A method for forming uniform density of iron-nickel shaped magnetic powder cores

Abstract

This invention discloses a method for forming a uniformly shaped iron-nickel magnetic powder core, comprising the following steps: Step 1, determining the structure of the iron-nickel magnetic powder core to be prepared and selecting a corresponding mold, then dividing the mold into multiple small area units according to the structural distribution and corresponding function of the iron-nickel magnetic powder core to be prepared; Step 2, filling each small area unit in the mold with a preset amount of pre-coated iron-nickel powder using a preset feeding box; Step 3, performing multi-stage pressing and forming on the filled powder; Step 4, subjecting the pressed semi-finished product to heat treatment-impregnation-drying treatment to obtain the target iron-nickel magnetic powder core. This invention aims to achieve uniformly formed iron-nickel magnetic powder cores.

Description

Technical Field

[0001] This invention relates to the field of iron-nickel shaped magnetic powder core technology, and in particular to a method for forming iron-nickel shaped magnetic powder cores with uniform density. Background Technology

[0002] Magnetic powder cores are soft magnetic materials formed by pressing a mixture of ferromagnetic powder particles and an insulating medium. The magnetoelectric properties of magnetic powder cores mainly depend on the permeability of the powder material, the size and shape of the particles, their fill factor, the content of the insulating medium, the molding pressure, and the heat treatment process. The magnetic powder includes Fe-Si, Fe-Ni, and Fe-Si-Al metal powders, as well as amorphous and nanocrystalline alloy powders. The insulating coating agents can be broadly classified into organic coating agents (epoxy resin, polyamide resin, silicone resin, polyvinyl alcohol, phenolic resin, and polystyrene, etc.) and inorganic coating agents (mica, water glass, oxide layers, etc.). The pressing methods mainly include cold pressing, warm pressing, vacuum hot pressing, two-step pressing, and die-wall lubrication pressing. However, in the cold pressing process, problems such as uneven density, insufficient mechanical strength, and die wear exist in the structural forming of irregularly shaped magnetic powder cores.

[0003] Existing invention patent CN114005669A discloses a manufacturing process for irregularly shaped ferrite cores, which involves stamping: using soft magnetic ferrite powder particles, a closed-type or integral-type blank is prepared by bidirectional stamping with a die on a vertical forming machine or a high-speed rotary forming machine; sintering; cutting and grinding; ultrasonic cleaning; and inspection. Although this overcomes the problem of product deformation that is easily caused by conventional manufacturing methods for irregularly shaped magnetic cores, the core manufacturing loss is high and the density differences in different regions of different irregularly shaped magnetic cores are not taken into account. Summary of the Invention

[0004] The main objective of this invention is to provide a method for forming iron-nickel irregular magnetic powder cores with uniform density, aiming to solve the technical problem that existing irregular magnetic powder cores have large magnetic losses and cannot overcome the problem of uneven density in the structural forming of irregular magnetic powder cores.

[0005] To achieve the above objectives, the present invention provides a method for forming uniform density of iron-nickel shaped magnetic powder cores, the method comprising the following steps:

[0006] Step 1: Determine the structure of the iron-nickel shaped magnetic powder core to be prepared and select the corresponding mold. Then, according to the structural distribution of the iron-nickel shaped magnetic powder core to be prepared and its corresponding function, divide the mold into multiple small regional units.

[0007] Step 2: Fill each small area unit in the mold with the corresponding preset amount of coated iron-nickel powder using a preset feeding box;

[0008] Step 3: Perform multi-stage pressing and molding of the filler powder;

[0009] Step 4: The pressed semi-finished product is subjected to heat treatment, impregnation and drying to obtain the target iron-nickel shaped magnetic powder core.

[0010] Optionally, the iron-nickel shaped magnetic powder core is an EE type magnetic powder core or an EQ type magnetic powder core. After step 1 and before step 2, at least three different particle sizes of iron-nickel powder are stirred in a preset ratio, and the iron-nickel mass ratio in each particle size is 55:45.

[0011] Optionally, iron-nickel powders of -500 mesh, -300 mesh, and -150 mesh are mixed at mass ratios of 65%-75%, 20%-25%, and 5%-15%, respectively.

