Patent Application
20250010365
The present disclosure relates to an insulation-coated soft magnetic metal powder, a dust core, an electronic element, an electronic device, an electric motor, and a generator.
Patent Document 1 discloses ferromagnetic powder for a dust core in which 0.1 to 10 vol % of a ZrO2 sol is added to an atomized iron powder. In addition, Patent Document 2 describes an insulation-coated soft magnetic metal powder in which zirconium oxide is used.
In an insulation-coated soft magnetic metal powder, loss reduction has been attempted by coating a soft magnetic metal particle with an insulation layer. However, there has been a problem that insulation property decreases when the temperature is increased to a predetermined temperature or higher during the production of an insulation-coated soft magnetic metal powder.
The present disclosure has been made in view of the above circumstances. An object of the present disclosure is to achieve loss reduction of an insulation-coated soft magnetic metal powder. The present disclosure can be realized in the following form.
According to the present disclosure, loss reduction of the insulation-coated soft magnetic metal powder can be achieved.
Here, desirable examples of the present disclosure are shown.
Hereinafter, the present disclosure will be described in detail. In the description herein, when “to” is used to describe a numerical value range, the lower limit value and the upper limit value are included unless otherwise specified. For example, when “10 to 20” is described, “10” as the lower limit value and “20” as the upper limit value are both included. That is, “10 to 20” is equivalent to “10 or more and 20 or less”.
An insulation-coated soft magnetic metal powder 1 includes: soft magnetic metal particles 2 having an average equivalent circle diameter of 10 μm to 100 μm; and an insulation layer 3 formed on a surface of each of the soft magnetic metal particles 2. The insulation layer 3 contains an oxide including Zr element. With respect to the insulation-coated soft magnetic metal powder 1, when the oxide is measured at 25° C. by XRD (X-ray diffraction), the strongest peak is a cubic peak or a tetragonal peak, and the intensity of a monoclinic peak is not greater than one-tenth of the intensity of the strongest peak.
The soft magnetic metal particles 2 are not limited in particular as long as they are metal particles being soft magnetic, and a wide range of such metal particles can be used. As the soft magnetic metal particles 2, a wide range of particles, such as those of pure iron and those of an iron-based alloy that are soft magnetic, can be used. As the iron-based alloy, an Fe—Si alloy, an Fe—Si—Cr alloy, an Fe—Si—Al alloy (sendust), an Ni—Fe alloy (permalloy), an Ni—Fe—Mo alloy (supermalloy), an Fe-based amorphous alloy, an Fe—Co alloy, or the like can be appropriately used. Among these, an Fe—Si alloy, an Fe—Si—Cr alloy, an Fe—Si—Al alloy (sendust), an Ni—Fe alloy (permalloy), and an Ni—Fe—Mo alloy (supermalloy) are preferable from the viewpoint of magnetic permeability, coercive force, and frequency characteristics.
When an Fe—Si alloy is used, an alloy having a composition composed of, for example, 0.1 mass % to 10 mass % of Si, and Fe and inevitable impurities as the remainder, can be used.
When an Fe—Si—Cr alloy is used, an alloy having a composition composed of, for example, 0.1 mass % to 10 mass % of Si, 10 mass % to 20 mass % of Cr, and Fe and inevitable impurities as the remainder, can be used.
The average equivalent circle diameter of the soft magnetic metal particles 2 is 10 μm or more and 100 μm or less, preferably 25 μm or more and 100 μm or less, and more preferably 50 μm or more and 100 m or less. The average equivalent circle diameter of the soft magnetic metal particles 2 can be changed as appropriate depending on the frequency band that is used. In particular, when it is assumed to be used in a high frequency band exceeding 100 kHz, the average equivalent circle diameter is more preferably 10 μm or more and 25 μm or less.
