Anti-DC iron core and heat treatment process thereof

Abstract

The invention relates to the technical field of anti-direct-current iron cores, and provides an anti-direct-current iron core and a heat treatment process thereof. A heat treatment process of an anti-direct-current iron core comprises the following steps that S1, an amorphous strip is wound into an amorphous iron core, oxidation heat treatment is conducted after vacuum heat treatment is conducted, and the heat-treated amorphous iron core is obtained; s2, winding the nanocrystalline strip into a nanocrystalline iron core, performing vacuum heat treatment, and then performing magnetizing heat treatment to obtain a heat-treated nanocrystalline iron core; and S3, the heat-treated nanocrystalline iron core is sleeved with the heat-treated amorphous iron core, and the anti-direct-current iron core is formed. According to the technical scheme, the problem that the metering precision and the operation reliability of the electric meter are poor under the scene containing harmonic waves and a direct-current bias magnetic field due to the large direct-current component of the iron core in the related technology is solved.

Description

Technical Field

[0001] This invention relates to the field of DC-resistant iron core technology, specifically to a DC-resistant iron core and its heat treatment process. Background Technology

[0002] Electrical electronic devices widely used in households, such as switching power supplies and frequency converters, generate non-sinusoidal currents during operation, which may contain DC components. When these currents pass through the current transformer system of an electricity meter, they can cause DC bias magnetization in the transformer core. Under normal circumstances, the transformer core needs to remain within its linear operating range to ensure a precise ratio between the primary and secondary currents. However, the intrusion of DC components disrupts this linearity, causing the secondary output current signal to fail to accurately reflect the actual primary current, leading to metering errors. Furthermore, if a DC component exists in the primary winding of the transformer, the magnetic flux will continuously increase until saturation. In saturation, the primary winding current will be entirely used to maintain the core excitation, causing the secondary output current to return to zero, failing to reflect the magnitude of the primary current and resulting in meter reading deviations. Simultaneously, after core saturation, the excitation current increases exponentially, causing abnormal temperature rise in the transformer. Prolonged overheating can accelerate the aging of the transformer's insulation materials and even lead to short-circuit faults, seriously affecting the normal operation of the meter and posing safety hazards. To solve these problems, a DC-resistant core is needed. Summary of the Invention

[0003] This invention proposes an anti-DC iron core and its heat treatment process, which solves the problem in related technologies that the large DC component of the iron core leads to poor metering accuracy and operational reliability of the meter in scenarios with harmonics and DC bias.

[0004] The technical solution of the present invention is as follows: This invention proposes a heat treatment process for DC-resistant iron cores, comprising the following steps: S1. The amorphous ribbon is wound into an amorphous iron core, and after vacuum heat treatment, it is subjected to oxidation heat treatment to obtain a heat-treated amorphous iron core. S2. The nanocrystalline strip is wound into a nanocrystalline iron core, and after vacuum heat treatment, it is subjected to magnetic heat treatment to obtain a heat-treated nanocrystalline iron core. S3. The heat-treated nanocrystalline iron core is fitted inside the heat-treated amorphous iron core to form the DC-resistant iron core; In step S1, the vacuum heat treatment includes three stages: the first stage, heating from room temperature to 232~238℃ and holding for 55~65 min; the second stage, heating from 232~238℃ to 317~323℃ and holding for 75~85 min; and the third stage, heating from 317~323℃ to 430~436℃ and holding for 480~490 min, followed by cooling. The oxidation heat treatment involves heating from room temperature to 200~206℃, holding at that temperature for 475~485 minutes, and then cooling.

[0005] In the heat treatment process of the DC-resistant iron core of this invention, unlike the existing technology that uses a single material or other suboptimal combination to make the DC-resistant iron core, this invention uses a nanocrystalline iron core inside an amorphous iron core. The amorphous iron core has the characteristics of low magnetic permeability but high saturation magnetic induction intensity, while the nanocrystalline iron core has the characteristics of high magnetic permeability but low saturation magnetic induction intensity. When there is no DC in the detection circuit, the nanocrystalline is not saturated, and its magnetic permeability is much higher than that of the amorphous iron core. At this time, the nanocrystalline iron core mainly plays the role of signal transmission. When there is DC in the detection circuit, the saturation magnetic permeability of the nanocrystalline is much lower than that of the amorphous iron core. At this time, the amorphous iron core mainly plays the role of signal transmission. The nanocrystalline iron core and the amorphous iron core work together, so that the DC-resistant iron core can efficiently process AC signals and significantly reduce the negative impact of DC components in complex AC-DC mixed magnetic field environments.

[0006] In the heat treatment process of the DC-resistant iron core of the present invention, the first stage of vacuum heat treatment in step S1 can be heated from room temperature to 232°C, 233°C, 234°C, 235°C, 236°C, 237°C, or 238°C.

