JP2523388B2 - Method for producing soft magnetic powder for magnetic shield and magnetic shield material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a method for producing soft magnetic powder, which is preferably used for a magnetic shield material, and a magnetic shield material containing the soft magnetic powder.

<Prior Art> A magnetic shield material is used to prevent a magnetic field generation source such as a magnetized object from affecting other objects or electric circuits. As a magnetic shield material, a metal plate having high magnetic permeability is desirable from the viewpoint of shielding characteristics, but the use of the metal plate is significantly limited in terms of properties and cost.

On the other hand, in the case of a powder material, it may be dispersed in an organic binder and applied in the form of paint to the necessary parts of the shield, or it may be applied to a suitable flexible support or the like to form a shield plate, Various uses are possible.

Various proposals have been made regarding magnetic shield materials using powder of high magnetic permeability.

For example, Japanese Patent Laid-Open No. 59-201493 discloses a magnetic shield coating prepared by mixing a flat powder obtained by crushing a soft magnetic amorphous alloy in a binder of a polymer compound, and Japanese Patent Laid-Open No. 58-59268 discloses a high magnetic permeability alloy. No. 58-50495 discloses a magnetic shield coating prepared by mixing a flat powder of No. 1 in a binder of a polymer compound, and a flake-like Sendust alloy coating is used as a magnetic shield film. No. 58631 discloses Fe-Ni alloy, Fe-Ni
-Co alloy, Fe-Si-Al alloy, Fe-Ni-Mo alloy, that is, permalloy alloy or molybdenum permalloy alloy,
Or flat irregular shaped particles such as Sendust alloy,
A magnetic shielding coating formed by mixing in a polymer compound binder is disclosed in Japanese Patent Publication No. 63-39966 and a magnetic shielding film of Permalloy, and in Japanese Patent Application Laid-Open No. 1-223627, Cr = 0.5 to 20 weight. %, S
i = 0.5 to 9 wt% (converted to atomic percentage: 1 to 16.5 at)
%), Al = 0.5 to 15% by weight, and the use of a flat magnetic iron powder coating film as a protective film for shielding is disclosed.

The reason for using the flat alloy particles in these magnetic shield films and magnetic shield materials is that when the magnetic shield material made into a paint is applied, the main surfaces of the flat alloy particles are oriented so as to be in the in-plane direction of the coating film. Therefore, the flat direction matches the direction used as the magnetic shield material, and the high magnetic permeability of the material itself can be utilized due to the small demagnetizing field derived from the flat shape. Then, it is possible to prevent deterioration of the magnetic characteristics in the in-plane direction of the coating film due to the demagnetizing field, and to obtain good magnetic shield characteristics.

<Problems to be Solved by the Invention> The above-mentioned known alloy powder for magnetic shield has the following problems.

The sendust alloy has low corrosion resistance, and when it has a flat shape, it has a large specific surface area and is easily ignited, which causes many problems in handling. Further, since it is easily rusted, magnetic characteristics are deteriorated and a poor appearance occurs.

Permalloy alloys such as permalloy alloy and molybdenum permalloy alloy are flattened not by cleavage but by rolling due to their crystal structure, so that the time required for flattening is long and the productivity is low. Further, since the flattening process takes a long time, processing strain becomes large, and high magnetic shield characteristics cannot be obtained. Further, the raw material of the permalloy alloy is about 5 to 10 times as high as that of the sendust alloy, which is very expensive.

Since the Fe-based amorphous alloy is also flattened by rolling, it has the same problem as the permalloy-based alloy.

Further, since the permalloy alloy and the Fe-based amorphous alloy have large magnetostriction, in addition to the deterioration of the magnetic properties due to the stress application during flattening, the magnetic properties also deteriorate due to the stress application when kneaded with the binder to form a paint. .

Further, since the permalloy-based alloy is soft, there is a drawback that the flat powder is deformed by stress in the coating process and the characteristics are deteriorated.

The present invention has been made under such circumstances, an object of the present invention is to provide a method for producing a soft magnetic powder for magnetic shielding, which can quickly and favorably flatten, and which has a high corrosion resistance and further has a small magnetostriction. Another object of the present invention is to provide an inexpensive magnetic shield material having a high magnetic shield effect by using this soft magnetic powder.

