Method for regulating and controlling sintered strontium ferrite material

Abstract

The invention relates to a method for regulating and controlling a sintered strontium ferrite material, which comprises the following steps: firstly, regulating and controlling the type and the ratio of additives according to the D50 particle size of strontium ferrite pre-sintered material powder and the performance requirement of the strontium ferrite material, and carrying out ball milling on the strontium ferrite pre-sintered material powder, the additives and a dispersing agent until the target D50 particle size is reached; mixed slurry is obtained; then, dehydrating the mixed slurry, and sequentially carrying out oriented wet pressing molding and drying to obtain a green body; and then, carrying out sintering treatment on the green body, controlling the heating rate in the sintering treatment until the sintering temperature is reached, carrying out heat preservation, and then cooling to obtain the strontium ferrite material. According to the method provided by the invention, the particle size characteristics of the pre-sintered material powder, the selection of the additive and the control of the ball milling process and the sintering process are combined, and the high-performance sintered strontium ferrite material can be prepared through regulation and control.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic material preparation, and in particular to a method for regulating and controlling sintered strontium ferrite materials. Background Art

[0002] Permanent ferrite magnets belong to the second generation of permanent magnetic materials. They have the characteristics of high resistivity, good temperature stability, strong resistance to environmental changes, etc. In addition, they are rich in raw material sources, low in cost, and suitable for mass production. They are key electronic materials for components such as micro-special motors in the fields of electroacoustic devices, industrial high-power motors, new energy vehicles, intelligent machinery, and unmanned power systems. Although the maximum magnetic energy product of ferrite magnets (strontium ferrite) is only 1 / 10 of the maximum magnetic energy product of rare earth magnets (sintered NdFeB permanent magnets), due to the uneven distribution of rare earth metal resources, the scarcity of certain heavy rare earth metals, the instability of the rare earth supply chain, and the potential negative impact of rare earth mining on the environment, it has become particularly urgent to find and develop more environmentally friendly and low-cost sintered ferrite permanent magnet alternatives, and the demand for high-end strontium ferrite materials will continue to increase.

[0003] At present, the focus of improving the performance of strontium ferrite materials is mainly on two key aspects: optimizing the performance of magnetic powder and enhancing the performance of magnets. Among them, the performance of magnetic powder can be optimized by doping rare earth ions into the raw materials to replace some elements, and adding dispersants to modify the surface of the powder; the performance of magnets can be improved by using appropriate additives and changing the sintering process. During the sintering process, the additives are enriched at the grain boundaries, playing a dual role of fluxing and inhibiting grain growth, which can not only refine the grains and increase the density of the magnet, but also significantly improve the microscopic morphology of the material, which is conducive to increasing the proportion of single-domain particles and improving the rectangularity.

[0004] For example, the existing study "Influence of SiO2 and CaO additions on the microstructure and magnetic properties of sintered Sr-hexaferrite. Journal of the European Ceramic Society, 25 (9), 1681-1688." discloses that adding SiO2 and CaO (or CaCO3) before sintering strontium ferrite can react at low temperature and form a calcium silicate phase. However, if strontium ferrite with excessive SrO is sintered at a eutectic temperature above 1210°C, the liquid phase will react with the calcium silicate formed by CaO and SiO2. The final composition of the liquid phase will determine the grain growth rate of the ferrite, affect the grain size and magnet density, etc., and further affect the magnetic properties. In addition, there are studies showing that the addition of additives can only improve the magnetic properties of a magnet in one aspect, but often causes a decrease in another magnetic property, which has obvious limitations. Moreover, the use of additives, the front-end ball milling process and the back-end sintering process are not analyzed together, which may lead to formulation conflicts when selecting additives. There is a lack of quantitative analysis of the impact of additive content and ratio on magnets, which easily leads to a situation where magnetic powder needs to be repeatedly tested and sintered to produce a magnet that meets the requirements.

[0005] Therefore, it is necessary to develop a preparation process that can monitor the entire process from magnetic powder to magnet, and match the magnetic powder characteristics, additive selection, and ball milling and sintering processes to quickly prepare the magnetic powder into magnets with customized performance, so as to improve production efficiency and reduce production costs. Summary of the invention

[0006] In view of the above problems, the purpose of the present invention is to provide a method for regulating the sintering of strontium ferrite materials. Compared with the prior art, the method provided by the present invention combines the particle size characteristics of the pre-fired powder, the selection of additives, the ball milling process and the control of the sintering process, and can regulate the preparation of high-performance sintered strontium ferrite materials.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for regulating sintered strontium ferrite material, the method comprising the following steps:

[0009] (1) According to the D50 particle size of the strontium ferrite pre-sintered powder and the performance requirements of the strontium ferrite material, the type and ratio of the additives are adjusted, and the strontium ferrite pre-sintered powder, the additives and the dispersant are ball-milled until the target D50 particle size is reached to obtain a mixed slurry;

[0010] (2) dehydrating the mixed slurry obtained in step (2), and then sequentially performing orientation wet pressing and drying to obtain a green body;

[0011] (3) sintering the green body obtained in step (2), wherein the heating rate is controlled to reach the sintering temperature and the temperature is maintained, and then cooled to obtain a strontium ferrite material.

[0012] In the present invention, the type and ratio of additives are controlled according to the characteristics of the D50 particle size of the strontium ferrite pre-sintered powder, and the ball milling and sintering processes are regulated. The magnetic properties of ferrite materials are closely related to the particle size of their slurry. The present invention can improve the dispersibility of the slurry and appropriately reduce the particle size of the magnetic powder, and can achieve a higher degree of grain orientation. In addition, by controlling the type of additives and adjusting the sintering process, the orientation and density of the ferrite material can be further improved, and by controlling the type of additives, different ferrite materials with specific performance requirements can be prepared based on a magnetic powder pre-sintered powder to meet the needs of different application scenarios.

[0013] Preferably, the additives in step (1) include silicon dioxide and calcium carbonate.

[0014] Preferably, the additive further comprises bismuth oxide and / or aluminum oxide.

[0015] In the present invention, the additive silicon dioxide is generally nanometer-grade, calcium carbonate, bismuth oxide, aluminum oxide, etc. are generally micrometer-grade, and all are industrially pure, wherein the particle size of the micrometer-grade additive generally satisfies D50=0.5-2.5μm, and D90 / D10<5.

[0016] Preferably, when the D50 particle size of the strontium ferrite pre-sintered powder is less than 1 μm, the mass of silicon dioxide accounts for 0.5-0.6% of the mass of the strontium ferrite pre-sintered powder, for example, it can be 0.5%, 0.52%, 0.54%, 0.56%, 0.58% or 0.6%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] Preferably, when the D50 particle size of the strontium ferrite pre-sintered powder is 1-3 μm, the mass of silicon dioxide accounts for 0.4-0.5% of the mass of the strontium ferrite pre-sintered powder, for example, it can be 0.4%, 0.42%, 0.44%, 0.46%, 0.48% or 0.5%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] Preferably, when the D50 particle size of the strontium ferrite pre-sintered powder is greater than 3 μm, the mass of silicon dioxide accounts for 0.2-0.4% of the mass of the strontium ferrite pre-sintered powder, for example, it can be 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3%, 0.32%, 0.34%, 0.36%, 0.38% or 0.4%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] In the present invention, the amount of silicon dioxide added in the additive is regulated according to the D50 particle size of the strontium ferrite pre-sintered powder. The present invention preferably adopts the corresponding mode of the above-mentioned D50 particle size range and the mass percentage of silicon dioxide, because in the sintering process, the silicate liquid phase with silicon dioxide as the network former is the main factor for regulating the sintering, and its content is too high or too low, which will affect the structure and performance of the sintered body. When it is too high, it is easy to cause the abnormal growth of the grains and then cause the coercive force to decrease. When it is too low, it is easy to cause incomplete sintering and insufficient density of the sintered body. Therefore, the present invention regulates the addition of silicon dioxide according to the D50 particle size range. Different D50 particle size ranges reflect the specific surface area of ​​the pre-sintered powder. The larger the particle size, the smaller the specific surface area, the less silicate liquid phase is required, and the content of silicon dioxide in the formula is also less. Therefore, the present invention can accurately predict and regulate the amount of silicon dioxide, so as to meet the performance requirements of the strontium ferrite material.

