Magnetic core with wide temperature range and low inductance change and preparation method thereof

Abstract

The invention relates to the technical field of magnetic cores, and particularly discloses a wide-temperature-range low-inductance-change magnetic core and a preparation method thereof. A wide-temperature-range low-inductance-change magnetic core is characterized in that raw materials comprise main components and additives, and the main components comprise, by mass, 64-69% of Fe203, 19-24% of ZnO, 9-12% of NiO and 3-5% of CuO; on the basis of the total mass of the main components, the additive comprises any one or a combination of more of 0.3 to 1.5 percent of Bi203, 0.2 to 1 percent of Al203 and 0.2 to 0.5 percent of SiO2. The magnetic core with the wide temperature range and the low inductance change can be used for inductance application and automobile circuit board manufacturing, high magnetic conductivity can be kept in the temperature range environment of-20 DEG C to 130 DEG C, the inductance change rate is smaller than or equal to 9.6%, and the magnetic core has excellent temperature change resistance stability.

Description

Technical Field

[0001] The present application relates to the field of magnetic core technology, and more specifically, to a magnetic core with a wide temperature range and low inductance variation and a preparation method thereof. Background Art

[0002] As the core component of inductor manufacturing, magnetic cores are increasingly used in electronic circuits, especially in electromagnetic components such as inductors and transformers. The performance of magnetic cores directly affects the working effect and stability of these components.

[0003] However, traditional core materials fail to fully consider the impact of temperature on core performance. In high and low temperature environments, the magnetic permeability often decreases significantly, resulting in large changes in inductance, which affects the working stability and reliability of the entire circuit. In the manufacture of automotive circuit boards, due to the complexity of the automotive operating environment, the core needs to withstand large temperature changes, and the temperature stability of the core is particularly critical.

[0004] With respect to the above-mentioned related technologies, the inventors found that most of the magnetic cores available on the market have poor resistance to temperature changes. When used in a temperature range of -20 to 130°C, the inductance change often exceeds 10%. This instability limits the application of magnetic cores in high-performance fields. Summary of the invention

[0005] In order to enhance the temperature variation resistance of the magnetic core and improve the stability of the magnetic core when used in a wide temperature range environment, the present application provides a magnetic core with low inductance variation in a wide temperature range and a preparation method thereof.

[0006] In the first aspect, the present application provides a magnetic core with low inductance variation over a wide temperature range, adopting the following technical solution: a magnetic core with low inductance variation over a wide temperature range, wherein the raw materials include a main component and an additive, and the main component includes 64-69% Fe2O3, 19-24% ZnO, 9-12% NiO and 3-5% CuO in terms of mass percentage; Based on the total mass of the main components, the additives include any one or more combinations of 0.3-1.5% Bi2O3, 0.2-1% Al2O3 and 0.2-0.5% SiO2.

[0007] By adopting the above technical scheme, Fe203, ZnO, NiO and CuO all have good magnetic permeability. The nickel-zinc material with a wide temperature range and low specific temperature coefficient can improve the magnetic properties of the magnetic core within a wide temperature range to obtain a magnetic core with higher magnetic permeability. The addition of CuO can increase the density and saturation magnetic induction intensity of nickel-zinc ferrite and reduce the coercive force of nickel-zinc ferrite.

[0008] Bi203 can be used as a grain growth promoter in the sintering process to promote grain growth, help form a more uniform microstructure, increase the density of the magnetic core, increase the initial magnetic permeability of the magnetic core, and reduce magnetic loss; the use of Al203 and Si02 additives can help increase the resistivity of the material, reduce eddy current losses, and improve the high-frequency performance and thermal stability of the magnetic core. The FeSiO3 produced by SiO2 during the sintering process exists between the grain boundaries, which can inhibit grain growth, refine the grains and increase coercivity.

[0009] Furthermore, the inventors found that under the raw material ratio of the present application, by accurately controlling the dosage relationship between the raw materials, a magnetic core product with high inductance stability in a wide temperature range can be obtained, which significantly improves the core's ability to resist temperature changes.

