Preparation method of MnO-SiO2 insulating coated metal soft magnetic powder core

Abstract

The application is suitable for the field of metal soft magnetic powder core, and provides a preparation method of MnO-SiO2 insulating coated metal soft magnetic powder core, which comprises the following steps: adding a silane coupling agent into MnO2 powder, modifying the MnO2 powder to make it rich in hydroxyl groups; adding metal magnetic powder and ethanol into the obtained modified MnO2 mixed solution, stirring and drying to obtain MnO2 insulating coated metal magnetic powder; screening the obtained MnO2 insulating coated metal magnetic powder, performing screening and granulation, and pressing to form a green body; performing temperature rising annealing on the obtained green body to obtain a finished product of MnO-SiO2 insulating coated metal soft magnetic powder core. The MnO2 coating layer is converted into a MnO-SiO2 coating layer through high-temperature annealing, the MnO-SiO2 insulating coating layer generated by in-situ reaction of Si in the metal magnetic powder and MnO2 is more uniform and dense, the MnO-SiO2 coating layer is resistant to high temperature and is not easy to decompose and fall off, and the problem that the phosphoric acid passivation layer is easy to decompose at high temperature is effectively solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of metal soft magnetic powder cores, and particularly relates to a preparation method of a MnO-SiO2 insulating coated metal soft magnetic powder core. BACKGROUND

[0002] The metal soft magnetic powder core is widely applied to the fields of communication power supply, electric automobile, inverter, variable frequency air conditioner and the like as an important functional material in switching power supply due to high saturation magnetic induction intensity, good frequency stability, excellent DC bias performance and low eddy current loss.

[0003] The metal soft magnetic powder core is mainly prepared by insulating coating of metal magnetic powder to increase demagnetizing field between particles and reduce eddy current loss, improve saturation resistance and thus improve the application frequency range. Therefore, high resistivity, high temperature resistance and uniform insulating coating layer become the key to preparation of high performance metal soft magnetic powder core.

[0004] At present, the coating methods of the metal soft magnetic powder core mainly include organic coating and inorganic coating. The coating layer of the organic coating method is relatively uniform but has the defects of easy aging and poor high temperature resistance. The inorganic coating method can be divided into two categories of phosphoric acid passivation and oxide coating. The phosphoric acid passivation layer will decompose at about 600 DEG C, and has similar problems as the organic coating method. The oxide coating method has the advantages of high resistivity and high temperature resistance, and thus becomes the preferred coating method of the metal soft magnetic powder core. However, the oxide coating method still has the problems of uneven coating and easy peeling of the coating layer. SUMMARY

[0005] In view of the above problems, on the one hand, the application discloses a preparation method of a MnO-SiO2 insulating coated metal soft magnetic powder core, which comprises the following steps:

[0006] A mixed solution of silane coupling agent and H2O is added to the MnO2 powder, and the MnO2 powder is modified to be rich in hydroxyl groups;

[0007] Metal magnetic powder and ethanol are added to the obtained modified MnO2 mixed solution, and after stirring and drying, the MnO2 insulating coated metal magnetic powder is obtained.

[0008] The obtained MnO2 insulating coated metal magnetic powder is sieved and granulated, and is pressed into a green body.

[0009] The obtained green body is annealed at a high temperature to obtain a MnO-SiO2 insulating coated metal soft magnetic powder core finished product.

[0010] Further, after the silane coupling agent is added to the MnO2 powder, the silane coupling agent is ultrasonically dispersed.

[0011] Further, the silane coupling agent is KH550.

[0012] Further, when the silane coupling agent is added to the MnO2 powder, the mass ratio of the MnO2, the silane coupling agent and H2O is 1:(0.009-0.011):(0.4-0.6).

[0013] Further, the drying temperature is 120°C, and the drying is performed for 1h.

[0014] Further, the metal magnetic powder is any one of iron-silicon-aluminum powder and iron-silicon powder.

[0015] Further, when the metal magnetic powder and ethanol are added to the obtained modified MnO2 mixture, the component ratio between the components is as follows: the metal magnetic powder is 100 parts, the MnO2 mixture is 6-16 parts, and the ethanol is 2-5 parts.

[0016] Further, the screening and granulating and the pressing to form the green body specifically include:

[0017] The metal magnetic powder after the screening and granulating is weighed;

[0018] The resin binder and zinc stearate are added to the metal magnetic powder, and the mixture is uniformly mixed;

[0019] The green body is formed by pressing with an oil press.

[0020] Further, the mass ratio of the MnO2 insulation-coated metal magnetic powder, the resin binder and the zinc stearate is 100:(0.25-0.35):(0.35-0.45).

[0021] Further, the oil press is pressed in a bidirectional floating pressing mode.