[0020] Preferably, the strontium ferrite pre-sintered powder in step (1) is pure M-phase strontium ferrite.

[0021] Preferably, the chemical formula of the strontium ferrite pre-sintered powder is SrFe x O 19 , wherein the value of X is 11-12, for example, 11, 11.2, 11.4, 11.6, 11.8 or 12, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0022] Preferably, the dispersant comprises calcium gluconate and / or sodium carboxymethylcellulose.

[0023] Preferably, the mass of the dispersant accounts for 0.3-0.5% of the mass of the strontium ferrite pre-sintered powder, for example, it can be 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.40%, 0.42%, 0.44%, 0.46%, 0.48% or 0.5%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] Preferably, a solvent is also added during the ball milling.

[0025] Preferably, the solvent comprises water.

[0026] Preferably, the solid-to-liquid ratio of the mixed slurry in the ball mill is 1:(1.5-2.5), for example, it can be 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4 or 1:2.5, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] Preferably, the grinding balls used in the ball milling include stainless steel balls.

[0028] Preferably, the diameter of the grinding balls used in the ball mill is 2-5 mm, for example, 2 mm, 3 mm, 4 mm or 5 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] Preferably, the mass ratio of the strontium ferrite pre-sintered powder to the grinding balls in the ball mill is 1:(10-20), for example, it can be 1:10, 1:12, 1:14, 1:16, 1:18 or 1:20, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] Preferably, the mass percentage of water in the mixed slurry during dehydration in step (2) is 30-50%, for example, it can be 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48% or 50%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] Preferably, the pressure of the oriented wet pressing molding is 4.5-6.5 MPa, for example, it can be 4.5 MPa, 4.6 MPa, 4.8 MPa, 5 MPa, 5.2 MPa, 5.4 MPa, 5.6 MPa, 5.8 MPa, 6 MPa, 6.2 MPa, 6.4 MPa or 6.5 MPa, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] Preferably, the holding time of the oriented wet pressing molding is 30-60s, for example, it can be 30s, 35s, 40s, 45s, 50s, 55s or 60s, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] Preferably, the maximum oriented magnetic induction intensity of the oriented wet pressing molding is 0.5-1.5T, for example, it can be 0.5T, 0.6T, 0.8T, 1T, 1.2T, 1.4T or 1.5T, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] Preferably, the drying temperature is 60-90°C, for example, it can be 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, 82°C, 84°C, 86°C, 88 or 90°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] Preferably, the drying time is 2-4 h, for example, it can be 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3 h, 3.2 h, 3.4 h, 3.6 h, 3.8 h or 4 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] Preferably, the sintering temperature in step (3) is 1150-1250°C, for example, it can be 1150°C, 1160°C, 1170°C, 1180°C, 1190°C, 1200°C, 1210°C, 1220°C, 1230°C, 1240°C or 1250°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] Preferably, the insulation time is 10-60 min, for example, 10 min, 20 min, 30 min, 40 min, 50 min or 60 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] Preferably, the heating process includes: first heating to 800° C. at a first heating rate, and then heating to the sintering temperature at a second heating rate.

[0039] Preferably, the first heating rate is ≤5°C / min, for example, it can be 5°C / min, 4°C / min, 3°C / min, 2°C / min or 1°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] Preferably, the second heating rate is ≤10°C / min, for example, it can be 10°C / min, 8°C / min, 6°C / min, 5°C / min, 4°C / min, 3°C / min, 2°C / min or 1°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] Preferably, the strontium ferrite material is divided into a first ferrite material, a second ferrite material, a third ferrite material and a fourth ferrite material according to remanence and coercive force.

[0042] Preferably, the properties of the first ferrite material meet the following requirements: the remanence Br is 4150-4250Gs, for example, it can be 4150Gs, 4160Gs, 4170Gs, 4180Gs, 4190Gs, 4200Gs, 4210Gs, 4220Gs, 4230Gs, 4240Gs or 4250Gs, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable; the coercive force Hcj is 3400-3700Oe, for example, The magnetic energy product BH is 4.1-4.3 MGOe, for example, 4.1 MGOe, 4.2 MGOe or 4.3 MGOe, but is not limited to the listed values. The magnetic energy product BH is 4.1-4.3 MGOe, for example, 4.1 MGOe, 4.2 MGOe or 4.3 MGOe, but is not limited to the listed values. The magnetic energy product BH is 5.0 g / cm2 or more. 3 , for example, it can be 5.0 g / cm 3 , 5.1g / cm 3 , 5.2g / cm 3 , 5.3g / cm 3 , 5.4g / cm 3 or 5.5g / cm 3 , but not limited to the listed values, other unlisted values ​​within the numerical range are also applicable.

[0043] Preferably, the performance of the second ferrite material satisfies: the remanence Br is 4050-4150Gs, for example, it can be 4050Gs, 4060Gs, 4070Gs, 4080Gs, 4090Gs, 4100Gs, 4110Gs, 4120Gs, 4130Gs, 4140Gs or 4150Gs, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable; the coercive force Hcj is 4200-4400 Oe, for example, it can be 4200Oe, 4250Oe, 4300Oe, 4350Oe or 4400Oe, but not limited to the listed values, and other values ​​not listed in the numerical range are also applicable; the maximum magnetic energy product BH is 4.0-4.2MGOe, for example, it can be 4.0MGOe, 4.1MGOe or 4.2MGOe, but not limited to the listed values, and other values ​​not listed in the numerical range are also applicable; the volume density is ≥4.95g / cm 3 , for example, it can be 4.95g / cm 3 , 4.96g / cm 3 , 4.97g / cm 3 , 4.98g / cm 3 , 4.99g / cm 3or 5.00g / cm 3 , but not limited to the listed values, other unlisted values ​​within the numerical range are also applicable.

[0044] Preferably, the properties of the third ferrite material meet the following requirements: the remanence Br is 4000-4100Gs, for example, it can be 4000Gs, 4010Gs, 4020Gs, 4030Gs, 4040Gs, 4050Gs, 4060Gs, 4070Gs, 4080Gs, 4090Gs or 4100Gs, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable; the coercive force Hcj is 4300-4500Oe, for example, it can be 43 00Oe, 4350Oe, 4400Oe, 4450Oe or 4500Oe, but not limited to the listed values, other values ​​not listed in the numerical range are also applicable; the maximum magnetic energy product BH is 3.9-4.1MGOe, for example, it can be 3.90MGOe, 3.95MGOe, 4.00MGOe, 4.05MGOe or 4.10MGOe, but not limited to the listed values, other values ​​not listed in the numerical range are also applicable; the volume density is ≥4.90g / cm 3 , for example, it can be 4.90g / cm 3 , 4.95g / cm 3 , 4.96g / cm 3 , 4.97g / cm 3 , 4.98g / cm 3 , 4.99g / cm 3 or 5.00g / cm 3 , but not limited to the listed values, other unlisted values ​​within the numerical range are also applicable.

