Nondestructive magnetic flaw detection device and method

Abstract

The lossless magnetic flaw detection device comprises a magnet yoke, an alternating current power supply and a control host, the alternating current power supply provides a power supply for the magnet yoke, the lossless magnetic flaw detection device further comprises a detector, the detector comprises a shell, a shielding layer is arranged in the shell, a protective sleeve and a cable connector are communicated with the shell, a partition plate is arranged in the shell, a supporting pipe is arranged on the partition plate, and the supporting pipe is connected with the control host. Through holes are formed in the partition plate and the shell, a soft magnetic probe and a phase-locked amplification circuit board are arranged in the shell, the lower end of the soft magnetic probe penetrates through the through holes in the supporting pipe, the partition plate and the shell, the upper end of the soft magnetic probe is connected with the shielding layer through a spring, the soft magnetic probe is sleeved with a detection coil, and the input side of the phase-locked amplification circuit board is connected with the detection coil. The output side of the phase-locked amplification circuit board is connected with an alternating-current power supply and a control host through two signal lines arranged in the cable connector, and the control host is connected with the alternating-current power supply through a control line. According to the invention, rapid, sensitive, convenient and nondestructive detection of cracks and defects on the surface layer and near surface layer of the metal material can be realized.

Description

Technical Field

[0001] The invention belongs to the field of magnetic flaw detection equipment, and in particular relates to a non-destructive magnetic flaw detection device and method. Background Art

[0002] In the field of industrial production and equipment maintenance, the widespread application of metal materials is crucial. However, during long-term service, metal materials are easily cracked due to various factors such as temperature changes, stress, and material defects. Metal cracks, as common material defects, will significantly reduce the toughness and strength of the material. If not discovered and handled in time, the continued development of cracks may cause metal fractures, leading to serious safety accidents and posing a huge threat to production safety. Therefore, accurate detection of metal cracks has become a key task in special equipment inspection, which is of great significance to ensuring production order and safety.

[0003] At present, there are various methods for metal flaw detection. Magnetic flaw detection is widely used in the inspection of metal components such as large pressure tanks, ships, special vehicles, and pressure pipelines because of its portable equipment, simple operation, and strong visibility. Among them, magnetic particle flaw detection is a common magnetic flaw detection method. It sprays nano magnetic powder or magnetic powder suspension on the surface of the workpiece to be tested after cleaning, and then uses a magnetic yoke to magnetize the workpiece. The cracks on the surface of the workpiece generate a leakage magnetic field due to magnetization, which attracts magnetic powder and thus shows the size and direction of the cracks. Sometimes technicians use fluorescent magnetic powder and observe in a darkroom to improve the detection sensitivity. However, magnetic particle flaw detection has obvious defects. It is highly dependent on optical visual detection and has strict requirements on the optical background of the detection environment and the vision and experience of the inspectors. Moreover, the adhesion of magnetic powder on the surface of the workpiece is unstable, and the adhesion on the vertical surface or the inner top surface is weak, which seriously affects the detection sensitivity and is difficult to meet the needs of high-precision flaw detection of metal materials. Summary of the invention

[0004] The purpose of the present invention is to provide a nondestructive magnetic flaw detection device and method to solve the problems that the existing magnetic particle flaw detection relies on optical detection, is greatly affected by the environment, and has limited sensitivity, so as to realize rapid, sensitive, and convenient nondestructive detection of surface and near-surface cracks of metal materials.

[0005] In order to solve the above problems, the technical solution of the present invention is: A nondestructive magnetic flaw detection device comprises a magnetic yoke, an AC power supply and a control host, wherein the AC power supply provides power for the magnetic yoke, and further comprises a detector, wherein the detector comprises a shell, a shielding layer is arranged in the shell, a sheath tube and a cable connector are connected to the shell, a partition is arranged in the shell, a support tube is arranged on the partition, through holes are opened on the partition and the shell, a soft magnetic probe and a phase-locked amplifier circuit board are arranged in the shell, the lower end of the soft magnetic probe passes through the support tube and the partition and the through hole on the shell, the upper end of the soft magnetic probe is connected to the shielding layer through a spring, a detection coil is arranged on the outer sleeve of the soft magnetic probe, the input side of the phase-locked amplifier circuit board is connected to the detection coil, the output side of the phase-locked amplifier circuit board is respectively connected to the AC power supply and the control host through two signal lines arranged in the cable connector, and the control host is connected to the AC power supply through a control line.

