Magnetic permeability enhancing repair process for low-weight rare earth magnetic steel

Abstract

The invention discloses a magnetic conductance enhanced repairing process for low-weight rare earth magnetic steel, and relates to the field of repairing of the low-weight rare earth magnetic steel. Comprising the following steps: scanning magnetic steel by adopting an online monitoring system, and registering and fusing acquired data to generate a comprehensive damage map; according to the damage map, after the damage area is accurately coated with the repairing agent paste, heating is synchronously conducted, and a gradient pulsed magnetic field and ultrasonic vibration are applied; after cooling, removing the redundant repairing agent, and then carrying out aging treatment; the online monitoring system comprises a pulsed magnetic field unit, a Hall sensor array and a terahertz imaging unit. The components of the repairing agent comprise a nanoscale Fe-Si-Al alloy and a low-melting-point alloy. The magnetic flux density and the coercive force of the repaired magnet are recovered, the magnetic flux recovery rate can reach 103%, the effective magnetic conductivity can be improved by 24%, and the crack repairing depth is larger than or equal to 175 microns.

Description

Technical Field

[0001] This invention relates to the field of low-heavy rare earth magnet repair technology, specifically to a magnetic permeability enhancement repair process for low-heavy rare earth magnets. Background Technology

[0002] Low-heavy rare-earth magnets, especially neodymium iron boron permanent magnets with low dysprosium (Dy) and low terbium (Tb) content, are core functional materials supporting the development of high-end equipment such as modern high-efficiency energy-saving motors, new energy vehicle drive systems, wind power generation, and precision servo control. Reducing the content of heavy rare-earth elements is an inevitable choice to cope with the scarcity of strategic resources and cost pressures. However, this inevitably sacrifices the intrinsic coercivity (Hcj) and temperature stability of the magnet, resulting in particularly prominent performance degradation problems under complex and harsh service environments (such as high temperature, high humidity, high frequency vibration, and alternating electromagnetic stress).

[0003] Performance degradation manifests primarily in three interrelated failure modes: first, irreversible demagnetization caused by irreversible reversal of magnetic moments under high-temperature conditions; second, intergranular corrosion preferentially occurring due to the low electrochemical potential of the neodymium-rich grain boundary phase, which in turn leads to the destruction of the magnetic isolation phase; and third, microcracks that initiate and propagate along grain boundaries under alternating stress, ultimately resulting in the simultaneous degradation of the magnet's structural integrity and magnetic properties. The accumulation of these micro-damages not only causes irreversible losses in magnetic flux density (Br) and coercivity, but also directly leads to decreased motor efficiency, increased torque ripple, and reduced operational reliability.

[0004] Currently, strategies for addressing this type of performance degradation are mainly divided into two categories: protection and repair. In terms of protection, traditional electroplating (such as nickel plating, zinc plating), physical vapor deposition (PVD), or spray coatings can delay surface corrosion to some extent, but they cannot address existing internal damage and are completely ineffective against demagnetization and cracks.

[0005] In terms of detection and repair, existing technologies have significant limitations: First, in the detection stage, manual inspection relying on offline sampling (such as magnetic measuring instruments and optical microscopes) is inefficient and cannot achieve real-time monitoring; conventional non-destructive testing techniques such as eddy current testing are only sensitive to surface defects, while ultrasonic testing is limited by noise interference from the material's grain structure, making it difficult to accurately identify subsurface hidden cracks and corrosion pores below 200 micrometers, and even more difficult to quickly quantify and locate demagnetized areas. Second, in the repair stage, thermal processing methods such as laser cladding generate high-temperature heat-affected zones, which easily cause rare earth element segregation and main phase grain growth, thus exacerbating performance degradation; local remagnetization technology can only temporarily restore apparent magnetic flux and cannot repair the damaged grain boundary microstructure, thus only treating the symptoms and not the root cause, and attenuation will quickly recur.

[0006] Therefore, there is an urgent need in this field to develop a completely new remanufacturing paradigm that can achieve a leap from "precise diagnosis" to "radical repair" and then to "performance gain". Summary of the Invention

[0007] The purpose of this invention is to provide a magnetic permeability enhancement repair process for low-heavy rare earth magnets, which can effectively repair demagnetization, corrosion and microcrack damage of magnets. It can also actively improve the effective magnetic permeability of magnets by constructing high magnetic permeability channels at grain boundaries, thereby achieving a breakthrough in the performance of the repaired magnets and solving the technical problems of difficult repair and inability to improve the performance of existing low-heavy rare earth magnets.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A magnetic permeability enhancement and repair process for low-heavy rare-earth magnets includes the following steps:

[0010] S100: An online monitoring system is used to scan the magnets, and the collected data is registered and fused to generate a comprehensive damage map.

