JP7702238B2 - Soft magnetic alloy powder, magnetic cores, magnetic components and electronic devices - Google Patents

Description

The present invention relates to soft magnetic alloy powders, magnetic cores, magnetic components, and electronic devices.

In recent years, there has been a demand for lower power consumption and higher efficiency in electronic, information, and communication devices, especially electronic devices. Furthermore, these demands are becoming even stronger as we move toward a low-carbon society. For this reason, there is a demand for reduced energy loss and improved power efficiency in the power supply circuits of electronic, information, and communication devices, especially electronic devices.

Here, in order to reduce energy loss and improve power supply efficiency, it is necessary to obtain soft magnetic alloy powder that has excellent soft magnetic properties and can improve the filling rate when used in magnetic cores.

Patent Document 1 describes a soft magnetic metal powder with improved Wardle sphericity. It also describes that by improving the sphericity, it is possible to manufacture superior power inductors.

Patent Document 2 describes a Co-based amorphous alloy ribbon. It also describes that the magnetic permeability and squareness ratio are improved by setting the S content to 30 ppm or less and the Al content to 40 ppm or less.

JP 2016-25352 A Japanese Patent Application Publication No. 3-173750

The present invention aims to provide a soft magnetic alloy powder that can produce a magnetic core with improved magnetic permeability without significantly changing the particle size.

In order to achieve the above object, the soft magnetic alloy powder of the present invention comprises:
A soft magnetic alloy powder having a main component represented by the composition formula (Co _(1-(α+β)) X1 _α X2 _β ) _{(1-(a+b+c+d+e+f))} M _a B _b P _c Si _d Cr _e S _f (atomic ratio),
X1 is one or more selected from the group consisting of Fe and Ni;
X2 is one or more selected from the group consisting of Al, Mn, Ag, Zn, Sn, As, Sb, Cu, Bi, N, O, C and rare earth elements;
M is one or more selected from the group consisting of Nb, Hf, Zr, Ta, Mo, W, Ti and V;
0<a≦0.140
0.160<b≦0.250
0≦c≦0.200
0≦d≦0.250
0≦e≦0.030
0≦f≦0.010
0.160<b+c+d+e+f≦0.430
0.500<1-(a+b+c+d+e+f)<0.840
α≧0
β≧0
0≦α+β<0.50
and
The soft magnetic alloy powder has a glass transition point Tg and a melting point Tm,
900°C≦Tm≦1200°C.

The soft magnetic alloy powder according to the present invention has the above composition and has the above-mentioned glass transition point and melting point, which makes the magnetic permeability of the soft magnetic alloy powder itself favorable, and further increases the sphericity of the powder particles and reduces the proportion of irregularly shaped particles. As a result, the magnetic permeability of a magnetic core using the soft magnetic alloy powder can be improved without changing the particle size of the soft magnetic alloy powder.

The powder particles contained in the soft magnetic alloy powder according to the present invention may have an average circularity of 0.93 or more, and the cumulative percentage of the powder particles having a circularity of from 0.50 to 0.50 may be 2.0% or less.

The powder particles contained in the soft magnetic alloy powder according to the present invention may have an average circularity of 0.95 or more, and the cumulative percentage of the powder particles having a circularity of from the lowest to 0.50 may be 1.5% or less.

The soft magnetic alloy powder according to the present invention may have a value obtained by dividing the Co content by the B content greater than 2.000 and less than 5.000.

The soft magnetic alloy powder according to the present invention may be amorphous.

The soft magnetic alloy powder according to the present invention may have nanocrystals.

The magnetic core according to the present invention contains the soft magnetic alloy powder described above.

The magnetic component according to the present invention contains the soft magnetic alloy powder described above.

The electronic device according to the present invention contains the soft magnetic alloy powder described above.

This is the observation result of powder particles with high sphericity using Morphologi G3. This is the observation result of powder particles with low sphericity using Morphologi G3. 13 is a graph showing the relationship between circularity and cumulative number ratio. 4 is a graph showing the portion of FIG. 3 with circularity of 0.4 to 0.6. 1 is a graph showing melting points Tm. 1 is a graph showing the glass transition point Tg and the crystallization onset point Tx. 7 is a graph showing the portion of FIG. 6 where temperatures are between 450° C. and 600° C. FIG. 1 is a schematic diagram of a metal powder manufacturing apparatus. FIG. 8B is an enlarged schematic view of a main part of FIG. 8A.

The following describes an embodiment of the present invention.

The soft magnetic alloy powder of the present embodiment is a soft magnetic alloy powder having a main component represented by the composition formula (Co _(1-(α+β)) X1 _α X2 _β ) (1-(a+b+c+ _{d +e+f))} M _a B _b P _c Si d Cr _e S _f (atomic ratio),
X1 is one or more selected from the group consisting of Fe and Ni;
X2 is one or more selected from the group consisting of Al, Mn, Ag, Zn, Sn, As, Sb, Cu, Bi, N, O, C and rare earth elements;
M is one or more selected from the group consisting of Nb, Hf, Zr, Ta, Mo, W, Ti and V;
0<a≦0.140
0.160<b≦0.250
0≦c≦0.200
0≦d≦0.250
0≦e≦0.030
0≦f≦0.010
0.160<b+c+d+e+f≦0.430
0.500<1-(a+b+c+d+e+f)<0.840
α≧0
β≧0
0≦α+β<0.50
and
The soft magnetic alloy powder has a glass transition point Tg and a melting point Tm,
It is characterized in that 900°C≦Tm≦1200°C.

