JP7148876B2 - Amorphous alloy ribbon, amorphous alloy powder, nanocrystalline alloy dust core, and method for producing nanocrystalline alloy dust core - Google Patents

Description

The present invention provides, for example, PFC circuits used in home appliances such as televisions and air conditioners, nanocrystalline alloy powder magnetic cores used in power circuits such as solar power generation, hybrid vehicles, and electric vehicles, and the nanocrystals The present invention relates to a method for manufacturing an alloy dust core, and an amorphous alloy ribbon and an amorphous alloy powder as materials for the nanocrystalline alloy dust core.

As a soft magnetic material used for various transformers, motors, generators, reactors, choke coils, noise countermeasure parts, laser power supplies, pulse power magnetic parts for accelerators, various sensors, magnetic shields and yokes for magnetic circuits, Fe-based nano Crystalline alloys are known. Fe-based nanocrystalline alloys are known to have small coercive force and magnetostriction comparable to Co-based amorphous alloys, and exhibit high saturation magnetic flux densities comparable to Fe-based amorphous alloys. This Fe-based nanocrystalline alloy is usually produced by quenching from a liquid phase or gas phase to form an amorphous alloy, and then microcrystallizing this by heat treatment. As a method of quenching from the liquid phase, a single roll method, a twin roll method, a centrifugal quenching method, a spinning method in a rotating liquid, an atomization method, a cavitation method, and the like are known. Also, as a method of quenching from the gas phase, a sputtering method, a vapor deposition method, an ion plating method, and the like are known.

The Fe-based nanocrystalline alloy is a micro-crystallized amorphous alloy produced by these methods, and has almost no thermal instability seen in amorphous alloys, and has a saturation magnetic flux density as high as that of Fe-based amorphous alloys. It is known to have low magnetostriction and exhibit excellent soft magnetic properties. Furthermore, nanocrystalline alloys are known to have little change over time and excellent temperature characteristics. The nanocrystalline alloy is obtained by heat-treating an amorphous alloy capable of nanocrystallization at a temperature equal to or higher than the nanocrystallization initiation temperature (hereinafter also simply referred to as "nanocrystallization heat treatment"). Hereinafter, an amorphous alloy capable of nanocrystallization before nanocrystallization heat treatment is also simply referred to as an “amorphous alloy”. Further, an Fe-based nanocrystalline alloy obtained by subjecting an amorphous alloy to nanocrystallization heat treatment is also simply referred to as a “nanocrystalline alloy”.

Amorphous alloys are generally produced by continuous casting into strips by roll quenching, and are produced as long alloy strips. Therefore, a magnetic core made of a nanocrystalline alloy is generally used in which an alloy ribbon is wound or laminated. However, in recent years, in electromagnetic booster circuits such as reactors, response to high frequency applications of several tens to hundreds of kHz is required due to needs such as miniaturization. The number of powder magnetic cores that have been processed is increasing. The reason why the powder magnetic core is used is as follows.

Magnetic cores used in high-frequency electromagnetic circuits are used with a reduced magnetic permeability in order to prevent magnetic saturation due to current fluctuations. In a powder magnetic core in which powdered magnetic material is solidified, a slight gap between powders plays a role of lowering magnetic permeability, so magnetic saturation is suppressed, and the loss of the entire circuit can be reduced.

In a high frequency range of several tens to several hundreds of kHz, a magnetic permeability of several tens to several hundreds is desired, so flat powder is easier to use than spherical powder. The reason for this is that when the in-plane direction of the flat powder is parallel to the magnetic path, the demagnetizing field coefficient in the direction of the magnetic path becomes relatively low, and shape magnetic anisotropy acts in the direction of the magnetic path. This is because it is easy to raise Amorphous alloy powder obtained by the atomization method has a nearly spherical shape, but it is an amorphous alloy obtained by pulverizing an amorphous alloy ribbon (hereinafter simply referred to as "amorphous alloy ribbon") manufactured by roll quenching and capable of nanocrystallization. Since the powder (hereinafter also simply referred to as "pulverized ribbon powder") is flattened, the use of this pulverized ribbon powder is being studied.

The amorphous alloy ribbon has hardness comparable to that of the Fe-based amorphous alloy ribbon. Therefore, it has the disadvantage of being difficult to pulverize and difficult to control the particle size after pulverization.

Since the amorphous alloy ribbon has excellent toughness before heat treatment, heat treatment for embrittlement of the alloy (hereinafter referred to as embrittlement heat treatment) is performed in order to pulverize it to produce pulverized ribbon powder. Although the toughness of the amorphous alloy ribbon is reduced by the embrittlement heat treatment, the amorphous alloy ribbon is pulverized while being torn, so stress tends to remain locally in the pulverized ribbon powder, which is one of the factors that deteriorates the magnetic properties. Become. In addition, embrittlement heat treatment becomes a bottleneck in the manufacturing process. In addition, when the pulverized ribbon powder subjected to the embrittlement heat treatment and the binder are compression-molded to form a powder magnetic core, the internal stress generated in the pressing process remains in the powder magnetic core, but the internal stress is relieved after that. Even if heat treatment (hereinafter referred to as strain relief heat treatment) is performed, it is difficult to sufficiently relax the stress, and sufficient soft magnetic properties cannot be obtained. The reason for this is that if the stress relief heat treatment of the amorphous alloy is repeatedly performed, the improvement effect is reduced, so if the embrittlement heat treatment is performed before pulverization, the stress relaxation due to the heat treatment after compression molding cannot be performed sufficiently. . Therefore, it is effective to develop an amorphous alloy ribbon having good pulverizability without performing embrittlement heat treatment.

