High remanence magnetic core and method of making same

Abstract

The application belongs to the technical field of magnetic functional materials, and particularly relates to a high-remanence magnetic core and a preparation method thereof. The preparation method comprises the following steps: dispersing ferroferric oxide, a cobalt source and a boron source in ethanol, and performing a deposition reaction under heating to obtain modified ferroferric oxide; melting raw materials of an iron-based amorphous alloy to prepare an amorphous strip, crushing the amorphous strip after segmented heat treatment to obtain iron-based amorphous alloy particles; mixing the iron-based amorphous alloy particles, the modified ferroferric oxide obtained in step (1) and a silicon resin, and performing compression molding, and then performing sintering in a protective atmosphere to obtain the high-remanence magnetic core. The magnetic core prepared by the application has high saturation magnetic induction intensity, a high squareness ratio and good mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of magnetic functional materials technology, specifically relating to a high remanence magnetic core and its preparation method. Background Technology

[0002] With the rapid development of the new energy vehicle industry, new energy power electronic equipment such as DC charging piles, charging guns, and photovoltaic inverters have placed stringent requirements on DC leakage protection. In Type B (smooth DC detection) residual current protectors, magnetic modulation DC detection technology is the key to achieving high-precision DC leakage protection, and the core sensitive element of this technology—the magnetic modulation core—directly determines the accuracy and reliability of DC leakage detection.

[0003] Currently, amorphous and nanocrystalline soft magnetic alloys are widely used in various magnetic devices due to their high saturation magnetic induction (Bs can reach over 1.2T), high permeability, and excellent high-frequency characteristics. However, for the special application of magnetically modulated DC leakage current detection, the key performance indicator of the material is not the conventional high permeability, but the rectangularity ratio of the hysteresis loop (Br / Bs), that is, the degree of closeness between the remanent magnetic induction Br and the saturation magnetic induction Bs. This is because magnetic modulation technology utilizes the magnetic switching characteristics of highly remanent materials, that is, the magnetic core can achieve faster and more complete flux reversal under periodic excitation, thereby transforming a small DC bias into a significant positive and negative half-cycle time asymmetry. By detecting this time difference, the magnitude of the primary-side DC leakage current can be accurately inferred, significantly improving the detection sensitivity and signal-to-noise ratio of DC leakage current.

[0004] In existing technologies, the hysteresis loop of conventional soft magnetic cores is relatively inclined, with a rectangularity ratio typically between 0.5 and 0.75. Even with longitudinal magnetic field heat treatment, which can increase the rectangularity ratio to around 0.85, in actual production, due to limitations in material composition and process fluctuations, it is difficult for batch products to consistently exceed 0.90, let alone reach above 0.95. This situation limits the detection accuracy and anti-interference capability of magnetically modulated DC leakage current protectors.

[0005] Therefore, the market urgently needs high remanent nanocrystalline magnetic core materials with a rectangularity ratio of 0.95 or higher and a remanent magnetic induction intensity of 1T or higher to meet the high requirements of the existing market. Summary of the Invention

[0006] The purpose of this invention is to provide a high remanence magnetic core and its preparation method, which has high saturation magnetic induction, rectangularity ratio and good mechanical properties.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a method for preparing a high remanence magnetic core, comprising the following steps: (1) The iron oxide, cobalt source and boron source were dispersed in ethanol and a deposition reaction was carried out under heating conditions to obtain modified iron oxide; (2) The raw materials of iron-based amorphous alloy are melted and made into amorphous ribbons, which are then crushed after segmented heat treatment to obtain iron-based amorphous alloy particles. (3) The iron-based amorphous alloy particles, the modified iron oxide obtained in step (1) are mixed with silicon resin, pressed into shape, and sintered under a protective atmosphere to obtain the high remanence magnetic core.

[0008] Furthermore, the cobalt source mentioned in step (1) is cobalt chloride, and the boron source is sodium borohydride.

[0009] Further, in step (1), the molar ratio of iron(III) oxide, cobalt source and boron source is 1:(0.1-0.15):(0.1-0.15); the heating temperature is 50-70 °C, and the deposition reaction time is 2-5 h.

[0010] Further, the iron-based amorphous alloy described in step (2) is composed of the following components by mass percentage: Cu 1.25-1.35 wt%, Nb 4.9-5.4 wt%, Si 6.5-7.5 wt%, B 1.95-2.05 wt%, Sm 0.5-0.7 wt%, Co 0.78-1.10 wt%, with the balance being Fe.