The average equivalent circle diameter of the soft magnetic metal particles 2 can be obtained by calculating an area-equivalent circle diameter from each particle area obtained through observation of a cross section by an FE-SEM. For example, in a case of a dust core 10, the dust core 10 including the insulation-coated soft magnetic metal powder 1 is molded, and a cross section of the dust core 10 is observed to obtain the average equivalent circle diameter (see
The insulation layer 3 contains an oxide including Zr (zirconium) element. When the insulation layer 3 is observed by a TEM (transmission electron microscope), particles forming the insulation layer 3 are confirmed. At least a part of the particles is formed by a crystal of the above oxide. The average equivalent circle diameter of the particles forming the insulation layer 3 is not limited in particular. From the viewpoint of reducing eddy current loss, the average equivalent circle diameter of the particles forming the insulation layer 3 is preferably 20 nm or more and 50 nm or less. The average equivalent circle diameter of the particles forming the insulation layer 3 can be controlled by adjusting the particle diameter of the raw material of the insulation layer 3.
The average equivalent circle diameter of the particles forming the insulation layer 3 can be obtained by calculating an area-equivalent circle diameter from each particle area obtained through observation of a cross section by a TEM. For example, in a case of the dust core 10, the dust core 10 including the insulation-coated soft magnetic metal powder 1 is molded, and a cross section of the dust core 10 is observed to obtain the average equivalent circle diameter. Specifically, an area-equivalent circle diameter is calculated from each particle area obtained through observation of a cross section of the dust core 10 by a TEM, and the area-equivalent circle diameter is used for the average equivalent circle diameter. More specifically, the average equivalent circle diameter is obtained as follows. In observation fields of view of five squares each being 300 nm×300 nm, multiple particles that can be observed without missing parts are focused on. The diameter of an ideal circle (perfect circle) having an area equal to the area (projected area) of each particle image (area-equivalent circle diameter) is calculated as an equivalent circle diameter of each particle. Then, the respective equivalent circle diameters of the particles are arithmetically averaged, whereby the average equivalent circle diameter is obtained. The equivalent circle diameter of each particle and the average equivalent circle diameter can be obtained by using general image analysis software.
The above oxide is preferably stabilized zirconia or partially stabilized zirconia from the viewpoint of appropriate loss reduction of the insulation-coated soft magnetic metal powder 1. Stabilized zirconia is zirconia obtained by solid-solving a stabilizer in ZrO2 (zirconia) such that cubic crystals are stably present at room temperature (25° C.). Stabilized zirconia can have a cubic fluorite structure. Partially stabilized zirconia is zirconia obtained by solid-solving a stabilizer by a smaller amount than that for stabilized zirconia in ZrO2, and in general, cubic crystals and tetragonal crystals are present in a dispersed manner at room temperature.
Examples of the stabilizer include at least one type of an oxide of Y (yttrium), Ca (calcium), Mg (magnesium), and other rare earth elements. Examples of the other rare earth elements include La (lanthanum), Ce (cerium), Nd (neodymium), Sm (samarium), Gd (gadolinium), Dy (dysprosium), Er (erbium), and Yb (ytterbium).
The above oxide is preferably stabilized zirconia or partially stabilized zirconia that contains yttria (Y2O3). When producing stabilized zirconia or partially stabilized zirconia, Ca is heated to 1100° C. or higher and then reacted with ZrO2, or Mg is heated to 1300° C. or higher and then reacted with ZrO2. Meanwhile, Y reacts with ZrO2 even at 1000° C. or lower, and thus, stabilized zirconia or partially stabilized zirconia that contains yttria can be easily and inexpensively produced. In addition, Y is inexpensive as compared with the other rare earth elements and is advantageous in terms of cost.
From the viewpoint of inhibiting generation of monoclinic ZrO2, the amount of yttria in stabilized zirconia or partially stabilized zirconia is preferably 2 mol % or more, and more preferably 7 mol % or more. From the viewpoint of inhibiting generation of a Zr3Y4O12 phase, the amount of yttria in stabilized zirconia or partially stabilized zirconia is preferably 20 mol % or more. From these viewpoints, the amount of yttria in stabilized zirconia or partially stabilized zirconia is preferably 2 mol % or more and 20 mol % or less, and more preferably 7 mol % or more and 20 mol % or less. The amount of yttria in stabilized zirconia or partially stabilized zirconia may be 15 mol % or less, may be 12 mol % or less, or may be 10 mol % or less.
The above oxide may be stabilized zirconia or partially stabilized zirconia that contains calcia (CaO).
