WO2020196608A1

WO2020196608A1 - Amorphous alloy thin strip, amorphous alloy powder, nanocrystalline alloy dust core, and method for producing nanocrystalline alloy dust core

Info

Publication number: WO2020196608A1
Application number: PCT/JP2020/013292
Authority: WO
Inventors: 元基太田
Original assignee: 日立金属株式会社
Priority date: 2019-03-26
Filing date: 2020-03-25
Publication date: 2020-10-01
Also published as: CN113365764A; JPWO2020196608A1; TW202100771A; TWI820323B; JP7148876B2; CN113365764B

Abstract

An amorphous alloy thin strip according to the present invention has an alloy composition represented by the formula: Fe_100-a-b-c-dCu_aSi_bB_cSn_d (wherein a, b, c and d represent values of at.% which satisfy the requirements represented by the formulae: 0.3 ≦ a < 1.55, 1 ≦ b ≦ 10, 11 ≦ c ≦ 17, 0.25 < d ≦ 1.0, and a+d ≦ 1.80). According to the amorphous alloy thin strip of the present invention, it is possible to provide: an amorphous alloy thin strip and an amorphous alloy powder each having excellent crushability and soft magnetic properties; and a method for producing a nanocrystalline alloy dust core using either one of the amorphous alloy thin strip or the amorphous alloy powder.

Description

Amorphous alloy strip, amorphous alloy powder, nanocrystalline alloy dust core, and nanocrystal alloy dust core manufacturing method

The present invention relates to, for example, a PFC circuit used in home appliances such as televisions and air conditioners, a nanocrystal alloy dust core used in a power supply circuit for solar power generation, hybrid vehicles, electric vehicles, etc., and the nanocrystals. The present invention relates to a method for producing an alloy dust core, an amorphous alloy strip as a material for the nanocrystalline alloy dust core, and an amorphous alloy powder.

Fe-based nano as a soft magnetic material used for various transformers, motors, generators, reactors, choke coils, noise suppression parts, laser power supplies, pulse power magnetic parts for accelerators, various sensors, magnetic shields, yokes for magnetic circuits, etc. Crystalline alloys are known. It is known that Fe-based nanocrystalline alloys have a small coercive force and magnetostriction comparable to Co-based amorphous alloys, and exhibit a high saturation magnetic flux density comparable to Fe-based amorphous alloys. This Fe-based nanocrystal alloy is usually produced by quenching from a liquid phase or a gas phase to form an amorphous alloy, which is then microcrystallized by heat treatment. Known methods for quenching from the liquid phase include a single roll method, a twin roll method, a centrifugal quenching method, a spinning method in a rotating liquid, an atomizing method, and a cavitation method. Further, 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.

Fe-based nanocrystalline alloys are microcrystallized amorphous alloys produced by these methods, and have almost no thermal instability as seen in amorphous alloys, and have a high saturation magnetostrictive density comparable to that of Fe-based amorphous alloys. It is known to have low magnetostriction and exhibit excellent soft magnetic properties. Further, it is known that nanocrystal alloys have a small change with time and are excellent in temperature characteristics. The nanocrystal alloy can be obtained by heat-treating an amorphous alloy capable of nanocrystallization at a temperature equal to or higher than the nanocrystallization start temperature (hereinafter, also simply referred to as “nanocrystallization heat treatment”). Hereinafter, the amorphous alloy capable of nanocrystallization before the nanocrystallization heat treatment is also simply referred to as "amorphous alloy". Further, an Fe-based nanocrystal alloy obtained by subjecting an amorphous alloy to a nanocrystallizing heat treatment is also simply referred to as a "nanocrystal alloy".

Amorphous alloys are usually manufactured by continuously casting them into thin strips by rolling quenching, and are manufactured as long alloy strips. Therefore, as the magnetic core made of nanocrystalline alloy, one in which alloy strips are wound or laminated is generally used. However, in recent years, electromagnetic booster circuits such as reactors have been required to be used for high frequency applications of several tens to several hundreds of kHz due to needs such as miniaturization, and powdered magnetic materials are hardened as a suitable magnetic core. The amount of dust cores that have been generated is increasing. The reasons why the dust core is used are as follows.

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

In the high frequency region of several tens to several hundreds of kHz, a magnetic permeability of several tens to several hundreds is required, so that the flat powder is easier to use than the spherical powder. The reason is that when the in-plane direction of the flat powder becomes parallel to the magnetic path, the demagnetizing field coefficient in the magnetic path direction becomes relatively low and the shape magnetic anisotropy works in the magnetic path direction. This is because it is easy to raise. The amorphous alloy powder obtained by the atomization method has a spherical shape, but is an amorphous alloy obtained by crushing a thin band of an amorphous alloy (hereinafter, also simply referred to as "amorphous alloy thin band") produced by roll quenching and capable of nano-crystallization. Since the powder (hereinafter, also simply referred to as "thin band crushed powder") becomes flat, it is being considered to use this thin band crushed powder.

The amorphous alloy strip has the same hardness as the Fe-based amorphous alloy strip. Therefore, it has the disadvantage that it is difficult to pulverize and it is difficult to control the particle size after pulverization.