[0011] Further, the segmented heat treatment steps in step (2) are as follows: under a longitudinal magnetic field of 600-800 A / m, heat treatment is performed at 350-380 ℃ for 1.5-2 h; after the magnetic field is removed, heat treatment is performed at 460-500 ℃ for 0.5-1 h, and then at 550-580 ℃ for 1.5-2 h.

[0012] Furthermore, in step (2), amorphous ribbon is prepared by single-roller spinning, and the rolling speed of the single-roller spinning is 40-50 m / s.

[0013] Further, in step (3), the mass ratio of the iron-based amorphous alloy particles, modified iron oxide and silicone resin is 1:(0.01-0.02):(0.02-0.05).

[0014] Further, in step (3), the pressing pressure is 1-3 GPa and the time is 20-40 s; the sintering temperature is 420-480 ℃ and the time is 1-2 h.

[0015] A second aspect of the present invention provides a high remanence magnetic core prepared by the preparation method described in the first aspect above.

[0016] The beneficial technical effects of this invention are as follows: 1. This invention improves the saturation magnetic flux density and mechanical properties of a magnetic core by adding cobalt boride-coated modified iron(III) oxide. Iron(III) oxide possesses excellent soft magnetic properties, and its combination with iron-based amorphous alloys can effectively increase the saturation magnetic flux density of the magnetic core. However, iron(III) oxide has low stability and is easily oxidized and degraded in air. Coating iron(III) oxide with cobalt boride improves its chemical stability, ensuring its long-term performance in the magnetic core. Simultaneously, the high strength and hardness of the boride, as a coating layer, effectively enhances the mechanical properties of the magnetic core.

[0017] 2. This invention adds appropriate amounts of Sm and Co elements to iron-based amorphous alloys, which can simultaneously improve the saturation magnetic induction and remanence. The rare earth element Sm can form hard magnetic nanocrystalline phases such as SmCo5, Sm(Co,Fe)5, Sm(Co,Nb)5, and Sm(Co,Cu)5 with transition elements such as Co and Fe, forming a two-phase composite structure with the α-Fe soft magnetic nanocrystalline phase. The α-Fe soft magnetic phase can increase the overall magnetic moment and improve the saturation magnetic induction, while the hard magnetic phases such as SmCo5 can provide pinning effect and improve the rectangularity ratio. Furthermore, by controlling the ratio of Sm to Co and using a segmented heat treatment process, an appropriate amount of hard magnetic phase is generated in the amorphous matrix, forming exchange coupling with the soft magnetic phase, promoting the stability of the magnetization state, and achieving a simultaneous increase in saturation magnetic induction and remanence while maintaining the alloy's low coercivity. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope image of the modified iron(III) oxide prepared in Example 1 of the present invention. Detailed Implementation

[0019] The following is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, all reagents or instruments used are conventional products obtained through commercial channels.

[0020] (I) Implementation Examples Example 1 Example 1 provides a method for preparing a high remanence magnetic core, comprising the following steps: (1) According to the ratio of ferric oxide, cobalt chloride, sodium borohydride and ethanol, 1 mol: 0.12 mol: 0.12 mol: 1 L, ferric oxide, cobalt chloride and sodium borohydride were added to ethanol and ultrasonically dispersed evenly. The mixture was reacted at 60 °C for 3 h. After centrifugation, washing and drying, modified ferric oxide was obtained. The scanning electron microscope image of the modified ferric oxide is shown below. Figure 1 As shown; (2) The raw materials were mixed evenly according to the proportion of Cu 1.3 wt%, Nb 5.2 wt%, Si 7.1 wt%, B 2 wt%, Sm 0.6 wt%, Co 0.95 wt%, and Fe 82.85 wt%, and then loaded into a melting furnace and melted evenly under an argon atmosphere to obtain a master alloy ingot. The master alloy ingot was crushed and cleaned, and then induction melted in a quartz tube. The roller speed was set to 50 m / s, and the amorphous ribbon was made by single-roller spinning. The amorphous ribbon was heat-treated at 360 ℃ for 1.8 h under a longitudinal magnetic field of 700 A / m. After the magnetic field was removed, it was first heat-treated at 480 ℃ for 0.8 h, and then heat-treated at 560 ℃ for 1.8 h. After crushing and grinding, iron-based amorphous alloy particles were obtained. (3) The iron-based amorphous alloy particles, modified iron oxide and silicone resin are ball-milled and mixed evenly according to the mass ratio of 1:0.01:0.03. The mixture is pressed at 2 GPa for 30s and then sintered at 460 °C for 1.5 h in an argon atmosphere to obtain a high remanence magnetic core.