For example, Patent Document 1 discloses a problem of crushing an amorphous soft magnetic alloy containing Fe, B, P, and Cu, which is difficult to crush, as it is without embrittlement heat treatment. represented by the formula _{FeaSibBcPxCuySnz} , _{79≤a≤86at} %, _0≤b≤10at %, _1≤c≤14at %, _1≤x≤15at %, _0.4≤ A soft magnetic alloy powder that satisfies y≦2 at%, 0.5≦z≦6 at%, and 0.04≦y/x≦1.20, wherein the soft magnetic alloy powder has an amorphous single phase. We are proposing an alloy powder.

In paragraph 0022 of the above-mentioned Patent Document 1, regarding improvement of pulverizability, "In the above soft magnetic alloy powder, Sn is an element responsible for forming an amorphous phase, and the content of Sn accelerates the quenching of the melted alloy. It is an essential element because it can be pulverized as it is without heat treatment for the amorphous alloy ribbons and flakes produced by the process.

In addition, Patent Document 2 describes that it is difficult to obtain a high saturation magnetic flux density of 1.7 T or more with Fe-based nanocrystalline materials such as FeCuNbSiB system and FeCuNbB system containing Nb at a few percent or more, and powder production _As a _{soft magnetic alloy} that _facilitates the .19).

Japanese Unexamined Patent Application Publication No. 2016-3366 Japanese Patent No. 5445888

However, further investigation is required to obtain an amorphous alloy ribbon capable of achieving both excellent grindability and soft magnetic properties.

Accordingly, an object of the present invention is to provide an amorphous alloy ribbon that has excellent pulverizability and can be subjected to a nanocrystallization heat treatment to obtain excellent soft magnetic properties, and an amorphous alloy ribbon obtained by pulverizing the amorphous alloy ribbon. An object of the present invention is to provide an alloy powder, and to provide a nanocrystalline alloy dust core produced using the alloy powder, and a method for producing a nanocrystalline alloy dust core.

Specific means for solving the above problems include the following aspects.
<1> Alloy composition: Fe _100-abc-d Cu _a Si _b B _c Sn _d (where a, b, c, and d are atomic % and 0.3 ≤ a < 1.55 , 1 ≤ b ≤ 10, 11 ≤ c ≤ 17, 0.25 < d ≤ 1.0, a + d ≤ 1.80),
Amorphous alloy ribbon.
<2> The amorphous alloy ribbon according to <1>, having a thickness of 15 μm or more and 50 μm or less.
<3> Alloy composition: Fe _100-abc-d Cu _a Si _b B _c Sn _d (where a, b, c, and d are atomic % and 0.3 ≤ a < 1.55 , 1 ≤ b ≤ 10, 11 ≤ c ≤ 17, 0.25 < d ≤ 1.0, a + d ≤ 1.80),
Having an alloy ribbon surface and a fracture surface,
Amorphous alloy powder.
<4> Alloy composition: Fe _100-abc-d Cu _a Si _b B _c Sn _d (where a, b, c, and d are atomic % and 0.3 ≤ a < 1.55 , 1 ≤ b ≤ 10, 11 ≤ c ≤ 17, 0.25 < d ≤ 1.0, a + d ≤ 1.80), and an amorphous alloy ribbon that has not been heat-treated is pulverized. a pulverization step of forming an amorphous alloy powder;
A compression molding step A in which the amorphous alloy powder and a binder are mixed and compression molded to form a green compact;
a crystallization heat treatment step A in which the green compact is subjected to heat treatment for nano-crystallizing the amorphous alloy powder contained in the green compact;
A method for producing a nanocrystalline alloy dust core having
<5> Alloy composition: Fe _100-abc-d Cu _a Si _b B _c Sn _d (where a, b, c, and d are atomic % and 0.3 ≤ a < 1.55 , 1 ≤ b ≤ 10, 11 ≤ c ≤ 17, 0.25 < d ≤ 1.0, a + d ≤ 1.80), and an amorphous alloy ribbon that has not been heat-treated is pulverized. a pulverization step of forming an amorphous alloy powder;
a crystallization heat treatment step B in which the amorphous alloy powder is subjected to a heat treatment for nanocrystallization to obtain a nanocrystalline alloy powder;
A compression molding step B in which the nanocrystallized nanocrystalline alloy powder and a binder are mixed and compression molded to form a green compact;
A method for producing a nanocrystalline alloy dust core having
<6> Alloy composition: Fe _100-abc-d Cu _a Si _b B _c Sn _d (where a, b, c, and d are atomic % and 0.3 ≤ a < 1.55 , 1 ≤ b ≤ 10, 11 ≤ c ≤ 17, 0.25 < d ≤ 1.0, a + d ≤ 1.80), and has a body-centered cubic structure with an average crystal grain size of 60 nm or less. A nanocrystalline alloy dust core containing an amorphous alloy powder having a structure in which crystal grains are dispersed in an amorphous matrix at a volume fraction of 30% by volume or more, and having an alloy ribbon surface and a fracture surface.

According to the present invention, an amorphous alloy ribbon having excellent pulverizability and capable of obtaining excellent soft magnetic properties by performing nanocrystallization heat treatment, an amorphous alloy powder obtained by pulverizing the amorphous alloy ribbon, and It is possible to provide a nanocrystalline alloy dust core manufactured using these materials and a method for manufacturing a nanocrystalline alloy dust core.

FIG. 4 is a graph showing the relationship between the Sn substitution amount x and the recovery rate of powder having a particle size of 106 μm or less. FIG. 4 is a graph showing the relationship between the Sn substitution amount x and the recovery rate of powder having a particle size of 63 μm or less. 4 is a photograph of the external appearance of pulverized ribbon powder of the present embodiment. 1 is a TEM photograph of pulverized ribbon powder of the present embodiment, which has been subjected to heat treatment for nanocrystallization. 1 is a TEM photograph of a pulverized ribbon powder of a comparative form subjected to heat treatment for nanocrystallization.

