A method for removing silicon impurities in high-silicon iron red for permanent magnet ferrite and a method for preparing permanent magnet ferrite using high-silicon iron red

Abstract

The application relates to the technical field of permanent magnet ferrite preparation, and discloses a method for removing silicon impurities in high-silicon iron red for permanent magnet ferrite, which comprises the following steps: mixing high-silicon iron red and sodium hydroxide, heating to make the sodium hydroxide melt and react; centrifuging the molten lye and the high-silicon iron red after the reaction; cooling, rinsing the solid, and drying.The technical scheme of the application solves the problem that the high-silicon iron red cannot be directly used to prepare high-performance permanent magnet ferrite due to the too high silicon content, the provided method for removing silicon impurities in the high-silicon iron red can effectively remove the contained silicon dioxide, silicon carbide and other impurities, and the preparation of high-performance permanent magnet ferrite is met; the performance of the prepared permanent magnet ferrite is similar to that prepared by using low-silicon-content iron red; the iron red raw material source for preparing the permanent magnet ferrite is greatly expanded; and the cost of the iron red raw material is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of permanent magnet ferrite preparation, in particular to a method for removing silicon impurities in high-silicon iron red for permanent magnet ferrite and a method for preparing permanent magnet ferrite using high-silicon iron red. BACKGROUND

[0002] Permanent magnet ferrite, also known as hard magnetic ferrite, is widely used in many fields such as automobile DC motor, starting motor, inductor, audio transformer, separator, etc. With the development of science and technology, more and more devices require miniaturization, light weight, energy saving and high efficiency, and as an important permanent magnet material in many devices, permanent magnet ferrite is required to have better performance. In the manufacturing method of permanent magnet ferrite, the most critical factor is the raw material and the ratio of the raw material, which directly affects the subsequent forming process and sintering process. The main raw material of permanent magnet ferrite is iron red, and the purity, impurity content and particle size of iron red all affect the performance of permanent magnet ferrite.

[0003] At present, the iron oxide red used as the raw material for ferrite production mainly comes from the regeneration process of cold-rolled silicon steel pickling waste liquid of steel enterprises. The iron oxide red obtained by this system contains silicon dioxide, silicon carbide and other silicon impurities. The purity of iron red used for preparing permanent magnet ferrite is generally not less than 99.2wt%, and the silicon impurity content is within 0.1mol / L. However, the silicon impurity content in the iron red products of many steel plants is more than 0.2wt%, and some is as high as 4wt%, which cannot meet the requirements of high-performance permanent magnet ferrite, and increases the difficulty of preparing permanent magnet ferrite. Therefore, how to process high-silicon iron red to meet the preparation requirements of permanent magnet ferrite and achieve the effect of expanding the source of iron red and reducing the cost is obviously an important technical problem currently faced.

[0004] A method for removing impurities from cold-rolled silicon steel iron oxide red is disclosed in Chinese patent application CN103950988A, that is, using 30-60% sodium hydroxide solution to alkali wash the cold-rolled silicon steel iron oxide red at a temperature of 140-200℃, but this method can only remove silicon dioxide in the iron oxide red, and cannot remove non-soluble impurities such as silicon carbide, so the treated iron oxide red cannot meet the preparation requirements of high-performance permanent magnet ferrite. SUMMARY

[0005] In view of the problem that the high silicon impurity content in the current iron red product cannot meet the preparation requirements of high-performance permanent magnet ferrite, the purpose of the present application is to provide a method for removing silicon impurities in high-silicon iron red for permanent magnet ferrite, which can effectively remove silicon impurities such as silicon dioxide and silicon carbide, and meet the performance requirements of permanent magnet ferrite.

[0006] Another purpose of the present application is to provide a method for preparing permanent magnet ferrite using high-silicon iron red, which can prepare permanent magnet ferrite from the treated high-silicon iron red, and the performance of the obtained permanent magnet ferrite is better.

