TW202219291A - Soft magnetic alloy powder and green compact thereof, and manufacturing methods therefor - Google Patents

Abstract

Provided are: a soft magnetic alloy powder which has great saturation magnetization and high affinity for a resin and from which a dust core having high magnetic permeability and high saturation magnetic flux density can be manufactured; a green compact thereof; and manufacturing methods therefor. This soft magnetic alloy powder, containing, in terms of mass concentration, 40.0-50.0% of Ni and 10-10,000 ppm of Cl, with the remainder consisting of Fe and inevitable impurities, is characterized by having an average particle diameter of 0.10-2.00 [mu]m and an average crystallite diameter of at least 0.5 times the average particle diameter. Moreover, the concentration of Ni, at an arbitrary point in a particle in the range from a core of the particle to a position which is 0.9 times the radius of the particle, is preferably 0.7-1.3 times the average Ni content of the whole particle. Consequently, the soft magnetic alloy powder has great saturation magnetization and high affinity for a resin, and facilitates the manufacture of a dust core having high magnetic permeability and high saturation magnetic flux density.

Description

Soft magnetic alloy powder, powder compact thereof, and method for producing the same

The present invention relates to alloy powders and powder compacts thereof, in particular to soft magnetic alloy powders suitable for core materials for inductors used at high frequencies, compact powders bonded thereto with resin, and methods for producing the same.

In the field of portable devices, especially in the small portable devices represented by smartphones and tablet PCs, high-performance and multi-functional systems have made remarkable progress in recent years. Along with this, there is also a strong demand for increasing the number of inductors to be mounted in the power supply circuit to be mounted, or to cope with the large current accompanying the high functionality of the integrated circuit IC. In addition, in response to the demand for further miniaturization and thinning of portable equipment, the demand for miniaturization and lowering of the coil itself has also increased.

In the core material of inductors operating at high frequencies, it is necessary to suppress eddy current loss, so conventionally, ferrite with high resistance has been used. However, due to the low saturation magnetic flux density of the oxide-rich iron system and the poor DC superposition characteristics, a large current cannot flow despite the increasing demand for high current in power inductors. Therefore, metal-based soft magnetic materials with high saturation magnetic flux density have recently attracted attention as core materials for small inductors. However, metal-based soft magnetic materials have low electrical resistance, and must be micronized in order to suppress eddy current loss.

Originally, in order to function as an inductor, a large inductance is a precondition, but since the inductance is proportional to the magnetic permeability of the core material, a material with high magnetic permeability is desired as the core material.

Furthermore, as an excellent high-permeability alloy developed, there is a Ni—Fe alloy, which is called a permalloy. It is known that the magnetic properties of the permalloy system vary greatly depending on the amount of Ni, and are used in various applications according to the magnetic properties.

For example, in a permalloy with a composition containing about 78% Ni, since both the crystalline magnetic anisotropy and the magnetostriction constant are almost zero, the initial permeability becomes the largest in the Ni-Fe alloy. The alloy of this composition is generally called 78 permalloy or permalloy A, which is used in the magnetic core of transformers, etc. The addition of Mo or Cu to this 78 permalloy to further increase the magnetic permeability is called permalloy C, which can be used for the magnetic core or magnetic head of the transformer.

In addition, the permalloy with a Ni content of about 45%, which is less than the 78 permalloy, is called 45 permalloy or permalloy B, and the initial permeability of the permalloy system of this composition is less than 78 Permalloy has a high saturation magnetic flux density, so it is widely used for transformer cores, magnetic poles, and magnetic shielding.

These permalloy alloy powders are conventionally produced by a gas atomization method or a mechanical pulverization method.

In recent years of operating frequencies of switching power supplies, in order to suppress eddy current loss, the particle size required for metal-based soft magnetic materials has reached a level of 1 μm or less in average particle size. However, the size of the fine powder that can be produced by the gas atomization method is limited to a size of several tens of μm in average particle size, and the production of permalloy powder with an average particle size of 1 μm or less is impossible.

In addition, it is known that ductile alloys such as permalloys re-agglomerate when micronized, so they cannot be pulverized to a size with an average particle size of 1 μm or less by a mechanical pulverization method. In addition, due to the strain introduced during pulverization , and the soft magnetic properties are greatly deteriorated, and the high magnetic permeability originally possessed by permalloy cannot be obtained.

In the production method of fine particles having an average particle diameter of 1 μm or less of permalloy A, as a production method other than the above, Patent Document 1 discloses a gas-phase reduction method using nickel chloride and ferric chloride as main raw materials. The alloy powder of permalloy A produced by (also referred to as "chemical vapor deposition method" = Chemical Vapor Deposition, hereinafter also referred to as "CVD method"). Moreover, the patent document 2 also discloses the method of manufacturing the alloy powder of Permalloy A and C by the same gas-phase reduction method. Furthermore, Patent Document 3 discloses an alloy powder of Permalloy B (45%Ni-55%Fe) produced by using oxides of nickel and iron as raw materials with a reducing gas such as hydrogen. Prior Art Documents Patent Documents

Patent Document 1: Japanese Invention Patent No. 4209614 Patent Document 2: Japanese Patent Laid-Open No. 2003-49203 Patent Document 3: Japanese Patent Laid-Open No. 2012-197474

The problem to be solved by the invention

However, the objects of Patent Document 1 and Patent Document 2 are limited to alloys in the so-called Ni-rich composition range where the Ni content is 55 to 90% by mass, and are permalloys of a type that emphasizes initial permeability and has a low saturation magnetic flux density. Although the saturation magnetic flux density is higher than that of ferrite, the saturation magnetic flux density of the level required by current inductors is completely insufficient.

