Permanent magnetic ferrite material based on efficient ball milling process and preparation method thereof

Abstract

The invention discloses a preparation method of a permanent magnetic ferrite material based on an efficient ball milling process, and belongs to the technical field of magnetic materials, the preparation method comprises the following steps: S1, weighing a permanent magnetic ferrite pre-sintering material, an additive and zinc stearate, and mixing and grinding in a wet ball milling manner to obtain uniformly mixed slurry; s2, dehydrating the uniformly mixed slurry to enable the water content of the slurry to be 25wt%-35wt%, and then molding in an oriented magnetic field to obtain a green body; and S3, sintering the green body in a resistance furnace to obtain the permanent magnetic ferrite material. According to the invention, an interface dispersant is added during ball milling of the pre-sintered material, so that agglomerated particles in the slurry during ball milling are rapidly opened, the ball milling efficiency can be rapidly improved, and the granularity of the slurry after ball milling is more uniform and higher in consistency.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic materials, and in particular relates to a permanent magnetic ferrite material based on a high-efficiency ball milling process and a preparation method thereof. Background Art

[0002] Permanent ferrite material is an important magnetic functional material, widely used in automotive motors, household appliances, power tools, and toy design and manufacturing. At present, the country advocates energy conservation, environmental protection, and green development. Permanent ferrite materials are increasingly widely used in emerging fields such as new energy, electric vehicles, smart cities, and smart earth, and the market demand is growing at a rate of about 15% per year. Ferrite permanent magnet materials have the advantages of easy use, high temperature resistance, high resistance, high coercivity, remanence, and magnetic energy product. Compared with rare earth permanent magnet materials and metal permanent magnet materials, sintered ferrite permanent magnet materials have the advantages of low price, large quantity, and easy purchase.

[0003] At present, the permanent ferrite magnets on the market are basically based on the M-type magnetoplumbite structure, supplemented by a small amount of W-type magnetoplumbite structure. In order to improve the performance of M-type ferrite magnets, the main direction is to make the particle size of ferrite grains close to the single-domain particle size and the particle size distribution range narrower, the particle size consistency is higher, the proportion of grains in anisotropic arrangement is higher and the density is high. In order to solve the above problems, in recent years, it has been proposed to add calcium gluconate, calcium lactate, sorbitol and citric acid during the wet ball milling process of permanent ferrite pre-sintering materials, which greatly improves the magnetic properties of permanent ferrite magnets. However, the current fine grinding (wet) process of ferrite pre-sintering materials has a long grinding time, consumes a lot of electricity, and increases production costs. Summary of the invention

[0004] In order to solve the problem that the prior art ferrite pre-sintered material fine grinding (wet grinding) process has a long grinding time, consumes a lot of electricity and increases production costs, the purpose of the present invention is to provide a permanent magnet ferrite material based on an efficient ball milling process and a preparation method thereof.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a permanent magnetic ferrite material based on a high-efficiency ball milling process, comprising the following steps:

[0007] S1: weighing the permanent magnet ferrite pre-sintered material, additives and zinc stearate, mixing and grinding them by wet ball milling to obtain a mixed slurry;

[0008] S2: dehydrating the mixed slurry to make the water content of the slurry 25wt%-35wt%, and then molding it in an oriented magnetic field to obtain a green body;

[0009] The slurry can be dehydrated by centrifugation or filter press. The water content of the slurry has a certain influence on both molding and sintering. If the water content is low, the slurry fluidity is poor, the automatic injection system is difficult to work and the injection consistency is poor, resulting in poor consistency and uneven density of the molded body after molding; if the water content is too high, it will lead to a decrease in molding efficiency, the water content of the molded body after molding fluctuates, and the molded body shrinks violently during the subsequent sintering process, resulting in a decrease in the mechanical strength of the sintered body.

[0010] S3: placing the green body into a resistance furnace for sintering to obtain a permanent magnet ferrite material.

[0011] Furthermore, the permanent magnet ferrite pre-sintered material in S1 is any one of Y30H-1, Y30H-2, Y32, Y33, Y35, Y36, Y38 and Y40.

[0012] Furthermore, the amount of permanent magnet ferrite pre-sintered material added in S1 is 500-1000g.

[0013] Furthermore, the additives in S1 include the following raw materials in weight percentage: 0.33-1.20wt% CaCO3, 0.1-0.65wt% SiO2, 0-1.5wt% Al2O3, 0-0.3wt% H3BO3, 0-0.15wt% NH4HCO3, 0-2wt% La2O3, 0-1wt% Co2O3; the average particle size of the additive powder should be less than or equal to 2μm.

