A nanocrystalline alloy magnetic core and its preparation process

Abstract

This invention discloses a nanocrystalline alloy magnetic core and its preparation process. The invention relates to the field of magnetic materials technology and comprises the following components by weight percentage: 81%–85% pure iron, 0.8%–1.2% pure copper, 8%–10% ferrosilicon, and 5.5%–8.5% ferroboron. This nanocrystalline alloy magnetic core and its preparation process, by uniformly spirally winding copper sheets around the inner and outer sides of the magnetic core, can delay the heating of the inner and outer surfaces of the core, reduce the temperature difference between the center of the core and the inner and outer sides, and make the temperature distribution in the center and sides of the core more uniform. This promotes more uniform elimination of internal stress and facilitates simultaneous nucleation and growth at different locations of the core during the second annealing step, resulting in more uniform grain size at the inner and outer locations of the core, thereby improving the core performance.

Description

Technical Field

[0001] This invention relates to the field of magnetic materials technology, specifically to a nanocrystalline alloy magnetic core and its preparation process. Background Technology

[0002] Current, voltage, and electrical energy are typically measured using instrument transformers. The core component of an instrument transformer is the magnetic core, whose performance directly determines the measurement accuracy. Nanocrystalline materials are composed of crystals with nanoscale dimensions (1-10 nm). Due to their extremely fine size, grain boundaries can account for 50% or more of the entire material. Their atomic arrangement differs from both ordered crystalline and disordered amorphous (glassy) states, and their properties also differ from those of crystalline or amorphous materials of the same composition. In many applications, traditional ferrite materials are insufficient, and an increasing number of EMC rectification solutions utilize inductors made from a new type of material called nanocrystalline magnetic cores. When measuring sinusoidal currents without a DC component, soft magnetic materials with high permeability are typically used to manufacture the magnetic core to improve measurement accuracy. Amorphous and nanocrystalline alloys possess excellent soft magnetic properties, especially nanocrystalline alloy cores, which exhibit superior comprehensive magnetic properties, including high saturation magnetic induction, high initial permeability, low Hc, low high-frequency loss under high magnetic induction, and higher resistivity than permalloy. Through longitudinal or transverse magnetic field treatment, high or low Br values ​​can be obtained. They are currently the best performing materials on the market and are widely used in high-power switching power supplies, inverters, magnetic amplifiers, high-frequency transformers, etc.

[0003] Chinese Patent Publication No. CN115881380A discloses a nanocrystalline alloy magnetic core comprising Cu, Si, B, Sr, Ir, Bi, Ni, Te, rare earth elements, and Fe. The contents of Cu, Si, B, Sr, Ir, Bi, Ni, Te, rare earth elements, and Fe are respectively: Cu 0.6-1.0%, Si 8.0-10.0%, B 5.5-8.0%, Sr 0.1-0.3%, Ir 0.05-0.15%, Bi 0.03-0.10%, Ni 0.8-1.5%, Te 0.1-0.3%, rare earth elements 0.01-0.04%, and the balance being Fe. This invention utilizes vacuum heat treatment of iron-based nanocrystalline magnetic cores: heating at a rate of 1℃ / min, setting the furnace exit temperature to 200℃, annealing at 540℃, and holding the annealing temperature for 60 minutes, representing the optimal processing technology for iron-based nanocrystalline magnetic cores. However, the aforementioned existing technologies have the following shortcomings: during the preparation process, the difference in cooling rates between the free surface and the roller-mounted surface leads to a significant difference in grain size between the two surfaces, affecting the magnetic properties of the core. Therefore, this invention provides a nanocrystalline alloy magnetic core and its preparation process to solve the above problems. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a nanocrystalline alloy magnetic core and its preparation process, solving the problems mentioned in the background section.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: a nanocrystalline alloy magnetic core, comprising the following components by weight percentage: 81%–85% pure iron, 0.8%–1.2% pure copper, 8%–10% ferrosilicon, and 5.5%–8.5% ferroboron.

