A heat treatment method for an anti-DC bias iron-based special-shaped nanocrystalline magnetic core

Abstract

The present invention discloses a heat treatment method for an anti - DC - bias iron - based special - shaped nanocrystalline magnetic core, which comprises the following steps: S1: Put the nanocrystalline material into a corresponding mold and press it to form a special - shaped nanocrystalline magnetic core; S2: Put the mold into a heating furnace, pre - evacuate it to - 0.1 MPa, inject nitrogen, and then carry out three - stage heating and heat preservation. When starting the second - stage heat preservation, apply a transverse magnetic field of 800 - 1800 GS to the nanocrystalline alloy magnetic core; S3: After the heat preservation at the highest temperature is completed, cool it with the heating furnace, cool it through a certain cooling method and rate. After cooling to the specified temperature, take it out of the furnace and quickly cool it to room temperature, and finally take out the special - shaped nanocrystalline magnetic core from the mold. By optimizing the heat treatment and transverse magnetic field process parameters, the present invention enables the special - shaped magnetic core to obtain a more sufficient crystallization and magnetic field treatment effect, obtains a higher magnetic permeability at 100 KHz, and further obtains a better magnetic permeability under the conditions of a 100 KHz frequency and an externally applied DC bias of 1.5 A, demonstrating good anti - DC - bias characteristics.

Description

Technical Field

[0001] The present invention belongs to the field of heat treatment processes for nanocrystalline magnetic cores, and particularly relates to a heat treatment method for a DC bias-resistant iron-based special-shaped nanocrystalline magnetic core. Background Art

[0002] A nanocrystalline magnetic core is a ring-shaped device obtained by heat-treating an amorphous alloy strip to form nanocrystalline grains inside the strip and endowing it with certain magnetic permeability. Generally, it includes processing steps such as base material melting, strip spraying, winding into a ring, and heat treatment. Among them, heat treatment is crucial for obtaining a high-performance nanocrystalline magnetic core.

[0003] Currently, the traditional heat treatment method is to heat-treat an amorphous alloy material above the crystallization temperature to make it into an amorphous-nanocrystalline duplex structure, thereby obtaining a nanocrystalline magnetic core. However, in the existing heat treatment process, the grain growth rate is relatively fast, and the grain size difference at different positions is relatively large, with poor annealing uniformity. The initial magnetic permeability of the obtained nanocrystalline magnetic core is relatively low, and the coercivity is relatively large, which is not conducive to obtaining a nanocrystalline iron core with excellent magnetic properties.

[0004] Chinese Patent CN 113832309 A proposes a vacuum annealing heat treatment process for a special-shaped nanocrystalline magnetic core. Aiming at the problem that the magnetic permeability of the special-shaped nanocrystalline magnetic core is affected during the heat treatment process in the existing process, a vacuum annealing heat treatment process method of placing the special-shaped nanocrystalline magnetic core in a dielectric mold and pre-pumping the vacuum atmosphere for protection is proposed. However, the special-shaped nanocrystalline magnetic core obtained by this treatment method does not have excellent saturation resistance and DC bias resistance characteristics; although Chinese Patent CN 109192431 A proposes a DC bias-resistant iron-based nanocrystalline alloy magnetic core and a preparation method, the magnetic permeability of the nanocrystalline magnetic core at a frequency of 100 KHz is relatively low. In addition, the existing molds for storing special-shaped nanocrystalline magnetic cores also have a complex structure and are inconvenient to install and remove. Summary of the Invention

[0005] In view of the above problems, the present invention provides a heat treatment method for a DC bias-resistant iron-based special-shaped nanocrystalline magnetic core. Through the improvement of the heat treatment process, good magnetic field treatment effects and excellent DC bias resistance characteristics are obtained, and technical problems such as the special-shaped nanocrystalline magnetic core obtained by the traditional heat treatment process not having excellent saturation resistance and DC bias resistance characteristics, and the inconvenient use of the mold are solved.