<Means for Solving the Problems> Such an object is achieved by the present invention of the following (1) to (9).

(1) In the ternary composition diagram (atomic ratio) of Fe, Si and Cr, A: Fe ₇₈ Si ₂₂ Cr ₀ B: Fe ₇₀ Si ₃₀ Cr ₀ C: Fe ₆₀ Si ₃₀ Cr ₁₀ D: Fe ₆₃ Si ₁₈ Cr ₁₉ E: Fe ₇₆ Si ₁₈ Cr ₆ has a composition represented by a region inside a pentagon obtained by connecting A, B, C, D, E and A in order (however, the AB line is not included). A method for producing a soft magnetic powder for a magnetic shield, comprising a step of flattening alloy particles to obtain flat soft magnetic particles, and subjecting the flat soft magnetic particles to a heat treatment.

(2) The method for producing a soft magnetic powder for magnetic shield according to the above (1), wherein a peak of surface index (002) is present in the X-ray diffraction chart of the flat soft magnetic particles after heat treatment.

(3) In the X-ray diffraction chart of the flat soft magnetic particles after the heat treatment, the peak height of the plane index (002) is represented by P (002).
And the peak height of the surface index (022) is P (022), P (002) / P (022) ≧ 0.1%.

(4) The method for producing a soft magnetic powder for magnetic shield according to any one of the above (1) to (3), wherein the saturation magnetostriction constant λs of the alloy forming the flat soft magnetic particles is 0 or less.

(5) Manufacture of the soft magnetic powder for magnetic shield according to any one of the above (1) to (4), wherein a value obtained by dividing the average particle size of the flat soft magnetic particles by the average thickness thereof is 10 to 3000. Method.

(6) The weight average particle diameter D _{50 of the} flat soft magnetic particles is 5 to 3
0 μm, and the average thickness is 1 μm or less (1)
(5) A method for producing a soft magnetic powder for magnetic shielding according to any one of (5) to (5).

(7) The method for producing a soft magnetic powder for magnetic shield according to any one of the above (1) to (6), wherein the holding temperature during heat treatment applied to the flat soft magnetic particles is 100 to 600 ° C.

(8) The method for producing a soft magnetic powder for magnetic shield according to any one of (1) to (7), wherein the flattening is performed by a medium stirring mill.

(9) A magnetic shield material comprising the soft magnetic powder for magnetic shield produced by the method according to any one of (1) to (8) above and a binder.

<Function> In the present invention, the flat soft magnetic particles constituting the soft magnetic powder for magnetic shield are obtained by flattening the alloy particles having the above composition to obtain flat soft magnetic particles, and the flat soft magnetic particles are subjected to heat treatment. It is manufactured by applying.

The present inventors have found that the alloy particles having the above composition are easily cleaved, and in particular, the cleavage occurs extremely easily when having a DO ₃ type crystal structure, which is suitable for the flat soft magnetic particles for magnetic shield. I found it.

When stress is applied to the alloy particles, cleavage occurs and flat soft magnetic particles are obtained. At this time, since the crystal plane direction in the cleavage plane is regular, the deterioration of the magnetic characteristics due to the flattening is extremely small.

Further, by cleavage, flat soft magnetic particles having a high aspect ratio (value obtained by dividing the average particle diameter by the average thickness) can be obtained, and further, the variations in the aspect ratio and the particle diameter are extremely small. Optimal.

Further, the time required for flattening is remarkably shortened and productivity is improved as compared with permalloy or the like which is flattened by rolling.

If flattening is performed with a medium stirring mill, flattening can be performed more quickly, and flat soft magnetic particles with less variation can be obtained.

Since the alloy particles are usually produced by quenching the molten alloy or crushing the ingot, the crystal structure may be disordered, but in this case, by heat treatment, DO ₃
The mold crystal structure can be adjusted, and the time required for flattening can be shortened.

The thus produced flat soft magnetic particles having the above composition have a high magnetic permeability and a low coercive force, and particularly when having a DO ₃ type crystal structure, extremely high magnetic characteristics can be obtained. Therefore, it is extremely suitable as a magnetic shield material.