[0010] Optionally, based on the total mass of the main components as a calculation basis, the additive further includes 0.2-0.5% ZrO2 and 0.1-0.3% Y2O3.

[0011] By adopting the above technical solution, the inventors found that the appropriate amount of zirconium doping can significantly improve the inductance stability of the magnetic core under a wide temperature range. On the one hand, this may be because ZrO2 can promote the transformation of the lattice, so that the magnetic core material maintains a stable tetragonal or cubic phase at high temperatures, effectively optimizes the lattice structure of the magnetic core material, improves the high-temperature structural stability of the magnetic core material, reduces the volume change and shear strain caused by the crystal transformation, and improves the inductance stability of the magnetic core at different temperatures. On the other hand, it may be due to the ZrO2 coating caused by the appropriate amount of 4+ The surface doping of nickel-zinc-copper ferrite stabilizes the surface structure of the core, improves the cycle stability and rate performance. The improved stability of the surface structure helps the core maintain inductance stability over a wide temperature range.

[0012] Y2O3 as a stabilizer, Y 3+ It not only reduces the purification temperature of ZrO2 crystals, but also introduces oxygen vacancies to produce lattice distortion, allowing the high-temperature phases (tetragonal and cubic phases) of ZrO2 to exist stably at low temperatures, further ensuring the structural stability of the core over a wide temperature range, reducing the impact of slight structural changes on the inductance stability of the core, and ensuring the inductance stability of the core over a wide temperature range.

[0013] Optionally, based on the total mass of the main components as a calculation basis, a binder and 0.01-0.05% of a defoaming agent are also included, wherein the binder is 0.6-1% of a silicone resin and 0.5-1% of CaCO3.

[0014] Optionally, the calcium carbonate is active nano calcium carbonate.

[0015] Optionally, the silicone resin is a dealcoholized silicone resin.

[0016] The inventors found that silicone resin has excellent high and low temperature resistance and electrical insulation, and can maintain a stable molecular structure within a wide temperature range, thereby ensuring the inductance stability of the magnetic core under a wide temperature range. Active nano-calcium carbonate has a high specific surface area and a small particle size, and has excellent dispersibility. The evenly dispersed nano-calcium carbonate particles can better interact with silicone resin molecules, effectively fill the pores in the silicone resin, and form a more uniform bonding layer. This helps to increase the interface area between the silicone resin and the magnetic core material, thereby improving the bonding strength, so that a tighter structure is formed between the magnetic core raw materials, and the mechanical properties of the magnetic core are improved.

[0017] By adopting the above technical solution, the reinforcing effect and dispersion compatibility of nano-calcium carbonate combined with the high and low temperature resistance of silicone resin can effectively reduce the eddy current loss and hysteresis loss of the magnetic core during operation, and significantly improve the inductance stability of the magnetic core in a wide temperature range.

[0018] In addition, when using dealcoholized silicone adhesive, small alcohol molecules are released during the curing process. Compared with other types of silicone resins, they are less volatile and more environmentally friendly.

[0019] In a second aspect, the present application provides a method for preparing a magnetic core with a wide temperature range and low inductance variation, using the following technical solution: A method for preparing a magnetic core with a wide temperature range and low inductance variation comprises the following steps: S1: Mixing Fe2O3, ZnO, NiO and CuO according to the raw material ratio, and then wet ball milling and spray granulation to obtain a mixture A; S2: pre-calcining the mixed material A under an inert gas atmosphere at a pre-calcining temperature of 760-820° C. for a holding time of 1.5-2 h to obtain a pre-calcined material; S3: Add additives, binders and defoamers to the pre-burned material, and perform secondary wet ball milling to obtain a mixture B; S4: spray granulation on mixed material B to obtain granular material; S5: Pressing and molding the granular material by cold isostatic pressing technology to obtain a blank; S6: vacuum sintering the blank, and then cooling at a rate of 100-150°C / h, the sintering temperature is 1030-1050°C, and the holding time is 3.5-6h.

