A soft magnetic powder core with permeability μ of 9 and its preparation method

Abstract

This invention belongs to the field of soft magnetic materials technology, specifically relating to an iron-silicon soft magnetic powder core with a permeability μ of 9 and its preparation method. The method includes the following steps: iron-silicon powder particle size distribution, primary insulation coating, powder heat treatment, secondary insulation coating, pressing and molding, core heat treatment, and surface coating; wherein the iron-silicon powder particle size distribution is as follows: -120 to +200 mesh 34.1%, -200 to +325 mesh 30.8%, -325 to +400 mesh 10%, and below -400 mesh 25.1%, and the powders are mixed uniformly according to the above proportions. The iron-silicon soft magnetic powder core prepared by this method has low permeability and good DC bias performance, making it particularly suitable for use in high-current power equipment and suitable for widespread application.

Description

Technical Field

[0001] This invention belongs to the field of soft magnetic materials technology, specifically relating to an iron-silicon soft magnetic powder core with a magnetic permeability μ of 9 and its preparation method. Background Technology

[0002] Iron-silicon soft magnetic powder cores possess excellent DC bias characteristics, a saturation magnetic flux density as high as 16,000 Gauss, good temperature stability, and high energy storage capacity. They are particularly suitable for applications in home appliances, UPS power supplies, photovoltaic inverters, new energy vehicles (OBC), wind power, and hydropower generation.

[0003] Currently, the main production processes for iron-silicon powder are gas atomization, water atomization, and mechanical crushing. Mechanical crushing has been phased out of the market because it cannot meet performance requirements. Water-atomized iron-silicon powder has an irregular shape (…). Figure 1 The surface has many sharp edges, which places higher demands on the powder insulation coating. Furthermore, the sharp edges are squeezed together during the pressing process, easily damaging the insulation layer and resulting in high core loss. However, gas-atomized iron-silicon powder is spherical in shape (…). Figure 2 The oxygen content of the powder is relatively easy to control, resulting in a high DC superposition and low loss in the produced magnetic core.

[0004] Patent CN102543345B discloses a method for manufacturing iron-silicon-aluminum soft magnetic powder cores. This process requires heating the powder to 80℃~120℃ and then pouring it into a phosphoric acid passivation solution for passivation. Although the insulation process is simple and the production efficiency is high, it cannot produce lower magnetic permeability.

[0005] Therefore, how to develop a soft magnetic powder core with low permeability, good DC bias performance, and particularly suitable for use in high-current power equipment is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention aims to overcome the above-mentioned deficiencies in the prior art and provides a method for preparing an iron-silicon soft magnetic powder core with a permeability μ of 9. The iron-silicon soft magnetic powder core prepared by this method has low loss and good DC bias performance.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A soft magnetic powder core with a permeability μ of 9 is disclosed. The core is made from iron-silicon powder of a specific particle size distribution, through a process involving primary insulation coating, powder heat treatment, secondary insulation coating, pressing, core heat treatment, and surface coating.

[0009] The particle size distribution of the iron-silicon powder is as follows: -120~+200 mesh accounts for 34.1%, -200~+325 mesh accounts for 30.8%, -325~+400 mesh accounts for 10%, and below -400 mesh accounts for 25.1%.

[0010] It should be noted that because coarser powder particles result in a smaller compression ratio and a smaller powder filling, the height of the pressed magnetic core is higher, thus increasing the permeability; conversely, finer powder particles result in a larger compression ratio and a smaller pressed magnetic core height, thus decreasing the permeability.

[0011] Optionally, the iron-silicon soft magnetic core uses gas-atomized iron-silicon powder, and the silicon content in the iron-silicon powder is 5% to 6%, with the remainder being iron.

[0012] Optionally, the insulating coating uses phosphoric acid, alcohol, water, kaolin, potassium silicate, and lignin to form a phosphate, silicate, and silicon oxide insulating layer on the surface of the iron-silicon powder.

