Gradient functionalized high-performance iron-nickel magnetic powder core and preparation method

Abstract

The invention relates to the technical field of magnetic materials, and provides a gradient functionalized high-performance iron-nickel magnetic powder core and a preparation method. The preparation method comprises the following steps: carrying out grain size distribution on iron-nickel powder, carrying out primary coating by using quartz powder, carrying out secondary synergistic coating by using phosphoric acid and silica sol, carrying out bonding lubrication, carrying out compression molding, and sintering to obtain the gradient functionalized high-performance iron-nickel magnetic powder core. According to the method, on the basis of gradient functionalization design of a coating layer, an electron migration path is blocked through a high-density quartz layer, then phosphoric acid-silica sol synergistically coats to form a composite insulating layer, and finally, a thin quartz-phosphate-nano silicon dioxide gradient functionalization coating layer with uniform thickness is formed on the surface of iron-nickel powder. The obtained iron-nickel magnetic powder core is low in loss and good in direct current bias performance, and the method is simple, environmentally friendly and low in cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of soft magnetic functional materials, and particularly relates to a gradient functionalized high-performance iron-nickel magnetic powder core and a preparation method thereof. BACKGROUND

[0002] With the rapid development of modern power electronics, information communication and technology, the importance of soft magnetic materials is increasingly highlighted in these fields, and the demand is increasing. As a core passive device, soft magnetic materials bear the role of electromagnetic energy conversion and transmission, and are the key magnetic conductive materials for power generation, transmission and conversion. Under the background of artificial intelligence, power electronic equipment tends to be high-frequency, high-efficiency and energy-saving, requiring electronic components to be efficient and small. With the development of power electronic equipment, communication equipment, electric vehicles and smart grids, the demand for DC bias characteristics and loss performance of iron-nickel materials is becoming higher and higher. Iron-nickel soft magnetic materials have high permeability and excellent DC bias characteristics, but their process is complex, the cost is high, the old process pollutes the environment, and the material has high eddy current loss, which limits its wide application and development in various fields. Therefore, it is a research hotspot to reduce the eddy current loss, the preparation method and the cost of the iron-nickel soft magnetic material while maintaining its original high DC bias characteristics.

[0003] The current preparation method of iron-nickel magnetic powder core is to combine iron-nickel magnetic powder core and insulating material, and coat a layer of insulating material coating on the surface of the magnetic powder through multiple complex processes. However, the current multi-process coating is not complete and uniform, and the process is complex and costly, which cannot meet the current demand for high performance and low cost. Therefore, a multi-layer uniform coating and gradient functionalized powder coating process is needed, which is simple and low in cost. Through a suitable annealing process, the magnetic properties of iron-nickel soft magnetic powder core are improved to develop its application in various fields. SUMMARY

[0004] The application provides a gradient functionalized high-performance iron-nickel magnetic powder core and a preparation method thereof, aiming to solve the problem that iron-nickel magnetic powder core is difficult to have low loss and excellent DC bias characteristics, and to solve the problem of complex preparation process.

[0005] A gradient functionalized high-performance iron-nickel magnetic powder core preparation method, using quartz powder, phosphoric acid and silica sol as insulating reagents to perform gradient insulating coating on the surface of iron-nickel magnetic powder particles. Through multi-layer insulating coating, the problem of direct contact between particles leading to conduction or electromagnetic interference is effectively solved. The preparation method is simple, environmentally friendly and low in cost. The obtained coating layer has good stability and high temperature resistance, and its thickness can be flexibly adjusted by increasing or decreasing the amount of reagents. A gradient functionalized high-performance iron-nickel magnetic powder core is obtained by the gradient functionalized high-performance iron-nickel magnetic powder core preparation method. While maintaining the original excellent DC bias characteristics, the eddy current loss is significantly reduced.

