Permanent magnet stabilizing method and permanent magnet

Abstract

The application relates to a permanent magnet stabilizing method and a permanent magnet. The permanent magnet stabilizing method comprises the following steps: magnetizing the permanent magnet to a saturation state; and partially demagnetizing the permanent magnet in the saturation state, wherein the demagnetization amount is less than or equal to 21%, and the apparent magnetic domain size after demagnetization is 0.1-1.0 mu m. The permanent magnet stabilizing method is used to eliminate the unstable state of the magnetic domain, make the magnetic moment deflect to a stable state in advance, greatly reduce the natural magnetic loss, and improve the time stability of the permanent magnet from the perspective of stabilizing the magnetic domain. The partial demagnetization stabilizing method is simple, efficient, and remarkable, and is favorable for improving the use precision and stability of key magnetic devices.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of permanent magnets, in particular to a permanent magnet stabilization method and a permanent magnet. BACKGROUND

[0002] The internal microstructure of permanent magnet material is not uniform, and the internal stress caused by magnetization, machining and other processing operations will cause natural magnetic loss of the permanent magnet material, that is, the magnetic properties of the permanent magnet will gradually weaken over time and with changes in external conditions; the instability of natural magnetic loss will affect the reliability of the permanent magnet material, which is not conducive to the application of the permanent magnet material.

[0003] The traditional stabilization method is to realize stabilization by demagnetization through heat preservation, high temperature, cold and hot cycle and other methods, which is essentially an aging method. The principle is to release the internal stress in the permanent magnet in advance to make the magnetism of the permanent magnet tend to be stable, avoid the release of the internal stress due to natural aging, and thus avoid the occurrence of demagnetization.

[0004] The above-mentioned demagnetization method through artificial aging mostly limits the processing technology, such as limiting the heating temperature, holding time or cold and hot cycle interval and other parameters. However, due to the different individual magnetic properties of the permanent magnet, the stabilization performance of the permanent magnet processed by such processing method has batch fluctuations and individual fluctuations, which cannot be applied to the fields such as aerospace and national defense which have high requirements on the stabilization performance. SUMMARY

[0005] Therefore, it is necessary to provide a permanent magnet stabilization method and a permanent magnet which can stably obtain high stabilization effect to solve the problem that the stabilization effect of the current stabilization method is affected by the individual magnetic properties of the permanent magnet and cannot meet the requirements of the fields such as aerospace and national defense.

[0006] The present application first provides a permanent magnet stabilization method, which comprises the following steps:

[0007] The permanent magnet is magnetized to a saturated state.

[0008] The permanent magnet in the saturated state is partially demagnetized, and the demagnetization amount is less than or equal to 21%, and the apparent domain size after demagnetization is 0.1-1.0 μm.

[0009] The permanent magnet stabilizing method, from the perspective of stabilizing magnetic domains, performs partial demagnetization by limiting demagnetization amount and apparent magnetic domain size to eliminate unstable state of magnetic domains, so that magnetic moment is deflected to stable state in advance, natural magnetic loss is greatly reduced, and time stability of the permanent magnet is improved. The partial demagnetization stabilizing method performs demagnetization by limiting demagnetization amount and apparent magnetic domain size, so that the apparent magnetic domains of the permanent magnet can be widened and merged to a relatively stable state, and therefore is not affected by individual magnetic properties of the permanent magnet, has strong universality, is simple and efficient, has remarkable effect, and is beneficial to improving use precision and stability of key magnetic devices.

[0010] In one embodiment, the permanent magnet in the saturated state is partially demagnetized, and the demagnetization amount is 7%-21%, and the apparent magnetic domain size is 0.5 μm-1.0 μm.

[0011] It can be understood that, in the demagnetization amount range and the apparent magnetic domain size range, the permanent magnet after demagnetization has low natural magnetic loss, strong magnetic stabilization performance, and strong magnetic properties, and can meet normal use requirements of the permanent magnet.

[0012] In one embodiment, the permanent magnet in the saturated state is partially demagnetized by an alternating pulse magnetic field or a direct current magnetic field.

