A high permeability near-spherical amorphous soft magnetic alloy magnetic core and a preparation method thereof

Abstract

The application discloses a kind of high magnetic permeability near-spherical amorphous soft magnetic alloy magnetic core and preparation method thereof, specifically relates to amorphous nanocrystalline soft magnetic alloy field.The method includes atomization preparation crystalline intermediate, plasma treatment and amorphization and magnetic core forming and post-processing.The advantage of this method is that the powder shape and structure can be accurately controlled, the magnetic permeability of the magnetic core is improved and the loss is reduced.The amorphous powder prepared by the application is a tail-shaped powder, and the tail shape enhances the compaction density and reduces the air gap loss.

Description

Technical Field

[0001] The invention relates to the field of amorphous nanocrystalline soft magnetic alloys, and in particular to a high-permeability nearly spherical amorphous soft magnetic alloy core and a preparation method thereof. Background Art

[0002] Due to the high electrical resistivity and high saturation magnetic induction intensity of amorphous powder in its amorphous state, amorphous magnetic cores made from this powder exhibit low power loss and excellent DC superposition resistance. Traditional methods for producing FeSiB amorphous powder typically utilize crushing of amorphous ribbons. For example, Chinese patent CN117444194A describes a new method for preparing soft magnetic composite materials by double-coating pure iron powder. The method involves pre-treating the FeSiB amorphous powder; mixing the pure iron powder and pre-treated amorphous FeSiB powder to produce magnetic powder; cold-pressing the magnetic powder into ring-shaped samples; and annealing the ring-shaped samples. This method has many advantages, particularly low manufacturing cost and high magnetic permeability. Amorphous magnetic cores made from this amorphous powder can have magnetic permeabilities ranging from μ45, μ60, μ75, and μ90. However, powders produced from crushed amorphous ribbons have a sheet thickness of only 20-30 microns, resulting in a flattened shape, effectively reducing eddy current losses. However, the low compaction density can result in poor DC superposition resistance. Moreover, adding iron powder to the raw materials can further improve the pressing density and anti-DC superposition characteristics, but the loss will increase significantly, and the magnetic permeability will decrease significantly after adding iron powder.

[0003] Therefore, the industry continues to explore the development of spherical amorphous powders and their magnetic cores to obtain lower power loss characteristics and better anti-DC superposition characteristics. The process method of gas atomization + water cooling can meet the preparation requirements of spherical amorphous powders. Chinese patent CN115831522A discloses an amorphous soft magnetic alloy powder and its preparation method and application. The raw materials are obtained by mixing according to the mass percentage molecular formula, and the raw materials are vacuum melted, cast and polished in sequence to obtain a master alloy; the master alloy is melted to form a melt, and the melt is broken into melt droplets by gas atomization; the melt droplets are mechanically broken by a high-speed turntable to obtain semi-molten particles, and the semi-molten particles are rapidly cooled by spraying water to obtain amorphous soft magnetic alloy powder. However, there are still two shortcomings: atomization produces completely spherical powders. Although the pressing density is high, spherical powders, especially FeSiB powders in an amorphous state, have high hardness and are difficult to shape. The molding strength is low, which causes magnetic core inductors to easily cause vibration and noise under high current conditions, affecting their application. At the same time, due to the completely spherical FeSiB amorphous powder, the contact surface between the magnetic core powder and the powder is small, resulting in low magnetic permeability of only 15-25. However, many applications require a magnetic permeability of μ60 or above. Therefore, it is currently very difficult to promote spherical FeSiB amorphous powder in the market application end.

[0004] Existing patents mostly adopt the addition of other elements such as Mn and Sn to improve the magnetic permeability of soft magnetic alloy materials, such as Chinese patent CN113096948A. However, the addition of other elements will affect the application of FeSiB amorphous powder alone and cannot meet the market application of spherical FeSiB amorphous powder.

