Power inductor gradient forming method and device based on high-temperature oil circulation hot pressing

Abstract

The invention provides a power inductor gradient forming method and device based on high-temperature oil circulation hot pressing, and relates to the technical field of inductor preparation. The method comprises the steps that iron-based amorphous alloy powder is obtained, and a mold is heated; feeding the iron-based amorphous alloy powder into a mold cavity of a heated mold, and pressing the iron-based amorphous alloy powder according to preset pressure to obtain a magnetic powder core; and annealing the obtained magnetic powder core to prepare the power inductor. The high-temperature oil circulation system is used for achieving mold global dynamic heat conduction, compared with a resistance rod point heat source mode, temperature gradient fluctuation and inductor magnetic core density deviation are reduced, product Q value stability is improved, and the problem of magnetic domain distortion caused by local overheating is effectively solved; and secondly, a closed oil way heat recovery framework is innovatively adopted, the thermal inertia of the system is reduced, the preheating time is shortened, the heating efficiency is improved, a temperature control algorithm is combined, accurate temperature control is achieved, and comprehensive energy consumption is reduced.

Description

Technical Field

[0001] This invention relates to the field of inductor fabrication technology, and in particular to a method and apparatus for gradient forming of power inductors based on high-temperature oil circulation hot pressing. Background Technology

[0002] Depending on the application scenario, magnetic powder needs to be pressed into magnetic powder cores of different shapes. The pressing methods are mainly divided into two types: cold pressing and hot pressing. Cold pressing introduces greater internal stress, increasing hysteresis loss. Hot pressing has less internal stress and does not require greater pressure, allowing for the production of high-density, high-performance power inductors under low-pressure and high-temperature conditions.

[0003] The performance of magnetic powder cores is closely related to the pressing pressure. On the one hand, to increase the core density and improve the permeability, greater pressure is required for molding. On the other hand, excessive pressure can cause the coating layer on the particle surface to crack, increasing eddy current losses. The molding pressure is related to the hardness of the magnetic powder; generally, the greater the hardness, the greater the molding pressure required. As the pressing pressure increases, the permeability initially increases and then decreases, while the magnetic loss shows the opposite trend. This is mainly because overpressure can cause cracks on the particle surface, damaging the integrity of the insulating layer, reducing the resistivity between particles, and increasing eddy current losses. Furthermore, the greater the pressure, the greater the residual stress, leading to greater hysteresis losses.

[0004] Currently, traditional hot pressing generally uses heating rods for heating. On the one hand, the quality of heating rods varies, which can easily lead to inaccurate temperature control and damage. On the other hand, traditional heating rods have a slow heating rate, low production efficiency, high cost, and cannot achieve gradient molding effects at different temperatures. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a power inductor gradient forming method and apparatus based on high-temperature oil circulation hot pressing, so as to solve the technical problems that the use of heating rods for hot pressing is prone to inaccurate temperature control of heating rods, slow heating rate of heating rods, low production efficiency and high cost.

[0006] This invention provides a method for shaping power inductors based on high-temperature oil circulation hot pressing, comprising:

[0007] Iron-based amorphous alloy powder was obtained and the mold was heated.

[0008] The iron-based amorphous alloy powder is fed into the cavity of a heated mold, and the iron-based amorphous alloy powder is pressed according to a preset pressure to obtain a magnetic powder core.

[0009] The obtained magnetic powder core is annealed to prepare a power inductor.

[0010] In addition, the power inductor gradient forming method based on high-temperature oil circulation hot pressing according to the present invention may also have the following additional technical features:

[0011] Furthermore, in the step of heating the mold: the mold is heated using a gradient heating method, with a heating temperature of 300℃-650℃.

[0012] Furthermore, in the step of heating the mold: when the mold is heated to 300°C, it is held under pressure for 1 second; when the mold is heated to 650°C, it is held under pressure for 2 seconds, so as to perform gradient heating of the mold.

[0013] Furthermore, in the step of heating the mold, the heating medium is high-temperature oil.

[0014] Furthermore, the preset pressure is 800 MPa.

[0015] Furthermore, annealing was carried out in a vacuum environment at a temperature of 450°C for 1 hour.