[0020] Optionally, the particle size of the mixture B is D50=0.5±0.1 μm.

[0021] Optionally, when sintering the blank in step S6, a staged heat treatment method is adopted: First, heat the temperature to 250-350℃ at a heating rate of 5-7℃ / min and keep it warm for 1-1.5h; Then increase the temperature to 760-820°C at a heating rate of 4-6°C / min and keep warm for 1.5-2.5h; Finally, the temperature was raised to 1030-1050°C at a heating rate of 2-4°C / min and kept at this temperature for 1-2h.

[0022] Optionally, the cold isostatic pressing treatment in step S5 is performed at a pressure of 200-300 MPa and a holding time of 25-35 min.

[0023] Optionally, the technical parameters of the spray granulation in step S4 are: The inlet air temperature is 260-320℃, the outlet air temperature is 85-120℃, the feeding frequency is 10-13Hz, and the sheet throwing frequency is 60Hz.

[0024] By adopting the above technical solution, the inventors found that segmented heat treatment sintering helps to accurately control the temperature of the magnetic core at different stages, and initially forms a stable crystal structure through low temperature treatment. In the subsequent heat treatment stage, the uniform growth of grains is further promoted by increasing the temperature, reducing defects and pores. Cold isostatic pressing of granular materials to obtain blanks can reduce the stress changes inside the magnetic core when the temperature changes.

[0025] Within the temperature and time range specified in this application, the process of combining cold isostatic pressing and staged heat treatment sintering can help further optimize the microstructure of the magnetic core, such as grain size, distribution and orientation, reduce stress changes and performance fluctuations inside the magnetic core when the temperature changes, and effectively improve the inductance stability of the product magnetic core within a wider temperature range when used.

[0026] In summary, this application has the following beneficial effects: 1. The present application achieves a magnetic core made of nickel-zinc-copper ferrite with high magnetic permeability and low magnetic loss by precisely controlling the ratio between the main components of the raw materials and the additives, thereby significantly improving the core's resistance to temperature changes and enabling the core to maintain inductance stability over a wide temperature range. The additives in the present application include ZrO2 and Y2O3, and the doping of zirconium optimizes the lattice structure of the core material, which helps to maintain the lattice structure of the core stable at high and low temperatures, reduces the volume change and shear strain caused by crystal transformation, and improves the inductance stability of the core at different temperatures.

[0027] 2. The present application uses a mixture of silicone resin and nano-active calcium carbonate as a binder. The evenly dispersed nano-calcium carbonate particles interact with the silicone resin molecules with high and low temperature performance, effectively filling the pores in the silicone resin and forming a more uniform bonding layer between the magnetic core materials. This allows the magnetic core to form a tighter structure during the sintering process, effectively reducing the eddy current loss and hysteresis loss of the magnetic core when it is working, thereby improving the inductance stability of the magnetic core over a wide temperature range.

[0028] 3. The method of the present application, through a process combining cold isostatic pressing and staged heat treatment sintering, allows the magnetic core material to undergo a solid-state phase change reaction at different temperature stages, thereby reducing crystal defects, further optimizing the crystal structure and magnetic domain wall properties of the magnetic core material, gradually releasing the thermal stress generated by the magnetic core material during the processing, and improving the temperature stability of the magnetic core, so that the magnetic core can still maintain a stable and excellent magnetic permeability in a wider temperature range, reducing the change in inductance strength. DETAILED DESCRIPTION

[0029] The following examples further illustrate the present application in detail. Example

[0030] Example 1 A magnetic core with low inductance change in a wide temperature range, wherein the raw materials include a main component, an additive, a defoamer and a binder, wherein the raw materials and amounts of the main component are shown in Table 1, and the total mass of the main component is used as the calculation basis. The raw materials and amounts of the additive, defoamer and binder are shown in Table 2, wherein the calcium carbonate is active nano calcium carbonate selected from Yuanjiang brand, 07563, with a particle size of 50-100nm; the defoamer is selected from Chaoqiangshi, JX-650; the silicone resin is a dealcoholized silicone resin selected from Tianxiang Technology, neutral (dealcoholized) sealing silicone rubber 519.

