METHOD FOR COATING MAGNETIC POWDER CORE WITH SODIUM SILICATE

Abstract

The present disclosure discloses a method for coating a magnetic powder core with sodium silicate, including: using polyoxyethylene laurylether phosphate as a dispersant for sodium silicate and lignosulfonate as a dispersant for a metal magnetic powder, mixing a dispersed sodium silicate solution and a dispersed metal magnetic powder, coating the dispersed metal magnetic powder, and drying: adding an insulating adhesive and a lubricant, subjecting the resulting mixture to a compression molding, and finally, carrying out a high-temperature annealing treatment to obtain a sodium silicate coated magnetic powder core.

Claims

1-10 (canceled)

11. A method for coating a magnetic powder core with sodium silicate, comprising: step 1, pretreatment of sodium silicate: mixing sodium silicate and deioinzed water in a ratio of 1:(1-5), adding polyoxyethylene laurylether phosphate thereto, and mixing uniformly to obtain a sodium silicate solution, wherein the polyoxyethylene laurylether phosphate serves to uniformly disperse the sodium silicate in an aqueous solution, and could also simultaneously play a role of antirust to prevent the metal magnetic powder from rusting; step 2, pretreatment of a metal magnetic powder: adding the metal magnetic powder to a coating furnace, setting the coating furnace at a temperature of 60-80° C. adding lignosulfonate to the coating furnace after reaching the set temperature, and stirring for 10-30 minutes, wherein the lignosulfonate serves to uniformly disperse the metal magnetic powder; step 3, coating: adding the sodium silicate solution obtained in step 1 to the metal magnetic powder obtained in step 2, and stirring for 10-30 minutes, wherein the sodium silicate solution is added in an amount of 1-10 wt % of the metal magnetic powder; step 4, baking: baking the powder obtained in step 3 at a temperature of 120-150° C. for 60-120 minutes to obtain a coated powder; step 5, adding an insulating adhesive and a lubricant: adding an inorganic insulating adhesive in an amount of 0.1%-1% by weight of the coated powder and a stearate as a lubricant in an amount of 0.1%-1% by weight of the coated powder to the coated powder obtained in step 4, and mixing uniformly; step 6, compression molding: subjecting the magnetic powder mixed uniformly in step 5 to a compression molding at a molding pressure of 1500-2300 MPa; and step 7, heat treatment: keeping the magnetic powder core molded in step 6 under the protection of a N.sub.2 or H.sub.2 atmosphere at a temperature of 600-800° C. for 30-90 minutes to obtain a sodium silicate-coated magnetic powder core.

12. The method of claim 11, wherein in step 1, the polyoxyethylene laurylether phosphate is added in an amount of 0.1-3 wt % of the sodium silicate.

13. The method of claim 11, wherein in step 2, the lignosulfonate is added in an amount of 0.1-1 wt % of the metal magnetic powder.

14. The method of claim 11, wherein the metal magnetic powder is one or more selected from the group consisting of pure Fe, FeSi, FeSiAl, FeSiNi, FeNi, FeNiMo, and FeSiCr, and has an average particle size of 10 to 200 μm.

15. The method of claim 11, wherein the insulating adhesive added in step 5 is one or more selected from the group consisting of silicon dioxide, aluminum oxide, and calcium oxide, and has a particle size of 10 μm or less.

16. The method of claim 11, wherein the stearate in step 5 is one or more selected from the group consisting of zinc stearate, aluminum stearate, and lithium stearate.

17. The method of claim 11. wherein a shape formed by the compression molding in step 6 is one of annular, E-shaped, and U-shaped.

18. The method of claim 11, wherein in step 3, the amount of the sodium silicate solution added is replaced by 20 wt % of the metal magnetic powder.

19. The method of claim 11. wherein step 6 further comprises chamfering after the compression molding.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 shows a flow chart of a coating process according to an example of the present disclosure.

[0030] FIG. 2 is an SME image of the sodium silicate coated magnetic powder core according to the present disclosure after an annealing treatment.

[0031] FIG. 3 is an SME image of the magnetic particle core coated by a conventional process in which an organic adhesive and phosphoric acid are used after an annealing treatment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The present disclosure is further described below in combination with drawings and specific examples, but the protection scope of the present disclosure is not limited thereto.

