TWI778112B - Fe-BASED ALLOY, CRYSTALLINE Fe-BASED ALLOY ATOMIZED POWDER, AND MAGNETIC CORE - Google Patents

Abstract

An iron-based alloy is used for the manufacture of crystalline iron-based alloy powder, and has the alloy composition represented by the composition formula (1). In the composition formula (1), a, b, c, d, e, and α satisfy 0.1≦a≦1.5, 13.0≦b≦15.0, 8.0<c<12.0, 0.5≦d<4.0, 0≦e≦2.0, 10.0<c+d<13.5, 0≦α≦0.9, and 71.0≦100-abcde≦74.0. Fe _100-abcde Cu _a Si _b B _c (Mo _1-α Nb _α ) _d Cr _e … Compositional formula (1)

Description

Iron-based alloys, crystalline iron-based alloy powders and magnetic cores

The present disclosure relates to iron-based alloys, crystalline iron-based alloy powders, and magnetic cores.

Iron-based alloys in powder form, ie, iron-based alloy powders, have been known from the past. For example, Patent Document 1 discloses an iron-based soft magnetic alloy which is excellent in soft magnetic properties (especially high-frequency magnetic properties) and has low magnetostriction with little deterioration of properties due to impregnation, deformation, etc. Magnetic alloy, characterized by: having the general formula (Fe _1-a M _a ) _100-xyz-α Cu _x Si _y B _z M' _α (only, M is Co and/or Ni, and M' is selected from Nb, At least one element in the group consisting of W, Ta, Zr, Hf, Ti and Mo, a, x, y, z and α satisfy 0≦a≦0.5, 0.1≦x≦3, 0≦y≦30, respectively , 0≦z≦25, 5≦y+z≦30 and 0.1≦α≦30.) represent the composition, and at least 50% of the structure is composed of fine crystal grains. The ninth page of this patent document 1 discloses that the iron-based soft magnetic alloy is in powder form.

In addition, Patent Document 2 discloses a soft magnetic powder that can ensure high insulating properties between particles during powder compaction, which is characterized by having Fe _100-abcdef Cu _a Si _b B _c M _d M' _e X _f (atomic %) [However, M is at least one element selected from the group consisting of Nb, W, Ta, Zr, Hf, Ti and Mo, and M' is V, Cr, Mn, At least one element selected from the group consisting of Al, platinum group elements, Sc, Y, Au, Zn, Sn, and Re, and X is selected from the group consisting of C, P, Ge, Ga, Sb, In, Be, and As At least one element in the group, a, b, c, d, e and f satisfy 0.1≦a≦3, 0<b≦30, 0<c≦25, 5≦b+c≦30, 0.1≦d ≦30, 0≦e≦10, and 0≦f≦10. ], and contains more than 40% by volume of crystalline structure with a particle size of 1 nm to 30 nm, using a JIS standard sieve with a mesh of 45 μm, a JIS standard sieve with a mesh of 38 μm, and a JIS standard sieve with a mesh of 25 μm in order. During the classification process, if the particles that pass through the JIS standard sieve with a mesh size of 45 μm but do not pass through the JIS standard sieve with a mesh size of 38 μm are defined as the first particles, they pass through the JIS standard sieve with a mesh size of 38 μm but do not pass through the JIS standard sieve with a mesh size of 25 μm. If the particles passing through the JIS standard sieve with a mesh size of 25 μm are defined as the third particles, the coercive force Hc1 of the first particle, the coercive force Hc2 of the second particle, and the coercive force Hc3 of the third particle satisfy Hc2/Hc1 is 0.85 or more and 1.4 or less, and Hc3/Hc1 is 0.5 or more and 1.5 or less. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Laid-Open No. 64-079342 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-110256

[The problem to be solved by the invention]

As a method of obtaining iron-based alloy powder, the following method is sometimes used: First, an iron-based alloy powder (hereinafter, also referred to as amorphous iron-based alloy powder) substantially consisting of an amorphous phase is obtained by a pulverization method. Amorphous Fe-based alloy atomized powder), and then heat-treated the amorphous Fe-based alloy atomized powder to obtain Fe-based alloy powder obtained by crystallization of a part of the amorphous phase (below , also known as crystalline Fe-based alloy atomized powder (Crystalline Fe-based alloy atomized powder) (for example, refer to the embodiment of the above-mentioned Patent Document 2). However, in the conventional crystalline iron-based alloy powder, the coercive force may be too large in some cases. In addition, even when the crystalline iron-based alloy powder exhibits a small coercive force, the range of the median particle diameter d50 that exhibits the small coercive force may be narrow. Such a crystalline iron-based alloy powder has a problem that the degree of freedom of selection of the median particle diameter d50 is low.

The present disclosure is made in view of the above-mentioned circumstances. An object of one aspect of the present disclosure is to provide an iron-based alloy capable of producing a crystalline iron-based alloy pulverized powder exhibiting a broad range of the median particle diameter d50 of a small coercive force. Another aspect of the present disclosure is to provide a crystalline iron-based alloy powder that exhibits a broad range of median particle diameter d50 with a small coercive force. Another aspect of the present disclosure is to provide a magnetic core containing the above-mentioned crystalline iron-based alloy powder. [Means of Solving Problems]

Means for solving the above-mentioned problems include the following aspects. <1> An iron-based alloy, which is used in the production of crystalline iron-based alloy powder, and has an alloy composition represented by the following composition formula (1). Fe _100-abcde Cu _a Si _b B _c (Mo _1-α Nb _α ) _d Cr _e … Compositional formula (1) In compositional formula (1), a, b, c, d, e, and α satisfy 0.1≦a ≦1.5, 13.0≦b≦15.0, 8.0<c<12.0, 0.5≦d<4.0, 0≦e≦2.0, 10.0<c+d<13.5, 0≦α≦0.9, and 71.0≦100-abcde≦74.0. <2> The iron-based alloy according to <1>, wherein, in the composition formula (1), d satisfies 0.5≦d≦3.5. <3> The iron-based alloy according to <1> or <2>, wherein, in the composition formula (1), e satisfies 0.5<e≦2.0. <4> The iron-based alloy according to any one of <1> to <3>, wherein, in the composition formula (1), α satisfies 0<α≦0.9. <5> The iron-based alloy according to any one of <1> to <4>, wherein, in the composition formula (1), c satisfies 10.0≦c<12.0. <6> A crystalline iron-based alloy powder having an alloy composition represented by the following composition formula (1) and an alloy structure containing nanocrystalline grains with an average particle diameter of 40 nm or less. Fe _100-abcde Cu _a Si _b B _c (Mo _1-α Nb _α ) _d Cr _e … Compositional formula (1) In compositional formula (1), a, b, c, d, e, and α satisfy 0.1≦a ≦1.5, 13.0≦b≦15.0, 8.0<c<12.0, 0.5≦d<4.0, 0≦e≦2.0, 10.0<c+d<13.5, 0≦α≦0.9, and 71.0≦100-abcde≦74.0. <7> The crystalline iron-based alloy powder according to <6>, wherein the coercive force when a magnetic field of 40 kA/m is applied is 190 A/m or less. <8> The crystalline iron-based alloy powder according to <6> or <7>, wherein, in the composition formula (1), d satisfies 0.5≦d≦3.5. <9> The crystalline iron-based alloy powder according to any one of <6> to <8>, wherein, in the compositional formula (1), e satisfies 0.5<e≦2.0. <10> The crystalline iron-based alloy powder according to any one of <6> to <9>, wherein, in the composition formula (1), α satisfies 0<α≦0.9. <11> The crystalline iron-based alloy powder according to any one of <6> to <10>, wherein, in the compositional formula (1), c satisfies 10.0≦c<12.0. <12> A magnetic core, comprising: the crystalline iron-based alloy powder according to any one of <6> to <11>, and a binder for adhering the crystalline iron-based alloy powder; the binder is selected from Free epoxy resin, unsaturated polyester resin, phenolic resin, xylene resin, diallyl phthalate resin, polysiloxane resin, polyimide imide, polyimide, and water glass At least 1 species from the group. [Effect of invention]

According to an aspect of the present disclosure, there can be provided an iron-based alloy capable of producing an iron-based alloy pulverized powder exhibiting a wide range of the median particle diameter d50 of a small coercive force. According to another aspect of the present disclosure, an iron-based alloy pulverized powder exhibiting a broad range of median particle diameter d50 with a small coercive force can be provided. According to yet another aspect of the present disclosure, a magnetic core containing the above-mentioned iron-based alloy powder can be provided.

In this specification, the numerical range represented by "-" means the range which includes the numerical value described before and after "-" as a minimum value and a maximum value, respectively. In this specification, the term "step" includes not only an independent step, but also a case that cannot be clearly distinguished from other steps, as long as the intended purpose of the step can be achieved.

