A method for producing a bonded magnet having a low magnetic energy product and a high coercivity

Abstract

The application discloses a preparation method of a bonded magnet with low magnetic energy product and high coercivity, and steps are as follows: dissolving magnetic powder into an organic solvent to obtain a glue solution; adding the glue solution into strontium ferrite magnetic powder, and heating and stirring at a rotating speed of 15-30 r / min; then adding neodymium-iron-boron magnetic powder, continuing to stir, adjusting the rotating speed to 10-20 r / min, and vacuumizing to a vacuum degree of 0.08-0.1 Pa; stopping vacuumizing, adjusting the rotating speed to 50-60 r / min, cooling to 5±5 DEG C, and continuing to stir to obtain mixed magnetic powder; crushing and screening the mixed magnetic powder, and then performing die molding; and sequentially performing heating and solidifying, epoxy resin surface treatment and magnetizing on the molded product. The application effectively combines dry mixing and wet mixing, obtains mixed magnetic powder with uniform mixing, the finished magnet meets the requirements, realizes continuous adjustment of the magnetic energy product while keeping high coercivity, and greatly improves the performance-price ratio of the magnetic powder.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bonded neodymium-iron-boron magnet preparation, in particular to a preparation method of a bonded magnet with low magnetic energy product and high coercivity. BACKGROUND

[0002] The traditional process steps of bonded neodymium-iron-boron magnet molding are: mixing, pressing, curing, surface treatment, and magnetizing. The related process technology is developed and improved based on the use of 100% rapidly quenched neodymium-iron-boron magnetic powder. With the expansion of the application field of bonded magnets, more requirements are put forward for the performance of the magnets, and the magnets made of 100% neodymium-iron-boron magnetic powder begin to appear the situation of not meeting the requirements. On this basis, composite magnetic powder has been widely studied and applied.

[0003] In the application of ferrite and neodymium-iron-boron composite powder, the performance of neodymium-iron-boron powder is much higher than that of strontium ferrite powder, the maximum magnetic energy product (BH)max of bonded neodymium-iron-boron powder is 6-12 MGOe, while the maximum magnetic energy product (BH)max of sintered ferrite is 4.5 MGOe, but the price of neodymium-iron-boron powder is 100-300 yuan / ton, and the price of ferrite magnet is 0.3-0.7 yuan / ton. The high price of raw materials greatly limits the popularization and application of bonded neodymium-iron-boron. Through the substitution of raw materials, under the premise of ensuring that the magnetic performance meets the requirements, the cost of materials is reduced, and the performance-price ratio is improved, which becomes an important way for the popularization and application of bonded neodymium-iron-boron. The substituted materials include copper powder, zinc powder, ferrite powder, etc. The most widely used method is to replace part of neodymium-iron-boron with ferrite, for example, the ferrite neodymium-iron-boron mixed magnet and its preparation method disclosed in patent CN117690682A, which combines ferrite magnetic powder and neodymium-iron-boron magnetic powder to improve the comprehensive magnetic performance of the magnet and reduce the manufacturing cost.

[0004] However, the existing technology generally uses ball milling mixing + spray granulation method to pretreat the composite magnetic powder. Due to the different characteristics of ferrite magnetic powder and neodymium-iron-boron magnetic powder, it is difficult to mix uniformly. The ferrite powder is spherical with an average particle size of 0.8-6 μm and a density of about 4.0 g / cm 3 ; while the neodymium-iron-boron powder is flaky with an average particle size of 20-35 μm and a density of about 7.0 g / cm 3; Ferrite magnetic powder is light and thin compared with Nd-Fe-B magnetic powder, which leads to difficulty in mixing, obvious stratification and difficulty in guaranteeing consistency of magnetic properties. This results in large difference in magnetic properties of different products, large demagnetization rate of products, and large difference in filling characteristics of magnetic powder between different parts of the same batch of magnetic powder, mainly reflected in powder flowability and bulk specific gravity. Under the same mold cavity, sometimes filling is fast and sometimes filling is slow, which leads to unstable pressing, unsmooth continuous pressing, frequent die jamming and over / under-pressing. After uniform mixing, local magnet strength is also affected, and local magnetic powder particles are fine and magnetic powder glue is less, which leads to low magnet strength, edge and corner defects and large variation in crushing strength of products. Moreover, strontium ferrite powder is an oxide and Nd-Fe-B magnetic powder is an alloy, and the difference in surface energy is large, so uneven mixing leads to different film thickness after electrophoretic coating of epoxy resin paint, thereby leading to rusting of products in salt spray test and inability to guarantee corrosion resistance. SUMMARY

[0005] The present application is to overcome the above-mentioned problems existing in the production process of ferrite Nd-Fe-B mixed magnets in the prior art, and provides a preparation method of a bonded magnet with low magnetic energy product and high coercivity. The dry method and the wet method are effectively combined to obtain uniformly mixed magnetic powder, and the finished magnet meets the requirements, realizes continuous adjustment of magnetic energy product while maintaining high coercivity, and greatly improves the performance-price ratio of the magnetic powder.

[0006] In order to achieve the above-mentioned purpose, the following technical solutions are adopted in the present application:

[0007] A preparation method of a bonded magnet with low magnetic energy product and high coercivity, comprising the following steps:

[0008] (1) dissolving the magnetic powder glue in an organic solvent to obtain a glue solution;

[0009] (2) adding the glue solution into strontium ferrite magnetic powder, stirring at a speed of 15-30 r / min at 40±5℃ for 10-20 min;

[0010] (3) adding Nd-Fe-B magnetic powder, stirring under the same conditions for 15-25 min, then adjusting the speed to 10-20 r / min, and vacuumizing to a vacuum degree of 0.08-0.1 Pa; stopping vacuumizing, adjusting the speed to 50-60 r / min, cooling to 5±5℃, and continuing to stir for 5-15 min to obtain mixed magnetic powder; the added strontium ferrite magnetic powder is 0-70% of the mass of the Nd-Fe-B magnetic powder;

[0011] (4) crushing and screening the mixed magnetic powder and then performing mold pressing;

[0012] (5) sequentially performing heating and curing, epoxy resin surface treatment and magnetization on the pressed product.

