Ultrathin iron-silicon-aluminum flaky powder and preparation method thereof

Abstract

The invention discloses ultrathin iron-silicon-aluminum flaky powder and a preparation method thereof, and particularly relates to the field of metal and alloy powder preparation. The method comprises the steps that firstly, an alloy material containing iron, silicon and aluminum is melted into alloy steel liquid through medium-frequency induction or electric arc induction, the steel liquid flows out through a flow limiting opening with the diameter being 3-8 mm, and gas atomization is conducted on the steel liquid through high-pressure nitrogen / argon; spraying atomized molten steel drops to the surface of a copper roller or a copper disc rotating at a high speed, and carrying out quenching solidification to form flaky powder; finally, the flaky powder is subjected to annealing treatment under the protection of nitrogen / argon; and grading and screening according to the granularity requirement to finally obtain the ultrathin iron-silicon-aluminum sheet-shaped powder. According to the preparation method, the thickness of the flaky powder can be further reduced, and the flake diameter of the flaky powder is increased, so that the length-diameter ratio is increased, and the high-frequency magnetic conductivity is further improved.

Description

Technical Field

[0001] The present invention relates to the field of metal and alloy powder preparation, and in particular to an ultra-thin Sendust flake powder and a preparation method thereof. Background Art

[0002] The traditional method for preparing sendust soft magnetic alloy flaky powder usually uses a stirred ball mill or a planetary ball mill as a grinding equipment, controls the ratio of steel balls to sendust soft magnetic alloy powder raw powder, ball milling time, selects a suitable ball milling medium solution and other processes and parameters, and can obtain sendust flake powder with a diameter-to-thickness ratio of (50-100):1, which meets the usual electromagnetic shielding and electromagnetic interference requirements. For example, Chinese patent CN104858441A, a method for preparing fine flaky metal soft magnetic alloy powder, the method includes selecting two or three of Fe, Si, Al, Ni and Mo as raw materials for alloy preparation; using a medium frequency induction furnace for alloy smelting; using a two-stream atomization method to atomize the melt and obtain a nearly spherical alloy powder; flattening the alloy powder by mechanical ball milling; annealing the obtained flaky powder, and preparing fine flaky metal soft magnetic alloy powder by ultrasonic vibration screening. However, due to the low directional motion rate of the steel balls in the traditional stirring ball mill, a large number of steel balls still collide with each other under the action of the stirring rod. In addition to the directional motion, the steel balls also move horizontally, etc., resulting in the formation of flake powders and powders being cold-welded by the collision of the steel balls again. As a result, the obtained flake powders are mostly finely crushed. Therefore, it is difficult for the traditional ball mill to avoid the shortcomings of flake powder fragmentation and cold welding as well as uneven surface of the flake powder.