Example 1

[0033] 10 g of sodium silicate and 10 g of deionized water were weighed and mixed uniformly and 0.01 g of polyoxyethylene laurylether phosphate was added thereto, and then mixed uniformly, obtaining a sodium silicate solution, in which the polyoxyethylene laurylether phosphate serves to uniformly disperse sodium silicate in an aqueous solution, and could also simultaneously play a role of antirust to prevent the metal magnetic powder from rusting. 1000 g of air-atomized sendust powder with an average particle size of 30 μm was weighed and placed into a coating furnace. The coating furnace was heated to 60° C., and then 1 g of lignosulfonate was added thereto and stirred for 20 minutes, wherein the lignosulfonate serves to uniformly disperse the metal magnetic powder. The sodium silicate solution was added to the metal magnetic powder and stirred for 10-30 minutes, obtaining a mixture. The coating furnace was then heated to 120 ° C., and the mixture was baked for 120 minutes, obtaining a coated powder: Then, aluminum oxide in an amount of 0.1% by weight of the coated powder and zinc stearate lubricant in an amount of 0.1% by weight of the coated powder were added to the coated powder, and they were mixed uniformly. The uniformly mixed magnetic powder was molded into a  27×φ14.7×11 annular magnetic powder core at a molding pressure of 1500 MPa, and chamfered. The magnetic powder core was kept at 600° C. under the protection of N.sub.2 atmosphere for 30 minutes, obtaining a sodium silicate coated magnetic powder core.

Example 2

[0034] 40 g of sodium silicate and 40 g of deionized water were weighed and mixed uniformly, and 1.2 g of polyoxyethylene laurylether phosphate was added thereto, and then mixed uniformly, obtaining a sodium silicate solution, in which the polyoxyethylene laurylether phosphate serves to uniformly disperse sodium silicate in an aqueous solution, and could also simultaneously play a role of antirust to prevent the metal magnetic powder from rusting. 1000 g of air-atomized sendust powder with an average particle size of 32 μm was weighed and placed into a coating furnace. The coating furnace was heated to 80° C., and 5 g of lignosulfonate was then added thereto and stirred for 30 minutes, wherein the lignosulfonate serves to uniformly disperse the metal magnetic powder. The sodium silicate solution was added to the metal magnetic powder and stirred for 30 minutes, obtaining a mixture. The coating furnace was then heated to 120° C., and the mixture was baked for 120 minutes, obtaining a coated. powder. Then, aluminum oxide in an amount of 0.5% by weight of the coated powder and zinc stearate lubricant in an amount of 0.8% by weight of the coated powder were added to the coated powder, and they were mixed uniformly. The uniformly mixed magnetic powder was molded into a φ27×φ14.7×11 annular magnetic powder core at a molding pressure of 2000 MPa, and chamfered. The magnetic powder core was kept at 700° C. under the protection of N.sub.2 atmosphere for 90 minutes, obtaining a sodium silicate coated magnetic powder core.

Comparative Example 1

[0035] An aerosolized FeSiAl ring magnetic powder core (φ27×φ14.7×11) prepared by a conventional coating process using an organic adhesive and phosphoric acid was used as a standard product with a permeability of 90.

Comparative Example 2

[0036] An aerosolized FeSiAl ring magnetic powder core (φ27×φ14.7×11) prepared by a conventional coating process using an organic adhesive and phosphoric acid was used as a standard product with a permeability of 75.

Performance Test

[0037] The annular magnetic powder cores obtained in Examples 1 to 2 and Comparative Examples 1 to 2 were subjected to winding test, using φ0.7 mm copper wire with 35 turns, in which the instrument for testing inductance was TH2816B, the instrument for testing loss was VR152, and the instrument for testing the DC bias performance was CHROMA3302+1320. The obtained results are shown in Table 1.

TABLE-US-00001 TABLE 1 Magnetic test results of Examples 1 to 2 and Comparative Examples 1 to 2 DC bias performance Inductance Core (Ratio of permeability (μH)/ losses under 100Oe DC bias 100 kHZ, Perme- (50 kHz/ magnetic field to 1 V, 25 Ts ability 100 mT) initial permeability) Example 1 71.95 92.1 242 29.5% Comparative 72.65 93.0 298 26.2% Example 1 Example 2 59.06 75.6 267 36.4% Comparative 59.61 76.3 321 34.1% Example 2

[0038] As can be seen from table 1, compared with the conventional coating process, the annular magnetic powder cores obtained in Examples 1 to 2 of the present disclosure have greatly reduced core losses, and improved DC bias performances by not less than 2%.