[0007] In the heat treatment process of the DC-resistant iron core of the present invention, the second stage of vacuum heat treatment in step S1 can be heated from 232~238℃ to 317℃, 318℃, 319℃, 320℃, 321℃, 322℃, and 323℃.

[0008] In the heat treatment process of the DC-resistant iron core of the present invention, the third stage of vacuum heat treatment in step S1 can be heated from 317~323℃ to 430℃, 431℃, 432℃, 433℃, 434℃, 435℃, and 436℃.

[0009] In the heat treatment process of the DC-resistant iron core of the present invention, the holding time of the first stage of vacuum heat treatment in step S1 can be 55min, 56min, 57min, 58min, 59min, 60min, 61min, 62min, 63min, 64min, or 65min.

[0010] In the heat treatment process of the DC-resistant iron core of the present invention, the holding time of the second stage of vacuum heat treatment in step S1 can be 75 min, 76 min, 77 min, 78 min, 79 min, 80 min, 81 min, 82 min, 83 min, 84 min, or 85 min.

[0011] In the heat treatment process of the DC-resistant iron core of the present invention, the holding time of the third stage of vacuum heat treatment in step S1 can be 480 min, 481 min, 482 min, 483 min, 484 min, 485 min, 486 min, 487 min, 489 min, or 490 min.

[0012] In the heat treatment process of the DC-resistant iron core of the present invention, the oxidation heat treatment can be carried out by raising the temperature from room temperature to 200℃, 201℃, 202℃, 203℃, 204℃, 205℃, and 206℃, and the holding time can be 475min, 476min, 477min, 478min, 479min, 480min, 481min, 482min, 483min, 484min, and 485min.

[0013] As a further technical solution, oxygen is introduced during the oxidation heat treatment process, and the flow rate of the oxygen is 15~16L / min.

[0014] As a further technical solution, in step S1, the heating time of the first stage, the second stage, and the third stage is each 100~120min independently; The heating time for the oxidation heat treatment is 100~120 min.

[0015] In the heat treatment process of the DC-resistant iron core of the present invention, the heating time of the first stage, the second stage and the third stage can be 100 min, 105 min, 110 min, 115 min and 120 min respectively.

[0016] As a further technical solution, in step S2, the vacuum heat treatment includes four stages: the first stage, heating from room temperature to 297~303℃ and holding for 80~100 min; the second stage, heating from 297~303℃ to 417~423℃ and holding for 80~100 min; the third stage, heating from 417~423℃ to 477~483℃ and holding for 110~130 min; and the fourth stage, heating from 477~483℃ to 582~588℃ and holding for 80~100 min, followed by cooling.

[0017] In the heat treatment process of the DC-resistant iron core of the present invention, the first stage of vacuum heat treatment in step S2 can be heated from room temperature to 297°C, 298°C, 299°C, 300°C, 301°C, 302°C, or 303°C.

[0018] In the heat treatment process of the DC-resistant iron core of the present invention, the second stage of vacuum heat treatment in step S2 can be heated from 297~303℃ to 417℃, 418℃, 419℃, 420℃, 421℃, 422℃, and 423℃.

[0019] In the heat treatment process of the DC-resistant iron core of the present invention, the third stage of vacuum heat treatment in step S2 can be heated from 417~423℃ to 477℃, 478℃, 479℃, 480℃, 481℃, 482℃, and 483℃.

[0020] In the heat treatment process of the DC-resistant iron core of the present invention, the fourth stage of vacuum heat treatment in step S2 can be heated from 477~483℃ to 582℃, 583℃, 584℃, 585℃, 586℃, 587℃, and 588℃.

[0021] As a further technical solution, in step S2, the heating time of the first stage is 20~30min; The heating time for the second and third stages is 50-60 minutes each independently; The heating time for the fourth stage is 65-75 minutes.

[0022] As a further technical solution, in step S2, the cooling process during the vacuum heat treatment specifically involves first naturally cooling to 200°C and then air cooling.

[0023] As a further technical solution, the magnetization heat treatment involves raising the temperature from room temperature to 320°C, holding it at that temperature for 80-90 minutes, and then cooling it. During the heat preservation process, a transverse magnetic field is activated, and the strength of the transverse magnetic field is 1350GS. Before the magnetization heat treatment, the vacuum is evacuated to -0.08MPa to -0.1MPa, and nitrogen gas is introduced until the pressure is 0.05 to 0.06MPa.

[0024] As a further technical solution, in steps S1 and S2, the vacuum degree of the vacuum heat treatment is independently -0.08MPa to -0.1MPa.

[0025] As a further technical solution, the composition of the amorphous iron core is Fe. 78 Si9B 12.5 Ga 0.5 The outer diameter is 27±0.5mm, the inner diameter is 21±0.5mm, the height is 12±0.3mm, and the weight is 16±0.3g; The nanocrystalline iron core is composed of Fe. 73.5 Cu1Nb3Si 13.5 B9 has an outer diameter of 20.9±0.5mm, an inner diameter of 19±0.5mm, a height of 12.0±0.3mm, and a weight of 5±0.3g.