[0013] Furthermore, this invention also claims protection for a method for preparing an iron-silicon soft magnetic powder core with a permeability μ of 9 as described above, specifically comprising the following steps:

[0014] 1) Primary insulation coating: Mix the atomized iron-silicon powder evenly, pour in the mixed insulating liquid of phosphoric acid, alcohol and water, and heat and dry it after the chemical reaction of the powder is completed.

[0015] 2) Powder heat treatment: The iron-silicon powder after the first insulation coating in step 1) is heat treated in a tunnel furnace and protected by a first protective gas for later use;

[0016] 3) Secondary insulation coating: Pour the powder after heat treatment in step 2) into the insulation equipment, add kaolin and stir evenly, then add potassium silicate, water and lignin and heat and dry for later use.

[0017] 4) Press molding: Add a release agent to the powder after insulation in step 3), press molding, and set aside;

[0018] 5) Core heat treatment: The magnetic core pressed in step 4) is placed in a nitrogen atmosphere for sintering, and then the surface of the magnetic core is spin-coated with epoxy resin powder to obtain the iron-silicon soft magnetic powder core with a permeability μ of 9.

[0019] Optionally, in step 1), the amount of phosphoric acid used is 5-8% of the weight of the iron-silicon powder, the amount of alcohol used is 8% of the weight of the iron-silicon powder, the amount of water used is 11% of the weight of the iron-silicon powder, and the heating temperature is controlled below 130°C, specifically 100°C to 130°C.

[0020] Optionally, in step 2), the heat treatment temperature is 700℃~800℃, the holding time is 30~120min; and the first protective gas is at least one of nitrogen and hydrogen.

[0021] Optionally, in step 3), the amount of kaolin is 8% to 10% of the weight of the iron-silicon powder, the amount of lignin is 1% of the weight of the iron-silicon powder, the amount of potassium silicate is 8% to 10% of the weight of the iron-silicon powder, the amount of water is 12% of the weight of the iron-silicon powder, and the heating temperature is controlled between 100 and 130°C.

[0022] Optionally, in step 4), the release agent is microcrystalline wax or zinc stearate, and the amount of the release agent is 0.2-0.4% of the weight of the iron-silicon powder; and the pressing pressure is 18-22 t / cm. 2 .

[0023] Optionally, in step 5), the nitrogen flow rate is 6m³ / h. 3 / h, sintering temperature is 700℃~780℃, holding time is 30~120min.

[0024] As can be seen from the above technical solutions, compared with the prior art, the iron-silicon soft magnetic powder core with a magnetic permeability μ of 9 and its preparation method disclosed in this invention have the following superior effects:

[0025] (1) The insulation process in this invention is simple, the production efficiency is high, and it can be mass-produced. The preparation process is energy-saving and environmentally friendly, and the product has excellent performance. Moreover, the magnetic core has extremely high DC bias performance and excellent power loss, and the product performance is at the leading level in the industry.

[0026] (2) The present invention uses coarse and fine powders for particle size distribution, wherein -120 mesh to +200 mesh accounts for 34.1%, -200 mesh to +325 mesh accounts for 30.8%, -325 mesh to +400 mesh accounts for 10%, and below -400 mesh accounts for 25.1%. The advantage of coarse and fine powders is that they can improve the density of the magnetic core, reduce the porosity of the magnetic core, and effectively reduce the loss of the magnetic core. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0028] Figure 1 This is a SEM image of water-atomized iron-silicon powder.

[0029] Figure 2 This is a SEM image of gas-atomized iron-silicon powder.

[0030] Figure 3 This is a graph showing the particle size distribution. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] To better understand the present invention, the technical solution of the present invention will be further described below with reference to embodiments. Example 1

[0033] 1) Take atomized iron-silicon powder, in which the silicon content is 5% to 6%, and the particle size distribution of the iron-silicon powder is as follows: -120 mesh to +200 mesh accounts for 34.1%, -200 mesh to +325 mesh accounts for 30.8%, -325 mesh to +400 mesh accounts for 10%, and below -400 mesh accounts for 25.1%. Mix the powder evenly according to the above proportions.