In general, soft magnetic alloy powders having a composition containing a large amount of Co have a higher relative magnetic permeability than soft magnetic alloy powders having a composition containing a large amount of Fe. In addition, soft magnetic alloy powders having a composition containing a large amount of Co tend to have high corrosion resistance and electrical resistance, and low dielectric loss. Furthermore, soft magnetic alloy powders having a composition containing a large amount of Co have a lower melting point than soft magnetic alloy powders having a composition containing a large amount of Fe. As a result, when producing soft magnetic alloy powders by an atomization method such as gas atomization, which will be described later, it is easy to lower the atomization temperature. Note that the melting point of the molten metal made of the soft magnetic alloy before atomization is usually the same as the melting point of the soft magnetic alloy powder obtained by atomization.

The soft magnetic alloy powder according to this embodiment has the above composition, glass transition point, and melting point, which allows the powder particles to have a good particle shape. Specifically, by having the above composition, glass transition point, and melting point, it is possible to obtain a soft magnetic alloy powder consisting of powder particles with a high average sphericity. Furthermore, it is possible to obtain a soft magnetic alloy powder with a small number of powder particles with a particle shape with a low degree of circularity, that is, a soft magnetic alloy powder with a small proportion of irregularly shaped particles.

The soft magnetic alloy powder according to this embodiment is made of powder particles having the above particle shape, and therefore can improve the filling rate of magnetic cores and the like that use the soft magnetic alloy powder, and can improve various properties such as the relative permeability of magnetic cores and the like. Hereinafter, powder particles may be simply referred to as particles.

In addition, when the soft magnetic alloy powder of this embodiment is heat treated, nanocrystals with a crystal grain size of 50 nm or less are likely to precipitate. In other words, the soft magnetic alloy powder of this embodiment is likely to be used as the starting material for soft magnetic alloy powder in which nanocrystals have been precipitated. Whether or not the powder contains nanocrystals and whether or not it contains amorphous matter can be confirmed by XRD.

In addition, when the soft magnetic alloy powder of this embodiment contains nanocrystals, each particle contains a large number of nanocrystals. In other words, the particle size of the soft magnetic alloy powder described below is different from the crystal grain size of the nanocrystals.

The components of the soft magnetic alloy powder according to this embodiment are described in detail below.

M is one or more selected from the group consisting of Nb, Hf, Zr, Ta, Mo, W, Ti and V.

The content (a) of M satisfies 0<a≦0.140. It may also satisfy 0.001≦a≦0.140. It may also satisfy 0.003≦a≦0.140, or 0.040≦a≦0.100. If M is not included, the soft magnetic alloy powder is less likely to have a glass transition point Tg. As a result, the circularity of the particles is likely to decrease, and the relative permeability is likely to decrease. If a is too large, the melting point Tm of the soft magnetic alloy powder is likely to decrease. As a result, the circularity of the particles is likely to decrease, the proportion of irregularly shaped particles in the soft magnetic alloy powder increases, and the relative permeability is likely to decrease. Furthermore, the saturation magnetic flux density is likely to decrease. In addition, from the viewpoint of making it easier to decrease the coercive force, it is preferable that 0.010≦a≦0.140.

The B content (b) satisfies 0.160<b≦0.250. It may also satisfy 0.180≦b≦0.250. If b is too small, the melting point Tm of the soft magnetic alloy may become too high, making it impossible to inject the molten metal and producing soft magnetic alloy powder. If b is too large, the melting point Tm becomes too low, increasing the proportion of irregularly shaped particles in the soft magnetic alloy powder, increasing the coercive force, and decreasing the relative permeability.

The P content (c) satisfies 0≦c≦0.200. In other words, P need not be contained. More preferably, it satisfies 0≦c≦0.150, and even more preferably, it satisfies 0.010≦c≦0.050. If c is too large, the melting point Tm of the soft magnetic alloy powder becomes too low, the proportion of irregular-shaped particles in the soft magnetic alloy powder increases, the coercive force increases, and the relative permeability decreases.

The Si content (d) satisfies 0≦d≦0.250. In other words, Si need not be contained. More preferably, it satisfies 0≦d≦0.200. If d is too large, the melting point Tm of the soft magnetic alloy powder becomes too low, the circularity decreases, the proportion of irregularly shaped particles in the soft magnetic alloy powder increases, the coercive force increases, and the relative permeability decreases.

The Cr content (e) satisfies 0≦e≦0.030. In other words, Cr does not have to be contained. More preferably, it satisfies 0.001≦e≦0.010. The inclusion of Cr increases the corrosion resistance of the soft magnetic alloy powder. If e is too large, the proportion of irregularly shaped particles in the soft magnetic alloy powder increases, the coercive force increases, and the relative permeability decreases.

The S content (f) satisfies 0≦f≦0.010. In other words, S does not have to be contained. The larger f is, the smaller the proportion of irregularly shaped particles in the soft magnetic alloy powder, but if f is too large, the coercive force increases and the relative permeability decreases.

The soft magnetic alloy powder according to this embodiment satisfies 0.160<b+c+d+e+f≦0.430. It may also satisfy 0.190≦b+c+d+e+f≦0.430. If b+c+d+e+f is too large, it is not possible to obtain a soft magnetic alloy powder with a high relative magnetic permeability.

Furthermore, the soft magnetic alloy powder according to this embodiment satisfies 0.500<1-(a+b+c+d+e+f)<0.840. It may also satisfy 0.550≦1-(a+b+c+d+e+f)≦0.800. If 1-(a+b+c+d+e+f) is too small or too large, it is not possible to obtain a soft magnetic alloy powder with a high relative magnetic permeability.

In addition, in the soft magnetic alloy powder of this embodiment, a portion of Co may be replaced with X1 and/or X2.