[Iron-Based Alloy] The iron-based alloy of the present disclosure is used in the production of crystalline iron-based alloy powder, and has an alloy composition represented by the composition formula (1) described later.

As described above, the crystalline iron-based alloy powder is produced by subjecting the amorphous iron-based alloy powder to heat treatment. Through the heat treatment, a part of the amorphous phase of the amorphous iron-based alloy powder is transformed into a crystalline phase, whereby a crystalline iron-based alloy powder can be obtained. The raw material of the powdered crystalline iron-based alloy powder, that is, the powdered amorphous iron-based alloy powder, is produced by a powdering method using a molten alloy having an alloy composition of the iron-based alloy as a raw material. Specifically, the amorphous iron-based alloy powder is obtained by pulverizing the above molten alloy into particles, and rapidly cooling the obtained particulate molten alloy (hereinafter, also referred to as "molten alloy particles"). And manufacture. The molten alloy having the alloy composition of the iron-based alloy can be produced by dissolving an ingot of the alloy composition of the iron-based alloy, or directly produced by dissolving and mixing each component (each element).

The iron-based alloy of the present disclosure is a raw material for crystalline iron-based alloy powder. The concept of iron-based alloys (ie, raw materials of crystalline iron-based alloy powders) of the present disclosure includes both amorphous iron-based alloy powders and raw materials (eg, ingots) of amorphous iron-based alloy powders By. In the present disclosure, the particles in the crystalline iron-based alloy powder are sometimes referred to as crystalline iron-based alloy powder particles, and the particles in the amorphous iron-based alloy powder are referred to as amorphous iron-based alloy powder particles.

By using the iron-based alloy of the present disclosure as a raw material, it is possible to manufacture a crystalline iron-based alloy exhibiting a small coercive force (eg, 190 A/m or less when a magnetic field of 40 kA/m is applied) and a wide range of median particle size d50. Alloy powder. Therefore, a crystalline iron-based alloy powder with a high degree of freedom of selection of the median particle size d50 can be obtained. The reason for obtaining this effect is considered to be because the iron-based alloy of the present disclosure has the alloy composition represented by the above-mentioned composition formula (1). It will be described in detail below.

Among the powdered particles of crystalline iron-based alloys, the coercive force of particles with large particle size may be larger than that of particles with small particle size. For its reasons, we consider the following reasons. The raw material of the crystalline iron-based alloy powder particles, ie, the amorphous iron-based alloy powder particles, is produced by rapidly cooling the molten alloy particles, as described above. At this time, since the specific surface area of the molten alloy particles of small particle size is large, the whole is rapidly cooled. Therefore, it is easy to obtain homogeneous and highly amorphous amorphous iron-based alloy powder particles from molten alloy particles of small particle size (ie, no crystal grains or extremely reduced crystal grains in the alloy structure). However, the large-diameter molten alloy particles have a small specific surface area, so the cooling rate tends to be relatively slow, and the cooling rate inside the particles tends to be slower than the cooling rate on the particle surface. As a result, amorphous iron-based alloy powder particles having an inhomogeneous amorphous phase or an amorphous phase in which crystal grains are partially precipitated may be obtained from molten alloy particles having a large particle size. When such amorphous iron-based alloy powder particles are heat-treated, coarse crystals are formed in the alloy structure, and as a result, the coercive force of the obtained crystalline iron-based alloy powder particles may increase. Regarding the above-mentioned problems, it is considered that since the iron-based alloy of the present disclosure has the alloy composition represented by the composition formula (1), the amorphous alloy in the stage of rapidly cooling the molten alloy particles is mainly due to the action of Si, B, and Mo. The cooling effect (hereinafter, also referred to as "rapid cooling effect") is excellent. Therefore, it is considered that when the iron-based alloy of the present disclosure is used, even from the molten alloy particles having a relatively large particle size, amorphous iron-based alloy powder particles that are homogeneous and highly amorphous can be easily obtained. As a result, it is considered that when the crystalline iron-based alloy powder obtained by heat-treating the amorphous iron-based alloy powder, the coercive force of the large particle size particles can be suppressed from becoming too large.

In addition, by using the iron-based alloy of the present disclosure as a raw material, the coercive force of the small particle size particles in the crystalline iron-based alloy powder can also be reduced. The reason for this is considered as follows. The crystalline iron-based alloy pulverized powder has a predetermined particle size distribution. It is considered that in the crystalline iron-based alloy powder, particles with small particle size are more susceptible to heat treatment than particles with large particle size. In this regard, the alloy composition represented by the composition formula (1) is excellent in the amorphization effect in the stage of rapidly cooling the molten alloy particles. Therefore, in terms of the alloy composition represented by the composition formula (1), in the stage of heat-treating the powdered amorphous iron-based alloy powder, the particles ranging from small particle size to large particle size in the powdered amorphous iron-based alloy powder are The amorphous structure of particles of various sizes is excellent in the effect of homogeneous crystallization. Therefore, it is considered that by using the iron-based alloy of the present disclosure as a raw material, the coercive force of the small particle size particles in the crystalline iron-based alloy powder can also be reduced.

Based on the above reasons, it is considered that by using the iron-based alloy of the present disclosure as a raw material, the median particle diameter d50 exhibiting a small coercive force (for example, a value of 190 A/m or less when a magnetic field of 40 kA/m is applied) can be produced. A wide range of crystalline iron-based alloy powders.

<Alloy composition represented by compositional formula (1)> The iron-based alloy of the present disclosure has an alloy composition represented by the following compositional formula (1). In addition, the alloy composition does not change during the process of obtaining the crystalline iron-based alloy powder from the iron-based alloy of the present disclosure. Therefore, the crystalline iron-based alloy powder obtained from the iron-based alloy of the present disclosure also has the alloy composition represented by the following composition formula (1).

Fe _100-abcde Cu _a Si _b B _c (Mo _1-α Nb _α ) _d Cr _e … Compositional formula (1) In compositional formula (1), a, b, c, d, e, and α satisfy 0.1≦a ≦1.5, 13.0≦b≦15.0, 8.0<c<12.0, 0.5≦d<4.0, 0≦e≦2.0, 10.0<c+d<13.5, 0≦α≦0.9, and 71.0≦100-abcde≦74.0.

(Fe) In the alloy composition represented by the composition formula (1), Fe is the main element constituting the iron-based alloy, and is an element that affects the saturation magnetization of the crystalline iron-based alloy powder. "100-a-b-c-d-e" in the composition formula (1) represents the Fe content (atomic %) in the alloy composition, and satisfies 71.0≦100-a-b-c-d-e≦74.0. When "100-a-b-c-d-e" is 71.0 or more, the saturation magnetization of the crystalline iron-based alloy powder is improved. When "100-a-b-c-d-e" is 74.0 or less, a crystalline iron-based alloy powder with a wide range of median particle diameter d50 exhibiting a small coercive force can be obtained.

(Cu) In the alloy composition represented by the composition formula (1), Cu is an important factor in the formation of nanocrystalline grains (also known as nanocrystals) in the stage of obtaining crystalline iron-based alloy powders by heat-treating amorphous iron-based alloy powders. That is, an element contributing to the formation of the bccFe-Si phase). "a" in the composition formula (1) represents the Cu content (atomic %) in the alloy composition, and satisfies 0.1≦a≦1.5. Thereby, the above-mentioned effect of adding Cu can be exerted, and the coercive force of the crystalline iron-based alloy powder can be reduced. When 0.1≦a is not satisfied (that is, when the content of Cu is less than 0.1 atomic %), the above-mentioned effect of adding Cu cannot be obtained. When a≦1.5 is not satisfied (that is, when the content of Cu exceeds 1.5 atomic %), the saturation magnetization of the crystalline iron-based alloy powder may decrease. In addition, when a≦1.5 is not satisfied, nuclei of nanocrystals are likely to be formed in the powdered amorphous iron-based alloy powder, and the nuclei will grow into coarse crystals due to heat treatment, and as a result, the powdered crystalline iron-based alloy powder may become There is a risk that the coercive force will become too large. Considering these viewpoints, "a" satisfies a≦1.5. "a" should satisfy a≦1.1, and more preferably satisfy a≦1.0.

(Si) In the alloy composition represented by the composition formula (1), Si contributes to the rapid cooling effect (that is, the effect of amorphization) in the stage of rapidly cooling the molten alloy particles, and by crystallizing the iron-based alloy Fe, which is the main component of the nanocrystalline grains, is solid-dissolved in the pulverized particles, and contributes to the reduction of magnetostriction and magnetic anisotropy. "b" in the composition formula (1) represents the Si content (atomic %) in the alloy composition, and satisfies 13.0≦b≦15.0. As a result, the coercive force of the crystalline iron-based alloy powder is reduced. When 13.0≦b is not satisfied (that is, when the content of Si is less than 13.0 atomic %), and when b≦15.0 is not satisfied (that is, when the content of Si exceeds 15.0 atomic %), amorphous iron bases will be obtained. The rapid cooling effect in the stage of powdering the alloy becomes small, and it is easy to precipitate coarse crystal grains of micron order. As a result, the coercive force of the crystalline iron-based alloy powder may become too large.