[0013] The present application mixes strontium ferrite magnetic powder and neodymium iron boron magnetic powder by dry-wet combination method. In the mixing process of the magnetic powder, the strontium ferrite magnetic powder and the glue solution are stirred and mixed first, and the stirring speed is controlled properly to make the glue solution penetrate slowly, so that the magnetic powder glue can contact with the magnetic powder uniformly. When the stirring speed is too slow, the magnetic powder flows too slowly, the glue solution is difficult to penetrate uniformly, and the magnetic powder glue and the magnetic powder cannot be mixed uniformly. When the stirring speed is too fast, the local magnetic powder agglomerates easily, and the mixing of the magnetic powder and the magnetic powder glue is also not uniform. At the same time, the present application also heats in the stirring process to make the organic solvent in the glue solution volatilize slowly. By controlling the heating temperature and the stirring time, the volatilization amount of the organic solvent is controlled, so that the humidity of the magnetic powder glue on the surface of the strontium ferrite magnetic powder is kept in a proper state. If the organic solvent is not fully volatilized, the magnetic powder glue is always in liquid state and cannot be adsorbed on the surface of the magnetic powder to solidify. If the organic solvent volatilizes too much, the magnetic powder glue has been fully solidified on the surface of the magnetic powder, and the subsequent neodymium iron boron magnetic powder cannot be adsorbed.

[0014] After the strontium ferrite magnetic powder is mixed with the glue solution uniformly and the dry and wet humidity of the magnetic powder glue on the surface is adjusted to a proper state, the dry neodymium iron boron magnetic powder is added, and stirring and mixing are carried out at the same temperature and speed first. Since the neodymium iron boron magnetic powder is mostly in a sheet shape and several times larger than the strontium ferrite magnetic powder, under the action of stirring, the dry neodymium iron boron magnetic powder flows quickly, and the semi-wet and semi-dry strontium ferrite powder can be adhered to the surface of the dry neodymium iron boron magnetic powder uniformly, so that the two are uniformly compounded. The stirring speed in this process cannot be too slow, otherwise the magnetic powder cannot flow, which is not conducive to the uniform adhesion of the strontium ferrite magnetic powder on the surface of the neodymium iron boron magnetic powder. At the same time, the stirring speed cannot be too fast, otherwise the strontium ferrite magnetic powder with the magnetic powder glue adsorbed on the surface will agglomerate by itself and form a large block. After the strontium ferrite magnetic powder is uniformly adhered to the surface of the neodymium iron boron magnetic powder, the speed is adjusted lower, and vacuum is started to be pumped. Under the action of vacuum, the un-volatilized organic solvent in the glue solution can be completely volatilized, and the magnetic powder glue is solidified. Then the vacuum is stopped, cooling is started, and the stirring speed is adjusted higher to continue stirring. At low temperature, the magnetic powder can be further broken, and the mixed magnetic powder with the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder uniformly compounded is finally obtained.

[0015] The application can realize continuous adjustment of magnetic energy product while maintaining high coercivity by adjusting the proportion of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder, meets the requirements of different fields on magnetic properties, and improves the performance-price ratio of the product. If the proportion of the strontium ferrite magnetic powder is too small, the adjustable range of the magnetic powder performance is narrow, and it is not conducive to reducing the cost; and if the proportion of the strontium ferrite magnetic powder is too large, the strontium ferrite magnetic powder cannot be uniformly adhered to the surface of the neodymium iron boron magnetic powder, and uniform mixing cannot be realized. The application effectively combines dry mixing and wet mixing to realize uniform mixing of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder, and the bonded magnet prepared has good magnetic performance consistency, and the continuous pressing is smooth when the bonded magnet is molded, and the bonded magnet is not prone to die jamming, and the crushing strength of the bonded magnet changes little, and the bonded magnet is not prone to edge and corner defects. Meanwhile, the uniform mixing of the two kinds of magnetic powders can also ensure uniform adsorption of the surface epoxy resin, and the bonded magnet has good corrosion resistance and is not prone to rusting under salt spray test.

[0016] Preferably, the average particle size of the strontium ferrite magnetic powder is 400-600 mesh, and the average particle size of the neodymium iron boron magnetic powder is 100-250 mesh.

[0017] Preferably, the components of the magnetic powder glue in step (1) include, by weight, 2-3 parts of epoxy resin, 0.35-0.55 parts of curing agent, and 0.02-0.04 parts of coupling agent.

[0018] Preferably, the curing agent is dicyandiamide, and the coupling agent is KH550.

[0019] Preferably, the mass of the magnetic powder glue in the glue solution added is 1.5-3.0% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder, and the mass of the organic solvent is 5-10% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder. Too little magnetic powder glue added cannot meet the strength requirement of the product; too much magnetic powder glue added not only causes the magnetic performance per unit volume to decrease, but also easily causes overflow, resulting in poor appearance. Too little organic solvent causes part of the strontium ferrite magnetic powder to not be fully soaked with the organic solvent, the surface of the magnetic powder is less magnetic powder glue, and the magnetic powder is not uniformly mixed, resulting in low product strength; too much organic solvent causes the organic solvent to be difficult to fully volatilize, affecting the mixing effect.

[0020] Preferably, in step (4), the mixed magnetic powder is vibrated and broken by Φ10×10 stainless steel balls, and is sieved through a 40-80 mesh sieve.

[0021] Preferably, in step (4), the pressure during molding is 8-10T / cm. 2 .

[0022] Preferably, in step (5), the temperature during heating and curing is 180±10℃, and the curing time is 50±10min.

[0023] Preferably, the thickness of the surface epoxy resin layer in step (5) is 0.015-0.025 mm.

[0024] Therefore, the present application has the following advantages:

[0025] (1) The magnetic energy product is continuously adjustable in the range of 3.0-8.0 MGOe, and the coercivity is above 7 KOe, meeting the requirements of different fields for magnetic properties and improving the performance-price ratio of products;

[0026] (2) The dry-wet combined method is used for mixing, solving the problem of poor uniformity of magnetic properties due to the difficulty in mixing the strontium ferrite magnetic powder and the neodymium-iron-boron magnetic powder uniformly because of the difference in properties of the magnetic powders when the strontium ferrite magnetic powder is partially replaced by the neodymium-iron-boron magnetic powder;

[0027] (3) The problem of poor strength of the magnet, easy edge missing and corner dropping, and die jamming when the strontium ferrite and neodymium-iron-boron composite magnetic powder is molded is solved; DETAILED DESCRIPTION

[0028] The present application will be further described in combination with the specific embodiments.

[0029] In the present application, all the equipment and raw materials can be purchased from the market or commonly used in the industry, and the methods in the following examples are conventional methods in the field unless otherwise specified.