X1 is one or more selected from the group consisting of Fe and Ni. The content of X1 may be α=0. In other words, X1 may not be contained. In addition, the number of atoms of X1 is preferably 40 at% or less, with the number of atoms in the entire composition being 100 at%. In other words, it is preferable to satisfy 0≦α{1-(a+b+c+d+e+f)}≦0.400. It is even more preferable to satisfy 0≦α{1-(a+b+c+d+e+f)}≦0.100. In addition, the coercive force is more likely to decrease and the relative permeability is more likely to increase when a small amount of Fe is contained than when no Fe is contained at all. In particular, the coercive force is more likely to decrease and the relative permeability is more likely to increase when the atomic ratio of Co/Fe is 5 to 20.

X2 is one or more selected from the group consisting of Al, Mn, Ag, Zn, Sn, As, Sb, Cu, Bi, N, O, C, and rare earth elements. The content of X2 may be β=0. In other words, X2 may not be contained. In addition, the number of atoms of X2 is preferably 5.0 at% or less, with the number of atoms in the entire composition being 100 at%. In other words, it is preferable to satisfy 0≦β{1-(a+b+c+d+e+f+g)}≦0.050.

The range of substitution amount of Co with X1 and/or X2 is less than half of Co based on the number of atoms. That is, 0≦α+β<0.50. It may also be 0≦α+β≦0.40. If α+β is too large, particularly if α+β≧0.50, the melting point of the soft magnetic alloy becomes too high, making it impossible to spray the molten metal and producing soft magnetic alloy powder.

Even if the melting point of the soft magnetic alloy is high, it is possible to spray the molten metal by increasing the atomization temperature. However, if the atomization temperature is high, the circularity of the soft magnetic alloy powder is likely to decrease, the proportion of irregularly shaped particles in the soft magnetic alloy powder is likely to increase, the coercive force is likely to increase, and the relative permeability is likely to decrease.

In addition, the value obtained by dividing the Co content by the B content (hereinafter, may be referred to as Co/B) may be greater than 2.000 and less than 5.250, greater than 2.000 and less than 5.000, or may be 2.340 or more and 4.000 or less. By having Co/B within the above range, the melting point Tm of the soft magnetic alloy powder described below tends to be lower, and the atomization temperature can be easily reduced.

The soft magnetic alloy powder of this embodiment may contain elements other than the elements contained in the main components as unavoidable impurities to the extent that they do not significantly affect the properties such as the relative permeability. For example, the soft magnetic alloy powder may contain 0.1% by mass or less relative to 100% by mass of the soft magnetic alloy powder.

The following describes how to evaluate the particle shape and particle size of the soft magnetic alloy powder of this embodiment.

The sphericity of the soft magnetic alloy powder may be evaluated by evaluating the circularity of a projection of the particle shape of the soft magnetic alloy powder.

In this embodiment, the particle shape is evaluated using a Morphologi G3 (Malvern Panatical). The Morphologi G3 is a device that can disperse powder with air, project and evaluate the individual particle shapes. The shape of particles with diameters ranging from approximately 0.5 μm to several mm can be evaluated using an optical microscope or a laser microscope. Specifically, as can be seen from the particle shape measurement results 1 and 2 shown in Figures 1 and 2, a large number of particle shapes can be projected and evaluated at once. However, in reality, a much larger number of particle shapes can be projected and evaluated at once than those shown in the particle shape measurement results 1 and 2 shown in Figures 1 and 2. Note that Figure 1 shows the projection results of powder particles with good particle shapes and high sphericity, and Figure 2 shows the projection results of powder particles with poor particle shapes and low sphericity.

Morphologi G3 can create and evaluate projection images of many particles at once, making it possible to evaluate the shapes of many particles in a short time compared to conventional evaluation methods such as SEM observation. For example, in the example described below, projection images are created for 20,000 particles, the circularity of each particle is automatically calculated, and the average circularity is calculated on a number basis. In contrast, conventional SEM observation uses SEM images to calculate the circularity of each particle, making it difficult to evaluate the shapes of many particles in a short time.

The circularity of a particle is expressed as 2(πS) ^1/2 /L, where S is the area in the projection and L is the perimeter in the projection. The circularity of a circle is 1, and the closer the circularity of a particle is to 1, the higher the sphericity of the particle.

The soft magnetic alloy powder according to this embodiment has the above composition, which allows the average circularity to be high, specifically, 0.93 or more. The average circularity is preferably 0.95 or more.

The proportion of irregularly shaped particles is evaluated using the following method.

For the 20,000 particles whose circularity was measured, the cumulative number ratio (cumulative frequency) from the lowest circularity was calculated. The smaller the cumulative number ratio from the lowest circularity to 0.50, the smaller the proportion of irregularly shaped particles.

The soft magnetic alloy powder according to this embodiment has the above composition, and therefore the melting point Tm can be set in the range of 900°C≦Tm≦1200°C, and the proportion of irregularly shaped particles can be reduced. The cumulative number ratio from the lowest circularity to 0.50 can be specifically set to 2.5% or less. The cumulative number ratio from the lowest circularity to 0.50 is preferably 1.5% or less. There is no particular lower limit to the cumulative number ratio from the lowest circularity to 0.50. For example, it may be 0.05% or more.

Examples of graphs with circularity on the horizontal axis and cumulative number ratio on the vertical axis are shown in Figures 3 and 4. In the case of the solid line, the cumulative number ratio from the lowest circularity to 0.50 is 1.5% or less. In contrast, in the case of the dotted line, the cumulative number ratio from the lowest circularity to 0.50 is greater than 1.5% and is 2.0% or less. In other words, it can be evaluated that the proportion of irregularly shaped particles is smaller in the case of the solid line than in the case of the dotted line.

The method for evaluating particle size is shown below.

In this embodiment and in the examples described later, particle size is evaluated on a volume basis. There are no particular limitations on the method for measuring the volume-based average particle size (D50). For example, the volume-based average particle size (D50) can be determined using a laser diffraction particle size distribution measuring device.

In this embodiment, there is no particular limit to the average particle size of the soft magnetic metal powder. For example, it may be 5 μm or more and 50 μm or less.