[0005] Chinese patent CN104858441A discloses a method for preparing fine flaky metal soft magnetic alloy powder. The method comprises selecting two or three of Fe, Si, Al, Ni, and Mo as raw materials for alloy preparation; smelting the alloy in a medium-frequency induction furnace; atomizing the melt using a two-stream atomization method to produce a nearly spherical alloy powder; flattening the alloy powder by mechanical ball milling; annealing the resulting flaky powder, and preparing fine flaky metal soft magnetic alloy powder through ultrasonic vibration screening. The powder produced by this method is fine and flaky, with a particle size of 10-100μm, an average thickness of 0.1μm-5μm, an aspect ratio of 50-500, and a powder flattening rate of 90%. However, after the spherical flattening, the anti-DC superposition characteristics are not good due to insufficient pressing density. Summary of the Invention

[0006] To this end, the present invention provides a high magnetic permeability nearly spherical amorphous soft magnetic alloy core and a preparation method thereof to solve the existing problems.

[0007] The present invention provides a two-step method for preparing a high-permeability, nearly spherical amorphous soft magnetic alloy core. A crystalline intermediate is prepared by atomization, and then plasma treatment and amorphization are performed to achieve powder shape optimization and amorphous structure control, thereby improving the core density, magnetic permeability and high-frequency performance.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] According to one aspect of the present invention, a method for preparing a high-permeability, nearly spherical amorphous soft magnetic alloy core is provided, the method comprising:

[0010] Step 1: Atomization to prepare crystalline intermediates

[0011] The Fe-Si-B iron-based amorphous material is melted, the Fe-Si-B alloy solution is atomized using high-pressure nitrogen, and then cooled into a completely spherical alloy powder to obtain a crystalline intermediate of the spherical soft magnetic alloy powder;

[0012] Step 2: Plasma treatment and amorphization

[0013] A completely spherical Fe-Si-B powder intermediate is heated by a high-temperature plasma jet and rapidly sprayed into an amorphization cooling pool. The Fe-Si-B powder intermediate is heated by the plasma jet and forms a nearly spherical shape with a tail during high-speed flight. It then enters the amorphization cooling pool and is rapidly cooled by coolant to form amorphous Fe-Si-B powder, which is nearly spherical with a tail.

[0014] Step 3: Core forming and post-processing

[0015] The amorphous Fe-Si-B powder obtained in step 2 is surface-insulated and coated, and after adding lubricant, it is pressed into a magnetic core.

[0016] As an example, in the Fe-Si-B iron-based amorphous material, Fe:Si:B=75-85:10-15:5-10 (atomic percentage), and as an example, Fe:Si:B=79:13:8 (atomic percentage) is preferred.

[0017] Furthermore, in step 1, the high-pressure nitrogen pressure is 3-8 MPa. The molten metal flow is broken into tiny droplets by the high-pressure nitrogen, and the droplets are formed into spherical shapes under the action of surface tension.

[0018] The cooling rate after atomization is about 10 3 -10 4 K / s, so that FeSiB is not completely amorphous, resulting in the formation of microcrystalline or nanocrystalline structure, so it is called "crystalline intermediate".

[0019] Furthermore, in step 1, the particle size of the spherical soft magnetic alloy powder is 5-55 microns.

[0020] Furthermore, in step 2, the temperature of the high-temperature plasma jet is 3,000-10,000°C. The high-temperature plasma can instantly heat the powder surface to a molten state. Simultaneously, the high-speed gas flow (such as argon) carries the powder, causing partial melting and resulting in shape change, forming a "nearly spherical shape with a tail" (similar to a satellite particle), which may enhance mechanical interlocking during pressing and increase density.

[0021] Furthermore, in step 2, the working gas of the plasma jet is one or more of nitrogen, argon, and hydrogen.

[0022] Furthermore, in step 2, the coolant in the amorphization cooling pool is water, liquid nitrogen or alcohol.

