JPH02290902A - Flaky fe-ni series alloy fine powder and manufacture thereof - Google Patents

Abstract

PURPOSE:To efficiently manufacture flaky soft magnetic fine powder having <=240A/m coercive force by mechanically pulverizing raw material powder with saturation magnetostriction constant and contents of Si and Al specified into the specific particle diameter and thickness. CONSTITUTION:Molten Fe-Ni series alloy having + or -15X10<-6> saturation magnetostriction constant measured with a bulk material and adding >=0.3% Si and >=0.05% Al, is atomized with water atomizing method to obtain the irregular shaped alloy powder. This alloy powder is mechanically pulverized as the raw material to 0.1-20mu average particle diameter and <=1mu average thickness and annealing is applied while keeping the flaky shape of the fine powder after pulverizing to make <=240A/m coercive force. The above Si and Al show improving effects of pulverization ability for raw material and soft magnetization and the improving effect of pulverization ability are not shown unless these elements are added more than the lower limits, and the soft magnetization is improved as increasing these elements, but when these elements are added too much, oxidation of the powder at the time of atomizing progresses greatly, therefor, the contents are practically limited to 3% Si and 1% Al.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to particles with an average particle size of 0.1 to 20 μm and an average thickness of 1 μm.
The present invention relates to the following flat alloy fine powder with excellent soft magnetism and a method for producing the same.

[Conventional technology]

In recent years, in the field of magnetic cards related to personal confidentiality, such as bank cards and credit cards, there has been an increasing need to coat the card surface with a coating film made of fine powder of a high magnetic permeability material for the purpose of magnetic shielding. . Such a coating powder is required to have high magnetic permeability, be a fine powder, and have a flat powder shape. This is not only necessary for ease of application and surface smoothness of the coating film, but also because the shearing force during application causes the flat fine powder to move in the flat direction where the demagnetizing field coefficient is lowest, that is, toward the card substrate. This is essential because high magnetic permeability in the in-plane longitudinal direction can be obtained by arranging them in parallel.

The specific characteristics of the powder required for this application include an average particle size of 0.1 to 20 μm, a thickness of 1 μm or less, and a coercive force of 240 μm in a random aggregation state ignoring the demagnetizing field.
It is less than A/m. The thickness of the powder is determined by embedding the powder in a resin powder and solidifying it while oriented in a flat direction in a magnetic field, and then examining the cross section of the embedded sample using a microscope.

As such a powder, Fe--Ni thread alloy, which has a high magnetic permeability and is easily plastically deformed and flattened, may be used. However, there is no disclosure of a powder having a coercive force of 240 A/m or less in terms of the powder specifications for Fe--Ni alloys and a method for obtaining the powder.

JP-A-63-357ol and JP-A-63-3570
For No. 6, the thickness is 2 μm or less, and the ratio of thickness to diameter is l/1.
It has been proposed to produce scale-like high magnetic permeability metal powder made of a pure metal or alloy material with a magnetic permeability of 0 or less using a wet ball milling method. Specifically, pure iron powder passed through a 44 μm sieve has been proposed. was ground for 96 hours to produce a scaly powder with a wall thickness of 1.0 μm that passed 98% through a 25 μm sieve, and Sendust alloy powder that passed through a 44 μm sieve was ground for 96 hours and passed through a 25 μm sieve. Wall thickness that passes 96% 1.
A scaly powder with a size of 0 to 1.5 μm is obtained. This method is
Although it is certainly possible to obtain magnetic material powder with a thickness of 2 μm or less, it requires grinding for as long as 96 hours, and it is difficult to obtain fine powder with an average particle size of 20 μI or less at a high yield. In addition, the coercive force of the obtained powder is significantly deteriorated due to crushing strain, and the coercive force 11c is high. It has been reported that the pure Fe powder has a power of 430e (3440A/m), and the Sendust alloy powder has a power of 90e (720A/m).