The glass transition point Tg and melting point Tm are explained below with reference to the drawings.

In FIG. 5, the solid line is an example of the results of thermal property measurement by a differential scanning calorimeter (DSC) for the soft magnetic alloy powder of this embodiment (hereinafter, simply referred to as the DSC measurement result), and the dotted line is an example of the DSC measurement result for the Fe-based soft magnetic alloy powder made of amorphous. The heating rate is constant. In general, the melting point is the temperature at which the soft magnetic alloy starts to melt (Tm1 in FIG. 5), and the melting point is the temperature at which melting is completed (Tm2 in FIG. 5). In this application, the melting point Tm is the temperature at which melting is completed (Tm2 in FIG. 5). This is because the temperature at which melting is completed has a greater effect on the atomization temperature and the temperature of the molten metal when performing an atomization method such as gas atomization described later, and has a greater effect on the characteristics of the soft magnetic alloy powder obtained by the atomization method.

In addition, when the temperature of the amorphous soft magnetic alloy powder of this embodiment is increased, a glass transition reaction (endothermic reaction) occurs at a specific temperature. This temperature is the glass transition point Tg. At an even higher temperature, a crystallization reaction (exothermic reaction) occurs at a certain temperature. This temperature is the crystallization onset point Tx. In this case, the supercooled liquid region ΔT is expressed as Tx-Tg.

The supercooled liquid region is related to the stabilization of amorphous matter, and the wider the supercooled liquid region and the larger ΔT, the higher the ability to form amorphous matter. In contrast, if the supercooled liquid region is narrow, the ability to form amorphous matter is low. It is preferable that ΔT is 20°C or higher.

In Figures 6 and 7, the solid line is an example of the thermal property measurement results by DSC for the soft magnetic alloy powder of this embodiment, and the dotted line is an example of the DSC measurement results for the Fe-based soft magnetic alloy powder made of amorphous. The heating rate is constant. The soft magnetic alloy powder of this embodiment has a glass transition point Tg and a crystallization onset point Tx. In contrast, the Fe-based soft magnetic alloy powder made of amorphous does not have a glass transition point Tg. Note that the crystallization onset point of the Fe-based soft magnetic alloy powder made of amorphous is not shown.

The soft magnetic alloy powder of this embodiment has the characteristic that it has a lower Tm and a higher Tg than amorphous Fe-based soft magnetic alloy powder. This allows the atomization temperature to be lowered. This reduces the coercive force of the soft magnetic alloy powder, improves the relative permeability of the soft magnetic alloy powder itself, increases the average circularity of the soft magnetic alloy powder, and reduces the proportion of irregularly shaped particles in the soft magnetic alloy powder. This improves the filling rate of the magnetic core using the soft magnetic alloy powder, and improves the relative permeability.

The manufacturing method of the soft magnetic alloy powder of this embodiment is described below.

The soft magnetic alloy powder of this embodiment can be manufactured, for example, by gas atomization.

The following describes how to manufacture soft magnetic alloy powder using the gas atomization method.

The inventors have found that when the atomizing device shown in Figures 8A and 8B is used as the atomizing device, it is easier to obtain soft magnetic metal powder with a good particle shape.

As shown in FIG. 8A, the atomizing device 10 has a molten metal supply section 20 and a cooling section 30 arranged vertically below the metal supply section 20. In the drawing, the vertical direction is along the Z-axis.

The molten metal supply unit 20 has a heat-resistant container 22 that contains the molten metal 21. In the heat-resistant container 22, the raw materials of each metal element, weighed to form the final composition of the soft magnetic alloy powder, are melted by a heating coil 24 to become the molten metal 21. The temperature during melting, i.e., the temperature of the molten metal 21, can be determined taking into account the melting points of the raw materials of each metal element and the melting point of the molten metal 21 (the above-mentioned Tm), and can be, for example, 1200 to 1600°C.

The molten metal 21 is discharged from the discharge port 23 toward the cooling section 30 as dripping molten metal 21a. High-pressure gas is sprayed from the gas spray nozzle 26 toward the discharged dripping molten metal 21a, and the dripping molten metal 21a becomes numerous droplets that are carried toward the inner surface of the cylinder 32 along the gas flow.

The gas injected from the gas injection nozzle 26 is preferably an inert gas or a reducing gas. Examples of the inert gas that can be used include nitrogen gas, argon gas, and helium gas. Examples of the reducing gas that can be used include ammonia decomposition gas. However, if the molten metal 21 is a metal that is difficult to oxidize, the gas injected from the gas injection nozzle 26 may be air.

The dripping molten metal 21a conveyed toward the inner surface of the cylinder 32 collides with the cooling liquid flow 50 formed in an inverted cone shape inside the cylinder 32, where it is further divided and refined, and is cooled and solidified to become solid alloy powder. The axis O of the cylinder 32 is inclined at a predetermined angle θ1 with respect to the vertical line Z. The predetermined angle θ1 is not particularly limited, but is preferably 0 to 45 degrees. By setting the angle in this range, it becomes easier to eject the dripping molten metal 21a from the discharge port 23 toward the cooling liquid flow 50 formed in an inverted cone shape inside the cylinder 32.

A discharge section 34 is provided below along the axis O of the cylinder 32, and allows the alloy powder contained in the cooling liquid flow 50 to be discharged to the outside together with the cooling liquid. The alloy powder discharged together with the cooling liquid is separated from the cooling liquid in an external storage tank or the like and taken out. The cooling liquid is not particularly limited, but cooling water is used.