[0006] A fabrication process for a nanocrystalline alloy magnetic core includes the following steps:

[0007] S1. Preparation of the master alloy:

[0008] S11. Pure iron, pure copper, ferrosilicon and ferroboron are used as raw materials. The raw materials are ultrasonically cleaned to remove surface dirt and then dried.

[0009] S12. Then place it in a vacuum melting furnace and repeatedly melt it to obtain a master alloy with uniform composition.

[0010] S2. The master alloy is wound to obtain the magnetic core;

[0011] S3. Vacuum heat treatment of the magnetic core: Place the magnetic core in a tube furnace and introduce nitrogen gas. Then, heat it to 500-510℃ at 10℃ / min, hold it for 15-20min, then heat it to 540-550℃ at 1℃ / min, hold it for 50-60min, and then remove it from the furnace when the temperature drops to 180-200℃ to obtain a nanocrystalline alloy magnetic core.

[0012] Preferably, the preparation process of the nanocrystalline alloy magnetic core further includes: S4, placing the nanocrystalline alloy magnetic core in a passivation solution and immersing it at room temperature for 100-120 minutes; then immersing and cleaning it with anhydrous ethanol, and then placing it in a drying oven at a temperature of 50-60°C for 40-60 minutes.

[0013] Preferably, the passivation solution is an iron-based phosphide passivation solution, and it is diluted to an 8% solution before use.

[0014] Preferably, the preparation process of the nanocrystalline alloy magnetic core further includes: S5, immersing the passivated nanocrystalline alloy magnetic core in a curing agent, then evacuating the air pressure to 0.01-0.03 MPa, letting it stand until no more bubbles emerge from the surface, then restoring the atmospheric pressure, and finally taking out the nanocrystalline alloy magnetic core and drying it in a drying oven at 90-100°C for 1.5-2 hours.

[0015] Preferably, the curing agent is selected from any one of silicone curing agents and polyurethane curing agents.

[0016] Preferably, in step S12, the internal pressure of the vacuum melting furnace is 3 × 10⁻⁶. -3 ~5×10 -3 Pa, the number of smelting times is 5 to 6.

[0017] Preferably, in step S3, during the heat treatment process, copper strips are wound inside and outside the magnetic core in a spiral shape, and the thickness of a single layer of copper strip is 0.1 to 0.3 mm.

[0018] Beneficial effects

[0019] This invention provides a nanocrystalline alloy magnetic core and its preparation process. Compared with the prior art, it has the following advantages:

[0020] (1) The nanocrystalline alloy magnetic core and its preparation process, by uniformly spirally winding copper sheets on the inner and outer sides of the magnetic core, can delay the heating of the inner and outer surfaces of the magnetic core, reduce the temperature difference between the middle of the magnetic core and the inner and outer sides, make the temperature distribution in the middle and the sides of the magnetic core more uniform, promote more uniform elimination of internal stress, and facilitate the simultaneous nucleation and growth at different positions of the magnetic core during the second annealing step, so that the grain size at the inner and outer positions of the magnetic core is more uniform, thereby improving the performance of the magnetic core.

[0021] (2) The nanocrystalline alloy magnetic core and its preparation process, by passivating and solidifying the magnetic core, increase the insulation between the magnetic core layers, thereby helping to reduce the loss of the magnetic core and improve the soft magnetic properties of the magnetic core. Attached Figure Description

[0022] Figure 1 A schematic diagram of a nanocrystalline alloy magnetic core with copper plating provided by the present invention and its preparation process;

[0023] Figure 2 The DSC curve of the nanocrystalline alloy magnetic core and its preparation process provided by the present invention;

[0024] Figure 3 TEM image of a nanocrystalline alloy magnetic core and its preparation process provided by the present invention;

[0025] Figure 4 This invention provides a method for testing the current-voltage characteristics of a nanocrystalline alloy magnetic core and its preparation process.

