Patent Application
20180096765
The present invention relates to a soft magnetic alloy.
Low power consumption and high efficiency have been demanded in electronic, information, communication equipment, and the like. Moreover, the above demands are becoming stronger for a low carbon society. Thus, reduction in energy loss and improvement in power supply efficiency are also required for power supply circuits of electronic, information, communication equipment, and the like. Then, improvement in permeability and reduction in core loss (magnetic core loss) are required for the magnetic core of the ceramic element used in the power supply circuit. If the core loss is reduced, the loss of power energy is reduced, and high efficiency and energy saving are achieved.
Patent Document 1 discloses that a soft magnetic alloy powder having a large permeability and a small core loss and suitable for magnetic cores is obtained by changing the particle shape of the powder. However, magnetic cores having a larger permeability and a smaller core loss are required now.
Patent Document 1: JP 2000-30924 A
As a method of reducing the core loss of the magnetic core, it is conceivable to reduce coercivity of a magnetic material constituting the magnetic core.
It is an object of the invention to provide a soft magnetic alloy having a low coercivity and a high permeability.
To achieve the above object, the soft magnetic alloy according to the present invention is a soft magnetic alloy comprising a main component of Fe, wherein
the soft magnetic alloy comprises a Fe composition network phase where regions whose Fe content is larger than an average composition of the soft magnetic alloy are linked;
the Fe composition network phase contains Fe content maximum points that are locally higher than their surroundings in 400,000/μm3 or more; and
a ratio of Fe content maximum points whose coordination number is 1 or more and 5 or less is 80% or more and 100% or less with respect to all of the Fe content maximum points.
The soft magnetic alloy according to the present invention comprises the Fe composition network phase, and thus has a low coercivity and a high permeability.
In the soft magnetic alloy according to the present invention, a ratio of Fe content maximum points whose coordination number is 2 or more and 4 or less is preferably 70% or more and 90% or less with respect to all of the Fe content maximum points.
In the soft magnetic alloy according to the present invention, a volume ratio of the Fe composition network phase is preferably 25 vol % or more and 50 vol % or less with respect to the entire soft magnetic alloy.
In the soft magnetic alloy according to the present invention, a volume ratio of the Fe composition network phase is preferably 30 vol % or more and 40 vol % or less with respect to the entire soft magnetic alloy.
Hereinafter, an embodiment of the present invention will be described.
A soft magnetic alloy according to the present embodiment is a soft magnetic alloy whose main component is Fe. Specifically, “main component is Fe” means a soft magnetic alloy whose Fe content is 65 atom % or more with respect to the entire soft magnetic alloy.
Except that main component is Fe, the soft magnetic alloy according to the present embodiment has any composition. The soft magnetic alloy according to the present embodiment may be a Fe—Si-M-B—Cu—C based soft magnetic alloy, a Fe-M′-B—C based soft magnetic alloy, or another soft magnetic alloy.
In the following description, the entire soft magnetic alloy is considered to be 100 atom % if there is no description of parameter with respect to content ratio of each element of the soft magnetic alloy.
When a Fe—Si-M-B—Cu—C based soft magnetic alloy is used, the following formulae are preferably satisfied if the Fe—Si-M-B—Cu—C based soft magnetic alloy has a composition expressed by FeaCubMcSidBeCf. When the following formulae are satisfied, the number of Fe content maximum points mentioned below tends to be large, a favorable Fe composition network phase tends to be obtained easily, and a soft magnetic alloy having a low coercivity and a high permeability tends to be obtained easily. Incidentally, a soft magnetic alloy composed of the following compositions is made of comparatively inexpensive raw materials. The Fe—Si-M-B—Cu—C based soft magnetic alloy of the present application also includes a soft magnetic alloy with f=0, that is, failing to contain C.
a+b+c+d+e+f=100
0.1≦b≦3.0
1.0≦c≦10.0
11.5≦d≦17.5
7.0≦e≦13.0
0.0≦f≦4.0
A Cu content (b) is preferably 0.1 to 3.0 atom %, more preferably 0.5 to 1.5 atom %. The smaller a Cu content is, the more easily a ribbon composed of the soft magnetic alloy tends to be prepared by a single roll method mentioned below.
M is a transition metal element other than Cu. M is preferably one or more selected from a group of Nb, Ti, Zr, Hf, V, Ta, and Mo. Preferably, M contains Nb.
A M content (c) is preferably 1.0 to 10.0 atom %, more preferably 3.0 to 5.0 atom %.
A Si content (d) is preferably 11.5 to 17.5 atom %, more preferably 13.5 to 15.5 atom %.
AB content (e) is preferably 7.0 to 13.0 atom %, more preferably 9.0 to 11.0 atom %.
A C content (f) is preferably 0.0 to 4.0 atom %. Amorphousness is improved by addition of C.
