A magnetic ring with an arc surface and its manufacturing process

Abstract

The present invention discloses a magnetic ring with a curved surface and a manufacturing process thereof, which belongs to the field of soft magnetic material production technology, and comprises the following steps: first preparing a preset amount of FeSiCr alloy powder; then, using ball milling to flatten it; then, performing surface phosphating on it; after it is fully dried, passivating it, and then, insulating and coating the material after secondary acidification; and then, after respectively pressing and forming, curing treatment and auxiliary processing, a magnetic ring product with a curved surface can be obtained. The stoichiometric ratio of the core molecular formula of this magnetic ring product is a mass percentage, wherein Fe is 87.80-91.75, Si is 3.65-8.20, and Cr is 4-5.55, and the sum of the percentages of the above three components is 100. The present invention solves the technical problem of large high-frequency loss of magnetic ring products in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of soft magnetic material production technology, in particular to a magnetic ring with an arc surface and a manufacturing process thereof. Background Art

[0002] Soft magnetic materials, with their high saturation magnetic induction intensity and magnetic permeability, play an irreplaceable role in electromagnetic conversion, energy storage and transmission. Traditional metal soft magnetic powder cores are made by uniformly mixing insulating metal or alloy powders with binders to form composite soft magnetic particles, which are prepared by powder metallurgy. Metal soft magnetic powder cores have high resistivity, low loss, and a wide range of application frequencies. With the development of science and technology and the progress of society, people have put forward new requirements for the development of the electronics industry: (1) The development of electronic devices should be miniaturized, high-frequency, integrated, and lightweight; (2) The development of the electronics industry should follow the principle of sustainable development. According to the above principles, in the process of preparing electronic devices, it is necessary to carefully select raw materials, optimize the preparation process as much as possible, reduce the impact on the environment during the preparation process, and improve the quality of electronic devices. Among the several categories of metal magnetic powder cores, the metal magnetic powder core systems that are currently more mature in industrial application include: pure iron powder core, Fe-Si system, Fe-Si-Al system, and Fe-Ni system.

[0003] Based on this, Chinese patent CN106205930A discloses a method for preparing an iron-nickel-molybdenum metal magnetic powder core, which includes the following steps: (1) smelting and atomization; (2) particle size combination; (3) magnetic powder ball milling; (4) heat treatment; (5) chemical coating; (6) oxidation film formation; (7) secondary insulation coating; (8) pressing and forming; (9) magnetic core annealing; (10) painting. The above-disclosed method for preparing an iron-nickel-molybdenum metal magnetic powder core has the advantages of low cost and easy operation. However, due to the high material price of iron-nickel-molybdenum magnetic powder, its cost is about 6 times that of traditional FeSiAl magnetic powder, resulting in extremely small actual market demand for the above-mentioned preparation method.

[0004] In addition, Chinese patent CN104361968A also discloses a method for preparing a low-loss, high-permeability Sendust magnetic powder core; the method comprises adding a small amount of Ti to FeSiAl during smelting, casting an ingot, crushing it into powder, and then subjecting it to high-temperature hydrogen annealing, insulation coating, molding, and core annealing to prepare a Sendust magnetic powder core with a magnetic permeability of 147. The loss at 50kHz and 100mT is 280mW / cm 3Although the magnetic core prepared by the above-disclosed method for preparing a low-loss, high-permeability sendust magnetic powder core has a high magnetic permeability, the eddy current loss is large and the loss is relatively high because the magnetic core powder prepared is relatively coarse. Moreover, because the crushed powder used in this preparation method has defects such as low magnetic core density and poor stacking performance.

[0005] Therefore, the soft magnetic materials currently popular in the market for integrated inductor components include FeSiCr alloy powder cores and carbonyl iron powder cores in the Fe-Si family. The addition of Cr to the FeSiCr alloy significantly enhances the corrosion resistance of Fe-Si alloys; however, this also makes it difficult to passivate the FeSiCr alloy powder with the weak acid H₃PO₄ during production and processing, allowing a complete inorganic insulating layer to form on its surface. Furthermore, the FeSiCr alloy powder has a relatively hard texture, making the surface insulating layer susceptible to cracking during conventional pressing. Furthermore, the internal structure of conventional FeSiCr alloy powder cores is a three-dimensional network composed of air gaps, internal stresses, and insulated alloy powder. Due to factors such as the particle shape and particle size distribution of the FeSiCr alloy powder cores, cavities are likely to remain within the pressed cores, making them susceptible to breakdown when used in high-voltage alternating magnetic fields. Therefore, existing FeSiCr alloy powder cores generally have the technical problem of high high-frequency loss. Summary of the Invention

[0006] Based on this, it is necessary to provide a magnetic ring with a curved surface and a manufacturing process thereof to address the technical problem of high high-frequency loss in the iron-based magnetic ring in the prior art.

