, special equipment (metal equipment) is prone to defects such as cracks and corrosion when used for a long time, which affects the stable and safe operation of the special equipment. The existing detection requires the use of two different devices for inspection and detection of surface crack defects and internal corrosion defects. The detection efficiency is low and the detection cost is high. Therefore, an electromagnetic dual-mode detection device and method that is compatible with pulsed eddy current detection and AC electromagnetic field detection is needed to reduce the cost of detection.

[0039] Embodiment 1

[0040] like Figures 1 to 4 As shown, the present invention provides an electromagnetic dual-mode detection device for metal defects, comprising:

[0041] Shell 1; wherein the shell 1 is made of composite material to facilitate the fixation of the detection unit 4 and other devices;

[0042] The AC electromagnetic field excitation unit 2 is fixed inside the shell 1 and is used to generate surface eddy currents on the surface of the metal specimen to be tested, wherein the scanning direction along the metal specimen to be tested is the X direction, the direction perpendicular to the scanning direction is the Y direction, and the direction perpendicular to the scanning surface is the Z direction; the AC electromagnetic field excitation unit 2 is driven by a high-frequency sinusoidal current; wherein the AC electromagnetic field excitation unit 2 includes a first excitation coil 8 and a U-shaped skeleton 9 that penetrates the first excitation coil 8. The first excitation coil 8 includes but is not limited to a rectangular excitation coil structure, which is conducive to the penetration and fixation of the U-shaped skeleton 9, and the first excitation coil 8 is wound by enameled wire, and its wire diameter, number of turns and number of winding layers are determined according to the intensity of the surface eddy current and the detection sensitivity of the surface crack defects of the metal specimen to be tested.

[0043] The pulse eddy current excitation unit 3 is fixed at the bottom of the AC electromagnetic field excitation unit 2, and is used to generate attenuated eddy currents inside the metal specimen to be tested; the pulse eddy current excitation unit 3 is driven by a low-frequency square wave current, and the pulse eddy current excitation unit 3 includes a second excitation coil 10, and the second excitation coil 10 is fixed at the bottom of the U-shaped skeleton 9. And the second excitation coil 10 also adopts a rectangular excitation coil structure; in an optional embodiment, the second excitation coil 10 is wound at the bottom of the U-shaped skeleton 9, parallel to the top of the U-shaped skeleton 9, and the second excitation coil 10 is also wound by enameled wire, and its wire diameter, number of turns and number of winding layers are determined according to the intensity of the attenuated eddy current and the detection sensitivity of the internal defects of the metal specimen to be tested.

[0044] The detection unit 4 includes a plurality of detection modules 7 wound with horizontal detection coils 5 and vertical detection coils 6, which are fixed to the bottom of the shell 1, wherein the horizontal detection coil 5 is used to sense the distorted magnetic field generated by the surface eddy current in the Z direction and the attenuated magnetic field generated by the attenuated eddy current; the vertical detection coil 6 is used to sense the distorted magnetic field generated by the surface eddy current in the X direction. The horizontal detection coil 5 and the vertical detection coil 6 are wound with enameled wire, and the wire diameter, number of turns and number of winding layers are determined according to the detection sensitivity of surface crack defects and internal surface corrosion defects. The above detection unit 4 is inserted in the area surrounded by the pulsed eddy current excitation unit 3 and the U-shaped frame 9.

[0045] The plurality of detection modules 7 are arranged in a rectangular array, for example, in a 6×2 matrix, and each detection module 7 includes a cross frame 14, the horizontal detection coil 5 horizontally wound around the cross frame 14, and the vertical cross coil 6 vertically wound around the cross frame 14. The horizontal detection coil 5 is used to collect the induced magnetic field of the surface eddy current in the Z direction and the induced magnetic field generated by the decaying eddy current; the vertical detection coil 6 is used to collect the induced magnetic field in the X direction when the surface eddy current flows through the surface cracks of the equipment.

[0046] In addition, the detection device is also provided with a first joint 11 connected to the AC electromagnetic field excitation unit 2, a second joint 12 connected to the pulse eddy current excitation unit 3, and a third joint 13 connected to the detection unit 4. The first joint 11, the second joint 12, and the third joint 13 are respectively welded and fixed to the detection device by soldering. It should also be noted that the sensor is filled with thermal conductive glue to fix the AC electromagnetic field excitation unit 2, the pulse eddy current excitation unit 3, and the detection unit 4 respectively and to achieve the purpose of heat dissipation, and at the same time, the stability of the first joint 11, the second joint 12, and the third joint 13 can also be ensured.

[0047] An electromagnetic dual-mode detection device for metal defects provided by an embodiment of the present invention enables multiple detection modules to generate amplitude images of crack defects when an AC electromagnetic field excitation unit generates surface eddy currents on the surface of a metal specimen to be tested; when a pulsed eddy current excitation unit generates continuous attenuated eddy currents inside the metal specimen to be tested, the attenuation rates of the detection signals at the calibration position and the detection position are compared, thereby realizing the detection of corrosion defects on the inner surface of the metal specimen to be tested, and further realizing the detection of defects inside and outside the metal specimen to be tested. Compared with the existing non-destructive testing methods, the detection cost is reduced and the detection efficiency is improved.