[0034] 2) Primary insulation: Pour the mixed iron-silicon powder into the insulation equipment, then pour in the mixed insulating liquid of phosphoric acid, alcohol, and water. After the iron-silicon powder and the phosphoric acid insulating liquid have completed the chemical reaction, heat and stir-fry until dry. The amount of phosphoric acid is 7% of the weight of the iron-silicon powder, the amount of alcohol is 8% of the weight of the iron-silicon powder, and the amount of water is 11% of the weight of the iron-silicon powder. The heating temperature is controlled between 100 and 130°C.

[0035] 3) Heat treatment of insulating powder: The iron-silicon powder after primary insulating coating is heat-treated in a tunnel furnace. Nitrogen gas is first introduced, followed by hydrogen gas after 20 minutes. The heat treatment is carried out at 750℃ for 50 minutes. The nitrogen gas flow rate is set to 6 m³ / min. 3 / h, hydrogen flow rate set to 2.5m 3 / h;

[0036] 4) Secondary insulation: After heat treatment and cooling, the iron-silicon powder is poured back into the insulation equipment, kaolin is added and stirred evenly, and then a mixed insulating liquid of potassium silicate, lignin and water is added and heated and stir-fried until dry; the amount of kaolin is 8% of the weight of iron-silicon powder, the amount of lignin is 1% of the weight of iron-silicon powder, the amount of potassium silicate is 8% of the weight of iron-silicon powder, and the amount of water is 12% of the weight of iron-nickel powder. The heating temperature is controlled between 100~130℃.

[0037] 5) Compression Molding: Before compression molding, add 0.3% zinc stearate by weight of iron-silicon powder as a release agent, mix evenly, and then press into a magnetic ring of 26.9mm*14.8mm*11.1mm. The molding pressure is 20 tons / square centimeter. The molded magnetic core is placed in a heat treatment furnace, nitrogen is introduced, and it is kept at 760℃ for 50 minutes, and then naturally cooled. The nitrogen flow rate is set to 6m³ / min. 3 / h;

[0038] 6) Epoxy resin powder was spin-coated onto the surface of the magnetic ring, and after curing, a soft magnetic powder core with a permeability μ of 9 was obtained. The magnetic properties of the obtained soft magnetic powder core are shown in Table 1. Example 2

[0039] 1) Take atomized iron-silicon powder, in which the silicon content is 5% to 6%, and the particle size distribution of the iron-silicon powder is as follows: -120 mesh to +200 mesh accounts for 34.1%, -200 mesh to +325 mesh accounts for 30.8%, -325 mesh to +400 mesh accounts for 10%, and below -400 mesh accounts for 25.1%. Mix the powder evenly according to the above proportions.

[0040] 2) Primary insulation: Pour the mixed iron-silicon powder into the insulation equipment, then pour in the mixed insulating liquid of phosphoric acid, alcohol, and water. After the iron-silicon powder and the phosphoric acid insulating liquid have completed the chemical reaction, heat and stir-fry until dry. The amount of phosphoric acid is 7% of the weight of the iron-silicon powder, the amount of alcohol is 8% of the weight of the iron-silicon powder, and the amount of water is 11% of the weight of the iron-silicon powder. The heating temperature is controlled between 100 and 130°C.

[0041] 3) Heat treatment of insulating powder: The iron-silicon powder after primary insulation coating is heat-treated in a tunnel furnace. Nitrogen gas is first introduced, followed by hydrogen gas after 20 minutes. The heat treatment is carried out at 770℃ for 50 minutes. The nitrogen gas flow rate is set to 6 m³ / min. 3 / h, hydrogen flow rate set to 2.5m 3 / h;

[0042] 4) Secondary insulation: After heat treatment and cooling, the iron-silicon powder is poured back into the insulation equipment, kaolin is added and stirred evenly, and then a mixed insulating liquid of potassium silicate, lignin and water is added and heated and stir-fried until dry; the amount of kaolin is 9% of the weight of iron-silicon powder, the amount of lignin is 1% of the weight of iron-silicon powder, the amount of potassium silicate is 7% of the weight of iron-silicon powder, and the amount of water is 12% of the weight of iron-nickel powder. The heating temperature is controlled between 100~130℃.