[0031] Table 1 Table 2 The method for preparing the magnetic core with wide temperature range and low inductance variation comprises the following steps: S1: Mixing Fe2O3, ZnO, NiO and CuO according to the raw material ratio, and then wet ball milling and spray granulation to obtain a mixture A; S2: placing mixed material A into a pre-burning furnace under a nitrogen atmosphere, pre-burning at 760° C. for 2 h to obtain a pre-burned material; S3: adding additives, binders and defoamers to the pre-sintered material, mixing and then performing secondary wet ball milling to obtain a mixture B, wherein the particle size of the mixture B is D50=0.5±0.1 μm; S4: Set the air inlet temperature to 260°C, the air outlet temperature to 85°C, the feeding frequency to 10Hz, and the sheet throwing frequency to 60Hz, and obtain granular material by spray granulation of mixed material B; S5: Using cold isostatic pressing technology, the pressure is set to 300 MPa, and the pressure is maintained for 25 minutes to press the granular material to obtain a blank; S6: The blank is subjected to vacuum stage-by-stage heating and sintering treatment through the following steps: First, the temperature was raised to 250°C at a heating rate of 5°C / min and kept at this temperature for 1.5 h; Then, the temperature was raised to 760°C at a heating rate of 4°C / min and kept at this temperature for 2 h; Finally, the temperature was raised to 1030°C at a heating rate of 3°C / min and kept at this temperature for 1.5 h; After sintering is completed, the temperature is lowered at a rate of 100°C / h to obtain the product.

[0032] Example 2 A magnetic core with low inductance variation over a wide temperature range is different from Example 1 in that the raw materials and amounts of the main components are shown in Table 1, the total mass of the main components is used as the calculation basis, and the raw materials and amounts of the additives, defoaming agents and binders are added as shown in Table 2; the preparation method of the magnetic core with low inductance variation over a wide temperature range comprises the following steps: S1: Mixing Fe2O3, ZnO, NiO and CuO according to the raw material ratio, and then wet ball milling and spray granulation to obtain a mixture A; S2: placing mixed material A into a pre-burning furnace under a nitrogen atmosphere, pre-burning at 780° C. for 1.5 h to obtain a pre-burned material; S3: adding additives, binders and defoamers to the pre-sintered material, mixing and then performing secondary wet ball milling to obtain a mixture B, wherein the particle size of the mixture B is D50=0.5±0.1 μm; S4: Set the air inlet temperature to 310°C, the air outlet temperature to 110°C, the feeding frequency to 11Hz, and the sheet throwing frequency to 60Hz, and obtain granular material by spray granulation of mixed material B; S5: Using cold isostatic pressing technology, the pressure is set to 200 MPa, and the pressure is maintained for 35 minutes to press the granular material to obtain a blank; S6: The blank is subjected to vacuum stage-by-stage heating and sintering treatment through the following steps: First, the temperature was raised to 300°C at a heating rate of 6°C / min and kept at this temperature for 1 h; Then, the temperature was raised to 780°C at a heating rate of 6°C / min and kept at this temperature for 2.5 h; Finally, the temperature was raised to 1040°C at a heating rate of 3°C / min and kept at this temperature for 1 h; After sintering is completed, the temperature is lowered at a rate of 150°C / h to obtain the product.

