JP2004079943A - Silicon-ferrous alloy based metal soft magnetic dust core - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicon-ferrous alloy based metal soft magnetic dust core for electronic components featuring high permeability, high saturation magnetization, a small loss, stability in DC superposition characteristics, and the like, and to provide its producing process. <P>SOLUTION: The silicon-ferrous alloy based metal soft magnetic dust core is produced by spraying surface coating liquid mixing an inorganic insulation layer forming liquid and rustproofing liquid under such a state as silicon-iron powder having particle size not larger than 75 μm and containing silicon by 0.5-7 wt% is floating while stirred by hot air, heat treating the silicon-iron powder subjected to surface coating at an appropriate temperature in order to form an insulation layer, compressing powder thus produced with an appropriate pressure to produce a dust core, and then treating it at an appropriate temperature in the atmosphere thereby generating appropriate subgrains. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Field of the Invention]
The present invention relates to a silicon-iron alloy-based metal soft magnetic powder magnetic core, and particularly for a circuit used in various electronic devices, for a noise filter circuit element and an electronic component of various choke coils which are expanding to an increasingly higher frequency range. The present invention relates to a silicon-iron alloy-based metal soft magnetic powder core as a material and a method for producing the same.
[0002]
[Prior art]
In conventional iron-based soft magnetic powder magnetic cores, an attempt to improve the magnetic properties of the magnetic core has focused mainly on the purity of the iron powder.
Also, in the production method of raw materials, the particle diameter of iron powder has been studied, such as spherical, plate-like, etc., but in each case, each particle is a cluster-like mass of several to several tens of primary particles, and the diameter is Particles of several tens μm are formed.
On the other hand, in the firing process after powder molding, normal recrystallization was performed, and for example, the recrystallization process found in JIS G 0552 (test method for ferrite crystal grain size of steel) was performed.
In this method, there is a limit in improving characteristics.
As a remedy, Japanese Patent Application No. 2001-321701 of the present applicant proposes a method of greatly improving the characteristics, but further improvement is required in terms of increasing the initial magnetic permeability and the high-frequency loss. Was.
Therefore, the present invention solves the above-mentioned problem by using a silicon-iron alloy to which silicon (Si) is added as an iron-based metal as a raw material.
[0003]
[Problems to be solved by the invention]
The present invention provides a silicon-iron alloy-based metal soft magnetic powder core having characteristics such as magnetic properties, that is, high magnetic permeability, high saturation magnetization, low loss, and stability of DC superimposition characteristics in a powder core for electronic components. An object is to provide a manufacturing method.
[0004]
[Means for Solving the Problems]
The present invention has found that primary grains containing strain exist in the crystal of each grain, and by selecting processing conditions for releasing the strain, a sub-grain of 150 to 700 nm width is formed in the grains. It has been found that the magnetic properties can be improved by preparing a.
In the silicon-iron powder used as the raw material, if the particle size exceeds 75 μm, the high-frequency characteristics are poor and cannot be controlled. Therefore, a particle size of 75 μm or less is appropriate.
Even if the shape of the sub-grain is spherical, there is some effect, but if the aspect ratio (aspect ratio) is 3 or more, the effect of improving the magnetic properties is greater.
Further, in this production method, silicon-iron powder particles having a particle diameter of 75 μm or less and a silicon content of 0.5 to 7% by weight are uniformly coated with a surface coating liquid comprising an insulating layer forming treatment liquid and a rust prevention treatment liquid. Is subjected to heat treatment in the atmosphere after compression-molding the surface-coated silicon-iron powder.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
The silicon-iron alloy soft magnetic powder core of the present invention is manufactured as follows.
Surface coating obtained by mixing an inorganic insulating layer forming treatment liquid and a rust prevention treatment liquid while silicon-iron powder having a particle diameter of 75 μm or less and a silicon content of 0.5 to 7% by weight is suspended and stirred with warm air. Wiping the liquid, heat-treating the surface-coated silicon-iron powder at an appropriate temperature to form an insulating layer, and compressing the powder obtained in this step at an appropriate pressure to obtain a dust core. Process at the right temperature in the atmosphere to produce the right subgrain.
[0006]
【Example】
Specific examples of the present invention will be described in detail below.
In a state where 3 kg of silicon-iron powder having an average particle diameter of 75 μm or less and having a silicon content of 0.5 to 7% by weight was suspended and stirred with warm air, 30 g of an insulating layer forming treatment liquid (3.4 g of phosphoric acid, 0 g of boric acid) 2.6 g, magnesium oxide 0.6 g, water 25.4 g), and a surface coating solution obtained by mixing 188 g of rust preventive solution (3.3 g of 1,2,3-benzotriazole, 184.7 g of water) was sprayed, and silicon-iron was sprayed. The powder surface was coated, heat-treated at 150 ° C. for 1 hour, and dried to form an insulating layer on the silicon-iron powder surface layer.
Further, the silicon-iron powder having an insulating layer formed on the surface is granulated with 300 g of water glass (27 g of water glass and 273 g of water) in order to enhance moldability and strength, and has an outer diameter of 18 mm and an inner diameter of 9 mm at 10 ton / cm ^2. And compression molding into a toroidal shape having a height of 6 mm to form a dust core, and further subjecting the dust core to a heat treatment at 200 ° C. to 600 ° C. in the air to form a silicon-iron alloy-based metal soft magnetic dust core. Made.
[0007]
FIGS. 1 and 2 show the sub-grain state of the silicon-iron alloy-based metal soft magnetic powder core manufactured as described above.