[0022] Further, the pressure during the pressing is 1600-1900MPa, and the density of the green body is 5.5-7.0g / cm 3 .

[0023] The step of heating and annealing the obtained green body to obtain the MnO-SiO2 insulation-coated metal soft magnetic powder core finished product specifically includes:

[0024] The green body is placed in an annealing furnace, and the annealing furnace is heated from room temperature to 200°C at a heating rate of 5°C / min under nitrogen protection, and the annealing furnace is kept at 200°C for 1h;

[0025] Then, the annealing furnace is heated to 900°C at a heating rate of 5°C / min, and the annealing furnace is kept at 900°C for 3h;

[0026] Then, the annealing furnace is cooled to room temperature, and the MnO-SiO2 insulation-coated metal soft magnetic powder core finished product is obtained.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] (1) The present application converts the MnO2 coating layer into MnO-SiO2 coating layer through high-temperature annealing. The MnO-SiO2 coating insulation layer has higher resistivity than the MnO2 insulation layer, effectively improving the anti-saturation ability of the metal soft magnetic powder core, reducing the eddy current loss, improving the application frequency range, and meeting the trend of high frequency of magnetic elements.

[0029] (2) Compared with the traditional oxide coating method, the MnO-SiO2 coating insulation layer generated by in-situ reaction of Si in the metal magnetic powder and MnO2 is more uniform and dense. Compared with the phosphoric acid passivation method which also performs in-situ coating, the MnO-SiO2 coating layer is resistant to high temperature and is not easy to decompose and fall off, effectively solving the problem that the phosphoric acid passivation layer is easy to decompose at high temperature.

[0030] (3) In the preparation method of the present application, no organic coating agent is added, and the resin binder and zinc stearate are completely decomposed during high-temperature annealing, and the pressing internal stress is relieved, finally realizing a full inorganic insulation layer, effectively avoiding the aging problem of the organic insulation layer, and the MnO2 addition amount affects the thickness of the MnO-SiO2 coating layer, so the DC bias performance and loss of the soft magnetic powder core can be adjusted by controlling the MnO2 addition amount.

[0031] (4) The preparation method of the present application has low production cost and simple process flow.

[0032] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application. The objects and other advantages of the present application can be realized and obtained by the structure indicated in the specification, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0034] Figure 1 is a cross-sectional micro-morphology diagram of the iron-silicon-aluminum soft magnetic powder core prepared in Example 1;

[0035] Figure 2 is a cross-sectional micro-morphology diagram of the iron-silicon-aluminum soft magnetic powder core prepared in Example 2;

[0036] Figure 3is a cross-section micrograph of the iron-silicon soft magnetic powder core prepared in Example 3. DETAILED DESCRIPTION

[0037] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0038] Example 1

[0039] (1) 12 g of MnO2 was added into a mixture of 0.12 g of KH550 and 6 g of H2O, and mechanically stirred for 1 h to obtain a modified MnO2 mixture;

[0040] (2) 300 g of iron-silicon-aluminum magnetic powder and 6 g of ethanol were added into the mixture in step (1), and mechanically stirred for 1 h, and then dried at 120℃ for 1 h to obtain the MnO2 insulated coated iron-silicon-aluminum powder;

[0041] (3) The MnO2 insulated coated iron-silicon-aluminum powder obtained in step (2) was sieved through a 200 mesh sieve, and then 200 g of the sieved powder was weighed, 0.6 g of resin binder and 0.8 g of zinc stearate were added and mixed uniformly, and then a green body with a density of 5.73 g / cm3was prepared by two-way floating pressing with an oil press at a pressure of 1860 MPa; 3

[0042] (4) Annealing treatment: the green body obtained in step (3) was placed in an annealing furnace, and nitrogen was introduced to dry the air in the furnace, and then the furnace was heated at a rate of 5℃ / min from room temperature to 200℃ for 1 h, and then heated at a rate of 5℃ / min to 900℃ for 3 h, and then cooled to room temperature with the furnace, and the heat treatment process was annealed to prepare the finished iron-silicon-aluminum soft magnetic powder core.

[0043] The cross-section micrograph of the iron-silicon-aluminum soft magnetic powder core prepared in this example is shown in Figure 1 It can be seen that the internal structure of the powder core is dense, and the gap between the iron-silicon-aluminum magnetic powder is uniformly coated with insulating material.

[0044] The magnetic performance indexes of the iron-silicon-aluminum soft magnetic powder core prepared in this example after winding test are as follows:

[0045] (1) Under the conditions of test frequency 100 kHz and test voltage 1 V, the permeability μ = 28.58;

[0046] ​(2) DC bias performance: at a test frequency of 100 kHz and a DC bias magnetic field of 100 Oe, the magnetic permeability percentage %μ = 87.08%; at a test frequency of 100 kHz and a DC bias magnetic field of 200 Oe, the magnetic permeability percentage %μ = 66.03%;

[0047] (3) Loss: at a test frequency of 100 kHz and a test magnetic flux density of 500 Gs, the unit volume loss Pcv = 142.07 mW / cm 3 .