Incidentally, Fe is, so to speak, a remaining part of the Fe—Si-M-B—Cu—C based soft magnetic alloy according to the present embodiment.
When the Fe-M′-B—C based soft magnetic alloy is used, the following formulae are preferably satisfied if the Fe-M′-B—C based soft magnetic alloy has a composition expressed by FeαM′βBγCΩ. When the following formulae are satisfied, the number of Fe content maximum points mentioned below tends to be large, a favorable Fe composition network phase tends to be obtained easily, and a soft magnetic alloy having a low coercivity and a high permeability tends to be obtained easily. Incidentally, a soft magnetic alloy composed of the following compositions is made of comparatively inexpensive raw materials. The Fe-M′-B—C based soft magnetic alloy of the present application also includes a soft magnetic alloy with Ω=0, that is, failing to contain C.
α+β+γ+Ω=100
1.0≦β≦14.1
2.0≦γ≦20.0
0.0≦Ω≦4.0
M′ is a transition metal element. M′ is preferably one or more element selected from a group of Nb, Cu, Cr, Zr, and Hf. M′ is more preferably one or more element selected from a group of Nb, Cu, Zr, and Hf. M′ most preferably contains one or more element selected from a group of Nb, Zr, and Hf.
A M′ content (β) is preferably 1.0 to 14.1 atom %, more preferably 7.0 to 10.1 atom %.
A Cu content in M′ is preferably 0.0 to 2.0 atom %, more preferably 0.1 to 1.0 atom %, provided that an entire soft magnetic alloy is 100 atom %. When a M′ content is less than 7.0 atom %, however, failing to contain Cu may be preferable.
A B content (γ) is preferably 2.0 to 20.0 atom %. When M′ contains Nb, a B content (γ) is preferably 4.5 to 18.0 atom %. When M′ contains Zr and/or Hf, a B content (γ) is preferably 2.0 to 8.0 atom %. The smaller a B content is, the further amorphousness tends to deteriorate. The larger a B content is, the further the number of maximum points mentioned below tends to decrease.
A C content (Ω) is preferably 0.0 to 4.0 atom %, more preferably 0.1 to 3.0 atom %. Amorphousness is improved by addition of C. The larger a C content is, the further the number of maximum points mentioned below tends to decrease.
Another soft magnetic alloy may be a Fe-M″-B—P—C based soft magnetic alloy, a Fe—Si—P—B—Cu—C based soft magnetic alloy, or the like.
When a Fe-M″-B—P—C based soft magnetic alloy is used, the following formulae are preferably satisfied if the Fe-M″-B—P—C based soft magnetic alloy has a composition expressed by FevM″wBxPyCz. When the following formulae are satisfied, the number of maximum points mentioned below tends to increase, a favorable Fe composition network phase tends to be obtained easily, and a soft magnetic alloy having a low coercivity and a high permeability tends to be obtained easily. Incidentally, a soft magnetic alloy composed of the following compositions is made of comparatively inexpensive raw materials. The Fe-M″-B—P—C based soft magnetic alloy of the present application also includes a soft magnetic alloy with z=0, that is, failing to contain C.
v+w+x+y+z=100
3.2≦w≦15.5
2.8≦x≦13.0
0.1≦y≦3.0
0.0≦z≦2.0
M″ is a transition metal element. M″ is preferably one or more elements selected from a group of Nb, Cu, Cr, Zr, and Hf M″ preferably contains Nb.
When a Fe—Si—P—B—Cu—C based soft magnetic alloy is used, the following formulae are preferably satisfied if the Fe—Si—P—B—Cu—C based soft magnetic alloy has a composition expressed by FevSiw1Pw2BxCuyCz. When the following formulae are satisfied, the number of maximum points mentioned below tends to increase, a favorable Fe composition network phase tends to be obtained easily, and a soft magnetic alloy having a low coercivity and a high permeability tends to be obtained easily. Incidentally, a soft magnetic alloy composed of the following compositions is made of comparatively inexpensive raw materials. The Fe—Si—P—B—Cu—C based soft magnetic alloy of the present application also includes a soft magnetic alloy with w1=0 or w2=0 (i.e., Si or P is not contained). The Fe—Si—P—B—Cu—C based soft magnetic alloy of the present application also includes a soft magnetic alloy with z=0 (i.e., C is not contained).
v+w1+w2+x+y+z=100
0.0≦w1≦8.0
0.0≦w2≦8.0
3.0≦w1+w2≦11.0
5.0≦x≦13.0
0.1≦y≦0.7
0.0≦z≦4.0
Here, the Fe composition network phase owned by the soft magnetic alloy according to the present embodiment will be described.