(B) In the alloy composition represented by the composition formula (1), B contributes to the rapid cooling effect in the stage of rapidly cooling the molten alloy particles, and by being solid-dissolved in the crystalline iron-based alloy powder particles in the system of nanometers Fe, which is the main component of crystal grains, contributes to the reduction of magnetostriction and magnetic anisotropy. "c" in the composition formula (1) represents the content of B (atomic %) in the alloy composition, and satisfies 8.0<c<12.0. Thereby, the coercive force of the crystalline iron-based alloy powder is reduced, and the saturation magnetization of the crystalline iron-based alloy powder is improved. When 8.0<c is not satisfied (that is, when the content of B is 8.0 atomic % or less), the rapid cooling effect in the stage of rapidly cooling the molten alloy particles may be reduced, and coarse crystal grains may be easily precipitated. As a result, the coercive force of the powdered crystalline iron-based alloy powder may become too large. When c<12.0 is not satisfied (that is, when the content of B is 12.0 atomic % or more), the proportion of B, which is a non-magnetic element, becomes high, so that the saturation magnetization of the crystalline iron-based alloy powder decreases.

Considering the viewpoint of broadening the range of the median particle size that exhibits a smaller coercive force, and the viewpoint of further improving the saturation magnetization, “c” in the composition formula (1) should satisfy 9.0≦c<12.0, and satisfy 10.0 ≦c<12.0 is better.

(Mo, Nb) In the alloy composition represented by the composition formula (1), Mo is an essential element, which contributes to the rapid cooling effect in the stage of rapidly cooling the molten alloy particles, and contributes to the rapid cooling effect in the crystalline iron-based alloy powder particles. The uniformity of the particle size of the nanocrystalline grains contributes. Therefore, in the crystalline iron-based alloy powder particles, Mo contributes to the effect of widening the range of the median particle diameter d50 that exhibits a small coercive force. In the alloy composition represented by the composition formula (1), Nb is an element contained arbitrarily. Nb has a similar effect to Mo, but has a poor effect of broadening the range of the median particle diameter d50 in which the crystalline iron-based alloy powder particles exhibit a small coercive force compared to Mo. The reason for this is not clear, but it is thought to be related to the tendency of Nb to promote the concentration of particles in the vicinity of the surface compared to Mo. "α" in the composition formula (1) means the ratio of the content of Nb to the total content of Mo and Nb. "α" satisfies 0≦α≦0.9. 0≦α≦0.9 means that Nb is not contained, or when Nb is contained, it means that the ratio of the content of Nb to the total content of Mo and Nb is 0.9 or less. As described above, Nb is less effective than Mo in widening the range of the median particle diameter d50 in which the crystalline Fe-based alloy powder particles exhibit a smaller coercive force. Therefore, when "α" in the composition formula (1) exceeds 0.9 (for example, when α=1.0, that is, when Mo is not contained but Nb is contained), there may be cases where the crystallized iron-based alloy powder exhibits a small amount of The case where the range of the median diameter d50 of the coercive force is narrowed.

"α" in the composition formula (1) preferably satisfies 0<α (that is, the alloy composition contains both of Mo and Nb). When 0<α is satisfied, the range of the median particle diameter d50 in which the crystalline iron-based alloy powder exhibits a smaller coercive force becomes wider. α is more preferably 0.1 or more, particularly preferably 0.2 or more. In addition, the upper limit of α is more preferably 0.8, still more preferably 0.6, and still more preferably 0.5.

"d" in the composition formula (1) represents the total content (atomic %) of Mo and Nb in the alloy composition, and satisfies 0.5≦d<4.0. Thereby, the range of the median particle diameter d50 in which the crystalline iron-based alloy powder particles exhibit a smaller coercive force is widened, and the saturation magnetization of the crystalline iron-based alloy powder particles is improved. When 0.5≦d is not satisfied (that is, when the total content of Mo and Nb is less than 0.5 atomic %), the above-described effect of adding Mo alone or the effect of adding Mo and Nb cannot be obtained. On the other hand, when d<4.0 is not satisfied (that is, when the total content of Mo and Nb is 4.0 atomic % or more), the Fe content decreases relatively, and as a result, the saturation magnetization of the crystalline iron-based alloy powder tends to decrease. . In detail, it is considered that the atomic weights of Mo and Nb are larger than those of other constituent elements (for example, Si, B, etc.), and therefore, when the content of Mo and Nb exceeds the upper limit, it is considered that the saturation magnetization will be affected compared with other constituent elements. Great impact.

As mentioned above, “d” in the composition formula (1) satisfies 0.5≦d<4.0, but from the viewpoint of further improving the saturation magnetization of the crystalline iron-based alloy powder, “d” in the composition formula (1) should preferably satisfy 0.5 ≦d≦3.5.

In the composition formula (1), "c" (that is, the content of B (atomic %)) and "d" (that is, the total content of Mo and Nb (atomic %)) satisfy 10.0<c+d< 13.5. Thereby, the range of the median particle diameter d50 exhibiting a smaller coercive force in the crystalline iron-based alloy powder particles is widened, and the saturation magnetization of the crystalline iron-based alloy powder particles is improved. When 10.0<c+d is not satisfied, the range of the median particle diameter d50 that exhibits a small coercive force in the crystalline iron-based alloy powder may be narrowed in some cases. When c+d<13.5 is not satisfied, the Fe content decreases relatively, and as a result, the saturation magnetization of the crystalline iron-based alloy powder may decrease.

(Cr) In the alloy composition represented by the composition formula (1), Cr is an element optionally contained. "e" in the composition formula (1) represents the content (atomic %) of Cr in the alloy composition, and satisfies 0≦e≦2.0. Thereby, the saturation magnetization of the crystalline iron-based alloy powder is improved. When e≦2.0 is not satisfied, the saturation magnetization of the crystalline iron-based alloy powder may be deteriorated in some cases. e may be 0 or may exceed 0 (ie, 0<e). When 0<e, the corrosion resistance of the crystalline iron-based alloy powder is further improved. In addition, when 0<e, Cr functions as a deoxidizer for removing O as an impurity, and as a result, the coercive force of the crystalline iron-based alloy powder is further reduced.

In the composition formula (1), e preferably satisfies 0.5<e≦2.0. Thereby, the corrosion resistance of the crystalline iron-based alloy powder is further improved, and the coercive force of the crystalline iron-based alloy powder becomes smaller.

For iron-based alloys, in addition to the alloy composition represented by the composition formula (1), impurities may also be contained. As an impurity, S (sulfur), O (oxygen), N (nitrogen), C (carbon), P (phosphorus) etc. are mentioned, for example. The content of S is preferably 200 mass ppm or less. The content of O is preferably 5000 mass ppm or less. The content of N is preferably 1000 mass ppm or less. The content of C is preferably 1000 mass ppm or less. The content of P is preferably 1000 mass ppm or less.

[Iron-Based Alloy Ingot] Next, an iron-based alloy ingot, which is one embodiment of the iron-based alloy disclosed in the present disclosure, will be described. The alloy composition of the iron-based alloy ingot of one aspect, as described above, is the alloy composition represented by the composition formula (1). An iron-based alloy ingot of one aspect can be produced, for example, by dissolving and mixing the raw materials of each element in the alloy composition represented by the composition formula (1) by a general method, and then cooling by a general method.

[Amorphous Iron-Based Alloy Powder] Next, an amorphous iron-based alloy powder that is another aspect of the iron-based alloy of the present disclosure will be described. The alloy composition of the amorphous iron-based alloy powder of one aspect, as described above, is the alloy composition represented by the composition formula (1). The alloy structure of the amorphous iron-based alloy powder in one aspect is substantially composed of an amorphous phase. However, the alloy structure of the amorphous iron-based alloy powder in one form may also contain a trace amount of crystalline phase.

<The content of crystal phase in the alloy structure> In the amorphous iron-based alloy powder, the content of the crystal phase in the alloy structure is preferably 2% by volume or less, more preferably 1% by volume relative to the entire alloy structure Below, it is especially preferable that it is substantially 0 volume %. When the content rate of the crystalline phase in the alloy structure in the amorphous iron-based alloy powder is 2% by volume or less, the crystalline iron-based alloy powder obtained by heat-treating the amorphous iron-based alloy powder can be obtained. Lower coercivity.