[0043] 5) Compression Molding: Before compression molding, add 0.3% zinc stearate by weight of iron-silicon powder as a release agent, mix evenly, and then press into a magnetic ring of 26.9mm*14.8mm*11.1mm. The molding pressure is 19 tons / square centimeter. The molded magnetic core is placed in a heat treatment furnace, nitrogen is introduced, and it is held at 740℃ for 50 minutes, and then naturally cooled. The nitrogen flow rate is set to 6m³ / min. 3 / h;

[0044] 6) Epoxy resin powder was spin-coated onto the surface of the magnetic ring, and after curing, a soft magnetic powder core with a permeability μ of 9 was obtained. The magnetic properties of the obtained soft magnetic powder core are shown in Table 1. Example 3

[0045] 1) Take atomized iron-silicon powder, in which the silicon content is 5% to 6%, and the particle size distribution of the iron-silicon powder is as follows: -120 mesh to +200 mesh accounts for 34.1%, -200 mesh to +325 mesh accounts for 30.8%, -325 mesh to +400 mesh accounts for 10%, and below -400 mesh accounts for 25.1%. Mix the powder evenly according to the above proportions.

[0046] 2) Primary insulation: Pour the mixed iron-silicon powder into the insulation equipment, then pour in the mixed insulating liquid of phosphoric acid, alcohol, and water. After the iron-silicon powder and the phosphoric acid insulating liquid have completed the chemical reaction, heat and stir-fry until dry. The amount of phosphoric acid is 8% of the weight of the iron-silicon powder, the amount of alcohol is 8% of the weight of the iron-silicon powder, and the amount of water is 11% of the weight of the iron-silicon powder. The heating temperature is controlled between 100 and 130°C.

[0047] 3) Heat treatment of insulating powder: The iron-silicon powder after primary insulation coating is heat-treated in a tunnel furnace. Nitrogen gas is first introduced, followed by hydrogen gas after 20 minutes. The heat treatment is carried out at 760℃ for 50 minutes. The nitrogen gas flow rate is set to 6 m³ / min. 3 / h, hydrogen flow rate set to 2.5m 3 / h;

[0048] 4) Secondary insulation: After heat treatment and cooling, the iron-silicon powder is poured back into the insulation equipment, kaolin is added and stirred evenly, and then a mixed insulating liquid of potassium silicate, lignin and water is added and heated and stir-fried until dry; the amount of kaolin is 8% of the weight of iron-silicon powder, the amount of lignin is 1% of the weight of iron-silicon powder, the amount of potassium silicate is 7% of the weight of iron-silicon powder, and the amount of water is 12% of the weight of iron-nickel powder. The heating temperature is controlled between 100~130℃.

[0049] 5) Compression Molding: Before compression molding, add 0.4% zinc stearate by weight of iron-silicon powder as a release agent, mix evenly, and then press into a magnetic ring of 26.9mm*14.8mm*11.1mm. The molding pressure is 20 tons / square centimeter. The molded magnetic core is placed in a heat treatment furnace, and nitrogen is introduced and held at 740℃ for 50 minutes, followed by natural cooling. The nitrogen flow rate is set to 6m³ / min. 3 / h;

[0050] 6) Epoxy resin powder was spin-coated onto the surface of the magnetic ring, and after curing, a soft magnetic powder core with a permeability μ of 9 was obtained. The magnetic properties of the obtained soft magnetic powder core are shown in Table 1. Example 4

[0051] 1) Take atomized iron-silicon powder, in which the silicon content is 5% to 6%, and the particle size distribution of the iron-silicon powder is as follows: -120 mesh to +200 mesh accounts for 34.1%, -200 mesh to +325 mesh accounts for 30.8%, -325 mesh to +400 mesh accounts for 10%, and below -400 mesh accounts for 25.1%. Mix the powder evenly according to the above proportions.