[0012] Optionally, in step 1, the mold for the iron-nickel shaped magnetic powder core is divided into a column region and an outer frame region. The column region includes two side column regions located at both ends and a central column region located in the middle. The outer frame region includes a central column extension region, two side column extension regions, and two central column-side column extension connection regions.

[0013] Optionally, in step 2, the feeding box includes a box body, a feeding port located on the upper surface of the box body, and an open bottom surface of the box body, wherein a screen is centrally arranged on the bottom surface of the box body.

[0014] Optionally, the width of the screen is the same as the width of the central column area.

[0015] Optionally, in step 3, the filling powder is compacted from the outer frame area to the column area in stages using a three-stage cylinder, a two-stage cylinder, and a one-stage cylinder.

[0016] Optionally, in step 4, the compression ratio of the two side column extension areas, the two middle column-side column extension connection areas, and the two side column areas in the pressed product is 2-2.1, and the compression ratio of the middle column area to the middle column extension area is 2.2-2.3.

[0017] Optionally, step 3 specifically includes:

[0018] A three-stage cylinder is used to apply 5t of pressure to the filling powder in advance to initially compact the powder;

[0019] Then, a secondary cylinder is used to apply a pressure of 12t to the initially compacted filler powder to further compact the powder.

[0020] Finally, a pressure of 19.5t is applied to the compacted filler powder in the second-stage cylinder using the first-stage cylinder to achieve the desired density and strength.

[0021] Optionally, step 4 specifically includes: sending the pressed semi-finished product into a preheating furnace and baking it in an atmosphere of 220°C for 3.5 hours, then transferring it to an atmosphere of 750°C for 2 hours of heat treatment, waiting for the product to return to room temperature, immersing it in an impregnation solution with a concentration of 1.45±0.02 for 15 minutes, and finally drying it at 190°C for 2 hours to obtain the target iron-nickel shaped magnetic powder core.

[0022] Beneficial effects:

[0023] This invention determines the structure of the desired iron-nickel shaped magnetic powder core and selects a corresponding mold. Then, based on the structural distribution and corresponding function of the core, the mold is divided into multiple small regional units. Each small regional unit in the mold is filled with a predetermined amount of coated iron-nickel powder using a pre-set feeding box. The filled powder is then subjected to multi-stage pressing. Finally, the pressed semi-finished product undergoes heat treatment, impregnation, and drying to obtain the target iron-nickel shaped magnetic powder core. The invention utilizes a feeding box with a sieve to add iron-nickel mixed powder to the corresponding areas of the mold, aligning the sieve with the width of the central column area. This differentiates the amount of iron-nickel mixed powder added to the central column area and its extension area from other areas, allowing for the simultaneous filling of different regions of the same mold with iron-nickel mixed powder at different flow rates. This ensures that the density of each region of the iron-nickel shaped magnetic powder core is essentially consistent during subsequent pressing, avoiding inconsistencies in mechanical strength and magnetic properties caused by density gradients, and preventing material cracking or defects. Furthermore, the entire preparation process is simple and convenient, facilitating widespread application. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0025] Figure 1 This is a flowchart of an embodiment of a method for forming uniform density of iron-nickel shaped magnetic powder cores according to the present invention;

[0026] Figure 2 for Figure 1 A schematic diagram of the EE-type magnetic powder core mold;

[0027] Figure 3 for Figure 1 A schematic diagram of the structure of the EQ type magnetic powder core mold;

[0028] Figure 4 for Figure 1 A schematic diagram of the feeding box used in the process;

[0029] Figure 5 for Figure 2 A schematic diagram of the bottom structure in the middle;

[0030] Figure 6 for Figure 1 A schematic diagram of the pressing operation in the process;

[0031] Figure 7 To adopt Figure 1 Top view and cross-sectional view of the EE-type magnetic powder core prepared by the method;

[0032] Figure 8 To adopt Figure 1 Top view and cross-sectional view of the EQ type magnetic powder core prepared by the method.