[0016] Another aspect of the present invention provides a power inductor gradient forming apparatus based on high-temperature oil circulation hot pressing, for implementing the above-mentioned power inductor gradient forming method based on high-temperature oil circulation hot pressing. The apparatus includes a forming mold, the forming mold comprising:

[0017] An upper punch assembly, a lower punch assembly, and a middle die assembly disposed between the upper punch assembly and the lower punch assembly;

[0018] The upper punch assembly includes an upper punch, an upper punch high-temperature oil circulation system, and an upper punch oil supply pipeline and an upper punch oil return pipeline connecting the upper punch and the upper punch high-temperature oil circulation system to form a closed oil circuit. The upper punch is provided with an upper punch oil circuit to connect the upper punch oil supply pipeline and the upper punch oil return pipeline.

[0019] The intermediate mold assembly includes an intermediate mold, an intermediate mold high-temperature oil circulation system, and an intermediate mold oil supply pipeline and an intermediate mold oil return pipeline connecting the intermediate mold and the intermediate mold high-temperature oil circulation system to form a closed oil circuit. The intermediate mold is provided with an intermediate mold oil circuit to connect the intermediate mold oil supply pipeline and the intermediate mold oil return pipeline.

[0020] Both the upper punch and the middle mold are equipped with temperature monitoring devices to control the temperature.

[0021] The aforementioned power inductor gradient molding method and apparatus based on high-temperature oil circulation hot pressing achieves dynamic heat conduction throughout the mold through a high-temperature oil circulation system. Compared with the resistance rod point heat source mode, it reduces temperature gradient fluctuations and inductor core density deviations, improves product Q-value stability, and effectively solves the problem of magnetic domain distortion caused by local overheating. Secondly, it innovatively adopts a closed-loop oil circuit heat recovery architecture, which reduces system thermal inertia, shortens preheating time, improves heating efficiency, and, combined with temperature control algorithms, achieves precise temperature control while reducing overall energy consumption. Attached Figure Description

[0022] Figure 1 This is a flowchart of the power inductor gradient molding method based on high-temperature oil circulation hot pressing in an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the architecture of the power inductor gradient forming device based on high-temperature oil circulation hot pressing in an embodiment of the present invention;

[0024] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0025] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0027] To address the technical problems of inaccurate temperature control and slow heating rate of heating rods in hot pressing, which leads to low production efficiency and high cost, this invention provides a power inductor gradient molding method and apparatus based on high-temperature oil circulation hot pressing. The high-temperature oil circulation system achieves dynamic heat conduction throughout the mold, reducing temperature gradient fluctuations and inductor core density deviations compared to the resistance rod point heat source mode, thus improving the product's Q-value stability and effectively solving the problem of magnetic domain distortion caused by localized overheating. Secondly, the innovative closed-loop oil circuit heat recovery architecture reduces system thermal inertia, shortens preheating time, and improves heating efficiency. Combined with a temperature control algorithm, it achieves precise temperature control and reduces overall energy consumption.

[0028] Specifically, such as Figure 1 As shown, the power inductor gradient molding method based on high-temperature oil circulation hot pressing includes steps S101-S103:

[0029] S101. Obtain iron-based amorphous alloy powder and heat the mold.

[0030] In some optional embodiments, a gradient heating method is used to heat the mold, with high-temperature oil as the heating medium and a heating temperature of 300℃-650℃. Specifically, when the mold is heated to 300℃, the pressure is held for 1 second; when the mold is heated to 650℃, the pressure is held for 2 seconds to perform gradient heating of the mold.

[0031] High-temperature oil is a heat transfer medium used in high-temperature environments, typically in industrial heating systems. It possesses a high boiling point, excellent thermal stability, and high thermal conductivity, enabling long-term stable operation at high temperatures. The addition of antioxidants to high-temperature oil makes it less prone to oxidation or decomposition at high temperatures, further ensuring stable long-term operation and reducing replacement frequency and maintenance costs. Due to its high thermal conductivity, it can quickly and evenly transfer heat to the target object. Simultaneously, high-temperature oil exhibits low volatility at high temperatures, reducing the generation of oil mist and volatile substances, thus lowering environmental pollution.