The content ratio (CP) of the crystalline phase in the alloy structure in the powdered amorphous iron-based alloy powder can be determined according to the broad diffraction pattern from the amorphous phase in the X-ray diffraction spectrum obtained by powder X-ray diffraction. The area (AA) and the area (AC) of the main peak with the largest diffraction intensity from the crystal phase were calculated according to the following formula. Content rate (CP) (volume %)=AC/(AC+AA)×100

In the present disclosure, the powder X-ray diffraction system is performed as follows. First, a powder to be measured (specifically, powdered amorphous iron-based alloy powder or powdered crystalline iron-based alloy powder) is pressed to prepare a sample for X-ray diffraction having a flat surface. Powder X-ray diffraction was performed on the flat surface of the prepared sample for X-ray diffraction to obtain an X-ray diffraction spectrum. For powder X-ray diffraction, an X-ray diffraction device using a Cu-Kα ray source (for example, RINT2000 manufactured by Rigaku) is used, and the 2θ is in the range of 20 to 60°C under the conditions of 0.02deg/step and 2step/sec carried out within.

<Median particle size d50> As mentioned above, by using the iron-based alloy of the present disclosure (for example, amorphous iron-based alloy powder) as a raw material, it is possible to manufacture and exhibit a small coercive force (for example, when a magnetic field of 40kA/ The value of m is 190A/m or less coercive force) and the median particle size d50 is a crystalline iron-based alloy powder with a wide range. It is believed that the heat treatment used to obtain the powdered crystalline iron-based alloy powder does not affect the particle size distribution of the powder. Therefore, it is considered that the median particle size d50 of the amorphous iron-based alloy powder is maintained even in the crystalline iron-based alloy powder obtained by heat-treating the amorphous iron-based alloy powder. The median particle diameter d50 (hereinafter, also simply referred to as "d50") of the powdered amorphous iron-based alloy powder is not particularly limited. The d50 of the amorphous iron-based alloy powder can be, for example, 3.0 μm or more and 35.0 μm or less.

If the d50 of the powdered amorphous iron-based alloy powder is 3.0 μm or more, the use of crystalline iron-based alloy powdered powder in the magnetic core (for example, powder magnetic core, metal composite magnetic core, etc.) can improve the iron-based alloy. The occupancy rate of particles can thereby improve the saturation magnetic flux density and magnetic permeability of the above-mentioned magnetic core. The d50 of the amorphous iron-based alloy powder is preferably 3.5 μm or more, more preferably 5.0 μm or more, and particularly preferably 8.5 μm or more. If the d50 of the powdered amorphous iron-based alloy is 35.0 μm or less, the eddy current loss can be reduced in the magnetic core made of the powdered crystalline iron-based alloy. Thereby, the core loss when using the above-mentioned magnetic core under the high frequency condition of 500 kHz or more, for example, can be reduced. The d50 of the amorphous iron-based alloy powder is preferably 28.0 μm or less, more preferably 20.0 μm or less.

In the present disclosure, the median diameter d50 refers to the volume-based median diameter obtained by the laser diffraction method. Hereinafter, an example of a method for measuring the median particle diameter d50 of an amorphous iron-based alloy powder by a laser diffraction method will be illustrated. Using a laser diffraction scattering particle size distribution analyzer (for example, LA-920 manufactured by Horiba Corporation), the representative particle size (μm) and the accumulation from the small particle size side were obtained for the entire amorphous iron-based alloy powder. Cumulative distribution curve of frequency (volume %) relationship (ie, cumulative distribution curve of volume basis). From the obtained cumulative distribution curve, the particle size corresponding to 50% by volume of the cumulative frequency was read, and the particle size was defined as the median particle size d50 of the powdered amorphous iron-based alloy powder.

<(d90-d10)/d50> The (d90-d10)/d50 of the amorphous iron-based alloy powder is preferably 1.00 or more and 4.00 or less. The smaller the numerical value of (d90-d10)/d50, the smaller the variation in particle size. About d50, it is as mentioned above. d10 means the particle size corresponding to 10 volume % of the cumulative frequency in the aforementioned cumulative distribution curve, and d90 means the particle size corresponding to 90 volume % of the cumulative frequency in the aforementioned cumulative distribution curve.

<Oxide film> The amorphous iron-based alloy powder may contain an oxide film on the surface layer portion of each particle. When the amorphous iron-based alloy powder in which the surface layer portion of each particle contains an oxide film is heat-treated, a crystalline iron-based alloy powder powder in which the surface layer portion of each particle contains an oxide film can be obtained.

When the amorphous iron-based alloy powder contains an oxide film, the amorphous iron-based alloy powder and the crystalline iron-based alloy powder obtained by heat-treating the amorphous iron-based alloy powder can be A rust preventive effect is obtained and useless oxidation is prevented. Thereby, the preservability of the powdered amorphous iron-based alloy powder and the powdered crystalline iron-based alloy powder is improved. In addition, when the amorphous iron-based alloy powder contains an oxide film, the insulation between particles in the crystalline iron-based alloy powder is improved, and as a result, the eddy current loss, which is one of the factors of core loss, is reduced. From the viewpoint of obtaining the effect of the above-mentioned oxide film more effectively, the thickness of the oxide film is preferably 2 nm or more.

In addition, the upper limit of the thickness of the oxide film is preferably 50 nm from the viewpoint of not easily hindering the effect of improving the magnetic properties by nano-crystallization and the formability of using the crystalline iron-based alloy powder to manufacture the magnetic core.

<An example of a method for producing amorphous iron-based alloy powder (production method A)> Hereinafter, an example of a production method for producing an amorphous iron-based alloy powder (hereinafter, referred to as "production method A") will be illustrated. Preparation method A includes the step of obtaining powdered amorphous iron-based alloy powder by a powdering method. The pulverization method, as described above, is a method of producing molten alloy powder by pulverizing the molten alloy into particles, and rapidly cooling the obtained molten alloy particles. According to the pulverization method, it is easy to form an amorphous iron-based alloy pulverized powder containing an oxide film in the surface layer portion.

In addition, according to the pulverization method, amorphous iron-based alloy powder particles having a shape surrounded by a curved surface (for example, a spherical shape, a nearly spherical shape, a teardrop shape, a gourd shape, etc.) can be obtained. Crystalline iron-based alloy powdered particles obtained by heat-treating the amorphous iron-based alloy powdered particles also have shapes surrounded by curved surfaces (for example, spherical, approximately spherical, teardrop-shaped, gourd-shaped, etc. ).

The pulverization method is not particularly limited, and known methods such as gas pulverization, water pulverization, disk atomization method, high-speed rotating water pulverization method, and high-speed combustion flame pulverization method can be used. In terms of the pulverization method, considering the ease of obtaining an amorphous iron-based alloy, it is desirable that the molten raw material has excellent micronization performance and can be processed at a speed of 10 ³ ℃/sec or more (more preferably 10 ⁵ ℃/sec or more). Cooled pulverization method.

In the water pulverization method, the molten raw material flowing down is made into powder by high-pressure water sprayed from a nozzle, and the powdery molten raw material is cooled by using the high-pressure water to obtain non-ferrous powder. A method of pulverizing a crystalline iron-based alloy powder (hereinafter, also simply referred to as "powder"). The gas pulverization method is a method of obtaining powder by powdering a molten raw material with an inert gas ejected from a nozzle, and cooling the powdered molten raw material. The cooling in the gas pulverization method includes cooling with high-pressure water, cooling with a water tank provided in the lower part of the pulverizing apparatus, cooling with dropping into flowing water, and the like. For the high-speed rotating water pulverization method, a cooling container with a cylindrical inner peripheral surface is used, and the cooling liquid flows down while rotating along the inner peripheral surface to form a layered cooling liquid layer, and the molten raw material is discharged. A method of obtaining powder by falling into the cooling liquid layer, pulverizing it, and cooling it. As far as the high-speed combustion flame pulverization method is concerned, the molten raw material is made into powder by using a high-speed burner to spray the flame at a supersonic speed or near the speed of sound and in the form of a flame jet. A method of obtaining powder by cooling the molten raw material in powder form using a rapid cooling mechanism using water or the like as a cooling medium. Regarding the high-speed combustion flame pulverization method, for example, Japanese Patent Laid-Open No. 2014-136807 can be referred to.

Considering that the cooling efficiency is excellent and the amorphous iron-based alloy can be obtained relatively easily, the pulverization method is preferably a rotary disk pulverization method, a high-speed rotating water pulverization method, or a high-speed combustion flame pulverization method. In addition, when using the water pulverization method or the gas pulverization method, it is preferable to use high-pressure water exceeding 50 MPa.

[Crystalline iron-based alloy powder] The crystalline iron-based alloy powder of the present disclosure has the alloy composition represented by the aforementioned composition formula (1), and has an alloy structure containing nanocrystalline grains with an average particle diameter of 40 nm or less.