Here, the average circularity of the soft magnetic alloy powder finally obtained can be adjusted by adjusting the water pressure of the cooling water. The lower the water pressure, the higher the average circularity of the soft magnetic alloy powder finally obtained, but if the water pressure is too low, the cooling water flow 50 formed in an inverted cone shape cannot be obtained. However, the proportion of irregularly shaped particles does not change much even if the water pressure is changed. There are no particular restrictions on the method of adjusting the water pressure. It can be appropriately determined depending on the method of supplying the cooling water. For example, when the cooling water is supplied by a pump, the water pressure of the cooling water can be adjusted by adjusting the pump pressure.

In this embodiment, the dripping molten metal 21a collides with the cooling liquid flow 50 formed in an inverted cone shape, so the flight time of the droplets of the dripping molten metal 21a is shortened compared to when the cooling liquid flow is along the inner surface 33 of the cylinder 32. When the flight time is shortened, the rapid cooling effect is promoted and the amorphous rate X of the obtained soft magnetic alloy powder increases. Furthermore, the average circularity tends to be high. In addition, when the flight time is shortened, the droplets of the dripping molten metal 21a are less likely to be oxidized, so the fineness of the obtained soft magnetic alloy powder is promoted and the quality of the soft magnetic alloy powder is improved.

In this embodiment, in order to form an inverted cone-shaped coolant flow inside the cylinder 32, the flow of the coolant is controlled in the coolant inlet (coolant outlet) 36 for introducing the coolant into the cylinder 32. The configuration of the coolant inlet 36 is shown in FIG. 8B.

As shown in FIG. 8B, the frame 38 defines an outer portion (outer space) 44 located on the radially outer side of the cylindrical body 32, and an inner portion (inner space) 46 located on the radially inner side of the cylindrical body 32. The outer portion 44 and the inner portion 46 are separated by a partition 40, and the outer portion 44 and the inner portion 46 are connected by a passage portion 42 formed at the upper portion of the partition 40 in the axial center O direction, allowing the coolant to flow.

A single or multiple nozzles 37 are connected to the outer portion 44, and the cooling liquid enters the outer portion 44 from the nozzles 37. In addition, a cooling liquid discharge portion 52 is formed below the inner portion 46 in the axial direction O, and the cooling liquid in the inner portion 46 is discharged (extracted) from there into the inside of the cylinder 32.

The outer peripheral surface of the frame 38 is the flow passage inner peripheral surface 38b that guides the flow of the cooling liquid inside the inner portion 46, and an outer convex portion 38a1 is formed at the lower end 38a of the frame 38, continuing from the flow passage inner peripheral surface 38b of the frame 38 and protruding radially outward. Therefore, the ring-shaped gap between the tip of the outer convex portion 38a1 and the inner surface 33 of the cylindrical body 32 becomes the cooling liquid discharge portion 52. A flow passage deflection surface 62 is formed on the upper surface of the outer convex portion 38a1 on the flow passage side.

8B, the radial width D1 of the cooling liquid discharge portion 52 is narrower than the radial width D2 of the main portion of the inner portion 46 due to the outward convex portion 38a1. Since D1 is narrower than D2, the cooling liquid flowing down the axis O along the inner peripheral surface 38b inside the inner portion 46 next flows along the flow path deflection surface 62 of the frame 38 and collides with the inner surface 33 of the cylinder 32 and is reflected. As a result, as shown in FIG. 8A, the cooling liquid is discharged from the cooling liquid discharge portion 52 into the inside of the cylinder 32 in an inverted cone shape, forming a cooling liquid flow 50. Note that when D1=D2, the cooling liquid discharged from the cooling liquid discharge portion 52 forms a cooling liquid flow along the inner surface 33 of the cylinder 32.

D1/D2 is preferably 2/3 or less, more preferably 1/2 or less, and most preferably 1/10 or more.

The cooling liquid flow 50 flowing out from the cooling liquid discharge portion 52 is an inverted conical flow that flows straight from the cooling liquid discharge portion 52 toward the axis O, but it may also be a spiral inverted conical flow.

The gas injection temperature, gas injection pressure, etc. may be set appropriately depending on the particle size of the target soft magnetic alloy powder. The gas injection temperature may be, for example, from room temperature to 200°C. The gas injection pressure may be, for example, from 0.5 MPa to 19 MPa.

The soft magnetic alloy powder according to this embodiment can be obtained by the above method. In order to suitably control the particle shape and particle size, it is preferable that the soft magnetic alloy powder is amorphous and does not contain crystals (nanocrystals).

It is preferable to perform a heat treatment on the amorphous soft magnetic alloy powder obtained by the gas atomization method. For example, by performing heat treatment at 350 to 575°C for 0.1 to 2 hours, it is possible to promote the diffusion of elements while preventing the individual powder particles from sintering together and becoming coarse, thereby allowing the powder to reach a thermodynamic equilibrium state in a short period of time and removing distortion and stress. Nanocrystals may precipitate at this point.

The soft magnetic alloy powder according to this embodiment can be used in any application requiring high relative magnetic permeability. For example, it can be used as a magnetic core. In particular, it can be used as a magnetic core for a power inductor. It can also be used in magnetic parts using the soft magnetic alloy powder, such as thin film inductors and magnetic heads. Furthermore, magnetic cores and magnetic parts using the soft magnetic alloy powder can be used in electronic devices.

The smaller the average particle size of the soft magnetic alloy powder, the more the loss at high frequencies can be reduced. For this reason, soft magnetic alloy powders with a small average particle size are particularly suitable for use in high frequency components. In addition, the larger the average particle size of the soft magnetic alloy powder, the easier it is to improve the magnetic permeability of the magnetic core. For this reason, soft magnetic alloy powders with a large average particle size are suitable for use in components that require high magnetic permeability.

The present invention will now be described in detail with reference to the following examples.

(Experimental Example 1)
Ingots of various materials were prepared and weighed so as to obtain master alloys having the compositions shown in Table 1. Then, the ingots were placed in a crucible disposed in a gas atomizing device.

