Ferrite magnetic powder, method for producing the same, and bonded magnet

Abstract

The application provides a kind of ferrite magnetic powder and its preparation method, bonded magnet, relate to the technical field of magnetic material, the preparation method of the ferrite magnetic powder includes the following steps: (a) the densification treatment of ferrite powder, obtain densification powder;(b) the annealing treatment of densification powder, break, obtain ferrite magnetic powder;Wherein, ferrite powder includes the fine powder of average particle size 0.2-0.5 microns and the coarse powder of average particle size 4.5-6.0 microns, the weight percentage of fine powder is 35-45%.The application solves the technical problem that the ferrite magnetic powder provided by the prior art cannot effectively consider the magnetic powder compression density (CD) and the magnet intrinsic coercivity (jHc) index, reaches the technical effect that the magnetic powder compression density is between 3.75-3.85g / cm 3 and the magnet intrinsic coercivity is above 275kA / m.

Description

Technical Field

[0001] This invention relates to the technical field of magnetic materials, and in particular to a ferrite magnetic powder and its preparation method, and a bonded magnet. Background Technology

[0002] In the field of bonded ferrite materials, injection-molded magnets are widely used in automotive, office, and home appliances—industries employing rotating electronic components—due to their high cost-effectiveness and ability to mold complex devices. To adapt to the miniaturization and efficiency trends in electronic appliances, higher requirements are being placed on injection-molded magnets: First, the injection molding of increasingly smaller and more complex micro-motor components necessitates higher magnet fluidity; second, to increase the lifespan of micro-motors and broaden their application areas, and to prevent demagnetization during frequent start-stop processes and under high and low temperature environments, the magnets need to possess higher intrinsic coercivity.

[0003] In injection-bonded ferrite magnets, ferrite powder accounts for approximately 90% of the mass. The properties of the magnetic powder directly affect the magnet's flowability and intrinsic coercivity. Higher compressive density of bonded ferrite powder means that to achieve the same mass percentage, the volume percentage of the powder in the binder is smaller, thus increasing the binder's volume ratio and improving the magnet's flowability. Therefore, under certain magnet formulation and molding process conditions, the magnet's flowability is positively correlated with the compressive density of the magnetic powder. Simultaneously, bonded ferrite powder needs to possess high intrinsic coercivity because shearing and friction between the materials during the mixing and molding process cause a certain proportion of loss in the magnet's intrinsic coercivity. Therefore, under certain magnet molding process conditions, the intrinsic coercivity of the magnet is positively correlated with the intrinsic coercivity of the magnetic powder.

[0004] Currently, this type of magnetic powder is divided into two types based on its preparation technology. One type has a normal particle size distribution, and its laser particle size distribution waveform shows a single peak. Its compressive density is generally between 3.3 and 3.5 g / cm³. 3 Between these two types, the intrinsic coercivity (jHc) of the magnet is generally less than 250 kA / m; another type is ferrite magnetic powder obtained through a coarse and fine powder mixing process, whose laser particle size distribution waveform exhibits multiple peaks, and the magnetic powder compressibility can reach 3.5-3.7 g / cm³. 3 The intrinsic coercivity (jHc) of the magnet is generally less than 260 kA / m. Existing technology CN201610167551.6 discloses a bonded ferrite magnetic powder and a bonded magnet, and a method for preparing the same. The particle size distribution of the bonded ferrite magnetic powder is normally distributed, and the main phase has the following molecular formula: (Sr... 1～x Ba xO·nFe₂O₃, where n is between 6.11 and 6.30, and 0.10 ≤ x ≤ 0.20, is prepared by using industrial-grade iron oxide red, strontium carbonate, and barium carbonate as raw materials, mixing them in a specific ratio, adding strontium chloride during the mixing process, pre-calcining at 1200–1280°C, and then crushing, grinding, and annealing to obtain bonded ferrite magnetic powder. In the examples, the magnetic powder compression density is less than 3.6 g / cm³. 3 The jHc index of the magnetic powder compact is less than 245 kA / m, but the jHc index of the magnet is not explicitly stated. Existing technology CN200410034695.1 discloses a bonded magnet and ferrite magnetic powder for bonded magnets, which uses a mixture of coarse powder (average particle size 2.5-5.0 micrometers) and fine powder (average particle size 0.5-1.0 micrometers), with the fine powder accounting for 15-40% of the mixed powder weight. The coarse and fine powders are mixed using a wet method. In the embodiment, the jHc index of the magnet is less than 265 kA / m, and the magnetic powder compression density is less than 3.5 g / cm³. 3 The prior art CN200880108680.1 discloses a ferrite powder for bonding magnets, its manufacturing method, and a bonded magnet using the same. It uses a mixture of coarse powder (average particle size 1.0-5.0 micrometers) and fine powder (average particle size 0.2-1.0 micrometers), with the fine powder accounting for 15-40% of the weight of the mixed powder. In the examples, the magnetic powder compressibility is less than 3.5 g / cm³. 3 The jHc index of the magnet is not explicitly stated. In the prior art, CN201080016639.9 discloses a ferrite powder for bonding magnets and its manufacturing method, as well as a bonded magnet using the same. This method involves mixing coarse and fine powders, but does not specify the average particle size range of the coarse and fine powders. The fine powder accounts for 15-40% of the weight of the mixed powder. Besides the above-mentioned prior art, there are also methods that mix ferrite with rare earth elements to improve the magnetic properties (including the jHc index) of ferrite materials. However, none of these methods address the technical issue of how to improve the magnetic powder compressibility density, and the addition of rare earth elements increases production costs, leading to a decrease in cost-effectiveness.

[0005] As can be seen from the above-mentioned existing technology, the process of preparing ferrite magnetic powder by mixing coarse powder and fine powder has at least the following problems:

[0006] (1) For ferrite powder with normal distribution, in order to improve the jHc index of the powder, the average particle size of the powder is often reduced by extending the grinding time and adding flux to refine the grain size. However, the reduction of the average particle size of the powder will lead to a decrease in the compressive density, and there is a contradiction between the two.

[0007] (2) For ferrite powder with multi-peak particle size distribution, in order to improve the compressibility, the method of increasing the particle size difference between coarse powder and fine powder is often adopted; in order to improve the average particle size of coarse powder, the process route of high temperature sintering is often adopted. However, under high temperature sintering conditions, magnetic powder particles will have problems such as adhesion and crystallization, which will lead to a decrease in the jHc index of coarse powder. In order to improve this problem, the method of increasing the proportion of fine powder is often adopted. However, as the content of fine powder increases, the overall compressibility of magnetic powder will decrease. Therefore, there is a contradiction between the jHc index and the compressibility of magnetic powder.

[0008] In view of this, the present invention is hereby proposed. Summary of the Invention

[0009] One of the objectives of this invention is to provide a method for preparing ferrite magnetic powder that can improve the magnetic powder compressibility density (CD) and intrinsic coercivity (jHc) of the magnetic powder.