The Fe composition network phase is a phase whose Fe content is higher than an average composition of the soft magnetic alloy. When observing a Fe concentration distribution of the soft magnetic alloy according to the present embodiment using a three-dimensional atom probe (hereinafter also referred to as a 3DAP) with a thickness of 5 nm, it can be observed that portions having a high Fe content are distributed in network as shown in
In conventional soft magnetic alloys containing Fe, a plurality of portions having a high Fe content respectively has a spherical shape or an approximately spherical shape and exists at random via portions having a low Fe content. The soft magnetic alloy according to the present embodiment is characterized in that portions having a high Fe content are linked in network and distributed as shown in
An aspect of the Fe composition network phase can be quantified by measuring the number of maximum points and coordination number of the maximum points of the Fe composition network phase.
The maximum point of the Fe composition network phase is a Fe content point that is locally higher than its surroundings. The coordination number of the maximum point is the number of the other maximum points linking to a maximum point via the Fe composition network phase.
Hereinafter, an analysis procedure of the Fe composition network phase according to the present embodiment will be described using the figures, and a maximum point, a coordination number of the maximum point, and a calculation method thereof will be thereby described.
First, a cube whose length of one side is 40 nm is determined as a measurement range, and this cube is divided into cubic grids whose length of one side is 1 nm. That is, 64,000 grids (40×40×40=64000) exist in one measurement range.
Next, a Fe content in each grid is evaluated. Then, a Fe content average value (hereinafter also referred to as a threshold value) in all of the grids is calculated. The Fe content average value is a value substantially equivalent to a value calculated from an average composition of each soft magnetic alloy.
Next, a grid whose Fe content exceeds the threshold value and is higher than that of all adjacent unit grids is determined as a maximum point.
With respect to grids 10 located at the end of the measurement range, grids whose Fe content is zero are considered to exist outside the measurement range.
Next, as shown in
Next, as shown in
Next, as shown in
Then, the number of line segments extending from each maximum point 10a is determined as a coordination number of each maximum point 10a. In
When a grid existing on an outermost surface within a measurement range of 40 nm×40 nm×40 nm shows a maximum point, this maximum point is excluded from calculation of a ratio of maximum points whose coordination number is within a predetermined range mentioned below.
Incidentally, the Fe composition network phase also includes a maximum point whose coordination number is zero and a region whose Fe content is higher than a threshold value existing in the surroundings of a maximum point whose coordination number is zero.
The accuracy of calculation results can be sufficiently highly improved by conducting the above-mentioned measurement several times in respectively different measurement ranges. The above-mentioned measurement is preferably conducted three times or more in respectively different measurement ranges.
The Fe composition network phase owned by the soft magnetic alloy according to the present embodiment contains Fe content maximum points that are locally higher than their surroundings in 400,000/μm3 or more, and a ratio of Fe content maximum points whose coordination number is 1 or more and 5 or less is 80% or more and 100% or less with respect to all of the Fe content maximum points. Incidentally, a denominator of the number of the maximum points is a volume of an entire measurement range, and is a total volume of the region 20a whose Fe content is higher than a threshold value and the region 20b whose Fe content is a threshold value or less.
The soft magnetic alloy according to the present embodiment comprises a Fe composition network phase where the number of maximum points and a ratio of maximum points whose coordination number is 1 or more and 5 or less are within the above ranges. It is thus possible to obtain a soft magnetic alloy having a low coercivity and a high permeability and excelling in soft magnetic properties particularly in high frequencies.
Preferably, a ratio of Fe content maximum points whose coordination number is 2 or more and 4 or less is 70% or more and 90% or less with respect to all of the Fe content maximum points.
Moreover, a volume ratio of the Fe composition network phase (a volume ratio of the region 20a whose Fe content is higher than a threshold value to a total of the region 20a whose Fe content is higher than a threshold value and the region 20b whose Fe content is a threshold value or less) is preferably 25 vol % or more and 50 vol % or less, more preferably 30 vol % or more and 40 vol % or less, with respect to the entire soft magnetic alloy.
When comparing a Fe—Si-M-B—Cu—C based soft magnetic alloy with a Fe-M′-B—C based soft magnetic alloy, the Fe-M′-B—C based soft magnetic alloy tends to have a higher number of maximum points and also have a larger coordination number.
When comparing a Fe—Si-M-B—Cu—C based soft magnetic alloy with a Fe-M′-B—C based soft magnetic alloy, the Fe—Si-M-B—Cu—C based soft magnetic alloy tends to have a lower coercivity and a higher permeability than those of the Fe-M′-B—C based soft magnetic alloy.
Hereinafter, a manufacturing method of the soft magnetic alloy according to the present embodiment will be described.
The soft magnetic alloy according to the present embodiment is manufactured by any method. For example, a ribbon of the soft magnetic alloy according to the present embodiment is manufactured by a single roll method.