Regarding the Fe-Ni alloy, that is, permalloy flat fine powder, we could not find any specific information about it, and the inventor of the present invention filed a patent application in 1983-
No. 123494, average particle size 1 by water atomization
We proposed a method of mechanically pulverizing Fe-Ni alloy powder of 0 μII1 or less to obtain flat fine powder with an average particle size of 0.1 to 10 μm and a thickness of 1 μm or less. That is, here,
Fe-Ni alloys have high plastic deformability, are easily stretched, and are relatively easy to flatten, but are difficult to pulverize.
It was pointed out that reducing the particle size of the initial powder is important in terms of grinding efficiency. By the method proposed above, Fe
Although it becomes easier to flatten the -Ni alloy into a flat powder, reducing the particle size of the initial powder cannot be considered a mass-production method from the point of view of atomization. In other words, the water atomization method is the most mass-producible atomization process and is the easiest to reduce the particle size, but for average particle diameters of 10 μm or less, the molten metal must be sprayed at a water pressure of 1000'Kgf/1 or more. Therefore, installation of high-pressure supply pumps, equipment costs such as piping are enormous, maintenance is complicated, and the molten metal beam diameter has to be narrowed down to a few φ, so the amount of hot water delivered per unit time is small. There are problems such as difficulty in obtaining a yield of <10 μm or less, and the method of the above-mentioned Japanese Patent Application No. 63-123-494 has a limited mass productivity when considered from the raw material powder as a whole. It's a situation.

[Problem to be solved by the invention]

The present invention has been made in consideration of the problems of the prior art, and has an average particle diameter of 0, 1 to 20 μI, and an average thickness of 1 μI.
The present invention provides a flat Fe--Nt alloy fine powder having a coercive force Hc of 24 OA/10 or less, and a method for mass-producing the powder.

[Means for resolving levy]

That is, the present invention provides F e-N i with a saturation magnetostriction constant λs measured in bulk material within ±15×104 and containing 0.3% or more of Si and/or 0.05% or more of Al.
Flat-shaped Fe-Ni with an average particle size of 0.1 to 20, cLm, an average thickness of 1 μm or less, and a coercive force Hc of 240 A/m or less, obtained by mechanically pulverizing a base alloy fine powder as a raw material powder.
After the fine alloy powder and the Fe-Ni alloy having the above composition are made into irregularly shaped alloy powder by water atomization, the raw material powder is mechanically pulverized to obtain an average particle size of 0.1 to 20.
µm, an average thickness of 1 µm or less, and annealing while maintaining the shape of the flat fine powder after pulverization to make the coercive force Hc 24 OA/m or less. This is a method for producing e-Ni alloy fine powder.

Further, as one embodiment of the method of the present invention, prior to mechanical pulverization, the powder to be pulverized is subjected to heat treatment in an atmosphere having a suppressed oxygen potential, and the mechanical pulverization is performed using an attritor as a high-energy ball mill. and mechanical grinding in the presence of a grinding aid.

[Effect]

In the present invention, the desired powder shape and properties are achieved, namely, an average particle size of 0.1 to 20 μm, a wall thickness of 1 μm or less, and a coercive force H.
The present inventors have discovered a method for mass-producing flat Fe-Ni alloy fine powder having c of 240 A/m or less. First, the saturation magnetostriction measured in bulk material is 0.3% or more of Si and or A is added to the Fe-Ni composition such that the constant λs is within ±15
An alloy to which 0.05% or more of l is added is pulverized by water atomization, and then subjected to mechanical pulverization.

Here, the base composition of the Fe-Ni alloy whose saturation magnetostriction constant λs is within ±15X10 is defined as FeNi. A high magnetic permeability alloy (so-called PA permalloy) with a composition in the area where an ordered lattice is formed, as well as Fe-Ni, which suppresses the ordered lattice and can achieve high magnetic permeability even by slow cooling.
This category includes multi-element permalloy (PC permalloy) in which Mo, Cr, Cu, Nb, Mn, etc. are added to the system. It is known that these PA-based or PC-based permalloys have high magnetic permeability due to their saturation magnetostriction constant being zero or close to zero, and their magnetic anisotropy constant K1 being close to zero. The target flat fine powder obtained by pulverization has a saturation magnetostriction constant of ±15 x 10"
If it is within the range, significant residual strain due to crushing will be released by subsequent annealing, and the target coercive force Hc will reach 24
It was found that it was 0 A/m or less.

In this case, the saturation magnetostriction constant is difficult to measure with the flat powder with a wall thickness of 1 μm or less, which is the object of the present invention, and is represented by a value measured with a plate material having a thickness of more than the valence order.

In order to improve the crushability and soft magnetism of the Fe-Ni thread alloy powder so that the saturation magnetostriction constant λs is within ±15
It was found that powders added at % or more were effective. Si,A
L is dissolved as a solid solution in the Ni-enriched Fe-Ni yarn, which is the main composition, to the order of several percent, but as is generally observed in ingot bulk materials, the higher the amount added to the powder, the lower the toughness; It is more easily pulverized than ordinary Fe--Ni alloys to which no elements are added, and has the effect of improving the soft magnetic properties of the flat fine powder.