The DO ₃ type crystal structure may disappear due to the stress during flattening, but in this case, the DO 3
_A type ₃ crystal structure can be formed.

The present inventors have found that a low temperature heat treatment at 100 to 600 ° C. is sufficient to form a DO ₃ type crystal structure in the alloy particles and the flat soft magnetic particles before being flattened. For this reason,
Heat treatment can be performed without worrying about ignition or sintering.

Incidentally, the presence of DO ₃ type crystal structure in X-ray diffraction chart can be confirmed by the presence of peaks of DO ₃ type crystal structure specific plane index (002).

Moreover, since the saturation magnetostriction constant λs of the alloy particles having the above composition can be set to zero or less, stress application at the time of flattening,
The application of stress when kneading with the binder to produce the shield material does not cause deterioration of magnetic permeability or increase of coercive force.

Furthermore, since the flat soft magnetic particles having the above composition have extremely high corrosion resistance, even in the case of a flat shape having a large specific surface area, they do not ignite during heat treatment, and there is a deterioration in magnetic properties due to rusting and a poor appearance. It never happens.

<Specific Configuration> The specific configuration of the present invention will be described in detail below.

The atomic ratio composition of the flat magnetic particles constituting the soft magnetic powder for magnetic shield of the present invention is A: Fe ₇₈ Si ₂₂ Cr ₀ B: Fe ₇₀ Si ₃₀ Cr ₀ C in the ternary composition diagram shown in FIG. : Fe ₆₀ Si ₃₀ Cr ₁₀ D: Fe ₆₃ Si ₁₈ Cr ₁₉ E: Fe ₇₆ Si ₁₈ Cr ₆ The inside area of the pentagon obtained by connecting A, B, C, D, E and A in order ( However, does not include the AB line).

 The reasons for limiting the composition will be described below.

The magnetic shield characteristics are insufficient outside the BC line.

Outside the CD line, the saturation magnetization is 5 kG or less, which is not preferable as a magnetic shield material and the magnetic shield effect is insufficient.

 Outside the DE line, the time required for flattening becomes long.

Outside the EA line, good corrosion resistance cannot be obtained, and in some cases there is a risk of ignition during heat treatment.

In addition, in order to further improve the corrosion resistance, the composition on the AB line is not included, that is, Cr is included. And Cr
The content of is preferably 0.1 at% or more.

A more preferable composition of the flat soft magnetic particles is F: Fe ₇₇ Si ₂₀ Cr ₃ G: Fe ₇₁ Si ₂₆ Cr ₃ H: Fe ₆₂ Si ₂₆ Cr ₁₂ I: Fe ₇₀ Si ₁₈ Cr ₁₂ in FIG. It is a region inside the pentagon obtained by connecting F, G, H, I, E, and F in order.

Incidentally, the flat soft magnetic particles, in addition to Fe, Si and Cr,
Various additional elements may be contained.

The additive element is not particularly limited, and can be selected from various metal elements such as transition metal elements and metalloid elements as necessary. The content of such additional elements is preferably 10 at% or less when the total of Fe, Si and Cr is 100 at%.

The flat soft magnetic particles may contain inevitable impurities such as N, O, and S as long as they do not adversely affect the magnetic properties.

In the present invention, it is preferable that the X-ray diffraction chart of the flat soft magnetic particles has a peak of surface index (002). These peaks indicate the presence of the DO ₃ type crystal structure.

When the peak height of the surface index (002) is P (002) and the peak height of the surface index (022) is P (022), P
If (002) / P (022) ≧ 0.1%, the effect of the present invention due to the DO ₃ type crystal structure is further enhanced.

When the Fe target is used, the (002) peak appears near 2θ = 39.5 ° and the (022) peak appears near 2θ = 57.2 °.

In the present invention, the soft magnetic powder has a maximum magnetic permeability μm of 20 to 80, especially 25 to 60, and a coercive force Hc of 1 to 20 Oe, particularly 1 to 14 Oe.

As the saturation magnetic constant λs of the alloy forming the flat soft magnetic particles, zero or less, particularly −10 × 10 ^{−6 to} 0, and further −3 × 10 ^{−6 to} 0.01 × 10 ⁻⁶ can be obtained.

The size and shape of the flat soft magnetic particles will be described below.