[0030] General embodiment:

[0031] A preparation method of a bonded magnet with low magnetic energy product and high coercivity, comprising the following steps:

[0032] (1) Dissolving the magnetic powder glue in an organic solvent to obtain a glue solution;

[0033] (2) Adding the glue solution into the strontium ferrite magnetic powder, stirring at a speed of 15-30 r / min at 40±5℃ for 10-20 min;

[0034] (3) Adding the neodymium-iron-boron magnetic powder, stirring under the same conditions for 15-25 min, adjusting the speed to 10-20 r / min, and vacuumizing to a vacuum degree of 0.08-0.1 Pa; stopping vacuumizing, adjusting the speed to 50-60 r / min, cooling to 5±5℃, and continuing to stir for 5-15 min to obtain the mixed magnetic powder; the added strontium ferrite magnetic powder is 0-70% of the mass of the neodymium-iron-boron magnetic powder;

[0035] (4) Crushing and sieving the mixed magnetic powder and then molding;

[0036] (5) Heating and curing the molded product, performing surface treatment with epoxy resin, and magnetizing in sequence.

[0037] As a specific embodiment, the average particle size of the strontium ferrite magnetic powder is 400-600 mesh, and the average particle size of the neodymium-iron-boron magnetic powder is 100-250 mesh.

[0038] As a specific embodiment, the components of the magnetic powder glue in step (1) include, by weight parts, 2-3 parts of epoxy resin, 0.35-0.55 parts of curing agent, and 0.02-0.04 parts of coupling agent.

[0039] As a specific embodiment, the curing agent is dicyandiamide, and the coupling agent is KH550.

[0040] As a specific embodiment, the mass of the magnetic powder glue added in the glue solution is 1.5-3.0% of the total mass of the strontium ferrite magnetic powder and the neodymium-iron-boron magnetic powder, and the mass of the organic solvent is 5-10% of the total mass of the strontium ferrite magnetic powder and the neodymium-iron-boron magnetic powder.

[0041] As a specific embodiment, in step (4), the mixed magnetic powder is vibrated and broken by Φ10×10 stainless steel balls, and sieved through a 40-80 mesh screen.

[0042] As a specific embodiment, in step (4), the pressure during the compression molding is 8-10 T / cm. 2 .

[0043] As a specific embodiment, in step (5), the temperature during the heating and curing is 180±10℃, and the curing time is 50±10 min.

[0044] As a specific embodiment, in step (5), the thickness of the surface epoxy resin layer is 0.015-0.025 mm.

[0045] Example 1:

[0046] A method for preparing a bonded magnet with low magnetic energy product and high coercivity, comprising the following steps:

[0047] (1) uniformly mix, by weight parts, 2.5 parts of epoxy resin W-6C, 0.03 parts of curing agent dicyandiamide, and 0.03 parts of silane coupling agent KH550 to obtain a magnetic powder glue;

[0048] (2) add the magnetic powder glue into acetone and stir to dissolve uniformly to obtain a glue solution;

[0049] (3) weigh the strontium ferrite magnetic powder (average particle size 500 mesh) and add it into a mixer, then add the glue solution, start stirring at a speed of 20 r / min; while stirring, heat the temperature in the container to 40℃, and stir for 15 min;

[0050] (4) then neodymium iron boron magnetic powder (brand 8-11, average particle size 200 mesh) is added into the mixer, and stirring is continued at a rotating speed of 20 r / min for 20 min; the rotating speed is adjusted to 15 r / min, and vacuumizing is continued until the vacuum degree is 0.09 Pa; the vacuumizing is stopped, the rotating speed is adjusted to 55 r / min, cooling water is passed to cool to 5℃, and stirring is continued for 10 min to obtain mixed magnetic powder; the added strontium ferrite magnetic powder is 5% of the mass of the neodymium iron boron magnetic powder, the mass of the magnetic powder glue in the glue solution is 2.0% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder, and the mass of the organic solvent is 8% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder;

[0051] (5) the mixed magnetic powder is broken by Φ10×10 stainless steel ball vibration, and is passed through a 60-mesh screen;

[0052] (6) the screened mixed magnetic powder is pressed into a Φ15×Φ9.8×8.45 mm ring through a mold under a pressing pressure of 10 T / cm 2

[0053] (7) the product after molding is heated and solidified at a temperature of 180℃ for 50 min;

[0054] (8) the product after solidification is subjected to surface treatment of electrophoretic epoxy resin (EP-703) with a film thickness of 0.020 mm;

[0055] (9) the product after surface treatment is subjected to magnetization to obtain the bonded magnet with low magnetic energy product and high coercivity.

[0056] Example 2:

[0057] A preparation method of a bonded magnet with low magnetic energy product and high coercivity, comprising the following steps:

[0058] (1) 2.5 parts of epoxy resin W-6C, 0.03 parts of curing agent dicyandiamide, and 0.03 parts of silane coupling agent KH550 are mixed uniformly to obtain magnetic powder glue;

[0059] (2) the magnetic powder glue is added into acetone, and is stirred and dissolved uniformly by a stirrer to obtain glue solution;

[0060] (3) strontium ferrite magnetic powder (average particle size 500 mesh) is weighed and added into the mixer, and then the glue solution is added, and stirring is started at a rotating speed of 15 r / min; at the same time, the temperature in the container is heated to 35℃, and stirring is continued for 20 min;

[0061] ​(4) then neodymium iron boron magnetic powder (brand 8-11, average particle size 200 mesh) is added into the mixer, and stirring is continued at a rotating speed of 15 r / min for 25 min; the rotating speed is adjusted to 10 r / min, and vacuum is extracted to a vacuum degree of 0.08 Pa; the vacuum extraction is stopped, the rotating speed is adjusted to 50 r / min, cooling water is passed to cool to 5℃, and stirring is continued for 15 min to obtain mixed magnetic powder; the added strontium ferrite magnetic powder is 5% of the mass of the neodymium iron boron magnetic powder, the mass of the magnetic powder glue in the glue solution is 2.0% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder, and the mass of the organic solvent is 8% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder;

[0062] (5) the mixed magnetic powder is broken by Φ10×10 stainless steel ball vibration, and is passed through a 60-mesh screen;

[0063] (6) under a pressing pressure of 10 T / cm 2 , the screened mixed magnetic powder is pressed into a circular ring with a size of Φ15×Φ9.8×8.45 mm through a mold;

[0064] (7) the product after molding is heated and solidified at a temperature of 180℃ for 50 min;

[0065] (8) the product after solidification is subjected to surface treatment of electrophoretic epoxy resin (EP-703) with a film thickness of 0.020 mm;

[0066] (9) the product after surface treatment is subjected to magnetization to obtain the bonded magnet with low magnetic energy product and high coercivity.