[0003] Chinese patent CN116900322A discloses a highly flattened Sendust aluminum alloy absorbing magnetic powder and a preparation method thereof, belonging to the field of electromagnetic absorbing materials. The preparation method includes the steps of material selection, primary ball milling, drying, primary screening, secondary ball milling, annealing, and secondary screening. The present invention significantly improves the yield and magnetic permeability of flaky Sendust aluminum powder by changing the ratio of grinding ball material / solvent / raw material powder and the size of the grinding ball diameter, screening low diameter-to-thickness ratio magnetic powder for secondary ball milling, and regulating the ball milling speed. However, due to cold welding between the flakes, the thickness of the flakes is usually between 600-880 nanometers, which has a certain impact on its application in certain high-frequency bands such as the P / L band. The ball milling cannot achieve the expected flatness, which further affects the magnetic permeability. Chinese patent CN103350225A discloses a multi-stage rod mill method for flattening soft magnetic alloy magnetic powder. This method can improve the diameter-to-thickness ratio of the magnetic powder and improve the yield rate. However, the production process is complicated and requires multi-stage rod milling. At the same time, it takes a long time to rod mill (using two-stage abrasive, 30 hours per stage), and the production efficiency is very low. CN104249155A discloses a multi-stage ball milling method. Compared with the traditional process, the flattening rate of magnetic powder has been significantly improved. However, the process also requires multi-stage ball milling, the ball milling time is long (using two-stage abrasive, 5-8h per stage), the production efficiency is low, and the process parameters need to be precisely controlled, otherwise the flattening rate of the magnetic powder will be seriously affected. In order to solve the above problems, Chinese patent application CN110718347A discloses a method using dimethylformamide and / or dimethyl sulfoxide as solvents and ball milling at high temperature, especially 90°C-120°C, to obtain a magnetic powder material with a high aspect ratio. The method of this patent only requires one ball milling, and the ball milling time is only about 2h. Although the production efficiency is improved, the magnetic powder obtained in its best embodiment 3 has an aspect ratio of less than 50:1, accounting for 7%, an aspect ratio of 50:1-100:1, accounting for 10%, and an aspect ratio greater than 100:1, accounting for 83%. Its maximum magnetic permeability is only 181, and its aspect ratio still has a lot of room for improvement. How to further reduce the thickness of sendust flake powder to below 500 nanometers to further improve the absorbing performance of the absorbing material so that it can be used in a wider frequency band is a difficult problem that needs to be solved urgently. Summary of the Invention

[0004] To this end, the present invention provides an ultra-thin Sendust flake powder and a preparation method thereof to solve the existing problems.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] According to one aspect of the present invention, a method for preparing ultra-thin sendust flake powder is provided, the method comprising:

[0007] Step 1: Atomization

[0008] The alloy material containing Sendust is melted into alloy steel liquid by medium frequency induction or arc induction. The steel liquid flows out through a flow restriction with a diameter of 3-8 mm and is atomized by high-pressure nitrogen / argon gas.

[0009] Step 2: Condensation

[0010] The atomized molten steel droplets are sprayed onto the surface of a high-speed rotating copper roller or copper disk, and are rapidly solidified to form flaky powder;

[0011] Step 3: Annealing and screening

[0012] The flaky powder is annealed under nitrogen / argon protection; and is classified and sieved according to particle size requirements to finally obtain ultra-thin Sendust flake powder.

[0013] Furthermore, in the step 1, the alloy material containing sendust has a silicon content of 9.7-10.1 wt%, an aluminum content of 5.6-6.0 wt%, and a silicon-aluminum atomic ratio of 1.6-1.8, which promotes the formation of a DO3 ordered phase and further improves the magnetic permeability.

[0014] Furthermore, in step 1, the atomization parameters are a carrier gas pressure of 2-6 MPa and a gas flow rate of 600-2000 Nm 3 / h, and control the atomized droplet diameter to 5-40 microns.

[0015] The present invention adopts a 3-8mm flow restriction port with 2-6MPa high-pressure inert gas atomization to accurately control the droplet size (5-40μm), laying the foundation for subsequent sheet formation; the gas flow rate is 600-2000Nm 3 / h dynamic adjustment window to meet the atomization requirements of different alloy compositions.

[0016] Furthermore, in the step 2, the rotation speed of the copper roller or copper plate is 500-1000 rpm, and the cooling rate of the water cooling system is 10 6 -10 7 K / s. High-speed rotating copper roller (speed is not specifically quantified and it is recommended to be supplemented) with water cooling system to achieve 10 6 -10 7 Cooling rate in K / s.

[0017] Furthermore, in the step 2, the flake powder has a thickness of 100-400 nanometers, a flake diameter of 10-70 micrometers, an diameter-to-thickness ratio of 200-400:1, and a surface roughness Ra of less than 0.1 μm.

[0018] Furthermore, in the step three, the annealing temperature is 450-750° C., the heating rate is 3-5° C. / min, and the holding time is 1-3 hours.

[0019] Furthermore, in the step three, the annealed powder is subjected to particle size screening by air flow classification or vibrating screen, and the classification accuracy D90 deviation is less than 5%.

