Nano-crystal magnetic core magnetic field heat treatment process capable of firstly cooling and then preserving heat

Abstract

The nanocrystalline magnetic core magnetic field heat treatment process comprises the following steps that S1, after a nanocrystalline magnetic core is wound, an integrated magnetic pulling process is prepared, or after annealing, a secondary magnetic pulling process is prepared; s2, a transverse magnetic field heat treatment process is set, heat preservation is conducted at a high temperature section firstly, and it is guaranteed that the temperature of a furnace body and the temperature of a magnetic core are uniform; s3, applying a transverse magnetic field when the transverse magnetic field heat treatment starts to cool from the set temperature, stopping cooling and preserving heat for a period of time when the temperature is reduced to a set heat preservation section, and cooling to the tapping temperature after heat preservation is finished; and S4, finally, the magnetic core subjected to transverse magnetic heat treatment is normally transferred to the rear-section assembling, detecting, packaging and shipping procedures. According to the magnetic field heat treatment process disclosed by the invention, compared with the conventional secondary heat preservation magnetic pulling and cooling magnetic pulling, the direct current bias resistance of the magnetic core is remarkably improved on the premise that the magnetic conductivity is not reduced, so that the redundancy of the magnetic core to a working environment is improved.

Description

Technical Field

[0001] The present application relates to the technical field of heat treatment of nanocrystalline magnetic cores, and in particular to a magnetic field heat treatment process of nanocrystalline magnetic cores that first cools down the temperature and then keeps the temperature. Background Art

[0002] Currently, the current and magnetic field in magnetic devices are affected by many factors, which causes the actual current waveform during operation to deviate from the designed waveform, resulting in a DC bias component. The bias magnetic field brought by this bias current makes the magnetic core more easily saturated. The magnetic permeability of the saturated magnetic core drops sharply, which will fail and cause device failure. Therefore, the core's ability to resist DC bias is an important indicator for measuring the core's performance and reliability.

[0003] In the related art, the commonly used secondary magnetic field heat treatment is to heat the annealed magnetic core to a single target temperature and keep it warm, and turn on the magnetic field while keeping it warm; at the same time, the commonly used cooling and pulling magnetization is to turn on the magnetic field while the magnetic core is cooling down until it cools down; thus, in the related art, the single temperature insulation magnetic field heat treatment or cooling magnetic field heat treatment method can increase the saturation current, but in order to improve the core's anti-bias ability, it is almost inevitable that the core's magnetic permeability becomes lower, thereby reducing the performance of the core. Summary of the invention

[0004] The purpose of the present application is to provide a nanocrystalline magnetic core magnetic field heat treatment process that first cools down and then keeps warm, so as to solve the problem in the related art that, although the saturation current can be increased by a single temperature holding magnetic field heat treatment or a cooling magnetic field heat treatment method, in order to improve the anti-bias ability of the magnetic core, it is almost inevitable that the magnetic permeability of the magnetic core becomes lower, thereby reducing the performance of the magnetic core.

[0005] The present application provides a nanocrystalline magnetic core magnetic field heat treatment process of first cooling and then keeping warm, which adopts the following technical solutions: A nanocrystalline magnetic core magnetic field heat treatment process of first cooling and then keeping warm comprises the following steps: S1: After winding the nanocrystalline magnetic core, prepare for an integrated magnetizing process or after annealing, prepare for a secondary magnetizing process; S2: Transverse magnetic field heat treatment process setting, first keep warm at a higher temperature to ensure uniform temperature of the furnace body and the magnetic core; S3: When the transverse magnetic field heat treatment starts to cool down from the set temperature, the transverse magnetic field is applied. When the temperature drops to the set insulation section, the temperature is stopped and kept for a period of time. After the insulation is completed, the temperature is lowered to the furnace exit temperature. S4: Finally, the magnetic core after transverse magnetic heat treatment is normally transferred to the back-end assembly, testing, packaging and shipment process.

[0006] Furthermore, in step S3, a transverse magnetic field is applied from the start of cooling to the heat preservation stage and the exit from the furnace.