[0006] A method for nondestructive magnetic flaw detection device, comprising the following steps: S1: Liquid nitrogen is poured into the shell through the sheath tube to provide an ultra-low temperature environment for the detection coil; S2: The control host controls the AC power supply to start, so that the magnetic yoke is energized, and the AC frequency is set to w0 and the phase is f0; the AC power supply reference channel is turned on, and the reference signal with the same frequency and phase as the excitation current is transmitted to the phase-locked amplifier circuit board through the signal line as the reference signal input; S3: Place the yoke on the surface of the workpiece to be tested. Under the excitation of the excitation AC power signal, the yoke generates an alternating magnetic field through the yoke coil. The magnetic field is transmitted to the yoke support leg through the magnetic circuit of the yoke handle and enters the inside of the workpiece to be tested, magnetizing the workpiece. S4: Place the shell on the surface of the workpiece and move the shell so that the tip of the soft magnetic probe sweeps across the surface to be tested. The alternating magnetic field excited by the yoke support leg propagates in the workpiece to be tested and leaks at the crack of the workpiece. The leakage magnetic field is transmitted by the soft magnetic probe to the center of the detection coil. At this time, a weak induced current signal will be induced in the detection coil. The induced current signal is transmitted to the phase-locked amplifier circuit board through the signal line, and after phase discrimination and amplification with the reference signal, it is transmitted back to the control host. S5: When the control host receives the current signal sent back by the phase-locked amplifier, it proves that there is a crack or defect in the workpiece. Through two-dimensional surface step scanning, the crack defect information on the workpiece surface can be reconstructed.

[0007] The beneficial effects of the present invention are: 1. Strong environmental adaptability: The present invention gets rid of the dependence on optical visual detection and does not need to consider the interference of ambient light background. It can stably and reliably carry out detection work in strong light, weak light or complex lighting environment, which greatly expands the application scenarios of detection and can be applied to any optical background occasions.

[0008] 2. High detection sensitivity: The phase-locked amplification detection technology of the detected signal and the excitation signal can accurately capture extremely weak magnetic leakage signals. Even extremely small cracks and defects on the surface and near the surface of metal materials can be clearly detected. Compared with traditional magnetic particle inspection, the detection sensitivity has been qualitatively improved.

[0009] 3. Strong anti-interference ability: By locking the magnetic field phase-locked frequency, the interference of other frequency magnetic fields (such as static magnetic fields) on the detection signal can be effectively avoided. This makes the detection process more stable, the detection results more reliable, greatly reduces the false detection rate, and ensures that the detection results truly reflect the actual condition of the metal material.

[0010] 4. Convenient and efficient operation: The entire flaw detection device has a reasonable structural design and a simple operation process. The control host can easily control the AC power supply and the magnetic yoke, and the detector can move flexibly. With the two-dimensional surface step scanning, it can quickly reconstruct the surface crack defect information of the workpiece, realize the rapid detection of metal materials, improve the detection efficiency, and meet the efficient flaw detection needs in actual production. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention will be further described below in conjunction with the accompanying drawings: Figure 1 It is a connection schematic diagram of the present invention; Figure 2 It is a structural schematic diagram of the present invention; Figure 3 It is a schematic diagram of the present invention regarding the magnetization of a workpiece by an AC yoke; Figure 4 It is a schematic diagram of the soft magnetic probe conducting AC leakage magnetic field of the present invention; Figure 5 The present invention relates to a block diagram of a phase-locked amplifier circuit board.

[0012] In the figure: control host 100, control line 101, AC power supply 200, yoke 300, yoke support foot 301, yoke handle 302, detector 400, signal line 401, cable connector 402, phase-locked amplifier circuit board 404, soft magnetic probe 405, detection coil 406, support tube 407, partition 408, thermocouple thermometer 409, sheath tube 410, shielding layer 411, thermal insulation layer 412, shell 413, workpiece 500, crack 501, leakage magnetic field 600, reference end 701, reference signal 702, phase sensitive detection PSD703, low pass filter LPF704, output signal 705, output end 706, signal end 707, detection signal 708. DETAILED DESCRIPTION