The crystalline iron-based alloy pulverized powder of the present disclosure exhibits a small coercive force and a wide range of median particle size d50. The reason for obtaining this effect is considered to be because the crystalline iron-based alloy powder of the present disclosure has the alloy composition represented by the above-mentioned composition formula (1). The details are as described above. The preferred aspect of the alloy composition of the crystalline iron-based alloy powder of the present disclosure is the same as the preferred aspect of the alloy composition of the iron-based alloy of the present disclosure.

<Nanocrystalline grains> In the crystalline iron-based alloy powder of the present disclosure, when the average particle diameter of the nanocrystalline grains is 40 nm or less, the coercive force is reduced. When the average particle size of the nanocrystal grains exceeds 40 nm, it becomes difficult to adjust the particle size of the nanocrystal grains, and the coercive force becomes large. The average particle diameter of the nanocrystal grains is preferably 35 nm or less, more preferably 30 nm or less.

On the other hand, the average particle diameter of the nanocrystalline particles is preferably 5 nm or more. Thereby, desired magnetic properties can be easily obtained.

In the present disclosure, the average particle diameter of the nanocrystal grains is obtained as follows. Nanocrystal grains have a fine crystal structure, and one nanocrystal grain is considered to be a single crystal. Therefore, in this specification, the size of the crystal grains is treated as the average particle diameter of the nanocrystal grains. Specifically, first, the powdered crystalline iron-based alloy powder of the present disclosure is crushed to prepare a sample for X-ray diffraction having a flat surface. Powder X-ray diffraction was performed on the flat surface of the prepared sample for X-ray diffraction to obtain an X-ray diffraction spectrum. For powder X-ray diffraction, an X-ray diffraction device using a Cu-Kα ray source (for example, RINT2000 manufactured by Rigaku) is used, and the 2θ is in the range of 20 to 60°C under the conditions of 0.02deg/step and 2step/sec carried out within. Using the peak portion of bccFe-Si [diffraction plane (110)] in the obtained X-ray diffraction spectrum, the crystal grain size D was determined according to the Scherrer formula shown below. The size D of the crystal grains obtained is defined as the average particle diameter of the nanocrystal grains.

D=(K･λ)/(βcosθ) … The Scherrer formula D represents the size of the crystal grains, K represents the Scherrer constant, specifically 0.9, λ represents the wavelength of the X-ray, and β represents the diffraction surface (110) The full width at half maximum of the peak portion, θ represents the Bragg angle (Bragg angle: half of the diffraction angle 2θ).

In the examples to be described later, for all the samples, the main peak with the largest diffraction intensity in the X-ray diffraction spectrum is around 2θ=45°, and is the peak portion of bccFe-Si [diffraction surface (110)] .

As described above, the nanocrystal grains contain bccFe-Si. The nanocrystalline particles may further contain FeB-based compounds.

<Content rate of crystal phase in alloy structure> In the crystalline iron-based alloy powder of the present disclosure, the content rate of crystal phase in the alloy structure is preferably 30% by volume or more with respect to the entire alloy structure. The concept of the crystalline phase referred to herein includes the aforementioned nanocrystalline grains. When the content rate of the crystal phase in the alloy structure is 30% by volume or more, the magnetostriction of the crystalline iron-based alloy powder can be further reduced. The upper limit of the content of the crystal phase in the alloy structure is not particularly limited. Magnetostriction is sometimes also affected by the balance between the crystalline phase and the amorphous phase. Taking this into consideration, the upper limit of the content of the crystal phase in the alloy structure may be, for example, 95% by volume, or 90% by volume or less.

The method for measuring the content of the crystal phase in the alloy structure of the powdered crystalline iron-based alloy powder is the same as the method for measuring the content of the crystal phase in the alloy structure of the powdered amorphous iron-based alloy powder.

<Coercive force> In the crystalline iron-based alloy powder of the present disclosure, the coercive force when a magnetic field of 40 kA/m is applied is preferably 190 A/m or less, more preferably 130 A/m or less, and particularly preferably 60 A/m or less. The lower limit of the coercive force when a magnetic field of 40 kA/m is applied is not particularly limited. Considering the manufacturing suitability of the crystalline iron-based alloy powder of the present disclosure, the lower limit may be 5 A/m or 10 A/m. In addition, applying a magnetic field of 40 kA/m corresponds to applying a magnetic field of 500 Oe.

<Saturation Magnetization> In the crystalline iron-based alloy powder of the present disclosure, the saturation magnetization when a magnetic field of 800 kA/m is applied is preferably 110 emu/g or more. In addition, in the crystalline iron-based alloy powder of the present disclosure, the upper limit of the saturation magnetization when a magnetic field of 800 kA/m is applied depends on the compositional amount of Fe.

<Median particle size d50> As mentioned above, the crystalline iron-based alloy powder of the present disclosure exhibits a small coercive force (for example, a coercive force below 190 A/m when a magnetic field of 40 kA/m is applied) The range of particle size d50 is wide. Therefore, the d50 of the crystalline iron-based alloy powder of the present disclosure is not particularly limited. Examples and preferred ranges of d50 in the crystalline iron-based alloy powder of the present disclosure are respectively the same as the examples and preferred ranges of d50 in the aforementioned amorphous iron-based alloy powder.

<(d90-d10)/d50> The preferred range of (d90-d10)/d50 in the crystalline iron-based alloy powder of the present disclosure is the same as that of (d90-d10) in the aforementioned amorphous iron-based alloy powder The preferred range of /d50 is the same.

<Oxide Film> The crystalline iron-based alloy powder of the present disclosure may contain an oxide film on the surface layer portion of each particle. The effect obtained by containing the oxide film is as described in the item of the amorphous iron-based alloy powder. The preferred thickness of the oxide film that can be contained in the crystalline iron-based alloy powder of the present disclosure is the same as the preferred thickness of the oxide film that can be contained in the amorphous iron-based alloy powder.

<Preferred Application> The crystalline iron-based alloy powder of the present disclosure described above is particularly suitable as a material for magnetic cores. As a magnetic core, a powder magnetic core, a metal composite magnetic core, etc. are mentioned.

The magnetic core obtained by powdering the crystalline iron-based alloy powder of the present disclosure can be ideally used in inductors, noise filters, choke coils, transformers, reactors, and the like.

As mentioned above, the crystalline Fe-based alloy powders of the present disclosure can achieve a small coercive force in a wide range of d50. Therefore, when the crystalline iron-based alloy powder of the present disclosure is used as the raw material of the magnetic core, the degree of freedom of selection of the raw material of the magnetic core (specifically, the degree of freedom of selection of d50) increases. In addition, the crystalline iron-based alloy powder of the present disclosure has a small coercive force, and thus contributes to the improvement of characteristics of inductors, noise filters, choke coils, transformers, reactors, and the like.

<Example of Production Method of Crystalline Iron-Based Alloy Powder (Production Method X)> Hereinafter, an example of a production method (hereinafter referred to as "Production Method X") for producing the crystalline iron-based alloy powder of the present disclosure will be illustrated. The manufacturing method X includes the following steps: obtaining the crystalline iron-based alloy powder of the present disclosure by applying heat treatment to the amorphous iron-based alloy powder which is one aspect of the iron-based alloy of the present disclosure.

A preferred aspect of the step of obtaining the crystalline iron-based alloy powder of the present disclosure is as follows: the aforementioned amorphous iron-based alloy powder, which is one aspect of the iron-based alloy of the present disclosure, is applied in sequence. The crystalline iron-based alloy powder of the present disclosure is obtained by classifying and heat-treating, or applying heat-treatment and classification in sequence. In this aspect, classification may be performed before the heat treatment, or may be performed after the heat treatment. When classification is performed before heat treatment, classification may also be performed after heat treatment (ie, classification, heat treatment, and classification may be applied in this order).

As mentioned above, for the crystalline iron-based alloy powder of the present disclosure, it exhibits a small coercive force (for example, a coercive force with a value of 190 A/m or less when a magnetic field of 40 kA/m is applied) that is less than the median particle size d50 Broad range. This effect is obtained due to the alloy composition in the iron-based alloy as the raw material (that is, the alloy composition represented by the composition formula (1)). Therefore, even if the step of obtaining the crystalline iron-based alloy pulverized powder of the present disclosure includes classification, the particles removed by classification can be reduced. Therefore, the production method X is a method for producing a crystalline iron-based alloy powder with excellent productivity.

(Heat Treatment) The conditions of the heat treatment can be appropriately adjusted so that the average particle diameter of the nanocrystalline grains in the crystalline iron-based alloy powder particles obtained by the heat treatment is 40 nm or less. The heat treatment can be carried out using, for example, a known heating furnace such as a batch type electric furnace and a mesh belt type continuous electric furnace.