[0052] 2) Primary insulation: Pour the mixed iron-silicon powder into the insulation equipment, then pour in the mixed insulating liquid of phosphoric acid, alcohol, and water. After the iron-silicon powder and the phosphoric acid insulating liquid have completed the chemical reaction, heat and stir-fry until dry. The amount of phosphoric acid is 5% of the weight of the iron-silicon powder, the amount of alcohol is 8% of the weight of the iron-silicon powder, and the amount of water is 11% of the weight of the iron-silicon powder. The heating temperature is controlled between 100 and 130°C.

[0053] 3) Heat treatment of insulating powder: The iron-silicon powder after primary insulating coating is heat-treated in a tunnel furnace. Nitrogen gas is first introduced, followed by hydrogen gas after 20 minutes. The heat treatment is carried out at 740℃ for 50 minutes; the nitrogen gas flow rate is set to 6 m³ / min. 3 / h, hydrogen flow rate set to 2.5m 3 / h;

[0054] 4) Secondary insulation: After heat treatment and cooling, the iron-silicon powder is poured back into the insulation equipment, kaolin is added and stirred evenly, and then a mixed insulating liquid of potassium silicate, lignin and water is added and heated and stir-fried until dry; the amount of kaolin is 10% of the weight of iron-silicon powder, the amount of lignin is 1% of the weight of iron-silicon powder, the amount of potassium silicate is 10% of the weight of iron-silicon powder, and the amount of water is 12% of the weight of iron-nickel powder. The heating temperature is controlled between 100~130℃.

[0055] 5) Before pressing, add 0.4% zinc stearate by weight of iron-silicon powder as a release agent, mix evenly, and press into a magnetic ring of 26.9mm*14.8mm*11.1mm. The pressing pressure is 22 tons / square centimeter. Place the formed magnetic core into a heat treatment furnace, purge with nitrogen, and hold at 780℃ for 50 minutes, then allow to cool naturally. The nitrogen flow rate is set to 6m³ / min. 3 / h;

[0056] 6) Epoxy resin powder was spin-coated onto the surface of the magnetic ring, and after curing, a soft magnetic powder core with a permeability μ of 9 was obtained. The magnetic properties of the obtained soft magnetic powder core are shown in Table 1. Example 5

[0057] 1) Take atomized iron-silicon powder, in which the silicon content is 5% to 6%, and the particle size distribution of the iron-silicon powder is as follows: -120 mesh to +200 mesh accounts for 34.1%, -200 mesh to +325 mesh accounts for 30.8%, -325 mesh to +400 mesh accounts for 10%, and below -400 mesh accounts for 25.1%. Mix the powder evenly according to the above proportions.

[0058] 2) Primary insulation: Pour the mixed iron-silicon powder into the insulation equipment, then pour in the mixed insulating liquid of phosphoric acid, alcohol, and water. After the iron-silicon powder and the phosphoric acid insulating liquid have completed the chemical reaction, heat and stir-fry until dry. The amount of phosphoric acid is 6% of the weight of the iron-silicon powder, the amount of alcohol is 8% of the weight of the iron-silicon powder, and the amount of water is 11% of the weight of the iron-silicon powder. The heating temperature is controlled between 100 and 130°C.