The fine powder of these soft magnetic materials is used as the magnetic core of the inductor, and the fine powder must be formed into a specific shape in a state of being electrically insulated from each other. Therefore, it is kneaded with an insulating resin to produce a powder of a specific shape. It is used as a powder magnetic core.

The magnetic properties of the powder magnetic core are not only the magnetic properties of the soft magnetic powder, but also largely depend on the filling state of the soft magnetic powder. The lower the filling rate, the lower the magnetic properties of the powder magnetic core.

In addition, from the viewpoint of reducing the eddy current loss, the smaller the particle size of the soft magnetic powder, the better, but the conventional sub-micron soft magnetic powder is prone to agglomeration when kneading with the resin, because the resin does not spread over each soft magnetic powder. On the surface of the particles, the powder particles are electrically short-circuited to each other, and the eddy current loss increases, and there are cases where the advantages of the specially produced fine powder cannot be exerted.

In addition, the target of Patent Document 3 is an alloy whose Ni content corresponds to the composition range of the so-called permalloy B in which the content rate of Ni corresponds to 40 to 50% by mass, which is a composition range in which a high saturation magnetic flux density can be expected. The solid-phase reduction method of oxides as raw materials, and the reduction temperature is very low in the range of 400°C to 700°C (which can be listed as advantages), so the resulting Ni-Fe alloy particles have poor sphericity and are formed into powder magnets. The filling rate of the core is low and the saturation magnetic flux density becomes low. In addition, due to the low reduction temperature, the diffusion rate of atoms is insufficient, so the uniformity of the composition or structure in the particle is low, which hinders the smooth movement of the magnetic wall inside the particle, the coercive force increases, and the magnetic permeability of the powder magnetic core is high. becomes lower and the loss increases.

The purpose of the present invention is to solve the problem of the prior art, and to provide a soft magnetic alloy with high magnetic permeability, high saturation magnetic flux density and low loss, which can manufacture a powder magnetic core with high affinity with resin and large saturation magnetization. pink. means of solving problems

The inventors of the present invention ensured that by improving the individual magnetic properties of the permalloy B alloy powder with an average particle size of 1 μm or less, and at the same time improving the affinity between the alloy powder and the resin, the resin can sufficiently coat the particle surfaces of the respective alloy powders. The electrical insulating properties of the particles of the alloy powder can be carefully examined for the composition and particle morphology of the alloy powder in the dust core with excellent high-frequency soft magnetic properties. As a result, it was found that it is important to include a certain amount of Cl in the permalloy B alloy powder, and to improve the homogeneity within each particle of the alloy powder.

Also, a method for producing the above-mentioned Permalloy B alloy with high homogeneity by the CVD method is examined. Conventionally, including Patent Document 1, in the production of permalloy powder by the CVD method, the reduction of Ni chloride gas and Fe chloride gas is carried out simultaneously. However, compared with the reduction of Ni chloride, the reduction of Fe chloride The reduction is difficult, so Fe can only be alloyed to about 15-25% by mass in Ni. Therefore, it has been difficult to manufacture the permalloy B alloy system containing 50 to 60 mass % of Fe by the CVD method. Therefore, the inventors of the present invention conducted intensive research on the production method of permalloy B alloy using the CVD method, and as a result, novelly found that by performing the reduction reaction of Ni and Fe in sequence without the same time, a homogeneous alloy powder can be obtained. method.

The present invention has been completed by further examination based on such knowledge. That is, the gist of the present invention is as follows. [1] A soft magnetic alloy powder comprising Ni: 40.0-50.0% and Cl: 10-10000 ppm in terms of mass concentration, the remainder being an alloy powder composed of Fe and unavoidable impurities, characterized in that: The average particle size of the alloy powder is 0.10-2.00 μm, and the average crystallite size is 0.5 times or more of the aforementioned average particle size. [2] The soft magnetic alloy powder according to [1], wherein in the alloy powder, the Ni concentration at any point in the particle within the range from the center of the particle to 0.9 times the radius of the particle is the particle The overall average Ni content is 0.7 to 1.3 times. [3] The soft magnetic alloy powder according to [1] or [2], wherein the coercive force of the alloy powder is 15 Oe or less. [4] The soft magnetic alloy powder according to any one of [1] to [3], wherein the alloy powder has a saturation magnetization of 130 emu/g or more. [5] A compacted powder body, characterized by a combination of the soft magnetic alloy powder according to any one of [1] to [4] and a resin. [6] The powder compact according to [5], wherein the resin is a thermosetting resin, an ultraviolet curing resin or a thermoplastic resin. [7] A method for producing a soft magnetic alloy powder, characterized in that an alloy powder is generated by a chemical vapor method, and the alloy powder contains Ni: 40.0-50.0% and Cl: 10-10,000 ppm in terms of mass concentration, and the remainder is The alloy powder partly composed of Fe and unavoidable impurities, the average particle size of the alloy powder is 0.10~2.00μm, and the average crystallite size is more than 0.5 times the above-mentioned average particle size. [8] The method for producing a soft magnetic alloy powder according to [7], wherein in the alloy powder, the Ni concentration at any point within the particle within a range from the center of the particle to 0.9 times the radius of the particle It is 0.7 to 1.3 times the average Ni content of the entire particle. [9] The method for producing a soft magnetic alloy powder according to [7] or [8], wherein the chemical vapor method reduces Ni chloride to form Ni particles, and a reduction reaction of Fe chloride is carried out on the surface of the Ni particles, A method of obtaining alloy particles with a uniform composition within the particles by forming composite particles having the Ni particles as cores and coating the surface with Fe, and then performing solution treatment in a temperature range where γNi-Fe solid solution single phase is formed. [10] The method for producing a soft magnetic alloy powder according to [9], wherein the temperature of the reduction reaction is 800 to 1100°C, and the temperature of the solution treatment is 900 to 1300°C. [11] A method for producing a powder compact, characterized by generating a soft magnetic alloy powder by a chemical vapor method, mixing resin in the soft magnetic alloy powder, and performing compression molding, wherein the soft magnetic alloy powder is a mass Concentration meter, contains Ni: 40.0~50.0% and Cl: 10~10000ppm, and the rest is composed of Fe and unavoidable impurities. The average particle size of the alloy powder is 0.10~2.00μm, and the average crystallite diameter It is 0.5 times or more of the aforementioned average particle size. [12] The method for producing a powder compact according to [11], wherein in the alloy powder, the Ni concentration at any point within the particle within the range from the center of the particle to 0.9 times the radius of the particle is The average Ni content of the whole particle is 0.7 to 1.3 times. [13] The method for producing a powder compact according to [11] or [12], wherein the chemical vapor method reduces Ni chloride to form Ni particles, and the reduction reaction of Fe chloride is carried out on the surface of the Ni particles to form A method of obtaining alloy particles having a uniform composition within the particles by performing solution treatment in a temperature range where a single phase of a γNi-Fe solid solution is obtained after the composite particles having the above-mentioned Ni particles as cores and coating the surface with Fe. [14] The method for producing a powder compact according to [13], wherein the temperature of the reduction reaction is 800 to 1100°C, and the temperature of the solution treatment is 900 to 1300°C. [15] The method for producing a powder compact according to any one of [11] to [14], wherein the resin is a thermosetting resin, an ultraviolet curing resin or a thermoplastic resin. effect of invention