[0010] The second objective of this invention is to provide a ferrite magnetic powder that can effectively balance the magnetic powder compressibility density (CD) and intrinsic coercivity (jHc) of the magnet, and can be used for injection molding, thereby improving the flowability and magnetic properties of injection-molded bonded ferrite magnets.

[0011] The third objective of this invention is to provide a bonded magnet with a high intrinsic coercivity (jHc) index.

[0012] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0013] In a first aspect, a method for preparing ferrite magnetic powder includes the following steps:

[0014] (a) The ferrite powder is densified to obtain densified powder;

[0015] (b) The densified powder is annealed and crushed to obtain the ferrite magnetic powder;

[0016] The ferrite powder includes fine powder with an average particle size of 0.2-0.5 micrometers and coarse powder with an average particle size of 4.5-6.0 micrometers;

[0017] The fine powder accounts for 35-45% by weight;

[0018] Both the fine powder and the coarse powder independently comprise iron oxide red and additives.

[0019] Furthermore, the densification process includes ball milling.

[0020] Preferably, the densification process includes the following steps:

[0021] The ferrite powder was ball-milled using a reciprocating vibratory ball mill to obtain a densified powder.

[0022] Furthermore, the method for preparing the fine powder includes the following steps:

[0023] After mixing the first iron oxide red and the additives, the mixture is densely pelletized and sintered to obtain the fine powder.

[0024] Preferably, the average particle size of the first iron oxide red is less than 0.8 micrometers;

[0025] Preferably, the temperature of the first sintering is 930-950℃.

[0026] Furthermore, the method for preparing the coarse powder includes the following steps:

[0027] The second iron oxide red and additives are mixed and densely pelletized, followed by a second sintering to obtain the coarse powder;

[0028] Preferably, the average particle size of the second iron oxide is greater than 1.50 micrometers;

[0029] Preferably, the second sintering temperature is 1180-1230℃.

[0030] Furthermore, the method of dense pelletizing includes applying pressure to form pellets;

[0031] Preferably, the applied pressure is above 10 MPa.

[0032] Furthermore, the additive includes at least one of strontium carbonate and strontium chloride.

[0033] Secondly, ferrite magnetic powder prepared by any of the above-described preparation methods.

[0034] Furthermore, the compressive density of the ferrite magnetic powder is 3.75-3.85 g / cm³. 3 .

[0035] Thirdly, a bonded magnet comprising the ferrite magnetic powder described in any of the preceding claims.

[0036] Furthermore, the intrinsic coercivity of the bonded magnet is above 275 kA / m;

[0037] Preferably, the residual magnetic induction intensity of the bonded magnet is above 293 mT.

[0038] Compared with the prior art, the present invention has at least the following beneficial effects:

[0039] The ferrite magnetic powder preparation method provided by this invention maintains a high jHc index in the ferrite powder composed of fine powder and coarse powder of specific particle size and in a specific ratio. At the same time, the densification treatment of the ferrite powder before the annealing process can optimize the morphology of the coarse and fine powder in the powder to achieve spherical shape, thereby improving the compressibility density of the magnetic powder. Therefore, the preparation method provided by this invention, with the synergistic effect of specific ferrite powder and densification treatment step, achieves the dual goals of high magnetic powder compressibility density and high magnet jHc index.

[0040] The ferrite magnetic powder provided by this invention can effectively balance the magnetic powder compressibility density (CD) and intrinsic coercivity (jHc) of the magnet, and can be used for injection molding. It can improve the flowability and magnetic properties of injection-molded bonded ferrite magnets, exceeding the level of equivalent products in the prior art.

[0041] The bonded magnet provided by this invention has a high intrinsic coercivity (jHc) index. Detailed Implementation

[0042] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] According to a first aspect of the present invention, a method for preparing ferrite magnetic powder is provided, comprising the following steps:

[0044] (a) The ferrite powder is densified to obtain densified powder;

[0045] (b) The densified powder is annealed and crushed to obtain ferrite magnetic powder;

[0046] Ferrite powder includes, but is not limited to, fine powder with an average particle size of 0.2-0.5 micrometers and coarse powder with an average particle size of 4.5-6.0 micrometers; wherein, the weight percentage of fine powder is 35-45%;

[0047] Both fine powder and coarse powder are independent of, but not limited to, iron oxide red and additives.

[0048] In this invention, the typical but non-limiting average particle size of the fine powder is, for example, 0.2, 0.3, 0.4, or 0.5; the typical but non-limiting average particle size of the coarse powder is, for example, 4.5, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8, or 6.0; and the typical but non-limiting weight percentage of the fine powder is, for example, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, or 45%.

[0049] The method for preparing ferrite magnetic powder provided by the present invention maintains a high JHc index in ferrite powder composed of fine powder and coarse powder of specific particle size and in specific proportion.

[0050] The ferrite magnetic powder preparation method provided by this invention involves densification treatment of the ferrite powder before the annealing process, which optimizes the morphology of coarse and fine powders in the powder to achieve spherical shape, thereby improving the compressibility density of the magnetic powder. Therefore, the preparation method provided by this invention, with the synergistic effect of specific ferrite powder and densification treatment steps, achieves the dual goals of high magnetic powder compressibility density and high magnet JHc index.

[0051] In a preferred embodiment, the densification treatment in this invention includes, but is not limited to, ball milling, which is more conducive to improving the densification effect of ferrite powder.

[0052] In a preferred embodiment, the densification process of the present invention includes the following steps:

[0053] Ferrite powder was ball-milled using a reciprocating vibratory ball mill to obtain a denser powder.

[0054] This invention employs a reciprocating vibratory ball mill for densification treatment, which can optimize the morphology of coarse and fine powders in ferrite powder, thereby further improving the compressibility density of the magnetic powder.

[0055] In a preferred embodiment, the method for preparing the fine powder in this invention includes the following steps:

[0056] After mixing the first iron oxide red and additives, the mixture is densely pelletized and sintered to obtain fine powder.

[0057] Among them, the average particle size of the first iron oxide red is less than 0.8 micrometers.

[0058] In a preferred embodiment, the method for preparing the coarse powder in this invention includes the following steps:

[0059] After the second iron oxide red and additives are mixed and densely pelletized, and then sintered again, coarse powder is obtained.

[0060] Among them, the average particle size of the second iron oxide is above 1.50 micrometers.

[0061] Unlike existing technologies that use industrial-grade iron oxide red, strontium carbonate, and barium carbonate as raw materials to prepare powder, this invention uses iron oxide red raw materials with an average particle size of less than 0.8 micrometers to prepare fine powder and iron oxide red raw materials with an average particle size of more than 1.50 micrometers to prepare coarse powder. After mixing the fine powder and coarse powder in a certain proportion, ferrite magnetic powder with high JHc index and high compressibility density can be obtained.

[0062] In this invention, the dense pelletizing after uniform mixing of iron oxide red and additives (including but not limited to at least one of strontium carbonate and strontium chloride) can reduce the porosity between raw material particles, increase the contact area between raw material particles, and improve the activity of solid-phase reaction between different material particles, which can effectively reduce the sintering temperature and achieve the effect of high-temperature pre-sintering.