[0007] A manufacturing process of a magnetic ring with a curved surface comprises the following steps:

[0008] S1: First, a preset mass of aerosolized FeSiCr alloy powder is weighed and placed into a ball mill; then, a preset mass of anhydrous ethanol is weighed according to the mass of the weighed FeSiCr alloy powder and poured into the ball mill; after the ball mill is sealed, the ball mill is placed in a ball milling device; the ball-to-material ratio is set to 10:1, the rotation speed is set to 300 r / min, and the ball milling time is set to 15 h;

[0009] S2: Then, the ball-milled FeSiCr alloy powder is added to a 1.5 wt.% H3PO4 acetone solution, wherein the mass ratio of the acetone solution to the FeSiCr alloy powder is 1.5:1; then, the mixture is uniformly stirred at 50°C until the acetone solution is completely volatilized; then, the remaining FeSiCr alloy powder is continuously dried in a vacuum drying oven at 120°C for 1 hour;

[0010] S3: Then, phosphated FeSiCr alloy powder with a particle size of less than 140 mesh was selected and added to a 2.0 wt% HCl ethanol solution. The mixed slurry was placed in a 65°C water bath and stirred evenly for 4 hours. After stirring, the FeSiCr powder was dried in a vacuum drying oven at 120°C for 1 hour.

[0011] S4: Next, FeSiCr alloy powder with a particle size of less than 140 mesh is selected using a vibrating screening machine, and the powder is placed in a pre-mixed solution of acetone and 1 wt.% KH-550, and the mixture is further stirred and dried. Then, a mixed solution of acetone and sodium silicate aqueous solution is dripped into the mixture, and finally, the mixture is stirred again and dried in a vacuum drying oven at 100° C. for 1 hour.

[0012] S5: Next, the forming mold is first wiped with an anhydrous alcohol solvent until the surface is smooth, and then barium stearate is used as a lubricant for the forming mold. Then, the FeSiCr powder after the insulation coating is placed in the forming mold for forming, wherein the forming pressure is 900 MPa and the pressure holding time is 90 seconds.

[0013] S6: Next, the iron-based magnetic powder core obtained after compression molding is placed in a drying oven and cured at 200° C. in an air atmosphere for 2 hours;

[0014] S7: Finally, the solidified iron-based magnetic powder core is polished into a magnetic ring with a curved surface.

[0015] Specifically, in step S1 , the mass ratio of the FeSiCr alloy powder to the anhydrous ethanol added into the ball mill at a single time is 1:2.

[0016] Specifically, in step S2, H3PO4 is first completely dispersed in the acetone solution under the action of an ultrasonic stirrer.

[0017] Specifically, in step S2, the temperature of the water bath reaction pot is set to 50° C., the acetone phosphate solution is first added, and then the FeSiCr alloy powder is added to the acetone phosphate solution.

[0018] Specifically, in step S2, a mechanical stirrer is first used to uniformly stir the mixed solution of the FeSiCr alloy powder and acetone phosphate until the acetone is completely volatilized, and the entire stirring process lasts for 40 minutes.

[0019] Specifically, the FeSiCr alloy powder was placed in a fume hood and dried at room temperature for 30 minutes, and then sieved using a 140-mesh sieve.

[0020] Specifically, finally, the FeSiCr alloy powder particles with a particle size less than 140 mesh were dried in a vacuum drying oven at 120° C. for 1 hour.

[0021] Specifically, the mass of the added sodium silicate aqueous solution accounts for 3%-4% of the mass of the input FeSiCr alloy powder.

[0022] Furthermore, a magnetic ring prepared by the above-mentioned manufacturing process of a magnetic ring with a curved surface has a stoichiometric ratio of the core molecular formula as a mass percentage, wherein Fe is 87.80-91.75, Si is 3.65-8.20, and Cr is 4.00-5.55, and the sum of the percentages of the above three components is 100.