According to the present invention, a soft magnetic alloy powder system having a large saturation magnetization and excellent resin adhesion can be easily produced, and an industrially significant effect can be achieved. In addition, according to the present invention, there is also an effect of facilitating the manufacture of a powder magnetic core with high magnetic permeability, high magnetic flux density, and low loss.

Therefore, according to the present invention, it is possible to provide Ni-Fe-based soft magnetic alloy powder capable of producing dust cores with high saturation magnetic flux density and excellent DC superposition characteristics. The Ni-Fe-based soft magnetic alloy powder of the present invention can be used as a Electronic parts materials are expected to play an important role in the future as the technological trend of the high frequency of electronic equipment and the rapid progress of miniaturization.

The form of carrying out the invention

Hereinafter, embodiments of the present invention will be described in detail. [Composition of alloy powder] The soft magnetic alloy powder of the present invention belongs to the so-called permalloy, which is a Ni-Fe binary system alloy, and belongs to the powder of the alloy called permalloy B with Ni content of about 45%. The soft magnetic alloy powder of the present invention In terms of mass concentration, it contains Ni: 40.0~50.0% and Cl: 10~10000ppm, and the remaining part is composed of Fe and inevitable impurities. The average particle size of the alloy powder is 0.10~2.00μm, The average crystallite size is 0.5 times or more the aforementioned average particle size. Furthermore, the Ni concentration (%) at any point in the particle within the range from the center of the particle to 0.9 times the radius of the particle of the aforementioned alloy powder is preferably the average Ni content (%) of the entire particle. ) 0.7~1.3 times. Hereinafter, % and ppm in the composition mean mass concentration.

Next, the reason why the composition of the alloy powder is limited will be described. [Ni: 40.0~50.0%] The Ni content of the alloy powder of the present invention is limited to a range of 40.0 to 50.0%. By setting it as this range, the coercive force is low, and the saturation magnetic flux density and magnetic permeability of an alloy become high. When the Ni content is less than 40.0%, the saturation magnetic flux density and the magnetic permeability of the alloy are greatly reduced at the same time. On the other hand, when the Ni content is higher than 50.0%, the saturation magnetic flux density of the alloy rapidly decreases. Preferably it is 43.0-50.0%, More preferably, it is 45.0-50.0%.

[Cl: 10~10000ppm] The addition of Cl (chlorine) greatly affects the insulating properties between the powder particles and the volume ratio of the soft magnetic powder in the resin when the powder magnetic core is produced by mixing with the resin. That is, the presence of Cl in this range increases the affinity with the resin, increases the packing density of the powder, provides a high magnetic permeability, and facilitates the manufacture of a dust core with a high saturation magnetic flux density. When the content of Cl is less than 10 ppm, the effect of improving the affinity between the soft magnetic powder and the resin is insufficient, and the surface of each soft magnetic powder particle cannot be coated with the resin. Therefore, the electrical insulation between the soft magnetic powder particles is insufficient, and the eddy current loss increases. big. On the other hand, when the content rate of Cl is more than 10000 ppm, rust is generated and the soft magnetic powder is corroded, so that the coercive force increases and the saturation magnetization decreases. Therefore, the content rate of Cl is limited to the range of 10-10000 ppm, Preferably it is 30-1000 ppm, More preferably, it is 50-500 ppm.