[0007] The present application provides the following technical solutions:

[0008] A method for removing silicon impurities in high-silicon iron red for permanent magnet ferrite, comprising the following steps:

[0009] (1-1) mixing high-silicon iron red with sodium hydroxide and heating to melt the sodium hydroxide and react;

[0010] (1-2) centrifuging the molten alkali liquor and high-silicon iron red after reaction;

[0011] (1-3) cooling, rinsing the solid, and drying.

[0012] The performance of permanent magnet ferrite is directly related to the performance of iron red. High-performance permanent magnet ferrite requires not only low silicon impurity content in iron red, but also low silicon carbide content, which leads to the fact that iron red used in other fields may not be suitable for permanent magnet ferrite. The silicon content in the iron red on the market is high, mainly in the form of silicon dioxide, silicon carbide, and silicate compounds, which seriously affects the performance of permanent magnet ferrite products and cannot meet the preparation of high-quality permanent magnet ferrite. After research by the inventors, sodium hydroxide solid is mixed with iron red, heated to melt the sodium hydroxide solid, and fully contacted with iron red particles to react with silicon dioxide, silicon carbide, and other impurities in iron red to convert silicon dioxide, silicon carbide, and other impurities in high-silicon iron red into soluble salt solids such as sodium silicate and sodium chloride. Then, most of the alkali and converted impurities are separated by centrifugation, and the residue is further cleaned. The specific reaction process is as follows:

[0013] 2NaOH + SiO2 → Na2SiO3 + H2O

[0014] SiC + 2NaOH (molten) + 2O2 → Na2SiO3 + CO2 + H2O

[0015] The above process can effectively remove silicon dioxide, silicon carbide, and other impurities in high-silicon iron red. Compared with sodium hydroxide, potassium hydroxide avoids the introduction of potassium impurities. The obtained iron red raw material can be used for the preparation of permanent magnet ferrite, and the performance of the prepared permanent magnet ferrite is similar to that of iron red raw material with low silicon content (silicon content ≤ 0.1%).

[0016] As a preferred method of the present application, the silicon content of high-silicon iron red in step (1-1) is ≥ 0.2 wt%. Preferably, it is 0.5 wt% to 4.5 wt%.

[0017] As a preferred method of the present application, the mass ratio of high-silicon iron red to sodium hydroxide in step (1-1) is 1:0.2 to 0.6. The preferred mass ratio is 1:0.3 to 0.4.

[0018] As a preferred method of the present application, the temperature of the heating reaction in step (1-1) is 350-460°C. The reaction time is preferably ≥ 2 h, more preferably 2-4 h.

[0019] As a preferred method of the present application, the centrifugal separation rate in step (1-2) is 2000-20000 r / min.

[0020] As a preferred method of the present application, sodium bicarbonate solution is used for rinsing in step (1-3). Rinsing with sodium bicarbonate solution inhibits the hydrolysis of sodium silicate on one hand, and rinses away sodium silicate, sodium chloride, etc. on the other hand, which is more conducive to improving the performance of the prepared permanent ferrite than water rinsing. Moreover, compared with sodium carbonate solution, sodium bicarbonate is less alkaline, with a pH ≤ 8.4, and has little effect on the acidic iron red. The concentration of sodium bicarbonate is preferably ≤ 1 mol / L, more preferably 0.01-0.1 mol / L. The mass ratio of sodium bicarbonate solution to iron red is preferably 8-10:1.

