Preparation method of low-magnetic-loss nanocrystalline powder

Abstract

The invention discloses a preparation method of low-magnetic-loss nanocrystal powder, and relates to an industrial preparation method of low-magnetic-loss nanocrystal powder, which is characterized in that the spray state of spray powder is amorphous, and the spray powder is amorphous and nanocrystal after vacuum crystallization heat treatment, and is different from a laboratory small-batch spray preparation method. The prepared powder is completely amorphous in a spray state; the prepared powder subjected to vacuum crystallization heat treatment has the advantages that the saturation flux density is larger than 1.24 T, the coercive force is lower than 30 A / m, the particle size D50 of the powder is 3-15 microns, and the magnetic loss is low. The preparation method belongs to the field of nanocrystalline soft magnetic powder material preparation.

Description

Technical Field

[0001] This invention relates to an industrial-scale preparation method for a low-magnetic-loss nanocrystalline powder that is amorphous in the sprayed state and becomes amorphous with nanocrystalline structure after vacuum crystallization heat treatment. Unlike laboratory small-batch spray preparation methods, this method uses industrially pure raw materials, and the prepared powder is completely amorphous in the sprayed state. The prepared powder has a saturation magnetic induction intensity greater than 1.24T, a coercivity less than 30A / m, good powder particle sphericity, and a small powder size D. 50 Within the range of 3 to 15 μm, it has the advantage of low magnetic loss. This invention belongs to the field of preparation of nanocrystalline soft magnetic powder materials. Background Technology

[0002] With the development of artificial intelligence, the workload of offline and cloud-based intelligent computing will increase dramatically. Furthermore, as the pressure of global warming intensifies, the energy consumption of related electrical appliances fails to meet the requirements of green development. Therefore, there is an urgent need for low-magnetic-loss nanocrystalline powder materials. These low-magnetic-loss powder materials, after being insulated and coated with inorganic and organic materials, are used to prepare nanocrystalline composite soft magnetic materials. These materials are then molded to create magnetic devices required in high-tech fields, satisfying numerous applications where nanocrystalline ribbons are not feasible. Examples include micro inductors for 5G communication power supplies, photovoltaic power supply inductors, and low-magnetic-loss soft magnetic stators for new energy vehicles.

[0003] Existing supersonic atomization methods include gas atomization and water atomization. Gas-atomized powders have better sphericity, which is convenient for insulating coating. However, the powder size of gas-atomized powders is relatively large, generally 53–150 μm. Compared with the preparation method of nanocrystalline rapid quenching thin strips, the preparation of nanocrystalline magnetic powder has its own bottlenecks. The cooling rate of existing gas atomization solidification technology is 2–3 orders of magnitude lower than that of rapid quenching solidification thin strips. Alloys of the same composition are more difficult to obtain completely amorphous in the spray state. Generally, the powder surface has a large number of inclusions and unwanted crystalline structures, resulting in poor coercivity, high coercivity value, and high magnetic loss of the powder. Among them, gas atomization is further divided into vacuum melting inert gas atomization and atmospheric melting gas atomization. However, whether it is vacuum melting inert gas atomization or atmospheric melting gas atomization, existing soft magnetic metal materials with a saturation magnetic induction intensity greater than 1.24T have the characteristics of large powder size, the powder spray state is not completely amorphous, it contains inclusions and crystalline structures, and the coercivity of the powder is deteriorated, which ultimately leads to excessive magnetic loss of the soft magnetic powder core.

[0004] The solidification and cooling rate of water-atomized powder is significantly improved, approaching that of rapidly quenched solidified thin strips. However, the sphericity of water-atomized powder is poor, which is not conducive to insulating coating. The density of the powder-formed magnetic powder core is low, and the magnetic permeability of the magnetic powder core decreases, preventing the magnetic potential of the atomized powder from being fully utilized. Furthermore, the high oxygen content of water-atomized powder results in high coercivity, which is detrimental to reducing magnetic loss in the magnetic powder core. It is particularly noteworthy that the coercivity of nanocrystalline soft magnetic powder prepared by existing technologies is poor, generally ranging from 17.6 to 34.1 Oe (1401.0 to 2714.4 A / m). The coercivity of the nanocrystalline powder prepared by the invention patent publication number CN115608996A is significantly improved, reaching 2.1 to 3.7 Oe (167.2 to 294.5 A / m).

[0005] In 1988, Yoshizawa et al. developed a FeSiBNbCu rapidly quenched amorphous alloy. Annealing yielded an alloy with nanocrystals dispersed in an amorphous matrix, designated Finemet, with a representative composition of Fe73.5-Si13.5-B9-Cu1-Nb3at%. This alloy exhibits a coercivity as low as 0.6 A / m and as high as 10 A / m. 5 While it possesses high permeability, its saturation magnetic induction intensity is only 1.24T or less, which is insufficient to meet the development needs of miniaturization, high power, and high current in high-tech new high-performance electronic devices. Therefore, there is an urgent need for nanocrystalline soft magnetic materials with high saturation magnetic induction intensity.

[0006] The invention of nanocrystalline rapidly quenched soft magnetic materials with higher saturation magnetic induction (greater than 1.24T) and low coercivity has attracted the attention of numerous experts and scholars in materials science and physics, who have conducted extensive laboratory research, innovation, and continuous problem-solving, resulting in numerous research papers and patents. Simultaneously, it has attracted the attention of the materials industry, with experts in the field undertaking significant research and development and process innovation, publishing numerous patents and technical papers. This superior soft magnetic material has attracted the eager anticipation of many electronic device engineers and enterprise engineers who can apply it. However, more than thirty years later, high-performance nanocrystalline rapidly quenched soft magnetic materials have still not been industrialized, despite possessing saturation magnetic induction greater than 1.24T, coercivity less than 3.0 A / m, and powder particle size exceeding D... 50 Powders with nanocrystals smaller than 53 μm, low magnetic loss, and good sphericity are more difficult to prepare.