[0013] It can be understood that, by demagnetizing through an external magnetic field, the demagnetization time can be greatly reduced, and the demagnetization efficiency is increased.

[0014] In one embodiment, the alternating pulse magnetic field demagnetization and the direct current magnetic field demagnetization each include the following steps:

[0015] The demagnetization curve of the permanent magnet is measured by a BH instrument;

[0016] The residual magnetism Br of the permanent magnet is determined according to the required demagnetization amount of the permanent magnet, and the residual magnetism Br=100%-demagnetization amount;

[0017] The demagnetization field H1 corresponding to the residual magnetism Br is determined according to the demagnetization curve;

[0018] H1 is referenced, and the verification test is repeated until the size of the alternating demagnetization field H2 or the direct current demagnetization field H3 is determined;

[0019] The permanent magnet is demagnetized according to the alternating demagnetization field H2 or the direct current demagnetization field H3.

[0020] In one embodiment, in the step of referencing H1 and repeating the verification test until the size of the alternating demagnetization field H2 or the direct current demagnetization field H3 is determined, the following steps are further included:

[0021] The permanent magnet is demagnetized according to the demagnetization field H1;

[0022] The residual magnetism Br1 of the permanent magnet after demagnetization is tested, if Br1 = Br, the demagnetization field H1 is the alternating demagnetization field H2 or the direct current demagnetization field H3, if Br1 ≠ Br, the permanent magnet is magnetized, the demagnetization field H1 is adjusted according to the difference between Br1 and Br, and then the demagnetization is performed again, and the step is repeated until Br1 = Br.

[0023] In one embodiment, the step of demagnetizing the permanent magnet according to the alternating demagnetization field H2 further comprises the following steps:

[0024] The permanent magnet is placed in the demagnetization tooling of the magnetizing machine;

[0025] The magnetizing machine mode is set to the demagnetization mode;

[0026] The demagnetization voltage V is set, V = 760 * H2;

[0027] The magnetizing machine performs capacitor charging and discharging to complete the demagnetization.

[0028] In one embodiment, the step of demagnetizing the permanent magnet according to the direct current demagnetization field H3 further comprises the following steps:

[0029] The permanent magnet is placed in the BH instrument;

[0030] The direct current demagnetization field of the BH instrument is set to 15A / m-75A / m according to the direct current demagnetization field H3;

[0031] The BH instrument is started to complete the demagnetization.

[0032] In one embodiment, in the step of placing the permanent magnet in the BH instrument, the orientation direction of the permanent magnet is parallel to the pole head.

[0033] In one embodiment, the material of the permanent magnet is selected from an alnico magnet.

[0034] It can be understood that the time stability of the alnico magnet is stronger, and the high requirements of the aerospace and national defense fields on the time stability of the permanent magnet can be better met.

[0035] The second aspect of the application provides a permanent magnet, the material of the permanent magnet is selected from an alnico magnet, and the apparent domain size of the permanent magnet is 0.1μm-1.0μm. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0037] Figure 1 Flowchart of the permanent magnet stabilizing method of the present application;

[0038] Figure 2 Apparent magnetic domain structure of the permanent magnet 124 days after the first group of experiments in Example 1;

[0039] Figure 3 Apparent magnetic domain structure of the permanent magnet 124 days after the fourth group of experiments in Example 1;

[0040] Figure 4 Magnetic flux change schematic diagram of the four groups of experiments in Example 1;

[0041] Figure 5 Flowchart of the permanent magnet stabilizing method of the present application;

[0042] Figure 6 Demagnetization curve schematic diagram of an Al-Ni-Co magnet;

[0043] Figure 7 Demagnetization curve schematic diagram of a Sm-Co magnet;

[0044] Figure 8 Flowchart of the permanent magnet stabilizing method of the present application;

[0045] Figure 9 Flowchart of the permanent magnet stabilizing method of the present application;

[0046] Figure 10 Flowchart of the permanent magnet stabilizing method of the present application. DETAILED DESCRIPTION

[0047] In order to make the above purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. In the following description, a lot of specific details are set forth in order to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the spirit of the present application, so the present application is not limited to the specific embodiments disclosed below.