[0067] Example 3:

[0068] A preparation method of a bonded magnet with low magnetic energy product and high coercivity, comprising the following steps:

[0069] (1) 2.5 parts of epoxy resin W-6C, 0.03 parts of curing agent dicyandiamide, and 0.03 parts of silane coupling agent KH550 are mixed uniformly to obtain magnetic powder glue;

[0070] (2) the magnetic powder glue is added into acetone, and is stirred and dissolved uniformly by a stirrer to obtain glue solution;

[0071] (3) strontium ferrite magnetic powder (average particle size 500 mesh) is weighed and added into a mixer, and then the glue solution is added, and stirring is started at a rotating speed of 30 r / min; while stirring, the temperature in the container is heated to 45℃, and stirring is continued for 10 min;

[0072] (4) then neodymium iron boron magnetic powder (brand 8-11, average particle size 200 mesh) is added into the mixer, and stirring is continued at a rotating speed of 30 r / min for 15 min; the rotating speed is adjusted to 20 r / min, and stirring is continued, and vacuum is extracted to a vacuum degree of 0.1 Pa; the vacuum extraction is stopped, the rotating speed is adjusted to 60 r / min, cooling water is passed to cool to 5℃, and stirring is continued for 5 min, to obtain mixed magnetic powder; the strontium ferrite magnetic powder added is 5% of the mass of the neodymium iron boron magnetic powder, the mass of the magnetic powder glue in the glue solution is 2.0% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder, and the mass of the organic solvent is 8% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder;

[0073] (5) the mixed magnetic powder is broken by Φ10×10 stainless steel ball vibration, and is passed through a 60-mesh screen;

[0074] (6) under a pressing pressure of 10 T / cm 2 , the screened mixed magnetic powder is pressed into a circular ring with a size of Φ15×Φ9.8×8.45 mm through a mold;

[0075] (7) the product after molding is heated and solidified, the temperature is 180℃, and the time is 50 min;

[0076] (8) the product after solidification is subjected to surface treatment of electrophoretic epoxy resin (EP-703) with a film thickness of 0.020 mm;

[0077] (9) the product after surface treatment is subjected to magnetization, to obtain the bonded magnet with low magnetic energy product and high coercivity.

[0078] Example 4:

[0079] A preparation method of a bonded magnet with low magnetic energy product and high coercivity, comprising the following steps:

[0080] (1) 2.5 parts of epoxy resin W-6C, 0.03 parts of curing agent dicyandiamide, and 0.03 parts of silane coupling agent KH550 are mixed uniformly to obtain magnetic powder glue;

[0081] (2) the magnetic powder glue is added into acetone, and is stirred and dissolved uniformly by a stirrer to obtain glue solution;

[0082] (3) strontium ferrite magnetic powder (average particle size 500 mesh) is weighed and added into a mixer, then the glue solution is added, and stirring is started at a rotating speed of 20 r / min; while stirring, the temperature in the container is heated to 40℃, and stirring is continued for 15 min;

[0083] (4) then neodymium iron boron magnetic powder (brand 8-11, average particle size 200 mesh) is added into the mixer, and stirring is continued at a rotating speed of 20 r / min for 20 min; the rotating speed is adjusted to 15 r / min, and vacuumizing is continued until the vacuum degree is 0.09 Pa; the vacuumizing is stopped, the rotating speed is adjusted to 55 r / min, cooling water is passed to cool to 5℃, and stirring is continued for 10 min to obtain mixed magnetic powder; the added strontium ferrite magnetic powder is 10% of the mass of the neodymium iron boron magnetic powder, the mass of the magnetic powder glue in the glue solution is 2.0% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder, and the mass of the organic solvent is 8% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder;

[0084] (5) the mixed magnetic powder is broken by Φ10×10 stainless steel ball vibration, and is passed through a 60-mesh screen;

[0085] (6) under a pressing pressure of 10 T / cm 2 , the screened mixed magnetic powder is pressed into a circular ring with a size of Φ15×Φ9.8×8.45 mm through a mold;

[0086] (7) the product after molding is heated and solidified at a temperature of 180℃ for 50 min;

[0087] (8) the product after solidification is subjected to surface treatment of electrophoretic epoxy resin (EP-703) with a film thickness of 0.020 mm;

[0088] (9) the product after surface treatment is subjected to magnetization to obtain the bonded magnet with low magnetic energy product and high coercivity.

[0089] Example 5:

[0090] A preparation method of a bonded magnet with low magnetic energy product and high coercivity, comprising the following steps:

[0091] (1) 2.5 parts of epoxy resin W-6C, 0.03 parts of curing agent dicyandiamide, and 0.03 parts of silane coupling agent KH550 are mixed uniformly to obtain magnetic powder glue;

[0092] (2) the magnetic powder glue is added into acetone, and is stirred and dissolved uniformly by a stirrer to obtain glue solution;

[0093] (3) strontium ferrite magnetic powder (average particle size 500 mesh) is weighed and added into a mixer, then the glue solution is added, and stirring is started at a rotating speed of 20 r / min; at the same time, the temperature in the container is heated to 40℃, and stirring is continued for 15 min;

[0094] (4) then neodymium iron boron magnetic powder (brand 8-11, average particle size 200 mesh) is added into the mixer, and stirring is continued at a rotating speed of 20 r / min for 20 min; the rotating speed is adjusted to 15 r / min, and vacuum is extracted to a vacuum degree of 0.09 Pa; the vacuum extraction is stopped, the rotating speed is adjusted to 55 r / min, cooling water is passed to cool to 5℃, and stirring is continued for 10 min to obtain mixed magnetic powder; the added strontium ferrite magnetic powder is 20% of the mass of the neodymium iron boron magnetic powder, the mass of the magnetic powder glue in the glue solution is 2.0% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder, and the mass of the organic solvent is 8% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder;

[0095] (5) the mixed magnetic powder is broken by Φ10×10 stainless steel ball vibration, and is passed through a 60-mesh screen;

[0096] (6) the sieved mixed magnetic powder is pressed into a Φ15×Φ9.8×8.45 mm ring through a mold under a pressing pressure of 10 T / cm 2

[0097] (7) the product after molding is heated and solidified at a temperature of 180℃ for 50 min;

[0098] (8) the product after solidification is subjected to surface treatment of electrophoretic epoxy resin (EP-703) with a film thickness of 0.020 mm;

[0099] (9) the product after surface treatment is subjected to magnetization to obtain the bonded magnet with low magnetic energy product and high coercivity.