[0020] Furthermore, the air flow velocity of the air flow classification is 10-30 m / s.

[0021] Furthermore, in step three, the oxygen content of the ultra-thin Sendust flake powder is less than 800 ppm, and the reflection loss in the frequency band of 2-18 GHz is ≤-30 dB.

[0022] In the annealing treatment of the present invention, the treatment under a protective atmosphere can eliminate cold working stress and improve the magnetic domain orientation.

[0023] According to another aspect of the present invention, an ultra-thin sendust flaky powder is provided, and the flaky powder is prepared by any of the above methods.

[0024] The present invention has the following advantages:

[0025] The present invention first melts the sendust soft magnetic alloy uniformly and atomizes it into molten steel beads with a diameter of 5-40 microns, and then directly sprays the molten steel beads onto a high-speed rotating copper roller or copper disk. The molten steel is swung into flakes and rapidly cooled into flaky powder. Compared with the traditional ball milling process, the obtained flaky powder can quickly solidify to form a nanocrystalline structure, effectively suppress eddy current loss, further reduce the thickness of the flaky powder, increase the flake diameter of the flaky powder, thereby improving the aspect ratio and further improving the high-frequency magnetic permeability.

[0026] The ultra-thin Sendust flaky powder prepared by the present invention has lower surface roughness and can significantly improve the interface bonding strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] 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.

[0028] 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.

[0029] Figure 1This is a scanning electron microscope image of the flaky sendust powder provided in Example 1 of the present invention;

[0030] Figure 2 This is a scanning electron microscope image of the flaky sendust powder provided in Example 2 of the present invention;

[0031] Figure 3 This is a scanning electron microscope image of the flaky sendust powder provided in Example 3 of the present invention;

[0032] Figure 4 This is a scanning electron microscope image of the flaky sendust powder provided in Comparative Example 1 of the present invention;

[0033] Figure 5 This is a scanning electron microscope image of the flaky sendust powder provided in Comparative Example 2 of the present invention;

[0034] Figure 6 This is a scanning electron microscope image of the flaky sendust powder provided in Comparative Example 4 of the present invention;

[0035] Figure 7 This is a scanning electron microscope image of the flaky sendust powder provided in Comparative Example 5 of the present invention. DETAILED DESCRIPTION

[0036] 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.

[0037] The following is a specific example of how to prepare ultra-thin Sendust flake powder.

[0038] Example 1

[0039] This embodiment provides a method for preparing ultra-thin Sendust flake powder:

[0040] Step 1: Atomization

[0041] The alloy material containing sendust (silicon 9.9%, aluminum 5.9%, silicon aluminum atomic ratio 1.67, the rest is iron, bulk density AD = 0.29g / cm 3 ); The sendust raw materials are smelted in a medium frequency smelting furnace. The smelting process is carried out under a nitrogen atmosphere. After the alloy steel liquid is melted evenly, the steel liquid is passed through a flow restriction with a diameter of 4.5 mm and atomized with nitrogen;

[0042] The atomization parameters are carrier gas pressure of 4.5 MPa and gas flow rate of 1450 m 3 / h, controlling the atomized droplet diameter to 20 microns;

[0043] By adjusting the gas pressure, nozzle design and melt temperature, the smaller D is, the thinner the final sheet thickness (d) will be (d∝D 0.8 ): To reduce D, it is necessary to increase the atomizing gas pressure, reduce the melt viscosity (such as adjusting the Si / Al content) or optimize the nozzle design; the relationship between sheet thickness and rotation speed (h∝ω -0.5 ): Increase ω to a critical value (e.g. from 5000rpm to 20000rpm), h can be halved (h2 / h1=(5000 / 20000) 0.5 =0.5);

[0044] Step 2: Condensation

[0045] The atomized steel liquid droplets are placed on a high-speed rotating copper plate with a flight direction of 45 degrees. The diameter of the copper plate is 600 mm and the rotation speed of the copper plate is 800 rpm. The ... 6 K / s) is cooled and solidified to form flaky powder;

[0046] Step 3: Annealing and screening

[0047] The powder is collected through a dust bag and then annealed under nitrogen / argon protection at an annealing temperature of 600°C, a heating rate of 3°C / min, and a holding time of 1 hour to form flaky powder. According to the particle size requirements, the annealed powder is screened by air flow classification to finally obtain ultra-thin sendust flake powder.