[0026] The present invention also proposes an anti-DC iron core, which is obtained by the aforementioned heat treatment process.

[0027] The working principle and beneficial effects of this invention are as follows: 1. This invention takes into account the influence of the internal structure and surface oxide film of the amorphous iron core on the DC component. Through a vacuum heat treatment process that prioritizes maintaining the amorphous structure, ensuring the size of atomic clusters, and finally guaranteeing sufficient atomic arrangement, and by controlling the formation of a dense oxide film on the surface of the amorphous iron core, it solves the problem of poor metering accuracy and operational reliability in scenarios with harmonics and DC bias caused by the large DC component of the iron core. Specifically, in the first stage of vacuum heat treatment, the temperature is raised from room temperature to 232~238℃ and held for 55~65 minutes, balancing the furnace temperature. This avoids excessive heat treatment that could damage the amorphous structure of the iron core due to excessively high temperatures or long holding times; and it also prevents uneven microstructure caused by excessively low temperatures or short holding times, which could affect the electromagnetic properties of the amorphous iron core. In the second stage, the temperature is increased from 232~238℃ to 317~323℃ and held for 75~85 minutes. This avoids the impact of excessively high temperatures or prolonged holding times on the uniformity of magnetic domains due to abnormal atomic cluster sizes, while also preventing the failure to release internal stress and weakening the magnetic stability of the amorphous core due to excessively low temperatures or short holding times. In the third stage, when the temperature is increased to 430~436℃, the atoms of the amorphous core can be fully arranged, significantly improving the magnetic permeability stability of the amorphous core and effectively reducing the negative impact of DC components on magnetic permeability and overall performance. The subsequent oxidation heat treatment involves heating to 200~206℃ and holding for 475~485 minutes. Under these conditions, a dense oxide film is formed on the surface of the amorphous core. The oxide film, by changing its surface magnetic properties, impedes and regulates the DC magnetic field, weakening the interference of DC components on the internal magnetic properties of the core. The oxidation heat treatment process of the present invention not only avoids the problem of excessively thick oxide film due to excessively high temperature or excessively long time, which affects the magnetic permeability of the iron core; but also avoids the problem of insufficient oxide film due to excessively low temperature or excessively short time, which cannot effectively block DC magnetic field.

[0028] 2. The DC-resistant iron core of the present invention can meet the following requirements: In terms of low current sensitivity, when a 3mA current passes through the primary side, the induced electromotive force of the iron core is not less than 0.035mV; in terms of dynamic inductance stability, when the bias current is 5A, the inductance value is controlled in the range of 57~61μH, and when the bias current is 3A, the inductance value is stable in the range of 58~63μH. Even under the condition of a low bias DC of 0.2A, the inductance value can still maintain a stable range of 60.5~66.5μH. Therefore, the iron core of the present invention can maintain the stability of magnetic permeability under complex current environment, effectively suppress the saturation effect caused by DC component, thereby ensuring the metering accuracy and operational reliability of the meter in scenarios containing harmonics and DC bias. Attached Figure Description

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0030] Figure 1 This is a schematic diagram of the structure of the DC-resistant iron core obtained in Embodiment 1 of the present invention. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1 Iron-based amorphous ribbon is wound into an amorphous iron core with the composition Fe. 78 Si9B 12.5 Ga 0.5 It has an outer diameter of 27mm, an inner diameter of 21mm, a height of 12mm, and a weight of 16g. Iron-based nanocrystalline ribbons are wound into nanocrystalline iron cores with the composition Fe. 73.5 Cu1Nb3Si 13.5 B9 has an outer diameter of 20.9 mm, an inner diameter of 19 mm, a height of 12 mm, and a weight of 5 g. The amorphous iron core was placed in a vacuum furnace and evacuated to -0.1 MPa. The temperature was increased from room temperature to 235°C over 120 min and held for 60 min. The temperature was then increased from 235°C to 320°C over 120 min and held for 80 min. The temperature was then increased from 320°C to 433°C over 120 min and held for 485 min. The temperature was then rapidly reduced to room temperature by air cooling. The amorphous iron core was then placed in an oxidation heat treatment furnace and oxygen was introduced at a flow rate of 15 L / min. The temperature was increased from room temperature to 203°C over 120 min and held for 480 min. The nanocrystalline iron core was placed in a vacuum furnace and evacuated to -0.1 MPa. The temperature was then increased from room temperature to 300°C over 30 minutes and held for 90 minutes. Next, the temperature was increased from 300°C to 420°C over 60 minutes and held for 90 minutes. Finally, the temperature was increased from 420°C to 480°C over 60 minutes and held for 120 minutes. The temperature was then increased from 480°C to 585°C over 75 minutes and held for 90 minutes. After naturally cooling to 200°C, the core was removed from the furnace and cooled to room temperature by a fan. The nanocrystalline iron core was placed in a magnetic heat treatment furnace, evacuated to -0.1 MPa, and 99.99% pure nitrogen was introduced to a pressure of 0.05 MPa. The temperature was raised from room temperature to 320℃ in 30 minutes and held for 90 minutes. At the beginning of the holding period, the transverse magnetic field was turned on with a strength of 1350 GS. After the holding period, the temperature was lowered to 300℃ using a cooling fan, the furnace door was opened, and the temperature was lowered to 80℃ by blowing an electric fan for 10 minutes. The core was then removed from the furnace and cooled to room temperature by blowing an electric fan. A nanocrystalline iron core is fitted inside an amorphous iron core to form a DC-resistant iron core. See the specific structure below. Figure 1 .