[0023] Furthermore, in the step 2, the cooling rate of the amorphous cooling pool is 10 5 -10 6 K / s. This inhibits the orderly arrangement of atoms, forming an amorphous structure. Rapid solidification prevents the molten portion from regaining its spherical shape and instead solidifies it into a tail-shaped ribbon, increasing the specific surface area and improving subsequent insulation coating.

[0024] Insulation coating: Use phosphate, silane or organic resin (such as epoxy) coating to reduce eddy current loss.

[0025] Furthermore, in step 3, the lubricant is low molecular weight wax, zinc stearate or lithium stearate, and the amount added is 0.3-0.8 wt % to improve powder fluidity, reduce pressing friction and avoid density unevenness.

[0026] Pressing is done by high pressure pressing, usually using isostatic pressing or die pressing.

[0027] Furthermore, in step three, the annealing temperature is 380-420°C to eliminate internal stress and restore magnetic permeability. The holding time is 0.5-1.5 hours to prevent oxidation and stabilize the magnetic domain arrangement. The annealing atmosphere is vacuum or inert gas, and the annealed core is coated with a layer of epoxy resin. Low-temperature annealing preserves the amorphous properties and optimizes the soft magnetic properties.

[0028] According to another aspect of the present invention, a high-permeability, nearly spherical amorphous soft magnetic alloy core prepared by the above method is provided, wherein the density of the core is 6.60-7.00 g / cm3, and the length of the tail accounts for 5-15% of the particle diameter.

[0029] Before amorphization, the Fe-Si-B soft magnetic alloy powder is first made into a spherical intermediate powder by atomization, and then the FeSiB spherical intermediate powder is heated by a plasma jet until the surface is melted. During the high-speed flight of the intermediate powder driven by the high-speed plasma jet, the molten part of the liquid on the surface will flow to the tail to form a tail shape. This tail-shaped powder is an important characteristic factor for improving the forming strength and magnetic permeability of the amorphous magnetic core.

[0030] The present invention has the following advantages:

[0031] The present invention uses a two-step process to prepare amorphous powder: first, atomization to obtain a crystalline intermediate, followed by plasma treatment to remelt and quench it into an amorphous state, while simultaneously changing the powder shape. This method has the advantage of being able to accurately control the powder shape and structure, improving the magnetic permeability of the magnetic core and reducing losses.

[0032] The amorphous powder prepared by the present invention is a tail-shaped powder. The tail shape enhances the compaction density and pressing strength, thereby improving the molding appearance yield of the magnetic core, and can also reduce the noise of the magnetic core under the electromagnetic field and reduce the air gap loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other implementation drawings based on the provided drawings without inventive effort.

[0034] The structures, proportions, sizes, etc. illustrated in this specification are intended only to complement the contents disclosed herein and to facilitate understanding and reading by persons familiar with the art. They are not intended to limit the conditions under which the present invention may be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportions, or adjustments in sizes, without affecting the efficacy and objectives of the present invention, shall still fall within the scope of the technical contents disclosed herein.

[0035] Figure 1 A flow chart of a process for preparing a high-permeability, nearly spherical amorphous soft magnetic alloy core provided in Example 1 of the present invention;

[0036] Figure 2 Schematic diagram of the plasma treatment and amorphization principle provided in Example 1 of the present invention;

[0037] Figure 3 This is a TEM image of the nearly spherical amorphous soft magnetic powder provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0038] The following describes the implementation of the present invention using specific embodiments. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. Obviously, the embodiments described are only a portion of the present invention, not all of it. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0039] Example 1

[0040] This embodiment provides a method for preparing a nearly spherical amorphous soft magnetic alloy core with high magnetic permeability. The preparation process flow chart is as follows: Figure 1 As shown:

[0041] Step 1: Atomization to prepare crystalline intermediates

[0042] The Fe-Si-B (Fe:Si:B=79:13:8 (atomic percentage)) iron-based amorphous material was melted, and the Fe-Si-B alloy solution was atomized by 3MPa high-pressure nitrogen gas and heated to 10 3 K / s cooling into a completely spherical alloy powder to obtain a crystalline intermediate of a spherical soft magnetic alloy powder; the particle size is 5-35 microns, and the median particle size is 20 microns;

[0043] Step 2: Plasma treatment and amorphization

[0044] Schematic diagram of plasma treatment and amorphization principle Figure 2 As shown in the figure, the completely spherical Fe-Si-B powder intermediate is heated by the nitrogen of the high temperature 10000℃ plasma jet and quickly sprayed into the liquid nitrogen of the amorphization cooling pool. After being heated by the plasma jet, the Fe-Si-B powder intermediate forms a nearly spherical shape with a tail during high-speed flight and enters the amorphization cooling pool to be rapidly cooled by the coolant (cooling rate is 10 5 K / s) to form amorphous Fe-Si-B powder, which is nearly spherical with a tail (the tail accounts for 5%);

[0045] Step 3: Core forming and post-processing

[0046] The amorphous Fe-Si-B powder obtained in step 2 was subjected to conventional phosphoric acid passivation method for surface insulation and coating, lubricated with zinc stearate (0.8 wt%), isostatically pressed (700 MPa), annealed (400 ° C, 1 hour, nitrogen protection), and epoxy coated to obtain a magnetic core. The TEM image is shown in FIG. Figure 3 shown.

[0047] Example 2

[0048] This embodiment provides a method for preparing a high-permeability, nearly spherical amorphous soft magnetic alloy core:

[0049] The preparation method is the same as that of Example 1, and the magnetic core is prepared using the following parameters:

[0050] Alloy composition: Fe: 80%, Si: 12%, B: 8%;

[0051] Atomization process: nitrogen pressure 8MPa, particle size 5-30μm, median particle size 15μm, cooling rate 10 4 K / s;

[0052] Plasma treatment: Argon plasma jet (12,000°C), alcohol as coolant (cooling rate 10 5 K / s), the tail accounts for 8%;

[0053] Pressing and annealing: lithium stearate lubricant (1.0 wt%), molding pressure 600 MPa, annealing conditions 380 ° C / 1.5 hours (vacuum).

[0054] Example 3

[0055] This embodiment provides a method for preparing a high-permeability, nearly spherical amorphous soft magnetic alloy core:

[0056] The preparation method is the same as that of Example 1, and the magnetic core is prepared using the following parameters:

[0057] Alloy composition: Fe: 75%, Si: 15%, B: 10%;

[0058] Atomization process: nitrogen pressure 3MPa, particle size 10-55μm, cooling rate 10 4 K / s;

[0059] Plasma treatment: hydrogen plasma jet (18,000°C), coolant is water (cooling rate 10 6 K / s), the tail accounts for 15%;

[0060] Pressing and annealing: zinc stearate lubricant (0.5 wt%), isostatic pressing 800 MPa, annealing conditions 410° C. / 0.5 hour (argon protection).

[0061] Example 4

[0062] This embodiment provides a method for preparing a high-permeability, nearly spherical amorphous soft magnetic alloy core:

[0063] The preparation method is the same as that of Example 1, and the magnetic core is prepared using the following parameters:

[0064] Alloy composition: Fe: 85%, Si: 10%, B: 5%;

[0065] Atomization process: nitrogen pressure 6MPa, particle size 15-45μm, cooling rate 10 3K / s;

[0066] Plasma treatment: Argon-nitrogen mixed plasma jet (20,000°C), liquid nitrogen (cooling rate 106K / s), tail proportion 5%;

[0067] Pressing and annealing: calcium stearate lubricant (0.7 wt%), molding pressure 500 MPa, annealing conditions 390 ° C / 1.2 hours (vacuum).