[0014] The addition of CaCO3, SiO2, H3BO3, La2O3 and Co2O3 is to improve the magnetic properties and density of sintered ferrite. The addition of Al2O3 improves the coercive force of the magnet. The addition of NH4HCO3 not only improves the ball milling efficiency, but also inhibits the loss of Sr in the pre-sintered material.

[0015] Furthermore, the added amount of zinc stearate in S1 is 0.1-0.4 wt %.

[0016] Furthermore, in S1, steel balls with a diameter of ∮3.5-∮6.5 mm are used during wet ball milling; the mass ratio of material, ball and water during wet ball milling is (12-15):1:(1.5-2.2); and the wet ball milling time is 12-16 h.

[0017] Furthermore, the average particle size of the mixed slurry after wet ball milling in S1 is 0.7-1.0 μm.

[0018] If the average particle size of the mixed material is small, less than 0.7μm, in the subsequent molding process, it will be difficult to dehydrate the slurry and the fluidity will be too high, making molding difficult. In the sintering process after molding, the temperature adaptation range of the product will be narrowed, and the grains will easily overgrow and produce crystals. If the average particle size of the mixed material is large, greater than 1.0μm, in the subsequent molding process, it will be difficult to orient the slurry in the molding magnetic field and the fluidity will be too low. In the sintering process after molding, large grains will easily overgrow and produce crystals. By precisely controlling the average particle size of the mixed slurry after wet ball milling to be between 0.7-1.0μm, not only the material behavior in the molding process is optimized and the production efficiency is improved, but also the comprehensive performance of the sintered product is significantly improved.

[0019] Furthermore, the forming magnetic field in S2 is 450-950KA / m.

[0020] The external molding magnetic field should be greater than or equal to 450KA / m. If the magnetic field during molding is too low, it will cause insufficient orientation of the slurry particles in the molded body after molding, resulting in a decrease in the magnetic properties of the molded body after sintering.

[0021] Furthermore, the sintering time in S3 is 50-60 minutes, and the sintering temperature is 1100-1300°C.

[0022] In a second aspect, the present invention provides a permanent magnet ferrite material based on a high-efficiency ball milling process, which is made by the preparation method of the permanent magnet ferrite material based on a high-efficiency ball milling process described in any one of the above contents.

[0023] Beneficial effects of the present invention:

[0024] 1. The present invention adds zinc stearate during the wet ball milling process. The dispersant currently used in ball milling has an addition amount that is too low, and if it is less than 0.15wt%, it has almost no effect on improving the ball milling efficiency. If the addition amount is too high, if it is higher than 0.3wt%, the sintered product is prone to cracks, black spots and other undesirable conditions. However, the use of zinc stearate will not have the above conditions. After the addition of zinc stearate, it can act on inorganic solid particles that are difficult to dissolve in liquids, so that the particles are quickly and evenly dispersed, and the particles are prevented from settling and agglomerating. It will be adsorbed on the surface of the solid particles and form an adsorption layer on the surface, so that a double-layer structure is formed on the surface of the solid particles. This structure has a strong affinity with water, and the solid particles will also be separated due to electrostatic repulsion. In this way, during ball milling, the slurry particles will be more evenly dispersed in water, and the particle suspension performance will be increased without rapid precipitation, so that the ball milling efficiency can be fully utilized, and the average particle size of the slurry after ball milling can be smaller under the same ball milling time, and the original ball milling effect can be achieved under the condition of reducing the ball milling time.

[0025] 2. The operation method of the permanent magnet ferrite material of the present invention is simple and does not increase the original permanent magnet ferrite production process, and is suitable for large-scale production. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Example 1

[0028] This embodiment provides a method for preparing a permanent magnetic ferrite material based on a high-efficiency ball milling process, comprising the following steps:

[0029] S1: Weigh 500g of permanent magnet ferrite pre-sintered material Y30H-2, 0.8wt% CaCO3, 0.1wt% H3BO3, 0.3wt% SiO2, 0.1wt% Al2O3, 0.13wt% NH4HCO3 and 0.1wt% zinc stearate, mix and grind by wet ball milling, using a steel ball with a diameter of 5mm during wet ball milling; the mass ratio of material, ball and water during wet ball milling is 12:1:1.8; the wet ball milling time is 14h to obtain a mixed slurry;

[0030] S2: Dehydrating the mixed slurry to make the water content of the slurry 30wt%, and then molding it in an orientation magnetic field with a molding magnetic field of 557KA / m to obtain a green body;

[0031] S3: placing the green body into a resistance furnace for sintering. The sintering time is 60 minutes and the sintering temperature is 1210° C. to obtain a permanent magnet ferrite material.