[0013] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] like Figure 1 and 2 As shown, a nondestructive magnetic flaw detection device includes a yoke 300, an AC power supply 200 and a control host 100, wherein the AC power supply 200 is connected to the yoke 300 through a wire to supply power to the yoke 300, and further includes a detector 400, wherein the detector 400 includes a shell 413, a shielding layer 411 is provided in the shell 413, a sheath tube 410 and a cable connector 402 are connected to the shell 413, a partition 408 is provided in the shell 413, a support tube 407 is provided on the partition 408, through holes are provided on the partition 408 and the shell 413, and a soft magnetic detection device is provided in the shell 413. Needle 405 and phase-locked amplifier circuit board 404, the lower end of the soft magnetic probe 405 passes through the support tube and the partition 408 and the through hole on the shell 413, the upper end of the soft magnetic probe 405 is connected to the shielding layer through the spring 403, and a detection coil 406 is arranged on the outer sleeve of the soft magnetic probe 405. The input side of the phase-locked amplifier circuit board 404 is connected to the detection coil 406, and the output side of the phase-locked amplifier circuit board 404 is respectively connected to the AC power supply 200 and the control host 100 through two signal lines 401 arranged in the cable connector 402, and the control host 100 is connected to the AC power supply 200 through the control line 101.

[0015] An IBM laptop is selected as the control host 100, a Jishili AS1000 single-phase power supply is selected as the AC power supply 200, and a Magnaflux yoke 300 is selected as the AC yoke 300.

[0016] Furthermore, a heat-insulating layer 412 is provided between the shielding layer 411 and the inner wall of the shell 413. The heat-insulating layer 412 has a thermal conductivity λ<0.05W / (m*K). The heat-insulating layer 412 is made of, for example, foamed polyurethane and has a thickness of 5-10 mm. After liquid nitrogen is poured into the detector, the heat-insulating layer 412 can prolong the retention time of the liquid nitrogen and reduce the volatilization rate of the liquid nitrogen, thereby maintaining the low-temperature environment inside the detector, while improving the safety of the equipment and ensuring the safety of the operator during use.

[0017] Furthermore, a thermocouple thermometer 409 is installed in the sheath tube 410, and a perforated pipe cover is threadedly connected to the sheath tube 410. The thermocouple thermometer 409 passes through the hole on the pipe cover. The sheath tube 410 is sealed by the pipe cover to prevent liquid nitrogen cold air from escaping, so that the shell 413 can maintain a low temperature for a longer time, for example, below -100°C. The temperature in the shell 413 is monitored in real time by the thermocouple thermometer 409. When it is observed that the temperature is lower than the preset value, the flaw detection is stopped.

[0018] Furthermore, the housing 413 is made of non-magnetic material, such as polyvinyl chloride. The housing made of non-magnetic material can ensure that the housing does not interfere with the magnetic field, thereby ensuring the purity and accuracy of the detection signal. This avoids interference caused by magnetic materials, ensures that the device can detect tiny cracks and defects, and improves the reliability and accuracy of detection.

[0019] Furthermore, the shielding layer 411 is made of a high magnetic permeability material, with a relative magnetic permeability greater than 20,000, such as a multilayer Permalloy. Electromagnetic shielding is used to optimize the quality and stability of the detection signal, and to improve the sensitivity and accuracy of the detection. In addition, the shielding layer can also prevent signal leakage, protect internal components, and ensure the reliability and stability of the device in complex environments.

[0020] Furthermore, the inner diameter of the detection coil 406 is less than 1.5 times the diameter of the soft magnetic probe 405. The detection coil 406 is, for example, a coil made of metal platinum wire, and the number of turns of the coil is 1000.

[0021] Furthermore, the spring 403 is made of non-magnetic material with a stiffness coefficient of 10 N / cm. The spring 403 moves in the vertical direction under the external stress. The spring 403 can play a supporting and buffering role, ensuring that the soft magnetic probe can flexibly and stably contact the surface of the workpiece, while reducing the impact of vibration and impact on the detection process. The design of the spring 403 not only improves the sensitivity and reliability of the detection, but also protects the probe and equipment and prolongs the service life.

[0022] Furthermore, the cable connector 402 is a waterproof cable connector 402. The waterproof cable connector 402 is used to seal the signal line, reduce the loss of liquid nitrogen cooling air, and prevent condensed water outside the housing from penetrating into the housing to avoid short circuit or damage to electronic components.