[0033] Twenty randomly selected DC-resistant iron core samples were used to measure the induced electromotive force at 3mA using an HT36 iron core measuring instrument. The inductance values ​​were measured using a ZX1373X-12A bridge bias current integrated tester at a frequency of 1K, a voltage of 1V, a 10-turn coil, a 30Ω internal resistance, and bias DC values ​​of 5A, 3A, and 0.2A. The test results are shown in Table 1.

[0034] Table 1. Test results of induced electromotive force and inductance of DC-resistant iron core in Example 1

[0035] As shown in Table 1, the induced electromotive force of the DC-resistant iron core prepared in Example 1 at 3mA is ≥0.035mV, with an average value of 0.0424mV. When the bias current is 5A, the inductance value is LS=57~61μH; when the bias current is 3A, the inductance value is LS=58~63μH; and when the bias current is 0.2A, the inductance value is LS=60.5~66.5μH. The pass rate of randomly selected samples reached 95%, demonstrating consistent DC-resistant inductance.

[0036] Example 2 Iron-based amorphous ribbon is wound into an amorphous iron core with the composition Fe. 78 Si9B 12.5 Ga 0.5 It has an outer diameter of 27mm, an inner diameter of 21mm, a height of 12mm, and a weight of 16g. Iron-based nanocrystalline ribbons are wound into nanocrystalline iron cores with the composition Fe. 73.5 Cu1Nb3Si 13.5 B9 has an outer diameter of 20.9 mm, an inner diameter of 19 mm, a height of 12 mm, and a weight of 5 g. The amorphous iron core was placed in a vacuum furnace and evacuated to -0.1 MPa. The temperature was increased from room temperature to 232°C over 120 min and held for 55 min. The temperature was then increased from 232°C to 317°C over 120 min and held for 75 min. The temperature was then increased from 317°C to 430°C over 120 min and held for 480 min. The temperature was then rapidly cooled to room temperature by air cooling. The amorphous iron core was then placed in an oxidation heat treatment furnace and oxygen was introduced at a flow rate of 15 L / min. The temperature was increased from room temperature to 200°C over 120 min and held for 475 min. The nanocrystalline iron core was placed in a vacuum furnace and evacuated to -0.1 MPa. The temperature was then increased from room temperature to 297°C over 20 minutes and held for 80 minutes. Next, the temperature was increased from 297°C to 417°C over 50 minutes and held for 80 minutes. Finally, the temperature was increased from 417°C to 477°C over 50 minutes and held for 110 minutes. The temperature was then increased from 477°C to 582°C over 65 minutes and held for 80 minutes. After naturally cooling to 200°C, the core was removed from the furnace and cooled to room temperature by a fan. The nanocrystalline iron core was placed in a magnetic heat treatment furnace, evacuated to -0.08 MPa, and 99.99% pure nitrogen was introduced to a pressure of 0.06 MPa. The temperature was raised from room temperature to 320℃ in 30 minutes and held for 80 minutes. At the beginning of the holding period, the transverse magnetic field was turned on with a strength of 1350 GS. After the holding period, the temperature was lowered to 300℃ using a cooling fan, the furnace door was opened, and the temperature was lowered to 80℃ by blowing an electric fan for 10 minutes. The core was then removed from the furnace and cooled to room temperature by blowing an electric fan. A nanocrystalline iron core is fitted inside an amorphous iron core to form a DC-resistant iron core; Twenty randomly selected DC-resistant iron core samples were used to measure the induced electromotive force at 3mA using an HT36 iron core measuring instrument. The inductance values ​​were measured using a ZX1373X-12A bridge bias current integrated tester at a frequency of 1K, a voltage of 1V, a 10-turn coil, a 30Ω internal resistance, and bias DC values ​​of 5A, 3A, and 0.2A. The test results are shown in Table 2.

[0037] Table 2. Test results of induced electromotive force and inductance of DC-resistant iron core in Example 2

[0038] Table 2 shows that the induced electromotive force of the DC-resistant iron core prepared in Example 2 at 3mA is ≥0.035mV, with an average value of 0.0424mV. When the bias current is 5A, the inductance value is LS=57~61μH; when the bias current is 3A, the inductance value is LS=58~63μH; and when the bias current is 0.2A, the inductance value is LS=60.5~66.5μH. The pass rate of randomly selected samples reached 95%, demonstrating consistent DC-resistant inductance.