Since the amorphous alloy thin band 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 produce thin band crushed powder by crushing. Although the toughness of the amorphous alloy strip is reduced by the embrittlement heat treatment, the amorphous alloy strip is crushed while being torn, so that stress tends to remain locally in the strip crushed powder, which is one of the causes of deterioration of magnetic properties. Become. In addition, the embrittlement heat treatment becomes a bottleneck in the manufacturing process. Further, when the embrittlement heat-treated thin band crushed powder and the binder are compression-molded to form a powder magnetic core, the internal stress generated in the pressurizing process remains in the powder magnetic core, but the internal stress is relaxed thereafter. Even if the heat treatment (hereinafter referred to as strain removing heat treatment) is performed, it is difficult to sufficiently relax the stress, and sufficient soft magnetic properties cannot be obtained. The reason is that the improvement effect of the strain removing heat treatment of the amorphous alloy decreases when it is repeatedly performed. Therefore, if the embrittlement heat treatment is performed before pulverization, the stress relaxation by the heat treatment after compression molding is not sufficiently performed. .. Therefore, it is effective to develop an amorphous alloy strip having good pulverizability without embrittlement heat treatment.

For example, Patent Document 1 has a problem of crushing an amorphous soft magnetic alloy containing Fe, B, P and Cu, which is difficult to crush, as it is without performing a brittle heat treatment, and as a means for solving the problem, a composition is used. It is represented by the formula Fe _a Si _b B _c P _x Cu _y Sn _z , 79 ≦ a ≦ 86 at%, 0 ≦ b ≦ 10 at%, 1 ≦ c ≦ 14 at%, 1 ≦ x ≦ 15 at%, 0.4 ≦ A soft magnetic alloy powder satisfying y ≦ 2 at%, 0.5 ≦ z ≦ 6 at% and 0.04 ≦ y / x ≦ 1.20, wherein the soft magnetic alloy powder is an amorphous single phase, soft magnetic. We are proposing alloy powder.

Further, in paragraph 0022 of Patent Document 1, regarding the improvement of pulverizability, "In the above-mentioned soft magnetic alloy powder, Sn is an element responsible for forming an amorphous phase, and by containing this Sn, the melted alloy is rapidly cooled. It is an essential element because the amorphous alloy strips and flakes produced in the above process can be crushed as they are without heat treatment. "

Further, Patent Document 2 makes it difficult to obtain a Fe-based nanocrystal material containing Nb of several% or more, such as FeCuNbSiB-based or FeCuNbB-based, having a high saturation magnetic flux density of 1.7 T or more, and then manufactures powder. As a soft magnetic alloy that is easy to use, a composition that does not contain Nb is proposed, and as an embodiment thereof, an alloy strip of _Febal Cu _1.35 Si ₁₄ B ₃ Sn _0.5 (Table 3, Sample No. .19) is presented.

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

However, further studies are required to obtain an amorphous alloy strip capable of achieving both excellent pulverizability and soft magnetic properties.

Therefore, an object of the present invention is to provide an amorphous alloy strip having excellent grindability and to obtain excellent soft magnetic properties by subjecting it to nanocrystallizing heat treatment, and to provide an amorphous alloy obtained by grinding the amorphous alloy strip. It is an object of the present invention to provide an alloy powder, and to provide a nanocrystal alloy dust core produced by using the alloy powder, and a method for producing a nanocrystal alloy dust core.

Specific means for solving the above problems include the following aspects.
<1> Alloy composition: Fe _100-ab-c-d Cu _a Si _b B _c Sn _d (where a, b, c, d are atomic%, 0.3 ≦ a <1.55 , 1 ≦ b ≦ 10, 11 ≦ c ≦ 17, 0.25 <d ≦ 1.0, a + d ≦ 1.80).
Amorphous alloy strip.
<2> The amorphous alloy strip according to <1>, which has 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, d are atomic%, 0.3 ≦ a <1.55 , 1 ≦ b ≦ 10, 11 ≦ c ≦ 17, 0.25 <d ≦ 1.0, a + d ≦ 1.80).
It has an alloy strip surface and a fracture surface,
Amorphous alloy powder.
<4> Alloy composition: Fe _100-a-bc-d Cu _a Si _b B _c Sn _d (where a, b, c, d are atomic%, 0.3 ≦ a <1.55 , 1 ≦ b ≦ 10, 11 ≦ c ≦ 17, 0.25 <d ≦ 1.0, a + d ≦ 1.80), and crushed an amorphous alloy strip that has not been heat-treated. Amorphous alloy powder crushing process
The compression molding step A in which the amorphous alloy powder and the binder are mixed and compression molded to obtain a green compact.
A crystallization heat treatment step A in which the green compact is subjected to a heat treatment for nanocrystallizing the amorphous alloy powder contained in the green compact.
A method for producing a nanocrystal alloy dust core having.
<5> Alloy composition: Fe _100-a-bc-d Cu _a Si _b B _c Sn _d (where a, b, c, d are atomic%, 0.3 ≦ a <1.55 , 1 ≦ b ≦ 10, 11 ≦ c ≦ 17, 0.25 <d ≦ 1.0, a + d ≦ 1.80), and crushed an amorphous alloy strip that has not been heat-treated. Amorphous alloy powder crushing process
The crystallization heat treatment step B of subjecting the amorphous alloy powder to a heat treatment for nanocrystallization to obtain a nanocrystal alloy powder,
The compression molding step B in which the nanocrystallized nanocrystal alloy powder and the binder are mixed and compression molded to obtain a green compact.
A method for producing a nanocrystal alloy dust core having.
<6> Alloy composition: Fe _100-a-bc-d Cu _a Si _b B _c Sn _d (where a, b, c, d are atomic%, 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 having an average crystal grain size of 60 nm or less. A nano-crystal alloy dust core containing an amorphous alloy powder having a structure in which crystal grains are dispersed in an amorphous matrix in a body integral ratio of 30% by volume or more, and having an alloy thin band surface and a fracture surface.