[0011] S200. Based on the damage map, the repair agent paste is precisely applied to the damaged area, and heating, gradient pulse magnetic field and ultrasonic vibration are applied simultaneously.

[0012] S300, after cooling, remove excess repair agent and then perform aging treatment;

[0013] In step S100, the online monitoring system includes a pulsed magnetic field unit, a Hall sensor array, and a terahertz imaging unit; the repair agent consists of nanoscale Fe-Si-Al alloy and low-melting-point alloy.

[0014] Existing technologies can only provide protection (such as electroplating) or restoration (such as remagnetization), with the goal of restoring the product to its original state.

[0015] This invention is the first to propose the concept of "functionalized repair" or "repair-enhancement" integration. By introducing nano-soft magnetic materials (Fe-Si-Al) into the repair agent and using a pulsed magnetic field to guide their oriented alignment at the grain boundaries, not only is the damage repaired structurally, but the magnetic circuit is also reconstructed functionally, forming a high-permeability channel.

[0016] After precisely applying the repair agent paste to the damaged area, only a thermal field is used. Heating the repair agent melts the low-melting-point alloy, giving it fluidity. The repair agent can only slowly penetrate through capillary action, which is inefficient and cannot be directed. Simultaneously, a gradient pulsed magnetic field is applied to provide the main directional driving force (Lorentz force), propelling the repair agent's penetration and guiding the directional alignment of the nano-soft magnetic particles. Simultaneously, ultrasonic vibration is applied, utilizing the "cavitation" and "acoustic flow" effects to clean the interface, prevent agglomeration, and enhance wetting. This allows the repair agent to fully wet and penetrate even the finest cracks, preventing internal defects such as pores. These three factors work synergistically, through the coupling effect of multi-physics fields, to ensure that the repair agent can quickly, directionally, deeply, and densely penetrate into the microscopic defects of the magnet, achieving the directional alignment of the nano-soft magnetic particles, ultimately achieving the dual goals of repair and enhancement.

[0017] Electromagnetic field generating unit: It consists of a capacitor discharge pulse power supply and a magnetic pole head. The magnetic pole head needs to adopt a hollow or water-cooled design to withstand the nearby thermal environment.

[0018] Precision temperature control unit: It adopts non-contact heating methods such as infrared laser or focused infrared lamp. Its optical path can be designed to irradiate the workpiece surface from the gap of the magnetic pole head, thereby realizing the synchronization of heating and magnetic field application in space.

[0019] Ultrasonic vibration unit: The ultrasonic transducer is integrated into the sample stage or magnetic pole head, so that the vibration energy is directly transmitted to the workpiece.

[0020] Integrated control system: A central controller coordinates the startup, parameter output, and timing of the three systems, ensuring that they start and end precisely at the same time and maintain parameter stability throughout the entire processing cycle.

[0021] Further, in step S100, a pulsed magnetic field is applied to locally saturate the magnet; a Hall sensor array is used to collect the three-dimensional distribution of the surface magnetic field; and a terahertz imaging system is used to scan the surface and subsurface regions at a frequency of 1~4THz.

[0022] Under current technological conditions, pulsed magnetic field strengths of 3.0T~5.0T and pulse widths of 2ms~20ms can be achieved for localized saturation magnetization of magnets. The entire detection process can be completed in a short time (3 minutes) without disassembling the magnet or motor, meeting the efficiency requirements of industrial online inspection. Simultaneously, it acquires the two most critical performance degradation information categories: functional (demagnetization) and structural (cracks, corrosion), creating a complete damage profile. It can not only detect defects but also accurately locate their three-dimensional coordinates, quantify the demagnetization rate, and measure the size and depth of cracks, providing an absolute basis for subsequent precise repair.

[0023] Using pulsed magnetic fields alone cannot detect early-stage hidden cracks and corrosion that have not yet caused significant magnetic flux loss. Using terahertz imaging alone cannot quantify the severity of demagnetization, nor can it distinguish whether a defect is a crack or a non-magnetic inclusion.

[0024] This solution generates a comprehensive damage map through data registration and fusion, which can clearly determine whether a magnetic field anomaly is caused by damage to the underlying structure; accurately assess the actual impact of structural damage on magnetic properties; and perform dual qualitative, locational, and quantitative analysis of defects, both functionally and structurally.