From the viewpoint of inhibiting generation of monoclinic ZrO2, the amount of calcia in stabilized zirconia or partially stabilized zirconia is preferably 3 mol % or more, more preferably 7 mol % or more, and further preferably 10 mol % or more. From the viewpoint of inhibiting generation of a CaZr4O9 phase or a CaZrO3 phase, the amount of calcia in stabilized zirconia or partially stabilized zirconia is preferably 20 mol % or less. From these viewpoints, the amount of calcia in stabilized zirconia or partially stabilized zirconia is preferably 3 mol % or more and 20 mol % or less, and more preferably 7 mol % or more and 20 mol % or less.
The above oxide may be stabilized zirconia or partially stabilized zirconia that contains magnesia (MgO).
From the viewpoint of inhibiting generation of monoclinic ZrO2, the amount of magnesia in stabilized zirconia or partially stabilized zirconia is preferably 4 mol % or more, more preferably 7 mol % or more, and further preferably 10 mol % or more. From the viewpoint of inhibiting generation of an MgO phase, the amount of magnesia in stabilized zirconia or partially stabilized zirconia is preferably 20 mol % or less. From these viewpoints, the amount of magnesia in stabilized zirconia or partially stabilized zirconia is preferably 4 mol % or more and 20 mol % or less, and more preferably 7 mol % or more and 20 mol % or less.
(3) Requirements about Intensity of Monoclinic Peak in Oxide Including Zr Element
With respect to the insulation-coated soft magnetic metal powder 1, when the oxide is measured at 25° C. by XRD, the strongest peak is a cubic peak or a tetragonal peak, and the intensity of a monoclinic peak is not greater than one-tenth of the intensity of the strongest peak. When multiple monoclinic peaks are observed, the peak having the highest intensity out of the multiple monoclinic peaks is specified as the monoclinic peak. When the strongest peak is a cubic peak or a tetragonal peak, and no monoclinic peak is observed, the intensity of the monoclinic peak is 0, and thus, is not greater than one-tenth of the intensity of the strongest peak.
A fact that the strongest peak is a cubic peak or a tetragonal peak, and the intensity of a monoclinic peak is not greater than one-tenth of the intensity of the strongest peak serves as one index indicating that, in the oxide, the amount of monoclinic ZrO2 is small and a large amount of ZrO2 is present as being cubic or tetragonal. In XRD, the peak of tetragonal ZrO2 and the peak of cubic ZrO2 overlap each other and are difficult to be separated from each other, and thus, a fact that the strongest peak is a cubic peak or tetragonal peak is set as one of the present requirements. From the viewpoint of reducing eddy current loss, ZrO2 is preferably present as cubic ZrO2. That is, it is preferable that, when the oxide is measured at 25° C. by XRD, a peak of cubic ZrO2 is detected.
The crystal phase showing the strongest peak of the oxide including Zr element can be controlled, for example, through addition of a stabilizer and the concentration of the stabilizer, adjustment of the particle diameter of the raw material of the insulation layer 3, adjustment of a heat treatment condition and the like in a production method described later, and the like.
The strongest peak of the oxide including Zr element can be obtained through XRD measurement of the dust core 10 including the insulation-coated soft magnetic metal powder 1. The XRD measurement is performed under the following conditions, for example.
In the diffraction pattern of the dust core 10 obtained in the XRD measurement, peaks derived from the soft magnetic metal particles 2, a measurement cell, etc., are excluded, and a peak derived from the oxide including Zr element is obtained. When the number of peaks derived from the oxide including Zr element is one, the peak is specified as the strongest peak. When there are multiple peaks derived from the oxide including Zr element, the peak having the highest intensity out of the multiple peaks is specified as the strongest peak.
More specific description will be given below with reference to
In the present embodiment, the reason why loss can be reduced in the insulation-coated soft magnetic metal powder 1 (the dust core 10) is not certain, but can be inferred as follows.
