Weather-resistant magnetic material for a mutual inductor and method for manufacturing the same

Abstract

The application belongs to the technical field of magnetic functional materials, and particularly relates to a weather-resistant magnetic material for a mutual inductor and a preparation method thereof. The weather-resistant magnetic material for the mutual inductor is composed of raw materials in the following mass percentages: Nb 5.2-5.8 wt%, Si 11-12.5 wt%, B 7.5-8.5 wt%, Cu 1.0-1.5 wt%, Co 0.1-0.2 wt%, Ni 0.05-0.15 wt%, Er 0.15-0.35 wt%, modified graphene 2-3 wt%, and the balance being Fe. The magnetic material prepared by the application has good soft magnetic properties, excellent high and low temperature stability, and outstanding mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of magnetic functional materials technology, specifically relating to a weather-resistant magnetic material for current transformers and its preparation method. Background Technology

[0002] In key sectors such as power systems, rail transit, and new energy, instrument transformers, as core equipment for power metering and relay protection, often operate in harsh environments with alternating high and low temperatures and extreme temperature differences. Currently, commonly used soft magnetic materials in commercially available instrument transformers mainly include silicon steel sheets, permalloy, ferrite, and amorphous nanocrystalline alloys. These materials generally possess characteristics such as high permeability, narrow hysteresis loops, low coercivity, and ease of magnetization and demagnetization, making them suitable for AC operating conditions and capable of rapidly responding to frequent changes in magnetic fields. Among them, amorphous nanocrystalline alloys stand out for their comprehensive performance. Their permeability is close to that of permalloy, their iron loss is much lower than that of silicon steel sheets (approximately 1 / 3 to 1 / 5 of that of silicon steel sheets), and their saturation magnetic flux density is higher than that of ferrite and permalloy. They also possess good processing performance and broad application prospects.

[0003] However, the amorphous and nanocrystalline alloys used in conventional instrument transformers are insufficient in terms of weather resistance. Under extreme temperature environments, they are prone to significant decreases in magnetic permeability and sharp increases in iron losses, leading to inaccurate metering, shortened service life, and even equipment failure, affecting the stable operation of the power system. Currently, the technological bottleneck in magnetic material research and development for the domestic instrument transformer industry lies in the fact that existing component ratios and heat treatment processes cannot simultaneously achieve high magnetic permeability, low iron losses, and temperature stability over a wide temperature range for amorphous and nanocrystalline materials, resulting in insufficient performance stability and reliability of products in harsh environments. To improve the technological competitiveness of instrument transformer products in high-end, harsh environment applications, it is necessary to optimize material component ratios and innovate heat treatment processes to achieve precise control over the grain size, grain boundary structure, and internal stress state of the material, thereby developing magnetic materials for instrument transformers with a wide temperature adaptability range and excellent weather resistance. Summary of the Invention

[0004] The primary objective of this invention is to provide a weather-resistant magnetic material for instrument transformers, which possesses excellent soft magnetic properties, superior high and low temperature stability, and outstanding mechanical properties.

[0005] The second objective of this invention is to provide a method for preparing the above-mentioned weather-resistant magnetic material for current transformers.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A weather-resistant magnetic material for instrument transformers is composed of the following raw materials in weight percentages: Nb 5.2-5.8 wt%, Si 11-12.5 wt%, B 7.5-8.5 wt%, Cu 1.0-1.5 wt%, Co 0.1-0.2 wt%, Ni 0.05-0.15 wt%, Er 0.15-0.35 wt%, modified graphene 2-3 wt%, and the balance being Fe.

[0008] Furthermore, the modified graphene is prepared by the following process:

[0009] (1) Add graphene to hydrofluoric acid solution for ultrasonic treatment, filter, wash and dry to obtain acid-treated graphene;

[0010] (2) The acid-treated graphene and hydrazine hydrate are added to the chemical plating solution, heated and stirred, filtered, washed and dried to obtain modified graphene.

[0011] Further, the mass fraction of the hydrofluoric acid solution in step (1) is 15-25%; the ratio of graphene to hydrofluoric acid solution is 0.5-1 g:1 L.

[0012] Further, the chemical plating solution in step (2) is composed of the following raw materials in parts by weight: 10 parts cobalt chloride, 2-2.5 parts tantalum chloride, 14-17 parts sodium citrate, 0.6-1 parts sodium hydroxide, and 1200-1600 parts water.