[0025] Furthermore, in step S100, the comprehensive damage map includes the distribution and demagnetization intensity of the demagnetized area, the location, size and depth of hidden cracks and corrosion pores ≤200μm below the surface, and the coordinate location of the damaged area.

[0026] Further, in step S200, the repair agent paste, by weight, comprises the following components: 60-85 parts of composite repair agent powder, 10-30 parts of terpineol, 2-5 parts of ethyl cellulose, 0.5-1.5 parts of phosphate ester dispersant (such as BYK-110), and 0.1-0.5 parts of organosilicon leveling agent (such as BYK-320);

[0027] The composite repair agent powder is obtained by combining nano-scale Fe-Si-Al alloy powder and low-melting-point alloy powder at a mass ratio of 1:3~9.

[0028] The formulation employs an extremely high content of functional phases, far exceeding that of conventional electronic pastes or thermal pastes. This ensures sufficient material to fill defects and form a reinforcing phase after repair. However, this also presents significant challenges due to high viscosity, easy agglomeration, and difficult application. To address this contradiction, the formulation introduces a specific ratio of phosphate ester dispersants and silicone leveling agents: the dispersants effectively adsorb onto the surface of nanoparticles, fundamentally preventing the agglomeration of highly active nanoparticles through steric hindrance or electrostatic repulsion, ensuring their uniform distribution within the system; the leveling agents significantly reduce the surface tension of the paste through extremely low addition amounts, allowing for better wetting and leveling of the substrate surface after coating, avoiding defects such as pinholes, thus achieving a balance between high solids content and good processability.

[0029] The composite repair agent powder achieves a perfect fusion of function and process by combining nano-sized Fe-Si-Al soft magnetic powder with low-melting-point alloy powder in a precise mass ratio of 1:3 to 9: the low-melting-point alloy acts as a "carrier" and "structural repair phase," which can flow and penetrate into microscopic defects after heating and melting, achieving tight sealing and filling; while the nano-soft magnetic particles carried by it act as a "functional enhancement phase," which are oriented under the action of a subsequent pulsed magnetic field, forming high permeability channels at the grain boundaries, thereby upgrading the traditional passive repair to an active performance gain.

[0030] The selection of the type and ratio of organic carriers (terpineol and ethyl cellulose) not only provides suitable rheological properties during the process, but also allows them to completely volatilize or pyrolyze during the repair heating stage, leaving no residue and avoiding secondary damage to the magnet's performance.

[0031] Furthermore, the low-melting-point alloy is selected from Sn-Bi-based alloys (CW-Sn42Bi58), Sn-In-based alloys (In52Sn48), or In-Bi-based alloys (In51.4Bi31.4Sn17.2), and its melting point is 60-200℃.

[0032] Furthermore, the nanoscale Fe-Si-Al alloy powder is prepared by high-energy ball milling: using micron-sized Fe-Si-Al alloy powder as raw material, it is ball-milled at high speed for 20 to 80 hours under argon protection at a high ball-to-material ratio of 10 to 20:1, and 1-3 wt% anhydrous ethanol is added to obtain nanoparticles with an average particle size in the range of 50 to 200 nm.

[0033] Furthermore, in step S200, the method for preparing the repair agent ointment includes the following steps:

[0034] Step 1: Add ethyl cellulose to terpineol and stir at 60-80°C until completely dissolved to obtain a clear and transparent solution; then cool.

[0035] Step 2: Mix the composite repair agent powder and dispersant evenly and add them to the solution obtained in Step 1. Continue stirring until a uniform paste is formed.

[0036] Step 3: Grind the above paste into a fine and uniform paste, remove air bubbles under a vacuum of -0.095MPa or higher for 3-5 minutes, and filter through a 200-400 mesh sieve to obtain the repair agent paste.