[0033] Explanation of icon numbers:

[0034] label name label name 1 First side column area 2 Central column area 3 Second side column area 5 Feed port 6 bottom of the box body 7 sieve 101 First side pillar extension area 201 First central post-side post extension connection area 202 Central column extension area 203 Second central column-side column extension connection area 301 Second side column extension area 21 First stage cylinder 22 Secondary cylinder 23 Three-stage cylinder 24 Undershoot 25 base 26 Central cylinder 27 negative mold

[0035] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] It should be noted that all directional indicators (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0038] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0039] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0040] See Figure 1 This invention provides a flowchart of an embodiment of a method for forming uniform density of iron-nickel shaped magnetic powder cores, the method comprising the following steps:

[0041] Step 1: Determine the structure of the iron-nickel shaped magnetic powder core to be prepared and select the corresponding mold. Then, according to the structural distribution of the iron-nickel shaped magnetic powder core to be prepared and its corresponding function, divide the mold into multiple small regional units.

[0042] Step 2: Fill each small area unit in the mold with the corresponding preset amount of coated iron-nickel powder using a preset feeding box.

[0043] Specifically, in this embodiment, the iron-nickel shaped magnetic powder core is an EE-type magnetic powder core or an EQ-type magnetic powder core, such as... Figure 2-3 As shown, the iron-nickel shaped magnetic powder core mold is divided into a pillar region and an outer frame region. The pillar region includes first and second side pillar regions 1 and 3 located at both ends and a central pillar region 2 located in the middle. The outer frame region includes a central pillar extension region 202, first and second side pillar extension regions 101 and 301, and first and second central pillar-side pillar extension connection regions 201 and 203. In actual mold filling, for both EE-type and EQ-type magnetic powder cores, material is filled from the outer frame region to the pillar region. The overall width of the central pillar region 2 is greater than the width of the two side pillar regions, and the structures and dimensions of the two side pillar regions are basically the same. Consequently, the widths of the first and second side pillar extension regions 101 and 301 are smaller than the width of the corresponding central pillar extension region 202. The resulting iron-nickel shaped magnetic powder core corresponds to the corresponding mold.

[0044] Simultaneously, before pressing the magnetic powder core, at least three different particle sizes of iron-nickel powder are pre-stirred according to a preset ratio, and the iron-nickel mass ratio in each particle size is 55:45. Furthermore, -500 mesh, -300 mesh, and -150 mesh iron-nickel powders are mixed in mass ratios of 65%-75%, 20%-25%, and 5%-15%, respectively. Preferably, for EE type magnetic powder cores, -500 mesh, -300 mesh, and -150 mesh iron-nickel powders are mixed in mass ratios of 70%-75%, 20%-25%, and 10%-15%, respectively; for EQ type magnetic powder cores, -500 mesh, -300 mesh, and -150 mesh iron-nickel powders are mixed in mass ratios of 65%-70%, 20%-25%, and 5%-15%, respectively. More preferably, the iron-nickel powder is stirred in a mixing bucket for 30 minutes according to the ratio to ensure its uniformity, and then the prepared organic-inorganic coating agent is poured in and reacted fully at 70°C for 2.5 hours. After the powder is dried, the preset amount of coated iron-nickel powder is added to the corresponding mold using a feeding box.

[0045] Furthermore, such as Figure 4-5As shown, the feeding box includes a box body, a feeding port 5 located on the upper surface of the box body, and an open bottom surface 6 of the box body. A screen 7 is also centrally arranged on the bottom surface 6 of the box body. Specifically, the particle size of the screen 7 is 150μm-250μm. Preferably, for EE type magnetic powder cores, the particle size of the screen 7 is 180μm-250μm, and for EQ type magnetic powder cores, the particle size of the screen 7 is 150μm-200μm. More preferably, the width of the screen 7 is consistent with the width of the central column area 2 in the corresponding mold. During actual feeding, the screen 7 in the feeding box is located directly above the central column area 2, so that the material passing through the screen 7 in the feeding box falls into the central column area 2. The purpose is to reduce the filling flow rate of the iron-nickel mixed powder entering the central column area 2 by using the screen 7, thereby differentiating the amount of coated iron-nickel powder added in the central column area 2 and the central column extension area 201 from other areas in the same time.

[0046] Step 3: Perform multi-stage pressing and molding of the filler powder.