[0048] Embodiment 2

[0049] The embodiment of the present invention provides a method for detecting internal and external defects of metal based on the first embodiment, and the device for detecting internal and external defects of metal provided by the above embodiment is applied, such as Figures 5 to 7 As shown, including:

[0050] S10: Place the detection device on the surface of the metal specimen to be tested, and establish a rectangular coordinate system about the metal specimen to be tested; wherein the scanning direction of the metal specimen to be tested is the X direction, the direction perpendicular to the scanning direction is the Y direction, and the direction perpendicular to the scanning surface is the Z direction; through the pulse / AC electromagnetic dual-mode method adopted by the above-mentioned detection device, place the detection device on the surface of the metal specimen to be tested, and use the above-mentioned detection probe to scan along the X direction.

[0051] S20: Excite the AC electromagnetic field excitation unit to generate surface eddy currents and obtain the magnetic field amplitudes in the X direction and the Z direction; specifically, by applying a sinusoidal current with a frequency of 10KHz at the first joint, an alternating magnetic field is generated at the first excitation coil, and then a surface eddy current is formed on the surface of the metal specimen to be tested; the surface eddy current generates an induced magnetic field in the X direction and the Z direction, and the amplitudes of the induced magnetic fields in the X direction and the Z direction are obtained according to the signal modulation; it should be noted here that when a crack is detected, the above amplitude will change, and the specific operations and results are as follows:

[0052] S21: dividing the detection unit into a first detection sub-unit and a second detection sub-unit in the Y direction; for example, the detection unit includes a 6×2 matrix of detection modules, and correspondingly each group of detection sub-units includes 6 detection modules;

[0053] S22: extracting the first X-direction magnetic field amplitude and the first Z-direction magnetic field amplitude detected by the first detection subunit; each detection module can perform detection separately, wherein the vertical detection coil in the detection module is used to obtain the amplitude of the induced magnetic field in the X direction; the horizontal detection coil is used to obtain the amplitude of the induced magnetic field in the Z direction; when there is no crack on the surface of the metal specimen to be tested, the amplitudes in the X direction and the Z direction measured by each detection module are respectively the same; when cracks appear on the surface of the metal specimen to be tested, the magnetic fields in the X direction and the Z direction are distorted, resulting in changes in the amplitudes of the induced magnetic fields in the X direction and the Z direction of the surface eddy current, and the first detection subunit (vertical detection coil) forms a first trough image in the X direction induced magnetic field signal Bx amplitude, and the first detection subunit (horizontal detection coil) Z direction induced magnetic field signal Bz forms a first peak-trough image obtained by the first detection subunit.

[0054] S23: drawing a first annular butterfly diagram using the first set of X-direction magnetic field amplitudes and the first set of Z-direction magnetic field amplitudes; the drawing method is to draw the annular butterfly diagram using the Bx magnetic field amplitude as the horizontal coordinate and the Bz magnetic field amplitude as the vertical coordinate;

[0055] S24: extracting the second X-direction magnetic field amplitude and the second Z-direction magnetic field amplitude detected by the second detection subunit;

[0056] S25: Draw a second annular butterfly diagram with the second set of X-direction magnetic field amplitudes and the second set of Z-direction magnetic field amplitudes. Steps S24 and S25 are the same as steps S22 and S23, and are not described here any more.

[0057] S30: Excite the pulse eddy current excitation unit to generate attenuated eddy current and obtain an attenuated voltage signal; specifically, apply a square wave current with a frequency of 2 Hz at the second joint, and when the signal jumps, the direction of the magnetic field of the second excitation coil changes, thereby generating continuous attenuated eddy currents inside the metal specimen to be tested; the attenuated eddy current generates a corresponding continuously attenuated voltage signal in the horizontal detection coil, and logarithmic analysis is used to determine whether the inner wall of the metal specimen to be tested is corroded and thinned.

[0058] S40: Detecting surface crack defects of the metal specimen to be tested according to the magnetic field amplitudes in the X direction and the Z direction, and detecting corrosion defects on the inner surface of the metal specimen to be tested according to the attenuated magnetic field signal. The detection of corrosion defects includes the following steps:

[0059] S41: Assume that the wall thickness of the corrosion-free area is h 0, using the attenuated magnetic field signal to obtain the baseline attenuation rate k in the non-corrosion area 0 ;

[0060] S42: sequentially using the first detection subunit and the second detection subunit to obtain the first group of detection attenuation rates and the second group of detection attenuation rates obtained when the attenuated magnetic field signal is applied to the corrosion area; wherein the detection signals in each horizontal detection coil in the six detection modules in the first detection subunit are calculated by linear fitting to obtain respective signal attenuation rates (the first group of detection attenuation rates), respectively: k 1-1 , k 1 - 2 , k 1 - 3 , k 1-4 , k 1-5 , k 1-6 Similarly, the detection signals in each horizontal detection coil in the detection module of the second detection subunit are calculated by linear fitting to obtain their respective signal attenuation rates (the second group of detection attenuation rates): k 2-1 , k 2 - 2 , k 2 - 3 , k 2-4 , k 2-5 , k 2-6 .