According to the present invention, an amorphous alloy ribbon having excellent pulverizability and having excellent soft magnetic properties obtained by subjecting nanocrystallization heat treatment, an amorphous alloy powder obtained by crushing the amorphous alloy ribbon, and an amorphous alloy powder. It is possible to provide a nanocrystal alloy dust core produced by using these, and a method for producing a nanocrystal alloy dust core.

It is a figure which shows the relationship between the Sn substitution amount x and the recovery rate of the powder of 106 μm or less. It is a figure which shows the relationship between the Sn substitution amount x, and the recovery rate of the powder of 63 μm or less. It is an appearance photograph of the thin band crushed powder of this embodiment. It is a TEM photograph of the thin band pulverized powder of this embodiment which has been heat-treated for nanocrystallization. It is a TEM photograph of the thin band pulverized powder of the comparative form which performed the heat treatment for nanocrystallization.

Next, the present invention will be specifically described with reference to embodiments, but the present invention is not limited to these embodiments. In addition, in this specification, the numerical range represented by using "-" means the range including the numerical values before and after "-" as the lower limit value and the upper limit value. In the numerical range described stepwise in the present specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. .. Further, in the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.

<Amorphous alloy strip>
The amorphous alloy strip of the present embodiment satisfies the following alloy composition.
Alloy composition: Fe _100-ab-c-d Cu _a Si _b B _c Sn _d (where a, b, c, 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 strip having the above alloy composition is a soft magnetic material that has excellent pulverizability and can obtain excellent soft magnetic properties (high saturation magnetic flux density) by subjecting it to nanocrystallization heat treatment.

In the amorphous alloy strip of the present embodiment, the raw material weighed so as to have the above alloy composition is melted by means such as high-frequency induction melting, and then discharged to the surface of a cooling roll rotating at high speed via a nozzle. It can be manufactured by roll quenching such as single roll or twin roll which is rapidly cooled and solidified. From the viewpoint of facilitating continuous casting and improving the production efficiency of the amorphous alloy thin band, and by delaying the cooling rate of the molten metal to intentionally cause embrittlement to improve the pulverizability of the thin band crushed powder. From the viewpoint of improving the production efficiency, the thickness of the amorphous alloy strip is preferably 15 μm or more. Further, from the viewpoint of improving the pulverizability and improving the production efficiency of the thin band crushed powder, the thickness of the amorphous alloy thin band is preferably 50 μm or less.

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

<Amorphous alloy powder>
Further, the amorphous alloy powder of the present embodiment has an alloy composition: Fe _100-ab-c-d Cu _a Si _b B _c Sn _d (where a, b, c, d are 0 in atomic%. It has a composition represented by 3 ≦ a <1.55, 1 ≦ b ≦ 10, 11 ≦ c ≦ 17, 0.25 <d ≦ 1.0, a + d ≦ 1.80), and has an alloy thin band surface. And a fracture surface. The alloy strip surface is a surface corresponding to both opposite planes of the amorphous alloy strip formed by roll casting.

This amorphous alloy powder becomes a nanocrystal alloy powder having a high saturation magnetic flux density by undergoing nanocrystallization heat treatment. Details will be described later.

The alloy composition of the amorphous alloy strip, the amorphous alloy powder, and the nanocrystal alloy dust core of the present embodiment will be described below.

The amorphous alloy strip, the amorphous alloy powder, and the nanocrystalline alloy dust core of the present embodiment have a composition without adding Nb or Mo and have a high saturation magnetic flux density.

The alloy composition of the amorphous alloy strip and the amorphous alloy powder of the present embodiment (hereinafter, the amorphous alloy strip and the amorphous alloy powder of the present embodiment may be simply referred to as "amorphous alloy strip and the like"). , It is a composition capable of nano-crystallization. Further, in the structure of the nanocrystal alloy strip and the nanocrystal alloy powder obtained by subjecting the amorphous alloy strip of the present embodiment to the nanocrystallization heat treatment, crystal grains having an average particle size of 30 nm or less have an area in the amorphous matrix. It is preferable that the structure is dispersed in a fraction of more than 0% and less than 30%.

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

The alloy composition of amorphous alloy strips and the like 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 atomic% of Fe in the alloy composition such as an amorphous alloy strip is preferably 77 atomic% or more, more preferably 79 atomic% or more.

Cu (copper) has the effect of embrittlement of the amorphous alloy strip and facilitating pulverization. In the Fe-B amorphous matrix, the heat of mixing Cu becomes positive with those elements, so in order to lower the potential energy, Cu atoms gather together during the cooling process during production to form a cluster. Since the Fe concentration increases around the cluster, a high-density region with a high Fe concentration is generated. It is speculated that this variation in density facilitates grinding. Further, since nanocrystals are uniformly generated in the alloy structure with Cu atoms as nuclei, the addition of Cu is indispensable.