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

[0007] A heat treatment method for a DC bias-resistant iron-based special-shaped nanocrystalline magnetic core, comprising the following steps:

[0008] S1: Place the nanocrystalline material into the corresponding mold and press it to form a special-shaped nanocrystalline magnetic core. The mold includes an inner mold and an outer mold;

[0009] S2: Place the mold into a heating furnace, pre-vacuum it to -0.1 MPa, inject nitrogen to achieve cyclic atmosphere protection during the heat treatment of the magnetic core, and then perform three-stage heating-up and heat preservation. When starting the second-stage heat preservation, apply a transverse magnetic field of 800 - 1800 GS to the nanocrystalline alloy magnetic core.

[0010] S3: After the heat preservation at the highest temperature is completed, cool with the heating furnace, cool through a certain cooling method and rate. After cooling to the specified temperature, take out of the furnace and quickly cool to room temperature. Finally, take out the special-shaped nanocrystalline magnetic core from the mold.

[0011] As a further technical solution, the mold includes an inner module and an outer module. The special-shaped nanocrystalline magnetic core is sleeved on the inner module, and the outer module is sleeved on the special-shaped nanocrystalline magnetic core. The wall thickness of the inner module and the outer module is 1 - 2 mm, and through holes are opened on the four walls. The mold material is made of non-magnetic stainless steel. One end of the long side of the outer module is a movable side, and a detachable baffle is provided to facilitate the loading and unloading of the nanocrystalline magnetic core.

[0012] As a further technical solution, in the step S1, the special-shaped nanocrystalline magnetic core includes any one of a rectangular magnetic core and a racetrack-shaped magnetic core.

[0013] As a further technical solution, in the three-stage heating-up and heat preservation process in the step S2, the first stage is to preheat the nanocrystalline magnetic core to eliminate stress, the second stage is to shape the special-shaped nanocrystalline magnetic core, and the third stage is the crystallization process of the nanocrystalline magnetic core.

[0014] As a further technical solution, when the first stage is the process of preheating the nanocrystalline magnetic core to eliminate stress, specifically: the annealing furnace is heated from room temperature to 380 - 400 °C at a heating rate of 4 - 5 °C / min and is kept at 380 - 400 °C for 60 - 90 min.

[0015] As a further technical solution, when the second stage is the process of shaping the special-shaped nanocrystalline magnetic core, specifically: the annealing furnace is heated to 460 - 480 °C at a heating rate of 1 - 2 °C / min and is kept at 460 - 480 °C for 60 - 90 min.

[0016] As a further technical solution, when the third stage is the crystallization process of the nanocrystalline magnetic core, specifically: the annealing furnace is heated to 550 - 575 °C at a heating rate of 1 - 2 °C / min and is kept at 550 - 575 °C for 100 - 120 min.

[0017] As a further technical solution, when the annealing furnace temperature enters the heat preservation section of 460 - 480 °C in the step S2, apply a transverse magnetic field of 800 - 1800 GS.

[0018] As a further technical solution, after the heat preservation at the highest temperature of 550-575°C in step S3 ends, the furnace starts to cool down, and a transverse magnetic field of 800-1800 GS is continuously applied during the cooling process.

[0019] As a further technical solution, the annealing furnace in step S3 cools to the specified discharging temperature of 240°C; the certain cooling rate in step S3 is 2-3°C / min.