[0006] A method for preparing a gradient functionalized high-performance iron-nickel magnetic powder core, comprising the following steps:

[0007] (1) Particle size grading: using a tapping vibrating screen to screen the iron-nickel powder by particle size, obtaining the iron-nickel powder with the required particle size, and then mixing by a certain proportion to obtain the iron-nickel powder with the graded particle size;

[0008] (2) First passivation coating: adding quartz powder to the iron-nickel powder with the graded particle size obtained in step (1) and mixing in a ball mill to coat a first passivation layer on the surface of the iron-nickel powder;

[0009] (3) Second passivation coating: adding a mixed ethanol solution of phosphoric acid and silica sol to the iron-nickel powder coated with the first passivation layer obtained in step (2), stirring uniformly, and then reacting in a rotary instrument, cooling and sieving after the reaction is completed, to coat a second passivation layer on the surface of the iron-nickel powder;

[0010] (4) Bonding and lubrication: adding an ethanol solution of silicone resin to the iron-nickel powder coated with the second passivation layer obtained in step (3), stirring uniformly, and then low-temperature drying and sieving; then adding a lubricant, stirring uniformly, and sieving to obtain the iron-nickel composite powder to be pressed;

[0011] (5) Pressing and annealing: pressing the iron-nickel composite magnetic powder into a ring shape, and then performing high-temperature annealing after the pressing is completed to obtain the gradient functionalized high-performance iron-nickel magnetic powder core.

[0012] In step (1), the iron-nickel magnetic powder raw material is preferably 200-mesh FeNi5.5 alloy powder and 400-mesh FeNi5.5 alloy powder, wherein the tapping frequency of the tapping vibrating screen is 140-160 times / min, the tapping time is 30-60 min, and the screen mesh is 100-400 mesh;

[0013] Further, in step (1), the particle size grading combination is -200 mesh to +325 mesh : -325 mesh to +400 mesh : -400 mesh = (30%-50%) : (20%-30%) : (20%-50%) based on 100% of the iron-nickel powder with the graded particle size;

[0014] As a preferred, the particle size grading combination is -200 mesh to +325 mesh : -325 mesh to +400 mesh : -400 mesh = 50% : 20% : 30%;

[0015] In step (2), 2-5 parts by mass of quartz powder are added to every 500 parts by mass of iron-nickel powder, and the ball milling time is 10-30 min;

[0016] In step (3), 0.2-2 parts by mass of phosphoric acid, 0.5-5 parts by mass of silica sol and 5-25 parts by mass of ethanol are added to 500 parts by mass of the iron-nickel powder, and the stirring time is 5-10 min.

[0017] Further, in step (3), the rotating instrument speed is 60-80 r / min, the reaction temperature is 120-160 DEG C, the reaction time is 40-80 min, and the screen mesh is 60-100 mesh.

[0018] In step (4), the addition amount of the silicone resin solution is 0.3-0.9% based on the iron-nickel composite powder, and the addition amount of the anhydrous ethanol is 3-6%; the stirring time is 10-20 min, the drying temperature is 60-120 DEG C, the drying time is 30-60 min, and the screen mesh is 100 mesh.

[0019] Further, in step (4), the addition amount of the lubricant is 0.4-0.8 wt% based on the iron-nickel composite powder, and the lubricant is one or more of zinc stearate, aluminum stearate, magnesium stearate and paraffin.

[0020] In step (5), the outer diameter of the pressed magnetic powder core is 26.80-27.20 mm, the inner diameter is 14.50-14.80 mm, the height is 10.95-11.20 mm, the pressing pressure is 18-20 t / cm 2 , the annealing temperature is 680-770 DEG C, and the annealing time is 5-8 h.

[0021] The application provides a gradient functionalized high-performance iron-nickel magnetic powder core and a preparation method.

[0022] The iron-nickel powder is screened according to particle size, and mixed according to a specific particle size ratio, so that a dense packing structure is formed between the powders, the distribution of the air gap in the magnetic core is adjusted, and the magnetic core loss is effectively reduced.

[0023] Then, the quartz powder is physically coated on the surface of the iron-nickel powder particles through ball milling, the ball milling produces strong impact, shearing and compression effects, the quartz powder particles repeatedly collide, deform, cold weld, break and finally adhere / embed into the surface of the relatively soft iron-nickel powder particles, so that a high-density inorganic layer is formed on the surface, the electron migration path is blocked, and the metal oxidation / corrosion reaction is inhibited.

