KR20190116267A - Soft magnetic flat powder - Google Patents

Abstract

An object of the present invention is to provide a soft magnetic flat powder capable of preventing oxidation during the flattening processing of metal powder and realizing a low coercive force. In order to achieve this object, a plurality of soft magnetic flat particles are included. A soft magnetic flat powder comprising: each of the plurality of soft magnetic flat particles has a mass% of Fe: 78% or more and 83% or less, Si: 13% or less (0 is not included), Al: 5.0% or more and 13% or less A soft magnetic flat powder comprising at least one of Cr, Ni, Mo, Cu, and Ti: 1.0% or more and 5.0% or less in total, and the balance being alloy particles composed of Fe and unavoidable impurities.

Description

Soft magnetic flat powder

This application claims the priority according to Japanese Patent Application No. 2017-19328 for which it applied on February 6, 2017, The whole content of this indication is integrated in this specification by reference.

The present invention relates to a soft magnetic flat powder, for example, a soft magnetic flat powder for electromagnetic wave absorbers used in various electronic devices.

In recent years, with the rapid development of electronic devices and information devices such as personal computers and smart phones, the speed of information transmission is increasing. As a result, malfunctions due to electromagnetic waves have become a problem inside the electronic equipment. In addition, the influence of electromagnetic waves emitted by these electronic devices on the human body is also problematic. As the electromagnetic wave absorber of these electronic devices, soft magnetic ferrite or soft magnetic flat powder is used.

In particular, the soft magnetic flat powder does not need to be sintered and solidified like soft magnetic ferrite, but is mixed with a resin or the like and is molded, so that it is flexible and has a high degree of freedom in mounting, and thus is widely used mainly in small electronic devices. .

The said soft magnetic flat powder is produced by the method of flattening a metal powder using the attritor apparatus. In this method, an organic solvent called toluene, a metal powder, and a grinding medium (steel ball) are charged into an attritor device, and pulverized and flattened by a rotary blade inside the device. In such a method, a soft material such as a Fe-Si-Al alloy of a soft magnetic alloy is mainly used.

For example, Japanese Unexamined Patent Publication No. 2014-204051 (Patent Document 1) discloses a Fe-Si-Al alloy produced by using the above-described method. In Patent Literature 1, Fe is 84% to 96%, has a high concentration, and the elements of Ti, V, Cr, Mn, Co, Ni, and Cu are substituted for Fe.

In addition, Japanese Laid-Open Patent Publication No. 2008-50644 (Patent Document 2) is conventionally made by adding Si: 9.0% to 12%, Al: 1.0% to 5.0%, and Cr: 1.0% to 5.0% with respect to Fe. It is high resistivity not to be found and realizes low magnetic force.

Japanese Patent Application Publication No. 2014-204051 Japanese Laid-Open Patent Publication No. 2008-50644

As described above, the soft magnetic flat powder is produced by mixing and pulverizing the metal powder and the grinding medium in water or an organic solvent by dry or wet processing. In that case, since it processes for a long time in water or an organic solvent, a metal powder tends to oxidize and deteriorate a magnetic characteristic. Therefore, it is desired to prevent oxidation of the metal powder and to flatten it.

However, although Patent Literature 1 mentioned above describes the variation in composition due to oxidation at the time of flat processing and heat treatment, no clear measures are taken, and the intention of the component review is as far as the magnetic properties are concerned. It is only. In addition, Fe is high in the range of 84% to 96%, and there is no mention of oxidation resistance and corrosion resistance, but it is estimated that these characteristics are low.

In addition, although Patent Document 2 describes that the corrosion resistance is improved by containing Al and Cr, it is a low value of 5.0% or less for Al. In addition, deterioration of the magnetic properties due to oxidation occurring during flattening processing is not considered.

With respect to the problems not considered in Patent Documents 1 and 2 described above, the present inventors have conducted intensive development, and as a result, the amount of Al added is increased, and elements other than Fe, Si, and Al are intentionally By further adding, the inventors have found that the oxidation resistance and the corrosion resistance can be improved and that high magnetic properties can be obtained, and the present invention has been completed.

That is, the present invention includes the following soft magnetic flat powder and magnetic sheet.