Next, the present invention will be specifically described by way of embodiments, but the present invention is not limited by these embodiments. In this specification, a numerical range represented by "-" means a range including the numerical values before and after "-" as lower and upper limits. In the numerical ranges described step by step in this specification, the upper limit or lower limit described in one numerical range may be replaced with the upper limit or lower limit of the numerical range described in other steps. . Moreover, in the numerical ranges described in this specification, the upper and lower limits of the numerical ranges may be replaced with the values shown in the examples.

<Amorphous alloy ribbon>
The amorphous alloy ribbon of this embodiment satisfies the following alloy composition.
Alloy composition: Fe _100-abc-d Cu _a Si _b B _c Sn _d (where a, b, c, and d are atomic %, 0.3 ≤ a < 1.55, 1 ≤ b≦10, 11≦c≦17, 0.25<d≦1.0, a+d≦1.80)

The amorphous alloy ribbon having the above alloy composition is excellent in pulverizability, and becomes a soft magnetic material capable of obtaining excellent soft magnetic properties (high saturation magnetic flux density) by performing nano-crystallization heat treatment.

The amorphous alloy ribbon in the present embodiment is produced by melting raw materials weighed so as to have the above alloy composition by means of high-frequency induction melting or the like, and then discharging the molten alloy through a nozzle onto the surface of a cooling roll rotating at high speed. It can be manufactured by roll quenching such as single roll or twin rolls. From the viewpoint of improving the production efficiency of the amorphous alloy ribbon by facilitating continuous casting, and from the viewpoint of intentionally causing embrittlement by slowing the cooling rate of the molten metal to improve pulverization, the pulverized ribbon powder is produced. From the viewpoint of improving production efficiency, the thickness of the amorphous alloy ribbon is preferably 15 μm or more. Moreover, the thickness of the amorphous alloy ribbon is preferably 50 μm or less from the viewpoint of improving pulverizability and improving the production efficiency of pulverized ribbon powder.

The amorphous alloy ribbon of the present embodiment includes not only a perfect strip but also a thin strip obtained by roll quenching. In addition, the strip-shaped strip refers to a strip that is partially torn or broken and separated into a plurality of strips. A method of casting an alloy strip by roll quenching such as single roll or twin roll is hereinafter referred to as "roll casting".

<Amorphous alloy powder>
In addition, the amorphous alloy powder of the present embodiment has an alloy composition: Fe _100-abc-d Cu _a Si _b B _c Sn _d (here, a, b, c, and d are atomic %, 0 .3 ≤ a < 1.55, 1 ≤ b ≤ 10, 11 ≤ c ≤ 17, 0.25 < d ≤ 1.0, a + d ≤ 1.80), and the alloy ribbon surface and a fracture surface. In addition, the alloy ribbon surface is a surface corresponding to both opposing planes of the amorphous alloy ribbon formed by roll casting.

This amorphous alloy powder becomes a nanocrystalline alloy powder having a high saturation magnetic flux density by subjecting it to a nanocrystallization heat treatment. Details will be described later.

The alloy composition of the amorphous alloy ribbon, amorphous alloy powder, and nanocrystalline alloy dust core of this embodiment will be described below.

The amorphous alloy ribbon, amorphous alloy powder, and nanocrystalline alloy dust core of the present embodiment have a composition in which Nb or Mo is not added, and have a high saturation magnetic flux density.

The alloy composition of the amorphous alloy ribbon and amorphous alloy powder of the present embodiment (hereinafter, the amorphous alloy ribbon and amorphous alloy powder of the present embodiment may be simply referred to as "amorphous alloy ribbon, etc.") is , a composition that allows nanocrystallization. In addition, the structure of the nanocrystalline alloy ribbon and the nanocrystalline alloy powder obtained by subjecting the amorphous alloy ribbon or the like of the present embodiment to nanocrystallization heat treatment has crystal grains having an average grain size of 30 nm or less in the amorphous matrix. It is preferable that the texture is more than 0% and less than 30% dispersed.

By subjecting the amorphous alloy ribbon or the like to nanocrystallization heat treatment, a nanocrystalline alloy ribbon or nanocrystalline alloy powder having a nanocrystalline structure in which nanocrystals having an average crystal grain size of 60 nm or less are dispersed in the amorphous phase is obtained. Obtainable. By subjecting the amorphous alloy ribbon or the like of the present embodiment to nanocrystallization heat treatment, the volume fraction of the nanocrystalline phase in the obtained nanocrystalline alloy ribbon or nanocrystalline alloy powder can be 30% or more. The nanocrystals are crystal grains having a body-centered cubic structure, and preferably have an average crystal grain size of 10 to 50 nm.

The alloy composition of the amorphous alloy ribbon will be described below.

Fe (iron) is an element that determines the saturation magnetic flux density Bs. In order to obtain a high saturation magnetic flux density Bs, the Fe atomic % in the alloy composition of the amorphous alloy ribbon is preferably 77 atomic % or more, more preferably 79 atomic % or more.

Cu (copper) has the effect of making the amorphous alloy ribbon brittle and facilitating pulverization. In the Fe—B amorphous matrix, Cu has a positive heat of mixing with those elements. Therefore, in order to lower the potential energy, Cu atoms gather together to form clusters during the cooling process during manufacturing. Since the Fe concentration increases around the cluster, a high-density region with a high Fe concentration is generated. It is speculated that this density variation facilitates pulverization. Moreover, the addition of Cu is essential because nanocrystals are uniformly generated in the alloy structure with Cu atoms as nuclei.

In order to obtain the above effects, the atomic % of Cu in the alloy composition of the amorphous alloy ribbon is 0.3 atomic % or more, preferably 0.5 atomic % or more, more preferably 0.7 atomic % or more, 0.8 atomic % or more is more preferable.