[0024] Further, after annealing, the porosity of the coating layer is reduced, residual stress in cold pressing is eliminated, and the risk of magnetic powder core cracking is reduced; in addition, the organic binder can promote crosslinking and curing during annealing, and enhance the interlayer bonding strength.

[0025] The annealing treatment can promote the amorphous oxide coating layer such as quartz powder to transform into a crystalline state, reduce structural defects, and densify; the phosphate coating layer is dehydrated and polymerized to convert into pyrophosphate crystals, which increases the resistivity and reduces the eddy current loss.

[0026] Further, after annealing, the porosity of the coating layer is reduced, residual stress in cold pressing is eliminated, and the risk of magnetic powder core cracking is reduced; in addition, the organic binder can promote crosslinking and curing during annealing, and enhance the interlayer bonding strength.

[0027] The present application provides a kind of gradient functionalization high-performance iron-nickel magnetic powder core and preparation method, compared with prior art, with the following beneficial effects:

[0028] 1, the present application adopts multi-insulation coating method, through "gradient functionalization" design, form quartz-phosphate-nanosilica ternary coating layer on the surface of iron-nickel powder particles, block electron migration path through quartz layer, provide flexible buffer interface through phosphate-nanosilica composite coating layer, obtain dense, uniform thickness and thin gradient functionalization coating layer, effectively reduce the problem of direct contact between particles leading to electric conduction or electromagnetic interference, the obtained iron-nickel magnetic powder core has good DC bias performance (94.6%, 100Oe), and low power loss (95.6kw / m 3 , 50kHz*100mT);

[0029] 2, in the present application, coating agent selection aspect, silica sol has the characteristics of high temperature resistance, good dispersibility, good permeability and low viscosity, which is beneficial to firm adhesion and uniform coating on the surface of iron-nickel powder particles, and forms a layer of non-magnetic material coating layer on the surface of iron-nickel particles together with phosphoric acid;

[0030] 3, the preparation method of the iron-nickel magnetic powder core of the present application realizes "gradient functionalization" design on the surface of iron-nickel powder particles, and the preparation method is simple and economical, on the one hand, organic silicon resin is used as binder, which can be compatible with solvents such as ethanol and water, reducing cost and process hazards; on the other hand, the silica sol used for passivation coating has certain adhesion, which can reduce the amount of binder, thereby reducing the cost. DETAILED DESCRIPTION

[0031] The technical solutions of the present application are further described in detail below through specific examples.

[0032] Example 1

[0033] (1) Particle size grading: 500 g of 200 mesh 200 g of 400 mesh iron-nickel powder was placed in a tap vibration screen, the tap vibration screen time was set to 60 min, the screen was 200 mesh, 325 mesh and 400 mesh for tap screening, then the screened iron-nickel powder was mixed in a ratio of -200 mesh to +325 mesh: -325 mesh to +400 mesh: -400 mesh = 5:2:3, to obtain the particle size graded iron-nickel powder;

[0034] (2) Primary passivation coating: 2.5 g of quartz powder and 500 g of particle size graded iron-nickel powder were placed in a ball mill together and ball milled for 20 min to obtain a primary passivation coated iron-nickel powder;

[0035] (3) Secondary passivation coating: 1 g of phosphoric acid, 2 g of silica sol and 15 g of absolute ethanol were mixed, then the solution was added to 500 g of the primary passivation coated iron-nickel powder, stirred uniformly and then placed in a rotary instrument for reaction, the reaction temperature was 150°C and the reaction time was 60 min; after the reaction was completed, the powder was taken out and dried, then sieved through a 100 mesh sieve to obtain a secondary passivation coated iron-nickel powder;

[0036] (4) Bonding and lubrication: 1.5 g of silicone resin solution and 15 g of absolute ethanol were mixed, then the mixed solution was added to the coated iron-nickel powder of step (3), stirred uniformly, then placed in a 60°C oven and dried for 30 min, then sieved through a 100 mesh sieve after cooling; 2 g of zinc stearate powder was added to 500 g of the bonded iron-nickel powder, mixed and stirred uniformly, then sieved through a 100 mesh sieve to obtain the iron-nickel composite powder to be pressed;

[0037] (5) Pressing and annealing: the iron-nickel composite powder was pressed into a magnetic ring with an outer diameter of 27.00 mm, an inner diameter of 14.70 mm and a height of 11.00 mm, the pressure was 18 t / cm 2 , after pressing, it was subjected to high temperature annealing, the annealing temperature was 680°C and the annealing time was 8 h, to obtain a gradient functionalized high performance iron-nickel magnetic powder core with uniform and complete coating.