[0048] It is to be understood that when an element such as a layer, region or substrate is referred to as being "on" or "connected to" another element, it can be directly on or connected to the other element or intervening elements can be present. In contrast, when an element such as a layer, region or substrate is referred to as being "directly on" or "directly connected to" another element, there are no intervening elements present. It will be understood that, when a layer is referred to as being "formed on" or "formed over" another layer, it can be directly formed on or over the other layer or intervening layers can be present. Like numbers refer to like elements throughout.

[0049] In addition, the terms "first", "second", etc. are used herein only to describe different instances, and do not imply a relative importance or a number of the indicated technical features. Thus, the features defined with "first", "second", etc. can include at least one of the features explicitly or implicitly. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise explicitly and specifically limited.

[0050] In the present application, unless otherwise explicitly specified and limited, the "on", "under", "above" and "over" of a first feature to a second feature can be that the first feature is directly in contact with the second feature, or the first feature is indirectly in contact with the second feature through an intermediate medium. Moreover, the "on", "above" and "over" of a first feature to a second feature can be that the first feature is directly above or obliquely above the second feature, or only means that the first feature is higher than the second feature in horizontal height. The "under", "below" and "under" of a first feature to a second feature can be that the first feature is directly below or obliquely below the second feature, or only means that the first feature is lower than the second feature in horizontal height.

[0051] Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the present application is for the purpose of describing a specific embodiment only and is not intended to be limiting of the present application. The use of the term "and / or" in the description of the present application includes any and all combinations of one or more of the associated listed items.

[0052] Please refer to Figure 1 As shown, the present application first provides a permanent magnet stabilizing method, comprising the following steps:

[0053] S100, magnetizing the permanent magnet to a saturation state;

[0054] S200, partially demagnetizing the permanent magnet in the saturation state, the demagnetization amount is less than or equal to 21%, and the apparent domain size after demagnetization is 0.1 μm-1.0 μm.

[0055] Compared with the prior art, the method is started from the aspect of stabilizing magnetic domains, eliminates the unstable state of the magnetic domains by partial demagnetization, makes the magnetic moments of the magnetic domains deflect to a stable state in advance, greatly reduces natural magnetic loss, and improves the time stability of the permanent magnet. The partial demagnetization and magnet stabilization method has strong universality, is simple and efficient, and has remarkable effects, and is beneficial to improving the use precision and stability of key magnetic devices.

[0056] In some embodiments, in the step of performing partial demagnetization on the permanent magnet in the saturated state, the demagnetization amount ranges from 7% to 21%, and the apparent magnetic domain size after demagnetization is 0.5 μm to 1.0 μm.

[0057] In some embodiments, in the step of performing partial demagnetization on the permanent magnet in the saturated state, the demagnetization is performed by an alternating current pulse magnetic field or a direct current magnetic field.

[0058] The high-temperature thermal demagnetization and the current common heat preservation, cold-heat cycle and other demagnetization means are essentially an aging method. The principle is to release the internal stress in the permanent magnet in advance, so that the magnetism of the permanent magnet tends to be stable, and the release of the internal stress caused by natural aging is avoided, and the demagnetization is thus avoided.

[0059] The high-temperature thermal demagnetization generally heats the permanent magnet at 500-700 ℃ for 10-30 min, and then cools the permanent magnet with the furnace, and the cooling time is usually more than 12 h. The artificial aging heat preservation magnet stabilization method generally heats the magnet at 100-200 ℃ for 8-10 h. The high-low temperature cold-heat cycle magnet stabilization method generally places the magnet in a high-low temperature test box, and one high-low temperature cycle generally needs 5-10 h, and the number of magnetic ring cycles is 2-3 times. That is, the magnet stabilization method by artificial aging to release the internal stress needs a relatively long period and has low efficiency.

[0060] The demagnetization by the alternating current pulse magnetic field or the direct current magnetic field can greatly reduce the demagnetization time and increase the demagnetization efficiency.