[0032] A high-temperature oil circulation system enables dynamic heat transfer across the entire mold area, reducing temperature gradient fluctuations by over 80% compared to the point heat source mode using resistance rods. Actual measurement data shows that the inductor core density deviation has been narrowed from ±5% in traditional processes to ±1.2%, and the product's Q-value stability has been improved by 3 times, effectively solving the problem of magnetic domain distortion caused by localized overheating. This improves product characteristics and consistency.

[0033] Compared to existing heating rod technologies, the high-temperature oil medium breaks through the 650℃ limit of resistance heating, enabling gradient hot pressing of novel materials such as nanocrystalline and amorphous alloys. The pressure-temperature coupling control system achieves a 10ms-level dynamic response, providing a new process dimension for the microstructure control of high-frequency inductor devices and meeting the needs of high-frequency application scenarios above 120MHz in 5G base stations.

[0034] S102. The iron-based amorphous alloy powder is fed into the cavity of the heated mold, and the iron-based amorphous alloy powder is pressed according to the preset pressure to obtain a magnetic powder core.

[0035] In some alternative embodiments, the preset pressure is 800 MPa.

[0036] S103. Anneal the obtained magnetic powder core to prepare a power inductor.

[0037] Furthermore, annealing is carried out in a vacuum environment at a temperature of 450℃ for 1 hour.

[0038] like Figure 2As shown, another aspect of the present invention provides a power inductor gradient forming apparatus based on high-temperature oil circulation hot pressing, used to implement the above-mentioned power inductor gradient forming method based on high-temperature oil circulation hot pressing. The apparatus includes a forming mold, which includes an upper punch assembly, a lower punch assembly, and a middle mold assembly disposed between the upper punch assembly and the lower punch assembly. The upper punch assembly includes an upper punch 4, an upper punch high-temperature oil circulation system 1, and an upper punch oil supply pipeline 2 and an upper punch oil return pipeline 6 connecting the upper punch 4 and the upper punch high-temperature oil circulation system 1 to construct a closed oil circuit. An upper punch oil passage 3 is provided to connect the upper punch oil supply line 2 and the upper punch oil return line 6; the middle mold assembly includes a middle mold 10, a middle mold high-temperature oil circulation system 7, and a middle mold oil supply line 8 and a middle mold oil return line 14 connecting the middle mold 10 and the middle mold high-temperature oil circulation system 7 to form a closed oil circuit. The middle mold 10 is provided with a middle mold oil passage 9 to connect the middle mold oil supply line 8 and the middle mold oil return line 14; both the upper punch 4 and the middle mold 10 are provided with temperature monitoring devices to control the temperature; specifically, this includes an upper punch temperature monitoring device 5 and a middle mold temperature monitoring device 13.

[0039] This device innovatively adopts a closed-loop oil circuit heat recovery architecture, reducing the system's thermal inertia to 1 / 4 of that of the electric heating mode and shortening the preheating time by 60%. Specifically, firstly, the high-temperature oil circulation system 1 of the upper punch utilizes high-temperature oil to achieve dynamic heat conduction throughout the mold, transferring heat from the upper punch supply line 2 to the upper punch oil circuit 3, where the upper punch 4 is heated, and then circulated through the upper punch return line 6. Secondly, the high-temperature oil circulation system 7 of the middle mold circulates high-temperature oil from the middle mold supply line 8 to the middle mold oil circuit 9, heating the middle mold 10, lower punch 11, and mandrel 12, and then circulating through the middle mold return line 14. Throughout the circulation process, temperature monitoring equipment controls the temperature, and with the help of a PID adaptive temperature control algorithm, precise temperature control at the ±0.5℃ level is achieved. Furthermore, this device uses metal pipes combined with ceramic fibers for sealing, avoiding the risk of oil leakage. It should be further noted that because high density can be achieved through hot pressing at low pressure, this device can realize a multi-cavity mold solution, not limited to a single cavity mold.

[0040] This application innovatively adopts a closed-loop oil-circuit heat recovery architecture and uses a gradient forming method in the hot pressing process to obtain magnetic powder cores with superior performance. Secondly, it uses high-temperature oil as the heating medium, which has higher temperature stability and greatly increases the heating rate, thereby improving production efficiency. Then, by using high-temperature oil, it breaks through the temperature point of traditional heating rods, allowing for product pressing at higher temperatures. Furthermore, the closed-loop oil-circuit heat recovery architecture reduces the loss of high-temperature oil and lowers production costs.