[0038] Comparative Example 1

[0039] The difference between this comparative example and Example 1 is that the iron-nickel raw powder used is 200 mesh and does not use tap vibration screening for particle size grading.

[0040] Comparative Example 2.

[0041] The difference between the present comparative example and Example 1 is that only phosphoric acid is used as the coating reagent in the secondary passivation coating, and no silica sol is added for joint coating.

[0042] Comparative Example 3

[0043] The difference between the present comparative example and Example 1 is that only silica sol is used as the powder coating reagent in the secondary passivation coating, and no phosphoric acid is added for joint coating.

[0044] Comparative Example 4

[0045] The difference between the present comparative example and Example 1 is that no primary passivation coating is performed using quartz powder, and only secondary coating is performed.

[0046] The core composite powders obtained in Example 1 and Comparative Examples 1-4 are pressed into magnetic rings with an outer diameter of 27.00 mm, an inner diameter of 14.70 mm, and a height of 11.10±0.10 mm. After high-temperature heat treatment, the magnetic rings are wound with coils for testing. The magnetic permeability and DC bias performance are calculated by testing the inductance value of the magnetic ring. The magnetic ring loss performance is also tested.

[0047] The performance test results of Example 1 and Comparative Examples 1-4 are shown in Table 1.

[0048] Table 1 Performance test results of Example 1 and Comparative Examples 1-4

[0049] As can be seen from the test results in Table 1, comparing Example 1 with Comparative Example 1, it can be concluded that the present application can effectively reduce the loss of iron-nickel magnetic powder core and improve the stacking performance of iron-nickel magnetic powder core by using a tap-type vibrating screen to screen and grade the iron-nickel raw powder. This is because after particle size grading, the magnetic powder is more densely distributed during pressing, which improves the density of the pressed magnetic powder core, thereby reducing the loss and improving the DC bias performance.

[0050] Comparing Example 1 with Comparative Examples 2-4, it can be concluded that the present application has excellent coating effect by using a mixed solution of quartz powder, phosphoric acid, and silica sol for gradient multi-insulation coating. The DC bias performance and loss performance of the coated iron-nickel magnetic powder core are very excellent. This is because the quartz powder is coated on the surface of the metal particles through ball milling, and then a passivation coating layer is formed on the surface of the iron-nickel powder particles through reaction and passivation of phosphoric acid. The silica sol has certain adhesion and high-temperature resistance, and can firmly adhere and fill into the micropores of the phosphoric acid insulation layer, making the coating layer more uniform and stable, and the iron-nickel coated powder more stable under high temperature and high pressure, thereby improving the stability and loss performance of the iron-nickel magnetic powder core.

[0051] Example 2

[0052] (1) Particle size grading: 500 g of 200 mesh 200 g of 400 mesh iron-nickel powder was placed in a tap vibration screen, the tap vibration screen time was set to 60 min, the screen was 200 mesh, 325 mesh and 400 mesh for tap screening, then the screened iron-nickel powder was mixed in a ratio of -200 mesh to +325 mesh: -325 mesh to +400 mesh: -400 mesh = 5:2:3 to obtain the particle size graded iron-nickel powder;

[0053] (2) Primary passivation coating: 4 g of quartz powder and 500 g of particle size graded iron-nickel powder were placed in a ball mill together and ball milled for 20 min to obtain the primary passivation coated iron-nickel powder;

