Non-destructive testing method and system for magnetization direction of non-magnetized magnet

Abstract

The invention discloses a method and system for detecting the magnetization direction of an unmagnetized magnet, and belongs to the technical field of magnetic material detection. The method comprises the following steps: applying an external guide magnetic field to a to-be-detected non-magnetized magnet; detecting a signal related to the physical state of the non-magnetized magnet under the action of the guide magnetic field as a response signal; and judging the magnetization direction of the non-magnetized magnet based on the corresponding relation between the response signal and the preset magnetization direction. The corresponding system comprises a guide magnetic field generation unit, a detection unit and a discrimination unit. The modulation effect of magnetocrystalline anisotropy of a non-magnetized magnet on an external magnetic field is utilized, invisible magnetic domain orientation information is converted into externally observable physical field difference, efficient, visual and lossless recognition of the preset magnetization direction is achieved, and the method is suitable for production quality control of magnetic assemblies such as a Halbach magnetic circuit and the like.

Description

Technical Field

[0001] This invention relates to the field of magnetic material testing technology, specifically to a non-destructive testing method and system for the magnetization direction of an unmagnetized magnet, which is particularly suitable for determining the magnetization direction of complex magnetic components such as Heilbeck magnetic circuits. Background Technology

[0002] In the application of permanent magnet materials, especially in the manufacturing process of high-performance magnetic components (such as magnetic levitation components in Helbeck magnetic circuits) and the processing of anisotropic magnets such as sintered NdFeB magnets, the prediction and confirmation of the magnetization direction of the magnet before final magnetization is a critical quality control step, especially for unmagnetized magnets or magnets delivered without magnetization. Helbeck components are usually assembled from multiple magnets arranged in a specific magnetization direction. If the magnetization direction is incorrect, the predetermined magnetization direction of each magnet cannot be effectively detected before magnetization, which can easily lead to assembly errors. After magnetization, the component performance may be substandard or even scrapped, resulting in a huge waste of materials and time.

[0003] However, for unmagnetized magnets, since their macroscopic magnetism is not yet apparent, and their internal magnetic domains are in a state of disorder or partial order but with a net external magnetic moment close to zero, existing magnetic detection methods cannot directly and effectively detect their potential, predetermined magnetization direction (i.e., the direction of the magnetocrystalline anisotropy easy magnetization axis). Existing technologies mainly suffer from the following shortcomings: Lack of direct detection methods: There is no efficient detection method specifically for the magnetization direction of unmagnetized magnets.

[0004] There is a risk of accidental magnetization: Some techniques attempt to use a strong magnetic field to slightly "test" magnetize the material beforehand, then detect the weak magnetism to determine the direction. This method carries the risk of accidentally magnetizing a magnet that should not be magnetized, altering its original state, and is not truly non-destructive testing.

[0005] Therefore, there is an urgent need in the field for a method and system that can quickly, intuitively and non-destructively detect the predetermined magnetization direction of an unmagnetized magnet in order to improve the yield, efficiency and reliability of magnetic component production. Summary of the Invention

[0006] This invention aims to provide a method and system for detecting the magnetization direction of an unmagnetized magnet. The method aims to transform the potential orientation information of the invisible magnetic domains inside the magnet into externally observable physical signal differences, thereby achieving rapid and accurate discrimination.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for detecting the magnetization direction of an unmagnetized magnet, comprising the following steps: S1. Apply an external guiding magnetic field to the unmagnetized magnet to be tested; S2. Detect a signal related to the physical state of the unmagnetized magnet under the action of the guiding magnetic field, and use it as a response signal; S3. Based on the correspondence between the response signal and the predetermined magnetization direction, determine the magnetization direction of the unmagnetized magnet.

[0008] Preferably, the strength of the guiding magnetic field is between 50 Gs and 500 Gs.

[0009] Preferably, the response signal in step S2 includes at least one of the following: (a) The magnetic field distribution signal modulated by the unmagnetized magnet in the space surrounding it; (b) The magnetic force or torque signal experienced by the unmagnetized magnet in the guiding magnetic field.

[0010] Preferably, when the response signal is a magnetic field distribution signal, step S2 is achieved by a detection element, wherein the detection element is selected from at least one of a magnetic display, a Hall sensor, and an induction coil.