[0048] The obtained flaky sendust powder was examined under a scanning electron microscope. Figure 1 As shown, the thickness test value is between 200-300 nanometers, laser particle size analysis, particle size D 50 =51 microns; the sheet diameter is 65 microns, the diameter-to-thickness ratio is 220, the powder flattening rate reaches 98%; the D90 deviation is <5%, the magnetic permeability of the absorbing material made after powder coating is 320, the coated surface is smooth and flat, and the powder oxygen content is 600ppm.

[0049] Example 2

[0050] This embodiment provides a method for preparing ultra-thin Sendust flake powder:

[0051] Step 1: Atomization

[0052] The alloy material containing sendust (9.7% silicon, 6.0% aluminum, 4.62 silicon-aluminum atomic ratio, and the rest iron) is melted in a medium frequency melting furnace under a nitrogen atmosphere. After the alloy steel liquid is evenly melted, the steel liquid is passed through a flow restriction with a diameter of 3 mm and atomized with nitrogen;

[0053] The atomization parameters are carrier gas pressure of 2 MPa and gas flow rate of 600 m 3 / h, controlling the atomized droplet diameter to 5 microns;

[0054] Step 2: Condensation

[0055] The atomized steel liquid droplets are placed on a high-speed rotating copper plate with a flight direction of 45 degrees. The diameter of the copper plate is 600 mm and the rotation speed of the copper plate is 500 rpm. The ... 7 K / s) is cooled and solidified to form flaky powder;

[0056] Step 3: Annealing and screening

[0057] The powder is collected through a dust bag and then annealed under nitrogen / argon protection at an annealing temperature of 450°C, a heating rate of 4°C / min, and a holding time of 1.5 hours to form flaky powder. According to the particle size requirements, the annealed powder is screened by air flow classification to finally obtain ultra-thin sendust flake powder.

[0058] The obtained flaky sendust powder was examined under a scanning electron microscope. Figure 2 As shown, the thickness test value is between 300-400 nanometers, laser particle size analysis, particle size D 50 =58 microns; bulk density = 0.32 g / cm3, sheet diameter is 62 microns, diameter-to-thickness ratio is 207, powder flattening rate reaches 98%; D90 deviation is <5%, the magnetic permeability of the absorbing material made after powder coating is 310, the coated surface is smooth and flat, and the powder oxygen content is 800ppm.

[0059] Example 3

[0060] This embodiment provides a method for preparing ultra-thin Sendust flake powder:

[0061] Step 1: Atomization

[0062] The alloy material containing sendust (10.1% silicon, 6.0% aluminum, 1.68 silicon-aluminum atomic ratio, and the rest iron) is melted in a medium frequency melting furnace under a nitrogen atmosphere. After the alloy steel liquid is evenly melted, the steel liquid is passed through a flow restriction with a diameter of 8 mm and atomized with nitrogen;

[0063] The atomization parameters are carrier gas pressure of 6 MPa and gas flow rate of 600 m 3 / h, controlling the atomized droplet diameter to 40 microns;

[0064] Step 2: Condensation

[0065] The atomized steel liquid droplets are placed on a high-speed rotating copper plate with a flight direction of 45 degrees. The diameter of the copper plate is 600 mm and the rotation speed of the copper plate is 1000 rpm. The ... 6 K / s) is cooled and solidified to form flaky powder;

[0066] Step 3: Annealing and screening

[0067] The powder is collected through a dust bag and then annealed under nitrogen / argon protection at an annealing temperature of 750°C, a heating rate of 5°C / min, and a holding time of 3 hours to form flaky powder. According to the particle size requirements, the annealed powder is screened by air flow classification to finally obtain ultra-thin sendust flake powder.