[0007] Furthermore, the temperature is from 510°C to 480°C as a cooling stage.

[0008] Furthermore, the temperature is 480° C. and the temperature is kept for 30 minutes as the heat preservation stage.

[0009] Furthermore, the performance of the annealed magnetic core obtained by the transverse magnetic heat treatment process of cooling at 520°C and maintaining at 470°C is better than that of the magnetic core obtained by the ordinary 510°C secondary transverse magnetic heat treatment process.

[0010] Furthermore, the nanocrystalline magnetic core obtained by a magnetic field heat treatment process of cooling at 510°C and maintaining at 450°C has better 10kHz inductance and DC bias resistance than the magnetic core obtained by a conventional 510°C integrated cooling magnetic field heat treatment process.

[0011] Compared with the prior art, the beneficial effects of this application are: The present application adopts a magnetic field heat treatment process of first cooling down from high temperature and then keeping the temperature. The magnetic field heat treatment process applies a transverse magnetic field when the temperature of the magnetic core starts to cool down from a high temperature, stops cooling when the temperature drops to a middle temperature, keeps the temperature for a period of time, and then cools down to the furnace-out temperature and takes it out of the furnace. The transverse magnetic field is always applied from the beginning of cooling to the keeping temperature to the furnace-out. In this way, the magnetic field heat treatment process can significantly improve the core's ability to resist DC bias without reducing the magnetic permeability, thereby improving the redundancy of the core to the working environment.

[0012] At the same time, the magnetic core of the present application can make the orientation of the magnetic domains relative to the working magnetic field more reasonable through high-temperature cooling-mid-section insulation transverse magnetic field heat treatment, and improve the anisotropy without reducing the initial magnetic permeability, so that it can work in a larger magnetic field, and the ability to resist DC bias is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a flow chart of the magnetic field heat treatment process of the nanocrystalline magnetic core of the embodiment of the present application, which involves first cooling down and then keeping the temperature.

[0014] Figure 2 This is a typical heating curve of the cooling-heat-maintaining magnetic field heat treatment process in the embodiment of the present application.

[0015] Figure 3 It is a schematic diagram comparing the magnetic core performance of the cooling-insulating magnetic field heat treatment in the embodiment of the present application and the ordinary magnetic field heat treatment process.

[0016] Figure 4 It is a schematic table comparing the core performance of the cooling-insulating magnetic field heat treatment and the integrated magnetic field heat treatment process in the embodiment of the present application. DETAILED DESCRIPTION

[0017] The following is combined with Figures 1-4 This application is described in further detail.

[0018] The present application discloses a nanocrystalline magnetic core magnetic field heat treatment process of first cooling and then keeping warm, referring to Figure 1 In this embodiment, the nanocrystalline magnetic core magnetic field heat treatment process includes the following steps: S1: After winding the nanocrystalline magnetic core, prepare for the integrated magnetizing process or after annealing, prepare for the secondary magnetizing process.

[0019] S2: Transverse magnetic field heat treatment process setting, first keep warm at a higher temperature to ensure uniform temperature of the furnace body and the magnetic core; specifically, refer to Figure 2 In this embodiment, when heated to 120 minutes, the furnace body reaches a maximum temperature of 560°C; then when the temperature is 560°C, insulation begins, and the insulation time is between 120 minutes and 240 minutes, that is, the insulation time is 120 minutes, which can ensure that the temperature of the furnace body and the magnetic core is uniform, and the nanocrystals are uniformly crystallized.

[0020] S3: Transverse magnetic field heat treatment: When the temperature starts to drop from the set temperature, a transverse magnetic field is applied. When the temperature drops to the set insulation section, the temperature is stopped and kept for a period of time. After the insulation is completed, the temperature is dropped to the furnace exit temperature. Specifically, due to the extremely high magnetic permeability of the nanocrystalline magnetic core material, the magnetic ring will be saturated under a very small magnetic field, so transverse magnetic field heat treatment is required to increase the working magnetic field range.