[0063] In a preferred embodiment, the method of dense pelletizing includes, but is not limited to, applying pressure to form pellets. The applied pressure can be above 10 MPa. Dense pelletizing with a pressure above 10 MPa is more conducive to reducing the porosity between raw material particles, more conducive to increasing the contact area between raw material particles, and more conducive to improving the activity of solid-phase reaction between different material particles, so as to effectively reduce the sintering temperature and achieve the effect of high-temperature pre-sintering.

[0064] In a preferred embodiment, the first sintering temperature can be 930-950°C, with typical but non-limiting temperatures such as 930°C, 935°C, 940°C, 945°C, and 950°C. After the iron oxide red with an average particle size of less than 0.8 micrometers and the additives are mixed evenly, pellets (blocks) are formed by applying a pressure of more than 10 MPa and sintering at a temperature of 930-950°C. This not only allows the material to maintain a small grain size, but also results in a low material density, which facilitates subsequent grinding and is beneficial for obtaining fine powder with a small average particle size and ultra-high JHc index.

[0065] In a preferred embodiment, the second sintering temperature can be 1180-1230°C, with typical but non-limiting temperatures such as 1180°C, 1190°C, 1200°C, 1210°C, 1220°C, and 1230°C. After the iron oxide red with an average particle size of more than 1.50 micrometers and the additives are mixed evenly, pellets (blocks) are formed by applying a pressure of more than 10 MPa and sintering at a temperature of 1180-1230°C. This not only allows the material to maintain a large particle size but also avoids problems such as crystallization, thereby maintaining a high JHc index for the coarse powder.

[0066] According to a second aspect of the present invention, a ferrite magnetic powder prepared by any of the above-described preparation methods is provided.

[0067] The ferrite magnetic powder provided by this invention has a compressive density of 3.75-3.85 g / cm³. 3 Its typical, but not limiting, compressible density is, for example, 3.75 g / cm³. 3 3.76 g / cm 3 3.77 g / cm 3 3.78g / cm 3 3.79 g / cm 3 3.80g / cm3 3.81 g / cm 3 3.82g / cm 3 3.83 g / cm 3 3.84 g / cm 3 3.85g / cm 3 .

[0068] The ferrite magnetic powder provided by this invention can effectively balance the magnetic powder compressibility density (CD) and intrinsic coercivity (jHc) of the magnet, and can be used for injection molding. It can improve the flowability and magnetic properties of injection-molded bonded ferrite magnets, exceeding the level of equivalent products in the prior art.

[0069] According to a third aspect of the present invention, a bonded magnet is provided, comprising the ferrite magnetic powder described in any of the preceding claims.

[0070] The intrinsic coercivity of the bonded magnet provided by this invention is above 275 kA / m, and the remanent magnetic induction intensity is above 293 mT.

[0071] The present invention will be further illustrated below through examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0072] Example 1

[0073] A method for preparing ferrite magnetic powder includes the following steps:

[0074] (1) Preparation of fine powder:

[0075] Iron oxide (iron oxide) with an average particle size of 0.8 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.5:1 and mixed evenly. The mixture was then made into pellets with a diameter of 15-20 mm under a pressure of 10 MPa. After drying, the pellets were placed in an electric furnace and sintered at 950℃ for 2 hours. Then, they were crushed by a jaw crusher and ball-milled for 6 hours using a JM-2L wet ball mill to obtain fine powder with an average particle size of 0.5 micrometers.

[0076] (2) Preparation of coarse powder:

[0077] Iron oxide (iron oxide) with an average particle size of 1.5 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.78:1 and mixed with an appropriate amount of strontium chloride. The mixture was then formed into pellets with a diameter of 15-20 mm under a pressure of 10 MPa. After drying, the pellets were placed in an electric furnace and sintered at 1230℃ for 2 hours. Then, they were crushed by a jaw crusher to obtain coarse powder with an average particle size of 6.0 micrometers.

[0078] (3) Preparation of mixed powder: according to a weight ratio of 45% and a weight ratio of 55%

[0079] The fine powder obtained in step (1) and the coarse powder obtained in step (2) are wet-mixed evenly and then dried to obtain ferrite powder. Then, the powder is densified by a reciprocating vibrating ball mill for 0.5 hours to obtain densified powder. The weight percentage of fine powder is 45% and the weight percentage of coarse powder is 55%.

[0080] The densified powder was annealed in an electric furnace at 950℃, then acid-washed with a 2wt% hydrochloric acid solution to bring its pH value to 6-7, and then dried and crushed to obtain ferrite magnetic powder.

[0081] A bonded magnet is prepared mainly by the following steps:

[0082] 93 parts by weight of the above-mentioned ferrite magnetic powder, 0.5 parts by weight of stabilizer, 0.5 parts by weight of lubricant and 6.0 parts by weight of binder were mixed in a mixer and then extruded and granulated using a twin-screw extruder to obtain granules; wherein the stabilizer is phosphite antioxidant 168, the lubricant is stearamide and the binder is nylon 6.

[0083] The obtained granules were injection molded on an injection molding machine, and the molded sample size was Φ20×10mm, resulting in a bonded magnet.

[0084] The properties of the ferrite magnetic powder and the bonded magnet prepared therefrom in this embodiment are shown in Table 1.

[0085] Performance testing methods include:

[0086] Weigh 15 grams of the obtained ferrite magnetic powder, put it into a cylindrical mold with a diameter of 25 mm, apply a forming pressure of 80 kN to press it into a cylindrical blank, measure the thickness of the blank, and calculate the compressibility.

[0087] 92 parts by weight of ferrite magnetic powder, 0.5 parts by weight of lubricant and 7.5 parts by weight of nylon 6 were mixed in a mixer. The resulting mixture was kneaded at 220-240℃ to produce particles with an average particle size of 3-4 mm. The particles were then used in a melt flow index tester. The extrusion weight was measured within 10 minutes at 270℃ and a load of 10 kg, which is the melt flow rate (unit: g / 10min).

[0088] 92 parts by weight of ferrite magnetic powder, 0.5 parts by weight of lubricant, and 7.5 parts by weight of nylon 6 were mixed in a mixer. The resulting mixture was kneaded at 220-240°C to form particles with an average particle size of 3-4 mm. The particles were then injection molded into cylindrical shapes with a diameter of 20 mm and a height of 10 mm in a magnetic field orientation at 270°C and 8.0 kGS. The magnetic properties were measured using a permanent magnet measuring instrument (the orientation magnetic field direction was parallel to the central axis of the cylinder).

[0089] Table 1

[0090] Remanent magnetic flux density (Br) of bonded magnets mT 293 Intrinsic coercivity (jHc) of bonded magnets kA / m 278 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 16.8 Flowability (MFR) of bonded magnets g / 10min 155 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.75

[0091] Example 2

[0092] A method for preparing ferrite magnetic powder includes the following steps:

[0093] (1) Preparation of fine powder:

[0094] Iron oxide (iron oxide) with an average particle size of 0.4 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.5:1 and mixed evenly. The mixture was then made into pellets with a diameter of 15-20 mm under a pressure of 10 MPa. After drying, the pellets were placed in an electric furnace and sintered at 930℃ for 2 hours. Then, they were crushed by a jaw crusher and ball-milled for 8 hours using a JM-2L wet ball mill to obtain fine powder with an average particle size of 0.2 micrometers.