[0039] Example 3 Iron-based amorphous ribbon is wound into an amorphous iron core with the composition Fe. 78 Si9B 12.5 Ga 0.5 It has an outer diameter of 27mm, an inner diameter of 21mm, a height of 12mm, and a weight of 16g. Iron-based nanocrystalline ribbons are wound into nanocrystalline iron cores with the composition Fe. 73.5 Cu1Nb3Si 13.5 B9 has an outer diameter of 20.9 mm, an inner diameter of 19 mm, a height of 12 mm, and a weight of 5 g. The amorphous iron core was placed in a vacuum furnace and evacuated to -0.1 MPa. The temperature was increased from room temperature to 238°C over 120 min and held for 65 min. The temperature was then increased from 238°C to 323°C over 120 min and held for 85 min. The temperature was then increased from 323°C to 436°C over 120 min and held for 490 min. The temperature was then rapidly cooled to room temperature by air cooling. The amorphous iron core was then placed in an oxidation heat treatment furnace and oxygen was introduced at a flow rate of 16 L / min. The temperature was increased from room temperature to 206°C over 120 min and held for 485 min. The nanocrystalline iron core was placed in a vacuum furnace and evacuated to -0.1 MPa. The temperature was then increased from room temperature to 303°C over 30 minutes and held for 100 minutes. Next, the temperature was increased from 303°C to 423°C over 60 minutes and held for 100 minutes. Finally, the temperature was increased from 423°C to 483°C over 60 minutes and held for 120 minutes. Then, the temperature was increased from 483°C to 588°C over 75 minutes and held for 100 minutes. After naturally cooling to 200°C, the core was removed from the furnace and cooled to room temperature by a fan. The nanocrystalline iron core was placed in a magnetic heat treatment furnace, evacuated to -0.1 MPa, and 99.99% pure nitrogen was introduced to a pressure of 0.05 MPa. The temperature was raised from room temperature to 320℃ in 30 minutes and held for 100 minutes. At the beginning of the holding period, the transverse magnetic field was turned on with a strength of 1350 GS. After the holding period, the temperature was lowered to 300℃ using a cooling fan, the furnace door was opened, and the temperature was lowered to 80℃ by blowing an electric fan for 10 minutes. The furnace was then removed and the temperature was lowered to room temperature by blowing an electric fan. A nanocrystalline iron core is fitted inside an amorphous iron core to form a DC-resistant iron core; Twenty randomly selected DC-resistant iron core samples were used to measure the induced electromotive force at 3mA using an HT36 iron core measuring instrument. The inductance values ​​were measured using a ZX1373X-12A bridge bias current integrated tester at a frequency of 1K, a voltage of 1V, a 10-turn coil, a 30Ω internal resistance, and bias DC values ​​of 5A, 3A, and 0.2A. The test results are shown in Table 3.

[0040] Table 3. Test results of induced electromotive force and inductance of DC-resistant iron core in Example 3

[0041] Table 3 shows that the induced electromotive force of the DC-resistant iron core prepared in Example 3 at 3mA is ≥0.035mV, with an average value of 0.0424mV. When the bias current is 5A, the inductance value is LS=57~61μH; when the bias current is 3A, the inductance value is LS=58~63μH; and when the bias current is 0.2A, the inductance value is LS=60.5~66.5μH. The pass rate of randomly selected samples reached 95%, demonstrating consistent DC-resistant inductance.

[0042] Comparative Example 1 The only difference between this comparative example and Example 1 is that the amorphous iron core was placed in a vacuum furnace and evacuated to -0.1 MPa. The temperature was then increased from room temperature to 235°C over 120 minutes and held for 60 minutes. Next, the temperature was increased from 235°C to 320°C over 120 minutes and held for 80 minutes. Finally, the temperature was increased from 320°C to 450°C over 120 minutes and held for 485 minutes. The core was then rapidly cooled to room temperature. The amorphous iron core was then placed in an oxidation heat treatment furnace, and oxygen was introduced at a flow rate of 15 L / min. The temperature was increased from room temperature to 203°C over 120 minutes and held for 480 minutes. Twenty randomly selected DC-resistant iron core samples were used to measure the induced electromotive force at 3 mA using an HT36 iron core measuring instrument. The inductance was measured using a ZX1373X-12A bridge bias current integrated tester at a frequency of 1 kHz, voltage of 1 V, 10 turns of coil, 30 Ω internal resistance, and DC bias values ​​of 5 A, 3 A, and 0.2 A. The test results are shown in Table 4.