[0021] This embodiment also provides a high remanence magnetic core prepared by the above method.

[0022] Example 2 Example 2 provides a method for preparing a high remanence magnetic core, comprising the following steps: (1) According to the ratio of iron oxide, cobalt chloride, sodium borohydride and ethanol, 1 mol: 0.1 mol: 0.1 mol: 1 L, iron oxide, cobalt chloride and sodium borohydride were added to ethanol and ultrasonically dispersed evenly. The mixture was heated at 50 °C for 2 h and then centrifuged, washed and dried to obtain modified iron oxide. (2) The raw materials were prepared in the proportion of Cu 1.25 wt%, Nb 4.9 wt%, Si 6.5 wt%, B 1.95 wt%, Sm 0.5 wt%, Co 0.78 wt%, and Fe 84.12 wt%. The raw materials were mixed evenly and loaded into a melting furnace. The furnace was melted evenly under an argon atmosphere to obtain a master alloy ingot. The master alloy ingot was crushed and cleaned, and then induction melted in a quartz tube. The roller speed was set to 40 m / s, and the amorphous ribbon was made by single-roller spinning. The amorphous ribbon was heat-treated at 350 ℃ for 1.5 h under a longitudinal magnetic field of 600 A / m. After the magnetic field was removed, it was first heat-treated at 460 ℃ for 0.5 h, and then heat-treated at 550 ℃ for 1.5 h. After crushing and grinding, iron-based amorphous alloy particles were obtained. (3) The iron-based amorphous alloy particles, modified iron oxide and silicone resin are ball-milled and mixed evenly according to the mass ratio of 1:0.01:0.02. The mixture is pressed at 1 GPa for 20s and then sintered at 420 °C for 2 h in an argon atmosphere to obtain a high remanence magnetic core.

[0023] This embodiment also provides a high remanence magnetic core prepared by the above method.

[0024] Example 3 Example 3 provides a method for preparing a high remanence magnetic core, comprising the following steps: (1) According to the ratio of iron oxide, cobalt chloride, sodium borohydride and ethanol, 1 mol: 0.15 mol: 0.15 mol: 1.2 L, iron oxide, cobalt chloride and sodium borohydride were added to ethanol and ultrasonically dispersed evenly. The mixture was heated at 70 °C for 5 h and then centrifuged, washed and dried to obtain modified iron oxide. (2) The raw materials are prepared in the proportion of Cu 1.35 wt%, Nb 5.4 wt%, Si 7.5 wt%, B 2.05 wt%, Sm 0.7 wt%, Co 1.10 wt%, and Fe 1.35 wt%. The raw materials are mixed evenly and loaded into a melting furnace. The furnace is melted evenly under an argon atmosphere to obtain a master alloy ingot. The master alloy ingot is crushed and cleaned, and then placed in a quartz tube for induction melting. The roller speed is set to 50 m / s, and the amorphous ribbon is made by single-roller spinning. The amorphous ribbon is heat-treated at 380 ℃ for 2 h under a longitudinal magnetic field of 800 A / m. After the magnetic field is removed, it is first heat-treated at 500 ℃ for 1 h, and then heat-treated at 580 ℃ for 2 h. After crushing and grinding, iron-based amorphous alloy particles are obtained. (3) According to the mass ratio of iron-based amorphous alloy particles, modified iron oxide and silicone resin 1:0.02:0.05, the iron-based amorphous alloy particles, the modified iron oxide and silicone resin in step (1) above are ball-milled and mixed evenly, pressed at 3 GPa for 40s to form, and sintered at 480 °C for 1 h in an argon atmosphere to obtain a high remanence magnetic core.

[0025] This embodiment also provides a high remanence magnetic core prepared by the above method.

[0026] (ii) Comparative Example Comparative Example 1 Comparative Example 1 is basically the same as Example 1, except that the amount of Co in step (2) is adjusted to 1.18 wt%, and Fe is adjusted to 82.62 wt%.

[0027] Comparative Example 2 Comparative Example 2 is basically the same as Example 1, except that step (1) is omitted and the modified iron(III) oxide in step (3) is replaced with iron(III) oxide.

[0028] (III) Test Examples The magnetic cores prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to performance tests.

[0029] Saturation magnetic induction intensity and rectangle ratio test: The saturation magnetic induction intensity and rectangle ratio of the magnetic core were tested using a soft magnetic DC (AC) tester. The test results are shown in Table 1.