[0095] (2) Preparation of coarse powder:

[0096] Iron oxide (iron oxide) with an average particle size of 1.5 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.78:1 and mixed evenly with an appropriate amount of strontium chloride. The mixture was then formed into pellets with a diameter of 15-20 mm under a pressure of 10 MPa. After drying, the pellets were placed in an electric furnace and sintered at 1180℃ for 2 hours. Then, they were crushed by a jaw crusher to obtain coarse powder with an average particle size of 4.5 micrometers.

[0097] (3) Preparation of mixed powder:

[0098] The fine powder obtained in step (1) and the coarse powder obtained in step (2) are wet-mixed evenly and then dried to obtain ferrite powder. Then, the powder is densified by a reciprocating vibrating ball mill for 0.5 hours to obtain densified powder. The weight percentage of fine powder is 35% and the weight percentage of coarse powder is 65%.

[0099] The densified powder was annealed in an electric furnace at 950℃, then acid-washed with a 2wt% hydrochloric acid solution to bring its pH value to 6-7, and then dried and crushed to obtain ferrite magnetic powder.

[0100] A bonded magnet is mainly prepared from the above-mentioned ferrite magnetic powder, and the preparation method is the same as in Example 1 to obtain the bonded magnet.

[0101] The properties of the ferrite magnetic powder and the bonded magnet prepared by it provided in this embodiment are shown in Table 2. The test methods are the same as in Embodiment 1.

[0102] Table 2

[0103] Remanent magnetic flux density (Br) of bonded magnets mT 295 Intrinsic coercivity (jHc) of bonded magnets kA / m 285 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 17.1 Flowability (MFR) of bonded magnets g / 10min 160 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.78

[0104] Example 3

[0105] A method for preparing ferrite magnetic powder includes the following steps:

[0106] (1) Preparation of fine powder:

[0107] Same as Example 2;

[0108] (2) Preparation of coarse powder:

[0109] Iron oxide (iron oxide) with an average particle size of 1.5 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.78:1 and mixed with an appropriate amount of strontium chloride. The mixture was then formed into pellets with a diameter of 15-20 mm under a pressure of 10 MPa. After drying, the pellets were placed in an electric furnace and sintered at 1230℃ for 2 hours. Then, they were crushed by a jaw crusher to obtain coarse powder with an average particle size of 6.0 micrometers.

[0110] (3) Preparation of mixed powder:

[0111] The fine powder obtained in step (1) and the coarse powder obtained in step (2) are wet-mixed evenly and then dried to obtain ferrite powder. Then, the powder is densified by a reciprocating vibrating ball mill for 0.5 hours to obtain densified powder. The weight percentage of fine powder is 45% and the weight percentage of coarse powder is 55%.

[0112] The densified powder was annealed in an electric furnace at 950℃, then acid-washed with a 2wt% hydrochloric acid solution to bring its pH value to 6-7, and then dried and crushed to obtain ferrite magnetic powder.

[0113] A bonded magnet is mainly prepared from the above-mentioned ferrite magnetic powder, and the preparation method is the same as in Example 1 to obtain the bonded magnet.

[0114] The properties of the ferrite magnetic powder and the bonded magnet prepared by it provided in this embodiment are shown in Table 3. The test methods are the same as those in Embodiment 1.

[0115] Table 3

[0116] Remanent magnetic flux density (Br) of bonded magnets mT 296 Intrinsic coercivity (jHc) of bonded magnets kA / m 290 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 17.5 Flowability (MFR) of bonded magnets g / 10min 175 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.83

[0117] Example 4

[0118] A method for preparing ferrite magnetic powder includes the following steps:

[0119] (1) Preparation of fine powder:

[0120] Same as Example 2;

[0121] (2) Preparation of coarse powder:

[0122] Iron oxide (iron oxide) with an average particle size of 1.8 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.78:1 and mixed with an appropriate amount of strontium chloride. The mixture was then formed into pellets with a diameter of 15-20 mm under a pressure of 10 MPa. After drying, the pellets were placed in an electric furnace and sintered at 1200℃ for 2 hours. Then, they were crushed by a jaw crusher to obtain coarse powder with an average particle size of 6.0 micrometers.

[0123] (3) Preparation of mixed powder:

[0124] The fine powder obtained in step (1) and the coarse powder obtained in step (2) are wet-mixed evenly and then dried to obtain ferrite powder. Then, the powder is densified by a reciprocating vibrating ball mill for 0.5 hours to obtain densified powder. The weight percentage of fine powder is 45% and the weight percentage of coarse powder is 55%.

[0125] The densified powder was annealed in an electric furnace at 950℃, then acid-washed with a 2wt% hydrochloric acid solution to bring its pH value to 6-7, and then dried and crushed to obtain ferrite magnetic powder.

[0126] A bonded magnet is mainly prepared from the above-mentioned ferrite magnetic powder, and the preparation method is the same as in Example 1 to obtain the bonded magnet.

[0127] The properties of the ferrite magnetic powder and the bonded magnet prepared by it provided in this embodiment are shown in Table 4. The test methods are the same as in Embodiment 1.

[0128] Table 4

[0129] Remanent magnetic flux density (Br) of bonded magnets mT 296 Intrinsic coercivity (jHc) of bonded magnets kA / m 295 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 17.5 Flowability (MFR) of bonded magnets g / 10min 176 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.85

[0130] Example 5

[0131] A method for preparing ferrite magnetic powder includes the following steps:

[0132] (1) Preparation of fine powder:

[0133] Iron oxide (iron oxide) with an average particle size of 0.8 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.5:1 and mixed evenly. The mixture was then made into pellets with a diameter of 15-20 mm under a pressure of 10 MPa. After drying, the pellets were placed in an electric furnace and sintered at 950℃ for 2 hours. Then, they were crushed by a jaw crusher and ball-milled for 8 hours using a JM-2L wet ball mill to obtain fine powder with an average particle size of 0.5 micrometers.

[0134] (2) Preparation of coarse powder:

[0135] Iron oxide (iron oxide) with an average particle size of 1.8 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.78:1 and mixed with an appropriate amount of strontium chloride. The mixture was then formed into pellets with a diameter of 15-20 mm under a pressure of 10 MPa. After drying, the pellets were placed in an electric furnace and sintered at 1200℃ for 2 hours. Then, they were crushed by a jaw crusher to obtain coarse powder with an average particle size of 6.0 micrometers.

[0136] (3) Preparation of mixed powder:

[0137] The fine powder obtained in step (1) and the coarse powder obtained in step (2) are wet-mixed evenly and then dried to obtain ferrite powder. Then, the powder is densified by a reciprocating vibrating ball mill for 0.5 hours to obtain densified powder. The weight percentage of fine powder is 45% and the weight percentage of coarse powder is 55%.