[0011] In one specific embodiment, the detection element in step S2 is a magnetic display sheet; the discrimination in step S3 includes: observing the color pattern displayed after the magnetic display sheet contacts the surface of the unmagnetized magnet, and comparing the color pattern with a standard color pattern under a known correct magnetization direction.

[0012] In another specific embodiment, the detection element in step S2 is a Hall sensor or an induction coil; the discrimination in step S3 includes: acquiring the electrical signal output by the detection element, and comparing the characteristics of the electrical signal with the pre-calibrated electrical signal characteristics corresponding to the correct and incorrect magnetization directions respectively.

[0013] Preferably, when the response signal is a magnetic force or torque signal, step S2 is performed by a force sensor; the discrimination in step S3 includes comparing the mechanical signal characteristics measured by the force sensor with pre-calibrated mechanical signal characteristics corresponding to the correct and incorrect magnetization directions, respectively.

[0014] The present invention also provides a system for implementing the above method, comprising: A guiding magnetic field generating unit is used to generate and apply the guiding magnetic field to the unmagnetized magnet to be tested; A detection unit is used to detect the response signal and generate a detection result; The discrimination unit is used to determine the magnetization direction based on the detection result; The discrimination unit is an automatic analysis module with preset discrimination logic, or an output device for presenting the detection results as a sensory signal for manual comparison by the operator.

[0015] Preferably, the detection unit is selected from one of a magnetic display, a Hall sensor, an induction coil, and a force sensor.

[0016] Preferably, the guiding magnetic field generating unit includes a magnetized magnet and a position adjustment mechanism for adjusting the relative distance between the magnetized magnet and the unmagnetized magnet.

[0017] To achieve accurate discrimination, system calibration is required before testing. Specifically, representative unmagnetized magnets with known correct and incorrect magnetization directions are used as standard samples. Under fixed detection system parameters, typical response signals (such as magnetosurface color, specific electrical signal values, and mechanical signal values) corresponding to these standard samples are acquired, and the discrimination threshold or standard feature spectrum used to distinguish between correct and incorrect directions is determined accordingly.

[0018] The technical principle of this invention lies in utilizing the modulation effect of the inherent magnetocrystalline anisotropy of an unmagnetized magnet on an applied magnetic field. When an unmagnetized magnet is placed in a weak external guiding magnetic field, the magnetic field distribution or the magnetic force experienced by it in the surrounding space (especially near its surface) will undergo characteristic changes due to the different potential orientations of its internal magnetic domains (i.e., the intended magnetization direction). By detecting the characteristics of this modulated spatial physical field (magnetic field or force field), the intended magnetization direction of the magnet can be indirectly and non-destructively identified.

[0019] Compared with the prior art, the present invention has the following significant advantages: Non-destructive testing: By utilizing the intrinsic properties (magnetic anisotropy) of unmagnetized magnets, a weak external magnetic field is used to "excite" and detect the response, thus achieving non-destructive and indirect detection of the orientation of internal magnetic domains.

[0020] Intuitive identification and easy operation: When using the magnetic display solution, the results are presented directly in color patterns, without the need for professional instruments or complex analysis. Ordinary workers can operate it quickly. It can also be used in automated testing equipment, which greatly improves the testing efficiency and is especially suitable for rapid full inspection on the production line.

[0021] Flexible and adaptable: This invention provides a variety of implementation schemes, from intuitive visualization to high-precision electrical signal detection, which can be flexibly selected according to different accuracy requirements, automation levels and cost budgets, making it widely applicable.

[0022] The results are reliable: This method is based on well-defined physical principles, and there is a direct correspondence between the response signal and the magnetization direction. As long as the guiding magnetic field conditions are consistent, the discrimination results are stable and reliable. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the state of the detection system using a magnetic display as a detection element in Embodiment 1 of the present invention before detection; Figure 2 This is a schematic diagram of the detection process in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the effect of a bright green pattern appearing on a magnetic display when the predetermined magnetization direction of the magnet under test is correct (OK product) in Embodiment 1 of the present invention. Figure 4 This is a schematic diagram of the effect of the magnetic display showing a dark gray color or no change when the predetermined magnetization direction of the magnet under test is incorrect (NG product) in Embodiment 1 of the present invention. Figure 5 Is adopted Figure 1 The image shown is a physical representation of the system's performance in detecting the magnetic components of the Heilbeck magnetic circuit. Figure 6 This is a picture of a magnet under test showing a bright green pattern when the magnet is in the correct predetermined magnetization direction (OK product). Figure 7 When the magnet under test is in the wrong intended magnetization direction (NG product), the magnetic display will show a dark gray or unchanged image.