A nanocrystalline alloy powder that has excellent soft magnetic properties by suppressing the formation of relatively large crystals in amorphous alloy ribbons, etc., which grow into coarse crystal grains by heat treatment after rapid solidification (before nanocrystallization heat treatment). From the viewpoint of obtaining a magnetic core, and by increasing the amorphous phase that relaxes the residual stress in the nanocrystalline alloy ribbon or nanocrystalline alloy powder obtained by heat-treating the amorphous alloy ribbon or the like, a nanocrystalline alloy dust core is produced. From the viewpoint of improving soft magnetic properties, the Cu atomic% in the alloy composition of the amorphous alloy ribbon is less than 1.55 atomic%, preferably 1.4 atomic% or less, and more preferably 1.2 atomic% or less. Preferably, less than 1.0 atomic % is more preferable.

Si (silicon) is an element that forms an alloy with Fe as a nanocrystalline phase by heat treatment to form a bcc phase ((Fe—Si)bcc phase). Also, it is an element that acts on the ability to form an amorphous material during rapid solidification. The atomic % of Si in the alloy composition of the amorphous alloy ribbon is 1 atomic % or more, preferably 2 atomic % or more, and more preferably 2.5 atomic % or more in order to form an amorphous phase after rapid solidification with good reproducibility. preferable. On the other hand, in order to ensure the reproducibility of the viscosity of the molten alloy, the content is 10 atomic % or less, preferably 8 atomic % or less, and more preferably 7 atomic % or less.

B (boron), like Si, is an element that acts on the amorphous forming ability during rapid solidification. In addition, B has the effect of making the Cu atoms, which are the nuclei of the nanocrystals, uniformly exist in the alloy structure (in the amorphous phase) without being unevenly distributed.

The atomic % of B in the alloy composition of the amorphous alloy ribbon or the like is 11 atomic % or more in order to form an amorphous phase after rapid solidification with good reproducibility and uniformly exist Cu atoms in the amorphous phase. % or more is preferable. In addition, although it is related to the total amount with the Si amount described later, from the viewpoint of obtaining a nanocrystalline alloy dust core having a high saturation magnetic flux density Bs, the atomic % of B in the alloy composition is 17 atomic % or less, and 15 atomic %. 0.5 atomic % or less is preferable.

Moreover, as described above, Fe is an element that determines the saturation magnetic flux density Bs. Therefore, when the amount of Fe in the amorphous alloy ribbon or the like decreases, the saturation magnetic flux density Bs tends to decrease. Furthermore, regarding the saturation magnetic flux density Bs, Si and B have relatively large effects on Fe. Therefore, the sum (b + c) of Si atomic % and B atomic % in the alloy composition of the amorphous alloy ribbon or the like is 20 atomic % or less ( That is, b+c≦20) is preferable, and 18 atomic % or less (b+c≦18) is more preferable.

Sn (tin) has the effect of embrittlement of amorphous alloy ribbons and the like. In addition, when Sn is added in combination with Cu, the embrittlement of the amorphous alloy ribbon and the like becomes more pronounced. Sn, which has a low melting point, can move in the amorphous alloy ribbon or the like even at a relatively low temperature, and can be evenly distributed throughout the amorphous alloy ribbon or the like. In relation to the fact that Sn and Cu form a compound, it is believed that Sn has the effect of dispersing Cu(Sn) clusters at a higher number density and broadly throughout amorphous alloy ribbons and the like. Further, Sn has a function and effect of suppressing the formation of coarse crystal grains after heat treatment of amorphous alloy ribbons and the like.

In order to obtain these effects, the atomic % of Sn in the alloy composition of the amorphous alloy ribbon is more than 0.25 atomic %, preferably 0.26 atomic % or more, more preferably 0.27 atomic % or more, 0.28 atomic % or more is more preferable. On the other hand, from the viewpoint of suppressing the precipitation of compounds that reduce the soft magnetic properties, the Sn atomic% in the alloy composition of the amorphous alloy ribbon is 1.0 atomic% or less, preferably less than 0.50 atomic%. 0.48 atomic % or less is more preferable, and 0.45 atomic % or less is even more preferable.

The sum (a+d) of the amount of Cu and the amount of Sn in the alloy composition of the amorphous alloy ribbon or the like is set to 1.80 atomic % or less. If the total amount of Cu and Sn in the alloy composition is 1.80 atomic % or less, it is easy to obtain a nanocrystalline alloy ribbon or nanocrystalline alloy powder having a high saturation magnetic flux density. From the viewpoint of obtaining a nanocrystalline alloy ribbon or nanocrystalline alloy powder having a high saturation magnetic flux density, the total amount of Cu and Sn in the alloy composition of the amorphous alloy ribbon is preferably 1.6 atomic % or less, and 1.5 Atom % or less is more preferable, and 1.45 atomic % or less is even more preferable. The sum of the amount of Cu and the amount of Sn in the alloy composition of the amorphous alloy ribbon or the like is determined from the viewpoint of obtaining an amorphous alloy ribbon with excellent grindability, and from the viewpoint of obtaining a nanocrystalline alloy ribbon or nanocrystalline alloy powder having a high saturation magnetic flux density. , preferably 0.8 atomic % or more, more preferably 1.0 atomic % or more, still more preferably 1.2 atomic % or more, and even more preferably 1.25 atomic % or more.

The amorphous alloy ribbon or the like of the present embodiment preferably has fine crystal grains dispersed in the amorphous (matrix). In alloys with a large amount of Fe, it is better to produce an amorphous alloy in which fine crystal grains are dispersed in the amorphous (matrix) rather than to produce a complete amorphous alloy, and then heat treat to promote crystallization. It has a fine crystal grain structure and can realize excellent soft magnetic properties.

With the alloy composition specified in the present embodiment, it is easy to obtain an amorphous alloy ribbon or the like in which fine crystal grains are dispersed in the amorphous (matrix) by roll casting. The state in which fine crystal grains are dispersed means a state in which crystal grains with an average grain size of 30 nm or less are dispersed in the amorphous matrix at a volume fraction of more than 0% and less than 30%.