[0033] Example 3 A magnetic core with low inductance variation over a wide temperature range is different from Example 1 in that the raw materials and amounts of the main components are shown in Table 1, the total mass of the main components is used as the calculation basis, and the raw materials and amounts of the additives, defoaming agents and binders are added as shown in Table 2; the preparation method of the magnetic core with low inductance variation over a wide temperature range comprises the following steps: S1: Mixing Fe2O3, ZnO, NiO and CuO according to the raw material ratio, and then wet ball milling and spray granulation to obtain a mixture A; S2: placing mixed material A into a pre-burning furnace under a nitrogen atmosphere, pre-burning at 800° C. for 2 h to obtain a pre-burned material; S3: adding additives, binders and defoamers to the pre-sintered material, mixing and then performing secondary wet ball milling to obtain a mixture B, wherein the particle size of the mixture B is D50=0.5±0.1 μm; S4: Set the air inlet temperature to 310°C, the air outlet temperature to 120°C, the feeding frequency to 12Hz, and the sheet throwing frequency to 60Hz, and obtain granular material by spray granulation of mixed material B; S5: Using cold isostatic pressing technology, the pressure is set to 200 MPa, and the pressure is maintained for 30 minutes to press the granular material to obtain a blank; S6: The blank is subjected to vacuum stage-by-stage heating and sintering treatment through the following steps: First, the temperature was raised to 350°C at a heating rate of 7°C / min and kept at this temperature for 1 h; Then, the temperature was raised to 800°C at a heating rate of 5°C / min and kept at this temperature for 2h; Finally, the temperature was raised to 1050°C at a heating rate of 4°C / min and kept at this temperature for 1.5 h; After sintering is completed, the temperature is lowered at a rate of 120°C / h to obtain the product.

[0034] Example 4 A magnetic core with low inductance variation over a wide temperature range is different from Example 1 in that the raw materials and amounts of the main components are shown in Table 1, the total mass of the main components is used as the calculation basis, and the raw materials and amounts of the additives, defoaming agents and binders are added as shown in Table 2; the preparation method of the magnetic core with low inductance variation over a wide temperature range comprises the following steps: S1: Mixing Fe2O3, ZnO, NiO and CuO according to the raw material ratio, and then wet ball milling and spray granulation to obtain a mixture A; S2: Mixture A was placed in a pre-burning furnace under a nitrogen atmosphere and pre-burned at 820° C. for 1.5 h to obtain a pre-burned material; S3: adding additives, binders and defoamers to the pre-sintered material, mixing and then performing secondary wet ball milling to obtain a mixture B, wherein the particle size of the mixture B is D50=0.5±0.1 μm; S4: Set the air inlet temperature to 320°C, the air outlet temperature to 120°C, the feeding frequency to 13Hz, and the sheet throwing frequency to 60Hz, and obtain granular material by spray granulation of mixed material B; S5: Using cold isostatic pressing technology, the pressure is set to 250 MPa, and the pressure is maintained for 30 minutes to press the granular material to obtain a blank; S6: The blank is subjected to vacuum stage-by-stage heating and sintering treatment through the following steps: First, the temperature was raised to 250°C at a heating rate of 6°C / min and kept at this temperature for 1.5 h; Then, the temperature was raised to 820°C at a heating rate of 4°C / min and kept at this temperature for 1.5 h; Finally, the temperature was raised to 1050°C at a heating rate of 3°C / min and kept at this temperature for 2 h; After sintering is completed, the temperature is lowered at a rate of 130°C / h to obtain the product.

[0035] Example 5 A magnetic core with low inductance variation in a wide temperature range, which differs from Example 1 in that Y2O3 is not added, and other steps are the same as those of Example 1.

[0036] Example 6 A magnetic core with low inductance variation in a wide temperature range, which differs from Example 1 in that ZrO2 is not added, and other steps are the same as those of Example 1.

[0037] Example 7 A magnetic core with low inductance variation in a wide temperature range, which differs from Example 1 in that Y2O3 and ZrO2 are not added, and other steps are the same as those of Example 1.

[0038] Example 8 A magnetic core with low inductance variation over a wide temperature range, which differs from Example 1 in that the calcium carbonate in the binder is heavy calcium carbonate selected from calcium carbonate H325-1000, and the other steps are the same as those in Example 1.