[0023] In summary, the manufacturing process for a magnetic ring with a curved surface according to the present invention first flattens FeSiCr powder through ball milling. Because the soft magnetic properties of FeSiCr powder are closely related to its density and resistivity, the quality factor of the magnetic powder core first increases and then decreases with increasing milling time. When the milling time is set to approximately 15 hours, a powder with a diameter of approximately 30 μm, a thickness of approximately 0.2 μm, and a particle aspect ratio (diameter / thickness) of 150 is obtained, resulting in the best overall magnetic properties for the magnetic powder core. Next, the FeSiCr alloy powder is subjected to a surface phosphating process for insulation coating. The reaction between the FeSiCr alloy powder and H₃PO₄ forms an inorganic phosphate layer on the surface of the FeSiCr alloy powder. The thickness of the insulation layer can be adjusted by controlling the phosphating temperature and the concentration of the phosphating solution. The real part of the complex permeability and high-frequency loss factor of the FeSiCr alloy magnetic powder core decrease with increasing phosphating concentration. However, the FeSiCr alloy powder reacts slowly with H₃PO₄ at room temperature, resulting in a thinner insulation layer. Therefore, continuing to use the secondary acidification process can promote further passivation of the surface of the FeSiCr alloy powder, and forming an insulating layer of phosphate and chloride containing Fe ions and Cr ions on its surface. In addition, the type of binder has a great influence on the magnetic properties of the FeSiCr magnetic powder core, and selecting a suitable binder is conducive to obtaining a magnetic powder core with the best coating effect. The manufacturing process of a magnetic ring with an arc surface of the present invention uses a sodium silicate aqueous solution as a binder in the insulation coating process to obtain a magnetic powder core with the highest magnetic permeability, the lowest loss, the largest quality factor at high frequency, and the best comprehensive magnetic properties. Then, in the subsequent pressing molding process and the curing treatment process, the influencing factors of the previous steps are synchronously and comprehensively matched. Then, a new type of magnetic ring product can be prepared through the above steps. Therefore, the manufacturing process of a magnetic ring with an arc surface of the present invention solves the technical problem of high high-frequency loss existing in the iron-based magnetic ring of the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a process flow chart of a manufacturing process of a magnetic ring with a curved surface according to the present invention;

[0025] Figure 2 A structural diagram of a BH AC magnetic characteristics analysis system. DETAILED DESCRIPTION

[0026] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0027] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0028] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0029] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0030] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0031] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0032] See also Figure 1 , Figure 1 The following is a process flow chart of the manufacturing process of a magnetic ring with an arc surface according to the present invention. Figure 1 As shown, the present invention provides a manufacturing process for a magnetic ring with an arc surface, which includes the following steps:

[0033] S1: First, a preset mass of aerosolized FeSiCr alloy powder is weighed and placed into a ball mill; then, a preset mass of anhydrous ethanol is weighed according to the mass of the weighed FeSiCr alloy powder and poured into the ball mill; after the ball mill is sealed, the ball mill is placed in a ball milling device; the ball-to-material ratio is set to 10:1, the rotation speed is set to 300 r / min, and the ball milling time is set to 15 h;

[0034] S2: Then, the ball-milled FeSiCr alloy powder is added to a 1.5 wt.% H3PO4 acetone solution, wherein the mass ratio of the acetone solution to the FeSiCr alloy powder is 1.5:1; then, the mixture is uniformly stirred at 50°C until the acetone solution is completely volatilized; then, the remaining FeSiCr alloy powder is continuously dried in a vacuum drying oven at 120°C for 1 hour;

[0035] S3: Then, phosphated FeSiCr alloy powder with a particle size of less than 140 mesh was selected and added to a 2.0 wt% HCl ethanol solution. The mixed slurry was placed in a 65°C water bath and stirred evenly for 4 hours. After stirring, the FeSiCr powder was dried in a vacuum drying oven at 120°C for 1 hour.

[0036] S4: Next, FeSiCr alloy powder with a particle size of less than 140 mesh is selected using a vibrating screening machine, and the powder is placed in a pre-mixed solution of acetone and 1 wt.% KH-550, and the mixture is further stirred and dried. Then, a mixed solution of acetone and sodium silicate aqueous solution is dripped into the mixture, and finally, the mixture is stirred again and dried in a vacuum drying oven at 100° C. for 1 hour.