In order to obtain the above effects, the atomic% of Cu in the alloy composition of an amorphous alloy strip or the like 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.

Nanocrystal alloy dust powder with excellent soft magnetic properties by suppressing the formation of relatively large crystals that grow into coarse crystal grains by heat treatment after quench solidification (before nanocrystallization heat treatment) in amorphous alloy strips, etc. From the viewpoint of obtaining a magnetic core, and by increasing the amorphous phase that relieves residual stress in the nanocrystal alloy strip and nanocrystal alloy powder obtained by heat-treating the amorphous alloy strip, etc., the nanocrystal alloy dust core From the viewpoint of improving soft magnetic properties, the atomic% of Cu in the alloy composition of amorphous alloy strips and the like is less than 1.55 atomic%, preferably 1.4 atomic% or less, and more preferably 1.2 atomic% or less. It is preferable, and less than 1.0 atomic% is more preferable.

Si (silicon) is an element that forms an alloy with Fe as a nanocrystal phase by heat treatment to form a bcc phase ((Fe—Si) bcc phase). It is also an element that acts on the amorphous forming ability during quenching and solidification. The atomic% of Si in the alloy composition of an amorphous alloy strip or the like is 1 atomic% or more, preferably 2 atomic% or more, more preferably 2.5 atomic% or more, in order to form an amorphous phase after quenching and solidification with good reproducibility. preferable. On the other hand, in order to ensure the reproducibility of the viscosity of the molten alloy, it 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 quenching and solidification. Further, B has an action of allowing Cu atoms, which are the cores of nanocrystals, to exist uniformly in the alloy structure (in the amorphous phase) without being unevenly distributed.

The atomic% of B in the alloy composition of an amorphous alloy strip or the like is 11 atomic% or more and 12 atoms in order to form an amorphous phase after quenching and solidifying with good reproducibility and uniformly present Cu atoms in the amorphous phase. % Or more is preferable. Further, although it is related to the total amount with the amount of Si described later, the atomic% of B in the alloy composition is 17 atomic% or less, and 15 from the viewpoint of obtaining a nanocrystalline alloy dust core having a high saturation magnetic flux density Bs. It is preferably 5.5 atomic% or less.

Further, 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 strip or the like decreases, the saturation magnetic flux density Bs tends to decrease. Further, with respect to the saturation magnetic flux density Bs, Si and B have a relatively large influence on Fe. Therefore, the total (b + c) of the atomic% of Si and the atomic% of B in the alloy composition of the amorphous alloy strip or the like is 20 atomic% or less (b + c) from the viewpoint of obtaining a nanocrystalline alloy dust core having a high saturation magnetic flux density Bs. 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 strips and the like. Further, by adding Sn in combination with Cu, the embrittlement of the amorphous alloy strip and the like becomes more remarkable. Sn having a low melting point can move within the amorphous alloy ribbon and the like even at a relatively low temperature, and can be evenly distributed over the entire amorphous alloy strip and the like. In relation to the formation of a compound by Sn and Cu, it is considered that Sn has an effect of widely dispersing Cu (Sn) clusters at a higher number density over the entire amorphous alloy strip and the like. In addition, Sn has an action effect of suppressing the formation of coarse crystal grains after heat treatment of an amorphous alloy strip or the like.

In order to obtain these effects, the atomic% of Sn in the alloy composition of an amorphous alloy strip or the like 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 lower the soft magnetic properties, the atomic% of Sn in the alloy composition of an amorphous alloy strip or the like 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 further preferable.

The total amount (a + d) of the amount of Cu and the amount of Sn in the alloy composition of an amorphous alloy strip or the like shall be 1.80 atomic% or less. When the total amount of Cu and Sn in the alloy composition is 1.80 atomic% or less, it is easy to obtain a nanocrystal alloy strip or a nanocrystal alloy powder having a large saturation magnetic flux density. The total amount of Cu and Sn in the alloy composition of the amorphous alloy strip and the like is preferably 1.6 atomic% or less from the viewpoint of obtaining the nanocrystal alloy strip and the nanocrystal alloy powder having a large saturation magnetic flux density, preferably 1.5 Atomic% or less is more preferable, and 1.45 atomic% or less is further preferable. The sum of the amount of Cu and the amount of Sn in the alloy composition of the amorphous alloy strip and the like is from the viewpoint of obtaining an amorphous alloy strip having excellent pulverizability and from the viewpoint of obtaining a nanocrystal alloy strip and a nanocrystal alloy powder having a large saturation magnetic flux density. , 0.8 atomic% or more is preferable, 1.0 atomic% or more is more preferable, 1.2 atomic% or more is further preferable, and 1.25 atomic% or more is further preferable.

The amorphous alloy strip or the like of the present embodiment preferably has fine crystal grains dispersed in the amorphous (matrix). For alloys with a large amount of Fe, it is better not to produce a completely amorphous alloy, but rather to produce an amorphous alloy in which fine crystal grains are dispersed in an amorphous (matrix) and then perform heat treatment to proceed with crystallization. It has a fine crystal grain structure and can realize excellent soft magnetic properties.