The adjustment of the heat treatment conditions can be performed, for example, by adjusting the rate of temperature increase, the maximum attained temperature (holding temperature), the holding time at the maximum attained temperature, and the like. The heating rate is, for example, 1°C/h to 200°C/h, preferably 3°C/h to 100°C/h. The maximum attained temperature (holding temperature) also depends on the crystallization temperature of the alloy structure of the amorphous iron-based alloy powder particles to be heat-treated (that is, the alloy structure substantially composed of an amorphous phase), and is, for example, 450℃～ 550℃, preferably 470℃～520℃. The holding time at the highest attained temperature is, for example, 1 minute to 3 hours, preferably 30 minutes to 2 hours.

The crystallization temperature of the alloy structure of the amorphous iron-based alloy powder particles can be determined by using a differential scanning calorimeter (DSC: Differential Scanning Calorimeter). The heating rate of /hr was obtained by thermal analysis.

The environment in which the heat treatment is performed is not particularly limited. The environment in which the heat treatment is performed includes an atmospheric environment, an inert gas (nitrogen, argon, etc.) environment, a vacuum environment, and the like.

The method of cooling the crystalline iron-based alloy pulverized powder obtained by the heat treatment is not particularly limited. As a cooling method, furnace cooling, air cooling, etc. are mentioned. In addition, the crystalline iron-based alloy powder obtained by heat treatment may be forcibly cooled by spraying a passivating gas.

(Classification) As the method of classification, the method implemented using a sieve, the method implemented using a classification apparatus, the method of combining these, etc. are mentioned. As a classification apparatus, well-known classification apparatuses, such as a centrifugal force type air-flow type classifier and an electromagnetic sieve shaker, are mentioned, for example. In the centrifugal force type airflow classifier, for example, d50, the ratio of particles having a particle size of 2 μm or less, etc. are adjusted by adjusting the rotational speed and air volume of the classifying rotor. In the electromagnetic sieve vibrator, for example, by appropriately selecting the mesh of the sieve, d50, the ratio of particles having a particle diameter of 2 μm or less, and the like are adjusted.

In powder classification using a centrifugal force type air classifier, the powder to be classified is subjected to centrifugal force due to eddy currents formed by the high-speed rotating classification rotor, and resistance to airflow supplied from an external blower. Thereby, the above-mentioned powder is divided into a group of large particles with a significant effect of centrifugal force, and a group of small particles with a significant effect of resistance. Centrifugal force can be adjusted by changing the rotational speed of the classification rotor, and resistance can be easily adjusted by changing the air volume from the blower. By adjusting the balance between centrifugal force and resistance, the powder can be classified into a predetermined particle size. When the above-mentioned group of small particles is recovered, the group of large particles is removed from the above-mentioned powder. Hereinafter, the grading of this aspect is also referred to as "overcut". When the above-mentioned large particle group is recovered, the small particle group is removed from the above-mentioned powder. Hereinafter, the grading of this aspect is also referred to as "undercut".

The classification preferably includes a first classification performed using a sieve and a second classification performed using a centrifugal force type airflow classifier after the first classification. The second classification in this aspect preferably includes overcutting, more preferably includes both overcutting and undercutting, and particularly preferably includes an operation of performing overcutting and undercutting in sequence.

The mesh of the sieve in the first classification can be appropriately selected. From the viewpoint of further reducing the time required for the first classification, the pore size is, for example, 90 μm or more, preferably 150 μm or more, and particularly preferably 212 μm or more. The upper limit of the pore size is, for example, 300 μm, preferably 250 μm, from the viewpoint of further reducing the load applied to the device used for the second classification. The pore mesh in this manual refers to the nominal pore mesh specified in JIS Z8801-1. In the second classification, the rotational speed of the classification rotor of the centrifugal force type air classifier is, for example, 500 rpm (revolution per minute) or more, preferably 1000 rpm or more. The upper limit of the rotation speed of the classification rotor also depends on the performance of the centrifugal force type airflow classifier, but the higher the rotation speed, the more small-diameter particles in the powder. In the second classification, the supply speed of the powder to be supplied to the centrifugal air classifier is, for example, 0.5 kg/h or more, preferably 1 kg/h or more, and particularly preferably 2 kg/h or more. The upper limit of the powder feeding speed depends on the classification processing capacity of the centrifugal force type airflow classifier. In the second classification, the air volume of the air flow in the centrifugal air classifier is, for example, 0.5 m ³ /s or more, preferably 1.0 m ³ /s or more, and particularly preferably 2.0 m ³ /s or more. The upper limit of the airflow volume depends on the capacity of the blower of the centrifugal force type airflow classifier.

[Magnetic Core] The magnetic core of the present disclosure contains the crystalline iron-based alloy powder of the present disclosure, and a binder for adhering the crystalline iron-based alloy powder. As far as the adhesive is concerned, it is preferably selected from epoxy resin, unsaturated polyester resin, phenolic resin, xylene resin, diallyl phthalate resin, polysiloxane resin, polyamide imide, polyamide At least one kind selected from the group consisting of imine and water glass.

In the magnetic core of the present disclosure, relative to 100 parts by mass of the crystalline iron-based alloy powder, the content of the binder is preferably 1 part by mass to 10 parts by mass, more preferably 1 part by mass to 7 parts by mass, and 1 part by mass to 5 parts by mass is particularly preferred. When the content of the binder is 1 part by mass or more, the insulation between particles and the strength of the magnetic core are further improved. When the content of the binder is 10 parts by mass or less, the magnetic properties of the magnetic core are further improved.

The shape of the magnetic core of the present disclosure is not particularly limited, and can be appropriately selected according to the purpose. The shape of the magnetic core of the present disclosure includes a ring shape (for example, a circular ring shape, a rectangular frame shape, etc.), a rod shape, and the like.

The magnetic core of the present disclosure can be manufactured, for example, by the following method. A formed body is obtained by filling the mixture of the powdered crystalline iron-based alloy powder of the present disclosure and the binder into a forming die, and pressing with a forming pressure of about 1-2 GPa using a hydraulic press forming machine or the like. The mixture may further contain lubricants such as zinc stearate. A magnetic core is obtained by heat-treating the obtained molded body at a temperature of, for example, 200° C. to less than the crystallization temperature for about 1 hour to harden the binder. The heat treatment environment at this time may be a passive gas environment or an oxidizing gas environment.

The metal composite magnetic core, which is an example of the magnetic core of the present disclosure, can be manufactured by, for example, burying the coil in the mixture of the powdered crystalline iron-based alloy powder and the binder of the present disclosure, and molding it into one piece. The integral molding can be performed by a known molding method such as injection molding.

In addition, the magnetic core of the present disclosure may also contain other metal powders than the crystalline iron-based alloy powder of the present disclosure. Examples of other metal powders include soft magnetic powders, and specific examples thereof include amorphous iron-based alloy powders, pure Fe powders, Fe—Si alloy powders, Fe—Si—Cr alloy powders, and the like. Compared with the d50 of the crystalline iron-based alloy powder of the present disclosure, the d50 of other metal powders can be smaller, larger, or the same, and can be appropriately selected according to the purpose. [Example]

Hereinafter, although the Example of this disclosure is illustrated, this disclosure is not limited to the following Example.

[Sample Nos. 1 to 28] <Preparation of ingot> Fe, Cu, Si, B, and at least one of Nb and Mo, and Cr were weighed as raw materials, placed in an alumina crucible, and placed in In the vacuum chamber of the high-frequency induction heating device, the vacuum chamber is evacuated. Then, each raw material was melted and mixed by high-frequency induction heating in an inert gas atmosphere (Ar) in a reduced pressure state, and then cooled to obtain ingots having the following alloy compositions A to G. The composition of each ingot was analyzed by ICP emission analysis. Among the alloy compositions A to G, the alloy compositions A and D are the alloy compositions of the comparative example which are not included in the alloy composition represented by the composition formula (1), and the other alloy compositions are included in the alloys represented by the composition formula (1). The alloy compositions of the examples within the composition range.

(Alloy Compositions A to G) A (Comparative Example): Fe _74.4 Cu _1.0 Si _13.5 B _7.6 Nb _2.5 Cr _1.0 B (Example): Fe _72.5 Cu _1.0 Si _13.5 B _9.0 Mo _3.0 Cr _1.0 C (Example): Fe _72.5 Cu _1.0 Si _13.5 B _11.0 Mo _1.0 Cr _1.0 D (Comparative Example): Fe _72.5 Cu _1.0 Si _13.5 B _9.0 Nb _3.0 Cr _1.0 E (Example): Fe _72.5 Cu _1.0 Si _13.5 B _9.0 Mo _1.5 Nb _1.5 Cr _1.0 F (Example): Fe _73.0 Cu _1.0 Si _13.5 B _9.0 Mo _1.3 Nb _1.5 Cr _0.7 G (Example): Fe _71.0 Cu _1.0 Si _15.5 B _9.0 Mo _1.3 Nb _1.3 Cr _1.0

Fe _100-abcde Cu _a Si _b B _c (Mo _1-α Nb _α ) _d Cr _e … Compositional formula (1) In compositional formula (1), a, b, c, d, e, and α satisfy 0.1≦a ≦1.5, 13.0≦b≦15.0, 8.0<c<12.0, 0.5≦d<4.0, 0≦e≦2.0, 10.0<c+d<13.5, 0≦α≦0.9, and 71.0≦100-abcde≦74.0.