[0037] First, a stepwise preparation method is adopted. First, a uniform organic carrier phase is formed by heating and dissolving, providing a stable environment for subsequent powder dispersion and avoiding agglomeration and insolubility problems that may occur with direct mixing. Second, a dispersant premixing step is introduced, allowing dispersant molecules to preferentially coat the surface of the composite repair agent powder, suppressing the tendency of nanoparticles to agglomerate due to their high surface energy from the source. This is a key prerequisite for achieving high uniformity. Finally, a post-processing procedure combining high-shear milling (such as three-roll milling) with vacuum degassing and precision filtration is employed. High-shear milling provides shear force far exceeding that of ordinary stirring, thoroughly breaking down all soft and hard agglomerates, ensuring that each nanoparticle is fully wetted by the organic carrier, thus forming a fine and uniform paste microstructure. The subsequent vacuum degassing effectively eliminates gas entrained during the process, preventing gas expansion and defects during subsequent repair heating. The final filtration step ensures the purity and reliability of the paste, removing potential large-particle impurities that could clog dispensing equipment. The entire process chain is interconnected and works synergistically, resulting in a paste that has high solids content, excellent rheological properties (such as good thixotropy), long-term storage stability, and uniformity.

[0038] Furthermore, in step S200, the heating temperature is 138~200℃; the conditions for the gradient pulse magnetic field are: 2.0~3.5T pulse magnetic field, field strength gradient >50T / m, pulse frequency 1~5Hz; the frequency of ultrasonic vibration is 20~40kHz, and the amplitude is 1~5μm.

[0039] Furthermore, in step S300, the cooling adopts a two-step method: first, it is rapidly cooled to 95~105℃ at a rate of 10~15℃ / s, and then slowly cooled to 20~30℃.

[0040] The first step, rapid cooling (10~15℃ / s), aims to quickly solidify the molten low-melting-point alloy repair agent by passing its solidification point. This effectively refines the solidification structure, prevents alloy component segregation, and ensures that the nano-soft magnetic particles are rapidly fixed at the predetermined grain boundary positions, maintaining the directional arrangement structure imparted by the pulsed magnetic field and laying the foundation for the formation of continuous high-permeability channels. The second step, slow cooling, involves a gradual cooling process from 95~105℃ to room temperature, after the alloy body has solidified and its shape has stabilized. This significantly reduces the thermal stress caused by the difference in thermal expansion coefficients between the repair area and the magnetic steel matrix, preventing microcracks from forming in brittle grain boundary regions or within the repair body, thus ensuring the structural integrity and long-term reliability of the repaired area.

[0041] Furthermore, in step S300, the aging treatment conditions include: holding at 150~180℃ for 1~2 hours.

[0042] The role of aging treatment: It promotes interfacial diffusion and alloying. During the 1-2 hour holding period, further atomic interdiffusion occurs between the low-melting-point alloying components (such as Sn, Bi, In) in the repair agent and the grain boundary phase (usually neodymium-rich phase) of the magnetic steel matrix. This not only significantly enhances the metallurgical bonding strength of the repair agent / matrix interface and improves the bonding force, but also modifies the original grain boundary phase to a certain extent, improving its stability. This temperature is lower than the sintering temperature of the main phase of the magnet, so it will not damage its intrinsic magnetism, but it is sufficient to effectively eliminate the microscopic internal stress remaining in the previous process steps (especially the rapid cooling process), making the repaired magnet more dimensionally stable. For the nano-soft magnetic Fe-Si-Al phase in the repair agent, this heat treatment process helps to stabilize its microstructure, optimize its magnetic properties, and ensure that the formed "high permeability channel" has long-lasting and stable performance.

[0043] Compared with the prior art, the beneficial effects of the present invention are:

[0044] 1. This invention integrates terahertz and magnetic field detection, enabling both quantitative assessment of demagnetization and visualization of subcutaneous 200μm hidden damage, achieving both clear visibility and accurate measurement. Multi-field coupling ensures the repair agent penetrates deep into grain boundaries and the finest microcracks, achieving tight sealing and fundamentally blocking damage propagation paths. The repaired magnet not only recovers its magnetic flux density (Br) and coercivity (Hcj), with a flux recovery rate of up to 103%, but also sees a 24% increase in effective permeability, achieving a crack repair depth ≥175μm.

[0045] 2. This invention integrates online detection and repair, significantly shortening maintenance time; precise local repair minimizes the thermal impact on the magnet substrate, avoiding the performance degradation risk caused by overall heating; the repaired grain boundaries simultaneously possess better mechanical strength and higher corrosion resistance, with a salt spray resistance time ≥966h, improving the long-term reliability of the magnet under harsh working conditions; it extends the service life of expensive low-heavy rare earth magnets, avoiding the high cost of replacing the entire unit, and is particularly suitable for predictive maintenance of large equipment such as new energy vehicle drive motors and wind turbines. Detailed Implementation

[0046] Example 1

[0047] Nanoscale Fe-Si-Al soft magnetic powder was prepared by high-energy ball milling: micron-sized Fe-Si-Al alloy powder (model: TITD-WFSA) was used as raw material. Under argon protection, a planetary ball mill was used with cemented carbide balls as the grinding medium. The mixture was ball-milled at high speed for 50 hours at a high ball-to-material ratio (15:1). 2wt% of anhydrous ethanol was added as a process control agent. Finally, nanoparticles with an average particle size in the range of 125nm were obtained.