[1] A soft magnetic flat powder comprising a plurality of soft magnetic flat particles, wherein each of the plurality of soft magnetic flat particles has a mass% of Fe: 78% or more and 83% or less and Si: 13% or less (0 is included) Al: not less than 5.0% and not more than 13% and at least one of Cr, Ni, Mo, Cu, and Ti: 1.0% or more and 5.0% or less in total, and the balance is alloy particles composed of Fe and unavoidable impurities, Soft magnetic flat powder.

[2] The coercive force measured by applying a magnetic field in the longitudinal direction of the soft magnetic flat particles is 230 A / m or less, and the saturation magnetic flux density of the soft magnetic flat powder is 0.6T or more and 1.5T or less. The soft magnetic flat powder of 1].

[3] A magnetic sheet containing the soft magnetic flat powder according to the above [1] or [2].

According to the present invention, there is provided a soft magnetic flat powder capable of preventing oxidation during the flattening of metal powder and realizing a low coercive force.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

<Composition of Soft Magnetic Flat Powder>

The soft magnetic flat powder of the present invention is an aggregate of a plurality of soft magnetic flat particles, and each soft magnetic flat particle has a mass% of Fe: 78% or more and 83% or less and Si: 13% or less (0 is not included). , Al: more than 5.0% and 13% or less, and at least one kind of Cr, Ni, Mo, Cu, and Ti: 1.0% or more and 5.0% or less in total, and remainder is an alloy particle composed of Fe and inevitable impurities. The reason for limiting the composition as described above is explained below.

[Fe: 78% or more and 83% or less]

Fe is an essential element for giving a soft magnetic flat powder a ferromagnetic property, and giving a soft magnetic flat powder high saturation magnetic flux density. When the content of Fe exceeds 83%, the oxidation resistance and corrosion resistance of the soft magnetic flat powder decrease. On the other hand, when the Fe content is less than 78%, the saturation magnetic flux density of the soft magnetic flat powder is greatly reduced. Therefore, content of Fe is 78% or more and 83% or less. The content of Fe is preferably 79% or more and 82% or less, and more preferably 79% or more and 81% or less.

[Si: 13% or less (not including 0)]

Si is an essential element for reducing the crystal magnetic anisotropy constant of the soft magnetic flat powder and reducing the coercive force of the soft magnetic flat powder. When the addition amount of Si decreases, the crystal magnetic anisotropy constant and coercive force of the soft magnetic flat powder tend to increase. When the Si content exceeds 13%, the saturation magnetic flux density of the soft magnetic flat powder is greatly reduced. Therefore, content of Si is more than 0% and 13% or less. The content of Si is preferably 3.0% or more and 10% or less, and more preferably 5.0% or more and 9.5% or less.

[Al: more than 5.0% and less than 13%]

Al is an essential element for reducing the crystalline magnetic anisotropy constant and coercive force of the soft magnetic flat powder and improving the oxidation resistance and corrosion resistance of the soft magnetic flat powder. If the amount of Al added is 5.0% or less, the corrosion resistance of the soft magnetic flat powder decreases, and the crystal magnetic anisotropy constant and the coercive force of the soft magnetic flat powder tend to increase. When the content of Al exceeds 13%, the saturation magnetic flux density of the soft magnetic flat powder is greatly reduced. Therefore, content of Al is more than 5.0% and 13% or less. The content of Al is preferably more than 5.0% and 10% or less, and more preferably 6.0% or more and 9.0% or less.

[At least one of Cr, Ni, Mo, Cu, Ti: 1.0% or more and 5.0% or less in total]

At least one of Cr, Ni, Mo, Cu, and Ti is an essential element for improving the oxidation resistance and corrosion resistance of the soft magnetic flat powder. And, "total 1.0% or more and 5.0% or less" means that when the soft magnetic flat particles contain one of Cr, Ni, Mo, Cu, and Ti, the content of the one kind of elements is 1.0% or more and 5.0% or less. When the soft magnetic flat particles contain two or more of Cr, Ni, Mo, Cu, and Ti, the total content of the two or more elements is 1.0% or more and 5.0% or less. When the total content of at least one of Cr, Ni, Mo, Cu, and Ti is less than 1.0%, the oxidation resistance and the corrosion resistance of the soft magnetic flat powder are not improved, and when the total content is more than 5.0%, the effects of precipitates, etc. As a result, the coercive force of the soft magnetic flat powder may be greatly increased. Therefore, the total content of at least one of Cr, Ni, Mo, Cu, and Ti is 1.0% or more and 5.0% or less. The total content of at least one of Cr, Ni, Mo, Cu, and Ti is preferably 1.5% or more and 4.5% or less, and more preferably 2.0% or more and 4.0% or less.