[0032] Example 2

[0033] This embodiment provides a method for preparing a permanent magnetic ferrite material based on a high-efficiency ball milling process, comprising the following steps:

[0034] S1: Weigh 500g of permanent magnet ferrite pre-sintered material, 0.8wt% CaCO3, 0.1wt% H3BO3, 0.3wt% SiO2, 0.1wt% Al2O3, 0.13wt% NH4HCO3 and 0.2wt% zinc stearate, mix and grind by wet ball milling, using a steel ball with a diameter of 5mm during wet ball milling; the mass ratio of material, ball and water during wet ball milling is 12:1:1.8; the wet ball milling time is 14h to obtain a mixed slurry;

[0035] S2: Dehydrating the mixed slurry to make the water content of the slurry 30wt%, and then molding it in an orientation magnetic field with a molding magnetic field of 557KA / m to obtain a green body;

[0036] S3: placing the green body into a resistance furnace for sintering. The sintering time is 60 minutes and the sintering temperature is 1210° C. to obtain a permanent magnet ferrite material.

[0037] Example 3

[0038] This embodiment provides a method for preparing a permanent magnetic ferrite material based on a high-efficiency ball milling process, comprising the following steps:

[0039] S1: Weigh 500g of permanent magnet ferrite pre-sintered material, 0.8wt% CaCO3, 0.1wt% H3BO3, 0.3wt% SiO2, 0.1wt% Al2O3, 0.13wt% NH4HCO3 and 0.3wt% zinc stearate, mix and grind by wet ball milling, use steel balls with a diameter of 5mm during wet ball milling; the mass ratio of material, ball and water during wet ball milling is 12:1:1.8; the wet ball milling time is 14h to obtain a mixed slurry;

[0040] S2: Dehydrating the mixed slurry to make the water content of the slurry 30wt%, and then molding it in an orientation magnetic field with a molding magnetic field of 557KA / m to obtain a green body;

[0041] S3: placing the green body into a resistance furnace for sintering. The sintering time is 60 minutes and the sintering temperature is 1210° C. to obtain a permanent magnet ferrite material.

[0042] Example 4

[0043] This embodiment provides a method for preparing a permanent magnetic ferrite material based on a high-efficiency ball milling process, comprising the following steps:

[0044] S1: Weigh 500g of permanent magnet ferrite pre-sintered material, 0.8wt% CaCO3, 0.1wt% H3BO3, 0.3wt% SiO2, 0.1wt% Al2O3, 0.13wt% NH4HCO3 and 0.4wt% zinc stearate, mix and grind by wet ball milling, using a steel ball with a diameter of 5mm during wet ball milling; the mass ratio of material, ball and water during wet ball milling is 12:1:1.8; the wet ball milling time is 14h to obtain a mixed slurry;

[0045] S2: Dehydrating the mixed slurry to make the water content of the slurry 30wt%, and then molding it in an orientation magnetic field with a molding magnetic field of 557KA / m to obtain a green body;

[0046] S3: placing the green body into a resistance furnace for sintering. The sintering time is 60 minutes and the sintering temperature is 1210° C. to obtain a permanent magnet ferrite material.

[0047] Example 5

[0048] This embodiment provides a method for preparing a permanent magnetic ferrite material based on a high-efficiency ball milling process, comprising the following steps:

[0049] S1: Weigh 500g of permanent magnet ferrite pre-sintered material, 0.8wt% CaCO3, 0.1wt% H3BO3, 0.3wt% SiO2, 0.1wt% Al2O3, 0.13wt% NH4HCO3 and 0.1wt% zinc stearate, mix and grind by wet ball milling, use steel balls with a diameter of 5mm during wet ball milling; the mass ratio of material, ball and water during wet ball milling is 12:1:1.8; the wet ball milling time is 12h to obtain a mixed slurry;

[0050] S2: Dehydrating the mixed slurry to make the water content of the slurry 30wt%, and then molding it in an orientation magnetic field with a molding magnetic field of 557KA / m to obtain a green body;

[0051] S3: placing the green body into a resistance furnace for sintering. The sintering time is 60 minutes and the sintering temperature is 1210° C. to obtain a permanent magnet ferrite material.