[0045] Preferably, the performance of the fourth ferrite material satisfies: the remanence Br is 3850-3950Gs, for example, it can be 3850Gs, 3860Gs, 3870Gs, 3880Gs, 3890Gs, 3900Gs, 3910Gs, 3920Gs, 3930Gs, 3940Gs or 3950Gs, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable; the coercive force Hcj is 4600-4700Oe, for example For example, it can be 4600Oe, 4620Oe, 4640Oe, 4680Oe or 4700Oe, but it is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable; the maximum magnetic energy product BH is 3.7-4.0MGOe, for example, it can be 3.7MGOe, 3.8MGOe, 3.9MGOe or 4.0MGOe, but it is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable; the volume density is ≥4.88g / cm 3, for example, it can be 4.88 g / cm 3 , 4.90g / cm 3 , 4.95g / cm 3 , 4.96g / cm 3 , 4.97g / cm 3 , 4.98g / cm 3 , 4.99g / cm 3 or 5.00g / cm 3 , but not limited to the listed values, other unlisted values ​​within the numerical range are also applicable.

[0046] In the present invention, according to the classification of remanence and coercive force, the first ferrite material generally represents a high remanence magnet, the second ferrite material generally represents a high remanence and high coercive force magnet, the third ferrite material generally represents a high coercive force magnet, and the fourth ferrite material generally represents an ultra-high coercive force magnet, and the remanence and coercive force ranges corresponding to each magnet are as described above.

[0047] Preferably, when the strontium ferrite material is the first ferrite material, the D50 particle size of the strontium ferrite pre-sintered powder is ≥2μm, for example, it can be 2μm, 3μm, 4μm, 5μm or 6μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0048] Preferably, when the strontium ferrite material is the first ferrite material, the molar ratio of calcium carbonate and silicon dioxide in the additive is (1.8-2.5):1, for example, it can be 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1 or 2.5:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] Preferably, when the strontium ferrite material is the first ferrite material, the mass percentage of bismuth oxide in the additive to the mass of the strontium ferrite pre-sintered powder is ≤1%, for example, it can be 1%, 0.9%, 0.8%, 0.6% or 0.5%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] Preferably, when the strontium ferrite material is the first ferrite material, the ball milling speed is 50-100rpm, for example, it can be 50rpm, 60rpm, 70rpm, 80rpm, 90rpm or 100rpm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0051] Preferably, when the strontium ferrite material is the first ferrite material, the ball milling time is 8-20 hours, for example, it can be 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours or 20 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0052] Preferably, when the strontium ferrite material is the first ferrite material, the ball milling to the target D50 particle size is 0.7-0.9 μm, for example, it can be 0.7 μm, 0.75 μm, 0.8 μm, 0.85 μm or 0.9 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0053] Preferably, when the strontium ferrite material is the first ferrite material, the sintering temperature is 1200-1250°C, for example, it can be 1200°C, 1210°C, 1220°C, 1230°C, 1240°C or 1250°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0054] Preferably, when the strontium ferrite material is the second ferrite material, the D50 particle size of the strontium ferrite pre-sintered powder is 1-3 μm, for example, it can be 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm or 3 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0055] Preferably, when the strontium ferrite material is the second ferrite material, the molar ratio of calcium carbonate and silicon dioxide in the additive is (1.5-1.8):1, for example, it can be 1.5:1, 1.6:1, 1.7:1 or 1.8:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0056] Preferably, when the strontium ferrite material is the second ferrite material, the ball mill rotation speed is 50-150rpm, for example, it can be 50rpm, 60rpm, 70rpm, 80rpm, 90rpm, 100rpm, 110rpm, 120rpm, 130rpm, 140rpm or 150rpm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0057] Preferably, when the strontium ferrite material is the second ferrite material, the ball milling time is 12-24 hours, for example, it can be 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0058] Preferably, when the strontium ferrite material is the second ferrite material, the ball milling to the target D50 particle size is 0.65-0.9 μm, for example, it can be 0.65 μm, 0.70 μm, 0.75 μm, 0.80 μm, 0.85 μm or 0.90 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0059] Preferably, when the strontium ferrite material is the second ferrite material, the sintering temperature is 1180-1220°C, for example, it can be 1180°C, 1190°C, 1200°C, 1210°C or 1220°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0060] Preferably, when the strontium ferrite material is the third ferrite material, the D50 particle size of the strontium ferrite pre-sintered powder is 1-3 μm, for example, it can be 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm or 3 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0061] Preferably, when the strontium ferrite material is the third ferrite material, the molar ratio of calcium carbonate and silicon dioxide in the additive is (1.2-1.5):1, for example, it can be 1.2:1, 1.3:1, 1.4:1 or 1.5:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0062] Preferably, when the strontium ferrite material is the third ferrite material, the ball mill rotation speed is 100-200rpm, for example, it can be 100rpm, 110rpm, 120rpm, 130rpm, 140rpm, 150rpm, 160rpm, 170rpm, 180rpm, 190rpm or 200rpm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0063] Preferably, when the strontium ferrite material is the third ferrite material, the ball milling time is 16-36 hours, for example, it can be 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours or 36 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0064] Preferably, when the strontium ferrite material is the third ferrite material, the ball milling to the target D50 particle size is 0.6-0.8 μm, for example, it can be 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm or 0.8 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0065] Preferably, when the strontium ferrite material is the third ferrite material, the sintering temperature is 1150-1200°C, for example, it can be 1150°C, 1160°C, 1170°C, 1180°C, 1190°C or 1200°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0066] Preferably, when the strontium ferrite material is the fourth ferrite material, the D50 particle size of the strontium ferrite pre-sintered powder is ≤3μm, for example, it can be 3μm, 2.8μm, 2.6μm, 2.4μm, 2.2μm, 2μm, 1.8μm, 1.6μm, 1.4μm, 1.2μm or 1μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0067] Preferably, when the strontium ferrite material is the fourth ferrite material, the molar ratio of calcium carbonate and silicon dioxide in the additive is (1.2-1.5):1, for example, it can be 1.2:1, 1.3:1, 1.4:1 or 1.5:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0068] Preferably, when the strontium ferrite material is the fourth ferrite material, the mass percentage of the aluminum oxide in the additive to the mass of the strontium ferrite pre-sintered powder is ≤1.5%, for example, it can be 1.5%, 1.4%, 1.3%, 1.2%, 1.1% or 1%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0069] Preferably, when the strontium ferrite material is the fourth ferrite material, the ball mill rotation speed is 100-200rpm, for example, it can be 100rpm, 110rpm, 120rpm, 130rpm, 140rpm, 150rpm, 160rpm, 170rpm, 180rpm, 190rpm or 200rpm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0070] Preferably, when the strontium ferrite material is the fourth ferrite material, the ball milling time is 16-36 hours, for example, it can be 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours or 36 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0071] Preferably, when the strontium ferrite material is the fourth ferrite material, the ball milling to the target D50 particle size is 0.6-0.8 μm, for example, it can be 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm or 0.8 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0072] Preferably, when the strontium ferrite material is the fourth ferrite material, the sintering temperature is 1150-1200°C, for example, it can be 1150°C, 1160°C, 1170°C, 1180°C, 1190°C or 1200°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0073] In the present invention, according to the performance requirements of the strontium ferrite material, that is, the performance requirements of the first ferrite material, the second ferrite material, the third ferrite material and the fourth ferrite material are prepared respectively, the above scheme is preferably used to regulate the molar ratio of calcium carbonate and silicon dioxide and whether bismuth oxide, aluminum oxide, etc. are added. This is because the molar ratio of calcium carbonate and silicon dioxide in the additive affects the composition of the silicate formed during the sintering process, and the silicate liquid phase of different compositions has different viscosities at high temperatures, and also has different effects on the growth orientation of the grains. Therefore, the present invention can further regulate the viscosity of the silicate liquid phase and affect the grain growth by regulating the molar ratio of calcium carbonate and silicon dioxide, thereby meeting the performance requirements of the strontium ferrite material. In addition, bismuth oxide and aluminum oxide can change the performance of ferrite by high-temperature doping, thereby further preparing a strontium ferrite material with the required performance requirements.