Usually, pure ZrO2 is present as being monoclinic at normal temperature. Monoclinic ZrO2 undergoes phase transformation from monoclinic to tetragonal during increase in temperature, and at this time, undergoes 4% volume shrinkage. Conversely, during decrease in temperature, Monoclinic ZrO2 undergoes volume expansion. In a case where a predetermined amount or more of monoclinic ZrO2 is included as the oxide, shrinkage and expansion are caused when annealing, etc., are performed for the purpose of removing strain of metal (reducing hysteresis loss), and there is a concern that eddy current loss due to breakage of the insulation layer 3 caused by the shrinkage and the expansion may increase. The temperature at which this phase transformation occurs is 1170° C. according to an equilibrium diagram. When ZrO2 is nanoparticles, the temperature at which the phase transformation occurs is lowered, and the phase transformation may occur even at 750° C.
In the present embodiment, cubic ZrO2 in a high temperature phase is stabilized even at room temperature through, for example, addition of a stabilizer (e.g., yttrium), so that annealing can be performed at a high temperature without causing the phase transformation of ZrO2. As a result, it is inferred that, while increase in eddy current loss due to breakage of the insulation layer 3 is suppressed, hysteresis loss can be sufficiently reduced by annealing, and loss reduction of the insulation-coated soft magnetic metal powder 1 (the dust core 10) can be achieved.
The above insulation-coated soft magnetic metal powder 1 is useful as a material of a dust core. That is, the dust core 10 preferably includes the insulation-coated soft magnetic metal powder 1. In the description of the dust core 10, regarding similar points, the description of the insulation-coated soft magnetic metal powder 1 above will be referred to.
The production method for the insulation-coated soft magnetic metal powder 1 and the dust core 10 is not limited in particular. An example is described below.
A suspension including zirconia particles, yttrium acetate, and a small amount of an organic component is mixed with a soft magnetic metal powder, and the mixture is dried. The soft magnetic metal powder is not limited in particular as long as it is metal particles being soft magnetic, and a wide range of such metal particles can be used. The source of yttrium may be an oxide of yttrium or a nitrate other than yttrium acetate. The obtained dry powder is subjected to heat treatment to obtain the insulation-coated soft magnetic metal powder 1. The condition for this heat treatment is not limited in particular. As the heat treatment condition, for example, conditions of heat treatment temperature of 750° C. to 1200° C. and an inert atmosphere (N2 atmosphere, Ar atmosphere) are appropriately adopted.
The insulation-coated soft magnetic metal powder 1 is put in a mold and subjected to press molding at a molding pressure of 1.0 GPa to 1.7 GPa, to obtain a molded body.
The obtained molded body is subjected to heat treatment (annealing) to obtain the dust core 10. As the heat treatment condition, for example, conditions of: heat treatment temperature of 600° C. to 1200° C.; a temperature increase rate at 350° C. to 600° C. of 3° C./min or more; a holding time of 10 minutes to 120 minutes; and an inert atmosphere (N2 atmosphere, Ar atmosphere) are appropriately adopted.
The heat treatment condition is changed as appropriate according to the types of the soft magnetic metal powder and the oxide that are used.
The dust core 10 above is suitably used in an electronic element. Examples of the electronic element include an inductor, a choking coil, a noise filter, a reactor, and a transformer. The electronic element includes the dust core 10 and a coil, for example.
Inductors 100, 20, 30 shown in
A noise filter 40 shown in
A reactor 50 shown in
A transformer 60 shown in
The dust core 10 above is suitably used in an electronic device. The electronic device includes an electronic element. Examples of the electronic element include the electronic elements described above.
A noise filter 70 shown in
The dust core 10 above is suitably used in an electric motor. Examples of the electric motor include a motor, a linear actuator, and the like.
A motor 80 shown in
A generator 90 shown in
Hereinafter, the present disclosure will be further specifically described with reference to Examples.
A suspension including zirconia particles, yttrium acetate, a small amount of an organic component, and a solvent was mixed with pure iron particles, and the mixture was dried and subjected to heat treatment. The concentration of oxide particles in the suspension was set to 0.1 mass % to 2 mass % with respect to the entire suspension. The amount of the suspension that was mixed with soft magnetic metal particles was set such that the entire amount of the contained oxide particles was 6 volume % with respect to the soft magnetic metal particles. The amount of yttrium acetate was set such that Zr element was 84 mol % and Y element was 16 mol % (8 mol % in terms of Y2O3). The conditions of the heat treatment (first heat treatment) were a heat treatment temperature of 900° C. and in nitrogen. The heat treatment was performed for the purpose of removing the organic component in the insulation layer and advancing solid solution reaction of the oxide. In this manner, an insulation-coated soft magnetic metal powder of Example 1 was obtained.