[0021] A method for preparing permanent ferrite using high-silicon iron red, comprising the following steps:

[0022] (2-1) treating the high-silicon iron red with the removal method of any one of claims 1 to 6 to obtain an iron red raw material;

[0023] (2-2) mixing the iron red raw material with strontium carbonate at a molar ratio of 5.6-6.5:1 to obtain a mixture, adding 0-5 wt% of an additive based on the mass of the mixture, and then adding a ball milling liquid at a mass ratio of 1:1-1.2 to uniformly ball mill the mixture to obtain a slurry, and drying the slurry;

[0024] (2-3) pre-baking the dried slurry at 1200-1320°C for 1-3 h to obtain a pre-baked material;

[0025] (2-4) coarsely crushing the pre-baked material, adding a ball milling liquid and 0-9 wt% of an additive based on the mass of the pre-baked material, and ball milling to obtain a fine slurry;

[0026] (2-5) dehydrating the fine slurry by standing, and pressing into a shape, and sintering at 1180-1280°C for 1-2 h to obtain a permanent ferrite.

[0027] In the above preparation process, the pre-baking temperature is preferably 1270-1310°C, and the time is preferably 1-2 h; and the sintering temperature is preferably 1220-1270°C.

[0028] As a preferred method of the present application,

[0029] The additive in step (2-2) is one or more of silicon oxide, calcium carbonate or aluminum trioxide;

[0030] The ball milling liquid in step (2-2) is water, and the particle size of the slurry after ball milling is 0.6-1.5 um.

[0031] As a preferred method of the present application,

[0032] The average particle size of the pre-fired material after coarse crushing in step (2-4) is 3-5 um;

[0033] The additive in step (2-4) is strontium carbonate, one or a mixture of several of silicon dioxide, aluminum oxide, calcium carbonate, boric acid;

[0034] The particle size of the fine material slurry in step (2-4) is 0.6-1 um.

[0035] As a preferred method of the present application,

[0036] In step (2-5), wet pressing is used, the molding magnetic field strength is 9000-11000 Oe, and the pressure is 3-5 MPa;

[0037] The sintering temperature in step (2-5) is 1220-1270℃, and the holding time is 1-2h.

[0038] The beneficial effects of the present application are as follows:

[0039] The technical scheme of the present application solves the problem that high-silicon iron red is difficult to be directly used for manufacturing high-performance permanent magnet ferrite due to too high silicon content, and the provided method for removing silicon impurities from high-silicon iron red can effectively remove impurities such as silicon dioxide and silicon carbide, meet the preparation of high-performance permanent magnet ferrite, and the performance of the prepared permanent magnet ferrite is similar to that prepared using low-silicon iron red, greatly expanding the source of iron red raw materials for preparing permanent magnet ferrite and reducing the cost of iron red raw materials. DETAILED DESCRIPTION

[0040] The specific embodiments of the present application will be further described below.

[0041] Unless otherwise specified, the raw materials used in the present application can be purchased from the market or commonly used in the art, and unless otherwise specified, the methods in the following examples are conventional methods in the art.

[0042] Example 1

[0043] The method for preparing permanent magnet ferrite using high-silicon iron red is as follows:

[0044] (1) Pretreatment of iron red: mix 1.6wt% silicon-containing iron oxide red and sodium hydroxide solid at a mass ratio of 1:0.3 and stir; then heat the mixture at 380℃ for 2h, and after reaction, separate the alkali and iron oxide red solid by centrifuge at 2000r / min;

[0045] (2) The separated red iron oxide solid is loaded into a stirring tank, 8 times the mass of red iron oxide is added into 0.1 mol / L NaHCO3 aqueous solution, and stirring is performed for 8 min. The stirred red iron oxide turbid liquid is sent into a diaphragm filter press for pressure filtration and dehydration, and the slurry after being rinsed twice is dried by a hot air flow to obtain a main material, and the silicon ion content in the main material is 0.12%;

[0046] (3) Preparation of pre-sintered raw material SrO-MFe2O3: the main material (calculated as red iron oxide) obtained in step 2 is mixed with strontium carbonate at a ratio of 5.95 moles of M, 0.1% of calcium carbonate is added as a mixing agent, and water is added at a mass ratio of 1:1. The uniform powder is obtained by ball milling, and the particle size is 1.0 um. Then, the pre-sintered material is obtained by drying at a temperature of 100°C.