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

Fe-B-based and Fe-B-Si-based alloy compositions tend to form an amorphous phase, but by adding an appropriate amount of Cu or Sn, which is insoluble in Fe, to Fe immediately after casting by the ultra-quenching method. Fine crystal grain nuclei can be appropriately formed in the base alloy (intermediate alloy). In the amorphous alloy having this structure, fine crystal grains are formed at the stage before the nanocrystallization heat treatment, and the crystal grains are not coarsened by appropriate heat treatment, a nanocrystal alloy can be obtained, and good soft magnetism is obtained. The characteristics are obtained. Further, since the fine crystal grains are randomly dispersed, the brittleness can be made high enough to cause breakage by bending at 180 °. Therefore, pulverization is possible without using a powerful pulverizing means such as a milling device, and the obtained amorphous alloy powder has a small residual stress.

The above alloy composition may contain impurities in addition to the listed elements. Examples of impurities include P (phosphorus), S (sulfur), N (nitrogen), C (carbon) and the like. This impurity can be replaced with Fe in the range of less than 1.0 atomic% in the atomic% of the above composition formula as 100 atomic%.

In particular, P is an element that acts on the amorphous forming ability during quenching and solidification, but it can also be a factor that deteriorates pulverizability. In order to ensure the pulverizability, it is necessary to further add Sn having an embrittlement effect, but since Sn is originally an element that lowers 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 strip is preferably less than 1.0 atomic%, more preferably 0.5 atomic% or less, with the atomic% of the above alloy composition being 100 atomic%. 0.3 atomic% or less is further preferable, 0.2 atomic% or less is further preferable, and 0.1 atomic% or less is even more preferable.

Since C is effective in stabilizing the viscosity of the molten alloy during casting, even if P is set in the above range and C is contained in the range of 0.40 atomic% or less in the amorphous alloy strip or the like. Good. The atomic% of C in the alloy composition of an amorphous alloy strip or the like is preferably 0.37 atomic% or less, more preferably 0.35 atomic% or less. Further, the atomic% of C in the alloy composition of the amorphous alloy strip or the like is preferably 0.10 atomic% or more, more preferably 0.20 atomic% or more, from the viewpoint of obtaining stabilization of the viscosity of the molten alloy during casting. , 0.22 atomic% or more is more preferable.

(Crushing and rating)
For pulverization of the amorphous alloy strip having the above alloy composition, a known means such as an atomizer, a ball mill, a jet mill, and a stamp mill can be adopted. The obtained pulverized powder of the amorphous alloy strip has an alloy strip surface formed by roll casting and a fracture surface.

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

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

According to this classification, it is preferable that the amorphous alloy powder having a particle size of more than 40 μm is 10% by mass or less of the total amorphous alloy powder. It is not easy to stably obtain an amorphous phase or a mixed phase of an amorphous phase and a fine crystal phase in this amorphous alloy powder having a particle size of more than 40 μm. Therefore, 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 further 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 many remaining 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 40 μm or less can be specified.

At this time, the amorphous alloy powder having a particle size of 20 μm or less can obtain an Fe-based nanocrystal alloy powder having a high saturation magnetic flux density Bs capable of suppressing magnetic saturation even in high-frequency applications, and is more than 20 μm and 40 μm or less. 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 so that the desired magnetic properties can be obtained.

In the above, the amorphous alloy powder having a particle size of more than 20 μm and 40 μm or less is defined as 30% by mass or more and 90% by mass or less of the total amorphous alloy powder, and the amorphous alloy powder having a particle size of 20 μm or less is 5% by mass or more and 60% by mass or more of the entire amorphous alloy powder. It is set to mass% or less. As described above, the amount can be changed according to the required magnetic characteristics.

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 whole amorphous alloy powder.

<Nanocrystalline alloy dust core>
The method for producing a nanocrystal alloy dust core according to the first embodiment using the above amorphous alloy powder is as follows.
Alloy composition: Fe _100-a- bc _-d Cu _a Si _b B _c Sn _d (where a, b, c, d are atomic%, 0.3 ≦ a <1.55, 1 ≦ Amorphous alloy having a composition represented by b ≦ 10, 11 ≦ c ≦ 17, 0.25 <d ≦ 1.0, a + d ≦ 1.80) and not subjected to heat treatment. The crushing process to make powder and
The compression molding step A in which the amorphous alloy powder and the binder are mixed and compression molded to obtain a green compact.
A crystallization heat treatment step A in which the green compact is subjected to a heat treatment for nanocrystallizing the amorphous alloy powder contained in the green compact.
It has.

Further, the method for producing the nanocrystal alloy dust core of the second embodiment using the above-mentioned amorphous alloy powder is described.
Alloy composition: Fe _100-a- bc _-d Cu _a Si _b B _c Sn _d (where a, b, c, d are atomic%, 0.3 ≦ a <1.55, 1 ≦ Amorphous alloy having a composition represented by b ≦ 10, 11 ≦ c ≦ 17, 0.25 <d ≦ 1.0, a + d ≦ 1.80) and not subjected to heat treatment. The crushing process to make powder and
The crystallization heat treatment step B in which the amorphous alloy powder is subjected to nanocrystallization heat treatment to obtain nanocrystal alloy powder,
The compression molding step B in which the nanocrystallized nanocrystal alloy powder and the binder are mixed and compression molded to obtain a green compact.
It has.