[0061] S43: Calculate the wall thickness of the corrosion area according to the reference attenuation rate, the first group of detection attenuation rates and the second group of detection attenuation rates. The wall thickness calculated by each detection module is obtained by the following formula:

[0062] (i=1, 2; j=1, 2, 3, 4, 5, 6)

[0063] After that, the average value is calculated separately, namely:

[0064] (i=1, 2; j=1, 2, 3, 4, 5, 6).

[0065] 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. An electromagnetic dual-mode detection device for metal internal and external defects, characterized in that: include: Housing (1); An alternating current electromagnetic field excitation unit (2) is fixed inside the housing (1) and is used to generate surface eddy currents on the surface of the metal specimen to be tested, wherein the scanning direction along the metal specimen to be tested is the X direction, the direction perpendicular to the scanning direction is the Y direction, and the direction perpendicular to the scanning surface is the Z direction; A pulsed eddy current excitation unit (3) is fixed to the bottom of the AC electromagnetic field excitation unit (2) and is used to generate a decaying eddy current inside the metal specimen to be tested; The detection unit (4) comprises a plurality of detection modules (7) wound with horizontal detection coils (5) and vertical detection coils (6), which are fixed to the bottom of the housing (1), wherein the horizontal detection coils (5) are used to sense the distorted magnetic field generated by the surface eddy current in the Z direction and the attenuated magnetic field generated by the attenuated eddy current; and the vertical detection coils (6) are used to sense the distorted magnetic field generated by the surface eddy current in the X direction.

2. The electromagnetic dual-mode detection device for metal internal and external defects according to claim 1, characterized in that: The AC electromagnetic field excitation unit (2) comprises a first excitation coil (8) and a U-shaped frame (9) penetrating the first excitation coil (8).

3. The electromagnetic dual-mode detection device for metal internal and external defects according to claim 2, characterized in that: The pulsed eddy current excitation unit (3) comprises a second excitation coil (10), wherein the second excitation coil (10) is fixed to the bottom of the U-shaped frame (9).

4. The electromagnetic dual-mode detection device for metal internal and external defects according to claim 1, characterized in that: The plurality of detection modules (7) are arranged in an array, the detection modules (7) comprising a cross frame (14), the horizontal detection coil (5) being horizontally wound around the cross frame (14), and the vertical detection coil (6) being vertically wound around the cross frame (14).

5. An electromagnetic dual-mode detection method for metal internal and external defects, applied to the electromagnetic dual-mode detection device for metal internal and external defects according to any one of claims 1 to 4, characterized in that: include: The electromagnetic dual-mode detection device is placed on the surface of the metal specimen to be tested, and a rectangular coordinate system is established about the metal specimen to be tested; wherein the scanning direction along the metal specimen to be tested is the X direction, the direction perpendicular to the scanning direction is the Y direction, and the direction perpendicular to the scanning surface is the Z direction; Exciting the AC electromagnetic field excitation unit to generate surface eddy currents and obtain the magnetic field amplitudes in the X direction and the Z direction; Exciting the pulse eddy current excitation unit to generate decaying eddy currents and obtain decaying magnetic fields; The surface crack defects of the metal specimen to be tested are detected according to the magnetic field amplitudes in the X direction and the Z direction, and the inner surface corrosion defects of the metal specimen to be tested are detected according to the attenuated magnetic field signal.

6. The electromagnetic dual-mode detection method for metal internal and external defects according to claim 5, characterized in that: The obtaining of the magnetic field amplitudes in the X direction and the Z direction specifically includes: Dividing the detection unit into a first detection sub-unit and a second detection sub-unit in the Y direction; Extracting a first group of X-direction magnetic field amplitudes and a first group of Z-direction magnetic field amplitudes detected by the first detection subunit; Draw a first annular butterfly diagram using the first group of X-direction magnetic field amplitudes and the first group of Z-direction magnetic field amplitudes; Extracting a second group of X-direction magnetic field amplitudes and a second group of Z-direction magnetic field amplitudes detected by the second detection subunit; A second annular butterfly diagram is drawn using the second set of X-direction magnetic field amplitudes and the second set of Z-direction magnetic field amplitudes.

7. The electromagnetic dual-mode detection method for metal internal and external defects according to claim 6, characterized in that: The detecting the inner surface corrosion defects of the metal specimen to be tested according to the attenuated magnetic field signal specifically includes: Using the attenuated magnetic field signal to obtain a reference attenuation rate in a corrosion-free area; sequentially using the first detection subunit and the second detection subunit to obtain a first group of detection attenuation rates and a second group of detection attenuation rates obtained when the attenuated magnetic field signal is applied to the corrosion area; The wall thickness of the corrosion area is calculated according to the reference attenuation rate, the first group of detection attenuation rates and the second group of detection attenuation rates.

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