Fe—B and Fe—B—Si alloy compositions tend to form an amorphous phase. Fine crystal grain nuclei can be appropriately formed in the base alloy (intermediate alloy). In the amorphous alloy with this structure, fine crystal grains are formed at the stage before the nano-crystallization heat treatment, and an appropriate heat treatment does not cause the crystal grains to coarsen, so that a nano-crystalline alloy is obtained and has good soft magnetism. properties are obtained. In addition, since the fine crystal grains are randomly dispersed, the brittleness can be high enough to cause breakage by 180° bending. Therefore, pulverization is possible without using a powerful pulverizing means such as a milling device, and the resulting amorphous alloy powder has a small residual stress.

The alloy composition may contain impurities in addition to the indicated elements. Impurities include, for example, P (phosphorus), S (sulfur), N (nitrogen), C (carbon), and the like. This impurity can be substituted for Fe in a range of less than 1.0 atomic % within 100 atomic % of the above composition formula.

In particular, P is an element that acts on the ability to form an amorphous material during rapid solidification, but it can also be a factor that deteriorates the grindability. In order to ensure grindability, it is necessary to further add Sn, which has an embrittlement effect. However, since Sn is an element that degrades the soft magnetic properties, it is not preferable to add a large amount of Sn. Therefore, the upper limit of the atomic % of P in the alloy composition such as the amorphous alloy ribbon is preferably less than 1.0 atomic %, more preferably 0.5 atomic % or less, with the atomic % of the alloy composition being 100 atomic %. 0.3 atomic % or less is more preferable, 0.2 atomic % or less is still more preferable, and 0.1 atomic % or less is still more preferable.

Since C is effective in stabilizing the viscosity of the molten alloy during casting, even if the amorphous alloy ribbon or the like contains C in the range of 0.40 atomic % or less after setting P in the above range. good. The atomic % of C in the alloy composition of the amorphous alloy ribbon is preferably 0.37 atomic % or less, more preferably 0.35 atomic % or less. In addition, the atomic % of C in the alloy composition of the amorphous alloy ribbon is preferably 0.10 atomic % or more, more preferably 0.20 atomic % or more, from the viewpoint of stabilizing the viscosity of the molten alloy during casting. , more preferably 0.22 atomic % or more.

(Pulverization and classification)
Known means such as an atomizer, a ball mill, a jet mill, and a stamp mill can be employed for pulverizing the amorphous alloy ribbon having the above alloy composition. The pulverized powder of the obtained amorphous alloy ribbon has an alloy ribbon surface formed by roll casting and a fractured surface.

In this embodiment, the amorphous alloy powder having a desired average particle size can be obtained by performing classification after pulverization.

For example, the classified amorphous alloy powder can have a median diameter D50 (particle diameter corresponding to cumulative 50% by volume) of 20 μm or more and 40 μm or less. Specifically, the amorphous alloy powder is classified with a sieve, and the powder with a particle size of more than 40 μm is 10% by mass or less of the whole powder, and the powder with a particle size of more than 20 μm and 40 μm is 30% by mass or more of the whole powder. It is 90% by mass or less, and the powder having a particle size of 20 μm or less can be 5% by mass or more and 60% by mass or less of the entire powder.

According to this classification, it is preferable that the amorphous alloy powder having a particle size of more than 40 μm accounts for 10 mass % or less of the entire amorphous alloy powder. It is not easy to stably obtain an amorphous phase or a mixed phase of an amorphous phase and a microcrystalline phase from the amorphous alloy powder having a particle size of more than 40 μm. Therefore, the content of the amorphous alloy powder having a particle size of more than 40 μm is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 0% by mass.

As described above, it is preferable that the amount of amorphous alloy powder having a particle size of more than 40 μm is small. Then, among the remaining many amorphous alloy powders, the ratio of the amorphous alloy powder having a particle size of 20 μm or less and the amorphous alloy powder having a particle size of more than 20 μm and not more than 40 μm can be specified.

At this time, the Fe-based nanocrystalline alloy powder having a particle size of 20 μm or less can provide a Fe-based nanocrystalline alloy powder having a high saturation magnetic flux density Bs that can suppress magnetic saturation even in high-frequency applications. Amorphous alloy powder having a particle size of is suitable for a magnetic core having a high initial magnetic permeability μi and excellent DC superimposition characteristics. Therefore, these amounts can be set to obtain the desired magnetic properties.

In the above, the amorphous alloy powder with a particle size of more than 20 μm and 40 μm or less accounts for 30% by mass or more and 90% by mass or less of the entire amorphous alloy powder, and the amorphous alloy powder with a particle size of 20 μm or less accounts for 5% by mass or more and 60% by mass of the entire amorphous alloy powder. % by mass or less. As noted above, the amount can be varied depending on the desired magnetic properties.

The amorphous alloy powder having a particle size of 20 μm or less is preferably 10% by mass or more, more preferably 20% by mass or more, preferably 50% by mass or less, and more preferably 40% by mass or less in the entire amorphous alloy powder. The amorphous alloy powder having a particle size of more than 20 μm and 40 μm or less is preferably 35% by mass or more, more preferably 40% by mass or more, preferably 85% by mass or less, and more preferably 80% by mass or less in the entire amorphous alloy powder.