[0052] Example 6

[0053] This embodiment provides a method for preparing a permanent magnetic ferrite material based on a high-efficiency ball milling process, comprising the following steps:

[0054] S1: Weigh 500g of permanent magnet ferrite pre-sintered material, 0.8wt% CaCO3, 0.1wt% H3BO3, 0.3wt% SiO2, 0.1wt% Al2O3, 0.13wt% NH4HCO3 and 0.2wt% zinc stearate, mix and grind by wet ball milling, using a steel ball with a diameter of 5mm during wet ball milling; the mass ratio of material, ball and water during wet ball milling is 12:1:1.8; the wet ball milling time is 12h to obtain a mixed slurry;

[0055] S2: Dehydrating the mixed slurry to make the water content of the slurry 30wt%, and then molding it in an orientation magnetic field with a molding magnetic field of 557KA / m to obtain a green body;

[0056] S3: placing the green body into a resistance furnace for sintering. The sintering time is 60 minutes and the sintering temperature is 1210° C. to obtain a permanent magnet ferrite material.

[0057] Example 7

[0058] This embodiment provides a method for preparing a permanent magnetic ferrite material based on a high-efficiency ball milling process, comprising the following steps:

[0059] S1: Weigh 500g of permanent magnet ferrite pre-sintered material, 0.8wt% CaCO3, 0.1wt% H3BO3, 0.3wt% SiO2, 0.1wt% Al2O3, 0.13wt% NH4HCO3 and 0.3wt% zinc stearate, mix and grind by wet ball milling, use steel balls with a diameter of 5mm during wet ball milling; the mass ratio of material, ball and water during wet ball milling is 12:1:1.8; the wet ball milling time is 12h to obtain a mixed slurry;

[0060] S2: Dehydrating the mixed slurry to make the water content of the slurry 30wt%, and then molding it in an orientation magnetic field with a molding magnetic field of 557KA / m to obtain a green body;

[0061] S3: placing the green body into a resistance furnace for sintering. The sintering time is 60 minutes and the sintering temperature is 1210° C. to obtain a permanent magnet ferrite material.

[0062] Example 8

[0063] This embodiment provides a method for preparing a permanent magnetic ferrite material based on a high-efficiency ball milling process, comprising the following steps:

[0064] S1: Weigh 500g of permanent magnet ferrite pre-sintered material, 0.8wt% CaCO3, 0.1wt% H3BO3, 0.3wt% SiO2, 0.1wt% Al2O3, 0.13wt% NH4HCO3 and 0.4wt% zinc stearate, mix and grind them by wet ball milling, using a steel ball with a diameter of 5mm during wet ball milling; the mass ratio of material, ball and water during wet ball milling is 12:1:1.8; the wet ball milling time is 12h to obtain a mixed slurry;

[0065] S2: Dehydrating the mixed slurry to make the water content of the slurry 30wt%, and then molding it in an orientation magnetic field with a molding magnetic field of 557KA / m to obtain a green body;

[0066] S3: placing the green body into a resistance furnace for sintering. The sintering time is 60 minutes and the sintering temperature is 1210° C. to obtain a permanent magnet ferrite material.

[0067] Comparative Example 1

[0068] Compared with Example 1, this comparative example is different only in that:

[0069] No zinc stearate added.

[0070] Comparative Example 2

[0071] This comparative example is different from Example 5 only in that:

[0072] No zinc stearate added.

[0073] Performance tests were performed on Examples 1 to 8 and Comparative Examples 1 to 2, and the test items were as follows:

[0074] 1. Average particle size detection: The mixed slurry obtained in step S1 of Example 1 to Example 8 and Comparative Example 1 to Comparative Example 2 was screened through a 120-mesh standard sample sieve, and a small amount of the screened slurry (the slurry solid content was greater than 10 g) was dried and dehydrated in an electric drying oven at a temperature range of 100-150°C. The dried slurry was sieved and dispersed through a 200-mesh standard sample sieve, and 5 g of the dispersed slurry powder was taken and the average particle size was tested with a porosity of 0.6. The average particle size test results are shown in Table 1.

[0075] 2. Magnetic property testing: The permanent magnet ferrite materials prepared in Examples 1 to 8 and Comparative Examples 1 to 2 were subjected to magnetic property testing. The test results are shown in Table 2.