In addition, the degree of the above-mentioned rust formation (rust formation rate) can be investigated by the method for measuring the rust resistance of alloy powder. In this rust resistance measurement method, the alloy powder is embedded in resin and fixed, and then the cross section is mirror-polished to obtain a test piece for rust resistance measurement. 20 particles were randomly selected, the presence or absence of rust was observed, and the proportion of rusted particles (rust rate) was calculated. Furthermore, the constant temperature and humidity tank was maintained under the conditions of temperature: 60°C, relative humidity: 95%, and the holding time in the constant temperature and humidity tank was set to 2000 hours. The rust rate of the alloy powder of the present invention obtained in this way is preferably 10% or less from the viewpoint of not causing problems in use. Furthermore, it is more preferable that it is 5% or less.

[Inevitable impurities] The remainder other than the above-mentioned components is Fe and unavoidable impurities. Moreover, as an unavoidable impurity element other than Fe, elements, such as C, N, P, S, Mn, Cu, and Al, are mentioned. These unavoidable impurities are elements that lower the saturation magnetization of the alloy powder, but if they are contained in a total amount of 3% or less, they are tolerable because they do not cause a fatal reduction in magnetic properties in practical use. Furthermore, from the viewpoint of improving the saturation magnetic flux density of the magnetic core, the content of the above elements is more preferably 1% or less in total.

[Average particle size of alloy powder: 0.10~2.00μm] Next, the reason for limiting the average particle diameter will be described. If the average particle size of the alloy powder is in the range of 0.10 to 2.00 μm, the coercive force of the soft magnetic powder is low, it is not easy to aggregate even if it is kneaded with the resin, and the powder filling rate in the resin is also good. When used as a powder magnetic core The saturation magnetic flux density becomes higher. However, if the average particle diameter is less than 0.10 μm, the coercive force of the soft magnetic powder increases. In addition, due to the strong cohesion, when kneading with the resin, the soft magnetic powders are in direct contact with each other without passing through the resin, and are not easily dispersed to form a bulky aggregate. Therefore, the fluidity of the magnetic material in the resin is poor, and the filling rate is poor. As the density increases, the saturation magnetic flux density of the dust core decreases, and the electrical insulation between the soft magnetic powder particles cannot be ensured, so the eddy current loss when used as the dust core increases. On the other hand, if the average particle size is larger than 2.00 μm, even if the insulation between particles can be ensured, the eddy current in the particles becomes a size that cannot be ignored due to the large particle size, and the eddy current loss when used as a powder magnetic core cannot be ignored. It is not appropriate to increase. Therefore, the average particle size is limited to the range of 0.10 to 2.00 μm.

The method for measuring the average particle size is to observe and photograph the alloy powder particles with a scanning electron microscope (SEM), and analyze the SEM image at a magnification of 20,000 times and measure the number of 1,000 to 2,000 particles, and obtain the number-based D50. Furthermore, it is preferably 0.20 to 1.50 μm, more preferably 0.20 to 1.00 μm.

[Average crystallite diameter] Next, the average crystallite diameter will be described. Usually, one particle is composed of a complex of plural crystals with different orientations. The so-called crystallites refer to individual crystals constituting the complex. Within the range of each of these crystals, the crystal orientations are uniform, and each can be regarded as a single crystal. In X-ray diffraction of a single crystal, at a certain incident angle, since all the crystal lattices satisfy Bragg's diffraction conditions at the same time, extremely sharp diffraction peaks are obtained. On the other hand, when the crystallite size (also referred to as "crystallite diameter") decreases, the number of crystallites (crystallites) constituting the particle increases, and each crystal has a different crystallographic orientation, so the width of the diffraction peak is increased. widen. In the X-ray diffraction method, the crystallite diameter can be calculated using the Scherrer formula. In the present invention, the crystallite diameter is defined by the value calculated by "JIS H 7805 Method for Measuring the Crystalline Diameter of Metal Catalysts by X-ray Diffraction".

When comparing particles of the same particle size, the larger the crystallite size, the higher the crystallinity, and since it is close to the value of the saturation magnetization of a single crystal, the coercivity decreases while showing a large saturation magnetization. On the other hand, when the crystallite size is small, the saturation magnetization decreases due to a structure with many grain boundaries or defects. In addition, they also become obstacles to the movement of the magnetic wall at the same time, so the coercive force is also increased. Therefore, from the viewpoint of soft magnetic properties, the crystallite diameter should preferably be large.

From the viewpoint of preferably having an internal structure substantially close to that of a single crystal, the average crystallite size is limited to 0.5 times or more the average particle size, that is, a size equal to or more than half of the average particle size. More preferably, it is 0.7 times or more of the average particle diameter, and particularly preferably 0.8 times or more of the average particle diameter.

In addition, the upper limit of the ratio of the average crystallite diameter and the average particle diameter is substantially 1.0. That is, when the particle is formed of a single crystal, the crystallite diameter = particle diameter, and the ratio is logically 1.0. Here, the substantial meaning is that the average crystallite diameter is obtained by X-ray diffraction as described above, but the average particle diameter is obtained based on the image analysis of SEM observation. Therefore, due to the difference in the measurement methods of the two, even when all the particles are completely single crystals, there is a possibility that the average crystallite diameter and the average particle diameter may not all be the same value, and the ratio may exceed 1.0. Therefore, the above-mentioned The limit is essentially taken as 1.0.