[0037] S5: Next, the forming mold is first wiped with an anhydrous alcohol solvent until the surface is smooth, and then barium stearate is used as a lubricant for the forming mold. Then, the FeSiCr powder after the insulation coating is placed in the forming mold for forming, wherein the forming pressure is 900 MPa and the pressure holding time is 90 seconds.

[0038] S6: Next, the iron-based magnetic powder core obtained after compression molding is placed in a drying oven and cured at 200° C. in an air atmosphere for 2 hours;

[0039] S7: Finally, the solidified iron-based magnetic powder core is polished into a magnetic ring with a curved surface.

[0040] Specifically, in step S1, the mass ratio of FeSiCr alloy powder to anhydrous ethanol added to the ball mill is 1:2. For example, for a single charge of 1 kg of FeSiCr alloy powder, 2 kg of anhydrous ethanol is required. Furthermore, the ball-to-material ratio is the mass ratio of the grinding balls to the material added. A ball-to-material ratio of 10:1 means that if 1 kg of FeSiCr alloy powder is added, the mass of the grinding balls is 10 kg. More specifically, studies of raw FeSiCr alloy powders prepared by water atomization have revealed that raw FeSiCr alloy powders exhibit irregular shapes and exhibit excellent press formability. Furthermore, the FeSiCr alloy powders gradually flatten with increasing ball milling time, resulting in a corresponding increase in the density and resistivity of the magnetic powder cores pressed therefrom. However, if the ball milling time is too long, the structure of the FeSiCr alloy powders can be easily destroyed, negatively impacting the density and resistivity of the magnetic powder cores. The soft magnetic properties of FeSiCr magnetic powder cores are closely related to their density and resistivity. As the ball-milling time of the FeSiCr alloy powder increases, the quality factor of the FeSiCr magnetic powder cores first increases and then decreases. Comparative experiments show that when the FeSiCr alloy powder is ball-milled for approximately 15 hours, a powder with a diameter of approximately 30 μm, a thickness of approximately 0.2 μm, and a particle aspect ratio (diameter / thickness) of 150 can be obtained. This results in FeSiCr magnetic powder cores with optimal overall magnetic properties.

[0041] Specifically, step S2 primarily involves subjecting the ball-milled FeSiCr alloy powder to a first acidification treatment, also known as a phosphating treatment. In this step, the ball-milled FeSiCr alloy powder is first coated with an insulating layer using a surface phosphating process, also known as a primary acidification process. After the ball-milling process, the FeSiCr alloy powder readily reacts with H₃PO₄, forming an inorganic phosphate layer on the FeSiCr powder surface. The thickness of the insulating layer can be adjusted by controlling the phosphating temperature and the concentration of the phosphating solution. Repeated experiments have shown that the real part of the complex magnetic permeability and high-frequency loss factor of FeSiCr alloy magnetic powder cores decrease with increasing phosphating concentration. Because the FeSiCr alloy powder reacts slowly with H₃PO₄ at room temperature, the resulting insulating layer is relatively thin. Increasing the phosphating temperature accelerates the phosphating reaction rate, thereby increasing the thickness of the insulating layer on the FeSiCr alloy powder surface. The saturation magnetization, Ms, of the FeSiCr alloy powder phosphated with 1.5 wt.% H₃PO₄ significantly decreases. More specifically, first, an H₃PO₄ acetone solution of appropriate concentration is prepared based on the mass of the ball-milled alloy powder. Specifically, the H₃PO₄ is completely dispersed in the acetone solution using an ultrasonic stirrer. A preferred concentration of the H₃PO₄ acetone solution is 1.5 wt.%, and the mass ratio of the acetone solution to the FeSiCr alloy powder is 1.5:1. Next, the FeSiCr alloy powder is added to the phosphate-acetone solution, and the temperature of the water bath reaction vessel is set to room temperature, i.e., 25°C, 50°C, or 65°C. In a preferred embodiment, the water bath temperature is set to 50°C. The FeSiCr alloy powder and phosphate-acetone mixed solution is then stirred at a constant speed using a mechanical stirrer until the acetone is completely evaporated. The stirring process lasts for 40 minutes. The acidified FeSiCr alloy powder is then dried in a fume hood at room temperature for 30 minutes. The slightly damp alloy powder is then granulated using a 140-mesh sieve. Finally, the FeSiCr alloy powder particles with a particle size less than 140 mesh and having undergone the primary acidification were dried in a vacuum drying oven at 120° C. for 1 hour. Thus, the process of insulating and coating the FeSiCr alloy powder using the H 3 PO 4 acetone solution was completed.