Flat soft magnetic particles have an average thickness of 1 μm or less, especially 0.01
It is preferably ˜1 μm. When the average thickness is less than 0.01 μm, the dispersibility in a binder decreases when the magnetic shield material is used. In addition, magnetic properties such as magnetic permeability decrease,
Insufficient shielding characteristics.

On the other hand, when it exceeds 1 μm, a coating film in which the soft magnetic powder is uniformly dispersed cannot be formed when the magnetic shield material is applied thinly, and the flat soft magnetic particles in the thickness direction of the coating film are not formed. Since the number of existing ones is small, the shield characteristics are insufficient. A more preferable result is obtained when the average thickness is 0.01 to 0.6 μm.

The average thickness may be measured with an analytical scanning electron microscope.

The average aspect ratio of the flat soft magnetic particles is preferably 10 to 3000, and more preferably 10 to 500. In the present invention, the average aspect ratio is a value obtained by dividing the average particle diameter of the flat soft magnetic particles by the average thickness.

When the average aspect ratio is less than 10, the influence of the demagnetizing field becomes large, the magnetic properties such as magnetic permeability deteriorate, and the shield properties become insufficient. On the other hand, the average aspect ratio in the flat soft magnetic particles having an average thickness within the above range is 30
If it exceeds 00, the average particle size becomes too large, so that breakage easily occurs when kneading with the binder, and the magnetic properties deteriorate.

The average particle diameter in this case means the weight average particle diameter D ₅₀ , and the weight of the flat soft magnetic particles constituting the soft magnetic powder is integrated from the smaller particle diameter, and this value is the whole soft magnetic powder. Is the particle size of the flat soft magnetic particles when it reaches 50% of the weight. The particle size in this case is a particle size measured by a particle size analyzer using a light scattering method. More specifically, the particle size analysis using the light scattering method is to measure the particle size distribution by measuring the scattering angle of Franhofer diffraction or Mie scattering using a laser beam or a halogen lamp as a light source while circulating the sample. Is. For more information, see "Powder and Industry" for example.
It is described in VOL.19 No.7 (1987).

The above D ₅₀ can be determined by the particle size distribution obtained by such a particle size analyzer.

In the present invention, the soft magnetic powder preferably has a D ₅₀ thus determined of 5 to 30 μm.

In the main surface shape of such flat soft magnetic particles, when the major axis length (maximum diameter) is a and the minor axis length (minimum diameter) is b, the average axial ratio a / b is When the magnetic shield is required to have directivity, a value as large as 1.2 or more is desirable. When the magnetic field source has a directional property, the magnetic permeability in that direction can be improved by curing the magnetic paint while applying the orientation magnetic field in that direction, and the magnetic shield effect can be enhanced.

In this case, more preferable results are obtained when a / b is 1.2 to 5. And, according to the medium stirring mill described later, such an axial ratio can be easily realized.

The major axis and the minor axis of the particles may be measured with an analytical transmission electron microscope.

 The method for producing the soft magnetic powder of the present invention will be described below.

In the present invention, the alloy particles having the composition shown in FIG. 1 are flattened to obtain flat soft magnetic particles.

The alloy particles may be produced by quenching the molten alloy or crushing the alloy ingot, and the method is not particularly limited.

The method for quenching the molten alloy is not particularly limited, but the water atomizing method is preferably used because alloy particles having a desired particle size can be obtained without a pulverizing step and the productivity is high.

The water atomization method is to inject high-pressure water into a molten alloy to solidify and powder it, and then cool it in water. The details are described, for example, in Japanese Patent Application No. 1-12267 of the present inventors. ing.

In addition to the water atomizing method, the molten metal is made to collide with the cooling base,
A method for obtaining a ribbon-shaped or flaky-shaped or granular alloy may be used. Examples of such a method include a single roll method, a twin roll method, and an atomizing method. In these methods, the obtained quenched alloy may be crushed as necessary to obtain alloy particles having a desired particle size.

When alloy particles are produced by crushing an alloy ingot, it is preferable that the ingot be subjected to a solubilization treatment and then crushed.

The average particle diameter of the alloy particles may be appropriately determined according to the particle diameter and aspect ratio of the target flat soft magnetic particles,
Usually, the weight average particle diameter D ₅₀ is 5 to 30 μm, preferably 7 to 2
It may be 0 μm.