[0007] What is the key obstacle preventing the industrialization of high-performance nanocrystalline soft magnetic materials? Through long-term research, we have found that the reason for this failure lies in the following: During industrial-scale rapid quenching, a 100% amorphous structure cannot be obtained. Coarse solidification crystallization occurs on the free surface of the rapid quenching zone. This solidification crystallization results in increased coercivity, significantly increased magnetic loss, and a marked deterioration in the magnetic properties of the soft magnetic material after annealing. While high-purity raw materials may prevent the occurrence of free-surface solidification crystallization, industrial-purity raw materials will inevitably produce it. For industrial production, the price of high-purity raw materials is unacceptable. Furthermore, even with high-purity raw materials, the microstructure and properties of the rapidly quenched thin strips are unstable during industrial production, with excessive fluctuations in magnetic properties. Even when using industrially pure raw materials, although some samples exhibit a saturation magnetic induction greater than 1.24T, the excessively high coercivity and magnetic loss at the operating frequency of the rapidly quenched thin strips severely negate the beneficial effects of the high saturation magnetic induction of the nanocrystalline material. Using industrially pure raw materials to prepare high-saturation magnetization, low-magnetic-loss nanocrystalline powder with good sphericity is even more impossible in industrial-scale production.

[0008] The patent specification in authorization announcement number CN106636982B also points out that the properties of amorphous alloy melts are greatly affected by trace elements. Certain high-temperature refractory particulate impurities act as heterogeneous nucleation sites during solidification, easily inducing crystallization and significantly reducing the amorphous alloy's ability to form. Due to the large variety and complex interactions of trace elements, it is even difficult to distinguish which are beneficial elements and which are harmful impurities. This is almost the reason why thousands of patented new alloy compositions are currently difficult to produce.

[0009] In this invention patent application, through long-term and extensive research, we discovered that nanocrystalline rapidly quenched soft magnetic alloys with high saturation magnetic induction are a very special type of material. The invention patent, based on laboratory process conditions and experimental results using high-purity raw materials, cannot achieve the results described in the patent in industrial production using industrially pure raw materials and industrial processing methods. This is because the rapid quenching solidification technology used in the preparation of this type of nanocrystalline soft magnetic alloy, using industrially pure raw materials, cannot obtain a 100% amorphous structure in the rapidly quenched state; using existing gas atomization methods, due to the reduced cooling rate, it is even more difficult to obtain a completely amorphous structure; using the new invention patent, the soft magnetic alloy prepared by water atomization can obtain a completely amorphous structure, but the powder sphericity is poor, the powder size is large, and especially the coercivity of the powder is 1-2 orders of magnitude higher than that of similar alloy nanocrystalline rapidly quenched thin strips, resulting in excessive magnetic loss of the nanocrystalline soft magnetic powder.

[0010] Therefore, an industrial-scale preparation method for low-magnetic-loss nanocrystalline powder was developed. Using industrially pure raw materials, the prepared powder exhibits complete amorphous properties in the spray state. The prepared powder possesses a saturation magnetic induction greater than 1.24 T, a coercivity less than 30 A / m, good sphericity, and a small particle size D. 50 In the range of 3–15 μm, it has the advantage of low magnetic loss, which meets the urgent need of high-tech fields for soft magnetic powder with high saturation magnetic induction intensity and low magnetic loss. It is challenging and has important engineering significance. Summary of the Invention