[0048] Example 2

[0049] Nanoscale Fe-Si-Al soft magnetic powder was prepared by high-energy ball milling: micron-sized Fe-Si-Al alloy powder (model: TITD-WFSA) was used as raw material. Under argon protection, a planetary ball mill was used with cemented carbide balls as the grinding medium. The mixture was ball-milled at high speed for 20 hours at a high ball-to-material ratio (10:1). 1 wt% of anhydrous ethanol was added as a process control agent. Finally, nanoparticles with an average particle size in the range of 50 nm were obtained.

[0050] Example 3

[0051] Nanoscale Fe-Si-Al soft magnetic powder was prepared by high-energy ball milling: micron-sized Fe-Si-Al alloy powder (model: TITD-WFSA) was used as raw material. Under argon protection, a planetary ball mill was used with cemented carbide balls as the grinding medium. The mixture was ball-milled at high speed for 80 hours at a high ball-to-material ratio (20:1). wt% of anhydrous ethanol was added as a process control agent. Finally, nanoparticles with an average particle size in the range of 200 nm were obtained.

[0052] Example 4

[0053] The repair agent paste contains the following components: 680g of compound repair agent powder, 200g of terpineol, 35g of ethyl cellulose, 10g of phosphate ester dispersant, and 3g of organosilicon leveling agent;

[0054] The composite repair agent powder is obtained by combining nano-scale Fe-Si-Al alloy powder (prepared by the method in Example 1) and low-melting-point alloy powder at a mass ratio of 1:6.

[0055] The low-melting-point alloy is a Sn-Bi based alloy (CW-Sn42Bi58) with a melting point of 138℃.

[0056] The preparation method of the repair agent ointment includes the following steps:

[0057] Step 1: Add ethyl cellulose to terpineol, stir at 70°C until completely dissolved to obtain a clear and transparent solution, then cool.

[0058] Step 2: Mix the composite repair agent powder and dispersant evenly and add them to the solution obtained in Step 1. Continue stirring until a uniform paste is formed.

[0059] Step 3: Grind the above paste into a fine and uniform paste, remove air bubbles under a vacuum of -0.1MPa for 4 minutes, and filter through a 300-mesh sieve to obtain the repair agent paste.

[0060] Example 5

[0061] The repair agent paste contains the following components: 600g of compound repair agent powder, 100g of terpineol, 20g of ethyl cellulose, 5g of phosphate ester dispersant, and 1g of organosilicon leveling agent;

[0062] The composite repair agent powder is obtained by combining nano-sized Fe-Si-Al alloy powder (prepared by the method of Example 1) and low-melting-point alloy powder at a mass ratio of 1:3.

[0063] The low-melting-point alloy is an In-Bi based alloy (In51.4Bi31.4Sn17.2), with a melting point of 200℃.

[0064] The preparation method of the repair agent ointment includes the following steps:

[0065] Step 1: Add ethyl cellulose to terpineol, stir at 60°C until completely dissolved to obtain a clear and transparent solution, then cool.

[0066] Step 2: Mix the composite repair agent powder and dispersant evenly and add them to the solution obtained in Step 1. Continue stirring until a uniform paste is formed.

[0067] Step 3: Grind the above paste into a fine and uniform paste, remove air bubbles under a vacuum of -0.098MPa for 3 minutes, and filter through a 200-mesh sieve to obtain the repair agent paste.

[0068] Example 6

[0069] The repair agent paste contains the following components: 850g of compound repair agent powder, 300g of terpineol, 50g of ethyl cellulose, 15g of phosphate ester dispersant, and 5g of organosilicon leveling agent;

[0070] The composite repair agent powder is obtained by combining nano-scale Fe-Si-Al alloy powder (prepared by the method of Example 1) and low-melting-point alloy powder at a mass ratio of 1:9.

[0071] The low-melting-point alloy is a Sn-In based alloy (In52Sn48), with a melting point of 118℃.