[0039] Example 9 A magnetic core with low inductance variation in a wide temperature range is different from Example 1 in that the silicone resin in the binder is replaced with polyvinyl alcohol of the same mass, and the other steps are the same as those in Example 1.

[0040] Example 10 A magnetic core with low inductance variation in a wide temperature range is different from Example 1 in that step S6 is specifically: heating the blank to 1030-1050°C at a heating rate of 2-4°C / min, keeping the temperature for 3.5-6h, and then cooling at a rate of 100-150°C / h to obtain the blank.

[0041] Comparative Example Comparative Examples 1-4 A magnetic core with low inductance variation over a wide temperature range is different from Example 1 in that the raw materials and amounts of the main components are shown in Table 3, and the other steps are the same as those of Example 1.

[0042] Table 3 Performance Test The following related performance test was performed on a magnetic core with a wide temperature range and low inductance change of Examples 1-10 and Comparative Examples 1-4. Each group of related tests was performed 3 times, and the average value of the 3 times was taken as the final result and the final result was recorded in Table 4.

[0043] 1. With reference to the provisions of GB / T 35690-2017, under the conditions of number of turns N=20Ts, f=128kHz, and u=0.1v, the magnetic permeability μi of the magnetic cores with wide temperature range and low inductance variation obtained in Examples 1-10 and Comparative Examples 1-4 was tested at -20°C, 25°C, and 130°C respectively; 2. Referring to the provisions of GB / T 6553-2014, the Curie temperature Tc of the magnetic core with wide temperature range and low inductance change obtained in Examples 1-10 and Comparative Examples 1-4 was tested using CH3302 and an oven; 3. With reference to the provisions of ABNT NBR 14127-2008, the impact strength of the magnetic cores with wide temperature range and low inductance variation obtained in Examples 1-10 and Comparative Examples 1-4 was tested at -20°C, 25°C and 130°C.

[0044] Table 4 According to the performance test data of Examples 1-10 and Comparative Examples 1-4 in Table 4, it can be seen that the magnetic core with a wide temperature range and low inductance change prepared under the formulation dosage of the main raw material components and additives of the present application can maintain a high magnetic permeability within the temperature range of -20 to 130°C, the change rate of inductance value is ≤8.6%, and the impact strength reaches 15.5-18.2 kJ / m 2 This shows that the magnetic core with wide temperature range and low inductance change in the present application has excellent resistance to temperature change and mechanical properties, can maintain inductance stability in a wide temperature range, maintain high magnetic permeability, and can meet the requirements of magnetic core applications in high-performance fields and extreme temperature environments.

[0045] According to the performance test results of Examples 1 and 5-7, it can be seen that adding ZrO2 and Y2O3 as additives can significantly improve the inductance stability of the magnetic core in a wide temperature range, and further optimize the impact resistance of the magnetic core. This may be because the doping of zirconium optimizes the lattice structure of the magnetic core material, and Y2O3 as a stabilizer can ensure the optimization of ZrO2, so that the lattice structure of the magnetic core remains stable at high and low temperatures, reducing the volume change and shear strain caused by crystal transformation, and improving the inductance stability and mechanical properties of the magnetic core at different temperatures; it may also be due to the ZrO2 coating caused by the appropriate amount of 4+ The surface doping of nickel-zinc-copper ferrite stabilizes the surface structure of the core, improves the cycle stability and rate performance. The improved stability of the surface structure also helps the core maintain inductance stability over a wide temperature range.

[0046] According to the performance test results of Examples 1 and 8-9, it can be seen that the use of silicone resin and nano-active calcium carbonate as a binder can not only improve the impact resistance of the magnetic core, but also further improve the stability of the magnetic core against temperature changes. This is because the evenly dispersed nano-calcium carbonate particles interact with the silicone resin molecules with high and low temperature performance, effectively filling the pores in the silicone resin, forming a more uniform bonding layer between the magnetic core materials, so that the magnetic core forms a more compact structure during the sintering process, effectively reducing the hysteresis loss of the eddy current loss when the magnetic core is working, thereby improving the inductance stability of the magnetic core under a wide temperature range.