[0047] (4) Pre-sintering: the green permanent magnet ferrite material is placed in a box furnace, and the temperature is raised to 1290°C at a rate of 2°C / min, and the pre-sintered material is obtained after being kept at this temperature for 60 min.

[0048] (5) Secondary ball milling: the pre-sintered material is coarsely crushed, and the coarse powder particle size is 4 um. 1% of calcium carbonate, 0.6% of strontium carbonate, 0.35% of silicon dioxide, and 0.2% of boric acid are added, and the fine slurry with a particle size of 0.8 um is obtained by ball milling.

[0049] (6) Sintering: the secondary ball milled slurry is pressed into a blank at a pressure of 4 MPa and placed in a box furnace. The magnetic field strength is 10000 Oe, the temperature is raised to 1260°C at a rate of 2°C / min, and the sintered material is obtained after being kept at this temperature for 60 min.

[0050] Example 2

[0051] The difference from Example 1 is that:

[0052] The silicon content of the red iron oxide in step (1) is 0.7 wt%;

[0053] The silicon ion content in the main material of the main material in step (2) is 0.06%.

[0054] Example 3

[0055] The difference from Example 1 is that:

[0056] The silicon content of the red iron oxide in step (1) is 2.8 wt%;

[0057] The silicon ion content in the main material of the main material in step (2) is 0.14%.

[0058] Example 4

[0059] The difference from Example 1 is that the melting reaction temperature in step (1) is 350°C, and the silicon ion content in the obtained main material is 0.13%.

[0060] Example 5

[0061] The difference from Example 1 is that the melting reaction temperature in step (1) is 400℃, and the silicon ion content in the obtained main material is 0.09%.

[0062] Example 6

[0063] The difference from Example 1 is that M in step (3) is 6.15.

[0064] Example 7

[0065] The difference from Example 1 is that an equal amount of water is used to replace the sodium bicarbonate solution in step (2).

[0066] Example 8

[0067] The method for preparing permanent magnet ferrite using high-silicon iron red is as follows:

[0068] (1) Pretreatment of iron red: iron oxide red containing 1.6wt% silicon and sodium hydroxide solid are mixed by stirring according to a mass ratio of 1:0.6; then the mixture is heated and reacted at 380℃ for 4h, after the reaction, the alkali and iron oxide red solid are quickly separated by a high-temperature centrifuge at 3000r / min, and attention should be paid to heat insulation treatment and quick operation during the operation;

[0069] (2) The separated iron oxide red solid is loaded into a stirring tank, 0.1mol / L NaHCO3 aqueous solution with 10 times the mass of the iron oxide red is added, and stirring is performed for 10min; the stirred iron oxide red turbid liquid is sent to a diaphragm filter press for pressure filtration and dehydration, and rinsed once; the slurry after being rinsed twice is dried by hot airflow to obtain a main material, and the silicon ion content in the main material is 0.11%;

[0070] (3) Preparation of pre-sintered raw material SrO·MFe2O3: the main material (calculated based on iron oxide red) obtained in step 2 is mixed with the ingredients according to a molar ratio of M of 5.95, calcium carbonate with a mass of 0.1% of the mixed material is added, and water is added according to a mass ratio of 1:1.2; the uniform powder is obtained by ball milling, and the particle size is 0.6um; then the pre-sintered material mixture is obtained by drying at a temperature of 100℃;

[0071] (4) Pre-sintering: the permanent magnet ferrite raw material is placed in a box-type furnace, heated to 1310℃ at a rate of 2℃ / min, and kept for 90min to obtain a pre-sintered material;

[0072] (5) Secondary ball milling: the pre-sintered material is coarsely crushed and broken, the coarse powder particle size is 5um, calcium carbonate 1%, strontium carbonate 0.6%, silicon dioxide 0.35%, and boric acid 0.2% are added, and the fine slurry with a particle size of 0.6um is prepared by ball milling;

[0073] (6) Sintering: The secondary ball-milled slurry was pressed into a green body at 3 MPa and put into a box furnace with a magnetic field strength of 11000 Oe. The temperature was raised to 1220°C at a rate of 2°C / min and held for 120 min.