[0041] To facilitate understanding of the present invention, several embodiments are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present invention will be more thorough and complete.

[0042] The mold model used in this invention is 270, with dimensions of OD*ID*HT = 26.92mm*14.73mm*11.18mm. This patent is not limited to this model; the model shown here is only to make the purpose, technical solution, and advantages of the embodiments of this invention clearer.

[0043] Example 1

[0044] The power inductor gradient molding method based on high-temperature oil circulation hot pressing used in this embodiment includes: setting the pressing temperature of mold A to 300℃, the heating time to 5min, and the pressing pressure to 800MPa; setting the pressing temperature of mold B to 650℃, the heating time to 10min, and the pressing pressure to 400MPa; placing the coated water-atomized iron-based amorphous alloy powder with D50 = 15μm-20μm into an automatic feeding hopper to ensure consistent feed weight each time; starting the pressing of mold A; after pressing, the powder is transferred by a robotic arm to mold B for pressing, and this process is repeated; annealing the pressed magnetic ring at 450℃ for 60min in a vacuum environment; and testing the performance of the obtained magnetic powder core.

[0045] Comparative Example 1

[0046] The difference between this comparative example and Example 1 is that in step 1, only the temperature of mold A is used for pressing, and the pressing pressure is 800 MPa. The remaining steps are the same as in Example 1.

[0047] Comparative Example 2

[0048] The difference between this comparative example and Example 1 is that in step 1, only the temperature of mold B is used for pressing, and the pressing pressure is 800 MPa. The remaining steps are the same as in Example 1.

[0049] Comparative Example 3

[0050] The difference between this comparative example and Example 1 is that the temperature in step 1 and the pressing pressure of mold B are changed to 1200MPa, while the other steps are the same as in Example 1.

[0051] Comparative Example 4

[0052] The difference between this comparative example and Example 1 is that the pressing pressure in step 1 and the temperature of mold B are changed to 500°C, while the rest of the steps are the same as in Example 1.

[0053] Comparative Example 5

[0054] The difference between this comparative example and Example 1 is that the powder used in step 2 is gas-atomized iron-silicon-aluminum powder. The other steps are the same as in Example 1.

[0055] Comparative Example 6

[0056] This comparative example uses a traditional hot pressing process, with heating rods used as the heating medium for the mold;

[0057] The pressing temperature of mold A was set to 300℃, the heating time to 10 min, and the pressing pressure to 800 MPa. The pressing temperature of mold B was set to 450℃, the heating time to 30 min, and the pressing pressure to 400 MPa. The coated water-atomized iron-based amorphous alloy powder with a D50 of 15 μm-20 μm was placed in an automatic feeding hopper to ensure that the weight of each feed was consistent. Mold A was started for pressing. After pressing, the powder was transferred to mold B by a robotic arm for pressing, and this process was repeated. The pressed magnetic rings were then annealed at 450℃ for 60 min in a vacuum environment. The performance of the magnetic powder core was then tested.

[0058] Comparative Example 7

[0059] The difference between this comparative example and Comparative Example 5 is that in step 1, only the temperature of mold A is used for pressing, and the pressing pressure is 800 MPa. The other steps are the same as those in Comparative Example 5.

[0060] Comparative Example 8

[0061] The difference between this comparative example and Comparative Example 5 is that in step 1, only the temperature of mold B is used for pressing, and the pressing pressure is 800 MPa. The other steps are the same as those in Comparative Example 5.

[0062] Comparative Example 9

[0063] This comparative example uses a traditional cold pressing process with a pressing pressure of 2000 MPa. The coated water-atomized iron-based amorphous alloy powder, with a D50 of 15μm-20μm, is placed in an automatic feeding hopper to ensure consistent weight for each feeding. The pressed magnetic ring is then annealed at 450℃ for 60 minutes under vacuum. The performance of the prepared magnetic powder core is then tested.

[0064] In the above case, molds A and B have identical dimensions and layout. Temperature display utilizes both built-in temperature control and an external thermometer for simultaneous monitoring. The heating time in the test plan is determined using a timer and temperature detection equipment.