[Indicator of Ni concentration homogeneity inside particle] Next, the homogeneity index of the Ni concentration inside the particle will be described. As described above, it is difficult to obtain fine powder with an average particle diameter of 1 μm or less, which is the object of the present invention, in the conventional atomization method for the production of permalloy powder, and the magnetic properties are also poor. Therefore, when a permalloy powder is produced by a conventional CVD method that can produce a fine powder with an average particle size of 1 μm or less, Ni is simultaneously produced in the production of the permalloy powder by the conventional CVD method. The reduction of chloride gas and Fe chloride gas, but compared with the reduction of Ni chloride, the reduction of Fe chloride is more difficult, so it is easy to generate particles containing more Ni than Fe. In Ni, only Fe can be reduced. Alloy to about 15 to 25 mass %. It was found that even if a large amount of unreacted chloride remains regardless of the yield, even if an excess amount of Fe chloride gas is charged to forcibly increase the Fe concentration, Ni is rapidly reduced, so the center of the particle is The Ni concentration in the vicinity is high, and the Fe concentration in the vicinity of the surface tends to be high, making it difficult to produce particles with high homogeneity. However, by using the CVD method of the present invention described later, a homogeneous alloy powder can be obtained.

Since the experiment related to the above-mentioned homogeneity index was performed, the content thereof will be explained. Using a CVD reactor, NiCl ₂ with a purity of 99.5 mass % and FeCl ₃ with a purity of 99.5 mass % were prepared so that the value of the Ni content rate was 46.0 mass % or 48.0 mass %. The conventional CVD method produces Ni-Fe alloy powder.

In Examples 1 to 4 of the present invention of the CVD method of the present invention, NiCl ₂ is first vaporized at 1000° C. in a reaction apparatus, reacted with hydrogen gas, and fine particles of Ni serving as nuclei are produced, and then, NiCl 2 is introduced thereinto. FeCl3 is _gasified at 1000°C, reacts with hydrogen, and precipitates and grows Fe on the surface of Ni particles. Finally, the composite particles are subjected to solution treatment at 1100°C, and then cooled to recover Ni. -Fe alloy powder.

In addition, in the conventional examples 1 and 2 of the conventional CVD method, a mixture of NiCl ₂ and FeCl ₃ in a ratio such that Fe becomes a large excess is continuously charged into the reaction apparatus regardless of the yield, and heated to 1000° C. In the state of argon, NiCl ₂ and FeCl ₃ are simultaneously vaporized by using argon gas as a carrier gas. Then, the chloride vapor is brought into contact with and mixed with hydrogen, and a reduction reaction occurs to generate a fine powder of Ni—Fe alloy.

In addition, in both the present invention example and the conventional example, the obtained alloy powder was subjected to a dechlorination step of washing with pure water to adjust the chlorine content.

Table 1 shows the chemical composition, average particle size, the minimum and maximum values of Ni concentration in the particles, and the difference between them and the average Ni content of the alloy powders obtained in Examples 1 to 4 of the present invention and Conventional Examples 1 and 2. ratio, and also shows magnetic properties.

In addition, the composition of Ni, Fe, and Cl was measured by the wet method, and the average particle diameter was measured by the image analysis of a scanning electron microscope. In addition, the Ni concentration in the particle|grains was calculated|required by performing analysis by the energy dispersive X-ray analysis method (EDX) mentioned later.

FIG. 2 shows an example of the distribution of the Ni concentration in the particles of Conventional Example 1 shown in Table 1. FIG. The horizontal axis of Fig. 2 shows the position after dividing the center position (center side) of the particle as 0 and the surface (surface side) of the particle as 10, and the vertical axis represents the Ni concentration (mass %) . In Fig. 2 of the measurement example of the distribution of Ni concentration in this conventional example 1, the Ni concentration in the vicinity of the surface is reduced to about 10.1%, and in the center part, it becomes as high as 72.4%, and the Ni concentration in the particles cannot be obtained. homogeneity. The reason for this is that in the conventional CVD method, Ni chloride gas and Fe chloride gas are mixed and flowed to the reaction tube, and are simultaneously reduced with hydrogen to obtain alloy powder. The particles are concentrated near the center, and Fe systems that are not easily reduced are concentrated near the surface of the particles.

On the other hand, in Fig. 1 showing an example of the distribution of Ni concentration in the particles of Example 1 of the present invention shown in Table 1, the distribution of Ni concentration from the center of the particle to the vicinity of the surface is in the range of 45.4 to 48.1%. , to obtain the homogeneity of Ni concentration. The reason for this is that a permalloy powder having a uniform composition from the surface to the center of the particle can be produced by adding a solution treatment step that was not present in the conventional process.

As is clear from Table 1, the Ni—Fe alloy powders of the examples of the present invention exhibited very excellent magnetic properties.

As described in the above experiments, it is clear that the homogeneity inside the particle greatly affects the magnetic properties, so as an index for evaluating the homogeneity inside the particle, the Ni concentration in the particle is focused. That is, the Ni concentration at any point in the particle within the range from the center of the particle to 0.9 times the radius of the particle is preferably 0.7 to 1.3 times the average Ni content of the entire particle.

Here, the reason for using the inside of the particle from the center of the particle to 0.9 times the particle radius is because the surface of the particle is affected by oxidation, so it is excluded, and the inside of the particle is not affected by oxidation. condition to confirm homogeneity.

The value of the above-mentioned Ni concentration is also described in the above-mentioned experimental example, the powder is embedded in the resin, and the cross-section of any particle after being cut by a focused ion beam (FIB) processing apparatus is analyzed by energy dispersive X-ray analysis method ( EDX) analysis. The Ni content obtained by averaging the entire particles is a value measured so that the beam diameter of EDX and the particle diameter are matched. If the range from the minimum value to the maximum value of the Ni concentration in the particle is in the range of 0.7 to 1.3 times the average Ni content rate, the internal homogeneity of the particle is guaranteed. More preferably, it is in the range of 0.8 to 1.2 times, and particularly preferably in the range of 0.9 to 1.1 times.