[0074] Example 9

[0075] The method for preparing permanent magnet ferrite using high-silicon iron red comprises the following steps:

[0076] (1) Pretreatment of iron red: iron oxide red containing 1.6wt% silicon and sodium hydroxide solid were mixed by stirring according to a mass ratio of 1:0.4. Then the mixture was heated at 380°C for 3h. After the reaction, the alkali and iron oxide red solid were quickly separated by a high-temperature centrifuge at 2000r / min. During the operation, attention should be paid to heat insulation treatment and quick operation.

[0077] (2) The separated iron oxide red solid was loaded into a stirring tank, 0.1 mol / L NaHCO3 aqueous solution was added in an amount of 9 times the mass of the iron oxide red, and stirring was performed for 15 min. The stirred iron oxide red slurry was sent to a diaphragm filter press for dewatering, and rinsing was repeated once. The slurry after two rinses was dried by hot gas flow to obtain a main material, and the silicon ion content in the main material was 0.12%.

[0078] (3) Preparation of pre-sintered raw material SrO·MFe2O3: The main material obtained in step 2 (calculated as iron oxide red) was mixed with the ingredients according to a ratio of M being 5.95 moles, calcium carbonate was added in an amount of 0.1% of the mixing mass, and water was added in a mass ratio of 1:1.1. The uniform powder was obtained by ball milling, and the particle size was 0.6um. Subsequently, the pre-sintered material mixture was obtained by drying at a temperature of 100°C.

[0079] (4) Pre-sintering: The permanent magnet ferrite green material was put into a box furnace, the temperature was raised to 1200°C at a rate of 2°C / min, and the temperature was held for 180 min to obtain the pre-sintered material.

[0080] (5) Secondary ball milling: The pre-sintered material was coarsely crushed, and the coarse powder particle size was 3um. Calcium carbonate was added in an amount of 1%, strontium carbonate was added in an amount of 0.6%, silicon dioxide was added in an amount of 0.35%, and boric acid was added in an amount of 0.2%. The fine slurry with a particle size of 1um was prepared by ball milling.

[0081] (6) Sintering: The secondary ball-milled slurry was pressed into a green body at 5 MPa and put into a box furnace with a magnetic field strength of 9000 Oe. The temperature was raised to 1180°C at a rate of 2°C / min and held for 120 min.

[0082] Comparative Example 1

[0083] The method for preparing permanent magnet ferrite using high-silicon iron red comprises the following steps:

[0084] (1) Pretreatment of red iron oxide: red iron oxide containing 1.6wt% silicon was mixed with sodium hydroxide solid at a mass ratio of 1:0.3 by stirring; then the mixture was heated at 380°C for 2h, and after the reaction, the alkali and red iron oxide solid were rapidly separated by centrifuge at 8000r / min;

[0085] (2) The separated red iron oxide solid was loaded into a stirring tank, 0.1 mol / L NaHCO3 aqueous solution was added at 8 times the mass of the red iron oxide, and the mixture was stirred for 8 min. The stirred red iron oxide slurry was sent to a diaphragm filter press for dewatering, and rinsed once. The slurry after two rinses was dried by hot air flow to obtain the main material, and the silicon ion content in the main material was 0.12%;

[0086] (3) Preparation of pre-sintered raw material SrO-MFe2O3: the main material (calculated as red iron oxide) obtained in step 2 was mixed with the ingredients at a ratio of M being 5.95 moles, calcium carbonate was added at 0.1% of the mass of the mixture, and water was added at a mass ratio of 1:1. The mixture was ball milled to obtain a uniform powder with a particle size of 1.0um, and then dried at 100°C to obtain the pre-sintered material mixture;