[0100] Example 6:

[0101] A preparation method of a bonded magnet with low magnetic energy product and high coercivity, comprising the following steps:

[0102] (1) 2.5 parts of epoxy resin W-6C, 0.03 parts of curing agent dicyandiamide, and 0.03 parts of silane coupling agent KH550 are mixed uniformly to obtain magnetic powder glue;

[0103] (2) the magnetic powder glue is added into acetone, and is stirred and dissolved uniformly by a stirrer to obtain glue solution;

[0104] (3) strontium ferrite magnetic powder (average particle size 500 mesh) is weighed and added into the mixer, and then the glue solution is added, and stirring is started at a rotating speed of 20 r / min; while stirring, the temperature in the container is heated to 40℃, and stirring is continued for 15 min;

[0105] ​(4) then neodymium iron boron magnetic powder (brand 8-11, average particle size 200 mesh) is added into the mixer, and stirring is continued at a rotating speed of 20 r / min for 20 min; the rotating speed is adjusted to 15 r / min, and vacuum is extracted to a vacuum degree of 0.09 Pa; the vacuum extraction is stopped, the rotating speed is adjusted to 55 r / min, cooling water is passed to cool to 5℃, and stirring is continued for 10 min to obtain mixed magnetic powder; the added strontium ferrite magnetic powder is 30% of the mass of the neodymium iron boron magnetic powder, the mass of the magnetic powder glue in the glue solution is 2.0% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder, and the mass of the organic solvent is 8% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder;

[0106] (5) the mixed magnetic powder is broken by Φ10×10 stainless steel ball vibration, and is passed through a 60-mesh screen;

[0107] (6) the sieved mixed magnetic powder is pressed into a Φ15×Φ9.8×8.45 mm ring through a mold under a pressing pressure of 10 T / cm 2

[0108] (7) the product after molding is heated and solidified at a temperature of 180℃ for 50 min;

[0109] (8) the product after solidification is subjected to surface treatment of electrophoretic epoxy resin (EP-703) with a film thickness of 0.020 mm;

[0110] (9) the product after surface treatment is subjected to magnetization to obtain the bonded magnet with low magnetic energy product and high coercivity.

[0111] Example 7:

[0112] A preparation method of a bonded magnet with low magnetic energy product and high coercivity, comprising the following steps:

[0113] (1) 2.5 parts of epoxy resin W-6C, 0.03 parts of curing agent dicyandiamide, and 0.03 parts of silane coupling agent KH550 are mixed uniformly to obtain magnetic powder glue;

[0114] (2) the magnetic powder glue is added into acetone, and is stirred and dissolved uniformly by a stirrer to obtain glue solution;

[0115] (3) strontium ferrite magnetic powder (average particle size 500 mesh) is weighed and added into a mixer, and then the glue solution is added, and stirring is started at a rotating speed of 20 r / min; while stirring, the temperature in the container is heated to 40℃, and stirring is continued for 15 min;

[0116] ​(4) then neodymium iron boron magnetic powder (brand 8-11, average particle size 200 mesh) is added into the mixer, and stirring is continued at a rotating speed of 20 r / min for 20 min; the rotating speed is adjusted to 15 r / min, and vacuum is extracted to a vacuum degree of 0.09 Pa; the vacuum extraction is stopped, the rotating speed is adjusted to 55 r / min, cooling water is passed to cool to 5℃, and stirring is continued for 10 min to obtain mixed magnetic powder; the added strontium ferrite magnetic powder is 50% of the mass of the neodymium iron boron magnetic powder, the mass of the magnetic powder glue in the glue solution is 2.0% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder, and the mass of the organic solvent is 8% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder;

[0117] (5) the mixed magnetic powder is broken by Φ10×10 stainless steel ball vibration, and is passed through a 60-mesh screen;

[0118] (6) the sieved mixed magnetic powder is pressed into a Φ15×Φ9.8×8.45 mm ring through a mold under a pressing pressure of 10 T / cm 2

[0119] (7) the product after molding is heated and solidified at a temperature of 180℃ for 50 min;

[0120] (8) the product after solidification is subjected to surface treatment of electrophoretic epoxy resin (EP-703) with a film thickness of 0.020 mm;

[0121] (9) the product after surface treatment is subjected to magnetization to obtain the bonded magnet with low magnetic energy product and high coercivity.

[0122] Example 8:

[0123] A preparation method of a bonded magnet with low magnetic energy product and high coercivity, comprising the following steps:

[0124] (1) 2.5 parts of epoxy resin W-6C, 0.03 parts of curing agent dicyandiamide, and 0.03 parts of silane coupling agent KH550 are mixed uniformly to obtain magnetic powder glue;

[0125] (2) the magnetic powder glue is added into acetone, and is stirred and dissolved uniformly by a stirrer to obtain glue solution;

[0126] (3) strontium ferrite magnetic powder (average particle size 500 mesh) is weighed and added into the mixer, and then the glue solution is added, and stirring is started at a rotating speed of 20 r / min; at the same time, the temperature in the container is heated to 40℃, and stirring is continued for 15 min;

[0127] ​(4) Then neodymium iron boron magnetic powder (brand 8-11, average particle size 200 mesh) is added into the mixer, and stirring is continued at a speed of 20 r / min for 20 min; the speed is adjusted to 15 r / min, and vacuum is extracted to a vacuum degree of 0.09 Pa; the vacuum extraction is stopped, the speed is adjusted to 55 r / min, cooling water is passed to cool to 5℃, and stirring is continued for 10 min to obtain mixed magnetic powder; the added strontium ferrite magnetic powder is 70% of the mass of the neodymium iron boron magnetic powder, the mass of the magnetic powder glue in the glue solution is 2.0% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder, and the mass of the organic solvent is 8% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder;

[0128] (5) The mixed magnetic powder is broken by Φ10×10 stainless steel ball vibration, and is passed through a 60-mesh screen;

[0129] (6) The sieved mixed magnetic powder is pressed into a Φ15×Φ9.8×8.45 mm ring through a mold under a pressing pressure of 10 T / cm 2

[0130] (7) The product after molding is heated and solidified at a temperature of 180℃ for 50 min;

[0131] (8) The product after solidification is subjected to surface treatment of electrophoretic epoxy resin (EP-703) with a film thickness of 0.020 mm;

[0132] (9) The product after surface treatment is magnetized to obtain the bonded magnet with low magnetic energy product and high coercivity.