[0024] Figure 8 This is a schematic diagram of the detection system in progress using a Hall sensor as the detection element in Embodiment 2 of the present invention. Figure 9 This is a schematic diagram of the detection system in progress using a coil as a detection element in Embodiment 3 of the present invention. Figure 10 This is a schematic diagram illustrating the effect when the predetermined magnetization direction of the magnet under test is correct in Embodiment 4 of the present invention; Figure 11 This is a schematic diagram illustrating the effect when the predetermined magnetization direction of the magnet under test is incorrect in Embodiment 4 of the present invention.

[0025] Among them, 10-adjustable distance fixing mechanism, 11-base of adjustable distance fixing mechanism, 20-magnetized magnet for applying guiding magnetic field, 30-magnet for magnetization direction to be tested, 40-detection element (such as MX magnetic display), 12-gaussmeter, 13-Hall sensor probe, 14-magnetic fluxmeter, 15-induction coil, 16-force sensor, 17-fine adjustment knob. Detailed Implementation

[0026] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0027] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0028] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0029] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0030] Example 1: Implementation method using a magnetic display as a detection element This embodiment provides a method and system for detecting the magnetization direction of an unmagnetized magnet, the specific steps of which are as follows: System setup: Reference Figure 1 Prepare a detection system. This system includes: The guiding magnetic field generating unit consists of a magnetized magnet 20 (a sintered neodymium iron boron magnet is used in this embodiment) that provides a stable magnetic field and an adjustable fixing mechanism 10. The adjustable fixing mechanism 10 includes a base 11 for precisely adjusting the horizontal distance between the magnetized magnet 20 and the magnet 30 under test. In this embodiment, the distance between the two is adjusted to approximately 3 cm, and the magnetic field direction of the magnetized magnet 20 is perpendicular to the test surface of the magnet 30 under test.

[0031] Magnetic field distribution detection unit: In this embodiment, a magnetic display plate 40 (model MX) sensitive to magnetic fields is selected as the detection element and is attached to the surface of the magnet 30 to be tested (i.e. the surface with the expected magnetization direction).

[0032] Testing process: S1. Place an unmagnetized neodymium iron boron square magnet, 30, in a fixed position as the magnet to be tested.

[0033] S2. Keep the distance between the magnetized magnet 20 and the magnetic display plate 40 (i.e. the surface of the magnet to be tested) stable at about 3cm. At this time, a weak guiding magnetic field (with an intensity of about 100-300 Gs) is generated at the magnet to be tested 30.

[0034] Due to the inherent magnetocrystalline anisotropy of an unmagnetized magnet, the potential orientation of its internal magnetic domains (i.e., the predetermined magnetization direction) will modulate the guiding magnetic field in the space, resulting in a change in the magnetic field distribution near the magnet surface.

[0035] Results observation and judgment: Observe the color change of the magnetic display plate 40 that is in close contact with the surface of the magnet.

[0036] like Figure 3As shown, assuming the predetermined magnetization direction of the magnet 30 to be tested is perpendicular to the base 11, if the predetermined magnetization direction of the magnet 30 to be tested is correct, the magnetic display sheet 40 will show a clear bright green pattern under the action of the modulated magnetic field.

[0037] like Figure 4 As shown, if the predetermined magnetization direction of the magnet 30 under test is incorrect (e.g., the direction is opposite or deviated), the magnetic display 40 will show as dark gray or no obvious color change (close to its original color).

[0038] By comparing the color pattern displayed on the magnetometer with a known standard color spectrum (bright green corresponds to the correct direction), the intended magnetization direction of the unmagnetized magnet can be determined instantly and intuitively. The entire process is fast, non-destructive, and requires no power or complex signal processing.