[0087] (4) Pre-sintering: the permanent magnet ferrite raw material was placed in a box furnace, heated to 1290°C at a rate of 2°C / min, and held for 60 min to obtain the pre-sintered material;

[0088] (5) Secondary ball milling: the pre-sintered material was coarsely crushed, with a coarse powder particle size of 4um, calcium carbonate 1%, strontium carbonate 0.6%, silicon dioxide 0.35%, and boric acid 0.2% were added, and the fine slurry with a particle size of 0.8um was prepared by ball milling;

[0089] (6) Sintering: the secondary ball milled slurry was pressed into a blank at 4MPa and placed in a box furnace, heated to 1260°C at a rate of 2°C / min, and held for 60 min.

[0090] The difference from Example 1 is that red iron oxide with a silicon content of 0.08% was used to prepare direct permanent magnet ferrite according to steps (3)-(6).

[0091] Comparative Example 2

[0092] The difference from Example 1 is that red iron oxide containing 1.6wt% silicon was used to prepare permanent magnet ferrite according to steps (3)-(6).

[0093] Comparative Example 3

[0094] The difference from Example 1 is that the iron oxide red containing 1.6% silicon is stirred with 30 wt% sodium hydroxide solution at 140°C in a mass ratio of 1:5, and the alkali solution and the iron oxide red solid are separated by a centrifuge, the separated iron oxide red solid is loaded into a stirring tank, 0.1 mol / L NaHCO3 aqueous solution is added in an amount of 8 times the mass of the iron oxide red, and stirring is performed for 8 min, the stirred iron oxide red slurry is sent to a diaphragm filter press for pressure filtration and dehydration, and the slurry is rinsed once more, the rinsed twice slurry is dried by a hot air stream, and the main material is obtained.

[0095] Comparative Example 4

[0096] The difference from Example 1 is that the step (1) is not separated by a centrifuge after the melting reaction.

[0097] Comparative Example 5

[0098] The difference from Example 1 is that 0.1 mol / L sodium carbonate solution is used instead of sodium bicarbonate aqueous solution in step (2).

[0099] The properties of the permanent ferrite magnets prepared in the above examples and comparative examples are shown in Table 1 below.

[0100] Table 1 Properties of each permanent ferrite magnet

[0101]

[0102] Note: The Fe2O3% values in the table are the purity of the iron oxide red used in step (3).

[0103] The permanent magnet ferrite prepared by using the iron oxide red product with 0.08wt% silicon content as Comparative Example 1, and the performance of the obtained permanent magnet ferrite can be used as a reference of the permanent magnet ferrite prepared by the technical scheme of the present application. As can be seen from the above table, the performance of the permanent magnet ferrite prepared by using the high-silicon iron red treated by the technical scheme of the present application is not much different from that of the permanent magnet ferrite prepared by using the low-silicon iron red product, indicating that the activity of the iron oxide red obtained by the technical scheme of the present application is not much different from that of the low-silicon iron oxide red product, and the method is feasible. Specifically, as can be found by comparing Example 1 and Comparative Example 2, the silicon impurity content of the treated iron red is significantly reduced, the adaptability and activity of the raw material are increased, the particle size and fluidity of the slurry are improved, the solid phase reaction is more sufficient, and thus the performance of the material is significantly improved; as can be found by comparing Comparative Examples 1-3, the higher the silicon impurity content in the iron red, the greater the influence on the residual magnetism of the ferrite; as can be found by comparing Comparative Examples 1, 4 and 5, with the increase of the melting temperature, the silicon impurity content is reduced, and the temperature is conducive to reducing the silicon impurity content in the iron oxide red; as can be found by comparing Comparative Examples 1 and 3, the iron oxide red treated by hot soaking with sodium hydroxide aqueous solution is not suitable for the preparation of permanent magnet ferrite, mainly because some silicon carbide and other impurities are not completely removed, and these impurities play a role of nails in the subsequent sintering process, resulting in high coercivity, but the residual magnetism is reduced due to the increase of impurities; as can be found by comparing Comparative Examples 1 and 7, the residual magnetism of the permanent magnet ferrite prepared in Example 1 is higher, which indicates that the activity of the iron oxide red obtained by rinsing with sodium bicarbonate aqueous solution is higher than that obtained by rinsing with water. As can be seen by comparing Comparative Examples 1 and 4, centrifugal separation can separate most of the impurities, avoid the residue after sodium bicarbonate rinsing, and improve the performance of the permanent magnet ferrite. As can be seen by comparing Comparative Example 1 and Comparative Example 5, the effect of rinsing with sodium carbonate is not good, mainly because sodium carbonate is more alkaline than sodium bicarbonate, which affects the activity of the iron oxide red.