[0047] It can be seen from the performance test results of Example 1 and Example 10 that the process of combining cold isostatic pressing and staged heat treatment sintering allows the magnetic core material to undergo a solid-state phase change reaction at different temperature stages, reducing crystal defects, further optimizing the crystal structure and magnetic domain wall properties of the magnetic core material, gradually releasing the thermal stress generated by the magnetic core material during processing, and improving the temperature stability of the magnetic core, so that the magnetic core can still maintain a stable and excellent magnetic permeability in a wider temperature range, reducing the change in inductance strength.

[0048] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed. However, as long as it is within the scope of the claims of the present application, it shall be protected by the patent law.

Claims

1. A magnetic core with a wide temperature range and low inductance variation, the raw materials comprising a main component and an additive, characterized in that: In terms of mass percentage, the main components include 64-69% Fe2O3, 19-24% ZnO, 9-12% NiO and 3-5% CuO; Based on the total mass of the main components, the additives include any one or more combinations of 0.3-1.5% Bi2O3, 0.2-1% Al2O3 and 0.2-0.5% SiO2.

2. The magnetic core with wide temperature range and low inductance variation according to claim 1, characterized in that: Based on the total mass of the main components, the additives also include 0.2-0.5% ZrO2 and 0.1-0.3% Y2O3.

3. The magnetic core with wide temperature range and low inductance variation according to claim 1, characterized in that: The total weight of the main component is used as a calculation basis, and a binder and 0.01-0.05% of a defoaming agent are also included. The binder is 0.6-1% of a silicone resin and 0.5-1% of CaCO3.

4. The magnetic core with wide temperature range and low inductance variation according to claim 3, characterized in that: The calcium carbonate is active nano calcium carbonate.

5. The method for preparing a magnetic core with a wide temperature range and low inductance variation according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: Mixing Fe2O3, ZnO, NiO and CuO according to the raw material ratio, and then wet ball milling and spray granulation to obtain a mixture A; S2: pre-calcining the mixed material A under an inert gas atmosphere at a pre-calcining temperature of 760-820° C. for a holding time of 1.5-2 h to obtain a pre-calcined material; S3: Add additives, binders and defoamers to the pre-burned material, and perform secondary wet ball milling to obtain a mixture B; S4: spray granulation on mixed material B to obtain granular material; S5: Pressing and molding the granular material by cold isostatic pressing technology to obtain a blank; S6: vacuum sintering the blank, and then cooling at a rate of 100-150°C / h, the sintering temperature is 1030-1050°C, and the holding time is 3.5-6h.

6. The method for preparing a magnetic core with a wide temperature range and low inductance variation according to claim 5, characterized in that: The particle size of the mixture B is D50=0.5±0.1 μm.

7. The method for preparing a magnetic core with a wide temperature range and low inductance variation according to claim 5, characterized in that: When the blank is sintered in step S6, a staged heat treatment method is adopted: First, heat the temperature to 250-350℃ at a heating rate of 5-7℃ / min and keep it warm for 1-1.5h; Then increase the temperature to 760-820°C at a heating rate of 4-6°C / min and keep warm for 1.5-2.5h; Finally, the temperature was raised to 1030-1050°C at a heating rate of 2-4°C / min and kept at this temperature for 1-2h.

8. The method for preparing a magnetic core with a wide temperature range and low inductance variation according to claim 5, characterized in that: The cold isostatic pressing treatment condition in step S5 is 200-300 MPa, and the holding time is 25-35 min.

9. The method for preparing a magnetic core with a wide temperature range and low inductance variation according to claim 5, characterized in that: The technical parameters of the spray granulation in step S4 are: The inlet air temperature is 260-320℃, the outlet air temperature is 85-120℃, the feeding frequency is 10-13Hz, and the sheet throwing frequency is 60Hz.

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