Furthermore, in order to improve the pulverization efficiency, it is effective to heat the raw material powder in an atmosphere with suppressed oxygen potential prior to pulverization, and although the cause of this is not clear, St. It is believed that selective grain boundary oxidation occurs due to the presence of Al. For example, when preheating is performed at 600°C in wet hydrogen as the pre-pulverization heating atmosphere,
The pulverization efficiency is improved compared to the case of no heat treatment and the case of heating in dry hydrogen. The atmosphere is not limited to wet hydrogen, and may be any weakly oxidizing atmosphere containing oxygen potential, such as nitrogen, inert gas such as Ar, NH, decomposed gas, etc., and is not particularly limited. The temperature may be within a range where the powder to be pulverized begins to agglomerate, but if it exceeds 1000°C, a sintered body with a relative density exceeding 70% will be produced, which will actually reduce the pulverization efficiency, so it is not preferable. .

Regarding the content of Si and Al, regardless of the presence or absence of heat treatment prior to the pulverization, from the viewpoint of improving pulverization efficiency, it is completely unnecessary to add at least 0.3% or more of Si or 0.05% or more of Al. SiO. Visible insteps on the order of 1-0.2% are not acceptable.

In addition, as the content of Si and Al increases, it improves the soft magnetic properties, and specifically reduces the coercive force Hc of the crushed flat fine powder, but if the content is too high, the Because oxidation becomes significant, Si is 3%, Al
The practical limit is 1%.

Furthermore, the faster the solidification rate during atomization, the smaller the crystal grain size of the powder, and therefore the easier the pulverization progresses. Therefore, as the atomization method, the water atomization method with a high cooling rate is most suitable. Furthermore, according to water atomization, the molten metal is solidified in an irregular shape with a disordered interface due to the shearing force of the water of the spray medium, so that it is easier to crush in shape compared to, for example, spherical powder such as gas atomization.

For mechanical pulverization, a stamp mill, a vibration mill, an attritor, etc. can be applied, but in the case of the Fe-Ni alloy powder added with 0.3% SL and/or 0.05% Al of the present invention, the above-mentioned pulverizer is used. By using the attritor with the highest input energy, it is possible to obtain flat powder with a target particle size and thickness within 10 hours with a yield of approximately 100%. Ordinary Fe-Ni without adding the above elements
In order to reduce the average thickness of the alloy powder to 1 μm or less after crushing, it is necessary to crush the powder for a long time, exceeding 10 hours.

The above is a case using an attritor, and in crushers such as stamp mills and vibration mills that require lower input energy, the time factor shifts to the longer time side as a whole, but the tendency is the same.

Flattening can be further promoted by performing the mechanical crushing in the presence of a suitable crushing aid.

The effectiveness of grinding aids is known, for example, in Japanese Patent Application No. 61-26213.
As exemplified in the case of amorphous alloy flakes in No. 4, the Fe-Ni of the present invention has the effect of adsorbing to the surface of activated powder particles as pulverization progresses, suppressing agglomeration of particles, and promoting flattening. It was also observed in alloys.

Effective solid aids include stearic acid, oleic acid,
Higher fatty acids such as lauric acid and palmitic acid, metal soaps such as zinc stearate, calcium stearate, zinc laurate, and aluminum laurate, higher aliphatic alcohols such as stearyl alcohol, and high M fatty acid amines such as ethanolamine and stearylamine. , polyethylene wax, etc. These may be used alone or in combination of two or more. The amount added is usually 0.1-500
Weight%. Furthermore, organic solvents such as alcohol, glycol, and ester can also be used as liquid auxiliaries.

The present invention will be explained in detail below with reference to Examples.

〔Example〕

Example 1 Molten metals of various Fe-NL alloys shown in the Example 1 column of Table 1 were water atomized to obtain powders with an average particle size of 29 to 37 μm.

These powders are pulverized with an attritor, and then H
, annealed in an air flow to reduce the coercive force Hc. Attritor pulverization was carried out by setting the weight ratio of SUJ 2 steel balls and water atomized powder to 3:1, adding ethanol as a grinding aid in the same weight as the water atomized powder, and pulverizing at 300 revolutions per minute. While sampling every 5 hours, the average thickness was 1μ.
When the particle size became less than m, the grinding was stopped, and the particles were sieved through a 350 mesh, and the yield of -350 mesh and its average particle size were measured. Also, 600℃X in a hydrogen atmosphere with a dew point of -60℃
Annealing was performed for lhr, and the coercive force 11c was measured. The shape of the flat fine powder before and after annealing was compared, and it was confirmed that there was no change in shape due to annealing.