Next, the master alloy was placed in the heat-resistant container 22 placed in the atomizing device 10. Next, after the inside of the cylinder 32 was evacuated, the heat-resistant container 22 was heated by high-frequency induction using a heating coil 24 provided outside the heat-resistant container 22, and the raw metals in the heat-resistant container 22 were melted and mixed to obtain molten metal (molten metal).

The obtained molten metal was sprayed into the housing 32 of the cooling section 30 at the atomizing temperature shown in Table 1, and argon gas was sprayed at a spray gas pressure of 7 MPa to form numerous droplets. The droplets collided with an inverted cone-shaped cooling water flow formed by cooling water supplied at a pump pressure of 10 MPa, turning into fine powder, which was then collected. However, for samples No. 3 and 4 in Table 1, the atomizing temperature was too low to spray the molten metal.

In the atomizing device 10 shown in Figures 8A and 8B, the inner diameter of the inner surface of the cylindrical body 32 was 300 mm, D1/D2 was 1/2, and the angle θ1 was 20 degrees.

Furthermore, in Experimental Example 1, heat treatment was performed at 475°C for 60 minutes. In addition, ICP analysis confirmed that the composition of the master alloy and the composition of the soft magnetic alloy powder were roughly the same.

It was confirmed whether each of the obtained soft magnetic alloy powders contained amorphous matter or nanocrystals. The presence or absence of peaks due to nanocrystals was confirmed using XRD. If it contained amorphous matter, it was recorded as amorphous in the microstructure column, and if it contained both amorphous and nanocrystals, it was recorded as amorphous + nanocrystals. The results are shown in Table 1.

The shape of the powder particles in each of the obtained soft magnetic alloy powders was evaluated. Specifically, the circularity of 20,000 particles was measured, and the average circularity on a number basis and the cumulative number ratio of particles with a circularity from the lowest to 0.50 were calculated. The results are shown in Table 1. Furthermore, for each example and comparative example, when the cumulative number ratio was 2.0% or less, there were few irregularly shaped particles, and when the cumulative number ratio was 1.5% or less, there were particularly few irregularly shaped particles. It was also confirmed that the average particle size (D50) on a volume basis for each example and comparative example was approximately 25 μm using a laser diffraction particle size distribution analyzer (HELOS&RODOS (Sympatec)).

DSC measurements were performed on each of the obtained soft magnetic alloy powders using STA449F3 (NETZSCH) to confirm the presence or absence of Tg. In addition, Tm and ΔT were measured. The results are shown in Table 1.

The coercive force Hc of each of the obtained soft magnetic alloy powders was measured using a K-HC1000 model (Tohoku Special Steel Co., Ltd.). The results are shown in Table 1. There is no particular limit to Hc. Hc may be 0.50 Oe or less. It is preferable that Hc is 0.20 Oe or less.

Next, a toroidal core was produced from each soft magnetic alloy powder. Specifically, each soft magnetic alloy powder was mixed with phenol resin as an insulating binder so that the amount of the phenol resin was 3% by mass of the total, and granulated to obtain a granulated powder of about 500 μm using a general planetary mixer as a mixer. Next, the obtained granulated powder was molded at a surface pressure of 4 ton/cm ² (392 MPa) to produce a toroidal-shaped molded body with an outer diameter of 13 mmφ, an inner diameter of 8 mmφ, and a height of 6 mm. The obtained molded body was hardened at 150° C. to produce a toroidal core.

Then, UEW wire was wound around the toroidal core, and μ (relative magnetic permeability) was measured at 100 kHz using a 4284A PRECISION LCR METER (Hewlett-Packard). The results are shown in Table 1. Note that a relative magnetic permeability μ of 30 or more was considered good.

As can be seen from Table 1, samples No. 1 to 4 and 1a, which are amorphous Fe-based soft magnetic alloys, had high Tm, and therefore the atomization temperature required for injection was high, at 1500°C or higher. In other words, the range of atomization temperatures at which soft magnetic alloy powder could be produced was narrow. Furthermore, the soft magnetic alloy powder obtained did not have a Tg. As a result, the soft magnetic alloy powder had a high coercive force, a low circularity, and many irregularly shaped particles. Furthermore, the relative permeability μ of the toroidal core produced using the soft magnetic alloy powder was low.

In contrast, samples No. 5 to 8 and 5a, which have compositions containing a large amount of Co, had low Tm, so the atomization temperature required for injection was low and they could be injected at an atomization temperature of 1,300°C. In other words, the range of atomization temperatures at which soft magnetic alloy powder could be produced was wide. Furthermore, the obtained soft magnetic alloy powder had a Tg. As a result, the soft magnetic alloy powder had a low coercive force, a high circularity, and few irregularly shaped particles. Furthermore, the relative permeability μ of the toroidal core produced using the soft magnetic alloy powder was high.

(Experimental Example 2)
In Experimental Example 2, soft magnetic alloy powders and toroidal cores of Samples No. 9 and 10 were produced under the same conditions as in Experimental Example 1, except that the pump pressure for supplying the cooling water was changed from that of Sample No. 1. The results are shown in Table 2.

As can be seen from Table 2, the average circularity of the particles of the soft magnetic alloy powder was improved by lowering the pump pressure. However, the change in the cumulative number ratio was small, and the change in the ratio of irregularly shaped particles was also small. Samples No. 9 and 10 were Fe-based soft magnetic alloys made of amorphous material, so they had high Tm. Furthermore, the soft magnetic alloy powder obtained did not have a Tg. As a result, the coercive force of the soft magnetic alloy powder was high and there were many irregularly shaped particles. Furthermore, the relative permeability μ of the toroidal core made using the soft magnetic alloy powder was low.

(Experimental Example 3)
In Experimental Example 3, soft magnetic alloy powders and toroidal cores of Samples Nos. 9 to 16 were produced under the same conditions as in Experimental Example 1, except that part of the Co in Sample No. 8 was replaced with Fe. The results are shown in Table 3.