[0021] Therefore, in step S3, a transverse magnetic field is always applied from the beginning of cooling to the insulation stage and the furnace exit. In this way, the magnetic core is heat treated with a high-temperature transverse magnetic field, which can make the magnetic domain deviate from the direction of the working magnetic field, improve the anisotropy, enable it to work in a larger magnetic field, and improve the ability to resist DC bias.

[0022] More specifically, refer to Figure 2 In this embodiment, the cooling-holding magnetic field heat treatment of the present application divides the magnetic field heat treatment into two processes, namely, the cooling process and the holding process. Among them, between 280min-285min, that is, within the 5min time, the temperature is from 510℃ to 480℃ for the cooling process; then, between 285min-315min, the temperature is 480℃ and the holding is 30min for the holding process.

[0023] This segmented magnetization process can make the distribution of magnetic domain directions in each energy state more reasonable, make the transformation speed of magnetic domains more constant during the magnetization process, and improve the anti-bias capability without reducing the magnetic permeability.

[0024] In addition, since the temperature of magnetic field heat treatment can be used to adjust the performance of the magnetic core, the higher the temperature of magnetic field heat treatment, the lower the initial magnetic permeability of the magnetic core. The magnetic cores in different application scenarios require different magnetic permeabilities, so the temperature can be adjusted to produce products that meet different needs.

[0025] There are multiple heat sources in the heat treatment furnace cavity. During the temperature change process, the temperature in the furnace is not consistent everywhere and will deviate from the set temperature to a certain extent. Figure 2 When the temperature drops from the crystallization temperature to the heat treatment start temperature, adding this period of insulation can give the furnace temperature a uniform buffer time, make the actual temperature close to the set temperature, and reduce the temperature difference in various places in the furnace chamber.

[0026] Therefore, refer to Figure 2 In this embodiment, before the cooling-keeping magnetic field heat treatment is started, the temperature is cooled from 560°C to 510°C between 240min-250min, that is, within 10min, and then kept at 510°C between 250min-280min, that is, within 30min; the main purpose of such treatment is to ensure the accuracy of the starting temperature of the magnetic field heat treatment.

[0027] In this way, the temperature drops from 510℃, which is the time when the magnetic field heat treatment is started. The cooling and heat preservation in this section is the process to improve product performance. The temperature drops from a high temperature here, making the distribution of magnetic domain direction more reasonable, avoiding excessive high temperature pulling magnetism that causes the domain to deviate from the working magnetic field and reduce the magnetic permeability, while improving the DC bias resistance.

[0028] S4: Finally, the magnetic core after transverse magnetic heat treatment is normally transferred to the back-end assembly, testing, packaging and shipment process.

[0029] Therefore, the present application adopts a magnetic field heat treatment process of first cooling down from high temperature and then keeping the temperature. The magnetic field heat treatment process applies a transverse magnetic field when the temperature of the magnetic core starts to cool down from a high temperature, and stops cooling when the temperature drops to a middle temperature, keeps the temperature for a period of time, and then cools down to the furnace temperature and takes it out of the furnace. The transverse magnetic field is always applied from the beginning of cooling to the keeping temperature to the furnace taking out. In this way, the magnetic field heat treatment process can significantly improve the core's ability to resist DC bias without reducing the magnetic permeability compared to the previous secondary insulation magnetization and cooling magnetization, thereby improving the redundancy of the core to the working environment.

[0030] At the same time, in the previous process, the magnetic permeability and the ability to resist DC bias are often inversely proportional, and it is not easy to improve the performance of both at the same time. The magnetic core of the present application can make the magnetic domain orientation more reasonable through special transverse magnetic field heat treatment, without reducing the initial magnetic permeability, and improve the anisotropy, so that it can work in a larger magnetic field, and the ability to resist DC bias is improved. Please refer toFigure 3 In this embodiment, the performance of the annealed magnetic core is compared using a 520℃ cooling-470℃ insulation transverse magnetic heat treatment process and a common 510℃ secondary transverse magnetic insulation heat treatment process. Specifically, the annealed magnetic core uses a magnetic core product with an outer diameter of 60, an inner diameter of 50.5, and a height of 25.