[0061] In some embodiments, in the step of performing partial demagnetization on the permanent magnet in the saturated state, the demagnetization is performed by a direct current magnetic field. As shown in Tables 1 and 2, under the same conditions, the natural magnetic loss of the second embodiment using the direct current magnetic field demagnetization is smaller than that of the third embodiment using the high-temperature thermal demagnetization, and the natural magnetic loss of the first embodiment using the alternating current pulse magnetic field demagnetization is the smallest. Therefore, the direct current magnetic field demagnetization not only has shorter demagnetization time and higher efficiency, but also has better magnet stabilization effect.

[0062] Please refer to Figure 5 , Figure 6 and Figure 7As shown, in some embodiments, the alternating pulse magnetic field demagnetization and the direct current magnetic field demagnetization each include the following steps:

[0063] S210, measuring the demagnetization curve of the permanent magnet by a BH instrument;

[0064] S220, determining the residual magnetization Br of the permanent magnet according to the required demagnetization amount of the permanent magnet, the residual magnetization Br = 100% - demagnetization amount;

[0065] S230, determining the size of the demagnetization field H1 corresponding to the residual magnetization Br according to the demagnetization curve;

[0066] S240, referring to H1, repeating the verification test until the size of the alternating demagnetization field H2 or the direct current demagnetization field H3 is determined;

[0067] S250, demagnetizing the permanent magnet according to the alternating demagnetization field H2 or the direct current demagnetization field H3.

[0068] Please refer to Figure 8 As shown, in some embodiments, in the step of repeating the verification test until the size of the alternating demagnetization field H2 or the direct current demagnetization field H3 is determined by referring to H1, the following steps are further included:

[0069] S241, demagnetizing the permanent magnet according to the demagnetization field H1;

[0070] S242, checking the residual magnetization Br1 of the permanent magnet after demagnetization, if Br1 = Br, then the demagnetization field H1 is the alternating demagnetization field H2 or the direct current demagnetization field H3; if Br1 ≠ Br, then the permanent magnet is magnetized, the demagnetization field H1 is adjusted according to the difference between Br1 and Br, and then the demagnetization is performed again, and the step is repeated until Br1 = Br.

[0071] Please refer to Figure 9 As shown, in some embodiments, in the step of demagnetizing the permanent magnet according to the alternating demagnetization field H2, the following steps are further included:

[0072] S251a, placing the permanent magnet in the demagnetization tool of the magnetizing machine;

[0073] S252a, setting the magnetizing machine mode to the demagnetization mode;

[0074] S253a, setting the demagnetization voltage V, V = 760 × H2;

[0075] S254a, the magnetizing machine performs capacitor charging and discharging to complete demagnetization.

[0076] Please refer to Figure 10 As shown, in some embodiments, in the step of demagnetizing the permanent magnet according to the direct current demagnetization field H3, the following steps are further included:

[0077] S251b, placing the permanent magnet in the BH instrument;

[0078] S252b, setting the DC demagnetizing field of the BH instrument to 15 A / m-75 A / m according to the DC demagnetizing field H3;

[0079] S253b, starting the BH instrument to complete demagnetization.

[0080] In some embodiments, in the step of placing the permanent magnet in the BH instrument, the orientation direction of the permanent magnet is parallel to the pole head.

[0081] In some embodiments, the material of the permanent magnet is selected from Alnico magnets.

[0082] Although rare earth permanent magnet materials have replaced Alnico magnets in many application fields due to their excellent residual magnetism and magnetic energy product, etc., Alnico magnets have irreplaceable role in the field of magnetic materials due to their excellent temperature stability (temperature coefficient 0.02% / ℃), time stability, easy magnetization, good processability, and high temperature use (working temperature 550℃). The reason is that Alnico magnets belong to cobalt-based permanent magnet materials, and the atomic magnetic moment of cobalt is smaller than that of iron, so the Curie temperature of Alnico magnets is higher than that of neodymium-iron-boron magnets, and the temperature stability is better.

[0083] In the present application, Alnico magnets are selected to further increase the time stability of the permanent magnet after the completion of the magnetic stabilization, so as to meet the high requirements of aerospace and national defense fields for the time stability of the permanent magnet.