In addition, soft magnetic alloy powders and toroidal cores of sample numbers 8a to 8e were produced under the same conditions as sample number 8, except for the change in composition. The results are shown in Table 3A.

From Table 3, samples No. 11 to 14, which have compositions within the specified range, have good particle shapes and good relative magnetic permeability μ of the toroidal core. Samples No. 11 to 14 show that as the Fe content increases, Tm increases, coercivity increases, and relative magnetic permeability μ decreases. Sample No. 16, which has α+β>0.500 and a small Co content, has a too high melting point of the soft magnetic alloy, and it was not possible to spray the molten metal at an atomization temperature of 1300°C. However, sample No. 11, which has a Co/Fe atomic ratio of 5 to 20, has a lower coercivity and a higher relative magnetic permeability μ than samples No. 8 and 12, which are outside the above range.

From Table 3A, each sample having a composition within a specified range, a Tg, and a Tm within a specified range required a low atomization temperature for injection, and could be injected at an atomization temperature of 1300°C. In other words, the range of atomization temperatures at which soft magnetic alloy powder could be produced was wide. Furthermore, the obtained soft magnetic alloy powder had a Tg. Therefore, the soft magnetic alloy powder had a low coercive force, a high circularity, and few irregularly shaped particles. Furthermore, the toroidal core produced using the soft magnetic alloy powder had a high relative permeability μ. Also, when the Co/B was higher than that of sample No. 8, the higher the Co/B, the higher the Tm, the smaller the average circularity, the higher the coercive force, and the lower the relative permeability μ.

(Experimental Example 4)
In Experimental Example 4, soft magnetic alloy powders and toroidal cores were produced under the same conditions as in Experimental Example 3 and Sample No. 11, except that the contents of the elements contained in the main components were changed. The results are shown in Tables 4 to 7.

Table 4 shows experimental examples in which the contents of Co, Fe and M (Nb) were changed. Samples No. 18 to 22, which had compositions within the specified ranges, had Tg and Tm within the specified ranges. The soft magnetic alloy powder had a high average circularity, few irregularly shaped particles and low coercive force. Furthermore, the relative permeability of the toroidal core was high.

In contrast, sample No. 17, which does not contain M (Nb), did not have a Tg. As a result, the average circularity of the soft magnetic alloy powder was low, there were many irregularly shaped particles, and the coercive force was high. Furthermore, the relative permeability of the toroidal core was high. Moreover, sample No. 23, which contained too much M, had a too low Tm. As a result, the average circularity of the soft magnetic alloy powder was low, there were many irregularly shaped particles, and the coercive force was high. Furthermore, the relative permeability of the toroidal core was high.

Table 5, Samples No. 24 to 27 are experimental examples in which the contents (b) of Co, Fe, and B were changed from Sample No. 11. Samples No. 25 and 26, which have compositions within a specified range, had Tg and Tm within a specified range. The average circularity of the soft magnetic alloy powder was high, there were few irregularly shaped particles, and the coercive force was low. Furthermore, the relative permeability of the toroidal core was high. In contrast, Sample No. 24, which has too little B content, had too high a melting point of the soft magnetic alloy, and it was not possible to spray the molten metal at the atomization temperature of 1300°C. Sample No. 27, which has too much B content, had too low a Tm. As a result, there were many irregularly shaped particles in the soft magnetic alloy powder, and the coercive force was high. Furthermore, the relative permeability of the toroidal core was low.

Table 5, Samples No. 28 to 34 are experimental examples in which the contents (c) of Co, Fe, and P were changed from Sample No. 11. Samples No. 28 to 33, which have compositions within a specified range, had Tg and Tm within a specified range. The average circularity of the soft magnetic alloy powder was high, there were few irregularly shaped particles, and the coercive force was low. Furthermore, the relative permeability of the toroidal core was high. In contrast, Sample No. 34, which contains too much P, had a too low Tm. As a result, the average circularity of the soft magnetic alloy powder was low, there were many irregularly shaped particles, and the coercive force was high. Furthermore, the relative permeability of the toroidal core was low.

Table 5, Samples No. 35 to 41 are experimental examples in which the contents (d) of Co, Fe, and Si were changed from Sample No. 11. Samples No. 35 to 40, which have compositions within a specified range, had Tg and Tm within a specified range. The soft magnetic alloy powder had a high average circularity, few irregularly shaped particles, and low coercive force. Furthermore, the relative permeability of the toroidal core was high. In contrast, Sample No. 41, which has too much Si content, had a too low Tm. As a result, the soft magnetic alloy powder had a low average circularity, many irregularly shaped particles, and high coercive force. Furthermore, the relative permeability of the toroidal core was low.

Table 6, Samples No. 42 to 46 are experimental examples in which the contents (e) of Co, Fe, and Cr were mainly changed from Sample No. 11. Samples No. 42 to 45, which have compositions within a specified range, had Tg and Tm within a specified range. The average circularity of the soft magnetic alloy powder was high, there were few irregularly shaped particles, and the coercive force was low. Furthermore, the relative permeability of the toroidal core was high. In contrast, Sample No. 46, which has too much Cr content, had many irregularly shaped particles in the soft magnetic alloy powder, and the coercive force was high. Furthermore, the relative permeability of the toroidal core was low.

Table 7, Samples No. 47 to 49 are experimental examples in which the contents (f) of Co, Fe, and S were mainly changed from Sample No. 11. Samples No. 47 and 48, which have compositions within a specified range, had Tg and Tm within a specified range. The average circularity of the soft magnetic alloy powder was high, the number of irregularly shaped particles was small, and the coercive force was low. Furthermore, the relative permeability of the toroidal core was high. Furthermore, since Samples No. 47 and 48 contain S, the proportion of irregularly shaped particles was lower than that of Sample No. 11. In contrast, Sample No. 49, which contains too much S, had a high coercive force of the soft magnetic alloy powder. Furthermore, the relative permeability of the toroidal core was low.