The alloy particles are preferably subjected to a heat treatment for adjusting the crystal structure.

The means for flattening the alloy particles is not particularly limited, and any means may be used as long as the desired flattening is possible.

However, in the present invention, since the flattening of the alloy particles mainly proceeds by cleavage, it is preferable to use a means capable of efficiently performing cleavage.

Examples of such means include a medium stirring mill and a rolling ball mill. Of these, the medium stirring mill is particularly preferably used.

The medium agitating mill is an agitator also called a pin type mill, a bead mill or an agitator ball mill, and is disclosed in, for example, JP-A-61-259739, Japanese Patent Application No. 1-259739.
-12267, etc.

The thus obtained flat soft magnetic particles are preferably heat-treated. This heat treatment is for forming the DO ₃ type crystal structure as described above.

The holding temperature and the temperature holding time during the heat treatment and the heat treatment applied to the alloy particles before the flattening are 100
It is preferable to set the temperature to 600 ° C for 10 minutes to 10 hours. If the holding temperature or temperature holding time is less than the above range, the effect of the heat treatment becomes insufficient, and if it exceeds the above range, ignition or sintering tends to occur. More preferable heat treatment conditions are 300 to 5
It is 30 minutes to 2 hours at 00 ° C.

The heat treatment is preferably performed in vacuum or in an atmosphere of an inert gas such as nitrogen, hydrogen or Ar.

 Note that this heat treatment may be performed in a magnetic field.

The magnetic shield material of the present invention contains the soft magnetic powder thus obtained and a binder, and the soft magnetic powder is dispersed in the binder.

The magnetic property of the magnetic shield material of the present invention is 50 when the maximum magnetic permeability μ _{m in} a DC magnetic field when converted to 100% of the material.
Or more, preferably 100 or more, particularly 150 to 400, and even 180
Values of up to 350 are obtained, and coercive force Hc of 2 to 200e, especially 2 to 150e.

Due to such magnetic characteristics, a sufficient magnetic shield effect can be obtained.

The filling factor of the soft magnetic powder in the magnetic shield material is 60.
It is preferably ˜95 wt%.

If the filling ratio is less than 60 wt%, the magnetic shielding effect is sharply reduced, and if it exceeds 95 wt%, the soft magnetic powder cannot be firmly bound by the binder, and the strength of the magnetic shielding material decreases.

When the filling rate is 70 to 90 wt%, a particularly good magnetic shielding effect is obtained, and the strength of the shielding material is sufficient.

The binder used in the present invention is not particularly limited, and can be appropriately selected from known thermoplastic resins, thermosetting resins, radiation-curable resins, and the like.

The magnetic shield material may contain a hardener, a dispersant, a stabilizer, a coupling agent, and the like, in addition to the soft magnetic powder and the binder.

Such a magnetic shield material is usually used after being formed into a desired shape or formed into a coating composition using a necessary solvent, and then, if necessary, heated and cured.

In general, curing may be carried out in a heating oven at 50 to 80 ° C. for about 6 to 100 hours.

When the magnetic shield material of the present invention is formed into a film or a thin plate and used for magnetic shield, the thickness of the magnetic shield material is preferably 5 to 200 μm.

Such a thickness range is such that the magnetic shield material of the present invention has the above-mentioned magnetic characteristics, so that it exhibits a high magnetic shield effect even at a thickness of 5 μm, and has such a degree that the shield material is not magnetically saturated. This is because, when a magnetic field having a high strength is to be shielded, the magnetic shielding effect is not remarkably improved even if the magnetic layer is formed to a thickness exceeding 200 μm.

When the magnetic shield material of the present invention is molded or applied in a desired shape, a magnetic field having a high directionality can be obtained by applying an orientation magnetic field or mechanically orienting the magnetic shield material. When the shield material is plate-shaped or film-shaped, it exhibits a high magnetic shield effect against a magnetic field in a direction parallel to the film surface, and exhibits a sufficient effect in the above-mentioned thickness range.

When applied to the magnetic shield material, a conductive coating film of Cu, Ni or the like may be formed on the soft magnetic powder.