In the single roll method, first, pure metals of metal elements contained in a soft magnetic alloy finally obtained are prepared and weighed so that a composition identical to that of the soft magnetic alloy finally obtained is obtained. Then, the pure metals of each metal element are molten and mixed, and a base alloy is prepared. Incidentally, the pure metals are molten by any method. For example, the pure metals are molten by high-frequency heating after a chamber is evacuated. Incidentally, the base alloy and the soft magnetic alloy finally obtained normally have the same composition.
Next, the prepared base alloy is heated and molten, and a molten metal is obtained. The molten metal has any temperature, and may have a temperature of 1200 to 1500° C., for example.
In the single roll method, the thickness of the ribbon to be obtained can be mainly controlled by controlling a rotating speed of the roll 33, but can be also controlled by controlling a distance between the nozzle 31 and the roll 33, a temperature of the molten metal, or the like. The ribbon has any thickness, and may have a thickness of 15 to 30 μm, for example.
The ribbon is preferably amorphous before a heat treatment mentioned below. The amorphous ribbon undergoes a heat treatment mentioned below, and the above-mentioned favorable Fe composition network phase can be thereby obtained.
Incidentally, whether the ribbon of the soft magnetic alloy before a heat treatment is amorphous or not is confirmed by any method. Here, the fact that the ribbon is amorphous means that the ribbon contains no crystals. For example, the existence of crystals whose particle size is about 0.01 to 10 μm can be confirmed by a normal X-ray diffraction measurement. When crystals exist in the above amorphous phase but their volume ratio is small, a normal X-ray diffraction measurement can determine that no crystals exist. In this case, for example, the existence of crystals can be confirmed by obtaining a restricted visual field diffraction image, a nano beam diffraction image, a bright field image, or a high resolution image of a sample thinned by ion milling using a transmission electron microscope. When using a restricted visual field diffraction image or a nano beam diffraction image, with respect to diffraction pattern, a ring-shaped diffraction is formed in case of being amorphous, and diffraction spots due to crystal structure are formed in case of being non-amorphous. When using a bright field image or a high resolution image, whether the existence of crystals can be confirmed by visually observing the image with a magnification of 1.00×105 to 3.00×105. In the present specification, it is considered that “crystals exist” if crystals can be confirmed to exist by a normal X-ray diffraction measurement, and it is considered that “microcrystals exist” if crystals cannot be confirmed to exist by a normal X-ray diffraction measurement but can be confirmed to exist by obtaining a restricted visual field diffraction image, a nano beam diffraction image, a bright field image, or a high resolution image of a sample thinned by ion milling using a transmission electron microscope.
Here, the present inventors have found that when a temperature of the roll 33 and a vapor pressure in the chamber 35 are controlled appropriately, a ribbon of a soft magnetic alloy before a heat treatment becomes amorphous easily, and a favorable Fe composition network phase is easily obtained after the heat treatment. Specifically, the present inventors have found that a ribbon of a soft magnetic alloy becomes amorphous easily by setting a temperature of the roll 33 to 50 to 70° C., preferably 70° C., and setting a vapor pressure in the chamber 35 to 11 hPa or less, preferably 4 hPa or less, using an Ar gas whose dew point is adjusted.
In a single roll method, it is conventionally considered that increasing a cooling rate and rapidly cooling the molten metal 32 are preferable, and that the cooling rate is preferably increased by widening a temperature difference between the molten metal 32 and the roll 33. It is thus considered that the roll 33 preferably normally has a temperature of about 5 to 30° C. The present inventors, however, have found that when the roll 33 has a temperature of 50 to 70° C., which is higher than that of a conventional roll method, and a vapor pressure in the chamber 35 is 11 hPa or less, the molten metal 32 is cooled uniformly, and a ribbon of a soft magnetic alloy to be obtained before a heat treatment easily becomes uniformly amorphous. Incidentally, a vapor pressure in the chamber has no lower limit. The vapor pressure may be adjusted to 1 hPa or less by filling the chamber with an Ar gas whose dew point is adjusted or by controlling the chamber to a state close to vacuum. When the vapor pressure is high, an amorphous ribbon before a heat treatment is hard to be obtained, and the above-mentioned favorable Fe composition network phase is hard to be obtained after a heat treatment mentioned below even if an amorphous ribbon before a heat treatment is obtained.
The obtained ribbon 34 undergoes a heat treatment, and the above-mentioned favorable Fe composition network phase can be thereby obtained. In this case, the above-mentioned favorable Fe composition network phase is easily obtained if the ribbon 34 is completely amorphous.
There is no limit to conditions of the heat treatment. Favorable conditions of the heat treatment differ depending on composition of a soft magnetic alloy. Normally, a heat treatment temperature is preferably about 500 to 600° C., and a heat treatment time is preferably about 0.5 to 10 hours, but favorable heat treatment temperature and heat treatment time may be in a range deviated from the above ranges depending on the composition.