[0042] Furthermore, in the above step S3, the FeSiCr alloy powder that has been phosphated is further subjected to a secondary acidification treatment. The secondary acidification treatment is based on the primary acidification, i.e., phosphating, and the passivated metal magnetic powder is subjected to an inorganic passivation treatment again using a strong acid. Since the passivation and corrosion processes occur simultaneously when the FeSiCr alloy powder reacts with H3PO4 and HCl. The FeSiCr alloy powder has good corrosion resistance, and therefore, its reaction rate with the weak acid H3PO4 is low, making it difficult to generate an insulating layer with a certain thickness on the surface of the alloy powder. The passivated FeSiCr alloy powder further reacts chemically with HCl, and an insulating layer with a certain thickness is generated again on the surface of the phosphating layer. At this time, the FeSiCr alloy powder changes from the original single sphere to a core-shell structure with a double insulating layer. In particular, since the acidifying agent used is a concentrated HCl ethanol solution and the boiling point of ethanol is 78.3°C, in order to control the reaction rate between the FeSiCr alloy powder and HCl and avoid excessive volatilization of the ethanol solution, the entire secondary acidification reaction needs to be carried out at a temperature of about 65°C.

[0043] Specifically, in the above-mentioned step S4, the insulation coating treatment of the FeSiCr alloy powder seat after the secondary acidification is continued. Since the type of binder has a great influence on the magnetic properties of the FeSiCr magnetic powder core, it is beneficial to select a suitable binder to obtain a magnetic powder core with the best coating effect. The magnetic powder core obtained by using the sodium silicate aqueous solution as a binder has the highest magnetic permeability and the lowest loss, the largest quality factor at high frequency, and the best comprehensive magnetic properties. In addition, the different contents of the binder have different effects on the magnetic properties of the FeSiCr magnetic powder core. When the added content is small, the more binder, the smaller the loss of the FeSiCr magnetic powder core and the larger the quality factor as a whole, but too much added content will greatly affect the magnetic permeability of the magnetic powder core. On the whole, when sodium silicate aqueous solution is used as a binder and the added content is between 3% and 4% of the mass of the FeSiCr alloy powder input, the obtained magnetic powder core has the best comprehensive magnetic properties. More specifically, insulation coating is the most core process in the entire process of preparing magnetic powder cores. The properties of the insulation coating agent will directly affect the electromagnetic properties of the pressed magnetic powder core. There are two main purposes for insulation coating of metal magnetic powder: first, the insulation coating agent, usually an inorganic coating agent or an organic coating agent, can act as a binder, improve the formability of the magnetic powder core, increase the strength of the magnetic powder core, and facilitate the industrial production and transportation of the product; second, the insulation coating agent, as a non-magnetic material, tightly coats the surface of the metal magnetic powder, which can effectively increase the resistivity between the metal powders, reduce the eddy current loss of the magnetic powder core, increase the operating frequency range of the magnetic powder core, and improve its electromagnetic properties in the alternating magnetic field.

[0044] Furthermore, the above step S5 is a process of pressing and forming the composite magnetic powder core. The pressing and forming process of the composite magnetic powder core is to mix the metal magnetic powder coated with insulation and lubricant uniformly.