[0023] Furthermore, the soft magnetic probe 405 is made of soft magnetic material, and the coercive force H c <10A / m.

[0024] A method for nondestructive magnetic flaw detection device, such as Figures 1 to 5 As shown, the following steps are included: S1: Liquid nitrogen is poured into the housing 413 through the sheath tube 410 to provide an ultra-low temperature environment for the detection coil 406, for example, below -100°C, and then a thermocouple thermometer 409 is installed on the sheath tube 410; The purpose of pouring liquid nitrogen into the shell is to: A. Improve detection sensitivity: In a low temperature environment, the resistance of the detection coil 406 will be significantly reduced. According to Ohm's law, the reduction in resistance can reduce the energy loss during signal transmission, thereby improving the strength and quality of the signal. A low temperature environment can also suppress thermal noise. Thermal noise is caused by the thermal motion of electrons. The lower the temperature, the smaller the thermal noise. By lowering the temperature, the interference of background noise can be reduced, so that weak leakage magnetic signals can be detected more clearly and the sensitivity of detection can be improved.

[0025] B. Enhance the performance of the soft magnetic probe 405: Soft magnetic materials generally have better magnetic properties at low temperatures, such as higher magnetic permeability and lower coercive force. These properties enable the soft magnetic probe 405 to more effectively sense and conduct leakage magnetic fields in a low temperature environment, thereby improving the accuracy and reliability of detection. A low temperature environment can reduce the hysteresis loss of the soft magnetic probe 405, making it respond faster in an alternating magnetic field, further improving detection efficiency.

[0026] C. Achieve high-precision detection: The purpose of this patent is to detect tiny cracks and defects on the surface and near the surface of metal materials. The leakage magnetic field signals caused by these defects are usually very weak and require a highly sensitive detection system to detect. The detection coil and soft magnetic probe in a low-temperature environment can better capture these weak signals, thereby achieving high-precision non-destructive testing.

[0027] D. Reduce the false detection rate: By lowering the temperature, reducing background noise and other interference signals, the leakage magnetic signal related to cracks or defects can be locked more accurately. This helps to improve the signal-to-noise ratio of detection, thereby reducing the false detection rate and ensuring the reliability of the detection results.

[0028] S2: The control host 100 controls the AC power supply 200 to start, so that the magnetic yoke 300 is powered, and the AC frequency is set to w0 and the phase is f0; the reference channel of the AC power supply 200 is turned on, and the reference signal with the same frequency and phase as the excitation current is transmitted to the phase-locked amplifier circuit board 404 via the signal line as the reference signal input; S3: placing the yoke 300 on the surface of the workpiece 500 to be measured. Under the excitation of the signal of the excitation AC power supply 200, the yoke 300 generates an alternating magnetic field through the coil of the yoke 300. The magnetic field is transmitted to the yoke support leg 301 through the handle magnetic circuit of the yoke 300 and enters the interior of the workpiece 500 to be measured, and magnetizes the workpiece 500. S4: Place the shell 413 on the surface of the workpiece 500, and move the shell 413 so that the tip of the soft magnetic probe 405 sweeps across the surface to be measured. The alternating magnetic field excited by the yoke support leg 301 propagates in the workpiece 500 to be measured, and leaks at the crack 501 of the workpiece 500. The leakage magnetic field 600 is transmitted by the soft magnetic probe 405 to the center of the detection coil. At this time, a weak induced current signal will be induced in the detection coil. The induced current signal is transmitted to the phase-locked amplifier circuit board 404 through the signal line, and after phase discrimination and amplification operations with the reference signal, it is transmitted back to the control host 100. In this example, if Figure 5 As shown, it is assumed that the reference signal 702 input to the phase-locked amplifier circuit board 404 is I r =I r0 cos(ω0t+Φ0) is input from the reference terminal 701, and the coil detection signal 708 is: t =I t0 cos(ω0t+Φ0)+B, where B is noise, is input from the signal terminal 707, and the output signal 705 after the phase-sensitive detection PSD703 and the low-pass filter LPF704 is: out =0.5*(I r0 I t0 ) is a DC signal, which is transmitted back from the output terminal 706 to the control host 100.