[0074] In the present invention, the rotation speed and time of ball milling are regulated according to the performance requirements of the strontium ferrite material, and then the ball milling is preferably controlled to the end point of the D50 particle size. The first to fourth ferrite materials correspond to different target D50 particle size ranges, because the sintering activity of powders with different particle sizes is different, and the sintering activity of samples with smaller particle sizes is larger. It is easier to obtain a dense sintered body under the same sintering conditions, and the orientation of the grain size after sintering directly determines the magnet performance. Smaller grain size will lead to greater coercive force, and samples with better grain orientation consistency have better remanence. Therefore, the present invention can further regulate the performance of the strontium ferrite material by controlling the D50 particle size after ball milling. In addition, the present invention takes a small amount of slurry and dries it before the end of ball milling to test whether the size of the powder after ball milling meets the target requirements. If the requirements are met, the material is discharged, otherwise the ball milling continues.

[0075] In the present invention, the heating rate and sintering temperature of sintering are regulated according to the performance requirements of strontium ferrite materials and the additive formula. The first to fourth ferrite materials correspond to different sintering temperature ranges respectively. This is because different ferrite materials use different additive formulas, and different additive formulas form different silicate liquid phase compositions at high temperatures, resulting in different viscosities and different grain growth processes during sintering, and different degrees of sintering promotion. Specifically, different sintering densities and differences in grain size and orientation inside the sintered body can be caused at the same sintering temperature. Therefore, the present invention preferably sets different sintering temperature ranges for different additive formulas, which can be regulated to achieve the required sintering density, grain size and orientation, and thus achieve the required magnetic properties.

[0076] In the present invention, the heating rate is controlled within a specific range because in the later stage of magnet sintering, the heating rate has a significant effect on the mass transfer and growth mode of the grains. A faster heating rate helps to avoid abnormal grain growth, and is suitable for obtaining magnets with smaller grain size and higher density at higher temperatures. A slower heating rate is conducive to the fusion growth between grains, and is suitable for obtaining magnets with larger grain size and higher density at lower temperatures. Therefore, the present invention can further regulate the performance of ferrite materials by preferably controlling the heating rate range.

[0077] Compared with the prior art, the present invention has the following beneficial effects:

[0078] (1) The method provided by the present invention can adapt the characteristics of magnetic powder, the selection of additives, ball milling and sintering processes, can achieve quantitative control of magnet performance, and can quickly produce customized magnets that meet specific performance requirements, avoiding the need for repeated testing of additives and sintering processes when using a single magnetic powder, thereby significantly improving production efficiency and reducing production costs.

[0079] (2) The method provided by the present invention can prepare a first ferrite material with high remanence, a second material with high remanence and high coercivity, a third ferrite material with high coercivity, and a fourth ferrite material with ultra-high coercivity, thereby meeting the use requirements in different fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 This is a flow chart of the method described in Example 1 of the present invention;

[0081] Figure 2 This is a demagnetization curve diagram of the strontium ferrite material described in Example 1 of the present invention;

[0082] Figure 3 This is a demagnetization curve diagram of the strontium ferrite material described in Example 2 of the present invention;

[0083] Figure 4 This is a demagnetization curve diagram of the strontium ferrite material described in Example 3 of the present invention;

[0084] Figure 5 This is a demagnetization curve diagram of the strontium ferrite material described in Example 4 of the present invention;

[0085] Figure 6 This is a demagnetization curve diagram of the strontium ferrite material described in Example 5 of the present invention;

[0086] Figure 7 This is a demagnetization curve diagram of the strontium ferrite material described in Example 6 of the present invention. DETAILED DESCRIPTION

[0087] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0088] In the following examples, the D50 particle size of the strontium ferrite pre-sintered powder was tested using the SYMPATEC GmbH HELOS & RODOS dry method;

[0089] The particle size distribution of the oxide powders in the following examples was tested using ISO 24235-2007 "Determination of particle size distribution of ceramic powders by laser diffraction method for fine ceramics (advanced ceramics, advanced industrial ceramics)".

[0090] Example 1

[0091] This embodiment provides a method for controlling the sintering of strontium ferrite materials, such as Figure 1 As shown, the method comprises the following steps:

[0092] (1) Select strontium ferrite pre-sintered powder, which is specifically pure M-phase strontium ferrite with a chemical formula of SrFe x O 19, wherein the value of X is 12, the D50 particle size is 2.5-3.0 μm, according to the D50 particle size of the strontium ferrite pre-sintered material powder and the performance requirements of the strontium ferrite material (taking the first ferrite material as the target product), the additives are set to be calcium carbonate and silicon dioxide, the mass of silicon dioxide accounts for 0.5% of the mass of the strontium ferrite pre-sintered material powder, and the molar ratio of calcium carbonate to silicon dioxide is 2:1, and the strontium ferrite pre-sintered material powder, additives and dispersant are added The mixture was put into a ball mill, wherein the pre-sintered material was 500 g, the dispersant (calcium gluconate) was 2.5 g, a 5 mm stainless steel grinding ball was used and the mass was 8 kg, and 1.02 kg of ball milling solvent water was added. The solid-liquid ratio of the mixed slurry in the ball mill was 1:2, the mass ratio of the strontium ferrite pre-sintered material powder and the grinding ball was 1:16, the ball milling speed was 100 rpm, the time was 18 h, and the ball milling was performed until the target D50 particle size was 0.85 μm to obtain a mixed slurry;

[0093] (2) dehydrating the mixed slurry obtained in step (2) until the mass percentage of water in the mixed slurry is 35%, and then loading it into a cylindrical mold with a diameter of 25 mm for orientation wet pressing, the molding pressure is 6.0 MPa, the holding time is 30 s, the maximum orientation magnetic induction intensity is 1.5 T, and then drying at 60° C. for 4 h to obtain a green body;

[0094] (3) The green body obtained in step (2) is sintered, wherein the temperature is first increased to 800° C. at a heating rate of 5° C. / min, then increased to 1210° C. at a heating rate of 5° C. / min and kept at this temperature for 30 min, and then cooled to obtain a strontium ferrite material.