[0045] Then it is pressed into magnetic rings of various specifications. The molding pressure, holding time and molding method will have a great impact on the final performance of the magnetic powder core. According to existing technology, the magnetic permeability of the magnetic powder core is positively correlated with the density. Therefore, the greater the molding pressure, the smaller the air gap inside the prepared powder core, the greater the green density, and the greater the effective magnetic permeability μe. However, the molding pressure has a limited effect on the density of the magnetic powder core. Excessive pressure will cause the insulating layer on the surface of the magnetic powder to rupture or even cause the magnetic ring to crack, exposing the conductive magnetic particles. The conductive particles contact each other, reducing the resistance of the magnetic powder core and increasing the power loss of the composite magnetic powder core. In the present invention, a magnetic ring with an arc surface and its manufacturing process, a four-column hydraulic press dry cold pressing method can be used to prepare a ring with an inner diameter of 10-60mm and an outer diameter of 20-100mm. Specifically, the mold can be wiped with an anhydrous alcohol solvent until the surface is smooth, and then barium stearate can be used as a mold lubricant to avoid scratches on the surface of the magnetic ring and difficulty in demolding during the pressing process, resulting in cracking. The pressure used in the preparation of the FeSiCr alloy powder through the above steps is in the range of 558 MPa to 1302 MPa. Considering that the particles are likely to overflow from the mold due to excessive pressure, the preferred pressure used during pressing is 900 MPa.

[0046] Furthermore, the above-mentioned step S6 is mainly a heat treatment process for the iron-based magnetic powder core. As the finishing step in the preparation of the magnetic powder core, the heat treatment process plays a decisive role in the final electromagnetic properties of the magnetic powder core. Since the magnetic powder core is subjected to great pressure during the pressing process, a large amount of internal stress will inevitably be generated inside the powder core. On the one hand, the existence of these internal stresses will lead to stress concentration inside the magnetic powder core, reducing the mechanical strength of the magnetic powder core; on the other hand, it will hinder the movement of magnetic domains, increase the coercive force of the magnetic powder core, and rapidly increase the hysteresis loss. The use of a heat treatment process can release the internal stress of the powder core, thereby improving the comprehensive performance of the magnetic powder core. Common heat treatment methods include: warm pressing, hot pressing, hot isostatic pressing, hot-magnetic field heat treatment and two-step pressing. The main process parameters of heat treatment include: protective atmosphere, heat treatment temperature, holding time and cooling rate. The protective atmosphere is mainly divided into: air, inert gas, and reducing gas. Compared to inert and reducing gas atmospheres, magnetic powder cores are more susceptible to oxidation during heat treatment in an air atmosphere, resulting in an increase in the non-magnetic phase within the powder core and a significant decrease in magnetic permeability. The annealing temperature has a particularly significant impact on the performance of the powder core. In powder cores formed by high-pressure pressing, the particles at the internal grain boundaries squeeze and deform, increasing the total free energy within the crystal. This lattice distortion generates a stress field, leading to magnetic domain pinning, hindering domain wall motion, and increasing the core's coercivity. High-temperature heat treatment causes recovery recrystallization in the high-energy distortion regions, gradually reducing grain boundaries and dislocations, releasing internal stress, promoting domain rearrangement, increasing the powder core's magnetic permeability, reducing coercivity and power loss, and improving its overall performance. Considering that powder cores contain an insulating agent, while inorganic insulating agents have high heat resistance, organic insulating agents are susceptible to decomposition at high temperatures. Excessive heat treatment temperatures can cause the insulating coating on the powder core surface to decompose, exposing the conductive powder surface, reducing resistivity and dramatically increasing eddy current losses. There are a large number of defects and internal stresses inside the molded metal magnetic powder core, which will cause a sudden increase in coercive force and a sudden increase in hysteresis loss factor. It is necessary to release the internal stress of the magnetic powder core through annealing. In the aforementioned steps, the thermal decomposition temperature of the binder introduced during the preparation of the magnetic powder core is relatively low, so it is advisable to use a low-temperature curing heat treatment method to cure the magnetic powder core. In order to prevent the binder from aging prematurely and losing its insulation properties, the best treatment solution is to set the heat treatment temperature to 200°C. At the same time, in order to adapt to large-scale production in factories and reduce the cost of curing and low-temperature annealing of magnetic powder cores, the heat treatment atmosphere is set to air. Therefore, the pressed iron-based magnetic powder core can be placed in a drying oven and cured at 200°C in an air atmosphere for 2 hours.

[0047] Furthermore, in the above step S7, the iron-based magnetic powder core after the curing treatment can be polished into a magnetic ring with a curved surface; the magnetic ring with a curved surface can be annular, circular or E-shaped.