[0013] Furthermore, based on the amount of cobalt chloride in the electroless plating solution, the mass ratio of the acid-treated graphene, cobalt chloride, and hydrazine hydrate is 1:(10-16):(8-11); the heating and stirring temperature is 60-90 ℃, and the time is 1-2 h.

[0014] The above-mentioned method for preparing magnetic materials for weather-resistant instrument transformers includes the following steps:

[0015] (a) Under an argon atmosphere with a vacuum degree of <10-2 Pa, the raw materials are heated and stirred, and then poured into a mold to cool, to obtain a master alloy ingot;

[0016] (b) The master alloy ingot is crushed, cleaned, melted, and then amorphous ribbon is obtained by single-roller spinning.

[0017] (c) The amorphous ribbon is heat-treated and cooled to obtain a magnetic material.

[0018] Further, the specific process of heating and stirring in step (a) is as follows: first, keep warm at 800-1000 ℃ for 2-5 min, and then raise to 1500-1600 ℃ and stir for 10-20 min.

[0019] Furthermore, the roller speed during the single-roller belt-spinning process described in step (b) is 40-50 m / s.

[0020] Further, the specific steps of the heat treatment described in step (c) are as follows: under a transverse magnetic field of 5-20 kA / m, first heat-treat at 350-575 ℃ for 7-10 h, and then hold at 280-350 ℃ for 2-4 h.

[0021] Furthermore, the cooling rate described in step (c) is 50-80 °C / min.

[0022] The beneficial technical effects of this invention are as follows:

[0023] 1. This invention, through adjusting the constituent elements and combining them with heat treatment processes, enables the material to possess both excellent soft magnetic properties and temperature adaptability. The combination of Si and B elements with a secondary heat treatment process ensures stable nanocrystal formation, reduces the formation of Fe-B compounds, and effectively improves soft magnetic properties. Nb, with its high thermal stability and large atomic size, can form atomic size mismatches with iron, enhancing the material's amorphous formation capability. It also segregates at nanocrystal boundaries, hindering atomic diffusion and grain growth, and promoting the formation of small and uniform nanocrystals. Co and Ni, by forming competing phases with Fe, increase the disorder within the alloy, improving amorphous formation capability and temperature stability. During heat treatment, the rare earth element Er has a significant modifying effect on the brittle phase and adsorbs and purifies impurities, improving the thermal stability of the amorphous matrix, thus enabling the material to possess both excellent soft magnetic properties and temperature stability.

[0024] 2. This invention adds modified graphene to materials, which can improve the magnetic and mechanical properties of magnetic materials. Graphene has a high specific surface area and surface tension. After surface coating with cobalt and tantalum, cobalt gives graphene good soft magnetic properties and forms a strong interfacial bond with the iron-based matrix, thereby forming a fine magnetic domain structure, reducing the resistance to domain wall movement, and optimizing the magnetic properties of the material. Tantalum has a high melting point and thermal stability. Doping it into the coating can improve the stability of graphene in the alloy matrix. Dispersed in the matrix, it can hinder the growth of nanocrystals, thus refining the grains and forming dispersion reinforcement, improving the mechanical properties of the material. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope image of the modified graphene prepared in Example 1 of the present invention. Detailed Implementation

[0026] 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, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or 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.

[0027] (I) Implementation Examples

[0028] Example 1

[0029] Example 1 provides a weather-resistant magnetic material for current transformers, which is composed of the following raw materials in the indicated mass percentages: Nb 5.5 wt%, Si 11.8 wt%, B 8 wt%, Cu 1.3 wt%, Co 0.1 wt%, Ni 0.1 wt%, Er 0.25 wt%, modified graphene 2 wt%, and the balance being Fe;

[0030] The modified graphene is prepared by the following process:

[0031] (1) According to the ratio of graphene to hydrofluoric acid solution of 0.8 g: 1 L, graphene was added to a 20% hydrofluoric acid solution, ultrasonically treated for 25 min, filtered, washed and dried to obtain acid-treated graphene.