The homogeneity of the Ni concentration can be judged by using the above-mentioned index of homogeneity inside the particle, and by setting it within the above-mentioned suitable range, an alloy powder having excellent magnetic properties such as coercive force and saturation magnetization can be obtained.

[Magnetic properties of alloy powder] [Coercive force] The coercive force of the alloy powder in the present invention is measured by placing the alloy powder in a designated container, melting, solidifying and fixing the paraffin wax, using a vibrating sample type magnetometer (VSM), in an external magnetic field: 1200kA/m Measure it under conditions. In applications such as inductors or magnetic cores of transformers, which are the object of the present invention, the coercive force should be small. Specifically, it is preferably 15 Oe or less, more preferably 10 Oe or less.

[Saturation magnetization] The measurement of the saturation magnetization of the alloy powder in the present invention is the same as the measurement of the aforementioned coercive force, using a VSM, and is measured under the conditions of an external magnetic field: 1200 kA/m. In applications such as inductors or magnetic cores of transformers, which are the object of the present invention, the saturation magnetization is preferably large. Specifically, it is preferably 130 emu/g or more, more preferably 142 emu/g or more.

[Manufacturing method of alloy powder] Next, the manufacturing method of the alloy powder of this invention is demonstrated. The alloy powder of the present invention is produced by the CVD method. The CVD method, as described above, reacts alloy elements such as Ni and Fe with high-temperature chlorine gas to generate chloride gas of each element, or the chloride gas of each element such as Ni and Fe is heated to a high temperature to vaporize the chloride gas. A method of obtaining an alloy powder containing a desired composition of Ni, Fe, etc. by reacting with a reducing gas such as hydrogen at a suitable temperature to reduce the chloride to obtain a mixed gas obtained by mixing a gas in a specific ratio .

However, the CVD method of the present invention is different from the conventional CVD method in that the reduction of Ni chloride and Fe chloride is not performed at the same time, but in the initial stage of the CVD reaction, Ni chloride is first reduced to generate Ni fine particles, and then Using the catalytic effect of the generated Ni fine particles, the reduction reaction of Fe chloride is accelerated on the surface of the Ni fine particles, and composite particles having Ni fine particles as cores and Fe-covered surfaces are produced. Afterwards, the process of obtaining Ni-Fe alloy powder particles with a uniform composition in the particles includes a solution treatment in a temperature range of γNi-Fe solid solution single phase, and a series of processes are completed inside the CVD reactor. By.

Here, in the reduction reaction of Ni chloride performed in the initial stage of the CVD reaction, the Ni chloride is heated to 800 to 1100° C. to be vaporized, and is reacted with a reducing gas (for example, hydrogen) to generate Ni fine particles (about 0.05~1.5μm), the subsequent reduction reaction of Fe chloride is on the surface of the generated Ni fine particles, and the Fe chloride gasified at high temperature (about 800~1100℃) and reducing gas (such as , hydrogen) reaction. When the temperature of this reduction reaction is less than 800°C, a sufficient reduction reaction does not occur, and when it exceeds 1100°C, the equilibrium constant of the reduction reaction decreases, so the reduction rate decreases and the residual chlorine increases. Therefore, the reduction temperature is preferably in the range of 800 to 1100°C, more preferably in the range of 900 to 1000°C. In addition, it is preferable to carry out the said solution processing performed after that in the temperature range of 900-1300 degreeC. When the temperature is less than 900°C, sufficient homogenization does not occur, so the lower limit temperature is made 900°C. If the solution treatment temperature is high, there is no obstacle from the viewpoint of improving the homogeneity and increasing the crystallite size. When the temperature is 1300°C, the upper limit temperature is set to 1300°C, more preferably in the range of 1000 to 1200°C, since the generated particles are fused to each other during the cooling process to generate connected particles, and the magnetic properties are lowered.

In addition, in the CVD method of the alloy powder of the present invention, the concentration of chloride gas, the concentration and flow rate of reducing gas, and the temperature and reaction time of the reduction reaction should be appropriately adjusted to obtain the desired alloy powder.

After the above reduction reaction, the obtained alloy powder is further subjected to a dechlorination step. The dechlorination step is a step of adjusting the chlorine concentration by washing the obtained alloy powder with a solvent. As the solvent to be used, a solvent capable of dissolving unreacted chloride or by-products generated by the reduction reaction is preferably used. As such a solvent, water, alcohol, etc. can be illustrated. When a specific chlorine concentration is reached, the dechlorination step is completed, and the target alloy powder is obtained.

[Pressed powder] By dispersing the alloy powder of the present invention in a resin, a compacted powder body with high packing density and low magnetic core loss can be easily produced.

There is no particular limitation on the method for producing the powder compact, and it can be produced by a well-known method. First, the alloy powder is mixed with a resin as a binder to obtain a mixture of the alloy powder dispersed in the resin. In addition, if necessary, the obtained mixture may be granulated to obtain a granulated product. By compression-molding the mixture or the granulated product, a compact (powder compact) is obtained.