[0048] Furthermore, after the above manufacturing process, a magnetic ring with a curved surface can be obtained, wherein the stoichiometric ratio of the core molecular formula is as follows: Fe is 87.80-91.75, Si is 3.65-8.20, and Cr is 4-5.55, and the sum of the percentages of the above three components is 100. One preferred embodiment is: Fe is 88.32, Si is 6.68, and Cr is 5.00.

[0049] Furthermore, a number of magnetic ring products with an inner diameter of 10 mm and an outer diameter of 20 mm were prepared using the manufacturing process of a magnetic ring with a curved surface according to the present invention, wherein product A is a product made according to the manufacturing process according to the present invention, and product B is a common commercially available magnetic ring product with the same size. Then, a HitchiBH-2000 BH AC magnetic property analyzer manufactured by Hitachi, Japan, was used to measure the soft magnetic properties of the magnetic powder core. Figure 2 As shown, the analysis system consists of two parts: a computer system and a test system. Among them, the data such as the outer diameter, inner diameter and height of the magnetic powder core can be used in the computer calculation software to obtain the effective cross-sectional area Ae, effective magnetic path length Le and effective volume Ve of the sample, and these parameters as well as the powder core mass and the number of coil turns are input into the test system to obtain the loss data of the magnetic powder core at different frequencies. In the specific measurement test, 0.5mm enameled copper wire was uniformly selected, the primary coil was wound with 10 turns, the secondary coil was wound with 15 turns, and the test frequency range was 50kHz-1000kHz. The loss data of the measured product are shown in Table 1 below. According to the data in Table 1, the loss of the magnetic ring product prepared using the manufacturing process of the magnetic ring with an arc surface of the present invention is significantly lower than the common magnetic ring products currently on the market. In particular, at a frequency of 1000kHz, the loss of the magnetic ring product prepared by the present invention is 10.62W / kg, which is about 19.2% lower than that of existing products.

[0050] Table 1 FeSiCr powder core loss test

[0051]

[0052] In summary, the manufacturing process for a magnetic ring with a curved surface according to the present invention first flattens FeSiCr powder through ball milling. Because the soft magnetic properties of FeSiCr powder are closely related to its density and resistivity, the quality factor of the magnetic powder core first increases and then decreases with increasing milling time. When the milling time is set to approximately 15 hours, a powder with a diameter of approximately 30 μm, a thickness of approximately 0.2 μm, and a particle aspect ratio (diameter / thickness) of 150 is obtained, resulting in the best overall magnetic properties for the magnetic powder core. Next, the FeSiCr alloy powder is subjected to a surface phosphating process for insulation coating. The reaction between the FeSiCr alloy powder and H₃PO₄ forms an inorganic phosphate layer on the surface of the FeSiCr alloy powder. The thickness of the insulation layer can be adjusted by controlling the phosphating temperature and the concentration of the phosphating solution. The real part of the complex permeability and high-frequency loss factor of the FeSiCr alloy magnetic powder core decrease with increasing phosphating concentration. However, the FeSiCr alloy powder reacts slowly with H₃PO₄ at room temperature, resulting in a thinner insulation layer. Therefore, continuing to use the secondary acidification process can promote further passivation of the surface of the FeSiCr alloy powder, and forming an insulating layer of phosphate and chloride containing Fe ions and Cr ions on its surface. In addition, the type of binder has a great influence on the magnetic properties of the FeSiCr magnetic powder core, and selecting a suitable binder is conducive to obtaining a magnetic powder core with the best coating effect. The manufacturing process of a magnetic ring with an arc surface of the present invention uses a sodium silicate aqueous solution as a binder in the insulation coating process to obtain a magnetic powder core with the highest magnetic permeability, the lowest loss, the largest quality factor at high frequency, and the best comprehensive magnetic properties. Then, in the subsequent pressing molding process and the curing treatment process, the influencing factors of the previous steps are synchronously and comprehensively matched. Then, a new type of magnetic ring product can be prepared through the above steps. Therefore, the manufacturing process of a magnetic ring with an arc surface of the present invention solves the technical problem of high high-frequency loss existing in the iron-based magnetic ring of the prior art.