[0084] The second aspect of the present application provides a permanent magnet, the material of the permanent magnet is selected from Alnico magnets, and the apparent domain size of the permanent magnet is 0.1 μm-1.0 μm.

[0085] Next, eight groups of test results of four embodiments are used as examples, Table 1 is the permanent magnet parameters of the eight groups of experiments, and Table 2 is the demagnetization related parameters corresponding to the eight groups of experiments and the magnetic loss of the permanent magnet after the completion of demagnetization.

[0086] Table 1

[0087]

[0088]

[0089] Table 2

[0090]

[0091] Embodiment one:

[0092] In this embodiment, the permanent magnet is an AlNiCo 8 type (Br = 10.5 kGs, Hcb = 1600 Gs, (BH)max = 11 MGOe) prepared by casting. The magnet is machined into a φ10mm*10mm cylinder, with the axial direction of the cylinder being the orientation direction. Using a BH instrument, the demagnetization curve of the permanent magnet is measured, and the magnetic properties of the magnet are calculated. The magnitude of the demagnetization field is calculated based on the required demagnetization amount. In Example 1, 12 permanent magnet samples were prepared, divided into 4 groups of 3 samples each. Group 1 was a blank control sample and was not demagnetized. Groups 2, 3, and 4 were demagnetized.

[0093] All samples were magnetized under a 1T magnetic field, ensuring each sample was fully saturated. The second group of samples was then placed in a demagnetizing fixture and partially demagnetized under a 30mT AC pulsed magnetic field, achieving a demagnetization rate of 7% (6%–8% acceptable, considering individual variations). The third group of samples was placed in the demagnetizing fixture and partially demagnetized under a 45mT AC pulsed magnetic field, achieving a demagnetization rate of 14% (13%–15% acceptable, considering individual variations). The fourth group of samples was placed in the demagnetizing fixture and partially demagnetized under a 60mT AC pulsed magnetic field, achieving a demagnetization rate of 21% (20%–22% acceptable, considering individual variations). The magnetic flux value of each group of samples was measured, and the average value was recorded. The original magnetic flux of the first group was denoted as... The original magnetic flux of group 2 is denoted as The original magnetic flux of group 3 is denoted as The original magnetic flux of group 4 is denoted as The magnetic flux values ​​of four sets of samples were measured and recorded daily thereafter. The first day was recorded as... as well as This process was repeated for one month; after one month, the magnetic flux values ​​of four sets of samples were measured and recorded every month thereafter; the samples were stored in a constant-temperature test room at 20°C and ≤50% RH.

[0094] The natural magnetic loss of the permanent magnet was calculated according to formula (1), and the results are shown in Table 2.

[0095]

[0096] Please refer to Figure 2 as well as Figure 3 As shown, on day 124, apparent magnetic domains of the samples were analyzed using magnetic force microscopy (MFM). It was found that some demagnetized samples exhibited domain merging and broadening, transforming from sharp peaks to rounded peaks. The apparent domain sizes of the demagnetized samples ranged from 0.5 μm to 1 μm, and the natural magnetic loss was less than 1.2% in all cases.

[0097] Example 2:

[0098] In this example, the permanent magnet is an Al-Ni-Co 8 type permanent magnet (Br = 10.5 kGs, Hcb = 1600 Gs, (BH)max = 11 MGOe) prepared by a casting process. The magnet is processed into a cylinder with a diameter of 10 mm and a length of 10 mm, and the axial direction of the cylinder is the orientation direction. A BH instrument is used to measure the demagnetization curve of the permanent magnet, and the magnetic properties of the magnet are calculated. The demagnetization field size of each sample is calculated according to the required demagnetization amount. Three permanent magnet samples are prepared in Example 2.