[0048] Example 2

[0049] (1) 24 g of MnO2 was added to a mixture of 0.24 g of KH550 and 12 g of H2O, and mechanically stirred for 1 h to obtain a modified MnO2 mixture;

[0050] (2) 300 g of iron-silicon-aluminum magnetic powder and 12 g of ethanol were added to the mixture in step (1), and mechanically stirred for 1 h, and then dried at 120°C for 1 h to obtain MnO2-insulated coated iron-silicon-aluminum powder;

[0051] (3) The MnO2-insulated coated iron-silicon-aluminum powder obtained in step (2) was sieved through a 200 mesh screen to form granules, then 200 g of the granulated powder was weighed, 0.6 g of resin binder and 0.8 g of zinc stearate were added and mixed uniformly, and then a double floating press was used at a pressure of 1860 MPa to form a green body with a density of 5.58 g / cm 3 ;

[0052] (4) Annealing treatment: the green body obtained in step (3) was placed in an annealing furnace and nitrogen was introduced to remove the air in the furnace, and then the heat treatment process of heating from room temperature to 200°C at a rate of 5°C / min, holding for 1 h, then heating to 900°C at a rate of 5°C / min, holding for 3 h, and then cooling to room temperature with the furnace, was used for annealing treatment to obtain an iron-silicon-aluminum soft magnetic powder core product.

[0053] The cross-sectional micro-morphology of the iron-silicon-aluminum soft magnetic powder core prepared in this example is shown in Figure 1 . It can be seen that the internal structure of the powder core is dense, and the gap between the iron-silicon-aluminum magnetic powder is uniformly coated with insulating material.

[0054] The magnetic performance indicators of the iron-silicon-aluminum soft magnetic powder core prepared in this example after winding test are as follows:

[0055] (1) At a test frequency of 100 kHz and a test voltage of 1 V, the magnetic permeability μ = 22.04;

[0056] (2) DC bias performance: at a test frequency of 100 kHz and a DC bias magnetic field of 100 Oe, the magnetic permeability percentage % μ = 90.1%; at a test frequency of 100 kHz and a DC bias magnetic field of 200 Oe, the magnetic permeability percentage % μ = 73.08%;

[0057] (3) Loss: at a test frequency of 100 kHz and a test magnetic flux density of 500 Gs, the unit volume loss Pcv = 251.04 mW / cm 3 .

[0058] Example 3

[0059] (1) 30 g of MnO2 was added to a mixture of 0.3 g of KH550 and 15 g of H2O, and mechanically stirred for 1 h to obtain a modified MnO2 mixture;

[0060] (2) 300 g of iron-silicon magnetic powder and 15 g of ethanol were added to the mixture in step (1), and mechanically stirred for 1 h, and then dried at 120℃ for 1 h to obtain an iron-silicon powder coated with MnO2 insulation;

[0061] (3) The MnO2-insulated iron-silicon aluminum powder obtained in step (2) was sieved through a 200 mesh screen to form granules, then 200 g of the granulated powder was weighed, 0.6 g of a resin binder and 0.8 g of zinc stearate were added and mixed uniformly, and then a double floating press was used at a pressure of 1860 MPa to form a green body with a density of 6.08 g / cm 3 ;

[0062] (4) Annealing treatment: the green body obtained in step (3) was placed in an annealing furnace and nitrogen was introduced to remove the air in the furnace. Under the protection of nitrogen, the furnace was heated from room temperature to 200℃ at a rate of 5℃ / min and held for 1 h, then heated to 900℃ at a rate of 5℃ / min and held for 3 h, and then cooled to room temperature with the furnace. Heat treatment process to perform annealing treatment to produce iron-silicon soft magnetic powder core finished product.

[0063] The cross-sectional micro-morphology of the iron-silicon soft magnetic powder core prepared in this example is shown in Figure 1 . It can be seen that the internal structure of the powder core is dense, and the gap between the iron-silicon magnetic powder is uniformly coated with insulating material.

[0064] The magnetic performance indicators of the iron-silicon soft magnetic powder core prepared in this example after winding test are as follows:

[0065] (1) At a test frequency of 100 kHz and a test voltage of 1 V, the magnetic permeability μ = 19.07;

[0066] (2) DC bias performance: at a test frequency of 100 kHz and a DC bias magnetic field of 100 Oe, the magnetic permeability percentage % mu = 92.2%; at a test frequency of 100 kHz and a DC bias magnetic field of 200 Oe, the magnetic permeability percentage % mu = 83.69%;

[0067] (3) Loss: at a test frequency of 100 kHz and a test magnetic flux density of 500 Gs, the unit volume loss Pcv = 511.84 mW / cm 3 .