[0068] Example 5

[0069] This embodiment provides a method for preparing a high-permeability, nearly spherical amorphous soft magnetic alloy core:

[0070] The preparation method is the same as that of Example 1, and the magnetic core is prepared using the following parameters:

[0071] Alloy composition: Fe: 82%, Si: 11%, B: 7%;

[0072] Atomization process: nitrogen pressure 4MPa, particle size 25-55μm, cooling rate 103K / s;

[0073] Plasma treatment: Argon plasma jet (10,000°C), water as coolant (cooling rate 10 5 K / s), the tail accounts for 12%;

[0074] Pressing and annealing: zinc stearate lubricant (0.6 wt%), isostatic pressing 750 MPa, annealing condition 400° C. / 1 hour (nitrogen protection).

[0075] Comparative Example 1

[0076] This comparative example provides a method for preparing a high permeability amorphous soft magnetic alloy core:

[0077] Without the plasma treatment and amorphization of step 2, the crystalline intermediate of the spherical soft magnetic alloy powder obtained in step 1 is directly subjected to magnetic core forming and post-processing to obtain a magnetic core.

[0078] Other step parameters are the same as in Example 1.

[0079] Comparative Example 2

[0080] This comparative example provides a method for preparing a high permeability amorphous soft magnetic alloy core:

[0081] Alloy composition: Fe:79%, Si:13%, B:8%;

[0082] Step 1: Fe prepared by water-gas atomization method 79 Si 13B8, amorphous powder particles, the powder is oval, comma, satellite sphere, and its median particle size is 20 μm. Other details are exactly the same as in Example 1.

[0083] Comparative Example 3

[0084] This comparative example provides a method for preparing a high permeability amorphous soft magnetic alloy core:

[0085] Replace step 2 of Example 1 of the present invention with the following: a crystalline intermediate of spherical soft magnetic alloy powder is used to flatten the atomized alloy powder by mechanical ball milling. The atomized soft magnetic alloy powder is placed in a stainless steel ball mill together with stainless steel balls, with a ball-to-material ratio of 5:1, and 0.5wt% of stearic acid by weight of the powder is added as a powder dispersant to prevent secondary agglomeration of the powder. The high-energy stirring ball mill rotates at 1000 rpm and the ball milling time is 30 minutes. The metal powder is stratified and extended by the impact and friction of the steel balls, and is crushed into flaky powder. After flattening, the nearly spherical powder is gradually ground into a flat shape, the powder surface is relatively smooth, the boundaries between the particles are clear, and there is no agglomeration. The flaky powder after flattening is placed in a vacuum electric furnace and annealed under inert gas (N2, Ar) protection conditions at an annealing temperature of 450°C and a holding time of 1 hour. The prepared powder is fine flakes. Other conditions are exactly the same as in Example 1 to obtain a magnetic core.

[0086] Comparative Example 4

[0087] This comparative example provides a method for preparing a high permeability amorphous soft magnetic alloy core:

[0088] The alloy is smelted in an argon atmosphere to a temperature of 1600°C. The melt is then poured into a 1000°C ladle. Using high-pressure argon gas at a post-valve pressure of 4 MPa, the melt is atomized through a 2mm aperture at a 20° atomization angle to form droplets. A high-speed rotary table rotating at 8000 rpm mechanically crushes the droplets into fine, semi-molten particles. The semi-molten particles are then cooled using a spray water spray at a flow rate of 40 L / min and a pressure of 0.2 MPa to produce spherical amorphous soft magnetic alloy powder. The median particle size is 25 μm.

[0089] Comparative Example 5

[0090] This comparative example provides a method for preparing a high permeability amorphous soft magnetic alloy core:

[0091] The annealing temperature is 450° C., and the other steps are completely consistent with those in Example 1.

[0092] Experimental Example 1

[0093] The magnetic cores obtained in Examples 1-5 and Comparative Examples 1-5 were subjected to physical testing, and the results are shown in Table 1.