Magnetic Properties of Soft Magnetic Flat Powders

[Report power]

In the soft magnetic flat powder of the present invention, the coercive force measured by applying a magnetic field (143.6 kA / m) in the longitudinal direction of the soft magnetic flat particles is preferably 230 A / m or less. The frequency band in which the magnetic sheet comprising the soft magnetic flat powder of the present invention is used is preferably 1 to 15 MHz, and the coercive force is 230 A / m or less in order to obtain a high permeability in the frequency band. desirable. The coercive force is more preferably 190 A / m or less, and still more preferably 120 A / m or less. The lower limit of the coercive force is not particularly limited, but is 200 A / m, for example. The coercive force is calculated based on the value when the soft magnetic flat powder is filled into the resin container and magnetized in the radial direction of the container. Since the longitudinal direction and the thickness direction of the soft magnetic flat particles filled in the container correspond to the radial direction and the height direction of the container, respectively, the value when magnetized in the radial direction of the container becomes the coercive force in the longitudinal direction, and the height direction of the container. The value in the case of magnetizing becomes coercive force in the thickness direction.

[Saturated Magnetic Flux Density]

The saturation magnetic flux density of the soft magnetic flat powder of the present invention is preferably 0.6T or more and 1.5T or less, more preferably 0.8T or more and 1.5T or less. The saturation magnetic flux density is measured by an applied magnetic field of 1.2 × 10 ³ kA / m using a vibration sample magnetometer (VSM).

<Method for producing soft magnetic flat powder>

The manufacturing method of the soft magnetic flat powder of this invention is possible by the method currently proposed. The alloy powder which becomes a raw material is produced by various atomization methods, and this is flattened dry or wet by a ball mill or an attritor. After that, it is possible to reduce the coercive force by heat treatment at 500 ° C or higher. The manufacturing method of the soft magnetic flat powder of this invention is as follows specifically ,.

<Method for producing soft magnetic flat powder>

The soft magnetic flat powder of the present invention can be produced by a method including a raw material powder preparation step, a flat processing step, and a heat treatment step.

[Raw powder preparation process]

As the raw material powder, a soft magnetic alloy powder is used. The soft magnetic alloy powder used as the raw material powder is an aggregate of a plurality of soft magnetic alloy particles, and each of the soft magnetic alloy particles has a mass% of Fe: 78% or more and 83% or less and Si: 13% or less (0 is included) Al): more than 5.0%, 13% or less, at least one of Cr, Ni, Mo, Cu, Ti: 1.0% or more and 5.0% or less in total, and remainder is an alloy particle which consists of Fe and an unavoidable impurity. The reason for limiting the composition and the preferred content of each element are as described above.

The raw material powder can be produced by, for example, various atomization methods such as a gas atomization method, a water atomization method, a disk atomization method, or a pulverization method performed after alloying by melting. Since the amount of oxygen contained in the raw material powder is preferably smaller, the raw material powder is preferably produced by the gas atomizing method, more preferably by the gas atomizing method using an inert gas. Since the powder produced by the atomizing method is close to a spherical shape, flattening is more likely to proceed than the powder produced by the pulverization method using attrition or the like. Since the powder produced by the grinding method has a smaller particle size than the atomized powder, there is a tendency that projections on the surface of the magnetic sheet are suppressed.

Although the particle size of the raw material powder is not particularly limited, the particle size of the raw material powder may be adjusted to a desired range by classification according to the purpose of adjusting the average particle diameter after flattening, the purpose of removing the powder containing a large amount of oxygen, and other manufacturing purposes. .

[Flat processing process]

After the raw material powder preparation step, the raw material powder is flattened. Thereby, flat powder is obtained. The flat process method is not specifically limited, The flat process of a raw material powder can be performed using an atliter, a ball mill, a vibration mill, etc., for example. Especially, it is preferable to use the attritor which is comparatively excellent in flat processing capability. In the case of performing flat processing in a dry manner, it is preferable to use an inert gas. In the case of performing the flat processing in a wet manner, it is preferable to use an organic solvent.