[0054] (3) Secondary passivation coating: 1 g of phosphoric acid, 3 g of silica sol and 15 g of absolute ethanol were mixed, then the solution was added to 500 g of the primary passivation coated iron-nickel powder, stirred uniformly and then placed in a rotary instrument for reaction, the reaction temperature was 150°C and the reaction time was 60 min; after the reaction was completed, the powder was taken out and dried, then sieved through a 100 mesh sieve to obtain the secondary passivation coated iron-nickel powder;

[0055] (4) Bonding and lubrication: 3 g of silicone resin solution and 15 g of absolute ethanol were mixed, then the mixed solution was added to the coated iron-nickel powder in step (2), stirred uniformly, then placed in a 60°C oven and dried for 30 min, then sieved through a 100 mesh sieve after cooling; 2 g of zinc stearate powder was added to 500 g of the bonded iron-nickel powder, mixed and stirred uniformly, then sieved through a 100 mesh sieve to obtain the iron-nickel composite powder to be pressed;

[0056] (5) Pressing and annealing: the iron-nickel composite powder was pressed into a magnetic ring with an outer diameter of 27.00 mm, an inner diameter of 14.70 mm and a height of 11.00 mm, the pressure was 20 t / cm 2 , after pressing, high temperature annealing was performed, the annealing temperature was 770°C and the annealing time was 5 h, to obtain the gradient functionalized high performance iron-nickel magnetic powder core which was uniformly and completely coated.

[0057] Comparative Example 5 is as follows:

[0058] The difference between this comparative example and Example 2 is that the particle size grading ratio after tap vibration screening is -200 mesh to +325 mesh: -325 mesh to +400 mesh: -400 mesh = 7:2:1.

[0059] Comparative Example 6 is as follows:

[0060] The difference between this comparative example and Example 2 is that the amount of phosphoric acid used in the secondary passivation coating is 2 g and the amount of silica sol used is 8 g, after stirring uniformly with the iron-nickel magnetic powder, the reaction was carried out in a rotary instrument, the reaction temperature was 180°C.

[0061] Comparative Example 7 is as follows:

[0062] The difference between this comparative example and Example 2 is that after the phosphoric acid and silica sol are used to coat together, no organic silicon resin is used for bonding.

[0063] The iron-nickel composite powder obtained in Example 2 and Comparative Examples 5, 6 and 7 is pressed into a magnetic ring with an outer diameter of 27.00 mm, an inner diameter of 14.70 mm and a height of 11.10±0.10 mm. After heat treatment, the magnetic ring is wound with a coil, and the inductance value of the magnetic ring is tested to calculate the magnetic permeability and DC bias performance. At the same time, the loss performance of the magnetic ring is tested.

[0064] The performance test results of Example 2 and Comparative Examples 5-7 are shown in Table 2.

[0065] Table 2 Performance test results of Example 2 and Comparative Examples 5-7

[0066] From the test results in Table 2, it can be seen that by comparing Example 2 with Comparative Example 5, it can be concluded that different particle size grading formulations have a great influence on the inductance and superposition performance of metal magnetic powder particles. The particle size grading formulation of Example 2 is the best in the present application. By comparing Example 2 with Comparative Example 6, it can be concluded that the ratio of coated reagents and the reaction temperature of the powder have a great influence on the magnetic permeability and superposition performance of iron-nickel magnetic powder. Only the appropriate ratio of coated reagents and reaction temperature can maintain low loss while maintaining good DC bias characteristics. By comparing Example 2 with Comparative Example 7, it can be concluded that the use of a bonding agent only affects the magnetic permeability performance of iron-nickel metal powder and does not cause an increase in magnetic powder loss and a decrease in DC bias characteristics, indicating that quartz powder, phosphoric acid and silica sol are the main insulation reagents in the process of the present application.

[0067] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limited thereto. Although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that the specific embodiments of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application. Any modification or equivalent replacement that does not depart from the spirit and scope of the present application should be covered in the scope of the claims of the present application.