[0026] Figure 5 The physical properties of the nanocrystalline alloy magnetic core and its preparation process provided by the present invention;

[0027] Figure 6 AC soft magnetic testing of a nanocrystalline alloy magnetic core and its preparation process is provided for the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] A nanocrystalline alloy magnetic core and its preparation process, comprising the following preparation steps:

[0031] S1. Preparation of the master alloy:

[0032] S11. Use 81% pure iron, 1.2% pure copper, 9.3% ferrosilicon and 8.5% ferroboron as raw materials, and perform ultrasonic cleaning on the raw materials to remove surface dirt and then dry them.

[0033] S12, then placed under an internal pressure of 3×10 -3 In a vacuum melting furnace of Pa, the alloy is repeatedly melted 5 times to obtain a master alloy with uniform composition.

[0034] S2. The master alloy is wound to obtain the magnetic core;

[0035] S3. Vacuum heat treatment of the magnetic core: The magnetic core is wound with copper strips inside and outside in a spiral shape, and the thickness of a single layer of copper strip is 0.1 mm. Then it is placed in a tube furnace and nitrogen gas is introduced. The temperature is then raised to 500℃ at 10℃ / min and held for 15 min. The temperature is then raised to 540℃ at 1℃ / min and held for 50 min. When the temperature is cooled to 180℃, it is taken out of the furnace to obtain a nanocrystalline alloy magnetic core.

[0036] S4. Place the nanocrystalline alloy magnetic core in an 8% iron-based phosphide passivation solution and immerse it at room temperature for 100 minutes; then clean it with anhydrous ethanol and dry it in a drying oven at 50°C for 40 minutes.

[0037] S5. Immerse the passivated nanocrystalline alloy core in an organosilicon curing agent, then reduce the air pressure to 0.01 MPa, let it stand until no more bubbles emerge from the surface, then restore atmospheric pressure. Finally, remove the nanocrystalline alloy core and dry it in a 9°C drying oven for 1.5 hours.

[0038] Example 2

[0039] A nanocrystalline alloy magnetic core and its preparation process, comprising the following preparation steps:

[0040] S1. Preparation of the master alloy:

[0041] S11. Use 83% pure iron, 1.0% pure copper, 10% ferrosilicon and 6% ferroboron as raw materials, and perform ultrasonic cleaning on the raw materials to remove surface dirt and then dry them.

[0042] S12, then placed under an internal pressure of 4×10 -3 In a vacuum melting furnace of Pa, the alloy is repeatedly melted 6 times to obtain a master alloy with uniform composition.

[0043] S2. The master alloy is wound to obtain the magnetic core;

[0044] S3. Vacuum heat treatment of the magnetic core: The magnetic core is wound with copper strips inside and outside in a spiral shape, and the thickness of a single layer of copper strip is 0.2 mm. Then it is placed in a tube furnace and nitrogen gas is introduced. The temperature is then raised to 505℃ at 10℃ / min and held for 18 min. The temperature is then raised to 545℃ at 1℃ / min and held for 55 min. When the temperature is lowered to 190℃, it is taken out of the furnace to obtain a nanocrystalline alloy magnetic core.

[0045] S4. Place the nanocrystalline alloy magnetic core in an 8% iron-based phosphide passivation solution and immerse it at room temperature for 110 minutes; then clean it with anhydrous ethanol and dry it in a drying oven at 55°C for 50 minutes.

[0046] S5. Immerse the passivated nanocrystalline alloy core in an organosilicon curing agent, then reduce the air pressure to 0.02MPa, let it stand until no more bubbles emerge from the surface, then restore atmospheric pressure. Finally, remove the nanocrystalline alloy core and dry it in a 95℃ drying oven for 2 hours.

[0047] Example 3

[0048] A nanocrystalline alloy magnetic core and its preparation process, comprising the following preparation steps:

[0049] S1. Preparation of the master alloy:

[0050] S11. Use 85% pure iron, 0.8% pure copper, 8.7% ferrosilicon and 5.5% ferroboron as raw materials, and perform ultrasonic cleaning on the raw materials to remove surface dirt and then dry them.