[0047] Specifically, a pressing device is used to press the filler powder, such as... Figure 6 As shown, the pressing device includes a base 25, a lower punch 24 placed on the base 25, and a primary cylinder 21, a secondary cylinder 22, and a tertiary cylinder 23 located above the lower punch 24. The lower punch 24 contains an iron-nickel shaped magnetic powder core mold, which includes a female mold 26. The base 25 also contains a central cylinder 27 corresponding to the mold size. The filling powder is then compacted in stages from the outer frame area to the column area using the tertiary cylinder 23, the secondary cylinder 22, and the primary cylinder 21. Taking EE-type magnetic powder core pressing as an example, a 5t pressure is applied to the filling powder using the tertiary cylinder to initially compact the powder; then a 12t pressure is applied to the initially compacted filling powder using the secondary cylinder to further compact the powder; finally, a 19.5t pressure is applied to the compacted filling powder using the primary cylinder to achieve the desired density and strength.

[0048] Step 4: The pressed semi-finished product is subjected to heat treatment, impregnation and drying to obtain the target iron-nickel shaped magnetic powder core.

[0049] Specifically, during the pressing of the EE-type magnetic powder core, the pressed semi-finished product is sent to a preheating furnace and baked in an atmosphere at 220°C for 3.5 hours. Then, it is heat-treated in an atmosphere at 750°C for 2 hours. After the product returns to room temperature, it is immersed in an impregnation solution with a concentration of 1.45±0.02 for 15 minutes. Finally, it is dried at 190°C for 2 hours to obtain the target iron-nickel shaped magnetic powder core. The compression ratios of the first and second side pillar extension regions 101 and 301, the first and second middle pillar-side pillar extension connection regions 201 and 203, and the first and second side pillar regions 1 and 3 in the pressed semi-finished product are all 2 to 2.1. The compression ratio of the middle pillar region 2 to the middle pillar extension region 202 is 2.2 to 2.3. Preferably, the compression ratios of the two side pillar extension regions, the two middle pillar-side pillar extension connection regions, and the two side pillar regions in the pressed semi-finished product are 2.1, and the compression ratio of the middle pillar region to the middle pillar extension region is 2.2. The compression ratio setting for each zone is based on the initial and theoretical densities of the iron-nickel powder, establishing a preliminary compression ratio range. Then, the initial compression ratio is calculated based on the target density and initial powder density for each zone. This can be done using the following formula:

[0050]

[0051] Where: C is the compression ratio, ρ f ρ0 is the initial powder density, where ρ is the target density. After calculating the initial compression ratio, finite element analysis (FEA) is used to simulate the pressure distribution and density changes during the pressing process, predicting the molding effect in each region. Based on the simulation results, the compression ratio of each region is fine-tuned to optimize density uniformity and reduce stress concentration.

[0052] Furthermore, such as Figure 7 The EE-type magnetic powder core prepared by the above method is shown in Table 1, along with its corresponding size range and parameters.

[0053] Table 1. Size range and parameters of each region of EE type magnetic powder core

[0054]

[0055] In the EE-type magnetic powder core prepared above, the width F of the corresponding central column region 2 is greater than the width L of the first and second side column regions 1 and 3, and the difference between the outer frame density ρ1 and the column density ρ2 is not significant.

[0056] And such as Figure 8 The EQ type magnetic powder core prepared by the above method is shown in Table 2, and the corresponding size range is shown in Table 2.

[0057] Table 2 Dimensions and parameters of each region of the EQ type magnetic powder core

[0058]

[0059] In the EQ-type magnetic powder core prepared above, the width D of the corresponding central column region 2 is greater than the widths (AE, AG) of the first and second side column regions 1 and 3, and the difference between the outer frame density ρ1 and the column density ρ2 is not significant.

[0060] Furthermore, to better illustrate the effects of the product obtained by the present invention, an EE-type magnetic powder core produced using existing technology is used as a comparative example to compare the performance of the product obtained by the present invention, as detailed in Table 2.

[0061] Table 3 compares the performance of the EE / EQ type magnetic powder cores prepared in the examples with those prepared using existing technologies.