[0094] Table 1

[0095] <![CDATA[Density (g / cm 3 )]]> shape Example 1 6.7 Nearly spherical + 5% tail Example 2 6.6 Nearly spherical +8% tail Example 3 6.8 Nearly spherical + 10% tail Example 4 6.9 Nearly spherical +12% tail Example 5 7.0 Nearly spherical + 15% tail Comparative Example 1 7.05 Complete sphere Comparative Example 2 6.7 Oval, comma, satellite sphere Comparative Example 3 6.3 flat Comparative Example 4 6.6 Complete sphere Comparative Example 5 6.9 Nearly spherical + 5% tail

[0096] Experimental Example 2

[0097] The magnetic cores obtained from Examples 1-5 and Comparative Examples 1-6 were tested, and the test results are shown in Table 2:

[0098] Loss 1: Under the test condition of 50KHz@1000Gs;

[0099] Loss 2: Tested at 10mT / 100kHz;

[0100] DC superposition immunity: Test condition is 100 Oersted.

[0101] Table 2

[0102]

[0103]

[0104] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made thereto. Therefore, such modifications and improvements, without departing from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A method for preparing a high permeability nearly spherical amorphous soft magnetic alloy core, characterized in that: The method comprises: Step 1: Atomization to prepare crystalline intermediates The Fe-Si-B iron-based amorphous material is melted, and the Fe-Si-B alloy solution is atomized and cooled into a completely spherical alloy powder using high-pressure nitrogen to obtain a crystalline intermediate of the spherical soft magnetic alloy powder; Step 2: Plasma treatment and amorphization A completely spherical Fe-Si-B powder intermediate is heated by a high-temperature plasma jet and rapidly sprayed into an amorphization cooling pool. The Fe-Si-B powder intermediate is heated by the plasma jet and forms a nearly spherical shape with a tail during high-speed flight. After entering the amorphization cooling pool, it is rapidly cooled by coolant to form amorphous Fe-Si-B powder, which is nearly spherical with a tail. Step 3: Core forming and post-processing The amorphous Fe-Si-B powder obtained in step 2 is surface-insulated and coated, lubricated, and then pressed into a magnetic core; In the step 1, the particle size of the spherical soft magnetic alloy powder is 3-55 microns; In the step 2, the particle is nearly spherical with a tail, and the length of the tail accounts for 5-15% of the particle size; In the step 2, the temperature of the high-temperature plasma jet is 3000-10000° C.; In the step 2, the cooling rate of the amorphous cooling pool is 10 5 –10 6 K / s; The atomic percentages of Fe:Si:B in the Fe-Si-B iron-based amorphous material are: 75-85:10-15:5-10.

2. The method for preparing a high permeability nearly spherical amorphous soft magnetic alloy core according to claim 1, characterized in that: In the step 2, the working gas of the plasma jet is one or more of nitrogen, argon and hydrogen.

3. The method for preparing a high permeability nearly spherical amorphous soft magnetic alloy core according to claim 1, characterized in that: In the step 2, the coolant in the amorphization cooling pool is water, liquid nitrogen or alcohol.

4. The method for preparing a high permeability nearly spherical amorphous soft magnetic alloy core according to claim 1, characterized in that: In the step 3, the lubricant is low molecular weight wax, zinc stearate or lithium stearate, and the addition amount is 0.3-0.8wt%.

5. The method for preparing a high permeability nearly spherical amorphous soft magnetic alloy core according to claim 1, characterized in that: In the step 3, the annealing condition is 380-420° C., the holding time is 0.5 hours to 1.5 hours, the annealing atmosphere is vacuum or inert gas protection, and the annealed magnetic core needs to be coated with a layer of epoxy resin paint on the outer layer.

6. A high permeability nearly spherical amorphous soft magnetic alloy core prepared by the method of any one of claims 1 to 5, characterized in that: The density of the magnetic core is 6.60-7.00 g / cm3.

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