[0068] The obtained flaky sendust powder was examined under a scanning electron microscope. Figure 3 As shown, the thickness test value is between 100-200 nanometers, laser particle size analysis, particle size D 50 =46 microns; bulk density = 0.31 g / cm3, D90 deviation <5%, sheet diameter is 70 microns, diameter-to-thickness ratio is 380, powder flattening rate reaches 98%; the magnetic permeability of the absorbing material produced after powder coating is 340, the coated surface is smooth and flat, and the powder oxygen content is 500ppm.

[0069] Comparative Example 1

[0070] This comparative example provides a method for preparing ultra-thin Sendust flake powder:

[0071] In this comparative example, the pressure of step 1 is 1.5 MPa and the gas flow rate is 600 m 3 / h, the diameter of the atomized droplets was controlled to be 40 μm, and the other aspects were completely consistent with Example 1. The obtained flaky sendust powder was observed under a scanning electron microscope. Figure 4 As shown, the thickness test value is between 900-1000 nanometers, laser particle size analysis, particle size D 50 =70 microns, bulk density =0.32 g / cm3, D90 deviation <5%, sheet diameter is 95 microns, diameter-to-thickness ratio is 100, powder flattening rate reaches 90%; the magnetic permeability of the absorbing material produced after powder coating is 200, and the coated surface is smooth and flat.

[0072] When the pressure is too low and the air flow is low, the thickness will be too thick, the flattening rate will be reduced, and the magnetic permeability will also be low.

[0073] Comparative Example 2

[0074] This comparative example provides a method for preparing ultra-thin Sendust flake powder:

[0075] In this comparative example, the rotation speed of the copper disk in step 2 is 300 rpm, and the rest is exactly the same as in Example 1.

[0076] The obtained flaky sendust powder was observed under a scanning electron microscope. Figure 5 As shown, the thickness test value is between 900-1000 nanometers, laser particle size analysis, particle size D 50 =75 microns; bulk density = 0.29 g / cm3, D90 deviation <5%, sheet diameter is 142 microns, diameter-to-thickness ratio is 150, powder flattening rate reaches 95%; the absorbing material produced after powder coating has a magnetic permeability of 250, the coated surface is smooth and flat, and the powder oxygen content is 1100 ppm.

[0077] If the rotation speed is reduced, the thickness will increase significantly, which will increase the sheet diameter, reduce the diameter-to-thickness ratio, and reduce the magnetic permeability.

[0078] Comparative Example 3

[0079] This comparative example provides a method for preparing ultra-thin Sendust flake powder:

[0080] In this comparative example, the rotation speed of the copper disk in step 2 is 1500 rpm, and the rest is exactly the same as in Example 1.

[0081] The thickness of the obtained flaky sendust powder was between 100-200 nanometers under the scanning electron microscope, and the particle size D 50 =40 microns; bulk density = 0.32 g / cm3, D90 deviation <5%, sheet diameter is 32-45 microns, diameter-to-thickness ratio is 312, powder flattening rate reaches 90%, but high speed will make the powder uneven; the magnetic permeability of the absorbing material made after powder coating is 280, the coated surface is smooth and flat, and the powder oxygen content is 980ppm.

[0082] Properly increasing the rotation speed has the most significant effect on thinning and low loss, but if the rotation speed is too high (over 4500 rpm), the system will be unstable and the equipment will be unable to produce. Moreover, when the rotation speed is too high, the cooling rate may exceed the critical amorphous forming ability of the alloy, resulting in complete amorphization of the powder. It is difficult to form a uniform nanocrystalline structure in subsequent annealing, and the magnetic permeability decreases instead of increases.