[0095] Example 2

[0096] This embodiment provides a method for controlling a sintered strontium ferrite material, the method comprising the following steps:

[0097] (1) Select strontium ferrite pre-sintered powder, which is specifically pure M-phase strontium ferrite with a chemical formula of SrFe x O 19, wherein the value of X is 11.6, the D50 particle size is 2.0-2.5 μm, according to the D50 particle size of the strontium ferrite pre-sintered powder and the performance requirements of the strontium ferrite material (taking the second ferrite material as the target product), the additives are set to be calcium carbonate and silicon dioxide, the mass of silicon dioxide accounts for 0.45% of the mass of the strontium ferrite pre-sintered powder, and the molar ratio of calcium carbonate to silicon dioxide is 1.8:1, and the strontium ferrite pre-sintered powder, additives and dispersion are mixed. The agent is added into a ball mill, wherein the pre-sintered material is 500g, the dispersant (calcium gluconate) is 2.5g, 3mm stainless steel grinding balls are used and the mass is 8kg, and 0.81kg of ball milling solvent water is also added. The solid-liquid ratio of the mixed slurry in the ball mill is 1:1.6, the mass ratio of the strontium ferrite pre-sintered material powder and the grinding ball is 1:16, the ball milling speed is 80rpm, the time is 16h, and the ball milling is performed until the target D50 particle size is 0.75μm to obtain a mixed slurry;

[0098] (2) dehydrating the mixed slurry obtained in step (2) until the mass percentage of water in the mixed slurry is 40%, and then loading it into a cylindrical mold with a diameter of 25 mm for orientation wet pressing, the molding pressure is 5.5 MPa, the holding time is 30 s, the maximum orientation magnetic induction intensity is 1.0 T, and then drying at 60° C. for 4 h to obtain a green body;

[0099] (3) The green body obtained in step (2) is sintered, wherein the temperature is first increased to 800° C. at a heating rate of 5° C. / min, then increased to 1180° C. at a heating rate of 5° C. / min and kept at this temperature for 30 min, and then cooled to obtain a strontium ferrite material.

[0100] Example 3

[0101] This embodiment provides a method for controlling a sintered strontium ferrite material, the method comprising the following steps:

[0102] (1) Select strontium ferrite pre-sintered powder, which is specifically pure M-phase strontium ferrite with a chemical formula of SrFe x O 19, wherein the value of X is 12, the D50 particle size is 2.5-3.0 μm, and according to the D50 particle size of the strontium ferrite pre-sintered powder and the performance requirements of the strontium ferrite material (taking the first ferrite material as the target product), the additives are set to be calcium carbonate, silicon dioxide and bismuth oxide, the mass of silicon dioxide accounts for 0.5% of the mass of the strontium ferrite pre-sintered powder, the molar ratio of calcium carbonate to silicon dioxide is 2:1, the mass of bismuth oxide accounts for 0.5% of the mass of the strontium ferrite pre-sintered powder, and the strontium ferrite is added to the strontium ferrite. The pre-sintered material powder, additives and dispersant are added into a ball mill, wherein the pre-sintered material is 500 g, the dispersant (sodium carboxymethyl cellulose) is 2.5 g, 5 mm stainless steel grinding balls are used with a mass of 6 kg, 1 kg of ball milling solvent water is also added, the solid-liquid ratio of the mixed slurry in the ball mill is 1:1.9, the mass ratio of the strontium ferrite pre-sintered material powder and the grinding balls is 1:12, the ball milling speed is 100 rpm, the time is 18 h, and the ball milling is performed until the target D50 particle size is 0.85 μm to obtain a mixed slurry;

[0103] (2) dehydrating the mixed slurry obtained in step (2) until the mass percentage of water in the mixed slurry is 35%, and then loading it into a cylindrical mold with a diameter of 25 mm for orientation wet pressing, the molding pressure is 6.0 MPa, the holding time is 30 s, the maximum orientation magnetic induction intensity is 1.5 T, and then drying at 60° C. for 4 h to obtain a green body;

[0104] (3) The green body obtained in step (2) is sintered, wherein the temperature is first increased to 800° C. at a heating rate of 5° C. / min, then increased to 1220° C. at a heating rate of 5° C. / min and kept at this temperature for 30 min, and then cooled to obtain a strontium ferrite material.

[0105] Example 4

[0106] This embodiment provides a method for controlling a sintered strontium ferrite material, the method comprising the following steps:

[0107] (1) Select strontium ferrite pre-sintered powder, which is specifically pure M-phase strontium ferrite with a chemical formula of SrFe x O 19, wherein the value of X is 11.8, the D50 particle size is 2.0-2.5 μm, according to the D50 particle size of the strontium ferrite pre-sintered powder and the performance requirements of the strontium ferrite material (taking the second ferrite material as the target product), the additives are set to be calcium carbonate and silicon dioxide, the mass of silicon dioxide accounts for 0.45% of the mass of the strontium ferrite pre-sintered powder, and the molar ratio of calcium carbonate to silicon dioxide is 1.5:1, and the strontium ferrite pre-sintered powder, additives and dispersion are mixed. The agent is added into a ball mill, wherein the pre-sintered material is 500g, the dispersant (calcium gluconate) is 2g, 3mm stainless steel grinding balls are used and the mass is 10kg, and 0.76kg of ball milling solvent water is also added. The solid-liquid ratio of the mixed slurry in the ball mill is 1:1.5, the mass ratio of the strontium ferrite pre-sintered material powder and the grinding ball is 1:20, the ball milling speed is 80rpm, the time is 20h, and the ball milling is performed until the target D50 particle size is 0.72μm to obtain a mixed slurry;

[0108] (2) dehydrating the mixed slurry obtained in step (2) until the mass percentage of water in the mixed slurry is 40%, and then loading it into a cylindrical mold with a diameter of 25 mm for orientation wet pressing, the molding pressure is 5.5 MPa, the holding time is 30 s, the maximum orientation magnetic induction intensity is 1.0 T, and then drying at 60° C. for 4 h to obtain a green body;

[0109] (3) The green body obtained in step (2) is sintered, wherein the temperature is first increased to 800° C. at a heating rate of 5° C. / min, then increased to 1190° C. at a heating rate of 5° C. / min and kept at this temperature for 60 min, and then cooled to obtain a strontium ferrite material.