[0138] The densified powder was annealed in an electric furnace at 950℃, then acid-washed with a 2wt% hydrochloric acid solution to bring its pH value to 6-7, and then dried and crushed to obtain ferrite magnetic powder.

[0139] A bonded magnet is mainly prepared from the above-mentioned ferrite magnetic powder, and the preparation method is the same as in Example 1 to obtain the bonded magnet.

[0140] The properties of the ferrite magnetic powder and the bonded magnet prepared by it provided in this embodiment are shown in Table 5. The test methods are the same as in Embodiment 1.

[0141] Table 5

[0142]

[0143]

[0144] Example 6

[0145] A method for preparing ferrite magnetic powder includes the following steps:

[0146] (1) Preparation of fine powder:

[0147] Same as Example 5;

[0148] (2) Preparation of coarse powder:

[0149] Same as Example 5;

[0150] (3) Preparation of mixed powder:

[0151] The fine powder obtained in step (1) and the coarse powder obtained in step (2) are wet-mixed evenly and then dried to obtain ferrite powder. Then, the powder is densified by a reciprocating vibrating ball mill for 0.5 hours to obtain densified powder. The weight percentage of fine powder is 35% and the weight percentage of coarse powder is 65%.

[0152] The densified powder was annealed in an electric furnace at 950℃, then acid-washed with a 2wt% hydrochloric acid solution to bring its pH value to 6-7, and then dried and crushed to obtain ferrite magnetic powder.

[0153] A bonded magnet is mainly prepared from the above-mentioned ferrite magnetic powder, and the preparation method is the same as in Example 1 to obtain the bonded magnet.

[0154] The properties of the ferrite magnetic powder and the bonded magnet prepared by it provided in this embodiment are shown in Table 6. The test methods are the same as in Embodiment 1.

[0155] Table 6

[0156]

[0157]

[0158] Example 7

[0159] A method for preparing ferrite magnetic powder includes the following steps:

[0160] (1) Preparation of fine powder:

[0161] Same as Example 5;

[0162] (2) Preparation of coarse powder:

[0163] Iron oxide (iron oxide) with an average particle size of 1.5 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.78:1 and mixed with an appropriate amount of strontium chloride. The mixture was then formed into pellets with a diameter of 15-20 mm under a pressure of 10 MPa. After drying, the pellets were placed in an electric furnace and sintered at 1230℃ for 2 hours. Then, they were crushed by a jaw crusher to obtain coarse powder with an average particle size of 6.0 micrometers.

[0164] (3) Preparation of mixed powder:

[0165] The fine powder obtained in step (1) and the coarse powder obtained in step (2) are wet-mixed evenly and then dried to obtain ferrite powder. Then, the powder is densified by a reciprocating vibrating ball mill for 0.5 hours to obtain densified powder. The weight percentage of fine powder is 35% and the weight percentage of coarse powder is 65%.

[0166] The densified powder was annealed in an electric furnace at 950℃, then acid-washed with a 2wt% hydrochloric acid solution to bring its pH value to 6-7, and then dried and crushed to obtain ferrite magnetic powder.

[0167] A bonded magnet is mainly prepared from the above-mentioned ferrite magnetic powder, and the preparation method is the same as in Example 1 to obtain the bonded magnet.

[0168] The properties of the ferrite magnetic powder and the bonded magnet prepared by it provided in this embodiment are shown in Table 7. The test methods are the same as in Embodiment 1.

[0169] Table 7

[0170] Remanent magnetic flux density (Br) of bonded magnets mT 295 Intrinsic coercivity (jHc) of bonded magnets kA / m 275 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 17.1 Flowability (MFR) of bonded magnets g / 10min 163 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.79

[0171] Example 8

[0172] A method for preparing ferrite magnetic powder includes the following steps:

[0173] (1) Preparation of fine powder:

[0174] Iron oxide (iron oxide) with an average particle size of 0.4 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.5:1 and mixed evenly. The mixture was then made into pellets with a diameter of 15-20 mm under a pressure of 10 MPa. After drying, the pellets were placed in an electric furnace and sintered at 930℃ for 2 hours. Then, they were crushed by a jaw crusher and ball-milled for 8 hours using a JM-2L wet ball mill to obtain fine powder with an average particle size of 0.2 micrometers.

[0175] (2) Preparation of coarse powder:

[0176] Iron oxide (iron oxide) with an average particle size of 1.5 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.78:1 and mixed evenly with an appropriate amount of strontium chloride. The mixture was then formed into pellets with a diameter of 15-20 mm under a pressure of 15 MPa. After drying, the pellets were placed in an electric furnace and sintered at 1180℃ for 2 hours. Then, they were crushed by a jaw crusher to obtain coarse powder with an average particle size of 4.5 micrometers.

[0177] (3) Preparation of mixed powder:

[0178] The fine powder obtained in step (1) and the coarse powder obtained in step (2) are wet-mixed evenly and then dried to obtain ferrite powder. Then, the powder is densified by a reciprocating vibrating ball mill for 0.5 hours to obtain densified powder. The weight percentage of fine powder is 35% and the weight percentage of coarse powder is 65%.

[0179] The densified powder was annealed in an electric furnace at 950℃, then acid-washed with a 2wt% hydrochloric acid solution to bring its pH value to 6-7, and then dried and crushed to obtain ferrite magnetic powder.

[0180] A bonded magnet is mainly prepared from the above-mentioned ferrite magnetic powder, and the preparation method is the same as in Example 1 to obtain the bonded magnet.

[0181] The properties of the ferrite magnetic powder and the bonded magnet prepared by it provided in this embodiment are shown in Table 8. The test methods are the same as in Embodiment 1.

[0182] Table 8

[0183] Remanent magnetic flux density (Br) of bonded magnets mT 296 Intrinsic coercivity (jHc) of bonded magnets kA / m 288 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 17.2 Flowability (MFR) of bonded magnets g / 10min 166 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.80

[0184] Example 9

[0185] A method for preparing ferrite magnetic powder includes the following steps:

[0186] (1) Preparation of fine powder:

[0187] Iron oxide (iron oxide) with an average particle size of 0.8 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.5:1 and mixed evenly. The mixture was then made into pellets with a diameter of 15-20 mm under a pressure of 15 MPa. After drying, the pellets were placed in an electric furnace and sintered at 950℃ for 2 hours. Then, they were crushed by a jaw crusher and ball-milled for 8 hours using a JM-2L wet ball mill to obtain fine powder with an average particle size of 0.5 micrometers.

[0188] (2) Preparation of coarse powder:

[0189] Iron oxide (iron oxide) with an average particle size of 1.8 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.78:1 and mixed evenly with an appropriate amount of strontium chloride. The mixture was then formed into pellets with a diameter of 15-20 mm under a pressure of 15 MPa. After drying, the pellets were placed in an electric furnace and sintered at 1200℃ for 2 hours. Then, they were crushed by a jaw crusher to obtain coarse powder with an average particle size of 6.0 micrometers.

[0190] (3) Preparation of mixed powder:

[0191] The fine powder obtained in step (1) and the coarse powder obtained in step (2) are wet-mixed evenly and then dried to obtain ferrite powder. Then, the powder is densified by a reciprocating vibrating ball mill for 0.5 hours to obtain densified powder. The weight percentage of fine powder is 45% and the weight percentage of coarse powder is 55%.