[0032] (2) First, prepare the chemical plating solution according to the following weight proportions: 10 parts cobalt chloride, 2.3 parts tantalum chloride, 15 parts sodium citrate, 0.8 parts sodium hydroxide, and 1400 parts water, and set aside. Then, based on the amount of cobalt chloride in the chemical plating solution, add the acid-treated graphene to the chemical plating solution according to the mass ratio of acid-treated graphene, cobalt chloride, and hydrazine hydrate of 1:13:10, and then add the reducing agent hydrazine hydrate. Stir at 70°C for 1 h, filter, wash, and dry to obtain modified graphene. The scanning electron microscope image of the modified graphene prepared in this embodiment is shown below. Figure 1 As shown.

[0033] This embodiment also provides a method for preparing the above-mentioned weather-resistant magnetic material for current transformers, the specific steps of which are as follows:

[0034] (a) After mixing the raw materials evenly according to the above mass percentages, transfer them into the melting furnace and evacuate to a vacuum of 10 under an argon atmosphere. -2 Pa, first heat to 900 ℃ and hold for 3 min, then heat to 1500 ℃ and stir electromagnetically for 15 min, then pour into a water-cooled mold, and obtain the master alloy ingot after cooling;

[0035] (b) The above-mentioned master alloy ingot is crushed and cleaned, placed in a quartz tube for induction melting, and amorphous ribbon is produced by single-roller spinning at a roller speed of 40 m / s.

[0036] (c) The above amorphous ribbon is heat-treated at 420 °C for 8 h under a transverse magnetic field of 15 kA / m, then held at 320 °C for 3 h, and finally cooled at a cooling rate of 50 °C / min to obtain a weather-resistant magnetic material for current transformers.

[0037] Example 2

[0038] Example 2 provides a weather-resistant magnetic material for current transformers, composed of the following raw materials by mass percentage: Nb 5.2 wt%, Si 11 wt%, B 7.5 wt%, Cu 1.0 wt%, Co 0.1 wt%, Ni 0.05 wt%, Er 0.15 wt%, modified graphene 2 wt%, with the balance being Fe;

[0039] The modified graphene is prepared by the following process:

[0040] (1) According to the ratio of graphene to hydrofluoric acid solution of 0.5 g: 1 L, graphene was added to a 15% hydrofluoric acid solution by mass, ultrasonic treatment for 20 min, and then filtered, washed and dried to obtain acid-treated graphene.

[0041] (2) First, prepare the chemical plating solution according to the following weight proportions: 10 parts cobalt chloride, 2 parts tantalum chloride, 14 parts sodium citrate, 0.6 parts sodium hydroxide, and 1200 parts water for later use; then, based on the amount of cobalt chloride in the chemical plating solution, add the acid-treated graphene to the chemical plating solution according to the mass ratio of acid-treated graphene, cobalt chloride and hydrazine hydrate 1:10:8, and then add the reducing agent hydrazine hydrate. Stir at 60°C for 1 h, filter, wash and dry to obtain modified graphene.

[0042] This embodiment also provides a method for preparing the above-mentioned weather-resistant magnetic material for current transformers, the specific steps of which are as follows:

[0043] (a) After mixing the raw materials evenly according to the above mass percentages, transfer them into the melting furnace and evacuate to a vacuum of 10 under an argon atmosphere. -2 Pa, first heat to 800 ℃ and hold for 2 min, then heat to 1500 ℃ and stir electromagnetically for 10 min, then pour into a water-cooled mold, and obtain the master alloy ingot after cooling;

[0044] (b) The above-mentioned master alloy ingot is crushed and cleaned, placed in a quartz tube for induction melting, and amorphous ribbon is produced by single-roller spinning at a roller speed of 40 m / s.

[0045] (c) The above amorphous ribbon is heat-treated at 350 °C for 7 h under a transverse magnetic field of 5 kA / m, then held at 280 °C for 2 h, and finally cooled at a cooling rate of 50 °C / min to obtain a weather-resistant magnetic material for current transformers.

[0046] Example 3

[0047] Example 3 provides a weather-resistant magnetic material for current transformers, composed of the following raw materials by mass percentage: Nb 5.8 wt%, Si 12.5 wt%, B 8.5 wt%, Cu 1.5 wt%, Co 0.2 wt%, Ni 0.15 wt%, Er 0.35 wt%, modified graphene 3 wt%, with the balance being Fe;

[0048] The modified graphene is prepared by the following process:

[0049] (1) According to the ratio of graphene to hydrofluoric acid solution 1 g: 1 L, graphene was added to a 25% hydrofluoric acid solution, ultrasonically treated for 30 min, filtered, washed and dried to obtain acid-treated graphene.