[0065] The magnetic powder cores prepared using the technical solutions of Example 1 and Comparative Examples 1-9 were tested for their product performance, and the test data are shown in Table 1.

[0066] Table 1:

[0067]

[0068] The data above shows that the system's thermal inertia is reduced to one-quarter of that of the electric heating mode, and the preheating time is shortened by 60%. Combined with a PID adaptive temperature control algorithm, precise temperature control at the ±0.5℃ level is achieved, resulting in a 42% reduction in overall energy consumption compared to traditional solutions, and an annual carbon emission reduction of 12.6 tons per unit. Furthermore, the hydraulic drive system eliminates the oxidation failure mechanism of the heating wire, extends the mean time between failures (MTBF) of key components, and improves the equipment's service life. The contact-type heat transfer method reduces thermal shock to the mold, and after several cycles of testing, no micro-crack propagation phenomenon common in traditional processes was observed.

[0069] In summary, the power inductor gradient molding method based on high-temperature oil circulation hot pressing in the above embodiments of the present invention achieves dynamic heat conduction throughout the mold through a high-temperature oil circulation system. Compared with the resistance rod point heat source mode, it reduces temperature gradient fluctuations and inductor core density deviations, improves product Q-value stability, and effectively solves the problem of magnetic domain distortion caused by local overheating. Secondly, the innovative closed-loop oil circuit heat recovery architecture reduces system thermal inertia, shortens preheating time, improves heating efficiency, and, combined with temperature control algorithms, achieves precise temperature control while reducing overall energy consumption.

[0070] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0071] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for power inductor gradient molding based on high-temperature oil circulation hot pressing, characterized in that, include: Iron-based amorphous alloy powder was obtained and the mold was heated; The iron-based amorphous alloy powder is fed into the cavity of a heated mold, and the iron-based amorphous alloy powder is pressed according to a preset pressure to obtain a magnetic powder core. The obtained magnetic powder core is annealed to prepare a power inductor.

2. The power inductor gradient forming method based on high-temperature oil circulation hot pressing according to claim 1, characterized in that, In the step of heating the mold: The mold is heated using a gradient heating method, with a heating temperature of 300℃-650℃.

3. The power inductor gradient forming method based on high-temperature oil circulation hot pressing according to claim 2, characterized in that, In the step of heating the mold: When the mold is heated to 300°C, it is held under pressure for 1 second; when the mold is heated to 650°C, it is held under pressure for 2 seconds to perform gradient heating on the mold.

4. The power inductor gradient forming method based on high-temperature oil circulation hot pressing according to claim 2, characterized in that, In the step of heating the mold: The heating medium is high-temperature oil.

5. The power inductor gradient forming method based on high-temperature oil circulation hot pressing according to claim 1, characterized in that, The preset pressure is 800 MPa.

6. The power inductor gradient forming method based on high-temperature oil circulation hot pressing according to claim 1, characterized in that, Annealing was performed in a vacuum environment at a temperature of 450℃ for 1 hour.

7. A power inductance gradient forming device based on high-temperature oil circulation hot pressing, characterized in that, For implementing the power inductor gradient forming method based on high-temperature oil circulation hot pressing as described in claims 1-6, the apparatus includes a forming mold, the forming mold comprising: An upper punch assembly, a lower punch assembly, and a middle die assembly disposed between the upper punch assembly and the lower punch assembly; The upper punch assembly includes an upper punch, an upper punch high-temperature oil circulation system, and an upper punch oil supply pipeline and an upper punch oil return pipeline connecting the upper punch and the upper punch high-temperature oil circulation system to form a closed oil circuit. The upper punch is provided with an upper punch oil circuit to connect the upper punch oil supply pipeline and the upper punch oil return pipeline. The intermediate mold assembly includes an intermediate mold, an intermediate mold high-temperature oil circulation system, and an intermediate mold oil supply pipeline and an intermediate mold oil return pipeline connecting the intermediate mold and the intermediate mold high-temperature oil circulation system to form a closed oil circuit. The intermediate mold is provided with an intermediate mold oil circuit to connect the intermediate mold oil supply pipeline and the intermediate mold oil return pipeline. Both the upper punch and the middle mold are equipped with temperature monitoring devices to control the temperature.

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