[0110] Example 5

[0111] This embodiment provides a method for controlling a sintered strontium ferrite material, the method comprising the following steps:

[0112] (1) Select strontium ferrite pre-sintered powder, which is specifically pure M-phase strontium ferrite with a chemical formula of SrFe x O 19, wherein the value of X is 11.8, the D50 particle size is 2.0-2.5 μm, and according to the D50 particle size of the strontium ferrite pre-sintered powder and the performance requirements of the strontium ferrite material (taking the fourth ferrite material as the target product), the additives are set to be calcium carbonate, silicon dioxide and aluminum oxide, the mass of silicon dioxide accounts for 0.4% of the mass of the strontium ferrite pre-sintered powder, the molar ratio of calcium carbonate to silicon dioxide is 1.5:1, the mass of aluminum oxide accounts for 0.65% of the mass of the strontium ferrite pre-sintered powder, and the strontium ferrite is added to the strontium ferrite. Strontium ferrite pre-sintered material powder, additives and dispersants are added into a ball mill, wherein the pre-sintered material is 500 g, the dispersant (sodium carboxymethyl cellulose) is 2.5 g, 2 mm stainless steel grinding balls are used with a mass of 8 kg, 1.27 kg of ball milling solvent water is also added, the solid-liquid ratio of the mixed slurry in the ball mill is 1:2.5, the mass ratio of the strontium ferrite pre-sintered material powder and the grinding balls is 1:16, the ball milling speed is 100 rpm, the time is 20 h, and the ball milling is performed until the target D50 particle size is 0.72 μm to obtain a mixed slurry;

[0113] (2) dehydrating the mixed slurry obtained in step (2) until the mass percentage of water in the mixed slurry is 40%, and then loading it into a cylindrical mold with a diameter of 25 mm for orientation wet pressing, the molding pressure is 5.5 MPa, the holding time is 30 s, the maximum orientation magnetic induction intensity is 1.0 T, and then drying at 60° C. for 4 h to obtain a green body;

[0114] (3) The green body obtained in step (2) is sintered, wherein the temperature is first increased to 800° C. at a heating rate of 5° C. / min, then increased to 1200° C. at a heating rate of 10° C. / min and kept at this temperature for 30 minutes, and then cooled to obtain a strontium ferrite material.

[0115] Example 6

[0116] This embodiment provides a method for controlling a sintered strontium ferrite material, the method comprising the following steps:

[0117] (1) Select strontium ferrite pre-sintered powder, which is specifically pure M-phase strontium ferrite with a chemical formula of SrFe x O 19, wherein the value of X is 11.8, the D50 particle size is 2.0-2.5 μm, according to the D50 particle size of the strontium ferrite pre-sintered powder and the performance requirements of the strontium ferrite material (taking the third ferrite material as the target product), the additives are set to be calcium carbonate and silicon dioxide, the mass of silicon dioxide accounts for 0.4% of the mass of the strontium ferrite pre-sintered powder, and the molar ratio of calcium carbonate to silicon dioxide is 1.5:1, and the strontium ferrite pre-sintered powder, additives and dispersant are added The mixture was put into a ball mill, wherein the pre-sintered material was 500 g, the dispersant (calcium gluconate) was 2.5 g, a 2 mm stainless steel grinding ball was used and the mass was 10 kg, and 0.81 kg of ball milling solvent water was added. The solid-liquid ratio of the mixed slurry in the ball mill was 1:1.6, the mass ratio of the strontium ferrite pre-sintered material powder and the grinding ball was 1:20, the ball milling speed was 150 rpm, the time was 20 h, and the ball milling was performed until the target D50 particle size was 0.65 μm to obtain a mixed slurry;

[0118] (2) dehydrating the mixed slurry obtained in step (2) until the mass percentage of water in the mixed slurry is 30%, and then loading it into a cylindrical mold with a diameter of 25 mm for orientation wet pressing, the molding pressure is 6.5 MPa, the holding time is 60 s, the maximum orientation magnetic induction intensity is 1.0 T, and then drying at 60° C. for 4 h to obtain a green body;

[0119] (3) The green body obtained in step (2) is sintered, wherein the temperature is first increased to 800° C. at a heating rate of 5° C. / min, then increased to 1200° C. at a heating rate of 10° C. / min and kept at this temperature for 30 minutes, and then cooled to obtain a strontium ferrite material.

[0120] Example 7

[0121] This embodiment provides a method for regulating the sintering of strontium ferrite material. The only difference compared with Example 1 is that the D50 particle size of the strontium ferrite pre-sintered powder in preparing the first ferrite material is 3-3.5 μm, and the mass of silicon dioxide accounts for 0.4% of the mass of the strontium ferrite pre-sintered powder.

[0122] Example 8

[0123] This embodiment provides a method for regulating the sintering of strontium ferrite material. The only difference compared with Example 1 is that the D50 particle size of the strontium ferrite pre-sintered powder in preparing the first ferrite material is 3.5-4μm, and the mass of silicon dioxide accounts for 0.2% of the mass of the strontium ferrite pre-sintered powder.

[0124] Example 9

[0125] This embodiment provides a method for regulating the sintering of strontium ferrite material. The only difference compared with Example 5 is that the D50 particle size of the strontium ferrite pre-sintered powder in preparing the fourth ferrite material is 0.5-1μm, and the mass of silicon dioxide accounts for 0.5% of the mass of the strontium ferrite pre-sintered powder.

[0126] Example 10

[0127] This embodiment provides a method for regulating the sintering of strontium ferrite materials. The only difference compared with Example 5 is that the D50 particle size of the strontium ferrite pre-sintered powder in preparing the fourth ferrite material is 0.5-1μm, and the mass of silicon dioxide accounts for 0.6% of the mass of the strontium ferrite pre-sintered powder.

[0128] Embodiment 11

[0129] This embodiment provides a method for controlling the sintering of strontium ferrite material. The only difference compared with the embodiment 1 is that the mass of silicon dioxide in the preparation of the first ferrite material accounts for 0.3% of the mass of the strontium ferrite pre-sintered powder.

[0130] Example 12

[0131] This embodiment provides a method for controlling the sintering of strontium ferrite material. The only difference compared with the embodiment 1 is that the mass of silicon dioxide in the preparation of the first ferrite material accounts for 0.6% of the mass of the strontium ferrite pre-sintered powder.

[0132] Embodiment 13

[0133] This embodiment provides a method for regulating the sintering of strontium ferrite material, which is different from that of embodiment 1 only in that the first ferrite material is ball-milled to a target D50 particle size of 0.6 μm.

[0134] Embodiment 14

[0135] This embodiment provides a method for regulating the sintering of strontium ferrite material, which is different from that of embodiment 1 only in that the first ferrite material is ball-milled to a target D50 particle size of 1.0 μm.

[0136] Embodiment 15

[0137] This embodiment provides a method for regulating the sintering of strontium ferrite material. The only difference compared with the embodiment 1 is that the sintering temperature in preparing the first ferrite material is 1190°C.

[0138] Example 16

[0139] This embodiment provides a method for regulating the sintering of strontium ferrite material. The only difference compared with the embodiment 1 is that the sintering temperature in the preparation of the first ferrite material is 1260°C.

[0140] Embodiment 17

[0141] This embodiment provides a method for regulating the sintering of strontium ferrite material. The only difference compared with the embodiment 1 is that the molar ratio of calcium carbonate to silicon dioxide in the preparation of the first ferrite material is 1.5:1.

[0142] Embodiment 18

[0143] This embodiment provides a method for regulating the sintering of strontium ferrite material. The only difference compared with the embodiment 1 is that the molar ratio of calcium carbonate to silicon dioxide in the preparation of the first ferrite material is 3.0:1.

[0144] Embodiment 19

[0145] This embodiment provides a method for regulating the sintering of strontium ferrite material, which is different from that of embodiment 2 only in that the second ferrite material is ball-milled to a target D50 particle size of 0.6 μm.

[0146] Embodiment 20

[0147] This embodiment provides a method for regulating the sintering of strontium ferrite material, which is different from that of embodiment 2 only in that the second ferrite material is ball-milled to a target D50 particle size of 0.95 μm.