[0050] (2) First, prepare the chemical plating solution according to the following weight proportions: 10 parts cobalt chloride, 2.5 parts tantalum chloride, 17 parts sodium citrate, 1 part sodium hydroxide, and 1600 parts water for later use; then, based on the amount of cobalt chloride in the chemical plating solution, add the acid-treated graphene to the chemical plating solution according to the mass ratio of acid-treated graphene, cobalt chloride and hydrazine hydrate 1:16:11, and then add the reducing agent hydrazine hydrate. Stir at 90°C for 2 h, filter, wash and dry to obtain modified graphene.

[0051] This embodiment also provides a method for preparing the above-mentioned weather-resistant magnetic material for current transformers, the specific steps of which are as follows:

[0052] (a) After mixing the raw materials evenly according to the above mass percentages, transfer them into the melting furnace and evacuate to a vacuum of 10 under an argon atmosphere. -2 Pa, first heat to 1000 ℃ and hold for 5 min, then heat to 1600 ℃ and stir electromagnetically for 20 min, then pour into a water-cooled mold, and obtain the master alloy ingot after cooling;

[0053] (b) The above-mentioned master alloy ingot is crushed and cleaned, placed in a quartz tube for induction melting, and amorphous ribbon is produced by single-roller spinning at a roller speed of 50 m / s.

[0054] (c) The above amorphous ribbon is heat-treated at 575 °C for 10 h under a transverse magnetic field of 20 kA / m, then held at 350 °C for 4 h, and finally cooled at a cooling rate of 50 °C / min to obtain a weather-resistant magnetic material for current transformers.

[0055] (ii) Comparative Example

[0056] Comparative Example 1

[0057] Comparative Example 1 is basically the same as Example 1, except that Co, Ni and Er are omitted in Example 1.

[0058] Comparative Example 2

[0059] Comparative Example 2 is basically the same as Example 1, except that the modified graphene in Example 1 is omitted.

[0060] Comparative Example 3

[0061] Comparative Example 3 is basically the same as Example 1, except that tantalum chloride is omitted when preparing modified graphene.

[0062] (III) Test Examples

[0063] The magnetic materials prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to the following performance tests.

[0064] Permeability test: The permeability of Examples 1-3 and Comparative Examples 1-3 was measured using an impedance analyzer at room temperature and a frequency of 10 kHz. The results are shown in Table 1.

[0065] Coercivity: The coercivity of Examples 1-3 and Comparative Examples 1-3 was measured using a BH analyzer at room temperature. The results are shown in Table 1.

[0066] Rate of change of magnetic permeability at high and low temperatures: The rate of change of magnetic permeability of nanocrystalline ribbons at -40℃ to +150℃ was measured compared with that of nanocrystalline ribbons at room temperature. The results are shown in Table 1.

[0067] Mechanical property test: A magnetic material with a thickness of t is placed vertically between two parallel plates. The distance d between the parallel plates is shortened until the soft magnetic alloy strip is completely folded in half. The toughness of the soft magnetic alloy strip is expressed as ε=t / (dt). If 0<ε≤1, the soft magnetic alloy strip is brittle. If ε=1, it means that the soft magnetic alloy strip does not break when folded 180° and has good toughness. The results are shown in Table 1.

[0068] Table 1. Test results of soft magnetic properties and mechanical properties of magnetic materials

[0069]

[0070] As shown in Table 1, the magnetic materials prepared in Examples 1-3 of this invention have good soft magnetic properties, excellent high and low temperature stability, and outstanding mechanical properties.

[0071] Compared to Example 1, Comparative Example 1 omits Co, Ni, and Er from Example 1, resulting in a decrease in soft magnetic properties and significant fluctuations in high and low temperature stability. This indicates that adjusting the Co, Ni, and Er elements in the magnetic material can improve its soft magnetic properties and temperature adaptability. Specific analysis reveals that Co and Ni, by forming competing phases with Fe, increase the disorder within the alloy, thereby enhancing amorphous formation ability and temperature stability. The rare earth element Er, during heat treatment, has a significant modifying effect on the brittle phase and adsorbs and purifies impurities, improving the thermal stability of the amorphous matrix, thus enabling the material to possess both good soft magnetic properties and temperature stability.