[0083] Comparative Example 4

[0084] This comparative example provides a method for preparing ultra-thin Sendust flake powder:

[0085] (1) The alloy material containing Sendust is the same as that in Example 1;

[0086] The grinding balls are GCr15 bearing steel balls, HRC>60, and the ball diameter is 5mm;

[0087] The solvent is a mixed solvent of ethanol and dimethyl sulfoxide, wherein the mass ratio of ethanol to dimethyl sulfoxide is 8:1;

[0088] (2) Primary ball milling: The grinding balls, solvent, and raw material powder of step (1) are sequentially added to a ball mill for primary ball milling, wherein, by mass ratio, the grinding balls: solvent: raw material powder = 10:6:1, the grinding stirring speed V1 is 275 rpm, and the stirring speed is constant; during the grinding process, cooling water is circulated through the outer interlayer of the grinding cylinder, and the temperature of the slurry is maintained at 50°C-65°C; the powder is ground once until the bulk density AD is less than 0.5g / cm 3 Time discharging;

[0089] (3) Drying: The slurry prepared in step (2) is pumped into a centrifuge, and after liquid-solid separation, the wet powder is placed in a 75°C oven for low-temperature drying;

[0090] (4) Sieving: The powder dried in step (3) was placed through a 600-mesh sieve to obtain -600-mesh and +600-mesh powders;

[0091] (5) Secondary ball milling: The -600 mesh powder is placed in a ball mill for secondary ball milling. The ball-solvent-raw material powder ratio, ball size, and solvent used in the secondary ball milling are the same as those in the primary ball milling. The secondary ball milling rate is 1.1 times that of V1. The powder is ground to an apparent density AD < 0.48 g / cm 3 The material is discharged, and then dried according to the method of step (3) to obtain dry powder;

[0092] (6) Annealing: The dry powder obtained by the secondary ball milling in step (5) was uniformly mixed with the +600 mesh powder obtained by sieving in step (4), and then subjected to high-temperature annealing at a temperature of 700°C for 61 minutes, using argon as a protective atmosphere, and then cooled to <30°C before being removed from the furnace;

[0093] (7) Secondary screening: The obtained flaky powder is put into a vibrating screen and screened to 160 mesh, and the -160 mesh flaky powder is collected to obtain ultra-thin sendust flake powder.

[0094] The obtained flaky sendust powder was observed under a scanning electron microscope. Figure 6 As shown, the thickness test value is between 600-700 nanometers, and the laser particle size analysis particle size D 50 =64 microns; bulk density = 0.32 g / cm3, D90 deviation <5%, sheet diameter is 42 microns, diameter-to-thickness ratio is 204, powder flattening rate reaches 90%; the magnetic permeability of the absorbing material produced after powder coating is 298, the coating surface is smooth and flat, and the powder oxygen content is 1007ppm.

[0095] Ball milling is used to increase the flattening rate of the powder. On the one hand, the increase in the flattening rate is limited, and on the other hand, the reduction in thickness is limited. In addition, the oxygen content of the powder will increase during the ball milling process.

[0096] Comparative Example 5

[0097] This comparative example provides a method for preparing ultra-thin Sendust flake powder:

[0098] The alloy material containing Sendust is the same as that in Example 1;

[0099] The alloy is smelted in a medium-frequency vacuum induction furnace under atmospheric pressure, using nitrogen to protect the alloy from oxidation. The alloy is melted at 1550°C, with a superheat maintained at 100°C. After the alloy is fully melted and its composition is homogenized, the liquid metal is atomized and pulverized using a V-shaped high-pressure water atomizer nozzle. The atomization pressure is controlled at 70 MPa, producing a nearly spherical soft magnetic powder. The atomized soft magnetic alloy powder is placed in a stainless steel ball mill with stainless steel balls at a ball-to-material ratio of 5:1. Polyvinyl alcohol (1.5 wt% of the powder mass) is added as a powder dispersant to prevent secondary agglomeration. The high-energy stirred ball mill is operated at 1500 rpm for 60 minutes. The impact and friction of the steel balls causes the metal powder to separate and expand, ultimately pulverizing into flaky powder. The flattened flaky powder is then placed in a vacuum furnace for annealing under inert gas (N2, Ar) at 400°C for 1 hour. The prepared powder is in the form of fine flakes.