[0011] A method for preparing low magnetic loss nanocrystalline powder, step 1: using industrial pure raw materials, industrial pure iron, industrial pure ferrosilicon, industrial pure copper, industrial pure graphite, etc., are placed into the crucible of a medium-frequency induction vacuum melting furnace; 0.20-0.80 wt% of additional industrial pure graphite, equal to the total weight of industrial ferroboron and alloy materials, is added to the charging hopper inside the melting furnace. The additional industrial pure graphite is evenly divided into 2-8 parts, each part is counterweighted with small pieces of industrial pure iron, and the weight of the counterweighting industrial pure iron is equal to the weight of the additional industrial pure graphite. Seven times the weight of industrial pure copper sheets are used to wrap industrial pure graphite into a batch. 1-6 batches of industrial pure graphite are placed separately in one feeding hopper compartment; 1-2 batches of industrial pure graphite are placed in the same compartment of the feeding hopper as industrial ferroboron. The total weight of industrial pure iron (plus counterweight), industrial pure ferrosilicon, industrial ferroboron, industrial pure copper, industrial pure copper sheets, and industrial pure graphite are all designed and proportioned according to their alloy compositions. Graphite in the industrial pure graphite batch is added separately. Step 2: First, vacuum the container to achieve 10... -4 ~10 -1 After Pa, the medium-frequency induction power supply is started to bake the raw materials inside the crucible, while the raw materials in the feeding hopper are baked simultaneously. The baking temperature is controlled within 300-800℃. During baking, the vacuum degree is maintained within 8-200Pa by adjusting the power supply magnitude, power supply speed, and vacuum unit pumping speed, and the baking time is 5-45 minutes. Vacuuming continues until the vacuum reaches 10 Pa. -2 ~10 -1 Step 3: Heat and melt the ingredients in the crucible until the mixture is clear, then evacuate until the vacuum level reaches 10 Pa; -4Refining 1 begins at ~8Pa and maintains this vacuum level for 5-30 minutes; Step 4: In refining 2, 1-6 packages of industrial pure graphite feedstock from the hopper are added to the crucible in batches to refine the alloy solution in the crucible. The molten temperature is controlled by a combination of three measures: vacuuming with a vacuum unit, opening and closing vacuum valves, adjusting the power supply to maintain the molten temperature 50-150°C above the alloy melting point, and controlling the rate of addition of the industrial pure graphite feedstock. These measures achieve soft boiling of the molten solution without splashing and control the furnace pressure within 130-5000Pa; Once the alloy solution surface is basically calm, the pressure in the melting furnace is then steadily controlled to 40-130Pa and maintained at 40-130Pa for 5-30 minutes; Step 5: Refining 3 continues, using a vacuum unit to... The vacuum level and the opening and closing of the vacuum valves, along with adjustments to the power supply, are used to control the molten liquid temperature at 50–150°C above the alloy melting point. The vacuum level inside the furnace is controlled at 5–38 Pa for 5–15 minutes to ensure the molten liquid reaches a soft boil without splashing. Step 6: Industrial ferroboron and the remaining industrial pure graphite feed bag are then added to the crucible simultaneously. The vacuum unit is used to evacuate the furnace, and the vacuum valves are opened and closed, while the power supply is adjusted to control the molten liquid temperature at 50–150°C above the alloy melting point. These two combined measures stabilize the furnace pressure from 130–5000 Pa to 40–130 Pa, achieving the clearing of the industrial ferroboron and ensuring the molten liquid reaches a soft boil without splashing. The pressure is maintained at 40–130 Pa for 2–5 minutes, followed by purging with 0.11–0.12MPa protection; Step 7: After argon purging, prepare for combined supersonic atomization and rotary ultrafine atomization for ultrafine powder production: Before spraying, the temperature of the alloy melt in the crucible is temporarily adjusted to 100-250℃ above the melting point; the crucible melting chamber, the spray chamber equipped with the supersonic atomizing nozzle and the ultrafine centrifugal atomizing rotary disk, and the powder cooling chamber are arranged from top to bottom, and all three chambers are within a vacuum system; the ultrafine centrifugal atomizing rotary disk is composed of a low thermal conductivity non-metallic material on the disk surface in contact with the supersonic atomizing droplets and a metallic material on the disk substrate. The axis of the ultrafine centrifugal atomizing rotary disk is parallel to but does not coincide with the center line of the supersonic atomization nozzle. The disk surface of the ultrafine centrifugal atomizing rotary disk is conical, with the lowest point near the disk axis and the highest point at the disk edge. The radius of the disk surface is... The angle with the horizontal plane is 1-5°; the vertical distance between the edge of the turntable and the lower end face of the supersonic atomizing nozzle is 10-49mm; the turntable speed is adjusted so that the spray droplets are quickly broken into fine droplets on the turntable surface, and the flight speed reaches 30-300m / s when the centrifugal motion leaves the edge of the turntable; after spraying, the infrared temperature monitoring point is quickly switched to aim at the center of the fine droplet area that has just left the edge of the turntable, and the power of the intermediate frequency induction power supply is controlled to indirectly control the temperature of the liquid alloy in the crucible, so as to control the center temperature of the fine droplet area that has just left the edge of the turntable to be 10-250℃ above the melting point of the alloy; the horizontal dimension of the droplet flight trajectory is 1500-15000mm; in the initial stage of the centrifugal flight process, the droplets are dispersed into finer droplets. From this point until the finer droplets reach the inner wall of the atomizing chamber, the centrifugal flight is the rapid solidification stage, during which the finer droplets complete rapid solidification. The argon supersonic spray pressure is 2.0–4.0 MPa higher than the argon pressure inside the spray chamber. High-speed circulation forced heat exchange cooling is used for the argon in the spray chamber and powder cooling chamber. At the outlets of the spray chamber and powder cooling chamber, the argon is subjected to extraction, forced cooling, purification, pressurization, and circulation. One path supplies the nozzle gas inlet, another path supplies the nozzle above the cooling gas curtain during the rapid solidification stage of the finer droplets in the atomizing chamber, and a third path supplies the nozzle at the powder-tumbling area in the powder cooling chamber. Throughout the spraying process, the argon supplied to the nozzle gas inlet and nozzle inlet is controlled via these three circulation paths. The air temperature is below 200℃. During the rapid solidification stage of the finer droplets' centrifugal flight, within the flight airspace starting from a horizontal distance of 500-2000mm from the edge of the turntable and ending at the double-layered water-cooled inner wall of the spray chamber in the flight direction, the finer droplets are continuously blown by a multi-nozzle cooling curtain of argon gas that has undergone forced circulation cooling during the spraying process. The argon gas pressure is 0.10-0.25MPa higher than the air pressure in the spray chamber. Below the endpoint of the finer droplets' flight is the powder cooling chamber, where the powder settles after the flight ends. The powder in the powder cooling chamber is continuously stirred, tumbled, and blown by a multi-nozzle spray of argon gas that has undergone forced circulation cooling. The argon gas pressure is 0.10-0.25MPa higher than the air pressure in the powder cooling chamber.At 25 MPa, the powder in contact with the inner wall of the cooling chamber during the stirring and turning process is cooled by the double-layer water-cooled inner wall until the powder temperature reaches 5-20°C above room temperature; Step 8: After the powder in the cooling chamber is cooled to room temperature, the powder is transferred to the cyclone classification chamber, first evacuated to below 1 Pa, and then nitrogen cyclone classification is performed to determine the particle size D of the spray-dried powder. 50 The powder size is 3-15μm. After classification, the powder is first vacuumed at 1Pa and then encapsulated with nitrogen. Step 9: According to the operating frequency of the device to which the powder is applied, the finer the powder size after classification should be selected. For frequencies of 50Hz-3MHz, select the corresponding D. 50 The powder is 15-3μm thick; then the powder is inorganically and organically insulated and then pressure-formed into a magnetic powder core; Step 10: First, the magnetic powder core is vacuum crystallized and heat-treated, and then the magnetic properties of the magnetic powder core are measured.