Claims

1. A method for preparing a gradient functionalized high-performance iron-nickel magnetic powder core, characterized in that: The following steps are involved: (1) Particle size grading: Screening of iron-nickel powders followed by particle size grading; (2) Primary passivation coating: adding quartz powder to the iron-nickel powder with good particle size distribution, and coating the surface of the iron-nickel powder with a first passivation layer; (3) Secondary passivation coating: adding a mixed solution of phosphoric acid and silica sol to the iron-nickel powder coated with the first passivation layer, and coating the surface of the iron-nickel powder with a second passivation layer; (4) bonding and lubrication: adding a binder and a lubricant to the iron-nickel powder coated with the second passivation layer in sequence to obtain an iron-nickel composite powder; (5) Pressing and annealing: The iron-nickel composite powder is pressed into shape and then annealed to obtain a gradient functionalized high-performance iron-nickel magnetic powder core.

2. The method for preparing a gradient functionalized high-performance iron-nickel magnetic powder core according to claim 1, wherein: In the step (1), the iron-nickel powder is 200-mesh and 400-mesh FeNi5.5 alloy powder, which is subjected to particle size screening by a slapping vibration screen, with the slapping frequency being 140-160 times / min, the slapping time being 30-60 min, and the screen mesh being 100-400 mesh.

3. The method for preparing a gradient functionalized high-performance iron-nickel magnetic powder core according to claim 1, wherein: In the step (1), taking the iron-nickel powder with good particle size distribution as 100%, the particle size distribution combination is: -200 mesh to +325 mesh: -325 mesh to +400 mesh: -400 mesh = (30%~50%): (20%~30%): (20%~50%).

4. The method for preparing a gradient functionalized high-performance iron-nickel magnetic powder core according to claim 3, wherein: In the step (1), taking the iron-nickel powder with good particle size distribution as 100%, the particle size distribution combination is: -200 mesh to +325 mesh: -325 mesh to +400 mesh: -400 mesh = 50%: 20%: 30%.

5. The method for preparing a gradient functionalized high-performance iron-nickel magnetic powder core according to claim 1, wherein: The step (2) is carried out in a ball mill, the ball milling time is 10-30 min, and the mass ratio of iron-nickel powder to quartz powder is 500:(2-5).

6. The method for preparing a gradient functionalized high-performance iron-nickel magnetic powder core according to claim 1, wherein: The step (3) is carried out in a rotating instrument at a rotation speed of 60-80 r / min, a reaction temperature of 120-160° C., and a reaction time of 40-80 min. After completion, the reaction is cooled and sieved with a sieve of 60-100 mesh. The mixed solution of phosphoric acid and silica sol uses ethanol as a solvent, and the mass ratio of iron-nickel powder, phosphoric acid, silica sol and ethanol is 500:(0.2-2):(0.5-5):(5-25).

7. The method for preparing a gradient functionalized high-performance iron-nickel magnetic powder core according to claim 1, wherein: In the step (4), after adding the binder, stirring is carried out for 10 to 20 minutes, drying is carried out at 60 to 120° C. for 30 to 60 minutes, and passing through a 100-mesh sieve; the binder is an ethanol solution of an organic silicone resin, and based on the iron-nickel composite powder, the addition amount of the organic silicone resin is 0.3 to 0.9 wt%, and the addition amount of anhydrous ethanol is 3 to 6%.

8. The method for preparing a gradient functionalized high-performance iron-nickel magnetic powder core according to claim 1, wherein: In the step (4), after adding the lubricant, stirring and sieving, the lubricant is one or more of zinc stearate, aluminum stearate, magnesium stearate, and paraffin, and the added amount is 0.4-0.8wt% of the iron-nickel composite powder.

9. The method for preparing a gradient functionalized high-performance iron-nickel magnetic powder core according to claim 1, wherein: In the step (5), the iron-nickel composite powder is pressed into a magnetic ring with an outer diameter of 26.80-27.20 mm, an inner diameter of 14.50-14.80 mm, and a height of 10.95-11.20 mm, wherein the pressing pressure is 18-20 t / cm 2 , the annealing temperature is 680~770℃, and the annealing time is 5~8h.

10. A gradient functionalized high performance iron-nickel magnetic powder core, characterized in that: The magnetic powder core is prepared by the method for preparing a gradient functionalized high-performance iron-nickel magnetic powder core according to any one of claims 1 to 9.

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