[0039] Example 2: Implementation using a Hall sensor.

[0040] This embodiment provides a method and system for detecting the magnetization direction of an unmagnetized magnet based on electrical signals.

[0041] System setup, such as Figure 8 As shown, the system includes: Guiding magnetic field generating unit: Same as in Example 1.

[0042] Magnetic field distribution detection unit: A gaussmeter 12 is used as the detection element. The Hall sensor probe 13 is precisely fixed at a position about 0.5mm-2mm away from the surface of the magnet 30 under test through a finely adjustable bracket, and is used to measure the magnetic induction intensity at that point.

[0043] Testing process: S1. Place the magnet to be tested 30 and fix the position of the Hall sensor probe 13.

[0044] S2. Apply a guiding magnetic field (in this embodiment, the strength is 150 Gs). The unmagnetized magnet modulates the magnetic field near its surface, and the strength of the modulated magnetic field is directly related to the predetermined magnetization direction of the magnet.

[0045] Results observation and judgment: The voltage signal output from the gaussmeter 12 is read. Assuming the predetermined magnetization direction of the magnet 30 under test is correct, its modulation effect will significantly enhance the magnetic field at the probe, and the Hall sensor reading will be approximately 200 Gs. If the predetermined magnetization direction is incorrect, the modulation effect will be very weak or even partially cancel out the guiding magnetic field, and the Hall sensor reading will be only around 100 Gs. By comparing the real-time voltage value with pre-stored standard electrical signal characteristic values ​​or curves for correct and incorrect directions, the system can automatically and accurately complete the discrimination. This method has high sensitivity and is suitable for small magnets or applications requiring quantitative detection.

[0046] Example 3: Implementation using an induction coil This embodiment provides another method and system for detecting the magnetization direction of an unmagnetized magnet based on electrical signals.

[0047] System setup, such as Figure 9 As shown, the system includes: Guiding magnetic field generating unit: Same as in Example 1.

[0048] The magnetic field change detection unit consists of a fluxmeter 14 and an induction coil 15. The induction coil 15 is a multi-turn induction coil, and its axial direction needs to be adjusted according to the preset detection direction. In this embodiment, the induction coil 15 is fixedly placed so that its axial direction is perpendicular to the base 11 and parallel to the detection surface of the magnet under test 30 with the predetermined magnetization direction.

[0049] The magnetometer 14 is electrically connected to the two ends of the induction coil 15 to measure and display the change in magnetic flux (ΔΦ).

[0050] Testing process The core of this embodiment lies in detecting the magnetic flux response, which is related to the magnetization direction, excited by a dynamic or changing guiding magnetic field in an unmagnetized magnet.

[0051] S1: Place the magnet to be tested 30 on the base 11.

[0052] S2: By causing relative motion between the magnet under test 30 and the induction coil 15, a changing magnetic field is generated at the location of the induction coil 15. Specifically, the magnet under test 30 is moved horizontally at a roughly uniform speed along a direction parallel to the base 11 (i.e., perpendicular to the axis of the induction coil 15) for a distance (e.g., 15 cm to 30 cm). Due to the different potential orientations (predetermined magnetization directions) of the magnetic domains within the unmagnetized magnet 30, its "magnetization" response (i.e., the magnitude and direction of the induced equivalent magnetic moment) to the changing external magnetic field varies significantly. This difference modulates the magnetic flux passing through the induction coil 15.

[0053] S3: The magnetometer 14 directly reads the absolute value (|ΔΦ|) of the change in magnetic flux passing through the coil during this magnetic field change, in milliwebers (mWb).

[0054] Results Observation and Judgment Observe the value of the change in magnetic flux displayed on the magnetometer 14.

[0055] Scenario 1 (Correct Predetermined Magnetization Direction): When the predetermined magnetization direction of the magnet under test 30 is consistent with the detection direction (e.g., perpendicular to the base 11 upwards), and optimally coordinated with the excitation direction of the guiding magnetic field, the equivalent magnetic moment induced by the magnet is maximized. This results in the most drastic change in magnetic flux passing through the induction coil 15 under the same magnetic field change excitation. The flux meter 14 displays a large value of magnetic flux change, for example, up to 20 mWb.