In addition to the above-mentioned single roll method, a powder of the soft magnetic alloy according to the present embodiment is obtained by a water atomizing method or a gas atomizing method, for example. Hereinafter, a gas atomizing method will be described.
In a gas atomizing method, a molten alloy of 1200 to 1500° C. is obtained similarly to the above-mentioned single roll method. Thereafter, the molten alloy is sprayed in a chamber, and a powder is prepared.
At this time, the above-mentioned favorable Fe composition network phase is finally easily obtained with a gas spray temperature of 50 to 100° C. and a vapor pressure of 4 hPa or less in the chamber.
After the powder is prepared by the gas atomizing method, a heat treatment is conducted at 500 to 650° C. for 0.5 to 10 minutes. This makes it possible to promote diffusion of elements while the powder is prevented from being coarse due to sintering of each particle, reach a thermodynamic equilibrium state for a short time, remove distortion and stress, and easily obtain a Fe composition network phase. It is then possible to obtain a soft magnetic alloy powder having soft magnetic properties that are favorable particularly in high-frequency regions.
An embodiment of the present invention has been accordingly described, but the present invention is not limited to the above-mentioned embodiment.
The soft magnetic alloy according to the present embodiment has any shape, such as a ribbon shape and a powder shape as described above. The soft magnetic alloy according to the present embodiment may also have a block shape.
The soft magnetic alloy according to the present embodiment is used for any purpose, such as for magnetic cores, and can be favorably used for magnetic cores for inductors, particularly for power inductors. In addition to magnetic cores, the soft magnetic alloy according to the present embodiment can be also favorably used for thin film inductors, magnetic heads, transformers, and the like.
Hereinafter, a method for obtaining a magnetic core and an inductor from the soft magnetic alloy according to the preset embodiment will be described, but is not limited to the following method.
For example, a magnetic core from a ribbon-shaped soft magnetic alloy is obtained by winding or laminating the ribbon-shaped soft magnetic alloy. When a ribbon-shaped soft magnetic alloy is laminated via an insulator, a magnetic core having further improved properties can be obtained.
For example, a magnetic core from a powder-shaped soft magnetic alloy is obtained by appropriately mixing the powder-shaped soft magnetic alloy with a binder and pressing this using a die. When an oxidation treatment, an insulation coating, or the like is carried out against the surface of the powder before the mixture with the binder, resistivity is improved, and a magnetic core further suitable for high-frequency regions is obtained.
The pressing method is not limited. Examples of the pressing method include a pressing using a die and a mold pressing. There is no limit to the kind of the binder. Examples of the binder include a silicone resin. There is no limit to a mixture ratio between the soft magnetic alloy powder and the binder either. For example, 1 to 10 mass % of the binder is mixed with 100 mass % of the soft magnetic alloy powder.
For example, 100 mass % of the soft magnetic alloy powder is mixed with 1 to 5 mass % of a binder and compressively pressed using a die, and it is thereby possible to obtain a magnetic core having a space factor (powder filling rate) of 70% or more, a magnetic flux density of 0.4 T or more at the time of applying a magnetic field of 1.6×104 A/m, and a resistivity of 1 Ω·cm or more. These properties are more excellent than those of normal ferrite magnetic cores.
For example, 100 mass % of the soft magnetic alloy powder is mixed with 1 to 3 mass % of a binder and compressively pressed using a die under a temperature condition that is equal to or higher than a softening point of the binder, and it is thereby possible to obtain a dust core having a space factor of 80% or more, a magnetic flux density of 0.9 T or more at the time of applying a magnetic field of 1.6×104 A/m, and a resistivity of 0.1 Ω·cm or more. These properties are more excellent than those of normal dust cores.
Moreover, a green compact constituting the above-mentioned magnetic core undergoes a heat treatment after pressing as a heat treatment for distortion removal. This further decreases core loss and improves usability.
An inductance product is obtained by winding a wire around the above-mentioned magnetic core. The wire is wound by any method, and the inductance product is manufactured by any method. For example, a wire is wound around a magnetic core manufactured by the above-mentioned method at least in one or more turns.
Moreover, when soft magnetic alloy particles are used, there is a method of manufacturing an inductance product by pressing and integrating a magnetic body incorporating a wire coil. In this case, an inductance product corresponding to high frequencies and large current is obtained easily.
Moreover, when soft magnetic alloy particles are used, an inductance product can be obtained by carrying out heating and firing after alternately printing and laminating a soft magnetic alloy paste obtained by pasting the soft magnetic alloy particles added with a binder and a solvent and a conductor paste obtained by pasting a conductor metal for coils added with a binder and a solvent. Instead, an inductance product where a coil is incorporated in a magnetic body can be obtained by preparing a soft magnetic alloy sheet using a soft magnetic alloy paste, printing a conductor paste on the surface of the soft magnetic alloy sheet, and laminating and firing them.