[0192] The densified powder was annealed in an electric furnace at 950℃, then acid-washed with a 2wt% hydrochloric acid solution to bring its pH value to 6-7, and then dried and crushed to obtain ferrite magnetic powder.

[0193] A bonded magnet is mainly prepared from the above-mentioned ferrite magnetic powder, and the preparation method is the same as in Example 1 to obtain the bonded magnet.

[0194] The properties of the ferrite magnetic powder and the bonded magnet prepared by it provided in this embodiment are shown in Table 9. The test methods are the same as in Embodiment 1.

[0195] Table 9

[0196] Remanent magnetic flux density (Br) of bonded magnets mT 295 Intrinsic coercivity (jHc) of bonded magnets kA / m 285 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 17.5 Flowability (MFR) of bonded magnets g / 10min 167 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.81

[0197] Example 10

[0198] A method for preparing ferrite magnetic powder includes the following steps:

[0199] (1) Preparation of fine powder:

[0200] Iron oxide (iron oxide) with an average particle size of 0.8 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.5:1 and mixed evenly. The mixture was then made into pellets with a diameter of 15-20 mm under conventional process conditions without pressure. After drying, the pellets were placed in an electric furnace and sintered at 950℃ for 2 hours. They were then crushed by a jaw crusher and ball-milled for 6 hours using a JM-2L wet ball mill to obtain fine powder with an average particle size of 0.5 micrometers.

[0201] (2) Preparation of coarse powder:

[0202] Iron oxide (iron oxide) with an average particle size of 1.5 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.78:1 and mixed evenly with an appropriate amount of strontium chloride. The mixture was then made into pellets with a diameter of 15-20 mm under conventional process conditions without pressure. After drying, the pellets were placed in an electric furnace and sintered at 1230℃ for 2 hours. Then, they were crushed by a jaw crusher to obtain coarse powder with an average particle size of 6.0 micrometers.

[0203] (3) Preparation of mixed powder:

[0204] The fine powder obtained in step (1) and the coarse powder obtained in step (2) are wet-mixed evenly and then dried to obtain ferrite powder. Then, the powder is densified by a reciprocating vibrating ball mill for 0.5 hours to obtain densified powder. The weight percentage of fine powder is 45% and the weight percentage of coarse powder is 55%.

[0205] The densified powder was annealed in an electric furnace at 950℃, then acid-washed with a 2wt% hydrochloric acid solution to bring its pH value to 6-7, and then dried and crushed to obtain ferrite magnetic powder.

[0206] A bonded magnet is mainly prepared from the above-mentioned ferrite magnetic powder, and the preparation method is the same as in Example 1 to obtain the bonded magnet.

[0207] The properties of the ferrite magnetic powder and the bonded magnet prepared by it provided in this embodiment are shown in Table 10. The test method is the same as in Embodiment 1.

[0208] Table 10

[0209]

[0210]

[0211] Example 11

[0212] A method for preparing ferrite magnetic powder includes the following steps:

[0213] (1) Preparation of fine powder:

[0214] Iron oxide (iron oxide) with an average particle size of 0.8 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.5:1 and mixed evenly. The mixture was then made into pellets with a diameter of 15-20 mm under a pressure of 9 MPa. After drying, the pellets were placed in an electric furnace and sintered at 950℃ for 2 hours. Then, they were crushed by a jaw crusher and ball-milled for 6 hours using a JM-2L wet ball mill to obtain fine powder with an average particle size of 0.5 micrometers.

[0215] (2) Preparation of coarse powder:

[0216] Iron oxide (iron oxide) with an average particle size of 1.5 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.78:1 and mixed evenly with an appropriate amount of strontium chloride. The mixture was then made into pellets with a diameter of 15-20 mm under a pressure of 9 MPa. After drying, the pellets were placed in an electric furnace and sintered at 1230℃ for 2 hours. Then, they were crushed by a jaw crusher to obtain coarse powder with an average particle size of 6.0 micrometers.

[0217] (3) Preparation of mixed powder:

[0218] The fine powder obtained in step (1) and the coarse powder obtained in step (2) are wet-mixed evenly and then dried to obtain ferrite powder. Then, the powder is densified by a reciprocating vibrating ball mill for 0.5 hours to obtain densified powder. The weight percentage of fine powder is 45% and the weight percentage of coarse powder is 55%.

[0219] The densified powder was annealed in an electric furnace at 950℃, then acid-washed with a 2wt% hydrochloric acid solution to bring its pH value to 6-7, and then dried and crushed to obtain ferrite magnetic powder.

[0220] A bonded magnet is mainly prepared from the above-mentioned ferrite magnetic powder, and the preparation method is the same as in Example 1 to obtain the bonded magnet.

[0221] The properties of the ferrite magnetic powder and the bonded magnet prepared by it provided in this embodiment are shown in Table 11. The test methods are the same as in Embodiment 1.

[0222] Table 11

[0223] Remanent magnetic flux density (Br) of bonded magnets mT 292 Intrinsic coercivity (jHc) of bonded magnets kA / m 276 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 16.2 Flowability (MFR) of bonded magnets g / 10min 150 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.74

[0224] Example 12

[0225] A method for preparing ferrite magnetic powder includes the following steps:

[0226] (1) Preparation of fine powder:

[0227] Iron oxide (iron oxide) with an average particle size of 0.8 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.5:1 and mixed evenly. The mixture was then made into pellets with a diameter of 15-20 mm under a pressure of 8 MPa. After drying, the pellets were placed in an electric furnace and sintered at 950℃ for 2 hours. Then, they were crushed by a jaw crusher and ball-milled for 6 hours using a JM-2L wet ball mill to obtain fine powder with an average particle size of 0.5 micrometers.

[0228] (2) Preparation of coarse powder:

[0229] Iron oxide (iron oxide) with an average particle size of 1.5 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.78:1 and mixed with an appropriate amount of strontium chloride. The mixture was then formed into pellets with a diameter of 15-20 mm under a pressure of 8 MPa. After drying, the pellets were placed in an electric furnace and sintered at 1230℃ for 2 hours. Then, they were crushed by a jaw crusher to obtain coarse powder with an average particle size of 6.0 micrometers.

[0230] (3) Preparation of mixed powder:

[0231] The fine powder obtained in step (1) and the coarse powder obtained in step (2) are wet-mixed evenly and then dried to obtain ferrite powder. Then, the powder is densified by a reciprocating vibrating ball mill for 0.5 hours to obtain densified powder. The weight percentage of fine powder is 45% and the weight percentage of coarse powder is 55%.

[0232] The densified powder was annealed in an electric furnace at 950℃, then acid-washed with a 2wt% hydrochloric acid solution to bring its pH value to 6-7, and then dried and crushed to obtain ferrite magnetic powder.

[0233] A bonded magnet is mainly prepared from the above-mentioned ferrite magnetic powder, and the preparation method is the same as in Example 1 to obtain the bonded magnet.