[0031] Specifically, in Figure 3 It can be seen that the magnetic induction intensity of the samples of these two processes increases with the increase of the magnetic field intensity. Under the same magnetic field intensity, the magnetic induction intensity of the process described in this application is generally higher than that of the ordinary process, and the increase in magnetic induction intensity is greater. The greater the magnetic induction intensity, the better the product performance.

[0032] At the same time, the magnetic permeability of the magnetic core decreases with the increase of magnetic field strength. The samples of the process used in this application are still higher than those of the ordinary process at each magnetic field strength, and the higher the magnetic permeability, the better the performance. The performance of the annealed magnetic core obtained by the transverse magnetic heat treatment process of 520℃ cooling-470℃ insulation is better than that of the ordinary 510℃ secondary transverse magnetic insulation heat treatment process.

[0033] In addition, refer to Figure 4 In this embodiment, the 10kHz inductive impedance DC bias performance of the nanocrystalline magnetic core is compared using a common 510℃ integrated cooling magnetic field heat treatment process and a 510℃ cooling-450℃ insulation magnetic field heat treatment process. Specifically, the nanocrystalline magnetic core uses a magnetic core product with an outer diameter of 50, an inner diameter of 32, and a height of 20.

[0034] Specifically, in Figure 4 It can be seen that at a frequency of 10kHz, the nanocrystalline magnetic core obtained by the magnetic field heat treatment process of 510℃ cooling and 450℃ insulation has better 10kHz inductance and DC bias resistance than the magnetic core obtained by the ordinary 510℃ integrated cooling magnetic field heat treatment process, and the improvement effect is obvious.

[0035] In this way, through the practical cooling-insulation process, it is revealed that the key to anti-bias lies in regulating the distribution of domains under various energies and directions, which brings new improvement ideas to the traditional magnetic pulling process.

[0036] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A nanocrystalline magnetic core magnetic field heat treatment process of first cooling and then keeping warm, characterized in that: The following steps are involved: S1: After winding the nanocrystalline magnetic core, prepare for an integrated magnetizing process or after annealing, prepare for a secondary magnetizing process; S2: Transverse magnetic field heat treatment process setting, first keep warm at a higher temperature to ensure uniform temperature of the furnace body and the magnetic core; S3: When the transverse magnetic field heat treatment starts to cool down from the set temperature, the transverse magnetic field is applied. When the temperature drops to the set insulation section, the temperature is stopped and kept for a period of time. After the insulation is completed, the temperature is lowered to the furnace exit temperature. S4: Finally, the magnetic core after transverse magnetic heat treatment is normally transferred to the back-end assembly, testing, packaging and shipment process.

2. The nanocrystalline magnetic core magnetic field heat treatment process of first cooling and then keeping warm according to claim 1 is characterized in that: In step S3, a transverse magnetic field is applied from the start of temperature reduction to the heat preservation stage and the furnace exit.

3. The nanocrystalline magnetic core magnetic field heat treatment process of first cooling and then keeping warm according to claim 1 is characterized in that: The temperature is from 510℃-480℃ for the cooling stage.

4. The nanocrystalline magnetic core magnetic field heat treatment process of first cooling and then keeping warm according to claim 1 is characterized in that: The temperature is 480°C and is kept warm for 30 minutes.

5. The nanocrystalline magnetic core magnetic field heat treatment process of first cooling and then keeping warm according to claim 1 is characterized in that: The performance of the annealed magnetic core obtained by the transverse magnetic heat treatment process of cooling at 520℃ and keeping at 470℃ is better than that of the magnetic core obtained by the ordinary 510℃ secondary transverse magnetic heat treatment process.

6. The nanocrystalline magnetic core magnetic field heat treatment process of first cooling and then keeping warm according to claim 1 is characterized in that: The nanocrystalline magnetic core is heat treated in a magnetic field from 510℃ to 450℃, and has better 10kHz inductance and DC bias resistance than the core heat treated in a conventional 510℃ integrated cooling magnetic field.

Images