In addition, the operation of the subsequent steps hardly affects the composition of the iron-based alloy. Therefore, it is considered that the composition of the ingot is maintained even in the powdered amorphous iron-based alloy powder and the powdered crystalline iron-based alloy powder.

<Production of amorphous iron-based alloy powder> The ingot is remelted at 1300 to 1700° C., and the obtained molten alloy is powderized by a pulverization method, thereby obtaining a non-crystalline iron-based alloy particle composed of amorphous iron-based alloy particles. Crystalline iron-based alloy powder. Here, regarding the pulverization method, the water pulverization method was used for the alloy compositions A to D, and the high-speed combustion flame pulverization method was used for the alloy compositions E to G. In the water pulverization method, the temperature of water, which is the spray medium, was set to 20° C., and the spray pressure of the water was set to 100 MPa. In addition, in the high-speed combustion flame pulverization method, the temperature of the flame injection from the injection member was set to 1300° C., and the dropping speed of the molten alloy as the raw material was set to 5 kg/min. Water is used as a cooling medium, and the cooling medium (water) is sprayed into a liquid mist by a cooling member. The cooling rate of the molten alloy was adjusted by setting the spray amount of water to be 4.5 liters/min to 7.5 liters/min.

<Classification> The amorphous iron-based alloy powder obtained above (amorphous iron-based alloy powder before classification) was classified as follows, and each sample in Table 1 was obtained. Sample Nos. 5, 6, 11, and 16 are samples to which only the following first classification (ie, classification using a sieve) was performed. Samples Nos. 1 to 4, 7 to 10, 12 to 15, and 17 to 28 were samples to which the following first classification and the following second classification were performed in this order.

(Classification using a sieve (first classification)) First, as the first classification common to all samples, the amorphous iron-based alloy powder before the classification obtained above was passed through a sieve with a mesh size of 250 μm. Coarse particle groups are removed from the amorphous iron-based alloy pulverized powder.

The amorphous iron-based alloy powder after the first classification is mixed with resin, and the obtained mixture is hardened. A smooth surface is formed by subjecting the obtained hardened material to polishing and ion milling. Parts where amorphous iron-based alloy particles exist in the obtained smooth surface were observed with a transmission electron microscope (TEM: Transmission Electron Microscope) at a magnification of 500,000, and composition mapping was performed. As a result, in the amorphous iron-based alloy particles in all the samples, it was confirmed that an oxide film having a thickness of 2 nm or more and 30 nm or less was present on the surface layer portion of the particles. In addition, the oxide film was identified by Ojie electron spectroscopy (JAMP-7830F, manufactured by JEOL Ltd.), and as a result, the oxide film in all the samples contained Fe, Si, Cu, and B.

(Classification by Centrifugal Type Air Type Classifier (Second Classification)) In Sample Nos. 1 to 4, 7 to 10, 12 to 15, and 17 to 28, a centrifugal force type airflow type classifier (Nissin Engineering Co., Ltd.) was used. TC-15) was prepared, and the amorphous iron-based alloy powder after the first classification was subjected to the second classification. Specifically, the air volume of the blower, the rotational speed of the classification rotor, and the powder supply speed were adjusted as shown in Table 1, and the second classification of the overcut state was used to powder the amorphous iron-based alloy after the first classification. Powder removes groups of large particles.

<Various Measurements> For each sample after classification, d10, d50, d90, and (d90-d10)/d50 were determined by the aforementioned methods. In addition, for each sample, X-ray diffraction by powder X-ray diffraction was measured under the measurement conditions described in the item "Crystal phase content in the alloy structure" in the item "Amorphous iron-based alloy powder". Ray Diffraction Spectroscopy. In the X-ray diffraction spectrum, when there is a diffraction peak portion derived from the crystal phase, it is judged as "presence" of the crystal phase, and when there is no diffraction peak portion derived from the crystal phase, it is judged as "absence" of the crystal phase. The above results are shown in Table 1.

[Table 1]

Furthermore, each sample after classification (that is, classified amorphous iron-based alloy particles) was observed at 100 to 5000 magnifications using a scanning microscope (SEM: Scanning Electron Microscope, S-4700 manufactured by Hitachi, Ltd.). As a result, the shape of each particle in each sample was a shape surrounded by a curved surface. Specifically, all the samples contained spherical particles, approximately spherical particles, teardrop-shaped particles, and gourd-shaped particles.

Using a differential scanning calorimeter (DSC8270 manufactured by Rigaku), each of the classified samples (ie, the classified amorphous iron-based alloy powder particles) was heated at a rate of 10°C/min to obtain a DSC curve. The crystallization temperature of each sample was determined from the obtained DSC curve. The results are shown in Table 2.

In addition, the following heat treatment hardly affects the particle size distribution of the particles. Therefore, it is considered that the particle size distribution (specifically, d10, d50, d90, and (d90-d10)/d50) of each sample after classification is maintained in each sample after heat treatment.

<Heat treatment> Using an electric heat treatment furnace, each sample after classification (except sample No. 10) was subjected to the conditions (heating rate, holding temperature KT, holding time, environment, and oxygen concentration) shown in Table 2. heat treatment. This heat treatment was performed by placing 10 g of each sample (except for sample No. 10) in a crucible made of alumina, and placing the crucible in an electric heat treatment furnace. Here, the holding temperature KT means the highest reached temperature in the heat treatment, and the holding time means the time held at the highest reaching temperature (ie, the holding temperature KT). The heat treatment in the N ₂ environment is carried out while introducing N ₂ gas into the electric heat treatment furnace. The oxygen concentration means the oxygen concentration (vol %) in the environment of the heat treatment. The oxygen concentration was measured using an oxygen concentration meter arranged in an electric heat treatment furnace. The oxygen concentration in the N ₂ environment was adjusted by adjusting the flow rate of N ₂ gas introduced into the electric heat treatment furnace. After the heat treatment (specifically, after the holding time), the heating of the electric heat treatment furnace was stopped, and each sample (except for sample No. 10) was furnace-cooled.

By the above heat treatment, crystalline iron-based alloy powders were obtained in the form of samples after heat treatment (except for sample No. 10). The above-mentioned heat treatment was not performed on the sample No. 10 after classification (that is, the amorphous iron-based alloy powder). In Table 2, sample No. 10 is used as a reference example.

<Measurement of the average particle size of nanocrystal grains> For each sample after heat treatment (except for sample No. 10), the average particle size of the nanocrystal grains contained in the structure of the particles was measured by the aforementioned method ( nm). The results are shown in Table 2.

In addition, for each of the samples after heat treatment (except for sample No. 10), the content of the crystal phase in the alloy structure of the crystalline iron-based alloy powder was measured by the method described above. As a result, the content of the crystal phase in the alloy structure of the crystalline iron-based alloy powder in all the samples was in the range of 50 to 80% by volume.

<Measurement of saturation magnetization and coercive force> For each sample after heat treatment, a magnetic measurement was performed to obtain a hysteresis loop, and from the obtained hysteresis loop, the saturation magnetization ( emu/g), and the coercive force (A/m) when a magnetic field of 40kA/m is applied. The magnetic measurement system was implemented using VSM (Vibrating Sample Magnetometer, VSM-5 manufactured by Toei Industries). The results are shown in Table 2.

[Table 2]

As shown in Table 2, it was confirmed that the saturation magnetization of the Examples and Comparative Examples were both 110 emu/g or more.

Then, based on the results in Table 2, the relationship between d50 and coercive force was graphed for each alloy composition (A to G) of the crystalline iron-based alloy powder. FIG. 1 is a graph showing the relationship between d50 and coercive force for each alloy composition (A to G) in crystalline iron-based alloy powder. In FIG. 1 , A to G mean alloy compositions A to G, respectively.

In addition, according to FIG. 1 , the breadth (probable value) of the range of d50 exhibiting coercive force of 190 A/m or less was estimated according to the following formula for the alloy composition (A to G) of each crystalline iron-based alloy powder. The results are shown in Table 3. The breadth of the range of d50 exhibiting coercive force below 190A/m (approximate value) = the maximum value of d50 exhibiting coercive force below 190A/m - the minimum value of d50 exhibiting coercive force below 190A/m.