[0051] S12, then placed under an internal pressure of 5×10 -3 In a vacuum melting furnace of Pa, the alloy is repeatedly melted 6 times to obtain a master alloy with uniform composition.

[0052] S2. The master alloy is wound to obtain the magnetic core;

[0053] S3. Vacuum heat treatment of the magnetic core: The magnetic core is wound with copper strips inside and outside in a spiral shape, and the thickness of a single layer of copper strip is 0.3mm. Then it is placed in a tube furnace and nitrogen gas is introduced. The temperature is then raised to 510℃ at 10℃ / min and held for 20min. The temperature is then raised to 550℃ at 1℃ / min and held for 60min. When the temperature is lowered to 200℃, it is taken out of the furnace to obtain a nanocrystalline alloy magnetic core.

[0054] S4. Place the nanocrystalline alloy magnetic core in an 8% iron-based phosphide passivation solution and immerse it at room temperature for 120 minutes; then clean it with anhydrous ethanol and dry it in a drying oven at 60°C for 60 minutes.

[0055] S5. The passivated nanocrystalline alloy core is immersed in polyurethane curing agent, then the air pressure is reduced to 0.03MPa, left to stand until no more bubbles emerge from the surface, then atmospheric pressure is restored, and finally the nanocrystalline alloy core is taken out and dried in a drying oven at 100℃ for 2 hours.

[0056] Comparative Example 1

[0057] A nanocrystalline alloy magnetic core and its preparation process, comprising the following preparation steps:

[0058] S1. Preparation of the master alloy:

[0059] S11. Use 81% pure iron, 1.2% pure copper, 9.3% ferrosilicon and 8.5% ferroboron as raw materials, and perform ultrasonic cleaning on the raw materials to remove surface dirt and then dry them.

[0060] S12, then placed under an internal pressure of 3×10 -3 In a vacuum melting furnace of Pa, the alloy is repeatedly melted 5 times to obtain a master alloy with uniform composition.

[0061] S2. The master alloy is wound to obtain the magnetic core;

[0062] S3. Vacuum heat treatment of the magnetic core: Place the magnetic core in a tube furnace and introduce nitrogen gas. Then, heat it to 500°C at 10°C / min and hold it for 15 min. Then, heat it to 540°C at 1°C / min and hold it for 50 min. When the temperature drops to 180°C, remove it from the furnace to obtain a nanocrystalline alloy magnetic core.

[0063] The current-voltage characteristic test of the magnetic core: The Shanghai Hengtong HT35 iron core measuring instrument was used to measure the current-voltage characteristic of the annealed magnetic core, i.e., the U-1 curve; the experimental parameters were: power frequency 50Hz, single-turn AC magnetization; the specific operation method was: power on and preheat for 5 minutes, adjust the measuring instrument range according to the size of the magnetic core, then place the magnetic core with the protective box directly on the iron core measuring instrument, adjust the current value, and record the output electromotive force U.

[0064] Thermal stability analysis: The analysis was performed using a NETZSCH-C404 differential scanning calorimeter (DSC). The specific experimental parameters were as follows: heating rate of 0.60℃ / s, Pt crucible, sample weight of 10-20mg, temperature range of 500-1050K, and experimental conditions: vacuum argon gas.

[0065] like Figure 2 As shown, with the increase of temperature, two exothermic peaks appear, corresponding to two different crystallization processes. The first crystallization peak corresponds to the α-Fe(Si) phase, and the precipitation of the α-Fe(Si) phase is beneficial to improving the soft magnetic properties of the strip. The second crystallization exothermic peak corresponds to the secondary phase Fe2B, and the precipitation of Fe2B will cause the ferromagnetism to change to paramagnetism, destroy the spontaneous magnetic properties, and reduce the magnetic properties. Figure 2 China T X1 This corresponds to the start of the first crystallization, where a soft magnetic phase precipitates. (T) p1 The first exothermic peak appears at this time, and the crystallization rate reaches its maximum value, after which grain growth becomes the dominant process; T x2 At the start of the second crystallization, the secondary Fe2B phase precipitates; at T X1 To T x2 Within this relatively wide temperature range, only the ferromagnetic phase precipitates, ensuring the formation of an amorphous-nanocrystalline dual-phase structure after heat treatment without the precipitation of a secondary phase. Therefore, the temperature during heat treatment must not exceed T. x2( 973K).