[0148] Embodiment 21

[0149] This embodiment provides a method for regulating the sintering of strontium ferrite material. The only difference compared with the embodiment 2 is that the sintering temperature in preparing the second ferrite material is 1150°C.

[0150] Embodiment 22

[0151] This embodiment provides a method for regulating the sintering of strontium ferrite material. The only difference compared with the embodiment 2 is that the sintering temperature in preparing the second ferrite material is 1250°C.

[0152] Embodiment 23

[0153] This embodiment provides a method for regulating the sintering of strontium ferrite material. The only difference compared with Example 2 is that the molar ratio of calcium carbonate to silicon dioxide in the preparation of the second ferrite material is 1.0:1.

[0154] Embodiment 24

[0155] This embodiment provides a method for regulating the sintering of strontium ferrite material. The only difference compared with Example 2 is that the molar ratio of calcium carbonate to silicon dioxide in the preparation of the second ferrite material is 2.0:1.

[0156] Embodiment 25

[0157] This embodiment provides a method for regulating the sintering of strontium ferrite material. The only difference compared with the embodiment 6 is that the sintering temperature in the preparation of the third ferrite material is 1140°C.

[0158] Embodiment 26

[0159] This embodiment provides a method for regulating the sintering of strontium ferrite material. The only difference compared with Embodiment 6 is that the sintering temperature in preparing the third ferrite material is 1220°C.

[0160] Embodiment 27

[0161] This embodiment provides a method for regulating the sintering of strontium ferrite material. The only difference compared with Example 6 is that the molar ratio of calcium carbonate to silicon dioxide in the preparation of the third ferrite material is 1:1.

[0162] Embodiment 28

[0163] This embodiment provides a method for regulating the sintering of strontium ferrite material. The only difference compared with Example 6 is that the molar ratio of calcium carbonate to silicon dioxide in the preparation of the third ferrite material is 1.8:1.

[0164] Embodiment 29

[0165] This embodiment provides a method for regulating the sintering of strontium ferrite material. The only difference compared with the embodiment 5 is that the sintering temperature in the preparation of the fourth ferrite material is 1130°C.

[0166] Embodiment 30

[0167] This embodiment provides a method for regulating the sintering of strontium ferrite material. The only difference compared with the embodiment 5 is that the sintering temperature in the preparation of the fourth ferrite material is 1230°C.

[0168] Embodiment 31

[0169] This embodiment provides a method for regulating the sintering of strontium ferrite materials. The only difference compared with the embodiment 5 is that the molar ratio of calcium carbonate to silicon dioxide in the preparation of the fourth ferrite material is 1:1.

[0170] Embodiment 32

[0171] This embodiment provides a method for regulating the sintering of strontium ferrite materials. The only difference compared with Embodiment 5 is that the molar ratio of calcium carbonate to silicon dioxide in the preparation of the fourth ferrite material is 2:1.

[0172] Taking Examples 1-6 as examples, the demagnetization curves of the obtained strontium ferrite materials are as follows: Figure 2-7 As shown, from Figure 2-7It can be seen that the methods provided in Examples 1-6 can produce products with performance that meets the requirements, and the squareness of the demagnetization curve is high, and the magnetic energy product of the product is large.

[0173] With reference to GB / T 3217-2013 "Magnetic Test Methods for Permanent Magnetic (Hard Magnetic) Materials", the magnetic properties of the ferrite materials in the above embodiment were tested; wherein, the magnetic properties were tested using a LE-AMH 500 permanent magnetic material BH instrument (double coil method), as shown in Table 1;

[0174] With reference to GB / T 4472-2011 “Determination of density and relative density of chemical products”, the volume density of the ferrite material in the above embodiment was tested, as shown in Table 1.

[0175] Table 1

[0176]

[0177]

[0178]

[0179] From the data in Table 1, we can see the following points:

[0180] (1) It can be seen from the data of Examples 1-6 that the methods provided in Examples 1 and 3 can prepare a first ferrite material, the methods provided in Examples 2 and 4 can prepare a second ferrite material, the method provided in Example 5 can prepare a fourth ferrite material, and the method provided in Example 6 can prepare a third ferrite material, and can meet the performance requirements.

[0181] (2) From the data of Examples 1 and 7-8, and Examples 5 and 19-20, it can be seen that the present invention preferably regulates the amount of silicon dioxide added in the additive according to the D50 particle size of the strontium ferrite pre-sintered material powder. From the data of Examples 1 and 11-12, it can be seen that the present invention further regulates the amount of silicon dioxide added by regulating the percentage of the mass of silicon dioxide in the mass of the strontium ferrite pre-sintered material powder, which can further avoid the influence of too high or too low silicon dioxide content on the performance of the ferrite material, thereby obtaining a ferrite material that meets the performance requirements.

[0182] (3) From the data of Examples 1 and 13-14, and Examples 2 and 19-20, it can be seen that the D50 particle size after ball milling in Examples 13-14 and 19-20 is not within the preferred control range of the present invention, and ferrite materials meeting the performance requirements cannot be prepared. It can be seen that the present invention can further regulate the sintering activity of the powder by preferentially controlling the D50 particle size range after ball milling, thereby obtaining a ferrite material meeting the performance requirements.

[0183] (4) From the data of Examples 1 and 15-16, 2 and 21-22, 6 and 25-26, and 5 and 29-30, it can be seen that the sintering temperatures in Examples 15-16, 21-22, 25-26, and 29-30 are not within the preferred control range of the present invention, and ferrite materials meeting the performance requirements cannot be prepared. It can be seen that the present invention can further regulate the grain growth process by preferentially controlling the sintering temperature, thereby obtaining a ferrite material meeting the performance requirements.

[0184] (5) From the data of Examples 1 and 17-18, 2 and 23-24, 6 and 27-28, and 5 and 31-32, it can be seen that the molar ratio of calcium carbonate to silicon dioxide in Examples 17-18, 23-24, 27-28, and 31-32 is not within the preferred control range of the present invention, and a ferrite material meeting the performance requirements cannot be prepared. It can be seen that the present invention can further regulate the composition of the silicate formed during the sintering process by preferentially controlling the molar ratio of calcium carbonate to silicon dioxide. Silicate liquid phases of different compositions have different viscosities at high temperatures and have different effects on the grains, thereby obtaining a ferrite material meeting the performance requirements.

[0185] In summary, the method provided by the present invention can adapt the magnetic powder characteristics, the selection of additives, ball milling and sintering processes, can achieve quantitative control of magnet performance, can quickly produce customized magnets that meet specific performance requirements, and avoids the need for repeated testing of additives and sintering processes when using a single magnetic powder, thereby significantly improving production efficiency and reducing production costs.

[0186] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for regulating sintered strontium ferrite material, characterized in that: The method comprises the following steps: (1) According to the D50 particle size of the strontium ferrite pre-sintered powder and the performance requirements of the strontium ferrite material, the type and ratio of the additives are adjusted, and the strontium ferrite pre-sintered powder, the additives and the dispersant are ball-milled until the target D50 particle size is reached to obtain a mixed slurry; (2) dehydrating the mixed slurry obtained in step (2), and then sequentially performing orientation wet pressing and drying to obtain a green body; (3) sintering the green body obtained in step (2), wherein the heating rate is controlled to reach the sintering temperature and the temperature is maintained, and then cooled to obtain a strontium ferrite material.