[0012] In step 1 of the preparation method of low magnetic loss nanocrystalline powder of the present invention, the alloy composition at% of the sprayed powder is Fe. a Si b B c M d Cu e C f , 75.0≤a≤82.0, 3.0≤b≤13.0, 10.5≤e≤16.5, 1.0≤d≤2.0, 0.5≤e≤1.5, 0.010≤f≤0.020, a+b+c+d+e=100at%; where M is at least one of Nb, Ti, Zr, Hf, Mo, and W, the composition range of at least one of Mo and W is 0.50~1.50, and the composition range of at least one of Nb, Ti, Zr, and Hf is 0.15~0.50; the oxygen content of the sprayed powder alloy is less than 100ppm.

[0013] The characteristic of step 7 of the preparation method of low magnetic loss nanocrystalline powder of the present invention is that the low thermal conductivity non-metallic material of the surface of the ultrafine centrifugal atomizing turntable is zirconium oxide.

[0014] The present invention provides a method for preparing low magnetic loss nanocrystalline powder, characterized in that: other alloys are first vacuum melted and refined, and then subjected to a combination of supersonic atomization and rotary ultrafine atomization as described in step 7, followed by cyclone classification as described in step 8. This method can produce other alloy powders that are finer than those prepared by existing supersonic atomization methods. 50 It reaches 3-15μm.

[0015] Compared with existing methods for preparing high-magnetic-performance nanocrystalline soft magnetic powders, the present invention has the following advantages:

[0016] 1) The soft magnetic powder spray can be prepared using only industrial pure raw materials and has a completely amorphous structure.

[0017] 2) The prepared soft magnetic powder particles have good sphericity, are fine, and have a small particle size D. 50 Between 3 and 15 μm.

[0018] 3) The prepared nanocrystalline powder not only has a saturation magnetic induction intensity higher than 1.24T, but also has excellent coercivity, with powder coercivity lower than 30A / m.

[0019] 4) The prepared nanocrystalline powder has low magnetic loss. Detailed Implementation