[0068] The MnO-SiO2 insulating coated metal soft magnetic powder core obtained by the above preparation method has the following advantages:

[0069] (1) The MnO2 coating layer is converted into a MnO-SiO2 coating layer by high-temperature annealing in the present application, and the MnO-SiO2 insulating layer has a higher resistivity than the MnO2 insulating layer, effectively improving the anti-saturation ability of the metal soft magnetic powder core, reducing its eddy current loss, improving its application frequency range, and meeting the trend of high frequency of magnetic components.

[0070] (2) Compared with the traditional oxide coating method, the MnO-SiO2 insulating layer generated by in-situ reaction of Si in the metal magnetic powder and MnO2 is more uniform and dense; and compared with the phosphoric acid passivation method which also performs in-situ coating, the MnO-SiO2 insulating layer is resistant to high temperature and is not easy to decompose and fall off, effectively solving the problem that the phosphoric acid passivation layer is easy to decompose at high temperature.

[0071] (3) In the preparation method of the present application, no organic coating agent is added, and the resin binder and zinc stearate are completely decomposed during high-temperature annealing, and the pressing internal stress is relieved, finally realizing a full inorganic insulating layer, effectively avoiding the aging problem of the organic insulating layer, and the MnO2 addition amount affects the thickness of the MnO-SiO2 coating layer, so the DC bias performance and loss of the soft magnetic powder core can be adjusted by controlling the MnO2 addition amount.

[0072] (4) The preparation method of the present application has low production cost and simple process flow.

[0073] Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a MnO-SiO2 insulating coated metal soft magnetic powder core, characterized in that, The method includes the following steps: A mixture of silane coupling agent and H2O is added to MnO2 powder to modify the MnO2 powder and enrich it with hydroxyl groups; when the silane coupling agent is added to the MnO2 powder, the mass ratio of MnO2, silane coupling agent and H2O is 1:0.009~0.011:0.4~0.

6. Metal magnetic powder and ethanol were added to the obtained modified MnO2 mixture, stirred and dried to obtain MnO2 insulating coated metal magnetic powder. The obtained MnO2 insulating coated metal magnetic powder is sieved, granulated, and pressed to form a green body. The obtained green blank is heated and annealed to obtain the finished metal soft magnetic powder core with MnO-SiO2 insulation coating; The metal magnetic powder is any one of iron-silicon-aluminum powder or iron-silicon powder.

2. The method for preparing the MnO-SiO2 insulating coated metal soft magnetic powder core according to claim 1, Its features are, After adding the silane coupling agent to the MnO2 powder, the silane coupling agent is ultrasonically dispersed.

3. The method for preparing a MnO-SiO2 insulating coated metal soft magnetic powder core according to claim 1, characterized in that, The silane coupling agent is KH550.

4. The method for preparing the MnO-SiO2 insulating coated metal soft magnetic powder core according to claim 1, Its features are, The drying temperature is 120℃, and the drying is maintained at this temperature for 1 hour.

5. The method for preparing the MnO-SiO2 insulating coated metal soft magnetic powder core according to claim 1, Its features are, The process of screening, granulating, and pressing to form a green body specifically includes: Weigh the sieved and granulated metal magnetic powder; Add resin binder and zinc stearate to the metal magnetic powder and mix thoroughly; The blanks are made by pressing them with a hydraulic press.

6. The method for preparing the MnO-SiO2 insulating coated metal soft magnetic powder core according to claim 5, Its features are, The mass ratio of the MnO2 insulating coated metal magnetic powder to the resin binder and zinc stearate is 100:0.25~0.35:0.35~0.

45.

7. The method for preparing a MnO-SiO2 insulating coated metal soft magnetic powder core according to claim 6, characterized in that, The hydraulic press uses a bidirectional floating pressing method for pressing.

8. The method for preparing a MnO-SiO2 insulating coated metal soft magnetic powder core according to claim 6, characterized in that, The pressing pressure is 1600-1900 MPa, and the green body density is 5.5-7.0 g / cm³. 3 .

9. The method for preparing a MnO-SiO2 insulating coated metal soft magnetic powder core according to any one of claims 1-8, characterized in that, The step of annealing the obtained green blank to obtain the finished metal soft magnetic powder core with MnO-SiO2 insulation coating specifically includes: The green blanks were placed in an annealing furnace, and the furnace was heated from room temperature to 200°C at a rate of 5°C / min under nitrogen protection, and held at that temperature for 1 hour. Then, the temperature was increased to 900℃ at a rate of 5℃ / min and held for 3 hours. The core is then cooled to room temperature in the furnace to obtain a finished product of MnO-SiO2 insulating coating metal soft magnetic powder core.

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