The obtained insulation-coated soft magnetic metal powder was put in a mold and subjected to press molding at a molding pressure of 1.7 GPa, whereby a press molded body having a diameter of 10 mm or a toroidal shape (outer diameter: 8 mm, inner diameter: 4.5 mm, height: 1.5 mm) was obtained. This molded body was subjected to heat treatment (second heat treatment). The conditions of the heat treatment were a heat treatment temperature of 600° C. to 1200° C., a temperature increase rate in a range of 350° C. to 600° C. of 3° C./min to 10° C./min, and in nitrogen. In this manner, a dust core of Example 1 was obtained.
A dust core of Example 2 was obtained in the same manner as that in Example 1 except that Fe-3.5 mass % Si alloy particles were used instead of the pure iron particles.
A dust core of Comparative Example 1 was obtained in the same manner as that in Example 1 except that yttrium acetate was not added.
A dust core of Comparative Example 2 was obtained in the same manner as that in Example 2 except that yttrium acetate was not added.
Table 1 collectively shows characteristics of the soft magnetic metal particles, the insulation layer, and the eddy current loss of Examples and Comparative Examples.
The column of “Crystal phase of strongest peak” indicates the crystal phase of the strongest peak specified by the method described in the embodiment.
In the column of “Intensity of monoclinic peak relative to intensity of strongest peak”, evaluation was performed, with respect to the intensity of the strongest peak and the intensity of the monoclinic peak specified by the method described in the embodiment, according to the criteria below. When the crystal phase of the intensity of the strongest peak is monoclinic, the intensity of the monoclinic peak and the intensity of the strongest peak are the same, and thus, the intensity of the monoclinic peak relative to the intensity of the strongest peak is 1.
Not greater than 1/10: the intensity of the monoclinic peak is not greater than one-tenth of the intensity of the strongest peak.
Greater than 1/10: the intensity of the monoclinic peak is greater than one-tenth of the intensity of the strongest peak.
In the column of “Satisfaction of requirement about intensity of monoclinic peak”, evaluation was performed according to the criteria below.
Satisfied: “Crystal phase of strongest peak” is cubic or tetragonal, and “Intensity of monoclinic peak relative to intensity of strongest peak” is not greater than 1/10.
Not satisfied: “Crystal phase of strongest peak” is not cubic or tetragonal, or “Intensity of monoclinic peak relative to intensity of strongest peak” is greater than
Eddy current loss (kW/m3) of the obtained dust core was measured under conditions of a frequency of 10 kHz and a magnetic flux density of 0.1 T. The measurement results are also shown in Table 1.
Examples 1, 2 satisfy requirements (a), (b), (c), (d) below.
In contrast to this, Comparative Examples 1, 2 do not satisfy requirement (d).
Examples 1, 2 had low eddy current losses as compared with those of Comparative Examples 1, 2.
Example 1, in which the composition of the soft magnetic metal particles was pure iron, had a low eddy current loss as compared with that of Comparative Example 1 having the same composition. Example 2, in which the composition of the soft magnetic metal particles was an Fe-3.5 mass % Si alloy, had a low eddy current loss as compared with that of Comparative Example 2 having the same composition. From these results, it was suggested that the composition of the soft magnetic metal particles is not limited in particular and that a wide range of the soft magnetic metal particles is applicable.
According to the present embodiment, loss reduction of the insulation-coated soft magnetic metal powder can be achieved.
The present disclosure is not limited to the embodiment described above in detail, and various modifications or variations can be made without departing from the scope of the claims.
The dust core of the present disclosure is particularly suitably used for usages as a motor, a transformer, a reactor, an inductor, a noise filter, and the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-081309 | May 2022 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2023/017052 | 5/1/2023 | WO |