[0133] Comparative Example 1 (two kinds of magnetic powders are directly mixed and then added into the glue solution):

[0134] A preparation method of a bonded magnet with low magnetic energy product and high coercivity, comprising the following steps:

[0135] (1) 2.5 parts of epoxy resin W-6C, 0.03 parts of curing agent dicyandiamide, and 0.03 parts of silane coupling agent KH550 are mixed uniformly to obtain magnetic powder glue;

[0136] (2) The magnetic powder glue is added into acetone, and is stirred and dissolved uniformly by a stirrer to obtain a glue solution;

[0137] ​(3) take strontium ferrite magnetic powder (average particle size 500 mesh) and neodymium-iron-boron magnetic powder (brand 8-11, average particle size 200 mesh) into a mixer, then add the glue solution, start stirring at 20 r / min; while stirring, heat the temperature in the container to 40℃, and stir for 35 min; adjust the stirring speed to 15 r / min and continue stirring, and vacuum to a vacuum degree of 0.09 Pa; stop vacuuming, adjust the stirring speed to 55 r / min, cool to 5℃ with cooling water, continue stirring for 10 min, and obtain mixed magnetic powder; the added strontium ferrite magnetic powder is 5% of the mass of the neodymium-iron-boron magnetic powder, the mass of the magnetic powder glue in the glue solution is 2.0% of the total mass of the strontium ferrite magnetic powder and the neodymium-iron-boron magnetic powder, and the mass of the organic solvent is 8% of the total mass of the strontium ferrite magnetic powder and the neodymium-iron-boron magnetic powder;

[0138] (4) the mixed magnetic powder is broken by Φ10×10 stainless steel ball vibration and passes through a 60-mesh screen;

[0139] (5) under a pressing pressure of 10T / cm 2 , the screened mixed magnetic powder is pressed into a Φ15×Φ9.8×8.45mm ring through a mold;

[0140] (6) the molded product is heated and cured at a temperature of 180℃ for 50 min;

[0141] (7) the cured product is surface treated with electrophoretic epoxy resin (EP-703) with a film thickness of 0.020mm;

[0142] (8) the surface treated product is magnetized to obtain the bonded magnet with low magnetic energy product and high coercivity.

[0143] Comparative Example 2 (too much strontium ferrite magnetic powder):

[0144] A preparation method of a bonded magnet with low magnetic energy product and high coercivity, comprising the following steps:

[0145] (1) uniformly mix 2.5 parts of epoxy resin W-6C, 0.03 parts of curing agent dicyandiamide, and 0.03 parts of silane coupling agent KH550 by weight to obtain magnetic powder glue;

[0146] (2) add the magnetic powder glue into acetone, and uniformly dissolve and stir with a stirrer to obtain a glue solution;

[0147] (3) take strontium ferrite magnetic powder (average particle size 500 mesh) into a mixer, then add the glue solution, start stirring at 20 r / min; while stirring, heat the temperature in the container to 40℃, and stir for 15 min;

[0148] (4) then neodymium iron boron magnetic powder (brand 8-11, average particle size 200 mesh) is added into the mixer, and stirring is continued at a rotating speed of 20 r / min for 20 min; the rotating speed is adjusted to 15 r / min, and vacuumizing is continued until the vacuum degree is 0.09 Pa; the vacuumizing is stopped, the rotating speed is adjusted to 55 r / min, cooling water is passed to cool to 5℃, and stirring is continued for 10 min to obtain mixed magnetic powder; the added strontium ferrite magnetic powder is 80% of the mass of the neodymium iron boron magnetic powder, the mass of the magnetic powder glue in the glue solution is 2.0% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder, and the mass of the organic solvent is 8% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder;

[0149] (5) the mixed magnetic powder is broken by Φ10×10 stainless steel ball vibration, and is passed through a 60-mesh screen;

[0150] (6) the screened mixed magnetic powder is pressed into a Φ15×Φ9.8×8.45 mm ring through a mold under a pressing pressure of 10 T / cm 2

[0151] (7) the product after molding is heated and solidified at a temperature of 180℃ for 50 min;

[0152] (8) the product after solidification is subjected to surface treatment of electrophoretic epoxy resin (EP-703) with a film thickness of 0.020 mm;

[0153] (9) the product after surface treatment is subjected to magnetization to obtain the bonded magnet with low magnetic energy product and high coercivity.

[0154] Comparative Example 3 (stirring speed is too fast):

[0155] A preparation method of a bonded magnet with low magnetic energy product and high coercivity, comprising the following steps:

[0156] (1) 2.5 parts of epoxy resin W-6C, 0.03 parts of curing agent dicyandiamide, and 0.03 parts of silane coupling agent KH550 are mixed uniformly to obtain magnetic powder glue;

[0157] (2) the magnetic powder glue is added into acetone, and is stirred and dissolved uniformly by a stirrer to obtain glue solution;

[0158] (3) strontium ferrite magnetic powder (average particle size 500 mesh) is weighed and added into a mixer, then the glue solution is added, and stirring is started at a rotating speed of 40 r / min; at the same time, the temperature in the container is heated to 40℃, and stirring is continued for 15 min;

[0159] ​(4) then neodymium iron boron magnetic powder (brand 8-11, average particle size 200 mesh) is added into the mixer, and stirring is continued at a rotating speed of 40 r / min for 20 min; the rotating speed is adjusted to 30 r / min, and vacuum is extracted to a vacuum degree of 0.09 Pa; the vacuum extraction is stopped, the rotating speed is adjusted to 55 r / min, cooling water is passed to cool to 5℃, and stirring is continued for 10 min to obtain mixed magnetic powder; the added strontium ferrite magnetic powder is 5% of the mass of the neodymium iron boron magnetic powder, the mass of the magnetic powder glue in the glue solution is 2.0% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder, and the mass of the organic solvent is 8% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder;

[0160] (5) the mixed magnetic powder is broken by Φ10×10 stainless steel ball vibration, and is passed through a 60-mesh screen;

[0161] (6) under a pressing pressure of 10 T / cm 2 , the screened mixed magnetic powder is pressed into a circular ring with a size of Φ15×Φ9.8×8.45 mm through a mold;

[0162] (7) the product after molding is heated and solidified at a temperature of 180℃ for 50 min;

[0163] (8) the product after solidification is subjected to surface treatment of electrophoretic epoxy resin (EP-703) with a film thickness of 0.020 mm;

[0164] (9) the product after surface treatment is subjected to magnetization to obtain the bonded magnet with low magnetic energy product and high coercivity.