The resin to be mixed as the binder is preferably a resin having improved affinity with the surface of the alloy powder, specifically, a thermosetting resin, an ultraviolet-curable resin or a thermoplastic resin. As a thermosetting resin, an epoxy resin, a phenol resin, a urea resin, a melamine resin, an unsaturated polyester resin, a polyurethane resin, a diallyl phthalate resin, etc. are mentioned. Moreover, as an ultraviolet curable resin, a urethane acrylate resin, an epoxy acrylate resin, a polyester acrylate resin, etc. are mentioned. In addition, as a thermoplastic resin, polyphenylene sulfide resin and nylon resin (polyamide resin) are mentioned. These resins show the effect of improving the affinity with the surface of the aforementioned alloy powder.

Then, the mixture or the granulated powder is filled in a mold, and compression molding is performed to obtain a compact (dust core) having the shape of the compact to be produced. Furthermore, when a thermosetting resin is used as the resin, it is preferable to perform heat treatment at 50 to 200°C. The obtained pressed powder system is a combination of the aforementioned alloy powder and resin tightly bound.

[Iron loss of compacted powder] The core loss (iron loss) is the loss caused by the physical properties of the magnetic core of an inductor or a transformer having a magnetic core of a magnetic material. one of the main factors for the reduction. The iron loss was measured by filling a ring-shaped mold (outer diameter: 13.0 mm, inner diameter: 8.0 mm) with mixed powder mixed with epoxy resin and dispersed alloy powder, and after press molding, the resin was hardened to obtain a thickness of : 3.0mm toroidal core (dust core), 20 turns on the primary side and 20 turns on the secondary side to form a coil. For this coil, the iron loss was measured under the conditions of a magnetic flux density of 0.010 T and a frequency of 800 kHz using a BH analyzer (SY-8218 manufactured by Iwatsu Keiki Co., Ltd.). The iron loss of the powder compact of the present invention is 200 kW/m ³ or less. More preferably, it is 150 kW/m ³ or less. Example

Hereinafter, the present invention will be further described based on Examples. However, the present invention is not limited only by the examples described below.

Alloy powders of the compositions shown in Table 2 were produced.

As raw materials, Ni chloride and Fe chloride were prepared, respectively. Then, Ni chloride was first vaporized at 1000°C in the reaction apparatus. It reacts with hydrogen gas to produce Ni fine particles that become nuclei. Furthermore, chloride gas obtained by vaporizing Fe chloride at 1000° C. was introduced into it, reacted with hydrogen gas, and Fe was precipitated and grown on the surface of Ni particles, and finally, in the latter stage of the reaction apparatus. , and at 1100°C for 5 to 10 seconds, the composite particles are subjected to solution treatment, cooled and recovered. Next, with respect to the obtained various alloy powders, a dechlorination step of washing with pure water was performed to adjust the chlorine content.

With respect to the obtained various alloy powders, magnetic properties, rust resistance, and iron loss were investigated. The investigation method is as follows. (1) Magnetic properties About the obtained various alloy powders, the coercive force and saturation magnetization were measured using the vibrating sample type magnetometer (made by Toei Industrial Co., Ltd.). (2) Rust resistance After the obtained various alloy powders were embedded in resin and fixed, the cross-section was mirror-polished to form a test piece for rust resistance measurement. 20 are selected from the ground, observe whether there is rust, and calculate the proportion of rust particles. Moreover, the constant temperature and humidity tank is maintained under the conditions of temperature: 60°C and relative humidity: 95%. In addition, the holding time in a constant temperature and humidity tank was made into 2000 hours. (3) Iron loss The obtained various alloy powders were mixed with resin (epoxy resin) at the powder volume ratio shown in Table 2 and dispersed to obtain various mixed powders. These mixed powders were filled in a ring-shaped mold (outer diameter: 13 mm, inner diameter: 8 mm), and after pressure molding, the resin was hardened to manufacture a ring-shaped magnetic core with a thickness of 3 mm. The obtained magnetic core was wound with 20 turns on the primary side and 20 turns on the secondary side, and was measured using a B-H analyzer (SY-8218, manufactured by Iwatsu Instrument Co., Ltd.) under the conditions of a magnetic flux density of 10 mT and a frequency of 800 kHz. Iron loss (core loss). (4) Average particle size and average crystallite size The obtained alloy powder was observed and photographed by SEM, and the D50 based on the number obtained by SEM image analysis with a magnification of 20,000 times and the measured particle number of 1000 to 2000 was taken as the average particle size. In addition, the average crystallite diameter is measured according to the aforementioned "JIS H 7805". (5) Ni concentration in each particle (intra-particle homogeneity index) The Ni concentration at an arbitrary point in each particle constituting the alloy powder is obtained by embedding the powder in resin, cutting the cross section of the arbitrary particle with a focused ion beam (FIB) processing device, and using an energy dispersive X It was analyzed and measured by radiation analysis method (EDX). However, the Ni concentration at any point within the range from the center of each particle to 0.9 times the particle radius was obtained, and the minimum and maximum values were extracted. In addition, the average Ni content of the entire particle was EDX. The beam diameter and particle diameter are consistent with the measurement. The ratio of the extracted minimum value and maximum value to the measured average Ni content ratio was obtained.

Table 2 summarizes the results obtained above.

The 1st Gr in Table 2 is data with a low Cl content, the powder volume ratio is poor, and the iron loss increases. The second Gr is data for changing the Ni content, and when the Ni content is outside the appropriate range, the coercive force is poor, and the iron loss also increases. The third Gr is the data for making the Cl content rate, and when it is outside the appropriate range, the powder volume rate is poor, and the iron loss is also increased. The fourth Gr is data for changing the homogeneity index of the particles. When the solution treatment temperature is in an appropriate range, the minimum value and the maximum value of the ratio of the Ni concentration to the average Ni content rate are within an appropriate range, and the magnetic properties and the like are improved. The 5th Gr is the data of changing the average crystallite size by changing the reduction temperature. When the reduction temperature is not within the proper range, the average crystallite size is small and the compositional homogeneity is poor, so the magnetic properties are deteriorated. The last 6th Gr is the data of changing the average particle size, and if it is outside the suitable range, the magnetic properties such as iron loss will be deteriorated. In addition, in the table, for example, "100<" means "more than 100".