[0076] Table 1

[0077] project Average particle size of mixed slurry (μm) Example 1 0.903 Example 2 0.864 Example 3 0.822 Example 4 0.806 Example 5 0.968 Example 6 0.953 Example 7 0.930 Example 8 0.899 Comparative Example 1 0.931 Comparative Example 2 0.930

[0078] As can be seen from Table 1, the average particle size of the mixed slurry of Example 1-Example 4 is smaller than that of Comparative Example 1 and Comparative Example 2, indicating that as the amount of zinc stearate added during ball milling continues to increase, under the same ball milling time, the average particle size of the obtained slurry becomes smaller and smaller. Compared with Example 1-Example 4, Example 5-Example 8 reduces the ball milling time. It can be found that after reducing the ball milling time by 2h, when the amount of zinc stearate added is 0.3wt% (Example 7), the average particle size of the slurry obtained by ball milling is consistent with the average particle size of the slurry in Comparative Example 1 without adding zinc stearate and without reducing the ball milling time, which is 0.930μm. It can be seen that adding zinc stearate during secondary ball milling can effectively reduce the time, and the average particle size of the slurry can meet the requirements of the production process technology in a shorter time.

[0079] Table 2

[0080]

[0081]

[0082] As can be seen from Table 2, the permanent magnet ferrite materials in Examples 1-4 increase the amount of zinc stearate added during ball milling. Under the same ball milling time, Br decreases slightly, Hcb gradually increases, and Hcj first increases and then decreases. Overall, adding zinc stearate during ball milling has no negative impact on the magnetic properties of the raw materials. Compared with Examples 1-4, Example 5-Example 8 reduces the ball milling time. The permanent magnet ferrite materials in Examples 5-Example 8 increase the amount of zinc stearate added during ball milling. Under the same ball milling time, Br decreases slightly, Hcb and Hcj first increase and then decrease. Overall, adding zinc stearate during ball milling has no negative impact on the magnetic properties of the raw materials, and similar effects can be achieved in a shorter ball milling time.

[0083] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0084] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a permanent magnetic ferrite material based on a high-efficiency ball milling process, characterized in that: The following steps are involved: S1: weighing the permanent magnet ferrite pre-sintered material, additives and zinc stearate, mixing and grinding them by wet ball milling to obtain a mixed slurry; S2: dehydrating the mixed slurry to make the water content of the slurry 25wt%-35wt%, and then molding it in an oriented magnetic field to obtain a green body; S3: placing the green body into a resistance furnace for sintering to obtain a permanent magnet ferrite material.

2. The method for preparing a permanent magnetic ferrite material based on a high-efficiency ball milling process according to claim 1, characterized in that: The permanent magnet ferrite pre-sintered material in S1 is any one of Y30H-1, Y30H-2, Y32, Y33, Y35, Y36, Y38 and Y40.

3. The method for preparing a permanent magnetic ferrite material based on a high-efficiency ball milling process according to claim 1, characterized in that: The amount of permanent ferrite pre-sintered material added in S1 is 500-1000g.

4. The method for preparing a permanent magnetic ferrite material based on a high-efficiency ball milling process according to claim 1, characterized in that: The additives in S1 include the following raw materials in weight percentage: 0.33-1.20wt% CaCO3, 0.1-0.65wt% SiO2, 0-1.5wt% Al2O3, 0-0.3wt% H3BO3, 0-0.15wt% NH4HCO3, 0-2wt% La2O3, 0-1wt% Co2O3; the average particle size of the additive powder should be less than or equal to 2μm.

5. The method for preparing a permanent magnetic ferrite material based on a high-efficiency ball milling process according to claim 1, characterized in that: The addition amount of zinc stearate in S1 is 0.1-0.4 wt%.

6. The method for preparing a permanent magnetic ferrite material based on a high-efficiency ball milling process according to claim 1, characterized in that: In S1, steel balls with a diameter of ∮3.5-∮6.5 mm are used for wet ball milling; the mass ratio of material, ball and water is (12-15):1:(1.5-2.2) during wet ball milling; and the wet ball milling time is 12-16 h.

7. The method for preparing a permanent magnetic ferrite material based on a high-efficiency ball milling process according to claim 1, characterized in that: The average particle size of the mixed slurry after wet ball milling in S1 is 0.7-1.0 μm.

8. The method for preparing a permanent magnetic ferrite material based on a high-efficiency ball milling process according to claim 1, characterized in that: The forming magnetic field in S2 is 450-950KA / m.

9. The method for preparing a permanent magnetic ferrite material based on a high-efficiency ball milling process according to claim 1, characterized in that: The sintering time in S3 is 50-60 minutes, and the sintering temperature is 1100-1300°C.

10. A permanent magnet ferrite material based on a high-efficiency ball milling process, made by the preparation method of a permanent magnet ferrite material based on a high-efficiency ball milling process according to any one of claims 1 to 9.

Images