[0059] 3) Heat treatment of insulating powder: The iron-silicon powder after primary insulating coating is heat-treated in a tunnel furnace. Nitrogen gas is first introduced, followed by hydrogen gas after 20 minutes. The heat treatment is carried out at 750℃ for 50 minutes. The nitrogen gas flow rate is set to 6 m³ / min. 3 / h, hydrogen flow rate set to 2.5m 3 / h;

[0060] 4) Secondary insulation: After heat treatment and cooling, the iron-silicon powder is poured back into the insulation equipment, kaolin is added and stirred evenly, and then a mixed insulating liquid of potassium silicate, lignin and water is added and heated and stir-fried until dry; the amount of kaolin is 9% of the weight of iron-silicon powder, the amount of lignin is 1% of the weight of iron-silicon powder, the amount of potassium silicate is 9% of the weight of iron-silicon powder, and the amount of water is 12% of the weight of iron-nickel powder. The heating temperature is controlled between 100~130℃.

[0061] 5) Compression Molding: Before compression molding, add 0.3% zinc stearate by weight of iron-silicon powder as a release agent, mix evenly, and then press into a magnetic ring of 26.9mm*14.8mm*11.1mm. The molding pressure is 21 tons / cm². The molded magnetic core is placed in a heat treatment furnace, nitrogen is introduced, and it is kept at 760℃ for 50 minutes, and then naturally cooled. The nitrogen flow rate is set to 6m³ / min. 3 / h;

[0062] 6) Epoxy resin powder was spin-coated onto the surface of the magnetic ring, and after curing, a soft magnetic powder core with a permeability μ of 9 was obtained. The magnetic properties of the obtained soft magnetic powder core are shown in Table 1.

[0063] Table 1. Magnetic properties of the iron-silicon soft magnetic powder cores obtained in Examples 1-5

[0064]

[0065] As shown in Table 1, the iron-silicon soft magnetic powder core with a permeability μ of 9 prepared using this method exhibits a DC bias performance of over 90% under a DC bias of 200 Oe; the power loss at 100 kHz and 30 mT is 300 mW / cm. 3 Its performance is among the best in the industry. Example 6

[0066] 1) Take atomized iron-silicon powder, in which the silicon content is 5% to 6%, and the particle size distribution of the iron-silicon powder is as follows: -120 mesh to +200 mesh accounts for 34.1%, -200 mesh to +325 mesh accounts for 30.8%, -325 mesh to +400 mesh accounts for 10%, and below -400 mesh accounts for 25.1%. Mix the powder evenly according to the above proportions.

[0067] 2) Primary insulation: Pour the mixed iron-silicon powder into the insulation equipment, then pour in the mixed insulating liquid of phosphoric acid, alcohol, and water. After the iron-silicon powder and the phosphoric acid insulating liquid have completed the chemical reaction, heat and stir-fry until dry. The amount of phosphoric acid is 6% of the weight of the iron-silicon powder, the amount of alcohol is 8% of the weight of the iron-silicon powder, and the amount of water is 11% of the weight of the iron-silicon powder. The heating temperature is controlled between 100 and 130°C.

[0068] 3) Heat treatment of insulating powder: The iron-silicon powder after primary insulating coating is heat-treated in a tunnel furnace. Nitrogen gas is first introduced, followed by hydrogen gas after 20 minutes. The heat treatment is carried out at 740℃ for 50 minutes. The nitrogen gas flow rate is set to 4 m³ / min. 3 / h, hydrogen flow rate set to 2.5m 3 / h;

[0069] 4) Secondary insulation: After heat treatment and cooling, the iron-silicon powder is poured back into the insulation equipment, kaolin is added and stirred evenly, and then a mixed insulating liquid of potassium silicate, lignin and water is added and heated and stir-fried until dry; the amount of kaolin is 9% of the weight of iron-silicon powder, the amount of lignin is 1% of the weight of iron-silicon powder, the amount of potassium silicate is 9% of the weight of iron-silicon powder, and the amount of water is 12% of the weight of iron-nickel powder. The heating temperature is controlled between 100~130℃.