[table 3]

As shown in FIG. 1 and Table 3, it was confirmed that the crystalline iron-based alloy powders of the examples (that is, the crystalline iron-based alloy powders obtained from the iron-based alloys having the alloy compositions B, C, and E to G) powder) compared to the crystalline iron-based alloy pulverized powder of the comparative example (that is, the crystalline iron-based alloy pulverized powder obtained from the iron-based alloy having the alloy compositions A and D), the former exhibited a coercive force below 190 A/m The range of d50 is wider. In addition, as shown in FIG. 1 , it was confirmed that the crystalline iron-based alloy powder of the example had a smaller minimum value of coercive force than the crystalline iron-based alloy powder of the comparative example.

Specifically, the alloy composition A (comparative example) is a composition that does not contain Mo, the B content does not reach the lower limit, and the Fe content exceeds the upper limit. That is, the alloy composition A does not satisfy 71.0≦100-a-b-c-d-e≦74.0, 0≦α≦0.9, and 8.0<c<12.0 in the composition formula (1). As shown in FIG. 1 and Table 3, in the alloy composition A (Comparative Example), the breadth of the range of d50 exhibiting a coercive force of 190 A/m or less was 0 μm (that is, there was no coercive force exhibiting a coercive force of 190 A/m or less). d50). Compared with the alloy composition A (comparative example), the Fe content and the B content of the alloy composition D (comparative example) satisfy the regulations, but Mo is not contained. That is, the alloy composition D satisfies 71.0≦100-a-b-c-d-e≦74.0 and 8.0<c<12.0 in the composition formula (1), but does not satisfy 0≦α≦0.9. In alloy composition D (Comparative Example), although there is a range of d50 exhibiting a coercive force of 190 A/m or less, the range of d50 exhibiting a coercive force of 190 A/m or less is narrower than that of the Example group. The alloy composition B (Example) is a composition in which Nb in the alloy composition D (Comparative Example) is replaced by Mo with the same atomic %. Compared with the alloy composition D (comparative example), the alloy composition B (Example) exhibits a wider range of d50 in which the former exhibits a coercive force of 190 A/m or less.

The alloy composition C (Example) is a composition in which the B content is increased and the Mo content is decreased as compared with the alloy composition B (Example). Compared with alloy composition B (Example), alloy composition C (Example) exhibits a wider range of d50 of coercive force below 190 A/m. In addition, as can be seen from Table 2, the saturation magnetization of the alloy composition C (Example) is also superior to that of the alloy composition B (Example). The alloy composition E (Example) is a composition in which a part of Mo in the alloy composition B (Example) is replaced by Nb. The alloy composition E (Example) exhibits a wider range of d50 of coercive force below 90 A/m than that of the alloy composition B (Example).

<Evaluation of Magnetostriction Constant> Regarding powder, it is difficult to directly measure the magnetostriction constant. Therefore, the measurement of the magnetostriction constant was carried out for the thin ribbon with the same structure as that of the powdered crystalline iron-based alloy powder, as a substitute test for estimating the magnetostrictive constant of the powdered powdered crystalline iron-based alloy powder. Specifically, an amorphous iron-based alloy ribbon having a thickness of 15 μm and a width of 5 mm was produced by a single roll method using ingots having the respective alloy compositions A to G. Rapid cooling in the single roll method is carried out in Ar gas. By subjecting the obtained amorphous iron-based alloy thin strip to heat treatment under the conditions shown in Table 4, a crystalline iron-based alloy thin strip was obtained.

[Table 4]

The obtained crystalline iron-based alloy thin strips all contain nanocrystalline grains with an average particle diameter of 40 nm or less in the range of 50% to 80% by volume. The magnetostrictive constants of each crystalline iron-based alloy thin strip were measured, and the results showed that the magnetostrictive constants of all the crystalline iron-based alloy thin strips were in the range of 0～+5×10 ^-6 . Therefore, it is presumed that each sample after heat treatment (ie, the crystalline iron-based alloy powder) also has the same magnetostriction constant.

<Production of Magnetic Core> To 100 parts by mass (25.00 g) of sample No. 21 (crystalline iron-based alloy powder with alloy composition E) in Table 2, powdered polysiloxane resin was added as a binder 5 parts by mass (1.25 g) and mixed. The obtained mixed powder was filled in a molding die, and a kneaded product was formed by applying a pressure of 400 MPa with a hydraulic press molding machine. The obtained molded body was heat-treated at 200°C for 1 hour. Through the above process, an annular magnetic core having an outer diameter of 13.5 mm, an inner diameter of 7.7 mm and a height of 2.0 mm can be obtained.

-Core Loss- The core of the above-mentioned annular body was used as the object to be measured, and 18 turns each of the primary winding and the secondary winding were wound around the object to be measured. In this state, the core loss (kW/m ³ ) of the magnetic core of the annular body was measured at room temperature using a BH analyzer SY-8218 manufactured by Iwatsu Instrument Co., Ltd. under the conditions of a maximum magnetic flux density of 30 mT and a frequency of 2 MHz at room temperature. . As a result, the core loss (kW/m ³ ) was 2400 kW/m ³ .

- Occupancy ratio (phase bulk density; %) - Core density A calculated from the weight and volume of the annular magnetic core, crystalline iron-based alloy powder and polysiloxane obtained by the gas replacement method The density B of the mixed powder, the density C of the crystalline iron-based alloy powder, the density of the polysiloxane D, the weight E of the crystalline iron-based alloy powder in the mixed powder, and the polysiloxane in the mixed powder The weight F of , and the occupancy rate P is calculated according to the following formula. P=A/B×V×100(%) A: Core density (×10 ³ kg/m ³ ) B: Density of mixed powder (×10 ³ kg/m ³ ) C: Crystalline iron-based alloy powder Density (×10 ³ kg/m ³ ) D: Density of polysiloxane resin (×10 ³ kg/m ³ ) E: Weight of crystalline iron-based alloy powder in mixed powder (kg) F: Mixed powder The weight of the polysiloxane in the middle (kg) V: the volume ratio of the crystalline iron-based alloy powder to the whole mixed powder, V=(E/C)/[(E/C)+(F/D) ] As a result, the occupancy rate (phase density; %) in the above-mentioned annular magnetic core was 68%.

The disclosure of Japanese Patent Application No. 2017-152561 filed on August 7, 2017 and the disclosure of Japanese Patent Application No. 2017-168311 filed on September 1, 2017 are incorporated herein by reference. All documents, patent applications, and technical specifications described in this specification are incorporated herein by reference to the same extent as when each document, patent application, and technical specification are cited for reference and are specifically and individually marked.

Fig. 1 is a graph showing the relationship between d50 and coercive force for each alloy composition (A to G) in crystalline iron-based alloy powder.

Claims (7)

An iron-based alloy, which is used in the manufacture of crystalline iron-based alloy powders with a coercive force of 190A/m or less when a magnetic field of 40kA/m is applied, and has an alloy composition represented by the following composition formula (1); Fe _{100- abcde} Cu _a Si _b B _c (Mo _1-α Nb _α ) _{d Cre} 1.5, 13.0≦b≦15.0, 8.0<c<12.0, 0.5≦d<4.0, 0.5<e≦2.0, 10.0<c+d<13.5, 0.2≦α≦0.6, and 71.0≦100-abcde≦74.0. According to the iron-based alloy of claim 1, in the composition formula (1), d satisfies 0.5≦d≦3.5. According to the iron-based alloy of claim 1 or 2, in the composition formula (1), c satisfies 10.0≦c<12.0. A crystalline iron-based alloy powder with a coercive force of 190A/m or less when a magnetic field of 40kA/m is applied; having an alloy composition represented by the following composition formula (1), and having nanocrystalline grains with an average particle size of 40nm or less The alloy structure; Fe _100-abcde Cu _a Si _b B _c (Mo _1-α Nb _α ) _d Cr _e ... composition formula (1) In composition formula (1), a, b, c, d, e, and α satisfy 0.1≦a≦1.5, 13.0≦b≦15.0, 8.0<c<12.0, 0.5≦d<4.0, 0.5<e≦2.0, 10.0<c+d<13.5, 0.2≦α≦0.6, and 71.0≦ 100-abcde≦74.0. The crystalline iron-based alloy powder according to claim 4, wherein, in the composition formula (1), d satisfies 0.5≦d≦3.5. According to the crystalline iron-based alloy powder according to claim 4 or 5, in the composition formula (1), c satisfies 10.0≦c<12.0. A magnetic core, comprising: the powdered crystalline iron-based alloy powder according to any one of items 4 to 6 of the scope of the patent application, and a binder for adhering the powdered crystalline iron-based alloy powder; the binder is selected from free-ring In the group consisting of oxygen resin, unsaturated polyester resin, phenolic resin, xylene resin, diallyl phthalate resin, polysiloxane resin, polyimide imide, polyimide, and water glass at least one of them.

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