The heat treatment in the crushing step of the method for producing the nanocrystal alloy dust core of the first and second embodiments described above is an embrittlement heat treatment or a nanocrystallization heat treatment, for example, at 200 ° C. or higher. Temperature heat treatment corresponds. The embrittlement heat treatment is preferably performed at 250 ° C. or higher.

According to the methods for producing nanocrystal alloy dust cores of the first and second embodiments, the amorphous alloy strip before pulverization is not subjected to brittle heat treatment or nanocrystallization heat treatment, so that the crystallization heat treatment step is performed. When nanocrystallizing heat treatment is applied to an amorphous alloy powder or green compact in A or the crystallization heat treatment step B, sufficient stress relaxation is performed, and a dust core having excellent soft magnetic properties such as saturation magnetic flux density can be obtained. ..

According to the method for producing a nanocrystal alloy powder magnetic core of the first embodiment described above (the embodiment in which the powder is subjected to the nanocrystallization heat treatment), the nanocrystallization heat treatment is performed together with the nanocrystallization of the amorphous alloy powder. , The integration by curing the binder and the stress relaxation of the compressive strain applied to the amorphous alloy powder can be performed at the same time.

According to the method for producing a nanocrystal alloy dust core of the second embodiment described above (the embodiment in which the amorphous alloy powder is subjected to the nanocrystallization heat treatment), the nanocrystallization heat treatment is performed together with the nanocrystallization of the amorphous alloy powder. , The stress relaxation of the compressive strain applied to the amorphous alloy powder can be performed at the same time.

The method for producing the nano-crystal alloy dust core of the first embodiment and the method for producing the nano-crystal alloy dust core of the second embodiment are used to obtain the green compact and then to prepare the green compact. It may have a heat treatment step for curing the contained binder and a heat treatment step for performing strain removing heat treatment of the green compact.

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

Amorphous alloy powder, binder such as silicone resin, and organic solvent if necessary are added and kneaded. In the case of compression molding, when an organic solvent is used, the organic solvent is then evaporated. It can also be granulated after kneading. A green compact can be obtained by putting this kneaded material in a press die and compression molding it into a desired magnetic core shape such as a toroidal shape. At this time, the nanocrystallization heat treatment is applied to the amorphous alloy powder or the green compact.

When the nanocrystallizing heat treatment is applied to the amorphous alloy powder, the green compact can also be heat-treated to cure the binder.

Further, when the nanocrystallization heat treatment is applied to the green compact, the heat treatment for curing the binder can also be performed at the same time.

<Nanocrystal heat treatment>
Hereinafter, the nanocrystallization heat treatment will be described.
The nanocrystallization heat treatment is performed up to a temperature of -30 ° C or higher at which an exothermic peak due to nanocrystal precipitation (first exothermic peak) appears and below a temperature at which an exothermic peak (second exothermic peak) due to coarse crystal precipitation appears. The temperature rises. Here, the first exothermic peak and the second exothermic peak can be grasped 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 set as the exothermic peak due to nanocrystal precipitation (first exothermic peak). The exothermic peak on the (high temperature side) can be set as the exothermic peak (second exothermic peak) due to coarse crystal precipitation. The lower limit of the temperature was set to -30 ° C, the temperature at which the first exothermic peak appears, when the powder magnetic core is heat-treated or when a large amount of amorphous alloy powder is heat-treated in one batch. Since the heat treatment can be performed at a temperature of about ± 30 ° C. of the first heat generation peak (for example, 400 to 460 ° C.) in consideration of speed and heat generation, the lower limit is the temperature of −30 ° C. at which the first heat generation peak appears. Is.

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

The nanocrystallization heat treatment is preferably performed in a non-oxidizing atmosphere such as nitrogen gas.

Further, the heating rate, the holding time at the maximum temperature, and the temperature decreasing rate in the nanocrystallization heat treatment can be appropriately set depending on the alloy component. The heating rate is preferably 0.001 ° C./sec to 1000 ° C./sec. However, if the temperature rise rate is high (for example, 10 ° C./sec or more), the maximum temperature may reach the second exothermic peak or higher due to self-heating associated with the crystallization of the amorphous alloy powder. Therefore, the amorphous alloy powder to be processed at the same time. It is necessary to pay attention to the amount of. The maximum temperature reached needs to be lower than the second exothermic peak, and is preferably lower than the second exothermic peak −30 ° C. It is considered that nanocrystallization is completed if the amorphous alloy powder is placed at the maximum temperature for 1 second or longer. However, when taking the form of a core or the like, it is necessary to improve heat conduction, and from the viewpoint of surely performing heat treatment, holding time of 60 seconds or more is good, and holding time of 600 seconds or 1800 seconds is preferable for a large shape. The retention time should be determined in consideration of efficiency and nanocrystallization. The temperature is generally cooled by air or gas, and there are no particular restrictions on the cooling rate. However, if the maximum temperature is close to the second exothermic peak, special attention is required, and the temperature immediately below the first exothermic peak is required. It is desirable to be cooled to the 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 nano-crystal alloy dust core obtained by the present embodiment has the above-mentioned alloy composition, and crystal grains having a body-centered cubic structure having an average crystal grain size of 60 nm or less have a body integration rate in the amorphous matrix. It is composed of an alloy powder having a structure dispersed in an amount of 30% by volume or more, an alloy thin band surface formed by roll casting, and a fracture surface.