[0070] 5) Compression Molding: Before compression molding, add 0.3% zinc stearate by weight of iron-silicon powder as a release agent, mix evenly, and then press into magnetic rings of 26.9mm*14.8mm*11.1mm. The molding pressure is 18, 19, 20, 21, and 22 tons / cm². The molded magnetic core is placed in a heat treatment furnace, nitrogen is introduced, and it is held at 740℃ for 50 minutes, followed by natural cooling. The nitrogen flow rate is set to 6 m³ / min. 3 / h;

[0071] 6) Epoxy resin powder was spin-coated onto the surface of the magnetic ring, and after curing, a soft magnetic powder core with a permeability μ of 9 was obtained. The magnetic properties of the obtained soft magnetic powder core are shown in Table 2. The test results show that the higher the pressure, the lower the core loss and the better the DC superposition.

[0072] Table 2 Magnetic properties of iron-silicon soft magnetic powder cores obtained by pressing under different pressures

[0073]

[0074] As shown in Table 2, under the same insulation coating process and heat treatment temperature conditions, the higher the pressure, the higher the magnetic permeability μ value of the magnetic core, and the better the DC superposition and loss. Moreover, within the pressure range that the mold can withstand, the higher the pressure, the better the magnetic core performance. Example 7

[0075] 1) Take atomized iron-silicon powder with a silicon content of 5% to 6%. The particle size distribution of the iron-silicon powder is as follows: -120 mesh to +200 mesh accounts for 34.1%, -200 mesh to +325 mesh accounts for 30.8%, -325 mesh to +400 mesh accounts for 10%, and below -400 mesh accounts for 25.1%. Mix the powder evenly according to the above proportions.

[0076] 2) Primary insulation: Pour the mixed iron-silicon powder into the insulation equipment, then pour in the mixed insulating liquid of phosphoric acid, alcohol, and water. After the iron-silicon powder and the phosphoric acid insulating liquid have completed the chemical reaction, heat and stir-fry until dry. The amount of phosphoric acid is 7% of the weight of the iron-silicon powder, the amount of alcohol is 7% of the weight of the iron-silicon powder, and the amount of water is 4% of the weight of the iron-silicon powder. The heating temperature is controlled between 100 and 130°C.

[0077] 3) Heat treatment of insulating powder: The iron-silicon powder after primary insulation coating is heat-treated in a tunnel furnace. Nitrogen gas is first introduced, followed by hydrogen gas after 20 minutes. The heat treatment is carried out at 740℃ for 50 minutes. The nitrogen gas flow rate is set to 6 m³ / min. 3 / h, hydrogen flow rate set to 2.5m 3 / h;

[0078] 4) Secondary insulation: After the heat treatment and cooling, the iron-silicon powder is poured back into the insulation equipment, kaolin is added and stirred evenly, and then a mixed insulation liquid of potassium silicate, lignin and water is added and heated and stir-fried until dry; the amount of kaolin is 5% of the weight of iron-silicon powder, the amount of lignin is 1% of the weight of iron-silicon powder, the amount of potassium silicate is 6% of the weight of iron-silicon powder, and the amount of water is 10% of the weight of iron-nickel powder. The heating temperature is controlled between 100 and 130°C.

[0079] 5) Compression Molding: Before compression molding, add 0.4% zinc stearate by weight of iron-silicon powder as a release agent, mix evenly, and then press into magnetic rings measuring 26.9mm*14.8mm*11.1mm. The molding pressure is 21 tons / square centimeter. The molded magnetic core is placed in a heat treatment furnace, and nitrogen gas is introduced and held at 680℃, 720℃, 740℃, 760℃, and 780℃ for 50 minutes respectively, followed by natural cooling. The nitrogen gas flow rate is set to 6 m³ / min. 3 / h;

[0080] 6) Epoxy resin powder was spin-coated onto the surface of the magnetic ring, and after curing, an iron-silicon soft magnetic powder core with a permeability μ of 9 was obtained. The magnetic properties of the obtained iron-silicon soft magnetic powder core are shown in Table 3.