[0100] The obtained flaky sendust powder was observed under a scanning electron microscope. Figure 7 As shown, the thickness test value is between 700-800 nanometers, laser particle size analysis, particle size D 50 =80μm, bulk density =0.32 g / cm3, D90 deviation <5%, sheet diameter is 1μm, diameter-to-thickness ratio is 80, powder flattening rate reaches 80%; the absorbing material produced after powder coating has a magnetic permeability of 230, the coated surface is smooth and flat, and the powder oxygen content is 1200ppm.

[0101] Ball milling is used to increase the flattening rate of the powder. On the one hand, the increase in the flattening rate is limited, and on the other hand, the reduction in thickness is limited. In addition, the oxygen content of the powder will increase during the ball milling process.

[0102] 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 ultra-thin sendust flake powder, characterized in that: The method comprises: Step 1: Atomization The alloy material containing Sendust is melted into alloy steel liquid by medium frequency induction or arc induction. The steel liquid flows out through a flow restriction with a diameter of 3-8 mm and is atomized by high-pressure nitrogen / argon gas. Step 2: Condensation The atomized molten steel droplets are sprayed onto the surface of a high-speed rotating copper roller or copper disk, and are rapidly solidified to form flaky powder; Step 3: Annealing and screening The flaky powder is annealed under nitrogen / argon protection; and is classified and sieved according to particle size requirements to obtain ultra-thin sendust flake powder.

2. The method for preparing ultra-thin Sendust flake powder according to claim 1, wherein: In the step 1, the alloy material containing sendust has a silicon content of 9.7-10.1 wt%, an aluminum content of 5.6-6.0 wt%, and a silicon-aluminum atomic ratio of 1.6-1.

8.

3. The method for preparing ultra-thin Sendust flake powder according to claim 1, wherein: In the step 1, the atomization parameters are a carrier gas pressure of 2-6 MPa and a gas flow rate of 600-2000 Nm 3 / h, and control the atomized droplet diameter to 5-40 microns.

4. The method for preparing ultra-thin Sendust flake powder according to claim 1, wherein: In the step 2, the rotation speed of the copper roller or copper plate is 500-1000 rpm, and the cooling rate of the rapid cooling water cooling system is 10 6 -10 7 K / s.

5. The method for preparing ultra-thin Sendust flake powder according to claim 1, wherein: In the step 2, the flake powder has a thickness of 100-400 nanometers, a flake diameter of 10-70 micrometers, an diameter-to-thickness ratio of 200-400:1, and a surface roughness Ra of less than 0.1 μm.

6. The method for preparing ultra-thin Sendust flake powder according to claim 1, wherein: In the step 3, the annealing temperature is 450-750° C., the heating rate is 3-5° C. / min, and the holding time is 1-3 hours.

7. The method for preparing ultra-thin Sendust flake powder according to claim 1, wherein: In the step 3, the annealed powder is screened for particle size by air flow classification or vibrating screen, and the classification accuracy D90 deviation is less than 5%.

8. The method for preparing ultra-thin Sendust flake powder according to claim 7, wherein: The air flow velocity of the air flow classification is 10-30 m / s.

9. The method for preparing ultra-thin Sendust flake powder according to claim 1, wherein: In the step 3, the oxygen content of the ultra-thin sendust flake powder is less than 800 ppm, and the reflection loss in the frequency band of 2-18 GHz is less than or equal to -30 dB.

10. An ultra-thin sendust flake powder, characterized in that: The flaky powder is prepared by the method according to any one of claims 1 to 9.

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