Here, when an inductance product is manufactured using soft magnetic alloy particles, in view of obtaining excellent Q properties, it is preferred to use a soft magnetic alloy powder whose maximum particle size is 45 μm or less by sieve diameter and center particle size (D50) is 30 μm or less. In order to have a maximum particle size of 45 μm or less by sieve diameter, only a soft magnetic alloy powder that passes through a sieve whose mesh size is 45 μm may be used.
The larger a maximum particle size of a soft magnetic alloy powder is, the further Q values in high-frequency regions tend to decrease. In particular, when using a soft magnetic alloy powder whose maximum particle diameter is more than 45 μm by sieve diameter, Q values in high-frequency regions may decrease greatly. When emphasis is not placed on Q values in high-frequency regions, however, a soft magnetic alloy powder having a large variation can be used. When a soft magnetic alloy powder having a large variation is used, cost can be reduced due to comparatively inexpensive manufacture thereof.
Hereinafter, the present invention will be described based on Examples.
Pure metal materials were respectively weighed so that a base alloy having a composition of Fe: 73.5 atom %, Si: 13.5 atom %, B: 9.0 atom %, Nb: 3.0 atom %, and Cu: 1.0 atom % was obtained. Then, the base alloy was manufactured by evacuating a chamber and thereafter melting the pure metal materials by high-frequency heating.
Then, the prepared base alloy was heated and molten to be turned into a metal in a molten state at 1300° C. This metal was thereafter sprayed against a roll by a single roll method at a predetermined temperature and a predetermined vapor pressure, and ribbons were prepared. These ribbons were configured to have a thickness of 20 μm by appropriately adjusting a rotation speed of the roll. Next, each of the prepared ribbons underwent a heat treatment, and single-plate samples were obtained.
In Experiment 1, each sample shown in Table 1 was manufactured by changing roll temperature, vapor pressure, and heat treatment conditions. The vapor pressure was adjusted using an Ar gas whose dew point had been adjusted.
Each of the ribbons before the heat treatment underwent an X-ray diffraction measurement for confirmation of existence of crystals. In addition, existence of microcrystals was confirmed by observing a restricted visual field diffraction image and a bright field image at 300,000 magnifications using a transmission electron microscope. As a result, it was confirmed that the ribbons of each example had no crystals or microcrystals and were amorphous.
Then, each sample after each ribbon underwent the heat treatment was measured with respect to coercivity, permeability at 1 kHz frequency, and permeability at 1 MHz frequency. Table 1 shows the results. A permeability of 9.0×104 or more at 1 kHz frequency was considered to be favorable. A permeability of 2.3×103 or more at 1 MHz frequency was considered to be favorable.
Moreover, each sample was measured using a three-dimensional atom probe (3DAP) with respect to the number of Fe content maximum points, a ratio of Fe content maximum points whose coordination number was 1 or more and 5 or less, a ratio of Fe content maximum points whose coordination number was 2 or more and 4 or less, and a content ratio of the Fe network phase to the entire sample. Table 1 shows the results.
Table 1 shows that amorphous ribbons are obtained in Examples where roll temperature was 50 to 70° C., vapor pressure was controlled to 11 hPa or less in a chamber of 30° C., and heat conditions were 500 to 600° C. and 0.5 to 10 hours. Then, it was confirmed that a favorable Fe network can be formed by carrying out a heat treatment against the ribbons. It was also confirmed that coercivity decreased and permeability improved.
On the other hand, the number of maximum points to be a condition of a favorable Fe network phase after a heat treatment tended to be small in comparative examples whose roll temperature is 30° C. (Sample No. 22 to Sample No. 26) or comparative examples whose roll temperature is 50° C. or 70° C. and vapor pressure is higher than 11 hPa (Sample No. 1, Sample No. 2, Sample No. 16, and Sample No. 17). That is, when the roll temperature was too low and the vapor pressure was too high at the time of manufacture of the ribbons, the number of maximum points after a heat treatment was small after the ribbons underwent a heat treatment, and a favorable Fe network could not be formed.
When the heat treatment temperature was too low (Sample No. 11) and the heat treatment time was too short (Sample No. 7), a favorable Fe network was not formed, and coercivity was higher and permeability was lower than those of Examples. When the heat treatment temperature was high (Sample No. 15) and the heat treatment time was too long (Sample No. 10), the number of maximum points of Fe tended to decrease. Sample No. 15 had a tendency that when the heat treatment temperature was high, coercivity deteriorated rapidly, and permeability decreased rapidly. It is conceived that this is because a part of the soft magnetic alloy forms boride (Fe2B). The formation of boride in Sample No. 15 was confirmed using an X-ray diffraction measurement.