[0081] Table 3 Magnetic properties of iron-silicon soft magnetic powder cores obtained at different annealing temperatures

[0082]

[0083] As shown in Table 3, under the same insulation coating process and pressure, the higher the heat treatment temperature, the higher the magnetic permeability of the core, while the DC superposition and loss begin to deteriorate; the lower the heat treatment temperature, the lower the magnetic permeability, while the DC superposition improves, but the loss also begins to deteriorate; and the loss and DC superposition performance are best when the heat treatment temperature is between 720℃ and 740℃.

[0084] Furthermore, the relationship between particle size distribution and powder compression ratio is shown in Tables 4 and 5 below.

[0085] Table 4

[0086]

[0087] Table 5

[0088]

[0089] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A soft magnetic powder core of iron-silicon with a permeability μ of 9, characterized in that, The iron-silicon soft magnetic powder core is made from iron-silicon powder according to a particle size distribution, and through a process of primary insulation coating, powder heat treatment, secondary insulation coating, pressing, core heat treatment, and surface coating; wherein, The particle size distribution of the iron-silicon powder is as follows: -120 to +200 mesh accounts for 34.1%, -200 to +325 mesh accounts for 30.8%, -325 to +400 mesh accounts for 10%, and below -400 mesh accounts for 25.1%. The preparation method of the iron-silicon soft magnetic powder core with a permeability μ of 9 specifically includes the following steps: 1) Primary insulation coating: Mix the gas-atomized iron-silicon powder evenly, pour in the mixed insulating liquid of phosphoric acid, alcohol and water, and heat and dry it after the chemical reaction of the powder is completed, then set aside. 2) Powder heat treatment: The iron-silicon powder after the first insulation coating in step 1) is heat treated in a tunnel furnace and protected by a first protective gas for later use. 3) Secondary insulation coating: Pour the powder after heat treatment in step 2) into the insulation equipment, add kaolin and stir evenly, then add potassium silicate, water and lignin and heat and dry for later use. 4) Press molding: Add a release agent to the powder after insulation in step 3), press molding, and set aside; 5) Core heat treatment: The magnetic core pressed in step 4) is placed in a nitrogen atmosphere for sintering, and then epoxy resin powder is spin-coated on the surface of the magnetic core to obtain the iron-silicon soft magnetic powder core with a magnetic permeability μ of 9. In step 2), the heat treatment temperature is 700℃~800℃, the holding time is 30~120min; and the first protective gas is at least one of nitrogen and hydrogen. The iron-silicon soft magnetic core uses gas-atomized iron-silicon powder, and the silicon content in the iron-silicon powder is 5% to 6%, with the remainder being iron. In step 1), the amount of phosphoric acid used is 5-8% of the weight of the iron-silicon powder, the amount of alcohol used is 8% of the weight of the iron-silicon powder, the amount of water used is 11% of the weight of the iron-silicon powder, and the heating temperature is 100℃-130℃. In step 3), the amount of kaolin used is 8% to 10% of the weight of the iron-silicon powder, the amount of lignin used is 1% of the weight of the iron-silicon powder, the amount of potassium silicate used is 8% to 10% of the weight of the iron-silicon powder, the amount of water used is 12% of the weight of the iron-silicon powder, and the heating temperature is 100℃ to 130℃.

2. The iron-silicon soft magnetic powder core with a permeability μ of 9 according to claim 1, characterized in that, The insulating coating uses phosphoric acid, alcohol, water, kaolin, potassium silicate, and lignin to form phosphate, silicate, and silicon oxide insulating layers on the surface of iron-silicon powder.

3. The iron-silicon soft magnetic powder core with a permeability μ of 9 according to claim 1, characterized in that, In step 4), the release agent is microcrystalline wax or zinc stearate, and the amount of the release agent is 0.2-0.4% by weight of the iron-silicon powder; and the pressure for the press forming is 18-22 t / cm 2 .

4. The iron-silicon soft magnetic powder core with a permeability μ of 9 according to claim 1, characterized in that, In step 5), the nitrogen flow rate is 6m³ / h. 3 / h, sintering temperature is 700℃~780℃, holding time is 30~120min.

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