[0030] Bending strength test: The magnetic cores of Examples 1-3 and Comparative Examples 1-2 were respectively processed into specimens with dimensions of 35 mm × 4 mm × 3 mm, and the test span was set to 30 mm. The specimens were placed on two support points of a universal testing machine, and a load was applied at the midpoint of the span through the upper indenter at a constant rate of 0.5 mm / min until the specimens fractured. During the loading process, the system automatically recorded the relationship curve between load and deflection and calculated the bending strength. The results are shown in Table 1.

[0031] Table 1 Test data of saturation magnetic induction, rectangularity ratio and bending strength As shown in Table 1, the magnetic core materials prepared in Examples 1-3 of the present invention have high saturation magnetic induction intensity, rectangularity ratio and good mechanical properties.

[0032] Compared to Example 1, Comparative Example 1, by adjusting Co to 1.18 wt%, showed a significant decrease in the saturation magnetic flux density and rectangularity of the magnetic core. This indicates that the Co content needs to be controlled within a suitable range (0.78-1.10 wt%). Excessive Co will disrupt the optimal ratio of Sm to Co, affecting the two-phase composite structure and exchange coupling of the soft and hard magnetic phases, leading to deterioration of magnetic properties. This invention, by controlling the ratio of Sm to Co and employing a staged heat treatment process, generates an appropriate amount of hard magnetic phase in the amorphous matrix, which forms exchange coupling with the soft magnetic phase, promoting magnetization stability. This achieves a simultaneous increase in saturation magnetic flux density and remanence while maintaining low coercivity in the alloy.

[0033] Compared to Example 1, Comparative Example 2, which replaced the modified iron oxide with unmodified iron oxide, showed a significant decrease in both the saturation magnetic induction and bending strength of the magnetic core. This indicates that adding cobalt boride coating to iron oxide can improve the saturation magnetic induction and mechanical properties of the magnetic core. This is because the cobalt boride coating can improve the chemical stability of iron oxide, preventing its oxidation and failure and ensuring its magnetic properties. On the other hand, the boride itself has high strength and high hardness, and as a coating layer, it can effectively improve the mechanical properties of the magnetic core.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A method for preparing a high remanence magnetic core, characterized in that, Includes the following steps: (1) The iron oxide, cobalt source and boron source were dispersed in ethanol and a deposition reaction was carried out under heating conditions to obtain modified iron oxide; (2) The raw materials of iron-based amorphous alloy are melted and made into amorphous ribbons, which are then crushed after segmented heat treatment to obtain iron-based amorphous alloy particles. (3) The iron-based amorphous alloy particles, the modified iron oxide obtained in step (1) are mixed with silicon resin, pressed into shape, and sintered under a protective atmosphere to obtain the high remanence magnetic core. In step (1), the molar ratio of iron(II,III) oxide, cobalt source, and boron source is 1:(0.1-0.15):(0.1-0.15); the heating temperature is 50-70 °C, and the deposition reaction time is 2-5 h. The iron-based amorphous alloy described in step (2) consists of the following components by mass percentage: Composition: Cu 1.25-1.35 wt%, Nb 4.9-5.4 wt%, Si 6.5-7.5 wt%, B 1.95-2.05 wt%, Sm 0.5-0.7 wt%, Co 0.78-1.10 wt%, balance Fe.

2. The method for preparing a high remanence magnetic core according to claim 1, characterized in that, The cobalt source mentioned in step (1) is cobalt chloride, and the boron source is sodium borohydride.

3. The method for preparing a high remanence magnetic core according to claim 1, characterized in that, The steps of the segmented heat treatment in step (2) are as follows: under a longitudinal magnetic field of 600-800 A / m, heat treatment is carried out at 350-380 ℃ for 1.5-2 h; after the magnetic field is removed, heat treatment is carried out at 460-500 ℃ for 0.5-1 h, and then heat treatment is carried out at 550-580 ℃ for 1.5-2 h.

4. The method for preparing a high remanence magnetic core according to claim 1, characterized in that, In step (2), amorphous ribbon is prepared by single-roller spinning, and the speed of single-roller spinning is 40-50 m / s.

5. The method for preparing a high remanence magnetic core according to claim 1, characterized in that, The mass ratio of the iron-based amorphous alloy particles, modified iron oxide and silicone resin in step (3) is 1:(0.01-0.02):(0.02-0.05).

6. The method for preparing a high remanence magnetic core according to claim 1, characterized in that, The pressing pressure in step (3) is 1-3 GPa and the time is 20-40 s; the sintering temperature is 420-480 ℃ and the time is 1-2 h.

7. A high remanence magnetic core prepared by the preparation method according to any one of claims 1-6.

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