[0234] The properties of the ferrite magnetic powder and the bonded magnet prepared by it provided in this embodiment are shown in Table 12. The test methods are the same as in Embodiment 1.

[0235] Table 12

[0236] Remanent magnetic flux density (Br) of bonded magnets mT 292 Intrinsic coercivity (jHc) of bonded magnets kA / m 274 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 16.1 Flowability (MFR) of bonded magnets g / 10min 145 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.72

[0237] Example 13

[0238] A method for preparing ferrite magnetic powder includes the following steps:

[0239] (1) Preparation of fine powder:

[0240] Iron oxide (iron oxide) with an average particle size of 0.8 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.5:1 and mixed evenly. The mixture was then made into pellets with a diameter of 15-20 mm under a pressure of 5 MPa. After drying, the pellets were placed in an electric furnace and sintered at 950℃ for 2 hours. Then, they were crushed by a jaw crusher and ball-milled for 6 hours using a JM-2L wet ball mill to obtain fine powder with an average particle size of 0.5 micrometers.

[0241] (2) Preparation of coarse powder:

[0242] Iron oxide (iron oxide) with an average particle size of 1.5 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.78:1 and mixed evenly with an appropriate amount of strontium chloride. The mixture was then formed into pellets with a diameter of 15-20 mm under a pressure of 5 MPa. After drying, the pellets were placed in an electric furnace and sintered at 1230℃ for 2 hours. Then, they were crushed by a jaw crusher to obtain coarse powder with an average particle size of 6.0 micrometers.

[0243] (3) Preparation of mixed powder:

[0244] The fine powder obtained in step (1) and the coarse powder obtained in step (2) are wet-mixed evenly and then dried to obtain ferrite powder. Then, the powder is densified by a reciprocating vibrating ball mill for 0.5 hours to obtain densified powder. The weight percentage of fine powder is 45% and the weight percentage of coarse powder is 55%.

[0245] The densified powder was annealed in an electric furnace at 950℃, then acid-washed with a 2wt% hydrochloric acid solution to bring its pH value to 6-7, and then dried and crushed to obtain ferrite magnetic powder.

[0246] A bonded magnet is mainly prepared from the above-mentioned ferrite magnetic powder, and the preparation method is the same as in Example 1 to obtain the bonded magnet.

[0247] The properties of the ferrite magnetic powder and the bonded magnet prepared by it provided in this embodiment are shown in Table 13. The test methods are the same as in Embodiment 1.

[0248] Table 13

[0249]

[0250]

[0251] Example 14

[0252] A method for preparing ferrite magnetic powder includes the following steps:

[0253] (1) Preparation of fine powder:

[0254] Iron oxide (iron oxide) with an average particle size of 0.4 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.5:1 and mixed evenly. The mixture was then made into pellets with a diameter of 15-20 mm under a pressure of 10 MPa. After drying, the pellets were placed in an electric furnace and sintered at 930℃ for 2 hours. Then, they were crushed by a jaw crusher and ball-milled for 8 hours using a JM-2L wet ball mill to obtain fine powder with an average particle size of 0.2 micrometers.

[0255] (2) Preparation of coarse powder:

[0256] Iron oxide (iron oxide) with an average particle size of 1.8 micrometers was selected. Iron oxide and strontium carbonate were weighed at a molar ratio of 5.78:1 and mixed with an appropriate amount of strontium chloride. The mixture was then formed into pellets with a diameter of 15-20 mm under a pressure of 10 MPa. After drying, the pellets were placed in an electric furnace and sintered at 1200℃ for 2 hours. Then, they were crushed by a jaw crusher to obtain coarse powder with an average particle size of 6.0 micrometers.

[0257] (3) Preparation of mixed powder:

[0258] The fine powder obtained in step (1) and the coarse powder obtained in step (2) are wet-mixed evenly and then dried to obtain ferrite powder (without densification treatment by a reciprocating vibrating ball mill). The powder has a weight ratio of 45% for fine powder and 55% for coarse powder.

[0259] The obtained powder was annealed in an electric furnace at 950℃, then acid-washed with 2wt% hydrochloric acid solution to bring its pH value to 6-7, and then dried and crushed to obtain ferrite magnetic powder.

[0260] A bonded magnet is mainly prepared from the above-mentioned ferrite magnetic powder, and the preparation method is the same as in Example 1 to obtain the bonded magnet.

[0261] The properties of the ferrite magnetic powder and the bonded magnet prepared by it provided in this embodiment are shown in Table 14. The test methods are the same as in Embodiment 1.

[0262] Table 14

[0263] Remanent magnetic flux density (Br) of bonded magnets mT 294 Intrinsic coercivity (jHc) of bonded magnets kA / m 285 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 17.3 Flowability (MFR) of bonded magnets g / 10min 166 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.78

[0264] Example 15

[0265] The difference between this embodiment and embodiment 1 is that the average particle size of the iron oxide raw material used in step (1) of this embodiment is 1.0 micrometers. All other aspects are the same as in embodiment 1. The properties of the obtained ferrite magnetic powder and the bonded magnet prepared therefrom are shown in Table 15.

[0266] Table 15

[0267] Remanent magnetic flux density (Br) of bonded magnets mT 290 Intrinsic coercivity (jHc) of bonded magnets kA / m 245 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 15.8 Flowability (MFR) of bonded magnets g / 10min 102 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.65

[0268] Example 16

[0269] The difference between this embodiment and embodiment 1 is that the average particle size of the iron oxide raw material used in step (2) of this embodiment is 1.2 micrometers. All other aspects are the same as in embodiment 1. The properties of the obtained ferrite magnetic powder and the bonded magnet prepared therefrom are shown in Table 16.

[0270] Table 16

[0271] Remanent magnetic flux density (Br) of bonded magnets mT 289 Intrinsic coercivity (jHc) of bonded magnets kA / m 255 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 15.5 Flowability (MFR) of bonded magnets g / 10min 95 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.60

[0272] Example 17

[0273] The difference between this embodiment and embodiment 1 is that the sintering temperature in step (1) of this embodiment is 900℃, while the rest is the same as in embodiment 1. The properties of the obtained ferrite magnetic powder and the bonded magnet prepared therefrom are shown in Table 17.

[0274] Table 17

[0275] Remanent magnetic flux density (Br) of bonded magnets mT 281 Intrinsic coercivity (jHc) of bonded magnets kA / m 220 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 14.5 Flowability (MFR) of bonded magnets g / 10min 110 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.68

[0276] Example 18

[0277] The difference between this embodiment and embodiment 1 is that the sintering temperature in step (1) of this embodiment is 1000℃, while the rest is the same as in embodiment 1. The properties of the obtained ferrite magnetic powder and the bonded magnet prepared therefrom are shown in Table 18.

[0278] Table 18

[0279] Remanent magnetic flux density (Br) of bonded magnets mT 290 Intrinsic coercivity (jHc) of bonded magnets kA / m 249 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 15.3 Flowability (MFR) of bonded magnets g / 10min 90 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.61

[0280] Example 19

[0281] The difference between this embodiment and embodiment 1 is that the sintering temperature in step (2) of this embodiment is 1000℃, while the rest is the same as in embodiment 1. The properties of the obtained ferrite magnetic powder and the bonded magnet prepared therefrom are shown in Table 19.