Further, if the amorphous alloy strip and the amorphous alloy powder of the present embodiment are subjected to nanocrystallizing heat treatment, the same structure can be obtained. Amorphous alloy strips and amorphous alloy powders that have undergone nanocrystallization heat treatment and nanocrystal alloy dust cores have a nanocrystal structure, so the effect of random magnetic anisotropy appears, and the soft magnetism is as good as the amorphous phase. The characteristics are maintained. Further, since the volume fraction of the crystal phase whose magnetization is higher than that of the amorphous phase increases with crystallization, the total magnetization increases by about 5 to 15%.

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

For the average crystal grain size (D) of nanocrystals, the half width (radian angle) of the (Fe—Si) bcc peak was obtained from the X-ray diffraction (XRD) pattern of the alloy powder after heat treatment, and the following formula was used by Scherrer. Can be sought.
D = 0.9 × λ / ((half width) × cosθ)
(Λ: X-ray wavelength of X-ray source) (For example, λ = 0.1789 nm in X-ray source CoKα)
The volume fraction of the nanocrystal phase is calculated by observing the inside of the powder with a transmission electron microscope (TEM), totaling the areas of substantially circular crystals, and calculating the ratio with respect to the area of the observation field of view.

(Example 1)
The roll casting, the alloy _{_{_{_{composition, Fe bal Cu x Si 4 B}}}} 14 Sn y (x + y = 1.40 in atomic%, y = 0,0.25,0.40,0.50,0.70,1. Amorphous alloy strips according to Samples 1 to 7 represented by 00, 1.40) were produced. The amorphous alloy strip had a thickness of 25 μm. The thickness of the thin band was calculated from the density, weight and dimensions (length x width). Further, the alloy strip was subjected to nanocrystallizing heat treatment (410 ° C.), and the saturation magnetic flux density Bs and the coercive force Hc were obtained from the DC BH curve of the applied magnetic field of 8000 A / m. The values are shown in Table 1. 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 strip, each of them was pulverized by the following procedure, and those having a particle size of 106 μm or less and those having a particle size of 63 μm or less were recovered, 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, the crushing was performed by the following procedure. First, the amorphous alloy strip was cut to obtain a test piece of about 0.3 g, and after measuring the weight w1 of the test piece, it was placed in a metal mortar and the pot was moved for 1 minute to pulverize it. Then, it was placed in a sieve having a mesh size of 106 μm, and the sieve was vibrated for 1 minute with a vibrator to obtain a powder having a mesh size of 106 μm or less that passed through the sieve. The weight w2 of this powder was measured. Then, w2 / w1 (%) was used as the recovery rate of the powder of 106 μm or less. After crushing in the same manner, the powder is placed in a sieve having an opening of 63 μm and vibrated with a vibrator for 1 minute to obtain a powder of 63 μm or less, the weight w3 is measured, and w3 / w1 (%) is 63 μm or less. The recovery rate of the powder of.

FIG. 3 is an external photograph of the thin band crushed powder of the present embodiment. In the pulverized strip powder, an alloy strip surface formed by flat roll casting and a fracture surface can be observed.

FIG. 4 is a cross-sectional TEM photograph of the powder obtained by subjecting the thin band crushed powder of the present embodiment to nanocrystallizing heat treatment (hereinafter referred to as the implemented nanocrystallized powder). FIG. 5 is a cross-sectional TEM photograph of a powder (hereinafter referred to as comparative nanocrystallized powder) obtained by subjecting a thin-band pulverized powder of a comparative form of an amorphous alloy strip to which Sn is not added to a nanocrystallization heat treatment. Both show the vicinity of the fracture surface. In the nanocrystallized powder carried out in FIG. 4, substantially the same crystal structure can be observed both in the vicinity of the fracture surface (range from the fracture surface to 1 μm) and inside (inside the powder exceeding 1 μm from the fracture surface). On the other hand, in the comparative nanocrystallized powder of FIG. 5, the crystal outline is blurred near the fracture surface rather than inside. That is, it is inferred that the comparative nanocrystallized powder does not have the crystal structure required as a nanocrystal alloy in the vicinity of the fracture surface, and the powder magnetic core using this comparative nanocrystallized powder tends to deteriorate in magnetic properties. Will be done.

FIG. 1 is a diagram showing the relationship between the Sn substitution amount x and the recovery rate of powder of 106 μm or less. FIG. 2 is a diagram showing the relationship between the Sn substitution amount x and the recovery rate of powder of 63 μm or less. Table 1 shows the amount of Cu added x, the amount of Sn added y, the total amount of Cu and Sn added, 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 strip. The coercive force is described. Here, the amorphous alloy strip was subjected to nanocrystallization 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 strip of the example is an amorphous alloy strip that can obtain excellent soft magnetic properties (high saturation magnetic flux density) by subjecting it to nanocrystallization heat treatment. That is, even in the thin band pulverized powder, excellent soft magnetic characteristics (high saturation magnetic flux density) can be obtained by performing the nanocrystallization heat treatment.