2. The method according to claim 1, characterized in that The additives in step (1) include silicon dioxide and calcium carbonate; Preferably, the additive further comprises bismuth oxide and / or aluminum oxide; Preferably, when the D50 particle size of the strontium ferrite pre-sintered powder is less than 1 μm, the mass of silicon dioxide accounts for 0.5-0.6% of the mass of the strontium ferrite pre-sintered powder; Preferably, when the D50 particle size of the strontium ferrite pre-sintered powder is 1-3 μm, the mass of silicon dioxide accounts for 0.4-0.5% of the mass of the strontium ferrite pre-sintered powder; Preferably, when the D50 particle size of the strontium ferrite pre-sintered powder is greater than 3 μm, the mass of silicon dioxide accounts for 0.2-0.4% of the mass of the strontium ferrite pre-sintered powder.

3. The method according to claim 1, characterized in that The strontium ferrite pre-sintered powder in step (1) is pure M-phase strontium ferrite; Preferably, the chemical formula of the strontium ferrite pre-sintered powder is SrFe x O 19 , where the value of X is 11-12; Preferably, the dispersant comprises calcium gluconate and / or sodium carboxymethyl cellulose; Preferably, the mass of the dispersant accounts for 0.3-0.5% of the mass of the strontium ferrite pre-sintered powder; Preferably, a solvent is also added during the ball milling; Preferably, the solvent comprises water; Preferably, the solid-liquid ratio of the mixed slurry in the ball mill is 1:(1.5-2.5); Preferably, the grinding balls used in the ball milling include stainless steel balls; Preferably, the diameter of the grinding balls used in the ball milling is 2-5 mm; Preferably, the mass ratio of the strontium ferrite pre-sintered powder to the grinding balls in the ball mill is 1:(10-20).

4. The method according to claim 1, characterized in that: Step (2) of dehydrating the mixed slurry until the mass percentage of water in the mixed slurry is 30-50%; Preferably, the pressure of the oriented wet pressing molding is 4.5-6.5 MPa; Preferably, the holding time of the oriented wet pressing molding is 30-60s; Preferably, the maximum orientation magnetic induction intensity of the orientation wet pressing molding is 0.5-1.5T; Preferably, the drying temperature is 60-90°C; Preferably, the drying time is 2-4 hours.

5. The method according to claim 1, characterized in that The sintering temperature in step (3) is 1150-1250° C. Preferably, the insulation time is 10-60min; Preferably, the heating process includes: firstly heating to 800° C. at a first heating rate, and then heating to the sintering temperature at a second heating rate; Preferably, the first heating rate is ≤5°C / min; Preferably, the second heating rate is ≤10°C / min.

6. The method according to any one of claims 1 to 5, characterized in that: The strontium ferrite material is divided according to remanence and coercive force, including a first ferrite material, a second ferrite material, a third ferrite material and a fourth ferrite material; Preferably, the properties of the first ferrite material meet the following requirements: remanence Br is 4150-4250Gs, coercivity Hcj is 3400-3700Oe, maximum magnetic energy product BH is 4.1-4.3MGOe, and volume density is ≥5.0g / cm 3 ; Preferably, the properties of the second ferrite material meet the following requirements: remanence Br is 4050-4150Gs, coercivity Hcj is 4200-4400Oe, maximum magnetic energy product BH is 4.0-4.2MGOe, and volume density is ≥4.95g / cm 3 ; Preferably, the performance of the third ferrite material meets the following requirements: remanence Br is 4000-4100 Gs, coercivity Hcj is 4300-4500 Oe, maximum magnetic energy product BH is 3.9-4.1 MGOe, and volume density is ≥4.90 g / cm 3 ; Preferably, the performance of the fourth ferrite material meets the following requirements: remanence Br is 3850-3950Gs, coercivity Hcj is 4600-4700Oe, maximum magnetic energy product BH is 3.7-4.0MGOe, and volume density is ≥4.88g / cm 3 .

7. The method according to claim 6, characterized in that When the strontium ferrite material is the first ferrite material, the D50 particle size of the strontium ferrite pre-sintered powder is ≥2 μm; Preferably, when the strontium ferrite material is the first ferrite material, the molar ratio of calcium carbonate to silicon dioxide in the additive is (1.8-2.5):1; Preferably, when the strontium ferrite material is the first ferrite material, the mass percentage of bismuth oxide in the additive to the mass of the strontium ferrite pre-sintered powder is ≤1%; Preferably, when the strontium ferrite material is the first ferrite material, the rotation speed of the ball mill is 50-100 rpm; Preferably, when the strontium ferrite material is the first ferrite material, the ball milling time is 8-20 hours; Preferably, when the strontium ferrite material is the first ferrite material, the ball milling is performed to a target D50 particle size of 0.7-0.9 μm; Preferably, when the strontium ferrite material is the first ferrite material, the sintering temperature is 1200-1250°C.

8. The method according to claim 6, characterized in that When the strontium ferrite material is the second ferrite material, the D50 particle size of the strontium ferrite pre-sintered powder is 1-3 μm; Preferably, when the strontium ferrite material is the second ferrite material, the molar ratio of calcium carbonate to silicon dioxide in the additive is (1.5-1.8):1; Preferably, when the strontium ferrite material is the second ferrite material, the rotation speed of the ball mill is 50-150 rpm; Preferably, when the strontium ferrite material is the second ferrite material, the ball milling time is 12-24 hours; Preferably, when the strontium ferrite material is the second ferrite material, the ball milling is performed to a target D50 particle size of 0.65-0.9 μm; Preferably, when the strontium ferrite material is the second ferrite material, the sintering temperature is 1180-1220°C.

9. The method according to claim 6, characterized in that When the strontium ferrite material is the third ferrite material, the D50 particle size of the strontium ferrite pre-sintered powder is 1-3 μm; Preferably, when the strontium ferrite material is the third ferrite material, the molar ratio of calcium carbonate to silicon dioxide in the additive is (1.2-1.5):1; Preferably, when the strontium ferrite material is the third ferrite material, the rotation speed of the ball mill is 100-200 rpm; Preferably, when the strontium ferrite material is the third ferrite material, the ball milling time is 16-36 hours; Preferably, when the strontium ferrite material is the third ferrite material, the ball milling is performed to a target D50 particle size of 0.6-0.8 μm; Preferably, when the strontium ferrite material is the third ferrite material, the sintering temperature is 1150-1200°C.

10. The method according to claim 6, characterized in that When the strontium ferrite material is the fourth ferrite material, the D50 particle size of the strontium ferrite pre-sintered powder is ≤3 μm; Preferably, when the strontium ferrite material is the fourth ferrite material, the molar ratio of calcium carbonate to silicon dioxide in the additive is (1.2-1.5):1; Preferably, when the strontium ferrite material is the fourth ferrite material, the mass percentage of the aluminum oxide in the additive to the mass of the strontium ferrite pre-sintered powder is ≤1.5%; Preferably, when the strontium ferrite material is the fourth ferrite material, the rotation speed of the ball mill is 100-200 rpm; Preferably, when the strontium ferrite material is the fourth ferrite material, the ball milling time is 16-36 hours; Preferably, when the strontium ferrite material is the fourth ferrite material, the ball milling is performed to a target D50 particle size of 0.6-0.8 μm; Preferably, when the strontium ferrite material is the fourth ferrite material, the sintering temperature is 1150-1200°C.

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