FIG. 3 shows the relationship between the sub-grain size and the initial magnetic permeability, and FIG. 4 shows the relationship between the particle size and the frequency characteristics of the initial magnetic permeability.
FIG. 5 shows the relationship between the subgrain size and the high-frequency loss, and FIG. 6 shows the relationship between the silicon addition amount and the high-frequency loss.
Here, the sub-grain size refers to the size of the narrow width, not the longitudinal direction.
The state of the sub-grain was measured by Ar ion milling using a high-resolution transmission electron microscope (TEM) to measure a region where a part of the sintered powder was thinned.
The magnetic permeability was determined by calculating the inductance after measurement by winding a powder magnetic core to be measured.
The loss was measured with a BH analyzer by winding a powder magnetic core to be measured.
[0008]
FIGS. 1 and 2 show the results obtained by observing the silicon-iron alloy soft magnetic powder magnetic cores manufactured in the examples according to the difference in the sub-grain size by using a high-resolution transmission electron microscope (TEM). .
[0009]
FIG. 3 shows a change in initial magnetic permeability due to a difference in sub-grain size of a silicon-iron alloy-based metal soft magnetic powder magnetic core manufactured in the example.
From FIG. 3, based on the change rate of the initial magnetic permeability of 1.0, the value of the initial magnetic permeability when the sub-grain size is in the range of 150 to 700 nm is 15% on the average in the range of 150 nm to 250 nm, and the range of 250 nm to 700 nm. With this, the initial permeability is improved by an average of 40%.
When the sub-grain size is 150 nm or less, there is no improvement in the initial magnetic permeability. When the sub-grain size is 700 nm or more, the initial magnetic permeability significantly deteriorates from 150 nm to 700 nm.
[0010]
FIG. 4 shows a change in high-frequency loss due to a difference in the sub-grain size of the iron-based soft magnetic powder magnetic core manufactured in the example.
From FIG. 4, based on the change rate of the high-frequency loss of 1.0, the high-frequency loss when the sub-grain size is in the range of 150 to 700 nm is improved by 20% in the range of 150 to 250 nm and by 35% in the range of 250 to 700 nm. Become.
At 150 nm or less, there is no improvement in high-frequency loss, and at 700 nm or more, there is a significant deterioration.
[0011]
FIG. 5 shows a change in initial magnetic permeability due to a difference in aspect ratio (aspect ratio) of the dust core manufactured in the example.
From FIG. 5, the value of the initial magnetic permeability is improved by 17% or more when the aspect ratio (aspect ratio) is 3 or more based on the change rate of the initial magnetic permeability of 1.0. Few.
[0012]
FIG. 6 shows a change in the frequency characteristic of the initial magnetic permeability due to the difference in the particle size of the silicon-iron alloy-based metal soft magnetic powder magnetic core manufactured in the example.
Referring to FIG. 6, based on the change rate of the initial magnetic permeability of 1.0, the frequency characteristic of the initial magnetic permeability at a particle size of 75 μm or less can be greatly improved to about 5% decrease at 10 MHz. When the particle size is 106 μm or less, the reduction is 30% at 10 MHz, and when the particle size is 150 μm or less, the reduction is 40% at 10 MHz.
[0013]
FIG. 7 shows the change in the addition amount of silicon (Si) metal and the high frequency loss of the dust core manufactured in the example.
According to FIG. 7, the high-frequency loss is improved by 15% to 35% when the added amount of silicon (Si) is in the range of 0.5 to 7% based on the added amount of silicon (Si) of 0%. However, not only the remarkable improvement effect of the high-frequency loss is not found, but when it is 7% or more, the powder becomes hard as a metal powder and a high molding pressure is required when a powder molded body is produced, which is not industrially preferable.
[0014]
As described with reference to FIGS. 3 to 7 of the above embodiment, it has been clarified that the magnetic properties of the silicon-iron powder can be significantly improved by controlling the size and shape of the sub-grain.
[0015]
【The invention's effect】
The present invention provides a method for compressing silicon-iron alloy-based soft magnetic powder obtained by insulating grain boundaries of iron powder into a predetermined shape. In this case, the selection of the processing conditions for releasing the magnetic field, that is, the formation of a sub-grain having a width of 150 to 700 nm succeeded in obtaining a significant improvement in magnetic characteristics.
Further, the magnetic properties of the silicon-iron alloy-based metal soft magnetic powder core of the present invention have made it possible to greatly contribute to the use of parts as various electronic equipment materials.
[Brief description of the drawings]
FIG. 1 is a photograph of a subgrain by cross-sectional TEM observation at a subgrain size of 250 to 700 μm.
FIG. 2 is a photograph of a subgrain by cross-sectional TEM observation at a subgrain size of 150 to 250 μm.
FIG. 3 is a graph showing the relationship between the size of a sub-grain size and the initial magnetic permeability.
FIG. 4 is a graph showing the relationship between the size of a sub-grain size and high-frequency loss.
FIG. 5 is a graph showing a relationship between an aspect ratio and an initial magnetic permeability.
FIG. 6 is a graph showing the relationship between the size of the particle size and the frequency characteristic of the initial magnetic permeability.
FIG. 7 is a graph showing the relationship between the amount of added silicon (Si) and high-frequency loss.

Claims (3)

A silicon-iron alloy based metal soft magnetic powder having a particle size of 75 [mu] m or less, a silicon content of 0.5 to 7% by weight, and a subgrain having a width of 150 to 700 nm in the particle. core. The silicon-iron alloy-based soft magnetic powder magnetic core according to claim 1, wherein the aspect ratio of the subgrain is 3 or more. The surface of a silicon-iron alloy powder having a particle size of 75 μm or less and a silicon content of 0.5 to 7% by weight is uniformly coated with a surface coating solution comprising an insulating layer forming solution and a rust preventive solution. A method for producing a silicon-iron alloy-based metal soft magnetic powder magnetic core, which comprises subjecting a surface-coated silicon-iron powder to compression molding and heat-treating it in air.

Images