<Nanocrystalline alloy dust core>
The method for manufacturing the nanocrystalline alloy dust core of the first embodiment using the above amorphous alloy powder includes:
Alloy composition: Fe _100-abc-d Cu _a Si _b B _c Sn _d (where a, b, c, and d are atomic %, 0.3 ≤ a < 1.55, 1 ≤ b ≤ 10, 11 ≤ c ≤ 17, 0.25 < d ≤ 1.0, a + d ≤ 1.80). A pulverization step into powder;
A compression molding step A in which the amorphous alloy powder and a binder are mixed and compression molded to form a green compact;
a crystallization heat treatment step A in which the green compact is subjected to heat treatment for nano-crystallizing the amorphous alloy powder contained in the green compact;
It has

In addition, the method for manufacturing the nanocrystalline alloy dust core of the second embodiment using the above amorphous alloy powder includes:
Alloy composition: Fe _100-abc-d Cu _a Si _b B _c Sn _d (where a, b, c, and d are atomic %, 0.3 ≤ a < 1.55, 1 ≤ b ≤ 10, 11 ≤ c ≤ 17, 0.25 < d ≤ 1.0, a + d ≤ 1.80). A pulverization step into powder;
a crystallization heat treatment step B in which the amorphous alloy powder is subjected to a nanocrystallization heat treatment to obtain a nanocrystalline alloy powder;
A compression molding step B in which the nanocrystallized nanocrystalline alloy powder and a binder are mixed and compression molded to form a green compact;
It has

The heat treatment in the pulverization step of the method for producing the nanocrystalline alloy dust core of the first and second embodiments described above refers to embrittlement heat treatment and nanocrystallization heat treatment. A temperature heat treatment corresponds. The embrittlement heat treatment is preferably performed at 250° C. or higher.

According to the method of manufacturing the nanocrystalline alloy dust core of the first and second embodiments, since the amorphous alloy ribbon before pulverization is not subjected to embrittlement heat treatment or nanocrystallization heat treatment, the crystallization heat treatment step is performed. When nano-crystallization heat treatment is applied to the amorphous alloy powder or powder compact in A or the crystallization heat treatment step B, stress is sufficiently relaxed, and a powder magnetic core having excellent soft magnetic properties such as saturation magnetic flux density can be obtained. .

According to the method for manufacturing the nanocrystalline alloy dust core of the first embodiment (embodiment in which the powder compact is subjected to nanocrystallization heat treatment), the nanocrystallization heat treatment causes the amorphous alloy powder to nanocrystallize and , integration by hardening the binder and stress relaxation of the compressive strain imparted to the amorphous alloy powder can be performed simultaneously.

According to the method for producing a nanocrystalline alloy dust core of the second embodiment (embodiment in which the amorphous alloy powder is subjected to nanocrystallization heat treatment), the nanocrystallization heat treatment causes the amorphous alloy powder to nanocrystallize. , stress relaxation of the compressive strain applied to the amorphous alloy powder can be simultaneously performed.

In the method for producing the nanocrystalline alloy powder magnetic core of the first embodiment and the method for producing the nanocrystalline alloy powder magnetic core of the second embodiment, after obtaining a powder compact, the powder compact is A heat treatment step for hardening the contained binder and a heat treatment step for performing strain relief heat treatment on the green compact may be provided.

By the above method, the amorphous alloy ribbon can be pulverized to obtain an amorphous alloy powder, and the amorphous alloy powder classified as necessary can be obtained. Using this amorphous alloy powder, a nanocrystalline alloy dust core can be produced by the following production method.

Amorphous alloy powder, a binder such as silicone resin, and if necessary, an organic solvent are added and kneaded. When an organic solvent is used in compression molding, the organic solvent is evaporated thereafter. Moreover, granulation can also be performed after kneading. The kneaded material is placed in a press mold and compression-molded into a desired magnetic core shape such as a toroidal shape to obtain a powder compact. At this time, the nano-crystallization heat treatment is applied to the amorphous alloy powder or to the powder compact.

If the nanocrystallization heat treatment is applied to the amorphous alloy powder, the green compact can also be subjected to heat treatment to harden the binder.

Further, when the nano-crystallization heat treatment is applied to the powder compact, heat treatment for hardening the binder can also be applied at the same time.

<Nano-crystallization heat treatment>
The nano-crystallization heat treatment will be described below.
The nano-crystallization heat treatment is performed at a temperature of −30° C. or higher at which the exothermic peak (first exothermic peak) due to the precipitation of nanocrystals appears, and up to a temperature below the temperature at which the exothermic peak (second exothermic peak) due to the precipitation of coarse crystals appears. Heat up. Here, the first exothermic peak and the second exothermic peak can be determined by measuring the alloy with a differential scanning calorimeter (DSC). For example, the alloy is measured by a differential scanning calorimeter (DSC) (heating rate 20 ° C./min), and the first (low temperature side) exothermic peak is defined as an exothermic peak (first exothermic peak) due to nanocrystal precipitation, and the second The exothermic peak (at the high temperature side) can be regarded as an exothermic peak (second exothermic peak) due to precipitation of coarse crystals. The reason why the lower limit of the temperature is −30° C., the temperature at which the first exothermic peak appears, is that when heat-treating a powder magnetic core or when heat-treating a large amount of amorphous alloy powder in one batch, the temperature must be raised. Considering the speed and heat generation, it can be performed at a temperature of about ± 30 ° C. of the first exothermic peak (for example, 400 to 460 ° C.), so the temperature at which the first exothermic peak appears - 30 ° C. is the lower limit. is.

On the other hand, when the amorphous alloy powder is heat-treated, it is not necessary to consider the temperature rise due to the heat generated by nanocrystallization, and it is effective to heat-treat at a temperature between the first exothermic peak and the second exothermic peak.

Note that the nano-crystallization heat treatment is preferably performed in a non-oxidizing atmosphere such as nitrogen gas.

Moreover, the rate of temperature increase, the holding time at the maximum temperature, and the rate of temperature decrease in the nano-crystallization heat treatment can be appropriately set depending on the alloy components. The heating rate is preferably 0.001° C./second to 1000° C./second. However, if the heating rate is high (e.g., 10°C/sec or more), the maximum temperature may exceed the second exothermic peak due to self-heating due to crystallization of the amorphous alloy powder. It is necessary to pay attention to the amount of The highest temperature reached must be lower than the second exothermic peak, preferably lower than the second exothermic peak -30°C. It is considered that nanocrystallization is completed when the amorphous alloy powder is placed under the maximum temperature for 1 second or more. However, in the case of taking the form of a core, etc., it is necessary to improve heat conduction, and from the viewpoint of ensuring heat treatment, it is preferable to hold for 60 seconds or more, and for large shapes, holding times of 600 seconds and 1800 seconds are preferable. The retention time should be determined by considering efficiency and nanocrystallization. Cooling with air or gas is common for cooling, and there are no particular restrictions on the cooling rate. It is desirable to be cooled to a region. Specifically, the temperature is preferably 400° C. or lower within 300 seconds, and more preferably 300° C. or lower within 600 seconds.