[0066] like Figure 3 As shown, the average size of the precipitated grains on the free surface is larger than that on the roller-attached surface. Compared with Comparative Example 1, copper-assisted annealing in Example 1 helps to reduce the size of the precipitated grains and improve their uniformity, which is beneficial to improving the uniformity of grains on both the free surface and the roller-attached surface.

[0067] like Figure 4 As shown, in Examples 1-3, the induced electromotive force is significantly increased under different excitation currents compared to Comparative Example 1.

[0068] like Figure 5 As shown, compared to Examples 1-3, Comparative Example 1 shows a deeper oxidation color and a more severe degree of oxidation, which leads to a continuous deterioration of magnetic properties; the brittleness test θ range continuously decreases, meaning that the better the core toughness, the less the core is affected by external forces, and the more stable the performance.

[0069] like Figure 6 As shown, compared to Comparative Example 1, the losses in Examples 1-3 are as low as 0.04 KW / m. 3 Both saturation permeability and coercivity are significantly improved.

[0070] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0071] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0072] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for preparing a nanocrystalline alloy magnetic core, characterized in that, The preparation steps include the following: S1. Preparation of the master alloy: S11. Pure iron, pure copper, ferrosilicon and ferroboron are used as raw materials. The raw materials are ultrasonically cleaned to remove surface dirt and then dried. S12. Then place it in a vacuum melting furnace and repeatedly melt it to obtain a master alloy with uniform composition. S2. The master alloy is wound to obtain the magnetic core; S3. Vacuum heat treatment of the magnetic core: Place the magnetic core in a tube furnace and introduce nitrogen gas. Then heat it to 500-510℃ at 10℃ / min and hold it for 15-20min. Then heat it to 540-550℃ at 1℃ / min and hold it for 50-60min. When the temperature drops to 180-200℃, remove it from the furnace to obtain a nanocrystalline alloy magnetic core. It is made from the following components by weight percentage: 81%–85% pure iron, 0.8%–1.2% pure copper, 8%–10% ferrosilicon, and 5.5%–8.5% ferroboron. The preparation process of the nanocrystalline alloy magnetic core also includes: S4, placing the nanocrystalline alloy magnetic core in a passivation solution and immersing it at room temperature for 100-120 minutes; then immersing and cleaning it with anhydrous ethanol, and then placing it in a drying oven at a temperature of 50-60℃ for 40-60 minutes. The passivation solution is an iron-based phosphide passivation solution, and it is diluted to an 8% solution before use; In step S3, during the heat treatment process, copper strips are wound around the inside and outside of the magnetic core in a spiral shape, and the thickness of a single layer of copper strip is 0.1 to 0.3 mm.

2. The preparation process of a nanocrystalline alloy magnetic core according to claim 1, characterized in that: The preparation process of the nanocrystalline alloy magnetic core also includes: S5, immersing the passivated nanocrystalline alloy magnetic core in a curing agent, then evacuating the air pressure to 0.01-0.03 MPa, letting it stand until no more bubbles emerge from the surface, then restoring the atmospheric pressure, and finally taking out the nanocrystalline alloy magnetic core and drying it in a drying oven at 90-100℃ for 1.5-2 hours.

3. The preparation process of a nanocrystalline alloy magnetic core according to claim 2, characterized in that: The curing agent is selected from either silicone curing agents or polyurethane curing agents.

4. The preparation process of a nanocrystalline alloy magnetic core according to claim 1, characterized in that: In step S12, the internal pressure of the vacuum melting furnace is 3 × 10⁻⁶. -3 ~5×10 -3 Pa, the number of smelting times is 5 to 6.

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