[0099] All samples are magnetized under a magnetic field of 1 T to ensure that each sample is saturated. Then the samples are placed in a BH instrument, and a direct current demagnetization field of 75 A / m is applied for partial demagnetization. The demagnetization amount of the sample is 14%, and considering individual fluctuations, the allowable range is 13% to 15%. The magnetic flux value of each sample is measured and averaged, denoted as The sample magnetic flux value is measured and recorded every day, denoted as wherein, is the magnetic flux value after one day, is the magnetic flux value after two days, and so on; after one month, the sample magnetic flux value is measured and recorded every other month. The samples are stored in a constant temperature test room with a temperature of 20°C and a humidity of ≤50% rh. The natural magnetic loss of the permanent magnet is calculated according to formula (1), and the results are shown in Table 2.

[0100] Example 3:

[0101] In this example, the permanent magnet is an Al-Ni-Co 8 type permanent magnet (Br = 10.5 kGs, Hcb = 1600 Gs, (BH)max = 11 MGOe) prepared by a casting process. The magnet is processed into a cylinder with a diameter of 10 mm and a length of 10 mm, and the axial direction of the cylinder is the orientation direction. A BH instrument is used to measure the demagnetization curve of the permanent magnet, and the magnetic properties of the magnet are calculated. The demagnetization field size of each sample is calculated according to the required demagnetization amount. Three permanent magnet samples are prepared in Example 3.

[0102] All samples are magnetized under a magnetic field of 1 T to ensure that each sample is saturated. Then the samples are placed in a vacuum heat treatment furnace, and heated to 600°C for 30 min, and then cooled in the furnace. The entire heating field needs to be in a vacuum state, with a vacuum degree less than or equal to 10 -3 Pa. The demagnetization amount of the sample is 7%, and considering individual fluctuations, the allowable range is 6% to 8%. The magnetic flux value of each sample is measured and averaged, denoted as The sample magnetic flux value is measured and recorded every day, denoted as wherein, is the magnetic flux value after one day, The magnetic flux value is recorded two days later, and so on; after one month, the magnetic flux value of the sample is measured and recorded every month. The sample is stored in a constant temperature test room, with a temperature of 20℃ and a humidity of ≤50%rh. The natural magnetic loss of the permanent magnet is calculated according to formula (1), and the results are shown in Table 2.

[0103] Example 4:

[0104] In this embodiment, the permanent magnet is a samarium cobalt permanent magnet (Mr = 8.50 kGs, Hcj = 23.00 kGs, (BH)m = 18.00 MGOe) prepared by powder metallurgy. The magnet is machined into a cylinder with a diameter of φ10 mm * 10 mm, with the axial direction of the cylinder being the orientation direction. Using a BH instrument, the demagnetization curve of the permanent magnet is measured, the magnetic properties of the magnet are calculated, and the magnitude of the demagnetization field is calculated based on the required demagnetization amount. Three permanent magnet samples are prepared in Example 4.

[0105] All samples were magnetized under a 7.5T magnetic field, ensuring each sample was fully saturated. One sample was selected without demagnetization and designated as Group 1. Two samples were then selected as Group 2 and placed in a demagnetization fixture for partial demagnetization under a 4T AC pulsed magnetic field. The demagnetization amount was 7%, with an allowable range of 6%–8% to account for individual variations. The magnetic flux of each sample was measured. The undemagnetized sample was recorded as... The average magnetic flux of the two demagnetized samples is denoted as . The magnetic flux values ​​of four sets of samples were measured and recorded daily thereafter. The first day was recorded as... and This process was repeated for one month; after one month, the magnetic flux values ​​of four groups of samples were measured and recorded every month thereafter; the samples were stored in a constant-temperature test room at 20°C and ≤50% RH. The natural magnetic loss of the permanent magnet was calculated according to formula (1), and the results are shown in Table 2.

[0106] As can be seen from the four sets of experimental results in Example 1, by limiting the amount of demagnetization and the apparent magnetic domain size after demagnetization, the natural magnetic loss in the second, third, and fourth sets of experiments is significantly reduced compared to the natural magnetic loss in the first set of experiments.

[0107] Meanwhile, by observing the demagnetization range of the four groups of experiments in Tables 1 and 2 and the natural magnetic loss over 124 days, it can be seen that when the demagnetization amount gradually increases in the four groups of experiments, the reduction in natural magnetic loss gradually decreases. This means that the method of eliminating magnetic domain instability through partial demagnetization has a marginal effect. If the demagnetization amount is too large, not only will the effect on reducing natural magnetic loss be poor, but it will also lead to the permanent magnet having too low magnetism, thus affecting the normal use of the permanent magnet.