[0043] Table 4 Test results of induced electromotive force and inductance of the DC-resistant iron core in Comparative Example 1

[0044] As shown in Table 4, the induced electromotive force of the DC-resistant iron core prepared in Comparative Example 1 at 3mA is ≥0.035mV. When the bias current is 5A, the inductance value is LS=43~47μH. When the bias current is 3A, the inductance value is LS=44~52μH. When the bias current is 0.2A, the inductance value is LS=51~57μH, which does not meet the requirements.

[0045] Comparative Example 2 The only difference between this comparative example and Example 1 is that the amorphous iron core was placed in a vacuum furnace and evacuated to -0.1 MPa. The temperature was then increased from room temperature to 235°C over 120 minutes and held for 60 minutes. Next, the temperature was increased from 235°C to 320°C over 120 minutes and held for 80 minutes. Finally, the temperature was increased from 320°C to 380°C over 120 minutes and held for 485 minutes. The core was then rapidly cooled to room temperature. The amorphous iron core was then placed in an oxidation heat treatment furnace, and oxygen was introduced at a flow rate of 15 L / min. The temperature was increased from room temperature to 203°C over 120 minutes and held for 480 minutes. Twenty randomly selected DC-resistant iron core samples were used to measure the induced electromotive force at 3 mA using an HT36 iron core measuring instrument. The inductance was measured using a ZX1373X-12A bridge bias current integrated tester at a frequency of 1 kHz, voltage of 1 V, 10 turns of coil, 30 Ω internal resistance, and DC bias of 5 A, 3 A, and 0.2 A. The test results are shown in Table 5.

[0046] Table 5 Test results of induced electromotive force and inductance of the DC-resistant iron core in Comparative Example 2

[0047] As shown in Table 5, the induced electromotive force of the DC-resistant iron core prepared in Comparative Example 2 at 3mA is ≥0.035mV. When the bias current is 5A, the inductance value is LS=41~47μH. When the bias current is 3A, the inductance value is LS=44~48μH. When the bias current is 0.2A, the inductance value is LS=41~50μH, which does not meet the requirements.

[0048] Comparative Example 3 The only difference between this comparative example and Example 1 is that the amorphous iron core was placed in a vacuum furnace and evacuated to -0.1 MPa. The temperature was then increased from room temperature to 235°C over 120 minutes and held for 60 minutes. Next, the temperature was increased from 235°C to 320°C over 120 minutes and held for 80 minutes. Finally, the temperature was increased from 320°C to 433°C over 120 minutes and held for 485 minutes. The core was then rapidly cooled to room temperature. The amorphous iron core was then placed in an oxidation heat treatment furnace, and oxygen was introduced at a flow rate of 15 L / min. The temperature was increased from room temperature to 203°C over 120 minutes and held for 400 minutes. Twenty randomly selected DC-resistant iron core samples were used to measure the induced electromotive force at 3 mA using an HT36 iron core measuring instrument. The inductance was measured using a ZX1373X-12A bridge bias current integrated tester at a frequency of 1 kHz, voltage of 1 V, 10 turns of coil, 30 Ω internal resistance, and DC bias values ​​of 5 A, 3 A, and 0.2 A. The test results are shown in Table 6.

[0049] Table 6 Test results of induced electromotive force and inductance of the DC-resistant iron core in Comparative Example 3

[0050] As shown in Table 6, the induced electromotive force of the DC-resistant iron core prepared in Comparative Example 3 at 3mA is ≥0.035mV. When the bias current is 5A, 3A and 0.2A, only 6 inductance values ​​are qualified, and the pass rate is only 30%.

[0051] Comparative Example 4 The only difference between this comparative example and Example 1 is that the amorphous iron core was placed in a vacuum furnace and evacuated to -0.1 MPa. The temperature was then increased from room temperature to 235°C over 120 minutes and held for 60 minutes. Next, the temperature was increased from 235°C to 320°C over 120 minutes and held for 80 minutes. Finally, the temperature was increased from 320°C to 433°C over 120 minutes and held for 485 minutes. The core was then rapidly cooled to room temperature. The amorphous iron core was then placed in an oxidation heat treatment furnace, and oxygen was introduced at a flow rate of 15 L / min. The temperature was increased from room temperature to 203°C over 120 minutes and held for 550 minutes. Twenty randomly selected DC-resistant iron core samples were used. The induced electromotive force at 3 mA was measured using an HT36 iron core measuring instrument. The inductance was measured using a ZX1373X-12A bridge bias current integrated tester at a frequency of 1 kHz, voltage of 1 V, 10 turns of coil, 30 Ω internal resistance, and DC bias of 5 A, 3 A, and 0.2 A. The test results are shown in Table 7.

[0052] Table 7 Test results of induced electromotive force and inductance of the DC-resistant iron core in Comparative Example 4

[0053] As shown in Table 7, the induced electromotive force of the DC-resistant iron core prepared in Comparative Example 4 at 3mA is ≥0.035mV. When the bias current is 5A, 3A and 0.2A, only 4 of the inductance values ​​are qualified, and the pass rate is only 20%.