As described above, the nanocrystalline alloy dust core obtained by the present embodiment has the above-described alloy composition, and the body-centered cubic crystal grains having an average crystal grain size of 60 nm or less are present in the amorphous matrix at a volume fraction. It is composed of an alloy powder having a structure in which 30% by volume or more is dispersed and having an alloy ribbon surface formed by roll casting and a fractured surface.

Further, if the amorphous alloy ribbon and amorphous alloy powder of the present embodiment are subjected to nano-crystallization heat treatment, they can have the same structure. Amorphous alloy ribbons, amorphous alloy powders, and nanocrystalline alloy dust cores that have been subjected to nanocrystallization heat treatment have a nanocrystalline structure, so that random magnetic anisotropy effects appear and good soft magnetism comparable to that of amorphous phases. Properties are maintained. Furthermore, since the volume fraction of the crystalline phase with higher magnetization than the amorphous phase increases with crystallization, the total magnetization increases by about 5 to 15%.

The nanocrystalline alloy dust core of this embodiment can have a saturation magnetic flux density of 1.65 T or more.

The average crystal grain size (D) of the nanocrystals is obtained from the X-ray diffraction (XRD) pattern of the alloy powder after heat treatment by obtaining the half-value width (radian angle) of the (Fe—Si)bcc peak, and using the following Scherrer formula: can ask.
D = 0.9 x λ/((half width) x cos θ)
(λ: X-ray wavelength of X-ray source) (for example, λ=0.1789 nm for X-ray source CoKα)
The volume fraction of the nanocrystalline phase is calculated by observing the inside of the powder with a transmission electron microscope (TEM), totaling the areas of the substantially circular crystals, and calculating the ratio to the area of the observation field.

(Example 1)
By roll casting, the alloy composition was reduced to _{FebalCuxSi4B14Sny ( x} + _y =1.40, y=0, 0.25, 0.40, 0.50, 0.70, ₁ . 00, 1.40), amorphous alloy ribbons according to samples 1 to 7 were produced. The amorphous alloy ribbon had a thickness of 25 μm. The thickness of the ribbon was calculated from the density, weight and dimensions (length x width). In addition, this alloy ribbon was subjected to a nano-crystallization heat treatment (410° C.), and the saturation magnetic flux density Bs and the coercive force Hc were obtained from a DC BH curve with an applied magnetic field of 8000 A/m. Table 1 shows the values. Samples 1, 2 and 7 are comparative examples, and samples 3 to 6 are examples.

In order to verify the pulverizability of this amorphous alloy ribbon, it was pulverized according to the following procedure, and those with a particle size of 106 μm or less and those with a particle size of 63 μm or less were collected, and the recovery rate was determined. It was judged that the higher the recovery rate, the better the pulverizability, because more fine pulverized powder was obtained.

Specifically, pulverization was performed by the following procedure. First, the amorphous alloy ribbon was cut into a test piece of about 0.3 g. After measuring the weight w1 of the test piece, it was placed in a metal mortar and pulverized by moving the mortar for 1 minute. After that, it was placed in a sieve with an opening of 106 μm, and the sieve was vibrated for 1 minute with a vibrator to obtain a powder of 106 μm or less that passed through the sieve. The weight w2 of this powder was measured. Then, w2/w1 (%) was taken as the recovery rate of the powder of 106 μm or less. After pulverizing in the same way, put it in a sieve with an opening of 63 μm, vibrate the sieve for 1 minute with a vibrator to obtain a powder of 63 μm or less, measure the weight w3, and w3/w1 (%) is 63 μm or less. The recovery rate of the powder of

FIG. 3 is an appearance photograph of pulverized ribbon powder of the present embodiment. In the pulverized ribbon powder, a flat alloy ribbon surface formed by roll casting and a fractured surface can be observed.

FIG. 4 is a cross-sectional TEM photograph of a powder obtained by subjecting the pulverized ribbon powder of the present embodiment to nano-crystallization heat treatment (hereinafter referred to as the nano-crystallized powder). FIG. 5 is a cross-sectional TEM photograph of powder (hereinafter referred to as comparative nano-crystallized powder) obtained by subjecting pulverized ribbon powder of the amorphous alloy ribbon of the comparative form to which Sn was not added to nano-crystallization heat treatment. Both images show the vicinity of the fracture surface. The practical nano-crystallized powder of FIG. 4 can be observed to have substantially the same crystal structure both near the fracture surface (in the range of 1 μm from the fracture surface) and inside (inside the powder more than 1 μm from the fracture surface). In contrast, in the comparative nanocrystallized powder of FIG. 5, the outline of the crystal is blurred near the fracture surface rather than inside. In other words, it is speculated that the comparative nano-crystallized powder does not have the crystal structure required for a nano-crystalline alloy in the vicinity of the fracture surface, and that the magnetic properties of the powder magnetic core using this comparative nano-crystallized powder tend to deteriorate. be done.

FIG. 1 is a diagram showing the relationship between the Sn substitution amount x and the recovery rate of powder having a particle size of 106 μm or less. FIG. 2 is a graph showing the relationship between the Sn substitution amount x and the recovery rate of powder having a particle size of 63 μm or less. In addition, Table 1 shows the plotted sample Cu addition amount x, Sn addition amount y, the total addition amount of Cu and Sn, the recovery rate of powders of 106 μm or less and 63 μm or less, and the saturation magnetic flux density Bs of the amorphous alloy ribbon. Coercivity is stated. Here, the amorphous alloy ribbon was subjected to nano-crystallization heat treatment, and the saturation magnetic flux density Bs and the coercive force were measured. From this, it can be seen that the amorphous alloy ribbons of Examples are amorphous alloy ribbons that can obtain excellent soft magnetic properties (high saturation magnetic flux density) by applying nano-crystallization heat treatment. In other words, excellent soft magnetic properties (high saturation magnetic flux density) can be obtained even in pulverized ribbon powder by subjecting it to nano-crystallization heat treatment.