In the column of Example 1 in Table 1, the main components of the sample material excluding unavoidable impurities, the saturation magnetostriction constant λs measured in the melted bulk material, the time required for pulverization to reach an average thickness of 1 μm, −
The yield of 350 mesh, the average particle size at -350 mesh, and the coercive force 11c of flat fine powder after annealing are shown.

From the perspective of the saturation magnetostriction constant λs, if it is within ±15×10″, even if there are various differences in the average grain size, the H after annealing
It can be seen that c can be obtained below the target of 240 A/m, and that with the same alloy base, the higher SL and Al are, the more Hc can be reduced.

From the viewpoint of pulverization efficiency, in the composition of the present invention containing 0.3% or more of Si and/or 0.05% or more of Al, 15 hours is sufficient under the present pulverization conditions; -350mes
It can be seen that the yield of h exceeds 70% and the average particle size is 20 μm or less. In particular, for alloys with equivalent λs, the difference in crushability and Hc between the composition of the present invention and the usual Fe-Ni alloy composition is remarkable.

Example 2 In exactly the same way as Example 1, No. 2 of the present invention was used. 14 and no. 1
The water atomized powder having the composition No. 8 was ground. These powders were prepared at 70°C in wet hydrogen with a dew point of 30°C prior to attritor grinding.
Heat treatment was performed at 0°C x 1hr. Through this treatment, the powder becomes
It became a lump that could be loosened by hand. The apparent particle size is approximately 3
00 μm.

When the above aggregate powder was pulverized using an attritor under the same conditions as in Example 1, the results of Example 2 in Table 1 were obtained. That is, compared to Example 1 in which the heat treatment was not performed, N
o. 14, the average thickness is 1 μm or less, but 15 → 10
hr, the yield of Katsu-350mesh improved by 7%, and the average particle size achieved decreased from 16 to 11 μm. No. 1
In No. 8, the yield of -350mesh increased by 8%, and the achieved average particle size decreased from 10 to 4 μm. Note that Hc after annealing is at the same level as when no heat treatment is performed, that is,
110 and LOOA/m, respectively.

〔Effect of the invention〕

As shown in the examples above, Si0.
Fe containing 3% or more and or Al 0.05% or more
- By subjecting the Ni-based alloy powder to pulverization, or further heat-treating the powder in an atmosphere with suppressed oxygen potential prior to pulverization, the average particle size is 0.
．． 1 to 20 μm, average thickness 1 μm or less, and coercive force H
Flat soft magnetic fine powder with c of 240 A/m or less can be efficiently produced, and its industrial value is great.

Claims (1)

[Claims] 1. The saturation magnetostriction constant λs measured in bulk material is ±15×
Within 10^-^6, Si0.3% or more and or A
An average particle size of 0.1 to 20 μm and an average thickness of 1 μm obtained by mechanically pulverizing raw material powder containing 0.05% or more of l.
Hereinafter, a flat Fe-Ni alloy fine powder characterized in that the coercive force Hc is 240 A/m or less. 2. A method for producing a flat Fe-Ni alloy fine powder according to claim 1, wherein molten alloy is atomized by a water atomization method, and the irregularly shaped alloy powder obtained is used as a raw material for mechanical processing. The average particle size is 0.1 to 20 μm.
Flat Fe-Ni characterized by comprising a step of reducing the average thickness to 1 μm or less, and a step of annealing the flat fine powder while maintaining its shape after pulverization, and reducing the coercive force Hc to 240 A/m or less. A method for producing alloy fine powder. 3. The flat Fe-Ni alloy according to claim 2, wherein, prior to mechanical pulverization, the raw material powder to be pulverized is subjected to heat treatment in an atmosphere having a suppressed oxygen potential. Method for producing fine powder. 4 Claim 2 of pulverizing using an attritor
A method for producing a flat Fe-Ni alloy fine powder according to item 1 or 3. 5. Flat Fe according to claim 2, 3, or 4, which is mechanically pulverized in the coexistence of a pulverizing aid.
- A method for producing Ni-based alloy fine powder.