Example 3

[0039] 100 g of sodium silicate and 100 g of deionized water were weighed and mixed uniformly and 3 g of polyoxyethylene laurylether phosphate was added thereto, and then mixed uniformly, obtaining a sodium silicate solution, in which the polyoxyethylene laurylether phosphate serves to uniformly disperse sodium silicate in an aqueous solution, and could also simultaneously play a role of antirust to prevent the metal magnetic powder from rusting. 1000 g of air-atomized sendust powder with an average particle size of 35 μm was weighed and placed into a coating furnace. The coating furnace was heated to 80° C., and then 10 g of lignosulfonate was added thereto and stirred for 30 minutes, wherein the lignosulfonate serves to uniformly disperse the metal magnetic powder. The sodium silicate solution was added to the metal magnetic powder and stirred for 30 minutes, obtaining a mixture. The coating furnace was then heated to 150° C. and the mixture was baked for 60 minutes, obtaining a coated powder. Then, aluminum oxide in an amount of 1% by weight of the coated powder and zinc stearate lubricant in an amount of 1% by weight of the coated powder were added to the coated powder, and they are mixed uniformly. The uniformly mixed magnetic powder was molded into a φ27×φ14.7×11annular magnetic powder core at a molding pressure of 2300 MPa, and chamfered. The magnetic powder core was kept at 800° C. under the protection of N.sub.2 atmosphere for 90 minutes, obtaining a sodium silicate coated magnetic powder core.

Example 4

[0040] 50 g of sodium silicate and 50 g of deionized water were weighed and mixed uniformly, and 0.5 g of polyoxyethylene laurylether phosphate was added thereto, and then mixed uniformly, obtaining a sodium silicate solution, in which the polyoxyethylene laurylether phosphate serves to uniformly disperse sodium silicate in an aqueous solution, and could also simultaneously play an role of antirust to prevent the metal magnetic powder from rusting. 1000 g of air-atomized sendust powder with an average particle size of 38 μm was weighed and placed into a coating furnace. The coating furnace was heated to 70° C., and 10 g of lignosulfonate was added thereto and stirred for 30 minutes, wherein the lignosulfonate serves to uniformly disperse the metal magnetic powder. The sodium silicate solution was added to the metal magnetic powder and stirred for 30 minutes, obtaining a mixture. The coating furnace was then heated to 150° C., and the mixture was baked for 60 minutes, obtaining a coated powder. Then, aluminum oxide in an amount of 1% by weight of the coated powder and zinc stearate lubricant in an amount of 0.5 % by weight of the coated powder were added to the coated powder, and they were mixed uniformly. The uniformly mixed magnetic powder was molded into a φ27×φ14.7×11annular magnetic powder core at a molding pressure of 2000 MPa, and chamfered. The magnetic: powder core was kept at 700° C. under the protection of H.sub.2 atmosphere for 80 minutes, obtaining a sodium silicate coated magnetic powder core.

Comparative Example 3

[0041] An aerosolized FeSi ring magnetic powder core (φ27×φ14.7×11) prepared by a conventional coating process using an organic adhesive and phosphoric acid was used as a standard product with a permeability of 26.

Comparative Example 4

[0042] An aerosolized FeSi ring magnetic powder core (φ27×φ14.7×11) prepared by a conventional coating process using an organic adhesive and phosphoric acid was used as a standard product with a magnetic permeability of 60.

Performance Test

[0043] The annular magnetic powder cores obtained in Examples 3 to 4 and Comparative Examples 3 to 4 were subjected to winding test, using φ0.7 mm copper wire with 35 turns, in which the instrument for testing inductance was TH2816B, the instrument for testing loss was VR152, and the instrument for testing DC bias performance was CHROMO3302+1320. The obtained results are shown in Table 2.

TABLE-US-00002 TABLE 2 Magnetic test results of Examples 3 to 4 and Comparative Examples 3 to 4 DC bias performance Inductance Core (Ratio of permeability (μH)/ losses under 100Oe DC bias 100 kHZ, Perme- (50 kHz/ magnetic field to 1 V, 25 Ts ability 100 mT) initial permeability) Example 3 20.55 26.3 898 92.3% Comparative 20.7 26.5 1126 89.7% Example 3 Example 4 47.42 60.7 608 73.4% Comparative 47.58 60.9 723 70.2% Example 4

[0044] As can be seen from table 2, compared with the conventional coating process, the annular magnetic powder cores obtained in Examples 3 to 4 of the present disclosure have greatly reduced core losses, and improved DC bias performance by not less than 7%.

[0045] Although embodiments of the present disclosure have been shown and described, it should be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations may be made to the embodiments described herein without departing from the principle and spirit of the present disclosure, and the scope of the present disclosure is defined by the appended claims and equivalents thereof.