[0020] The technical solution of the present invention has the following beneficial effects:

[0021] 1. By segmentally controlling the heating temperature, heating time, and heat preservation time, and optimizing the transverse magnetic field intensity, time, and magnetic field application temperature, the special-shaped magnetic core can be more fully crystallized and magnetically treated, enabling the special-shaped magnetic core to obtain a higher magnetic permeability at 100 KHz. Furthermore, under the conditions of a 100 KHz frequency and an externally applied 1.5 A DC bias, a better magnetic permeability can be obtained, providing better anti-saturation ability and anti-DC bias characteristics for the special-shaped iron-based nanocrystalline magnetic core in the design of high-frequency filter inductors for new energy vehicles;

[0022] 2. The mold for storing the iron-based special-shaped nanocrystalline magnetic core of the present invention has a simple structure and is convenient for installation and disassembly. Description of the Drawings

[0023] Figure 1 is the process flow chart of the heat treatment process of the anti-DC bias iron-based special-shaped nanocrystalline magnetic core of the present invention;

[0024] Figure 2 is the structural schematic diagram of the mold for storing the iron-based special-shaped nanocrystalline magnetic core of the present invention;

[0025] In the figure: 1. Inner module; 2. Outer module; 3. Nanocrystalline magnetic core; 4. Baffle. Detailed Embodiments

[0026] The technical solutions of the present invention will be clearly and completely described below through embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] As Figure 1 shown, a heat treatment method for an anti-DC bias iron-based special-shaped nanocrystalline magnetic core of the present invention includes the following steps:

[0028] S1: Put the nanocrystalline material into the corresponding mold and press it to form a special-shaped nanocrystalline magnetic core;

[0029] S2: Place the mold into the heating furnace, pre-evacuate the vacuum to -0.1 MPa, inject nitrogen to achieve the cyclic atmosphere protection during the magnetic core heat treatment process, and then perform three-stage heating and heat preservation. Specifically: the first stage is the preheating and stress relief process of the nanocrystalline magnetic core, and the process is: the annealing furnace is heated from room temperature to 380 - 400 °C at a heating rate of 4 - 5 °C / min and kept at 380 - 400 °C for 60 - 90 min; the second stage is the shaping process of the special-shaped nanocrystalline magnetic core, and the process is: the annealing furnace is heated to 460 - 480 °C at a heating rate of 1 - 2 °C / min and kept at 460 - 480 °C for 60 - 90 min; the third stage is the crystallization process of the nanocrystalline magnetic core, and the process is: the annealing furnace is heated to 550 - 575 °C at a heating rate of 1 - 2 °C / min and kept at 550 - 575 °C for 100 - 120 min. When starting the second-stage heat preservation, apply a transverse magnetic field of 800 - 1800 GS to the nanocrystalline alloy magnetic core;

[0030] S3: After the heat preservation at the highest temperature is completed, cool with the heating furnace, cool at a rate of 2 - 3 °C / min through a certain cooling method, take out of the furnace after cooling to 240 °C and quickly cool to room temperature, and finally take out the special-shaped nanocrystalline magnetic core from the mold.

[0031] It should be noted that the composition ratio of the iron-based nanocrystalline alloy used in the embodiment of the present invention is: calculated by weight percentage: Si 8.5 - 9.0%, B 1.4 - 1.7%, Nb 5.4 - 5.8%, Cu 1.2 - 1.4%, Co 0.3 - 0.8%, and the balance is Fe content and inevitable impurity elements; the thickness of the iron-based nanocrystalline strip is 14 - 18 μm. For other preparation processes in the nanocrystalline magnetic core, such as base material melting, strip spraying, winding into a ring, etc., they all belong to the existing process technologies, and the present invention will not repeat them here.

[0032] The process parameters of the specific embodiments are as follows:

[0033] Example 1

[0034]

[0035] Example 2

[0036]

[0037] Example 3

[0038]

[0039]

[0040] Example 4

[0041]

[0042] Example 5

[0043]

[0044] Comparative Example 1

[0045]

[0046]

[0047] It can be seen from the test results of the above Examples 1-5 that the present invention controls the heating temperature, heating time, and heat preservation time in sections, and optimizes the transverse magnetic field strength, time, and magnetization temperature, so that the special-shaped magnetic core can be more fully crystallized and magnetically treated, enabling the special-shaped magnetic core to obtain a higher magnetic permeability at 100 KHz, and further obtaining a better magnetic permeability under the conditions of a frequency of 100 KHz and an applied DC bias of 1.5 A, demonstrating good DC bias resistance characteristics. In Comparative Example 1, the transverse magnetic field was applied when the temperature was cooled down to 420 °C, and the measured magnetic permeability at 100 KHz and a bias current of 1.5 A was significantly lower. It can be seen that the application process of the transverse magnetic field and the like has a great influence on the DC bias resistance characteristics of the special-shaped magnetic core.