[0062]

[0063] As shown in Table 3, the density difference between the pillar region and the outer frame region in the EE / EQ type magnetic powder core prepared by the present invention is smaller than that in the comparative example. Therefore, the preparation method of the present invention can effectively improve the density uniformity of the finished product. When the EE / EQ type magnetic powder cores of the comparative example and the present invention are used in corresponding devices, the inductance value of the device using the EE / EQ type magnetic powder core of the present invention is greater than that of the comparative example, the DC Bias value of the device using the EE / EQ type magnetic powder core of the present invention is greater than that of the comparative example, the Core Loss value of the device using the EE / EQ type magnetic powder core of the present invention is smaller than that of the comparative example, and the yield of the device is also much higher than that of the comparative example. Therefore, the magnetic powder core prepared by the present invention has improved molding rate, mechanical strength and geometric accuracy, and is suitable for producing complex-shaped magnetic powder cores that require high quality and high performance.

[0064] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method of molding an iron-nickel magnetic powder core with uniform density, characterized by, The method comprises the following steps: Step 1, determining the structure of the iron-nickel shaped magnetic powder core to be prepared and selecting a corresponding mold, then dividing the mold into multiple small area units according to the structure distribution of the iron-nickel shaped magnetic powder core to be prepared and its corresponding function, the mold of the iron-nickel shaped magnetic powder core is divided into a column area and an outer frame area, the column area includes two edge column areas at both ends and a middle column area in the middle, the outer frame area includes a middle column extension area, two edge column extension areas and two middle column-edge column extension connection areas, the width of the middle column area is greater than the width of the two edge column areas; Step 2, filling each small area unit in the mold with a preset amount of coated iron-nickel powder using a preset feeding box; Step 3, multi-stage compression molding of the filled powder to obtain a semi-finished product with corresponding area units of the mold of the iron-nickel shaped magnetic powder core; Step 4, heat treatment-impregnation-drying treatment of the semi-finished product after compression molding to obtain the target iron-nickel shaped magnetic powder core, the compression ratio of the two edge column extension areas, the two middle column-edge column extension connection areas and the two edge column areas in the semi-finished product after compression molding is 2-2.1, and the compression ratio of the middle column area and the middle column extension area is 2.2-2.

3.

2. The Fe-Ni ferrite powder core density uniformity forming method according to claim 1, characterized by, The iron-nickel shaped magnetic powder core is an EE type magnetic powder core or an EQ type magnetic powder core, and before step 2 and after step 1, at least three kinds of iron-nickel powder with different particle sizes are stirred according to a preset ratio, and the mass ratio of iron-nickel in each particle size is 55:

45.

3. The Fe-Ni ferrite powder core density uniformity forming method according to claim 2, characterized by, -500 mesh, -300 mesh and -150 mesh iron-nickel powder are mixed according to a mass ratio of 65%-75%, 20%-25% and 5%-15% respectively.

4. The Fe-Ni ferrite powder core consistency molding method according to claim 1, characterized by, In step 2, the feeding box comprises a box body, a feeding port on the upper surface of the box body and an open bottom surface of the box body, and a screen is arranged in the center of the bottom surface of the box body.

5. The Fe-Ni ferrite powder core consistency molding method according to claim 4, wherein The width of the screen is consistent with the width of the middle column area.

6. The Fe-Ni ferrite powder core consistency molding method according to claim 1, wherein In step 3, a three-stage cylinder, a two-stage cylinder and a one-stage cylinder are used to sequentially stage the compaction operation of the filled powder from the outer frame area to the column area.

7. The Fe-Ni ferrite powder core consistency molding method according to claim 6, wherein The step 3 specifically comprises: preliminary compaction of the powder by applying a 5t pressure to the filled powder using a three-stage cylinder; further compaction of the powder by applying a 12t pressure to the preliminarily compacted mold using a two-stage cylinder; finally, applying a 19.5t pressure to the two-stage compacted mold using a one-stage cylinder to achieve the desired density and strength.

8. The Fe-Ni ferrite powder core consistency molding method according to any one of claims 1 to 7, characterized by, The step 4 specifically comprises: sending the product after compression molding into a preheating furnace, baking in a 220℃ atmosphere for 3.5h, then transferring into a 750℃ atmosphere for heat treatment for 2h, waiting for the product to return to room temperature, soaking into a 1.45±0.02 concentration impregnation liquid pool for 15min, and finally drying at 190℃ for 2h to obtain the target iron-nickel shaped magnetic powder core.

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