[0056] Scenario 2 (Incorrect Predetermined Magnetization Direction): When the predetermined magnetization direction of the magnet under test 30 is opposite to or significantly deviates from the detection direction, the induced equivalent magnetic moment is very small. In this case, the magnetic flux modulation effect caused by the change in the external magnetic field is weak, and the magnetic flux change value displayed by the fluxmeter 14 is significantly smaller, for example, only 2 mWb.

[0057] Discrimination method Because the measured change in magnetic flux differs significantly by an order of magnitude when the magnetization direction is correct versus incorrect (e.g., 20 mWb vs. 2 mWb), a reasonable threshold (e.g., 5 mWb) can be set for rapid discrimination: a measurement value above the threshold is considered correct (OK), while a value below the threshold is considered incorrect (NG). This method is effective against large signal differences, has strong anti-interference capabilities, and provides objective and reliable discrimination results.

[0058] Example 4: Implementation using a force sensor This embodiment provides a method and system for detecting the magnetization direction of an unmagnetized magnet based on mechanical signals.

[0059] System setup, such as Figure 10-11 As shown, the system includes: The guiding magnetic field generating unit consists of a magnetized magnet 20 and an adjustable distance fixing mechanism 10, and its function is the same as that in Embodiment 1.

[0060] The force signal detection unit employs a force sensor 16, whose measuring end is reliably in contact with the back of the magnetized magnet 20 via a mounting bracket with a fine-tuning knob 17. The base 11 of the adjustable distance fixing mechanism 10 is used to fix the magnet 30 under test, while the force sensor 16 is mounted on an independent bracket.

[0061] Testing process: S1. Place the unmagnetized magnet 30 on the base 11, and ensure that the magnetized magnet 20 is in good contact with the force sensor 16.

[0062] S2. Adjust the relative position of the magnetized magnet 20 and the magnet to be tested 30 (the distance is 2cm in this embodiment) and apply a guiding magnetic field with an intensity of 200 Gs.

[0063] Results observation and judgment: The stable force value (F) is read and recorded by the force sensor 16.

[0064] It is assumed that the predetermined magnetization direction of the magnet 30 to be inspected should be perpendicular to the base 11 and consistent with the direction of the guiding magnetic field (or at a small angle). If the direction is correct (OK product), the attractive force shown by the force sensor can reach 5N. If the direction is incorrect (NG product), the attractive force is significantly reduced, only 0.2N.

[0065] By comparing the measured force value with a pre-calibrated threshold value (for example, set to 1N) or a standard force value range, the correctness of the magnetization direction can be quickly and objectively judged. This method has high precision and is easy to realize automatic discrimination.

[0066] Example 5: Verification experiment for mass production To verify the actual detection efficiency of the method of the present invention in mass production, the inventor conducted the following verification experiment.

[0067] A batch of assembled but unmagnetized Halbach maglev components are selected as test samples, and the total number of samples is 30,000. Each component contains multiple unmagnetized neodymium iron boron magnets arranged in a specific direction. According to the production records, there may be quality hazards in this batch due to incorrect placement of the magnet direction.

[0068] Adopt the detection system of the present invention as shown in Figure 1 The guiding magnetic field generating unit uses a standard sintered neodymium iron boron magnet, which is fixed by an adjustable bracket to keep the distance between the magnetizing magnet and the detection point on the surface of the component to be tested at 3 cm, generating a guiding magnetic field with an intensity of 100 Gs. The detection unit uses an MX-type magnetic display film as the detection element. The operator closely attaches the magnetic display film to the predetermined detection area on the outer surface of the component and observes the color pattern shown by the magnetic display film under the action of the guiding magnetic field. By comparing with a pre-established standard color atlas (the bright green pattern corresponding to the correct magnetization direction), the direction of each magnet inside the component can be quickly judged whether it is correct. After detecting all 30,000 components, a total of 312 components showing abnormalities are marked. The magnetic display films on the surfaces of these components present dark gray or no significant color change, which is significantly different from the standard bright green pattern.