The kind of organic solvent used in wet flat processing is not specifically limited. The addition amount of the organic solvent is preferably 100 parts by mass or more, and more preferably 200 parts by mass or more with respect to 100 parts by mass of the raw material powder. The upper limit of the addition amount of an organic solvent is not specifically limited, It can adjust suitably according to the balance of the magnitude | size and shape of desired flat powder, and productivity. The organic solvent may be a hydrous organic solvent, but in order to lower the oxygen content, the water concentration in the organic solvent is preferably 0.002 parts by mass or less with respect to 100 parts by mass of the organic solvent. Although the flattening aid may be used together with the organic solvent, in order to suppress oxidation, the addition amount of the flattening aid is preferably 5 parts by mass or less with respect to 100 parts by mass of the raw material powder.

[Heat treatment process]

After the flat processing step, the flat powder is heat treated. The heat treatment apparatus is not particularly limited as long as the desired heat treatment temperature can be realized. The heat treatment temperature is preferably 500 to 900 ° C, more preferably 600 to 850 ° C. By performing heat treatment at such a temperature, the coercive force can be reduced. The heat treatment time is not particularly limited and can be appropriately adjusted according to the throughput, productivity, and the like. However, when the heat treatment time becomes longer, the productivity decreases, so the heat treatment time is preferably within 8 hours.

In the heat treatment step, when the heat treatment atmosphere is air, oxidation of the flat powder proceeds. Therefore, in order to suppress oxidation of the flat powder, it is preferable to heat-treat the flat powder in vacuum or in an inert gas (for example, argon and nitrogen).

From the viewpoint of increasing the insulation property of the magnetic sheet including the soft magnetic flat powder, the use of the surface-treated soft magnetic flat powder may be suitable, and in the method for producing the soft magnetic flat powder, during the heat treatment step or Before and after the heat treatment step, the surface treatment step may be performed as necessary. For example, for surface treatment, heat treatment may be performed under an atmosphere containing a small amount of active gas. Moreover, it is also possible to improve corrosion resistance, dispersibility to rubber | gum, etc. by surface treatment represented by the cyanide coupling agent conventionally proposed.

<Magnetic sheet>

The magnetic sheet of the present invention contains the soft magnetic flat powder of the present invention. The magnetic sheet of the present invention has, for example, a structure in which the soft magnetic flat powder of the present invention is dispersed in matrix materials such as rubber, elastomer, and resin. The matrix material can be appropriately selected, one matrix material may be used, or two or more matrix materials may be used.

The amount of the soft magnetic flat powder contained in the magnetic sheet can be appropriately adjusted in consideration of required permeability characteristics and the like. The amount of the soft magnetic flat powder (volume filling rate of the soft magnetic flat powder in the magnetic sheet) contained in the magnetic sheet is preferably 20 to 60% by volume, for example, 20 to 40% by volume or 40 to 60% by volume. .

The manufacture of the magnetic sheet which consists of soft magnetic flat powder can be performed according to the method currently proposed using soft magnetic flat powder. For example, a soft magnetic flat powder is mixed with toluene dissolved in chlorinated polyethylene, applied to a base material made of synthetic resin such as polyester resin, and the dried product is compressed by various presses or rolls. It can manufacture by doing.

EXAMPLE

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated concretely based on an Example.

[Production of Flat Powder]

The alloy powder of the composition shown in Table 1 and Table 2 was produced by the gas atomization method, it classified into 150 micrometers or less, and used as raw material powder. The gas atomization method was performed by using an alumina crucible for melting, tapping an alloy molten metal from a nozzle having a diameter of 5 mm under the crucible, and spraying it with high pressure argon.

Subsequently, the raw material powder was flattened by the attritor device. The attritor put a 4.8 mm diameter ball made of SUJ2 into the stirring vessel together with the raw material powder and industrial ethanol, and carried out at 350 rpm of the blade.

The obtained flat powder was heat-treated in Ar atmosphere in order to remove the distortion introduced during flat processing. The temperature of the heat treatment was 500 to 900 ° C in consideration of the sintering temperature of the powder, and the time of the heat treatment was 3 hours.