[0072] The preparation method of the repair agent ointment includes the following steps:

[0073] Step 1: Add ethyl cellulose to terpineol, stir at 80°C until completely dissolved to obtain a clear and transparent solution, then cool.

[0074] Step 2: Mix the composite repair agent powder and dispersant evenly and add them to the solution obtained in Step 1. Continue stirring until a uniform paste is formed.

[0075] Step 3: Grind the above paste into a fine and uniform paste, remove air bubbles under a vacuum of -0.12MPa for 5 minutes, and filter through a 400-mesh sieve to obtain the repair agent paste.

[0076] Comparative Example 1

[0077] In the formulation, the composite repair agent powder is obtained by combining nano-sized Fe-Si-Al alloy powder (prepared by the method in Example 1) and Sn-Bi-based alloy powder (CW-Sn42Bi58) at a mass ratio of 1:1. The remaining formulation components, parameters, and preparation methods are the same as in Example 4.

[0078] Comparative Example 2

[0079] In the formulation, the composite repair agent powder is obtained by combining nano-sized Fe-Si-Al alloy powder (prepared by the method in Example 1) and Sn-Bi-based alloy powder (CW-Sn42Bi58) at a mass ratio of 1:15. The remaining formulation components, parameters, and preparation methods are the same as in Example 4.

[0080] The performance parameters of the repair agent ointments prepared in Examples 4-6 and Comparative Examples 1-2 are shown in Table 1.

[0081] Table 1. Performance parameters of the repair agent ointments prepared in Examples 4-6 and Comparative Examples 1-2

[0082]

[0083] As shown in Table 1, the repair agent pastes prepared in Examples 4-6 exhibit the following characteristics: magnetic permeability improvement of up to 29%, crack repair depth of up to 200 μm, corrosion protection up to 1030 h, and interfacial bonding strength ≥78%.

[0084] In Comparative Example 1, the excess nanoparticles were completely coated by the low-melting-point alloy. During the process, they were easily oxidized and agglomerated, which blocked the permeation channels, resulting in an increase in magnetic permeability (10%) and bonding strength (55 MPa).

[0085] Comparative Example 2 has insufficient functional phase and cannot form a continuous magnetic permeability enhancement network. Therefore, the increase in magnetic permeability is weak (5%), and the performance enhancement effect is lost.

[0086] The present invention demonstrates that a mass ratio of nanoparticles to low-melting-point alloys in the range of 1:3 to 9 ensures both sufficient nanoparticles to construct high magnetic permeability pathways and a sufficient amount of low-melting-point alloys as a carrier to achieve good penetration and bonding.

[0087] Example 7

[0088] A magnetic permeability enhancement and repair process for low-heavy rare-earth magnets includes the following steps:

[0089] S100: An online monitoring system is used to scan the magnet, and the collected data is registered and fused to generate a comprehensive damage map. The online monitoring system includes a pulsed magnetic field unit, a Hall sensor array (model GDB-H-S64), and a terahertz imaging unit (model MICROXCAM-384I-THZ). A pulsed magnetic field is applied to locally saturate the magnet, and the surface magnetic field distribution is collected by the Hall sensor array to form distribution data. The surface and subsurface regions are scanned by the terahertz imaging system at a frequency of 0.5THz. The comprehensive damage map includes the distribution and intensity of demagnetized areas, the location, size, and depth of hidden cracks and corrosion pores ≤200μm below the surface, and the coordinate location of the damaged areas.

[0090] S200. Based on the damage map, the repair agent paste (prepared by the method in Example 4) is precisely applied to the damaged area, and then simultaneously heated, a gradient pulsed magnetic field and ultrasonic vibration are applied; the heating temperature is 170℃; the conditions of the gradient pulsed magnetic field are: 2.8T pulsed magnetic field, field strength gradient 55T / m, pulse frequency 3Hz; the frequency of ultrasonic vibration is 30kHz and the amplitude is 3μm.

[0091] S300: First, rapidly cool to 100°C at a rate of 12°C / s, then slowly cool to 25°C. After cooling, remove excess repair agent, and then perform aging treatment: hold at 165°C for 1.5 hours.