[0069] To verify the accuracy of the detection results, destructive disassembly and recheck are carried out on 312 abnormal components. The results confirm that there is at least one magnet with an actual placement direction not in line with the design requirements inside all abnormal components. At the same time, hundreds of components judged to be qualified are randomly selected for recheck, and the results show that the directions of the magnets inside are all correct.

[0070] This verification experiment demonstrates that the method and system of this invention can achieve: high-precision identification of the magnetization direction of unmagnetized magnets, with a defect detection rate of 100% and no missed detections; rapid non-destructive testing, with a single component requiring only a few seconds of inspection time, suitable for the full inspection requirements of production lines; simple and intuitive operation, with test results completely consistent with destructive verification results, thus verifying reliability. This experiment fully demonstrates the practical value of this invention in improving the production efficiency and quality control of magnetic components.

[0071] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

[0072] It should be particularly noted that the various embodiments listed in this specification and accompanying drawings are intended to illustrate the technical solutions and advantages of the present invention, and not to limit the scope of protection of the present invention. Without departing from the core ideas and technical effects of the present invention, those skilled in the art can make any form of improvement, substitution, combination, or modification to the structural arrangement, process parameters, material selection, control logic, etc., of the described embodiments; any obvious changes based on the same concept should be considered equivalent solutions of the present invention and should be included within the scope of protection defined by the claims of the present invention. The actual scope of protection of the present invention is determined by the appended claims and should be correctly understood in conjunction with the specification and accompanying drawings.

Claims

1. A method for detecting the magnetization direction of an unmagnetized magnet, characterized in that, Includes the following steps: S1. Apply an external guiding magnetic field to the unmagnetized magnet to be tested; S2. Detect a signal related to the physical state of the unmagnetized magnet under the action of the guiding magnetic field, and use it as a response signal; S3. Based on the correspondence between the response signal and the predetermined magnetization direction, determine the magnetization direction of the unmagnetized magnet.

2. The method according to claim 1, characterized in that, The strength of the guiding magnetic field is between 50 Gs and 500 Gs.

3. The method according to claim 1 or 2, characterized in that, The response signal in step S2 includes at least one of the following: (a) The magnetic field distribution signal modulated by the unmagnetized magnet in the space surrounding it; (b) The magnetic force or torque signal experienced by the unmagnetized magnet in the guiding magnetic field.

4. The method according to claim 3, characterized in that, When the response signal is a magnetic field distribution signal, step S2 is performed by a detection element, which is selected from at least one of a magnetic display, a Hall sensor, and an induction coil.

5. The method according to claim 4, characterized in that, The detection element is a magnetic display sheet; the discrimination in step S3 includes: observing the color pattern displayed after the magnetic display sheet contacts the surface of the unmagnetized magnet, and comparing the color pattern with the standard color pattern under the known correct magnetization direction.

6. The method according to claim 4, characterized in that, The detection element is a Hall sensor or an induction coil; the discrimination in step S3 includes: acquiring the electrical signal output by the detection element, and comparing the characteristics of the electrical signal with the characteristics of the pre-calibrated electrical signals corresponding to the correct and incorrect magnetization directions respectively.

7. The method according to claim 3, characterized in that, When the response signal is a magnetic force or torque signal, step S2 is performed by a force sensor for detection; the discrimination in step S3 includes comparing the mechanical signal characteristics measured by the force sensor with the pre-calibrated mechanical signal characteristics corresponding to the correct and incorrect magnetization directions, respectively.

8. A system for implementing the method according to any one of claims 1 to 7, characterized in that, include: A guiding magnetic field generating unit is used to generate and apply the guiding magnetic field to the unmagnetized magnet to be tested; A detection unit is used to detect the response signal and generate a detection result; The discrimination unit is used to determine the magnetization direction based on the detection result; The discrimination unit is an automatic analysis module with preset discrimination logic, or an output device for presenting the detection results as a sensory signal for manual comparison by the operator.

9. The system according to claim 8, characterized in that, The detection unit is selected from one of the following: magnetic display, Hall sensor, induction coil, and force sensor.

10. The system according to claim 8 or 9, characterized in that, The guiding magnetic field generating unit includes a magnetized magnet and a position adjustment mechanism for adjusting the relative distance between the magnetized magnet and the unmagnetized magnet.

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