[0054] Comparative Example 5 The only difference between this comparative example and Example 1 is that the amorphous iron core was placed in a vacuum furnace and evacuated to -0.1 MPa. The temperature was then increased from room temperature to 235°C over 120 minutes and held for 60 minutes. Next, the temperature was increased from 235°C to 320°C over 120 minutes and held for 80 minutes. Finally, the temperature was increased from 320°C to 433°C over 120 minutes and held for 485 minutes. The core was then rapidly cooled to room temperature. The amorphous iron core was then placed in an oxidation heat treatment furnace, and oxygen was introduced at a flow rate of 15 L / min. The temperature was increased from room temperature to 250°C over 120 minutes and held for 480 minutes. Twenty randomly selected DC-resistant iron core samples were used to measure the induced electromotive force at 3 mA using an HT36 iron core measuring instrument. The inductance was measured using a ZX1373X-12A bridge bias current integrated tester at a frequency of 1 kHz, voltage of 1 V, 10 turns of coil, 30 Ω internal resistance, and DC bias values ​​of 5 A, 3 A, and 0.2 A. The test results are shown in Table 8.

[0055] Table 8 Test results of induced electromotive force and inductance of the DC-resistant iron core in Comparative Example 5

[0056] As shown in Table 8, the induced electromotive force of the DC-resistant iron core prepared in Comparative Example 5 at 3mA is ≥0.035mV. When the bias current is 5A, 3A, and 0.2A, the inductance value is unqualified and does not meet the requirements.

[0057] Comparative Example 6 The only difference between this comparative example and Example 1 is that the amorphous iron core was placed in a vacuum furnace and evacuated to -0.1 MPa. The temperature was then increased from room temperature to 235°C over 120 minutes and held for 60 minutes. Next, the temperature was increased from 235°C to 320°C over 120 minutes and held for 80 minutes. Finally, the temperature was increased from 320°C to 433°C over 120 minutes and held for 485 minutes. The core was then rapidly cooled to room temperature. The amorphous iron core was then placed in an oxidation heat treatment furnace, and oxygen was introduced at a flow rate of 15 L / min. The temperature was increased from room temperature to 180°C over 120 minutes and held for 480 minutes. Twenty randomly selected DC-resistant iron core samples were used to measure the induced electromotive force at 3 mA using an HT36 iron core measuring instrument. The inductance was measured using a ZX1373X-12A bridge bias current integrated tester at a frequency of 1 kHz, voltage of 1 V, 10 turns of coil, 30 Ω internal resistance, and DC bias of 5 A, 3 A, and 0.2 A. The test results are shown in Table 9.

[0058] Table 9 Test results of induced electromotive force and inductance of the DC-resistant iron core in Comparative Example 6

[0059] As shown in Table 9, the induced electromotive force of the DC-resistant iron core prepared in Comparative Example 6 at 3mA is ≥0.035mV. When the bias current is 5A, 3A, and 0.2A, the inductance value is unqualified and does not meet the requirements.

[0060] Comparative Example 7 The only difference between this comparative example and Example 1 is that the amorphous iron core was placed in a vacuum furnace and evacuated to -0.1 MPa. The temperature was then increased from room temperature to 235°C over 120 minutes and held for 60 minutes. Next, the temperature was increased from 235°C to 320°C over 120 minutes and held for 80 minutes. Finally, the temperature was increased from 320°C to 433°C over 120 minutes and held for 485 minutes. The core was then rapidly cooled to room temperature. The amorphous iron core was then placed in an oxidation heat treatment furnace, and oxygen was introduced at a flow rate of 15 L / min. The temperature was increased from room temperature to 203°C over 120 minutes and held for 450 minutes. Twenty randomly selected DC-resistant iron core samples were used to measure the induced electromotive force at 3 mA using an HT36 iron core measuring instrument. The inductance was measured using a ZX1373X-12A bridge bias current integrated tester at a frequency of 1 kHz, voltage of 1 V, 10 turns of coil, 30 Ω internal resistance, and DC bias values ​​of 5 A, 3 A, and 0.2 A. The test results are shown in Table 10.

[0061] Table 10 Test results of induced electromotive force and inductance of the DC-resistant iron core in Comparative Example 7

[0062] As shown in Table 10, the induced electromotive force of the DC-resistant iron core prepared in Comparative Example 7 at 3mA is ≥0.035mV. When the bias current is 5A, 3A, and 0.2A, the inductance value is unqualified and does not meet the requirements.

[0063] Comparative Example 8 The only difference between this comparative example and Example 1 is that the outer diameter of the nanocrystalline iron core is 27 mm, the inner diameter is 21 mm, the height is 12 mm, and the weight is 19 g. The amorphous iron core has an outer diameter of 20.9 mm, an inner diameter of 19 mm, a height of 12 mm, and a weight of 4.21 g; a nanocrystalline iron core is fitted over the amorphous iron core. Twenty randomly selected DC-resistant iron core samples were tested using an HT36 iron core measuring instrument to measure the induced electromotive force at 3 mA. The test results are shown in Table 11.