An experiment was carried out in the same manner as Experiment 1 by changing a composition of a base alloy at a roll temperature of 70° C. and a vapor pressure of 4 hPa in a chamber. Each sample underwent a heat treatment at 450° C., 500° C., 550° C., 600° C., and 650° C., and a temperature when coercivity was lowest was determined as a heat treatment temperature. Table 2 and Table 3 show characteristics at the temperature when coercivity was lowest. That is, the samples had different heat treatment temperatures. Table 2 shows the results of experiments carried out with Fe—Si-M-B—Cu—C based compositions. Table 3 and Table 4 show the results of experiments carried out with Fe-M′-B—C based compositions. Table 5 and Table 6 show the results of experiments carried out with Fe-M″-B—P—C based compositions. Table 7 shows the results of experiments carried out with Fe—Si—P—B—Cu—C based compositions.
In the Fe—Si-M-B—Cu—C based compositions, the above-mentioned favorable Fe network was formed, a coercivity of 2.0 A/m or less was considered to be favorable, a permeability of 5.0×104 or more at 1 kHz frequency was considered to be favorable, and a permeability of 2.0×103 or more at 1 MHz frequency was considered to be favorable. In the Fe-M′-B—C based compositions, a coercivity of 20 A/m or less was considered to be favorable, a permeability of 2.0×104 or more at 1 kHz frequency was considered to be favorable, and a permeability of 1.3×103 or more at 1 MHz frequency was considered to be favorable. In the Fe-M″-B—P—C based compositions, a coercivity of 4.0 A/m or less was considered to be favorable, a permeability of 5.0×104 or more at 1 kHz frequency was considered to be favorable, and a permeability of 2.0×103 or more at 1 MHz frequency was considered to be favorable. In the Fe—Si—P—B—Cu—C based compositions, a coercivity of 7.0 A/m or less was considered to be favorable, a permeability of 3.0×104 or more at 1 kHz frequency was considered to be favorable, and a permeability of 2.0×103 or more at 1 MHz frequency was considered to be favorable.
Sample No. 39 was observed using a 3DAP with 5 nm thickness.
As shown in Table 2 to Table 7, a ribbon obtained by a single roll method at a roll temperature of 70° C. and a vapor pressure of 4 hPa can form an amorphous phase even if a base alloy has different compositions, and a heat treatment at an appropriate temperature forms a favorable Fe composition network phase, decreases coercivity, and improves permeability.
Examples having a Fe—Si-M-B—Cu—C based composition shown in Table 2 tended to have a comparatively small number of maximum points, and examples having a Fe-M′-B—C based composition shown in Table 3 and Table 4 tended to have a comparatively large number of maximum points.
In samples having a Fe—Si-M-B—Cu—C based composition shown in Table 2, particularly Sample No. 32 to Sample No. 36, the number of maximum points of Fe tended to increase by a small amount of addition of Cu. When a Cu content is too large, there is a tendency that a ribbon before a heat treatment obtained by a single roll method contains crystals, and a favorable Fe network is not formed.
In samples having a Fe—Si-M-B—Cu—C based composition shown in Table 2, particularly Sample No. 43 to Sample No. 47, a sample having a smaller Nb content shows that a ribbon obtained by a single roll method tended to easily contain crystals. A sample having a larger Nb content tended to easily have a decreased number of maximum points of Fe and a decreased permeability.
In samples having a Fe—Si-M-B—Cu—C based composition shown in Table 2, particularly Sample No. 27 to Sample No. 31, a sample having a smaller B content shows that a ribbon before a heat treatment obtained by a single roll method tended to easily contain microcrystals. A sample having a larger B content tended to easily have a decreased number of maximum points of Fe and a decreased permeability.
In samples having a Fe—Si-M-B—Cu—C based composition shown in Table 2, particularly Sample No. 37 to Sample No. 42, a sample having a smaller Si content tended to have a decreased permeability.
In samples having a Fe—Si-M-B—Cu—C based composition shown in Table 2, particularly Sample No. 55 and Sample No. 56, amorphousness tended to be maintained by containing C even in a range where a Fe content is increased, and a favorable Fe network tended to be formed.
In samples having a Fe-M′-B—C based composition shown in Table 3, particularly Sample No. 61 to Sample No. 65, a sample having a smaller M content shows that a ribbon before a heat treatment obtained by a single roll method tended to contain crystals.
In samples having a Fe-M′-B—C based composition shown in Table 3, particularly Sample No. 66 to Sample No. 70, a sample having a smaller B content shows that a ribbon before a heat treatment obtained by a single roll method tended to contain crystals, and a sample having a larger B content shows that the number of maximum points of Fe tended to decrease.
As a result of similar examination with respect to Sample No. 71 to Sample No. 103 in Table 3 and Sample No. 104 to Sample No. 118 and Sample No. 160 to Sample No. 179 in Table 4, it was confirmed that an amorphous phase was formed in a soft magnetic alloy ribbon having an appropriate composition and manufactured at a roll temperature of 70° C. and a vapor pressure of 4 hPa in a chamber. Then, the samples tended to have a network structure of Fe, a low coercivity, and a high permeability by carrying out an appropriate heat treatment. Sample No. 104 to Sample No. 118, which contained 0.1 to 3.0 atom % of Cu and 0.1 to 3.0 atom % of C, tended to have a lower coercivity and a higher permeability, compared to the other samples.