(Experimental Example 5)
In Experimental Example 5, soft magnetic alloy powder and toroidal cores were produced under the same conditions as in Experimental Example 1, except that part of Co in Sample No. 8 was replaced with X1 and/or X2. The results are shown in Tables 8 and 9.

Even when part of the Co was replaced with X1 and/or X2, each sample having a composition within the specified range had a Tg and a Tm within the specified range. The soft magnetic alloy powder had a high average circularity, few irregularly shaped particles, and a low coercive force. Furthermore, the relative permeability of the toroidal core was increased.

(Experimental Example 6)
In Experimental Example 6, soft magnetic alloy powder and toroidal cores were produced for Sample No. 8 under the same conditions as in Experimental Example 1, except that the type of M was changed. The results are shown in Table 10.

Even when the type of M was changed, each sample with a composition within the specified range had a Tg and a Tm within the specified range. The soft magnetic alloy powder had a high average circularity, few irregularly shaped particles, and low coercive force. Furthermore, the relative permeability of the toroidal core was high.

(Experimental Example 7)
In Experimental Example 7, soft magnetic alloy powder and toroidal cores were produced under the same conditions as in Experimental Example 1 except that the heat treatment conditions for Sample No. 8 were changed. Specifically, Sample No. 109 was not heat-treated. Sample No. 110 was heat-treated at 575°C. The results are shown in Table 11. Although not shown in Table 11, each sample had a Tg and a Tm within a predetermined range. The soft magnetic alloy powder had a high average circularity, few irregularly shaped particles, and low coercive force.

The soft magnetic alloy powder of sample No. 109 can be said to be the soft magnetic alloy powder before heat treatment in the manufacturing process of the soft magnetic alloy powder of sample No. 8. When comparing before and after heat treatment at 475°C, it is believed that the heat treatment did not produce crystals and was able to remove distortion and stress, resulting in an increase in the relative permeability μ.

The soft magnetic alloy powder of sample No. 110 was heat-treated at 575°C, which resulted in the formation of nanocrystals and a nanoheterostructure in which the nanocrystals are contained within the amorphous phase.

(Experimental Example 8)
In Experimental Example 8, soft magnetic alloy powders and toroidal cores of Samples No. 111 and 112 were produced under the same conditions as in Experimental Example 3, except that the average particle size on a volume basis was changed from that of Sample No. 11. Furthermore, soft magnetic alloy powders and toroidal cores of Samples No. 113 to 115 were produced under the same conditions as Samples No. 11, 111, and 112, except that the B content (b) was reduced and the atomization temperature was set to 1600° C. The results are shown in Table 12.

As shown in Table 12, the larger the average particle size, the higher the relative permeability of the toroidal core. In addition, each of samples No. 11, 111, and 112, which have compositions within the specified range, had a Tg and a Tm within the specified range. The soft magnetic alloy powder had a high average circularity, few irregularly shaped particles, and a low coercive force. Furthermore, the relative permeability of the toroidal core was high.

In contrast, samples No. 113 to 115, which had too small a B content (b), did not have a Tg and had too high a Tm. As a result, the soft magnetic alloy powder had a low average circularity, many irregularly shaped particles, and a high coercive force. Furthermore, the relative permeability of the toroidal core was low.

Reference Signs List 1, 2: Particle shape measurement result 10: Atomization device 20: Molten metal supply section 21: Molten metal 21a: Dropping molten metal 30: Cooling section 36: Cooling liquid introduction section 38a1: Outward convex section 50: Cooling liquid flow

Claims (8)

A soft magnetic alloy powder having a main component represented by the composition formula (Co _(1-( α ₊ β ₎₎ X1αX2β)(1-( _a + _{b +c+d+e+f)) MaBbPcSidCrESf ( atomic ratio} ),
X1 is one or more selected from the group consisting of Fe and Ni;
X2 is one or more selected from the group consisting of Al, Mn, Ag, Zn, Sn, As, Sb, Cu, Bi, N, O, C and rare earth elements;
M is one or more selected from the group consisting of Nb, Hf, Zr, Ta, Mo, W, Ti and V;
0<a≦0.140
0.160<b≦0.250
0.010≦c≦0.050
0≦d≦0.250
0≦e≦0.030
0≦f≦0.010
0.160<b+c+d+e+f≦0.430
0.500<1-(a+b+c+d+e+f)<0.840
α≧0
β≧0
0≦α+β ≦0.40
and
The average circularity of powder particles contained in the soft magnetic alloy powder is 0.93 or more, and a cumulative number ratio of the powder particles having a circularity of from 0.50 to 0.50 is 2.0% or less,
The soft magnetic alloy powder has a glass transition point Tg and a melting point Tm,
A soft magnetic alloy powder having a temperature of 900°C≦Tm≦1200°C. The soft magnetic alloy powder according to claim 1, wherein the average circularity of the powder particles contained in the soft magnetic alloy powder is 0.95 or more, and the cumulative percentage of the powder particles having a circularity of 0.50 from the lowest circularity is 1.5% or less. The soft magnetic alloy powder according to claim 1 or 2, in which the value obtained by dividing the Co content by the B content is greater than 2.000 and less than 5.000. The soft magnetic alloy powder according to any one of claims 1 to 3, which is amorphous. The soft magnetic alloy powder according to any one of claims 1 to 3, which has nanocrystals. A magnetic core containing the soft magnetic alloy powder according to any one of claims 1 to 5. A magnetic part containing the soft magnetic alloy powder according to any one of claims 1 to 5. An electronic device containing the soft magnetic alloy powder according to any one of claims 1 to 5.

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