In each data, the data described in the examples are all alloy powder with low coercive force below 10Oe, high saturation magnetization above 130emu/g, and excellent rust resistance, and when it is used as a powder magnetic core, it can be produced Significant effect of powder cores with low core loss with iron loss of 150kW/m ³ or less.

On the other hand, the data described in the comparative examples outside the scope of the present invention are the alloy powder whose coercive force exceeds 20Oe, or the saturation magnetization is less than 130emu/g, or the alloy powder whose rust resistance is lowered, is used as a dust core. , it becomes a powder core with high core loss with iron loss exceeding 300kW/m ³ .

As described above, the present invention provides a technique for producing fine particles with an average particle size of 1 μm or less of an alloy known as permalloy B by CVD method, which has a size of 100,000 which is very different from iron-based soft magnetic materials. The maximum permeability and saturation flux density of 1.5T about 2 times larger than that of Permalloy C.

[ Fig. 1 ] A graph showing the Ni concentration distribution of Example 1 of the present invention in an experiment related to Ni concentration homogeneity. [ Fig. 2] Fig. 2 is a graph showing the distribution of Ni concentration in Conventional Example 1 in the experiment concerning the homogeneity of Ni concentration.

Claims (15)

A soft magnetic alloy powder, which is based on mass concentration, contains Ni: 40.0~50.0% and Cl: 10~10000ppm, and the remainder is composed of Fe and inevitable impurities. The alloy powder is characterized in that: the alloy powder The average particle size is 0.10-2.00 μm, and the average crystallite size is 0.5 times or more of the aforementioned average particle size. The soft magnetic alloy powder according to claim 1, wherein in the alloy powder, the Ni concentration at any point in the particle within the range from the center of the particle to 0.9 times the radius of the particle is the average of the entire particle Ni content rate is 0.7~1.3 times. The soft magnetic alloy powder according to claim 1 or 2, wherein the coercive force of the aforementioned alloy powder is 15 Oe or less. The soft magnetic alloy powder according to any one of claims 1 to 3, wherein the saturation magnetization of the alloy powder is 130 emu/g or more. The powder compact according to any one of claims 1 to 4, characterized by being a combination of the soft magnetic alloy powder and resin. The powder compact according to claim 5, wherein the resin is a thermosetting resin, an ultraviolet curing resin or a thermoplastic resin. A method for producing a soft magnetic alloy powder, characterized in that an alloy powder is generated by a chemical vapor method. The aforementioned alloy powder is based on mass concentration, and contains Ni: 40.0-50.0% and Cl: 10-10000 ppm, and the remaining part is composed of Fe. And the alloy powder composed of unavoidable impurities, the average particle size of the alloy powder is 0.10~2.00μm, and the average crystallite size is more than 0.5 times of the aforementioned average particle size. The method for producing a soft magnetic alloy powder according to claim 7, wherein in the alloy powder, the Ni concentration at any point in the particle within the range from the center of the particle to 0.9 times the radius of the particle is the particle The overall average Ni content is 0.7 to 1.3 times. The method for producing a soft magnetic alloy powder according to claim 7 or 8, wherein the chemical vapor method reduces Ni chloride to form Ni particles, and a reduction reaction of Fe chloride is carried out on the surface of the Ni particles to form the Ni particles. A method of obtaining alloy particles having a uniform composition within the particles by performing solution treatment in a temperature range in which γNi-Fe solid solution single phase is formed after the composite particles serving as cores are coated with Fe on the surface. The method for producing a soft magnetic alloy powder according to claim 9, wherein the temperature of the reduction reaction is 800 to 1100°C, and the temperature of the solution treatment is 900 to 1300°C. A method for producing a powder compact, characterized by generating soft magnetic alloy powder by chemical vapor method, mixing resin in the soft magnetic alloy powder, and performing compression molding, wherein the soft magnetic alloy powder is measured by mass concentration, Alloy powder containing Ni: 40.0~50.0% and Cl: 10~10000ppm, the remainder is composed of Fe and inevitable impurities, the average particle size of the alloy powder is 0.10~2.00μm, and the average crystallite size is the above average More than 0.5 times the particle size. The method for producing a powder compact according to claim 11, wherein in the alloy powder, the Ni concentration at any point in the particle within the range from the center of the particle to 0.9 times the radius of the particle is the entire particle The average Ni content rate of 0.7~1.3 times. The method for producing a powder compact according to claim 11 or 12, wherein the chemical vapor method reduces Ni chloride to form Ni particles, and a reduction reaction of Fe chloride is carried out on the surface of the Ni particles to form the Ni particles as the A method of obtaining alloy particles with a uniform composition within the particles by performing solution treatment in a temperature range where γNi-Fe solid solution single phase is formed after the core and the composite particles on the surface are coated with Fe. The method for producing a pressed powder according to claim 13, wherein the temperature of the reduction reaction is 800 to 1100°C, and the temperature of the solution treatment is 900 to 1300°C. The method for producing a powder compact according to any one of claims 11 to 14, wherein the resin is a thermosetting resin, an ultraviolet-curable resin, or a thermoplastic resin.

Images