[0048] In addition, the shape of the magnetic core also has many effects on the performance. The heat treatment process of this application is mainly aimed at special-shaped nanocrystalline magnetic cores. Compared with ring-shaped nanocrystalline magnetic cores with regular shapes, it is relatively more difficult to obtain the same magnetic properties, and the process is relatively complex.

Claims

1. A heat treatment method for an anti - DC - bias iron - based special - shaped nanocrystalline magnetic core, characterized in that, It includes the following steps: S1: Place the nanocrystalline material into the corresponding mold and press it to form a special-shaped nanocrystalline magnetic core. The mold includes an inner mold and an outer mold. S2: Place the mold into a heating furnace, pre-vacuum it to -0.1 MPa, inject nitrogen to achieve cyclic atmosphere protection during the heat treatment of the magnetic core, and then perform three-stage heating and holding. When entering the second-stage holding, apply a transverse magnetic field of 800 - 1800 GS to the nanocrystalline alloy magnetic core. S3: After the holding at the highest temperature is completed, cool with the heating furnace, cool through a certain cooling method and rate. After cooling to the specified temperature, take it out of the furnace and quickly cool it to room temperature. Finally, take out the special-shaped nanocrystalline magnetic core from the mold. In the three-stage heating and holding, the first stage is the process of preheating the nanocrystalline magnetic core to eliminate stress, specifically: the annealing furnace heats up from room temperature to 380 - 400 °C at a heating rate of 4 - 5 °C / min and holds at 380 - 400 °C for 60 - 90 min; the second stage is the process of shaping the special-shaped nanocrystalline magnetic core, specifically: the annealing furnace heats up to 460 - 480 °C at a heating rate of 1 - 2 °C / min and holds at 460 - 480 °C for 60 - 90 min; the third stage is the crystallization process of the nanocrystalline magnetic core, specifically: the annealing furnace heats up to 550 - 575 °C at a heating rate of 1 - 2 °C / min and holds at 550 - 575 °C for 100 - 120 min. In step S2, when the temperature of the annealing furnace enters the holding section of 460 - 480 °C, apply a transverse magnetic field of 800 - 1800 GS; in step S3, after the holding at the highest temperature of 550 - 575 °C is completed, start to cool with the furnace, and continuously apply a transverse magnetic field of 800 - 1800 GS during the cooling process. The mold includes an inner module (1) and an outer module (2). The special-shaped nanocrystalline magnetic core (3) is sleeved on the inner module (1), and the outer module (2) is sleeved on the special-shaped nanocrystalline magnetic core (3). The wall thickness of the inner module and the outer module is 1 - 2 mm, and through holes are opened on the four walls. The mold material is made of non-magnetic stainless steel. One end of the long side of the outer module is a movable side, and a detachable baffle (4) is provided to facilitate the loading and unloading of the nanocrystalline magnetic core into and out of the mold.

2. The heat treatment method of an anti-DC bias iron-based special-shaped nanocrystalline magnetic core according to claim 1, characterized in that: In step S1, the special-shaped nanocrystalline magnetic core includes any one of a rectangular magnetic core and a racetrack-shaped magnetic core.

3. The heat treatment method of an anti - DC - bias iron - based special - shaped nanocrystalline magnetic core according to claim 1, characterized in that: In step S3, the annealing furnace cools to the specified furnace-out temperature of 240 °C; in step S3, the cooling rate is 2 - 3 °C / min.

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