[0020] Example 1

[0021] This invention discloses a method for preparing low magnetic loss nanocrystalline powder, wherein step 1 involves dispensing Fe... 77.79 Si 3.0 B 16.5 Nb 0.50 Mo 1.50 Cu 0.7 C 0.010 The alloy composition atomic percentage is 500 kg, all using industrially pure raw materials. Step 1: Using industrially pure raw materials, place the industrially pure iron, industrially pure ferrosilicon, industrially pure copper, and industrially pure graphite from the batch into the crucible of a medium-frequency induction vacuum melting furnace; In the charging hopper of the melting furnace, add industrial ferroboron and 0.20 wt% of additional industrially pure graphite, wherein the additional industrially pure graphite is evenly divided into 2 parts, each part is counterweighted with a small piece of industrially pure iron, the weight of which is... Seven times the amount of industrial pure graphite is packaged with industrial pure copper sheets to form an industrial pure graphite feed bag. One industrial pure graphite feed bag is placed separately in one feeding hopper compartment; one industrial pure graphite feed bag is placed in the same compartment of the feeding hopper as industrial ferroboron. Among them, the total weight of industrial pure iron (plus counterweight), industrial pure ferrosilicon, industrial ferroboron, industrial pure copper and industrial pure copper sheets, and industrial pure graphite are respectively designed and formulated according to alloy composition. Graphite in the industrial pure graphite feed bag is added separately. Step 2: First, vacuum is applied until 10 -4 After Pa, the medium-frequency induction power supply is started to bake the raw materials inside the crucible, while the raw materials in the feeding hopper are baked simultaneously. The baking temperature is controlled within 800℃. During the baking period, the vacuum degree is maintained within 200Pa by adjusting the power supply magnitude, power supply speed, and vacuum unit pumping speed. The baking time is 45 minutes. Vacuuming continues until the vacuum reaches 10 Pa. -2 Step 3: Heat and melt the ingredients in the crucible until the mixture is clear, then evacuate until the vacuum level reaches 10 Pa; -4Step 1: Refining begins at Pa, and this vacuum level is maintained for 30 minutes. Step 4: In refining 2, one package of industrial pure graphite feedstock from the hopper is added to the crucible to refine the alloy solution in the crucible. The temperature of the melt is controlled at 150°C above the alloy melting point by using a vacuum unit to evacuate the furnace, opening and closing the vacuum valves, and adjusting the power supply. These two combined measures achieve soft boiling of the melt without splashing and control the furnace pressure within 5000 Pa. After the alloy solution surface is basically calm, the pressure in the melting furnace is then steadily controlled to 40 Pa and maintained at 40 Pa for 30 minutes. Step 5: Refining 3 continues, using a vacuum unit to evacuate the furnace, opening and closing the vacuum valves, and adjusting the power supply to control the temperature of the melt above the alloy melting point. Step 6: Then, simultaneously add industrial ferroboron and the remaining industrial pure graphite feed bag to the crucible. Vacuum the furnace at 150℃, control the vacuum degree at 5Pa, and hold for 5 minutes to ensure the molten liquid reaches a soft boil without splashing. Using a vacuum unit to evacuate and control the vacuum valves, and adjusting the power supply, control the molten liquid temperature to 150℃ above the alloy melting point. These two combined measures stabilize the furnace pressure from 5000Pa to 40Pa, achieving industrial ferroboron purification and ensuring the molten liquid reaches a soft boil without splashing. Hold at 40Pa for 2 minutes, then purge with argon at 0.11MPa for protection. Step 7: After argon purging, prepare for supersonic atomization combined with rotary ultrafine atomization for ultrafine powder production: Before atomization, temporarily adjust the temperature of the alloy molten liquid in the crucible. The temperature is controlled to be 100°C above the melting point; the crucible melting chamber, the spray chamber equipped with a supersonic atomizing nozzle and an ultrafine centrifugal atomizing disc, and the powder cooling chamber are arranged from top to bottom, and all three chambers are within a vacuum system; the ultrafine centrifugal atomizing disc is composed of zirconium oxide, a low thermal conductivity non-metallic material that contacts the supersonic atomizing droplets, and high-strength stainless steel for the disc substrate. The axis of the ultrafine centrifugal atomizing disc is parallel to but does not coincide with the center line of the supersonic atomization nozzle. The disc surface is conical, with the lowest point near the disc axis and the highest point at the edge. The angle between the radial direction of the disc surface and the horizontal plane is 5°; the vertical distance between the edge of the disc and the lower end face of the supersonic atomizing nozzle is 49mm; the disc rotation speed is adjusted to ensure that the sprayed droplets are... The liquid rapidly breaks into fine droplets on the disk surface, and the centrifugal motion causes the droplets to reach a speed of 300 m / s as they detach from the edge of the disk. After spraying, the infrared temperature monitoring point is quickly switched to aim at the center of the fine droplet region just after it leaves the edge of the disk. The power of the intermediate frequency induction power supply is controlled to indirectly control the temperature of the liquid alloy in the crucible, ensuring that the center temperature of the fine droplet region just after it leaves the edge of the disk is controlled 10°C above the alloy melting point. The horizontal dimension of the droplet flight trajectory is 1500 mm. In the initial stage of the centrifugal flight, the droplets disperse into even finer droplets. From this point until the finer droplets reach the inner wall of the atomizing chamber, the centrifugal flight is a rapid solidification stage, during which the finer droplets complete rapid solidification. The argon supersonic spray pressure is 4 mmol higher than the argon pressure in the spray chamber.0MPa; Argon gas in the spray chamber and powder cooling chamber is cooled by high-speed circulation forced heat exchange. Argon gas at the spray chamber outlet and powder cooling chamber outlet is subjected to extraction, forced cooling, purification, pressurization, and circulation. One supply line is given to the nozzle gas inlet, another to the nozzle above the cooling gas curtain during the rapid solidification stage of the finer droplets in the atomization chamber, and a third to the nozzle at the powder-tumbling area in the powder cooling chamber. Throughout the spraying process, the argon gas temperature supplied to the nozzle and nozzle inlets via these three circulation lines is controlled to be below 200℃. During the rapid solidification stage of the finer droplets' centrifugal flight, within the flight airspace starting 500mm horizontally from the edge of the turntable and ending at the double-layered water-cooled inner wall of the spray chamber in the flight direction, argon gas is continuously supplied via... Finer droplets are blown through a multi-nozzle cooling curtain of argon gas under forced circulation cooling, with the argon pressure 0.25 MPa higher than the spray chamber pressure. Below the endpoint of the finer droplets is the powder cooling chamber, where the powder settles after flight. The powder in the powder cooling chamber is continuously stirred, tumbled, and blown through the multi-nozzle cooling curtain of argon gas under forced circulation cooling, with the argon pressure 0.25 MPa higher than the powder cooling chamber pressure. During stirring and tumbling, the powder in contact with the inner wall of the cooling chamber is cooled by the double-layer water-cooled inner wall until the powder temperature reaches 5-20°C above room temperature. Step 8: After the powder in the cooling chamber cools to room temperature, the powder is transferred to the cyclone classification chamber, first evacuated to below 1 Pa, and then classified by nitrogen cyclone to determine the particle size D of the spray-dried powder. 50 The powder is 15μm in size. After classification, the powder is first vacuumed at 1Pa and then encapsulated with nitrogen. Step 9: Prepare the powder application device with a working frequency of 200kHz. The powder is inorganically and organically insulated and then pressure-formed into a magnetic powder core. Step 10: First, vacuum crystallize and heat-treat the magnetic powder core, and then measure the magnetic properties of the magnetic powder core.

[0022] The nanocrystalline soft magnetic powder exhibits a saturation magnetic induction of 1.73 T and a coercivity of 3.9 A / m; under conditions of 200 kHz and 0.05 T, the magnetic loss of the powder core is 251 mW / cm². 3 .