[0092] Example 8

[0093] A magnetic permeability enhancement and repair process for low-heavy rare-earth magnets includes the following steps:

[0094] S100: An online monitoring system is used to scan the magnet, and the collected data is registered and fused to generate a comprehensive damage map. The online monitoring system includes a pulsed magnetic field unit, a Hall sensor array (model GDB-H-S64), and a terahertz imaging unit (model MICROXCAM-384I-THZ). A pulsed magnetic field is applied to locally saturate the magnet, and the surface magnetic field distribution is collected by the Hall sensor array to form distribution data. The surface and subsurface regions are scanned by the terahertz imaging system at a frequency of 0.1THz. The comprehensive damage map includes the distribution and intensity of demagnetized areas, the location, size, and depth of hidden cracks and corrosion pores ≤200μm below the surface, and the coordinate location of the damaged areas.

[0095] S200. Based on the damage map, the repair agent paste (prepared by the method in Example 4) is precisely applied to the damaged area, and then simultaneously heated, a gradient pulsed magnetic field and ultrasonic vibration are applied; the heating temperature is 138℃; the conditions of the gradient pulsed magnetic field are: 2.0T pulsed magnetic field, field strength gradient 50.1T / m, pulse frequency 1Hz; the frequency of ultrasonic vibration is 20kHz and the amplitude is 1μm.

[0096] S300: First, rapidly cool to 95°C at a rate of 10°C / s, then slowly cool to 30°C. After cooling, remove excess repair agent, and then perform aging treatment: keep at 150°C for 1 hour.

[0097] Example 9

[0098] A magnetic permeability enhancement and repair process for low-heavy rare-earth magnets includes the following steps:

[0099] S100: An online monitoring system is used to scan the magnet, and the collected data is registered and fused to generate a comprehensive damage map. The online monitoring system includes a pulsed magnetic field unit, a Hall sensor array (model GDB-H-S64), and a terahertz imaging unit (model MICROXCAM-384I-THZ). A pulsed magnetic field is applied to locally saturate the magnet, and the surface magnetic field distribution is collected by the Hall sensor array to form distribution data. The surface and subsurface regions are scanned by the terahertz imaging system at a frequency of 1.0 THz. The comprehensive damage map includes the distribution and intensity of demagnetized areas, the location, size, and depth of hidden cracks and corrosion pores ≤200 μm below the surface, and the coordinate location of the damaged areas.

[0100] S200. Based on the damage map, the repair agent paste (prepared by the method in Example 4) is precisely applied to the damaged area, and then simultaneously heated, a gradient pulsed magnetic field and ultrasonic vibration are applied; the heating temperature is 200℃; the conditions of the gradient pulsed magnetic field are: 3.5T pulsed magnetic field, field strength gradient 60T / m, pulse frequency 5Hz; the frequency of ultrasonic vibration is 40kHz and the amplitude is 5μm.

[0101] S300: First, rapidly cool to 105°C at a rate of 15°C / s, then slowly cool to 30°C. After cooling, remove excess repair agent, and then perform aging treatment: keep at 180°C for 2 hours.

[0102] Comparative Example 3

[0103] In process step S200, no ultrasonic vibration is applied. The remaining process parameters are exactly the same as in Example 7.

[0104] Comparative Example 4

[0105] In process step S200, no gradient pulsed magnetic field is applied. The remaining process parameters are exactly the same as in Example 7.

[0106] Comparative Example 5

[0107] Step S200 is modified as follows: first heat the coating repair agent and keep it at that temperature for 3 minutes; then stop heating and apply the same pulsed magnetic field and ultrasonic vibration for 3 minutes. The remaining process parameters are exactly the same as in Example 7.

[0108] The performance parameters of the low-heavy rare earth magnets repaired using the repair processes of Examples 7-9 and Comparative Examples 3-5 are shown in Table 2.

[0109] Table 2 shows the performance parameters of the low heavy rare earth magnets after repair using the repair processes in Examples 7-9 and Comparative Examples 3-5.

[0110]

[0111] Note: The test method for magnetic flux recovery rate is: the ratio of the magnetic flux after repair to the original new magnetic flux;

[0112] The test method for irreversible magnetic flux loss after high-temperature aging is as follows: after holding at 180℃ for 1000 hours, the magnetic flux loss rate is measured.

[0113] As shown in Table 2, in Examples 7 to 9, the magnetic flux recovery rate can reach 103%, the magnetic permeability is increased by ≥24%, the crack repair depth is ≥175μm, the interface bonding strength is ≥83MPa, the salt spray resistance time is ≥966h, and the irreversible loss of magnetic flux after high temperature aging is ≤3.7%.

[0114] In Comparative Example 3, the lack of ultrasonic cleaning and penetration aids significantly reduced the penetration capacity of the repair agent, resulting in a significant decrease in crack repair depth (80μm) and bonding strength (55MPa), leading to poorer durability (400h salt spray resistance) and anti-aging performance (8.2% loss).