[0165] Comparative Example 4 (stirring speed is too slow):

[0166] A preparation method of a bonded magnet with low magnetic energy product and high coercivity, comprising the following steps:

[0167] (1) 2.5 parts of epoxy resin W-6C, 0.03 parts of curing agent dicyandiamide, and 0.03 parts of silane coupling agent KH550 are mixed uniformly to obtain magnetic powder glue;

[0168] (2) the magnetic powder glue is added into acetone, and is stirred and dissolved uniformly by a stirrer to obtain glue solution;

[0169] (3) strontium ferrite magnetic powder (average particle size 500 mesh) is weighed and added into a mixer, then the glue solution is added, and stirring is started at a rotating speed of 10 r / min; while stirring, the temperature in the container is heated to 40℃, and stirring is continued for 15 min;

[0170] (4) then neodymium iron boron magnetic powder (brand 8-11, average particle size 200 mesh) is added into the mixer, and stirring is continued at a rotating speed of 10 r / min for 20 min; then vacuum is extracted to a vacuum degree of 0.09 Pa; the vacuum extraction is stopped, the rotating speed is adjusted to 55 r / min, cooling water is passed to cool to 5℃, and stirring is continued for 10 min to obtain mixed magnetic powder; the added strontium ferrite magnetic powder is 5% of the mass of the neodymium iron boron magnetic powder, the mass of the magnetic powder glue in the glue solution is 2.0% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder, and the mass of the organic solvent is 8% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder;

[0171] (5) the mixed magnetic powder is broken by Φ10×10 stainless steel ball vibration, and is passed through a 60-mesh screen;

[0172] (6) the sieved mixed magnetic powder is pressed into a Φ15×Φ9.8×8.45mm ring through a mold under a pressing pressure of 10T / cm 2

[0173] (7) the product after molding is heated and solidified at a temperature of 180℃ for 50 min;

[0174] (8) the product after solidification is subjected to surface treatment of electrophoretic epoxy resin (EP-703) with a film thickness of 0.020mm;

[0175] (9) the product after surface treatment is subjected to magnetization to obtain the bonded magnet with low magnetic energy product and high coercivity.

[0176] Comparative Example 5 (the organic solvent is not fully volatilized):

[0177] A preparation method of a bonded magnet with low magnetic energy product and high coercivity, comprising the following steps:

[0178] (1) 2.5 parts of epoxy resin W-6C, 0.03 parts of curing agent dicyandiamide, and 0.03 parts of silane coupling agent KH550 are mixed uniformly to obtain magnetic powder glue;

[0179] (2) the magnetic powder glue is added into acetone, and is stirred and dissolved uniformly by a stirrer to obtain glue solution;

[0180] (3) strontium ferrite magnetic powder (average particle size 500 mesh) is weighed and added into the mixer, and then the glue solution is added, and stirring is started at a rotating speed of 20 r / min for 15 min;

[0181] ​(4) then neodymium iron boron magnetic powder (brand 8-11, average particle size 200 mesh) is added into the mixer, and stirring is continued at a rotating speed of 20 r / min for 20 min; the rotating speed is adjusted to 15 r / min, and vacuumizing is continued until the vacuum degree is 0.09 Pa; the vacuumizing is stopped, the rotating speed is adjusted to 55 r / min, cooling water is passed to cool to 5℃, and stirring is continued for 10 min to obtain mixed magnetic powder; the added strontium ferrite magnetic powder is 5% of the mass of the neodymium iron boron magnetic powder, the mass of the magnetic powder glue in the glue solution is 2.0% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder, and the mass of the organic solvent is 8% of the total mass of the strontium ferrite magnetic powder and the neodymium iron boron magnetic powder;

[0182] (5) the mixed magnetic powder is broken by Φ10×10 stainless steel ball vibration, and is passed through a 60-mesh screen;

[0183] (6) the screened mixed magnetic powder is pressed into a Φ15×Φ9.8×8.45 mm ring through a mold under a pressing pressure of 10 T / cm 2

[0184] (7) the product after molding is heated and solidified at a temperature of 180℃ for 50 min;

[0185] (8) the product after solidification is subjected to surface treatment of electrophoretic epoxy resin (EP-703) with a film thickness of 0.020 mm;

[0186] (9) the product after surface treatment is subjected to magnetization to obtain the bonded magnet with low magnetic energy product and high coercivity.

[0187] Comparative Example 6 (excessive volatilization of organic solvent):

[0188] A preparation method of a bonded magnet with low magnetic energy product and high coercivity, comprising the following steps:

[0189] (1) 2.5 parts of epoxy resin W-6C, 0.03 parts of curing agent dicyandiamide, and 0.03 parts of silane coupling agent KH550 are mixed uniformly to obtain magnetic powder glue;

[0190] (2) the magnetic powder glue is added into acetone, and is stirred and dissolved uniformly by a stirrer to obtain glue solution;

[0191] (3) strontium ferrite magnetic powder (average particle size 500 mesh) is weighed and added into the mixer, and then the glue solution is added, and stirring is started at a rotating speed of 20 r / min; at the same time, the temperature in the container is heated to 60℃, and stirring is continued for 15 min;

[0192] ​(4) then neodymium-iron-boron magnetic powder (brand 8-11, average particle size 200 mesh) is added into the mixer, and stirring is continued at a rotating speed of 20 r / min for 20 min; the rotating speed is adjusted to 15 r / min, and vacuum is extracted to a vacuum degree of 0.09 Pa; the vacuum extraction is stopped, the rotating speed is adjusted to 55 r / min, cooling water is passed to cool to 5℃, and stirring is continued for 10 min to obtain mixed magnetic powder; the strontium ferrite magnetic powder added is 5% of the mass of the neodymium-iron-boron magnetic powder, the mass of the magnetic powder glue in the glue solution is 2.0% of the total mass of the strontium ferrite magnetic powder and the neodymium-iron-boron magnetic powder, and the mass of the organic solvent is 8% of the total mass of the strontium ferrite magnetic powder and the neodymium-iron-boron magnetic powder;

[0193] (5) the mixed magnetic powder is broken by Φ10×10 stainless steel ball vibration, and is passed through a 60-mesh screen;

[0194] (6) the sieved mixed magnetic powder is pressed into a Φ15×Φ9.8×8.45 mm ring through a mold under a pressing pressure of 10 T / cm 2

[0195] (7) the product after molding is heated and solidified at a temperature of 180℃ for 50 min;

[0196] (8) the product after solidification is subjected to surface treatment of electrophoretic epoxy resin (EP-703) with a film thickness of 0.020 mm;

[0197] (9) the product after surface treatment is subjected to magnetization to obtain the bonded magnet with low magnetic energy product and high coercivity.