Claims

1. A method for removing silicon impurities from high-silicon iron red used in permanent magnet ferrites, characterized in that, Includes the following steps: (1-1) High-silicon iron red is mixed with sodium hydroxide and heated to melt the sodium hydroxide and react. The silicon content in the high-silicon iron red is ≥0.2wt%. (1-2) After the reaction, the molten alkali solution and high-silicon iron red are separated by centrifugation; (1-3) Cool down and rinse the solid, dry it, and rinse it with sodium bicarbonate solution.

2. The removal method according to claim 1, characterized in that, In step (1-1), the mass ratio of high-silicon iron red to sodium hydroxide is 1:0.2 to 0.

6.

3. The removal method according to claim 1, characterized in that, The heating temperature in step (1-1) is 350-460℃.

4. The removal method according to claim 1, characterized in that, The centrifugation rate in steps (1-2) is 2000-20000 r / min.

5. A method for preparing permanent magnet ferrite using high-silicon iron red, characterized in that, Includes the following steps: (2-1) The high-silicon iron red raw material is prepared by treating it with a silicon impurity removal method, wherein the silicon impurity removal method is the silicon impurity removal method for high-silicon iron red for permanent magnet ferrite as described in any one of claims 1 to 4; (2-2) Mix iron oxide raw material with strontium carbonate at a molar ratio of 5.6 to 6.5:1 to obtain a mixture, add 0 to 5 wt% of the additives by mass of the mixture, and then add ball milling liquid at a mass ratio of 1:1 to 1.

2. Ball mill the mixture evenly to obtain a slurry, and then dry it. (2-3) The slurry dried by pre-firing at 1200-1320℃ for 1-3 hours is used to obtain pre-fired material; (2-4) Coarsely crushed pre-calcined material, add ball milling liquid and additives with a mass fraction of 0-9 wt%, and ball mill to obtain fine slurry; (2-5) The fine slurry is allowed to stand to dehydrate and is pressed into shape. It is then sintered at 1180-1280℃ for 1-2 hours to obtain permanent magnet ferrite.

6. The preparation method according to claim 5, characterized in that, The additive in step (2-2) is one or more of silicon dioxide, calcium carbonate, or aluminum oxide; The ball milling fluid in step (2-2) is water, and the particle size of the slurry after ball milling is 0.6 to 1.5 μm.

7. The preparation method according to claim 5, characterized in that, The average particle size of the pre-calcined material after coarse crushing in steps (2-4) is 3-5 μm; The additives in steps (2-4) are strontium carbonate, silicon dioxide, aluminum oxide, calcium carbonate, and boric acid, or a mixture of several of these. The particle size of the fine slurry in steps (2-4) is 0.6 to 1 μm.

8. The preparation method according to claim 5, characterized in that, In steps (2-5), wet pressing is performed with a forming magnetic field strength of 9000-11000 Oe and a pressure of 3-5 MPa. The sintering temperature in steps (2-5) is 1220-1270℃, and the holding time is 1-2h.

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