[0023] Example 2

[0024] This invention discloses a method for preparing low magnetic loss nanocrystalline powder, wherein step 1 involves dispensing Fe... 75.78 Si 11.0 B 10.5 Nb 0.50 Zr 0.5 0Mo 1.00 Cu 0.7 C 0.020The alloy composition atomic percentage is 500 kg, all using industrially pure raw materials. Step 1: Using industrially pure raw materials, place the industrially pure iron, industrially pure ferrosilicon, industrially pure copper, and industrially pure graphite from the batch into the crucible of a medium-frequency induction vacuum melting furnace; In the charging hopper of the melting furnace, add industrial ferroboron and 0.80 wt% of additional industrially pure graphite, wherein the additional industrially pure graphite is evenly divided into 8 parts, each part is counterweighted with small pieces of industrially pure iron, and the weight of the counterweighting industrially pure iron is [not specified in the original text]. Seven times the amount of industrial pure graphite, wrapped in industrial pure copper sheets, constitutes an industrial pure graphite feed package. Six feed packages are placed separately in one feeding hopper compartment; two feed packages are placed in the same compartment of the feeding hopper as industrial ferroboron. The total weight of industrial pure iron (plus counterweight), industrial pure ferrosilicon, industrial ferroboron, industrial pure copper and industrial pure copper sheets, and industrial pure graphite are all formulated according to their alloy compositions. Graphite in the industrial pure graphite feed package is added separately. Step 2: First, vacuum the system to achieve 10... -1 After Pa, the medium-frequency induction power supply is started to bake the raw materials inside the crucible, while the raw materials in the feeding hopper are baked simultaneously. The baking temperature is controlled within 700℃. During the baking period, the vacuum level is maintained within 8 Pa by adjusting the power supply magnitude, power supply speed, and vacuum unit pumping speed. The baking time is 5 minutes. Vacuuming continues until the vacuum reaches 10 Pa. -2 Step 3: Heat and melt the ingredients in the crucible until the mixture is clear, then evacuate until the vacuum level reaches 10 Pa; -1Step 1: Refining begins at Pa, and this vacuum level is maintained for 30 minutes. Step 4: In refining 2, one package of industrial pure graphite feedstock from the hopper is added to the crucible in batches to refine the alloy solution in the crucible. The molten liquid temperature is controlled by three combined measures: vacuuming with the vacuum unit, opening and closing the vacuum valves, adjusting the power supply to maintain the molten liquid temperature 100°C above the alloy melting point, and controlling the addition rate of the industrial pure graphite feedstock. These measures achieve soft boiling of the molten liquid without splashing and keep the furnace pressure below 5000 Pa. Once the alloy solution surface is basically calm, the furnace pressure is then steadily controlled to 130 Pa and maintained at 130 Pa for 30 minutes. Step 5: Refining 3 continues, using the vacuum unit to vacuum, opening and closing the vacuum valves, and adjusting the power supply... Step 6: Then, simultaneously add industrial ferroboron and the remaining industrial pure graphite feed bag to the crucible. Vacuuming is controlled at 38 Pa for 15 minutes to ensure the melt reaches a soft boil without splashing. These two combined measures—vacuuming with a vacuum unit, opening and closing vacuum valves, and adjusting power supply—stable the melt temperature at 150°C above the alloy melting point. This reduces the furnace pressure from 5000 Pa to 130 Pa, achieving industrial ferroboron treatment and ensuring the melt reaches a soft boil without splashing. The pressure is maintained at 130 Pa for 5 minutes, followed by argon purging at 0.11 MPa for protection. Step 7: After argon purging, prepare for supersonic atomization combined with rotary ultrafine atomization for ultrafine powder production: [The text abruptly ends here, likely due to an incomplete translation or source material.] The temperature of the molten alloy in the crucible is temporarily adjusted to 250°C above its melting point. The crucible melting chamber, the spray chamber equipped with a supersonic atomizing nozzle and an ultrafine centrifugal atomizing disc, and the powder cooling chamber are arranged from top to bottom, all within a vacuum system. The ultrafine centrifugal atomizing disc is composed of zirconium oxide, a low-thermal-conductivity non-metallic material that contacts the supersonic atomized droplets, and high-strength stainless steel as the disc substrate. The axis of the ultrafine centrifugal atomizing disc is parallel to but does not coincide with the center line of the supersonic atomization nozzle. The disc surface is conical, with the lowest point near the disc axis and the highest point at the edge. The angle between the disc radius and the horizontal plane is 1°. The vertical distance between the edge of the disc and the lower end face of the supersonic atomizing nozzle is 10mm. The disc rotation speed is adjusted to... The spray droplets rapidly break into fine droplets on the disk surface. As they detach from the disk edge via centrifugal motion, their flight speed reaches 100 m / s. After spraying, the infrared temperature monitoring point quickly shifts to aim at the center of the fine droplet region just outside the disk edge. The power of the intermediate frequency induction power supply is controlled, indirectly regulating the temperature of the liquid alloy inside the crucible, ensuring that the center temperature of the fine droplet region just outside the disk edge is controlled 250°C above the alloy's melting point. The horizontal dimension of the droplet flight trajectory is 15000 mm. In the initial stage of centrifugal flight, the droplets disperse into even finer droplets. From this point until the finer droplets reach the inner wall of the atomization chamber, the centrifugal flight is a rapid solidification stage, during which the finer droplets complete rapid solidification. The argon supersonic spray pressure is 2 times higher than the argon pressure inside the spray chamber.0MPa; Argon gas in the spray chamber and powder cooling chamber is cooled by high-speed circulation forced heat exchange. Argon gas at the spray chamber outlet and powder cooling chamber outlet is subjected to extraction, forced cooling, purification, pressurization, and circulation supply. One supply line is given to the nozzle gas inlet, another to the nozzle above the cooling gas curtain during the rapid solidification stage of the finer droplets in the atomization chamber, and a third to the nozzle at the powder-tumbling area in the powder cooling chamber. Throughout the spraying process, the argon gas temperature supplied to the nozzle and nozzle inlets via these three circulation lines is controlled to be below 200℃. During the rapid solidification stage of the finer droplets' centrifugal flight, within the flight airspace starting 2000mm horizontally from the edge of the turntable and ending at the double-layered water-cooled inner wall of the spray chamber in the flight direction, argon gas is continuously supplied during the spraying process. Finer droplets are blown through a multi-nozzle cooling air curtain of argon gas, which has undergone forced circulation cooling. The argon gas pressure is 0.10 MPa higher than the air pressure in the spray chamber. Below the endpoint of the finer droplets is the powder cooling chamber, where the powder settles after flight. The powder in the powder cooling chamber is continuously stirred, tumbled, and blown through the tumbled powder with multi-nozzle cooling argon gas, which has undergone forced circulation cooling. The argon gas pressure is 0.10 MPa higher than the air pressure in the powder cooling chamber. During the stirring and tumbling process, the powder in contact with the inner wall of the cooling chamber is cooled by the double-layer water-cooled inner wall until the powder temperature reaches 5°C above room temperature. Step 8: After the powder in the cooling chamber has cooled to room temperature, the powder is transferred to the cyclone classification chamber. First, a vacuum is drawn to below 1 Pa, and then nitrogen cyclone classification is performed to determine the particle size D of the spray-dried powder. 50 The powder is 3μm in size. After classification, the powder is first vacuumed at 1Pa and then encapsulated with nitrogen. Step 9: Prepare the powder application device with a working frequency of 3MHz. The powder is inorganically and organically insulated and then pressure-formed into a magnetic powder core. Step 10: First, vacuum crystallize and heat-treat the magnetic powder core, and then measure the magnetic properties of the magnetic powder core.