[0108] Furthermore, through observation Figure 4It can be seen that the boundary value of the natural magnetic loss reduction is about 1%, thus, when the demagnetization is less than 21% and the apparent magnetic domain size after demagnetization is 0.1-1.0 μm, the obtained permanent magnet not only has lower natural magnetic loss and stronger stable magnetic performance, but also has stronger magnetic performance, which can meet the normal use requirements of the permanent magnet.

[0109] In addition, according to the experiment of Example Four, it can be seen that the natural magnetic loss of the samarium-cobalt magnet is also significantly reduced after quantitative demagnetization according to the method, which proves that the effect of the method on the stable magnetic domain structure is effective for different types of permanent magnets.

[0110] The technical features of the above-described embodiments can be combined arbitrarily, and to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the description.

[0111] The above-described embodiments only express several implementation manners of the application, the description is more specific and detailed, but it should not be understood as a limitation on the patent application scope. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the application, a number of modifications and improvements can be made, which all belong to the protection scope of the application. Therefore, the patent protection scope of the application should be subject to the appended claims.

Claims

1. A method of stabilizing a magnetic field with permanent magnets, characterized in that, The method comprises the following steps: magnetizing the permanent magnet to a saturation state; partially demagnetizing the permanent magnet in the saturation state by AC pulse magnetic field demagnetization or DC magnetic field demagnetization, the demagnetization amount ranges from 7% to 21%, and the apparent magnetic domain size after demagnetization ranges from 0.5 μm to 1.0 μm; the AC pulse magnetic field demagnetization and the DC magnetic field demagnetization both comprise the following steps: measuring the demagnetization curve of the permanent magnet by a BH instrument; determining the residual magnetism Br of the permanent magnet according to the required demagnetization amount, wherein the residual magnetism Br = 100% - demagnetization amount; determining the demagnetization field H1 corresponding to the residual magnetism Br according to the demagnetization curve; repeating the verification test by referring to H1 until the size of the AC demagnetization field H2 or the DC demagnetization field H3 is determined; demagnetizing the permanent magnet according to the AC demagnetization field H2 or the DC demagnetization field H3; in the step of repeating the verification test by referring to H1 until the size of the AC demagnetization field H2 or the DC demagnetization field H3 is determined, the method further comprises the following steps: demagnetizing the permanent magnet according to the demagnetization field H1; checking the residual magnetism Br1 of the permanent magnet after demagnetization, wherein if Br1 = Br, the demagnetization field H1 is the AC demagnetization field H2 or the DC demagnetization field H3, and if Br1 ≠ Br, the permanent magnet is magnetized again, the demagnetization field H1 is adjusted according to the difference between Br1 and Br, and the step is repeated until Br1 = Br.

2. The permanent magnet stabilizing method according to claim 1, characterized by, in the step of demagnetizing the permanent magnet according to the AC demagnetization field H2, the method further comprises the following steps: placing the permanent magnet in a demagnetization tool of a magnetizing machine; setting the magnetizing machine to a demagnetization mode; setting the demagnetization voltage V, wherein V = 760 × H2; performing capacitor charging and discharging by the magnetizing machine to complete the demagnetization.

3. The permanent magnet stabilizing method according to claim 1, characterized by, in the step of demagnetizing the permanent magnet according to the DC demagnetization field H3, the method further comprises the following steps: placing the permanent magnet in a BH instrument; setting the DC demagnetization field of the BH instrument to 15 A / m-75 A / m according to the DC demagnetization field H3; starting the BH instrument to complete the demagnetization.

4. The permanent magnet stabilizing method according to claim 3, characterized by, in the step of placing the permanent magnet in the BH instrument, the orientation direction of the permanent magnet is parallel to the pole head.

5. The permanent magnet stabilization method according to claim 1, characterized by, the material of the permanent magnet is selected from an alnico magnet.

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