[Evaluation of Flat Powder]

The coercive force (Hc) and saturation magnetic flux density (Bs) of the flat powder to which the heat treatment was applied were measured. The coercive force was measured by applying a magnetic field (143.6 kA / m) in the longitudinal direction of the flat particles using COERCIMETER HC801 manufactured by Qumano. Specifically, the flat powder was filled into a resin container having a diameter of 6 mm and a height of 8 mm, and calculated on the basis of the value when magnetized in the radial direction of the container. Since the longitudinal direction and the thickness direction of the flat particles filled in the container correspond to the radial direction and the height direction of the container, respectively, the value in the case of magnetizing in the radial direction of the container becomes the coercive force in the longitudinal direction, and magnetizes in the height direction of the container. The value in one case is the coercive force in the thickness direction. The saturation magnetic flux density was measured at an applied magnetic field of 1.2 × 10 ³ kA / m using a vibration sample magnetometer (VSM).

In addition, the corrosion resistance of the flat powder was evaluated. About corrosion resistance, the flat powder was immersed in 20 degreeC salt solution of 25 degreeC for 100 hours, and the rust state after immersion was evaluated based on the following references | standards.

A: No call

B: Low call out

C: The state of call out is moderate

D: The condition is high

TABLE 1

TABLE 2

Note 1) Underline is other than the conditions of the present invention.

In Table 1 and Table 2, No.1-31 is an example of this invention, No.32-43 is a comparative example.

Comparative Example No. 32 has a high coercive force and a low saturation magnetic flux density because the total amount (Cr content) of elements other than Fe, Si, and Al is high. Comparative Example No. 33 has a low Fe content and a high coercive force because the total amount (Ni content) of elements other than Fe, Si, and Al is high. In Comparative Example No. 34, since the total amount (Mo content) of elements other than Fe, Si, and Al is high, the coercive force is high and the corrosion resistance is inferior. In Comparative Example No. 35, the total amount (Cu content) of elements other than Fe, Si, and Al is high, so the coercive force is high, and the corrosion resistance is poor. Comparative Example No. 36 has a low Fe content and a high total amount (Ti content) of elements other than Fe, Si, and Al, and therefore has high coercive force, low saturation magnetic flux density, and poor corrosion resistance.

In Comparative Examples Nos. 37 to 39, the Fe content was low and the total amount of elements other than Fe, Si, and Al was high. Therefore, the coercive force was high and the corrosion resistance was somewhat inferior. Comparative Example No. 40 has a high coercive force and a poor corrosion resistance because the total amount of elements other than Fe, Si, and Al is high. Comparative Example No. 41 has a high Si content and a low Al content, so that the coercive force is high, the saturation magnetic flux density is low, and the corrosion resistance is poor. Comparative Example No. 42 has a high Al content, and therefore has high coercive force and low saturation magnetic flux density. Since Comparative Example No. 43 has a low Al content, the coercive force is high and the corrosion resistance is poor.

On the other hand, since all the invention examples No.1-31 satisfy | fill the conditions of this invention, it turns out that the characteristic of the coercivity, the saturation magnetic flux density, and corrosion resistance measured by applying the magnetic field in the longitudinal direction is excellent.

As mentioned above, this invention can prevent deterioration of the magnetic property by oxidation at the time of flat processing by raising content of alloying elements other than Fe, compared with the former, and flat powder can simultaneously implement low coercive force and high corrosion resistance. It provides a soft magnetic flat powder that can be.

Claims (3)

As a soft magnetic flat powder comprising a plurality of soft magnetic flat particles,
Each of the plurality of soft magnetic flat particles has a mass% of Fe: 78% or more and 83% or less, Si: 13% or less (0 is not included), Al: 5.0% or more and 13% or less, Cr, Ni, Mo, At least one of Cu and Ti: 1.0% or more and 5.0% or less in total, and remainder is alloy particle which consists of Fe and an unavoidable impurity,
Soft magnetic flat powder. The method of claim 1,
A soft magnetic flat powder having a coercive force of 230 A / m or less measured by applying a magnetic field in the longitudinal direction of the soft magnetic flat particles, and a saturated magnetic flux density of the soft magnetic flat powder of 0.6T or more and 1.5T or less. The magnetic sheet containing the soft magnetic flat powder of Claim 1 or 2.