[0025] The nanocrystalline soft magnetic powder exhibits a saturation magnetic induction of 1.71 T and a coercivity of 2.4 A / m; under conditions of 3 MHz and 0.01 T, the magnetic loss of the powder core is 437 mW / cm². 3 .

[0026] Comparative Example 1

[0027] The alloy composition is the same as in Example 1, consisting of Fe. 77.80 Si 3.0 B 16.5 Nb 0.50 Mo 1.50 Cu 0.7 Industrial-grade pure raw materials were used, but the existing vacuum melting and argon spraying method was employed. The raw materials were placed together in a crucible for melting, and after clearing, allowed to stand for 15 minutes. The melt was then sprayed at 250°C, followed by vacuum crystallization, pressing into magnetic powder cores, and measuring magnetic properties. Soft magnetic powder D 50With a diameter of 92 μm, a saturation magnetic induction of 1.43 T, a coercivity of 517 A / m, and a magnetic loss of 956 mW / cm² under conditions of 200 kHz and 0.05 T, the magnetic powder core exhibits a magnetic loss of 956 mW / cm². 3 .

Claims

1. A method for preparing low magnetic loss nanocrystalline powder, characterized in that: 1) Step 1: Using industrially pure raw materials, place the industrially pure iron, industrially pure ferrosilicon, industrially pure copper, and industrially pure graphite from the batch into the crucible of a medium-frequency induction vacuum melting furnace; add 0.20–0.80 wt% of industrial ferroboron and alloy batch total weight of additional industrially pure graphite to the charging hopper inside the melting furnace. The additional industrially pure graphite is evenly divided into 2–8 portions, each portion being counterweighted with small pieces of industrially pure iron, the weight of which is equal to the weight of the additional industrially pure graphite. Seven times the weight of industrial pure copper sheets are used to form industrial pure graphite feed packages. 1 to 6 portions of industrial pure graphite feed packages are placed separately in one feeding hopper compartment. 1 to 2 portions of industrial pure graphite feed packages are placed in the same compartment of the feeding hopper as industrial ferroboron. Among them, the total weight of industrial pure iron, industrial pure ferrosilicon, industrial ferroboron, industrial pure copper and industrial pure copper sheets, and industrial pure graphite are respectively designed and formulated according to alloy composition. Graphite in the industrial pure graphite feed package is added separately. 2) Step 2: First, create a vacuum until it reaches 10. -4 ~10 -1 After Pa, the medium-frequency induction power supply is started to bake the raw materials inside the crucible, while the raw materials in the feeding hopper are baked simultaneously. The baking temperature is controlled within 300-800℃. During baking, the vacuum degree is maintained within 8-200Pa by adjusting the power supply magnitude, power supply speed, and vacuum unit pumping speed, and the baking time is 5-45 minutes. Vacuuming continues until the vacuum reaches 10 Pa. -2 ~10 -1 Pa; 3) Step 3: Heat and melt the ingredients in the crucible, then evacuate until the vacuum level reaches 10. -4 Refining begins at ~8Pa and this vacuum level is maintained for 5 to 30 minutes; 4) Step 4: In refining step 2, add 1 to 6 packages of industrial pure graphite feedstock from the hopper to the crucible in batches. The alloy solution in the refining crucible is controlled by three combined measures: vacuuming with a vacuum unit, opening and closing vacuum valves, adjusting the power supply to control the molten liquid temperature to 50 to 150°C above the alloy melting point, and adjusting the addition rate of the industrial pure graphite feedstock. These measures achieve soft boiling of the molten liquid without splashing and control the furnace pressure within 130 to 5000 Pa. After the alloy solution surface is basically calm, the pressure in the melting furnace is then steadily controlled to 40 to 130 Pa and maintained at 40 to 130 Pa for 5 to 30 minutes. 5) Step 5: Next, refine 3. By using the vacuum unit to evacuate the vacuum and the opening and closing of the vacuum valve, and adjusting the power supply, control the temperature of the melt to be 50-150°C above the melting point of the alloy. Control the vacuum degree in the furnace to be 5-38Pa and hold it for 5-15 minutes to ensure that the melt boils softly without splashing. 6) Step 6: Then, add industrial ferroboron and the remaining industrial pure graphite feed bag to the crucible at the same time. By using a vacuum unit to evacuate and open and close the vacuum valves, and adjusting the power supply, the temperature of the melt is controlled at 50-150°C above the melting point of the alloy. These two combined measures stabilize the furnace pressure from 130-5000Pa to 40-130Pa, achieving the clearing of industrial ferroboron and soft boiling of the melt without splashing. The pressure is maintained at 40-130Pa for 2-5 minutes, and then argon is purged at 0.11-0.12MPa for protection. 