<Example> Hereinafter, the present invention will be described in more detail with reference to specific examples.

Example 1 In this example, flat soft magnetic particles having various compositions were produced, and the effect of the present invention was confirmed.

Alloy particles were prepared by a water atomizing method, and then the alloy particles were flattened by a medium stirring mill and further heat-treated to obtain soft magnetic powder composed of flat soft magnetic particles.

Table 1 below shows the composition of the flat soft magnetic particles, the holding temperature and the temperature holding time during the heat treatment.

The flattening by the medium stirring mill was performed until the weight average particle diameter D ₅₀ of the flat soft magnetic particles reached 15 μm, and the time required for the flattening was measured.

 Table 1 shows the results.

The average thickness is determined by analysis type scanning electron microscope, D ₅₀ was measured by a particle size analyzer utilizing light scattering.

After the heat treatment, an X-ray diffraction analysis was carried out using an Fe target for the flat soft magnetic particles, and from the obtained X-ray diffraction chart, the peak height P (002) and the surface index (022) of the surface index (002) were
Find the peak height P (022) of P (002) / P (022)
Was calculated.

 The results of the X-ray diffraction chart analysis are shown in Table 1.

The saturation magnetostriction constant λs in each composition shown in Table 1 was measured. The results are shown in Table 1.

These soft magnetic powders were immersed in 5% NaCl (20 ° C.) for 48 hours, and the corrosion resistance was examined. The evaluation of corrosion resistance shown in Table 1 is as follows.

◯: No change in appearance Δ: Lightly discolored ×: Rust on the entire surface Next, the obtained soft magnetic powder was mixed with the following binder, curing agent and solvent to prepare a magnetic shield material.

(Binder) Vinyl chloride-vinyl acetate copolymer [S-REC A (manufactured by Sekisui Chemical Co., Ltd.)] 100 parts by weight Polyurethane [Nipporan 2304 (manufactured by Nippon Polyurethane Co.)] 100 parts by weight (solid content conversion) (curing agent) Polyisocyanate [Coronate HL (manufactured by Nippon Polyurethane Co.)] 10 parts by weight (solvent) MEK 850 parts by weight The filling ratio of the soft magnetic powder in the magnetic shield material was 80% by weight.

The obtained magnetic shield material is applied to a long PET substrate with a thickness of 75 μm to a thickness of 25 μm, wound into a roll, and then 60 ° C.
It was heated at 60 minutes for curing. This was cut into a sheet to obtain a shield plate sample. As the magnetic characteristics of the shield plate sample, the coercive force (H
c) is shown in Table 1.

Place the prepared shield plate sample on the magnet, measure the leakage magnetic flux φ at the 0.5 cm position from the shield plate sample, and compare it with the magnetic flux φ ₀ without the shield plate to obtain the ratio φ / φ ₀ . The shield ratio was calculated and expressed as a relative value with sample No. 1 set to 100. The results are shown in Table 1.

Under these measurement conditions, if the shield ratio is 150 or less, a sufficient shield effect is obtained, but in reality, the smaller the shield ratio, the better.

For comparison, particles of Sendust alloy, permalloy alloy, molybdenum permalloy alloy, and Fe-based amorphous alloy were used and flattened in the same manner as above to produce a soft magnetic powder.

For these, the same measurements and evaluations as described above were performed. The results are shown in Table 1.

From the results shown in Table 1, the effect of the present invention is clear.

That is, in Sample Nos. 1 to 7 which are examples of the present invention, the flattening time is short, the corrosion resistance is high, and the saturation magnetostriction constant λs has a negative value. Then, the low coercive force required as a magnetic shield material is obtained, and in fact, the shield ratio when used as a magnetic shield material is high.

On the other hand, Sample Nos. 8 to 10 have poor magnetic shielding properties, and Sample No. 101, which does not contain Cr required for flattening, has low corrosion resistance and long flattening time. Has become.

In addition, the sendust alloy of sample No. 11 has low corrosion resistance.