For the amorphous alloy ribbons with y=0.25 and 1.40, the recovery rate of powder of 106 μm or less was 54% or less, and the recovery rate of powder of 63 μm or less was 20% or less. However, in the amorphous alloy ribbons with y = 0.40, 0.50, 0.70, and 1.00, the recovery rate of powder of 106 µm or less exceeded 54%, and the recovery rate of powder of 63 µm or less exceeded 20%. rice field. Further, the amorphous alloy ribbon of the present embodiment had a saturation magnetic flux density Bs of 1.70 T or more and a coercive force Hc of 12.0 A/m or less by applying the nano-crystallization heat treatment. Thus, the amorphous alloy ribbon of the present embodiment has excellent pulverizability and excellent soft magnetic properties due to the nano-crystallization heat treatment.

(Example 2)
Amorphous alloy ribbons according to Samples 8 to 12 having an alloy composition of Fe _bal Cu _x Si ₄ B ₁₄ Sn _y in terms of atomic % and having x and y shown in Table 2 were produced by roll casting. The amorphous alloy ribbon had a thickness of 25 μm. The thickness of the ribbon was calculated from the density, weight and dimensions (length x width). The amorphous alloy ribbon was subjected to a nano-crystallization heat treatment (410° C.), and the saturation magnetic flux density Bs and the coercive force Hc (measured in the same manner as in Example 1) were measured. Table 2 shows the results. Samples 8, 9 and 12 are comparative examples, and samples 10 and 11 are examples.

In the same manner as in Example 1, the recoveries of powder with a particle size of 106 μm or less and powder with a particle size of 63 μm or less were determined.

No. 10 samples (x=0.90, y=0.40) and no. Eleven samples (x=0.80, y=0.50) had a recovery rate of 60% or more for powder of 106 μm or less, and a recovery rate of 63 μm or less exceeded 20%. Further, the amorphous alloy ribbon of the present embodiment had a saturation magnetic flux density Bs of 1.70 T or more and a coercive force Hc of 10 A/m or less by applying nanocrystallization heat treatment. As described above, the amorphous alloy ribbon of the present embodiment has excellent pulverizability and excellent magnetic properties due to the nano-crystallization heat treatment.

An alloy ribbon in which the total amount of Cu and Sn added exceeds 1.80 atomic percent has a low saturation magnetic flux density Bs and cannot be put to practical use.

Claims (6)

Alloy composition: Fe _100-abc-d Cu _a Si _b B _c Sn _d (where a, b, c, and d are atomic %, 0.3 ≤ a ≤ 1.2, 1 ≤ b ≤ 10, 11 ≤ c ≤ 17, 0.40 ≤ d ≤ 1.00 , a + d ≤ 1.80),
Amorphous alloy ribbon. 2. The amorphous alloy ribbon according to claim 1, having a thickness of 15 μm or more and 50 μm or less. Alloy composition: Fe _100-abc-d Cu _a Si _b B _c Sn _d (where a, b, c, and d are atomic %, 0.3 ≤ a ≤ 1.2, 1 ≤ b ≤ 10, 11 ≤ c ≤ 17, 0.40 ≤ d ≤ 1.00 , a + d ≤ 1.80),
Having an alloy ribbon surface and a fracture surface,
Amorphous alloy powder. Alloy composition: Fe _100-abc-d Cu _a Si _b B _c Sn _d (where a, b, c, and d are atomic %, 0.3 ≤ a ≤ 1.2, 1 ≤ Amorphous alloy ribbon having a composition represented by b≤10, 11≤c≤17 , 0.40≤d≤1.00 , a+d≤1.80) and formed by roll casting without heat treatment A pulverizing step of pulverizing to form an amorphous alloy powder;
A compression molding step A in which the amorphous alloy powder and a binder are mixed and compression molded to form a green compact;
a crystallization heat treatment step A in which the green compact is subjected to heat treatment for nano-crystallizing the amorphous alloy powder contained in the green compact;
A method for producing a nanocrystalline alloy dust core having Alloy composition: Fe _100-abc-d Cu _a Si _b B _c Sn _d (where a, b, c, and d are atomic %, 0.3 ≤ a ≤ 1.2, 1 ≤ Amorphous alloy ribbon having a composition represented by b≤10, 11≤c≤17 , 0.40≤d≤1.00 , a+d≤1.80) and formed by roll casting without heat treatment A pulverizing step of pulverizing to form an amorphous alloy powder;
a crystallization heat treatment step B in which the amorphous alloy powder is subjected to a heat treatment for nanocrystallization to obtain a nanocrystalline alloy powder;
A compression molding step B in which the nanocrystallized nanocrystalline alloy powder and a binder are mixed and compression molded to form a green compact;
A method for producing a nanocrystalline alloy dust core having Alloy composition: Fe _100-abc-d Cu _a Si _b B _c Sn _d (where a, b, c, and d are atomic %, 0.3 ≤ a ≤ 1.2, 1 ≤ b ≤ 10, 11 ≤ c ≤ 17, 0.40 ≤ d ≤ 1.00 , a + d ≤ 1.80) and has a body-centered cubic structure with an average crystal grain size of 60 nm or less. A nanocrystalline alloy dust core containing a nanocrystalline alloy powder having a nanocrystalline structure dispersed in an amorphous matrix at a volume fraction of 30% by volume or more and having an alloy ribbon surface and a fracture surface.

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