7) Step 7: After argon purging, prepare for combined supersonic atomization and rotary ultrafine atomization for ultrafine powder production: Before spraying, temporarily adjust the temperature of the alloy melt in the crucible to 100-250℃ above the melting point; the crucible melting chamber, the spray chamber equipped with the supersonic atomizing nozzle and the ultrafine centrifugal atomizing rotary disk, and the powder cooling chamber are arranged from top to bottom, and all three chambers are within a vacuum system; the ultrafine centrifugal atomizing rotary disk is composed of a low thermal conductivity non-metallic material on the disk surface in contact with the supersonic atomized droplets and a metallic material on the disk substrate. The axis of the ultrafine centrifugal atomizing rotary disk is parallel to but does not coincide with the center line of the supersonic atomization nozzle. The disk surface of the ultrafine centrifugal atomizing rotary disk is conical, with the lowest point near the disk axis and the highest point at the disk edge. The angle between the disk radius and the horizontal plane is 1-5°; the edge of the disk and the ultrafine centrifugal atomizing nozzle are conical. The vertical distance from the lower end face of the sonic atomizing nozzle is 10–49 mm; adjusting the turntable speed causes the spray droplets to rapidly break into fine droplets on the turntable surface, and the flight speed reaches 30–300 m / s when the centrifugal motion detaches from the edge of the turntable; after spraying, the infrared temperature monitoring point is quickly switched to aim at the center of the fine droplet area just away from the edge of the turntable, controlling the power of the intermediate frequency induction power supply to indirectly control the temperature of the liquid alloy in the crucible, and achieving the control of the center temperature of the fine droplet area just away from the edge of the turntable at 10–250℃ above the alloy melting point; the horizontal dimension of the droplet flight trajectory is 1500–15000 mm; in the initial stage of the centrifugal flight process, the droplets disperse into even finer droplets, and from this point until the finer droplets reach the inner wall of the atomizing chamber is the rapid solidification stage, and the... The fine droplets undergo rapid solidification; the argon supersonic spray pressure is 2.0–4.0 MPa higher than the argon pressure inside the spray chamber; the argon in the spray chamber and powder cooling chamber is cooled by high-speed circulation forced heat exchange; the argon at the spray chamber outlet and powder cooling chamber outlet is subjected to extraction, forced cooling, purification, pressurization, and circulation supply. One supply line is given to the nozzle gas inlet, another to the nozzle above the cooling gas curtain during the rapid solidification stage of the finer droplets in the atomization chamber, and a third to the nozzle at the powder-tumbling area in the powder cooling chamber. Throughout the spraying process, the argon temperature supplied to the nozzle gas inlet and nozzle inlet via the three circulation lines is controlled to be below 200°C; during the rapid solidification stage of the finer droplets in centrifugal flight, the argon gas is supplied at a horizontal distance of 500–200 mm from the edge of the turntable. Within the flight airspace starting at 000mm and ending at the double-layered water-cooled inner wall of the spray chamber in the flight direction, finer droplets are continuously blown by a multi-nozzle cooling curtain of argon gas that has undergone forced circulation cooling during the spraying process. The argon gas pressure is 0.10–0.25 MPa higher than the air pressure in the spray chamber. Below the endpoint of the finer droplets is the powder cooling chamber, where the powder settles after the flight. The powder in the powder cooling chamber is continuously stirred, tumbled, and blown by a multi-nozzle cooling curtain of argon gas that has undergone forced circulation cooling. The argon gas pressure is 0.10–0.25 MPa higher than the air pressure in the powder cooling chamber. During the stirring and tumbling process, the powder in contact with the inner wall of the cooling chamber is cooled by the double-layered water-cooled inner wall until the powder temperature reaches 5–20°C above room temperature. 8) Step 8: After the powder in the cooling chamber has cooled to room temperature, transfer the powder to the cyclone classifier. First, evacuate the vacuum to below 1 Pa, then perform nitrogen cyclone classification. The particle size D of the spray-dried powder is determined. 50 The powder, ranging from 3 to 15 μm, is first vacuum-sealed at 1 Pa and then encapsulated with nitrogen. 9) Step 9: Based on the operating frequency of the powder application device, the finer the powder after grading, the higher the frequency. For frequencies between 50Hz and 3MHz, select D. 50 The powder is 15-3μm in size; then the powder is inorganically and organically insulated and then pressure-formed into a magnetic powder core. 10) Step 10: First, vacuum crystallize and heat-treat the magnetic powder core, then measure the magnetic properties of the magnetic powder core.

2. As described in claim 1, step 1 of the method for preparing low magnetic loss nanocrystalline powder is characterized in that: the alloy composition at% of the sprayed powder is Fe. a Si b B c M d Cu e C f , 75.0≤a≤82.0, 3.0≤b≤13.0, 10.5≤c≤16.5, 1.0≤d≤2.0, 0.5≤e≤1.5, 0.010≤f≤0.020, a+b+c+d+e=100at%; where M is at least one of Nb, Ti, Zr, Hf, Mo, and W, the composition range of at least one of Mo and W is 0.50~1.50, and the composition range of at least one of Nb, Ti, Zr, and Hf is 0.15~0.50; the oxygen content of the sprayed powder alloy is less than 100ppm.

3. As described in claim 1, step 7 of the method for preparing low magnetic loss nanocrystalline powder is characterized in that: the low thermal conductivity non-metallic material on the surface of the ultrafine centrifugal atomizing disc is zirconium oxide.

4. As described in claim 1, a method for preparing low magnetic loss nanocrystalline powder is characterized in that: other alloys are first vacuum melted and refined, and then subjected to a combination of supersonic atomization and rotary ultrafine atomization as described in step 7, and cyclone classification as described in step 8, which can produce other alloy powders that are finer than those prepared by existing supersonic atomization methods. 50 It reaches 3-15μm.