[0053] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0054] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A manufacturing process for a magnetic ring with an arc surface, characterized in that: It includes the following steps: S1: First, a preset mass of aerosolized FeSiCr alloy powder is weighed and placed into a ball mill; then, a preset mass of anhydrous ethanol is weighed according to the mass of the weighed FeSiCr alloy powder and poured into the ball mill; after the ball mill is sealed, the ball mill is placed in a ball milling device; the ball-to-material ratio is set to 10:1, the rotation speed is set to 300 r / min, and the ball milling time is set to 15 h; S2: Next, the ball-milled FeSiCr alloy powder is added to a 1.5 wt% phosphoric acid-acetone solution, wherein the mass ratio of acetone to the FeSiCr alloy powder is 1.5:1; then, the mixture is uniformly stirred at 50° C. until the acetone is completely volatilized; then, the remaining FeSiCr alloy powder is continuously dried in a vacuum drying oven at 120° C. for 1 hour; S3: Then, phosphated FeSiCr alloy powder with a particle size of less than 140 mesh was selected and added to a 2.0 wt% HCl ethanol solution. The mixed slurry was placed in a 65°C water bath and stirred evenly for 4 hours. After stirring, the FeSiCr powder was dried in a vacuum drying oven at 120°C for 1 hour. S4: Then, a vibrating screening machine is used to select FeSiCr alloy powder with a particle size of less than 140 mesh, and the powder is placed in a pre-mixed solution of acetone and 1wt% KH-550, and the mixture is further stirred and dried; then, a mixed solution of acetone and sodium silicate aqueous solution is dripped into the dried modified FeSiCr alloy powder, and finally, the modified FeSiCr alloy powder dripped with the mixed solution of acetone and sodium silicate aqueous solution is stirred again and dried in a vacuum drying oven at 100°C for 1 hour; S5: Next, the forming mold is first wiped with an anhydrous alcohol solvent until the surface is smooth, and then barium stearate is used as a lubricant for the forming mold. Then, the FeSiCr powder after the insulation coating is placed in the forming mold for forming, wherein the forming pressure is 900 MPa and the pressure holding time is 90 seconds. S6: Next, the iron-based magnetic powder core obtained after compression molding is placed in a drying oven and cured at 200° C. in an air atmosphere for 2 hours; S7: Finally, the solidified iron-based magnetic powder core is polished into a magnetic ring with a curved surface.

2. The manufacturing process of a magnetic ring with a curved surface according to claim 1, characterized in that: In step S1 , the mass ratio of the FeSiCr alloy powder to the anhydrous ethanol added into the ball mill at a single time is 1:

2.

3. The manufacturing process of a magnetic ring with a curved surface according to claim 1, characterized in that: In step S2, H3PO4 is first completely dispersed in the acetone solution under the action of an ultrasonic stirrer.

4. The manufacturing process of a magnetic ring with a curved surface according to claim 2, characterized in that: In step S2, the temperature of the water bath reaction pot is set to 50° C., acetone phosphate solution is first added, and then the FeSiCr alloy powder is added to the acetone phosphate solution.

5. The manufacturing process of a magnetic ring with a curved surface according to claim 3, characterized in that: In step S2, a mechanical stirrer is first used to uniformly stir the mixed solution of the FeSiCr alloy powder and acetone phosphate until the acetone is completely volatilized. The entire stirring process lasts for 40 minutes.

6. The manufacturing process of a magnetic ring with a curved surface according to claim 4, characterized in that: Then, the FeSiCr alloy powder was placed in a fume hood and dried at room temperature for 30 min, and then sieved using a 140-mesh sieve.

7. The manufacturing process of a magnetic ring with a curved surface according to claim 5, characterized in that: Finally, the FeSiCr alloy powder particles with a particle size less than 140 mesh were dried in a vacuum drying oven at 120° C. for 1 hour.

8. The manufacturing process of a magnetic ring with a curved surface according to claim 1, characterized in that: The mass of the added sodium silicate aqueous solution accounts for 3%-4% of the mass of the input FeSiCr alloy powder.

9. A magnetic ring manufactured by the manufacturing process of a magnetic ring with a curved surface according to any one of claims 1 to 8, characterized in that: The stoichiometric ratio of the core molecular formula of the magnetic ring obtained by the manufacturing process of a magnetic ring with a curved surface as described in any one of claims 1 to 8 is a mass percentage, wherein Fe is 87.80-91.75, Si is 3.65-8.20, and Cr is 4.00-5.55, and the sum of the percentages of the three components Fe, Si, and Cr is 100.

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