A coordination number distribution of all maximum points was graphed with respect to Sample No. 39 of Table 2 and Sample No. 63 of Table 3.
As a result of similar examination with respect to Sample No. 120 to Sample No. 159 in Table 5 and Sample No. 194 to Sample No. 213 in Table 6, which had a Fe-M″-B—P—C based composition, it was confirmed that an amorphous phase was formed in a soft magnetic alloy ribbon having an appropriate composition and manufactured at a roll temperature of 70° C. and a vapor pressure of 4 hPa in a chamber. Then, the samples tended to have a network structure of Fe, a low coercivity, and a high permeability by carrying out an appropriate heat treatment. In a sample having less B, P and/or C content, the number of maximum points and a ratio of maximum points whose coordination number was 1 or more and 5 or less were larger easily, and favorable characteristics were obtained easily.
As a result of similar examination with respect to Sample No. 214 to Sample No. 223 in Table 7, which had a Fe—Si—P—B—Cu—C based composition, it was confirmed that an amorphous phase was formed in a soft magnetic alloy ribbon having an appropriate composition and manufactured at a roll temperature of 70° C. and a vapor pressure of 4 hPa in a chamber. Then, the samples tended to have a network structure of Fe, a low coercivity, and a high permeability by carrying out an appropriate heat treatment. In a sample having more Si content, the number of maximum points and a ratio of maximum points whose coordination number was 1 or more and 5 or less were larger easily, and favorable characteristics were obtained easily. According to Sample No. 214 to Sample No. 217, it was found that favorable characteristics were obtained easily in a sample having a larger Si content and a smaller Fe content. According to Sample No. 218 to Sample No. 221, it was found that when a total of a Si content and a P content was constant, favorable characteristics were obtained easily in a sample having a larger P content.
Pure metal materials were respectively weighed so that a base alloy having a composition of Fe: 73.5 atom %, Si: 13.5 atom %, B: 9.0 atom %, Nb: 3.0 atom %, and Cu: 1.0 atom % was obtained. Then, the base alloy was manufactured by evacuating a chamber and thereafter melting the pure metal materials by high-frequency heating.
Then, the manufactured base alloy was heated and molten to be turned into a metal in a molten state at 1300° C. This metal was thereafter sprayed by a gas atomizing method in predetermined conditions shown in Table 8 below, and powders were prepared. In Experiment 3, Sample No. 304 to Sample No. 307 were manufactured by changing a gas spray temperature and a vapor pressure in a chamber. The vapor pressure was adjusted using an Ar gas whose dew point had been adjusted.
Each of the powders before the heat treatment underwent an X-ray diffraction measurement for confirmation of existence of crystals. In addition, a restricted visual field diffraction image and a bright field image were observed by a transmission electron microscope. As a result, it was confirmed that each powder had no crystals and was completely amorphous.
Then, each of the obtained powders underwent a heat treatment and thereafter measured with respect to coercivity. Then, a Fe composition network was analyzed variously. A heat treatment temperature of a sample having a Fe—Si-M-B—Cu—C based composition was 550° C., a heat treatment temperature of a sample having a Fe-M′-B—C based composition was 600° C., and a heat treatment temperature of a sample having a Fe—Si—P—B—Cu—C based composition was 450° C. The heat treatment was carried out for 1 hour. In Experiment 3, a coercivity of 30 A/m or less was considered to be favorable in the Fe—Si-M-B—Cu—C based compositions (Sample No. 304 and Sample No. 305), and a coercivity of 100 A/m or less was considered to be favorable in the Fe-M′-B—C based compositions (Sample No. 306 and Sample No. 307).
In Sample No. 305 and Sample No. 307, a favorable Fe network was formed by appropriately carrying out a heat treatment against the completely amorphous powders. In comparative examples of Sample No. 304 and Sample No. 306, whose gas temperature of 30° C. was too low and vapor pressure of 25 hPa was too high, however, the number of maximum points after the heat treatment was small, no favorable Fe composition network was formed, and coercivity was high.
When comparing comparative examples and examples shown in Table 8, it was found that an amorphous soft magnetic alloy powder was obtained by changing a gas spray temperature, and that the number of maximum points of Fe increased and a Fe composition network structure was obtained in the same manner as a ribbon by carrying out a heat treatment against the amorphous soft magnetic alloy powder. In addition, coercivity tended to be small by having a Fe network structure in the same manner as the ribbons of Experiments 1 and 2.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-194634 | Sep 2016 | JP | national |