Samples Nos. 12 to 14 have a flattening time that is at least twice as long as that of the samples of the present invention, and are poor in productivity. Also, sample N
o.12 permalloy alloy has low corrosion resistance, large magnetostriction,
Shielding property is low. The molybdenum permalloy alloy of sample No. 13 has insufficient corrosion resistance and insufficient shielding characteristics. The Fe-based amorphous alloy of Sample No. 14 has a large magnetostriction, and when used as a shield material, when a stress is applied, a predetermined shield effect may not be obtained.

[Example 2] In this example, in Sample No. 3 shown in Table 1 above, the heat treatment conditions were variously changed and the characteristics were examined. The conditions of each measurement were the same as in Example 1.

 The results are shown in Table 2 below.

In addition, X using sample No. 24 and Fe target
The line diffraction charts are shown in FIG. 2 and FIG. 3, respectively.

Example 3 The alloy particles having the compositions shown in Table 1 above were heat-treated at 450 ° C. for 1 hour and then flattened under the same conditions as in Example 1. The flattening time was 10% or more. It was shortened.

 The effects of the present invention are apparent from the above examples.

<Effects of the Invention> The flat soft magnetic particles constituting the soft magnetic powder in the present invention have a high magnetic permeability and a low coercive force, and can have a saturation magnetostriction constant λs of zero or less, and further have good corrosion resistance. Therefore, it is extremely suitable as a magnetic shield material.

Further, since the alloy particles that are easily cleaved are used as the raw material,
Flat soft magnetic particles having a high aspect ratio can be produced in a short time, and after flattening, a heat treatment is performed to form a predetermined crystal structure, so that extremely high magnetic characteristics can be obtained.

The magnetic shield material of the present invention using such soft magnetic powder is inexpensive and has high performance, and can be applied to an extremely wide range in addition to magnetic shields for speakers, CRTs and the like.

[Brief description of drawings]

FIG. 1 is a ternary composition diagram showing the composition of flat soft magnetic particles constituting the soft magnetic powder produced by the present invention. 2 and 3 show X of flat soft magnetic particles, respectively.
It is a line diffraction chart.

Claims (9)

(57) [Claims] 1. In a ternary composition diagram (atomic ratio) of Fe, Si and Cr, A: Fe ₇₈ Si ₂₂ Cr ₀ B: Fe ₇₀ Si ₃₀ Cr ₀ C: Fe ₆₀ Si ₃₀ Cr ₁₀ D: Fe ₆₃ Si ₁₈ Cr ₁₉ E: Fe ₇₆ Si ₁₈ Cr ₆ , the composition represented by the area inside the pentagon obtained by sequentially connecting A, B, C, D, E, and A (but not including the AB line) A method for producing a soft magnetic powder for magnetic shield, comprising the step of flattening the alloy particles having the above to obtain flat soft magnetic particles, and subjecting the flat soft magnetic particles to a heat treatment. 2. The method for producing a soft magnetic powder for a magnetic shield according to claim 1, wherein a peak of the plane index (002) is present in the X-ray diffraction chart of the flattened soft magnetic particles after the heat treatment. 3. An X-ray diffraction chart of the flat soft magnetic particles after heat treatment, wherein the peak height of the plane index (002) is P
3. P (002) / P (022) ≧ 0.1% when P (022) is the peak height of (002) and the surface index (022).
A method for producing the soft magnetic powder for magnetic shield according to. 4. The method for producing a soft magnetic powder for magnetic shield according to claim 1, wherein the alloy constituting the flat soft magnetic particles has a saturation magnetostriction constant λs of 0 or less. 5. The method for producing a soft magnetic powder for a magnetic shield according to claim 1, wherein a value obtained by dividing an average particle diameter of the flat soft magnetic particles by an average thickness thereof is 10 to 3000. . 6. The weight average particle diameter D _{50 of the} flat soft magnetic particles.
Is 5 to 30 μm, and the average thickness is 1 μm or less. 6. The method for producing a soft magnetic powder for a magnetic shield according to claim 1, wherein 7. The method for producing a soft magnetic powder for a magnetic shield according to claim 1, wherein a holding temperature during heat treatment applied to the flat soft magnetic particles is 100 to 600 ° C. 8. The method for producing a soft magnetic powder for a magnetic shield according to claim 1, wherein the flattening is performed by a medium stirring mill. 9. A magnetic shield material comprising the soft magnetic powder for magnetic shield manufactured by the method according to claim 1 and a binder.