[0029] S5: When the control host 100 receives the current signal sent back by the phase-locked amplifier, it proves that there is a crack 501 or defect in the workpiece 500. Through two-dimensional surface step scanning, the defect information of the crack 501 on the surface of the workpiece 500 can be reconstructed.

[0030] The contents described in the embodiments of this specification are merely an enumeration of the implementation forms of the inventive concept. The protection scope of the present invention should not be regarded as limited to the specific forms described in the embodiments. The protection scope of the present invention also extends to equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

Claims

1. A nondestructive magnetic flaw detection device, comprising a magnetic yoke, an AC power supply and a control host, wherein the AC power supply supplies power to the magnetic yoke, and is characterized in that: It also includes a detector, which includes a shell, a shielding layer is arranged in the shell, a sheath tube and a cable connector are connected to the shell, a partition is arranged in the shell, a support tube is arranged on the partition, through holes are opened on the partition and the shell, a soft magnetic probe and a phase-locked amplifier circuit board are arranged in the shell, the lower end of the soft magnetic probe passes through the support tube and the partition and the through hole on the shell, the upper end of the soft magnetic probe is connected to the shielding layer through a spring, a detection coil is arranged on the outer sleeve of the soft magnetic probe, the input side of the phase-locked amplifier circuit board is connected to the detection coil, and the output side of the phase-locked amplifier circuit board is respectively connected to the AC power supply and the control host through two signal lines arranged in the cable connector, and the control host is connected to the AC power supply through a control line.

2. A nondestructive magnetic flaw detection device according to claim 1, characterized in that: A heat preservation and insulation layer is arranged between the shielding layer and the inner wall of the shell, and the heat preservation and insulation layer has a thermal conductivity coefficient λ<0.05W / (m*K).

3. A nondestructive magnetic flaw detection device according to claim 1, characterized in that: A thermocouple thermometer is installed in the sheath tube.

4. A nondestructive magnetic flaw detection device according to claim 1, characterized in that: The shell is made of non-magnetic material.

5. A nondestructive magnetic flaw detection device according to claim 1, characterized in that: The shielding layer is made of high magnetic permeability material, and the relative magnetic permeability is greater than 20,000.

6. A nondestructive magnetic flaw detection device according to claim 1, characterized in that: The inner diameter of the detection coil is less than 1.5 times the diameter of the soft magnetic probe.

7. A nondestructive magnetic flaw detection device according to claim 1, characterized in that: The spring is made of non-magnetic material.

8. A nondestructive magnetic flaw detection device according to claim 1, characterized in that: The cable connector is a waterproof cable connector.

9. A nondestructive magnetic flaw detection device according to claim 1, characterized in that: The soft magnetic probe is made of soft magnetic material, with a coercive force H c <10A / m.

10. A method of using the nondestructive magnetic flaw detection device according to any one of claims 1 to 9, characterized in that: The steps include: S1: Liquid nitrogen is poured into the shell through the sheath tube; S2: The control host controls the AC power supply to start, so that the magnetic yoke is energized, and the AC frequency is set to w0 and the phase is f0; the AC power supply reference channel is turned on, and the reference signal with the same frequency and phase as the excitation current is transmitted to the phase-locked amplifier circuit board through the signal line as the reference signal input; S3: Place the yoke on the surface of the workpiece to be measured. Under the excitation of the excitation AC power supply signal, the yoke generates an alternating magnetic field through the yoke coil. The magnetic field is transmitted to the yoke support leg through the magnetic circuit of the yoke handle and enters the inside of the workpiece to be measured to magnetize the workpiece. S4: Place the shell on the surface of the workpiece and move the shell so that the tip of the soft magnetic probe sweeps across the surface to be tested. The alternating magnetic field excited by the yoke support leg propagates in the workpiece to be tested and leaks at the crack of the workpiece. The leakage magnetic field is transmitted by the soft magnetic probe to the center of the detection coil. At this time, a weak induced current signal will be induced in the detection coil. The induced current signal is transmitted to the phase-locked amplifier circuit board through the signal line, and after phase discrimination and amplification with the reference signal, it is transmitted back to the control host. S5: When the control host receives the current signal sent back by the phase-locked amplifier, it proves that there is a crack or defect in the workpiece. Through two-dimensional surface step scanning, the crack defect information on the workpiece surface can be reconstructed.

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