[0072] Compared to Example 1, Comparative Example 2 omitted the modified graphene used in Example 1, and Comparative Example 3 omitted tantalum chloride during the preparation of modified graphene. Both the soft magnetic properties and mechanical properties of the materials showed a significant decrease, indicating that modified graphene can significantly improve the soft magnetic properties and mechanical properties of the materials. Specific analysis reveals that graphene has a high specific surface area and surface tension. After cobalt plating, graphene exhibits good soft magnetic properties and forms a strong interfacial bond with the iron-based matrix, thereby forming a fine magnetic domain structure, reducing the resistance to domain wall movement, and optimizing the magnetic properties of the material. Tantalum has a high melting point and thermal stability; its doping into the plating layer can improve the stability of graphene in the alloy matrix. Dispersed in the matrix, it can hinder the growth of nanocrystals, refining the grains and forming dispersion reinforcement, thus improving the mechanical properties of the material.

[0073] 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 weather-resistant magnetic material for current transformers, characterized in that, It is composed of the following raw materials in the indicated mass percentages: Nb 5.2-5.8 wt%, Si 11-12.5 wt%, B 7.5-8.5 wt%, Cu 1.0-1.5 wt%, Co 0.1-0.2 wt%, Ni 0.05-0.15 wt%, Er 0.15-0.35 wt%, modified graphene 2-3 wt%, with the balance being Fe; The modified graphene is prepared by the following process: (1) Add graphene to hydrofluoric acid solution for ultrasonic treatment, filter, wash and dry to obtain acid-treated graphene; (2) The acid-treated graphene and hydrazine hydrate are added to the chemical plating solution, heated and stirred, filtered, washed and dried to obtain modified graphene. The chemical plating solution is composed of the following raw materials in parts by weight: 10 parts cobalt chloride, 2-2.5 parts tantalum chloride, 14-17 parts sodium citrate, 0.6-1 parts sodium hydroxide, and 1200-1600 parts water.

2. The weather-resistant magnetic material for instrument transformers according to claim 1, characterized in that, The mass fraction of the hydrofluoric acid solution in step (1) is 15-25%; the ratio of graphene to hydrofluoric acid solution is 0.5-1 g:1 L.

3. The weather-resistant magnetic material for current transformers according to claim 1, characterized in that, The mass ratio of the acid-treated graphene, cobalt chloride, and hydrazine hydrate, based on the amount of cobalt chloride in the chemical plating solution, is 1:(10-16):(8-11); the heating and stirring temperature is 60-90 ℃, and the time is 1-2 h.

4. A method for preparing a weather-resistant magnetic material for an instrument transformer according to any one of claims 1-3, characterized in that, Includes the following steps: (a) In a vacuum degree <10 -2 Under an argon atmosphere of Pa, the raw materials are heated and stirred, then poured into a mold and cooled to obtain a master alloy ingot; (b) The master alloy ingot is crushed, cleaned, melted, and then amorphous ribbon is obtained by single-roller spinning. (c) The amorphous ribbon is heat-treated and cooled to obtain a magnetic material.

5. The method for preparing the weather-resistant magnetic material for current transformers according to claim 4, characterized in that, The specific process of heating and stirring in step (a) is as follows: first, keep warm at 800-1000 ℃ for 2-5 min, and then raise the temperature to 1500-1600 ℃ and stir for 10-20 min.

6. The method for preparing the weather-resistant magnetic material for current transformers according to claim 4, characterized in that, The roller speed during the single-roller belt-spinning process described in step (b) is 40-50 m / s.

7. The method for preparing the weather-resistant magnetic material for current transformers according to claim 4, characterized in that, The specific steps of the heat treatment described in step (c) are as follows: under a transverse magnetic field of 5-20 kA / m, first heat-treat at 350-575 ℃ for 7-10 h, and then keep at 280-350 ℃ for 2-4 h.

8. The method for preparing the weather-resistant magnetic material for current transformers according to claim 4, characterized in that, The cooling rate described in step (c) is 50-80 °C / min.

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