For the amorphous alloy strips with y = 0.25 and 1.40, the recovery rate of the powder of 106 μm or less was 54% or less, and the recovery rate of the powder of 63 μm or less was 20% or less. However, for the amorphous alloy strips with y = 0.40, 0.50, 0.70, 1.00, the recovery rate of the powder of 106 μm or less exceeds 54%, and the recovery rate of the powder of 63 μm or less exceeds 20%. It was. Further, the amorphous alloy strip 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 subjecting the nanocrystallizing heat treatment. As described above, the amorphous alloy strip of the present embodiment has excellent pulverizability and excellent soft magnetic properties by subjecting the nanocrystal heat treatment.

(Example 2)
The roll casting, the alloy composition is _{_{_{_{Fe bal Cu x Si 4 B 14}}}} Sn y in atomic%, x shown in Table 2, one of y, to produce an amorphous alloy ribbon according to the sample 8-12. The amorphous alloy strip had a thickness of 25 μm. The thickness of the thin band was calculated from the density, weight and dimensions (length x width). Table 2 shows the results of measuring the saturation magnetic flux density Bs and the coercive force Hc (measured in the same manner as in Example 1) by subjecting the amorphous alloy strip to nanocrystallizing heat treatment (410 ° C.). Samples 8, 9 and 12 are comparative examples, and samples 10 and 11 are examples.

Similar to Example 1, the recovery rate of the powder having a particle size of 106 μm or less and the powder having a particle size of 63 μm or less was determined.

No. 10 samples (x = 0.90, y = 0.40) and No. In the 11 samples (x = 0.80, y = 0.50), the recovery rate of the powder of 106 μm or less exceeded 60%, and the recovery rate of the powder of 63 μm or less exceeded 20% or more. Further, the amorphous alloy strip 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 subjecting the nanocrystallizing heat treatment. As described above, the amorphous alloy strip of the present embodiment has excellent pulverizability and excellent magnetic properties by subjecting the nanocrystal heat treatment.

In the alloy thin band in which the total amount of Cu and Sn added exceeds 1.80 atomic%, the saturation magnetic flux density Bs is lowered and it cannot be put into practical use.

Claims

Alloy composition: Fe 100-ab-c-d Cu a Si b B c Sn d (where a, b, c, d are atomic%, 0.3 ≦ a <1.55, 1 ≦ It has a composition represented by b ≦ 10, 11 ≦ c ≦ 17, 0.25 <d ≦ 1.0, a + d ≦ 1.80).
Amorphous alloy strip.
The amorphous alloy strip according to claim 1, wherein the thickness is 15 μm or more and 50 μm or less.
Alloy composition: Fe 100-ab-c-d Cu a Si b B c Sn d (where a, b, c, d are atomic%, 0.3 ≦ a <1.55, 1 ≦ It has a composition represented by b ≦ 10, 11 ≦ c ≦ 17, 0.25 <d ≦ 1.0, a + d ≦ 1.80).
It has an alloy strip surface and a fracture surface,
Amorphous alloy powder.
Alloy composition: Fe 100-a- bc -d Cu a Si b B c Sn d (where a, b, c, d are atomic%, 0.3 ≦ a <1.55, 1 ≦ Amorphous alloy ribbon having a composition represented by b ≦ 10, 11 ≦ c ≦ 17, 0.25 <d ≦ 1.0, a + d ≦ 1.80) and formed by roll casting without heat treatment. And the crushing process to make an amorphous alloy powder
The compression molding step A in which the amorphous alloy powder and the binder are mixed and compression molded to obtain a green compact.
A crystallization heat treatment step A in which the green compact is subjected to a heat treatment for nanocrystallizing the amorphous alloy powder contained in the green compact.
A method for producing a nanocrystal alloy dust core having.
Alloy composition: Fe 100-a- bc -d Cu a Si b B c Sn d (where a, b, c, d are atomic%, 0.3 ≦ a <1.55, 1 ≦ Amorphous alloy ribbon having a composition represented by b ≦ 10, 11 ≦ c ≦ 17, 0.25 <d ≦ 1.0, a + d ≦ 1.80) and formed by roll casting without heat treatment. And the crushing process to make an amorphous alloy powder
The crystallization heat treatment step B of subjecting the amorphous alloy powder to a heat treatment for nanocrystallization to obtain a nanocrystal alloy powder,
The compression molding step B in which the nanocrystallized nanocrystal alloy powder and the binder are mixed and compression molded to obtain a green compact.
A method for producing a nanocrystal alloy dust core having.
Alloy composition: Fe 100-a- bc -d Cu a Si b B c Sn d (where a, b, c, d are atomic%, 0.3 ≦ a <1.55, 1 ≦ Crystal grains having a composition represented by b ≦ 10, 11 ≦ c ≦ 17, 0.25 <d ≦ 1.0, a + d ≦ 1.80) and having a body-centered cubic structure having an average crystal grain size of 60 nm or less. A nanocrystalline alloy dust core containing an amorphous alloy powder having a structure dispersed in an amorphous matrix with a body integral ratio of 30% by volume or more, and having an alloy thin band surface and a fracture surface.