[0115] In Comparative Example 4, the lack of a magnetic field for directional driving prevented the nanoparticles from forming a high magnetic permeability pathway, resulting in a magnetic permeability increase of only 3%, which was almost ineffective; the repair agent relied solely on capillary action to penetrate, resulting in the shallowest repair depth (40 μm).

[0116] In Comparative Example 5, the step-by-step process disrupted the synchronization effect, and all indicators were far inferior to those of Example 7, which was processed synchronously.

[0117] This demonstrates that the simultaneous application of the "thermal-magnetic-acoustic" three fields in this invention is an inseparable technical whole.

Claims

1. A magnetic permeability enhancement and repair process for low-heavy rare-earth magnets, characterized in that, Includes the following steps: S100: An online monitoring system is used to scan the magnets, and the collected data is registered and fused to generate a comprehensive damage map. S200. Based on the damage map, the repair agent paste is precisely applied to the damaged area, and heating, gradient pulse magnetic field and ultrasonic vibration are applied simultaneously. S300, after cooling, remove excess repair agent and then perform aging treatment; In step S100, the online monitoring system includes a pulsed magnetic field unit, a Hall sensor array, and a terahertz imaging unit; the repair agent consists of nanoscale Fe-Si-Al alloy and low-melting-point alloy.

2. The repair process according to claim 1, characterized in that, In step S100, a pulsed magnetic field is applied to locally saturate the magnet, and a Hall sensor array is used to collect the surface magnetic field distribution to form distribution data; the surface and subsurface regions are scanned by a terahertz imaging system at a frequency of 0.1~1.0THz.

3. The repair process according to claim 1, characterized in that, In step S100, the comprehensive damage map includes the distribution and demagnetization intensity of the demagnetized area, the location, size and depth of hidden cracks and corrosion pores ≤200μm below the surface, and the coordinate location of the damaged area.

4. The repair process according to claim 1, characterized in that, In step S200, the repair agent paste, by weight, comprises the following components: 60-85 parts of composite repair agent powder, 10-30 parts of terpineol, 2-5 parts of ethyl cellulose, 0.5-1.5 parts of phosphate ester dispersant, and 0.1-0.5 parts of organosilicon leveling agent; The composite repair agent powder is obtained by combining nano-scale Fe-Si-Al alloy powder and low-melting-point alloy powder at a mass ratio of 1:3~9.

5. The repair process according to claim 4, characterized in that, The low-melting-point alloy is selected from Sn-Bi-based alloys, Sn-In-based alloys, or In-Bi-based alloys, and its melting point is 60~200℃.

6. The repair process according to claim 4, characterized in that, The nanoscale Fe-Si-Al alloy powder was prepared by high-energy ball milling: using micron-sized Fe-Si-Al alloy powder as raw material, the powder was ball-milled at high speed for 20 to 80 hours under argon protection at a high ball-to-material ratio of 10 to 20:1, and 1 to 3 wt% anhydrous ethanol was added to obtain nanoparticles with an average particle size in the range of 50 to 200 nm.

7. The repair process according to claim 4, characterized in that, In step S200, the method for preparing the repair agent ointment includes the following steps: Step 1: Add ethyl cellulose to terpineol and stir at 60-80°C until completely dissolved to obtain a clear and transparent solution; then cool. Step 2: Mix the composite repair agent powder and dispersant evenly and add them to the solution obtained in Step 1. Continue stirring until a uniform paste is formed. Step 3: Grind the above paste into a fine and uniform paste, remove air bubbles under a vacuum of -0.095MPa or higher for 3-5 minutes, and filter through a 200-400 mesh sieve to obtain the repair agent paste.

8. The repair process according to claim 1, characterized in that, In step S200, the heating temperature is 138~200℃; the conditions for the gradient pulsed magnetic field are: 2.0~3.5T pulsed magnetic field, field strength gradient >50T / m, pulse frequency 1~5Hz; the frequency of ultrasonic vibration is 20~40kHz, and the amplitude is 1-5μm.

9. The repair process according to claim 1, characterized in that, In step S300, the cooling process is carried out in two steps: first, the temperature is rapidly cooled to 95~105℃ at a rate of 10-15℃ / s, and then slowly cooled to 20~30℃.

10. The repair process according to claim 1, characterized in that, In step S300, the aging treatment conditions include: holding at 150-180℃ for 1-2 hours.

Images