[0064] Table 11 Test results of induced electromotive force of the DC-resistant iron core in Comparative Example 8

[0065] As shown in Table 11, the DC-resistant iron core induced electromotive force prepared in Comparative Example 8 is unqualified and does not meet the requirements.

[0066] Comparative Example 9 This comparative DC-resistant iron core only used the amorphous iron core from Example 1, and the heat treatment of the amorphous iron core from Example 1 was performed. Twenty randomly selected DC-resistant iron core samples were tested using an HT36 iron core measuring instrument to measure the induced electromotive force at 3mA. The test results are shown in Table 12.

[0067] Table 12 Test results of induced electromotive force of the DC-resistant iron core in Comparative Example 9

[0068] As shown in Table 12, the DC core induced electromotive force prepared in Comparative Example 9 is unqualified and does not meet the requirements.

[0069] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A heat treatment process for an anti-DC iron core, characterized in that, Includes the following steps: S1. The amorphous ribbon is wound into an amorphous iron core, and after vacuum heat treatment, it is subjected to oxidation heat treatment to obtain a heat-treated amorphous iron core. S2. The nanocrystalline strip is wound into a nanocrystalline iron core, and after vacuum heat treatment, it is subjected to magnetic heat treatment to obtain a heat-treated nanocrystalline iron core. S3. The heat-treated nanocrystalline iron core is fitted inside the heat-treated amorphous iron core to form the DC-resistant iron core; In step S1, the vacuum heat treatment includes three stages: the first stage, heating from room temperature to 232~238℃ and holding for 55~65 min; the second stage, heating from 232~238℃ to 317~323℃ and holding for 75~85 min; and the third stage, heating from 317~323℃ to 430~436℃ and holding for 480~490 min, followed by cooling. The oxidation heat treatment involves heating from room temperature to 200~206℃, holding at that temperature for 475~485 minutes, and then cooling.

2. The heat treatment process for an anti-DC iron core according to claim 1, characterized in that, Oxygen is introduced during the oxidative heat treatment process, and the flow rate of the oxygen is 15~16 L / min.

3. The heat treatment process for an anti-DC iron core according to claim 1, characterized in that, In step S1, the heating time for the first stage, the second stage, and the third stage is each 100~120min independently; The heating time for the oxidation heat treatment is 100~120 min.

4. The heat treatment process for an anti-DC iron core according to claim 1, characterized in that, In step S2, the vacuum heat treatment includes four stages: the first stage, heating from room temperature to 297~303℃ and holding for 80~100 min; the second stage, heating from 297~303℃ to 417~423℃ and holding for 80~100 min; the third stage, heating from 417~423℃ to 477~483℃ and holding for 110~130 min; and the fourth stage, heating from 477~483℃ to 582~588℃, holding for 80~100 min, and then cooling.

5. The heat treatment process for an anti-DC iron core according to claim 4, characterized in that, In step S2, the heating time in the first stage is 20~30 minutes; The heating time for the second and third stages is 50-60 minutes each independently; The heating time for the fourth stage is 65-75 minutes.

6. The heat treatment process for an anti-DC iron core according to claim 4, characterized in that, In step S2, the cooling process during the vacuum heat treatment specifically involves first naturally cooling to 200°C and then air cooling.

7. The heat treatment process for an anti-DC iron core according to claim 1, characterized in that, The magnetic heat treatment involves raising the temperature from room temperature to 320°C, holding it at that temperature for 80-90 minutes, and then cooling it. During the heat preservation process, a transverse magnetic field is activated, and the strength of the transverse magnetic field is 1350GS. Before the magnetization heat treatment, the vacuum is evacuated to -0.08MPa to -0.1MPa, and nitrogen gas is introduced until the pressure is 0.05 to 0.06MPa.

8. The heat treatment process for an anti-DC iron core according to claim 1, characterized in that, In steps S1 and S2, the vacuum degree of the vacuum heat treatment is independently -0.08MPa to -0.1MPa.

9. The heat treatment process for an anti-DC iron core according to claim 1, characterized in that, The amorphous iron core is composed of Fe. 78 Si9B 12.5 Ga 0.5 The outer diameter is 27±0.5mm, the inner diameter is 21±0.5mm, the height is 12±0.3mm, and the weight is 16±0.3g; The nanocrystalline iron core is composed of Fe. 73.5 Cu1Nb3Si 13.5 B9 has an outer diameter of 20.9±0.5mm, an inner diameter of 19±0.5mm, a height of 12.0±0.3mm, and a weight of 5±0.3g.

10. A DC-resistant iron core, characterized in that, It is obtained by using the heat treatment process described in any one of claims 1 to 9.

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