[0282] Table 19

[0283] Remanent magnetic flux density (Br) of bonded magnets mT 280 Intrinsic coercivity (jHc) of bonded magnets kA / m 263 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 14.4 Flowability (MFR) of bonded magnets g / 10min 85 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.55

[0284] Example 20

[0285] The difference between this embodiment and embodiment 1 is that the sintering temperature in step (2) of this embodiment is 1300℃, while the rest is the same as in embodiment 1. The properties of the obtained ferrite magnetic powder and the bonded magnet prepared therefrom are shown in Table 20.

[0286] Table 20

[0287] Remanent magnetic flux density (Br) of bonded magnets mT 290 Intrinsic coercivity (jHc) of bonded magnets kA / m 230 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 15,0 Flowability (MFR) of bonded magnets g / 10min 115 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.69

[0288] Comparative Example 1

[0289] The difference between this comparative example and Example 1 is that the weight percentage of fine powder in the ferrite magnetic powder of this comparative example is 50%, the weight percentage of coarse powder is 50%, and the rest is the same as in Example 1. The properties of the obtained ferrite magnetic powder and the bonded magnet prepared therefrom are shown in Table 21.

[0290] Table 21

[0291] Remanent magnetic flux density (Br) of bonded magnets mT 290 Intrinsic coercivity (jHc) of bonded magnets kA / m 285 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 16.0 Flowability (MFR) of bonded magnets g / 10min 118 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.69

[0292] Comparative Example 2

[0293] The difference between this comparative example and Example 1 is that the weight percentage of fine powder in the ferrite magnetic powder of this comparative example is 30%, the weight percentage of coarse powder is 70%, and the rest is the same as in Example 1. The properties of the obtained ferrite magnetic powder and the bonded magnet prepared therefrom are shown in Table 22.

[0294] Table 22

[0295] Remanent magnetic flux density (Br) of bonded magnets mT 291 Intrinsic coercivity (jHc) of bonded magnets kA / m 265 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 16.1 Flowability (MFR) of bonded magnets g / 10min 123 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3,70

[0296] Comparative Example 3

[0297] The difference between this comparative example and Example 1 is that the average particle size of the fine powder obtained in step (1) of this comparative example is 0.1 micrometers. The rest is the same as in Example 1. The properties of the ferrite magnetic powder obtained and the bonded magnet prepared therefrom are shown in Table 23.

[0298] Table 23

[0299] Remanent magnetic flux density (Br) of bonded magnets mT 290 Intrinsic coercivity (jHc) of bonded magnets kA / m 272 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 16.2 Flowability (MFR) of bonded magnets g / 10min 138 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.72

[0300] Comparative Example 4

[0301] The difference between this comparative example and Example 1 is that the average particle size of the fine powder obtained in step (1) of this comparative example is 0.6 micrometers. The rest is the same as in Example 1. The properties of the ferrite magnetic powder obtained and the bonded magnet prepared therefrom are shown in Table 24.

[0302] Table 24

[0303] Remanent magnetic flux density (Br) of bonded magnets mT 291 Intrinsic coercivity (jHc) of bonded magnets kA / m 252 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 16.2 Flowability (MFR) of bonded magnets g / 10min 114 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.69

[0304] Comparative Example 5

[0305] The difference between this comparative example and Example 1 is that the average particle size of the coarse powder obtained in step (2) of this comparative example is 4.0 micrometers. The rest are the same as in Example 1. The properties of the ferrite magnetic powder obtained and the bonded magnet prepared therefrom are shown in Table 25.

[0306] Table 25

[0307] Remanent magnetic flux density (Br) of bonded magnets mT 288 Intrinsic coercivity (jHc) of bonded magnets kA / m 269 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 15.8 Flowability (MFR) of bonded magnets g / 10min 92 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.62

[0308] Comparative Example 6

[0309] The difference between this comparative example and Example 1 is that the average particle size of the coarse powder obtained in step (2) of this comparative example is 7.0 micrometers. The rest are the same as in Example 1. The properties of the ferrite magnetic powder obtained and the bonded magnet prepared therefrom are shown in Table 26.

[0310] Table 26

[0311] Remanent magnetic flux density (Br) of bonded magnets mT 289 Intrinsic coercivity (jHc) of bonded magnets kA / m 249 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 15.2 Flowability (MFR) of bonded magnets g / 10min 126 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.71

[0312] Comparative Example 7

[0313] The difference between this comparative example and Example 1 is that densification treatment was not performed in step (3) of this comparative example. All other steps are the same as in Example 1. The properties of the ferrite magnetic powder obtained and the bonded magnet prepared therefrom are shown in Table 27.

[0314] Table 27

[0315] Remanent magnetic flux density (Br) of bonded magnets mT 286 Intrinsic coercivity (jHc) of bonded magnets kA / m 261 The maximum magnetic energy product of bonded magnets ((BH)max) <![CDATA[kJ / m 3 ]]> 14.9 Flowability (MFR) of bonded magnets g / 10min 78 Compressibility of ferrite magnetic powder <![CDATA[g / cm 3 ]]> 3.53

[0316] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A ferrite magnetic powder, characterized by, The compressed density of the ferrite magnetic powder is 3.75-3.85 g / cm 3 ; The method for preparing the ferrite magnetic powder includes the following steps: (a) The ferrite powder is densified to obtain a densified powder; (b) The densified powder is annealed and crushed to obtain the ferrite magnetic powder; The ferrite powder includes fine powder with an average particle size of 0.2-0.5 micrometers and coarse powder with an average particle size of 4.5-6.0 micrometers; The fine powder accounts for 35-45% by weight. Both the fine powder and the coarse powder independently comprise iron oxide red and additives; The densification process includes ball milling. The densification process includes the following steps: The ferrite powder was ball-milled using a reciprocating vibratory ball mill to obtain a densified powder. The method for preparing the fine powder includes the following steps: After mixing the first iron oxide red and the additives, the mixture is densely pelletized and sintered to obtain the fine powder. The average particle size of the first iron oxide red is less than 0.8 micrometers; The temperature of the first sintering is 930-950 ℃; The method for preparing the coarse powder includes the following steps: The second iron oxide red and additives are mixed and densely pelletized, followed by a second sintering to obtain the coarse powder; The average particle size of the second iron oxide red is above 1.50 micrometers; The second sintering temperature is 1180-1230 ℃; The method of dense pelletizing includes applying pressure to form pellets; The applied pressure is above 10 MPa; The additive includes at least one of strontium carbonate and strontium chloride.

2. A bonded magnet characterized by, The bonded magnet comprises the ferrite magnetic powder as described in claim 1.

3. The bonded magnet according to claim 2, characterized by The intrinsic coercivity of the bonded magnet is above 275 kA / m.

4. The bonded magnet according to claim 2, characterized in that, The residual magnetic induction intensity of the bonded magnet is above 293 mT.

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