[0198] The properties of the bonded magnets prepared in the above examples and comparative examples are tested, and the results are shown in Table 1; wherein the magnetic properties are tested by a magnetic tester, and the salt spray test is performed by using a 5(wt)% NaCl solution.

[0199] Table 1: Test results of properties of bonded magnets.

[0200]

[0201] As can be seen from Table 1, the strontium ferrite magnetic powder and the neodymium-iron-boron magnetic powder are mixed by the method in the application in Examples 1-8, and the two can be uniformly mixed, the magnetic properties of the obtained bonded magnet have a small fluctuation range, the fluctuation range of the maximum magnetic energy product is within 2%, the fluctuation range of the intrinsic coercivity is within 1%, the film thickness of the epoxy resin layer on the surface is uniform, and the product has good corrosion resistance. At the same time, the obtained bonded magnet has high coercivity, and can realize continuous adjustment of the magnetic energy product in the range of 3.0-8.0 MGOe, which can meet the requirements of different fields for magnetic properties, and improve the performance-price ratio of the product.

[0202] ​In Comparative Example 1, strontium ferrite magnetic powder and neodymium iron boron magnetic powder were directly mixed and then added to the adhesive. Due to the difference in their properties, they could not be mixed evenly. The fluctuation range of the magnetic properties of the resulting bonded magnet was significantly increased compared with that in Example 1. The thickness of the epoxy resin layer on the surface of the product could not be kept consistent, which led to a decrease in its corrosion resistance.

[0203] In Comparative Example 2, the addition ratio of strontium ferrite magnetic powder was too high, which prevented it from adhering evenly to the surface of neodymium iron boron magnetic powder. This reduced the uniformity of mixing and resulted in a larger fluctuation in magnetic properties compared to Example 1.

[0204] In Comparative Example 3, the stirring speed during mixing was too fast, which easily caused local agglomeration of magnetic powder, resulting in uneven mixing of strontium ferrite magnetic powder with magnetic powder adhesive and neodymium iron boron magnets. In Comparative Example 4, the stirring speed during mixing was too slow, which prevented the magnetic powder from flowing effectively and also prevented the strontium ferrite magnetic powder from mixing evenly with magnetic powder adhesive and neodymium iron boron magnets. Both of these factors led to an increase in the fluctuation range of the magnetic properties of the product.

[0205] In Comparative Example 5, the organic solvent did not evaporate sufficiently after the strontium ferrite magnetic powder was mixed with the adhesive, resulting in an overly wet magnetic powder adhesive that could not adhere to the surface of the magnetic powder and solidify. Consequently, the strontium ferrite magnetic powder could not effectively adhere to the surface of the neodymium iron boron magnet, and the two could not be mixed evenly. In Comparative Example 6, excessive evaporation of the organic solvent resulted in the magnetic powder adhesive being fully solidified on the surface of the magnetic powder, making it impossible for the neodymium iron boron magnetic powder to adhere to it, which was also not conducive to the even mixing of the two. Both of these situations also led to large fluctuations in the magnetic properties of the product.

Claims

1. A method for preparing a bonded magnet with low energy product and high coercivity, characterized in that the steps include: include: (1) Dissolve the magnetic powder adhesive in an organic solvent to obtain an adhesive solution; (2) Add the adhesive solution to the strontium ferrite magnetic powder and stir at 15~30 r / min for 10~20 min at 40±5℃; (3) Add neodymium iron boron magnetic powder, stir under the same conditions for 15-25 min, adjust the speed to 10-20 r / min, and evacuate to a vacuum degree of 0.08-0.1 Pa; stop evacuation, adjust the speed to 50-60 r / min, cool to 5±5℃, and continue stirring for 5-15 min to obtain mixed magnetic powder; the added strontium ferrite magnetic powder is 0-70% of the mass of neodymium iron boron magnetic powder; (4) After crushing and sieving the mixed magnetic powder, it is molded into shape; (5) The molded product is heated and cured, treated with epoxy resin and magnetized in sequence.

2. The method for preparing a bonded magnet with low energy product and high coercivity according to claim 1, characterized in that, The average particle size of the strontium ferrite magnetic powder is 400-600 mesh, and the average particle size of the neodymium iron boron magnetic powder is 100-250 mesh.

3. The method for preparing a bonded magnet with low magnetic energy product and high coercivity according to claim 1, characterized in that, By weight, the components of the magnetic powder adhesive in step (1) include: 2-3 parts epoxy resin, 0.35-0.55 parts curing agent, and 0.02-0.04 parts coupling agent.

4. The method for preparing a bonded magnet with low magnetic energy product and high coercivity according to claim 3, characterized in that, The curing agent is dicyandiamide, and the coupling agent is KH550.

5. The method for preparing a bonded magnet with low magnetic energy product and high coercivity according to claim 1, 2, or 3, characterized in that, The mass of the magnetic powder adhesive in the added adhesive solution is 1.5 to 3.0% of the total mass of strontium ferrite magnetic powder and neodymium iron boron magnetic powder, and the mass of the organic solvent is 5 to 10% of the total mass of strontium ferrite magnetic powder and neodymium iron boron magnetic powder.

6. The method for preparing a bonded magnet with low magnetic energy product and high coercivity according to claim 1, characterized in that, In step (4), the mixed magnetic powder is crushed by vibration using Φ10×10 stainless steel balls and then sieved through a 40~80 mesh screen.

7. The method for preparing a bonded magnet with low magnetic energy product and high coercivity according to claim 1 or 6, characterized in that, The pressure during compression molding in step (4) is 8-10 T / cm. 2 .

8. The method for preparing a bonded magnet with low energy product and high coercivity according to claim 1, characterized in that, In step (5), the temperature for heating and curing is 180±10℃ and the curing time is 50±10min.

9. The method for preparing a bonded magnet with low magnetic energy product and high coercivity according to claim 1 or 8, characterized in that, In step (5), the thickness of the surface epoxy resin layer is 0.015~0.025mm.

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