JP2018101686A - Soft magnetic alloy powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soft magnetic alloy powder that is used for a magnetic core for a magnetic device and can obtain a high magnetic permeability.SOLUTION: A soft magnetic alloy powder includes at least two phases of a magnetic phase containing Fe and a stress relaxation phase having a Young's modulus of 70 GPa or less. The magnetic phase is bonded via the stress relaxation phase, mixed phase grains are formed, and preferably the thickness of the stress relaxation phase is 5 to 100 nm and the magnetic phase is a grain having a grain size of 100 μm or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a soft magnetic alloy powder, a green compact made using the soft magnetic alloy powder, a paste, a sheet, and a magnetic core of a magnetic device such as a choke coil, an inductor, a reactor, and a transformer formed using the same. is there.

Soft magnetic alloy powders are used as magnetic cores for a wide variety of magnetic devices because they can be easily molded into a desired shape by pressure molding or kneading with a resin. In addition, there is a feature that a magnetic core having a high volume resistance and a small eddy current loss can be produced by kneading with a high resistance component such as a resin to make a composite, which has contributed to an increase in efficiency of the magnetic device. In recent years, a magnetic powder having a low coercive force, a high resistivity, and a saturation magnetization has been reported in order to satisfy the demand for further reduction in loss in high frequency applications.

For example, Patent Document 1 contains B, Zr, Nb, Ta, Hf, Mo, Ti, and V, which have an amorphous forming effect, in addition to magnetic metal elements of Fe, Co, and Ni, and further has Cr, W that has a corrosion resistance effect. , Ru, Rh, Pd, Os, Ir, Pt, Al, Si, Ge, C, and P are disclosed. Further, in Patent Document 2, nanostructures including Fe, B, Si, S, C, P, Al, Ge, Ga, Be, Au, Cu, etc. and having a mixed phase structure of a microcrystalline phase having an crystal grain size of 60 nm or less and an amorphous phase. A technique for producing a magnetic device using a crystalline soft magnetic alloy powder is disclosed. As a method for increasing resistance, for example, Patent Document 3 discloses a technique of coating soft magnetic alloy powder with glass. Patent Document 4 also discloses a technique for improving mechanical workability by adding Sn, In, Zn to a soft magnetic alloy mainly composed of Fe.

JP 2002-184616 A JP 2008-294411 A JP 2002-50511 A JP 2009-299108 A

By the way, the amorphous phase portion of the soft magnetic alloy powder containing the amorphous phase has a mechanically hard property because it does not have a long-range order of crystals. Therefore, although distortion is relatively unlikely to occur with respect to the mechanical external force, stress that antagonizes the external force is stored inside the powder. Therefore, when the magnetic core is prepared by pressure molding, the stress generated during the pressure molding remains in the powder. Further, when the magnetic core is a composite of resin / solvent, stress is accumulated inside the powder in response to volume changes in the process such as curing of the kneaded resin and drying of the solvent.

It is known that the magnetic permeability of soft magnetic materials decreases depending on the product of internal stress and magnetostriction constant, and that the magnetic permeability of soft magnetic materials can be improved by relaxing internal stress. In order to produce a magnetic core having a high magnetic permeability, a soft magnetic alloy powder that hardly accumulates internal stress is required. Attempts have been made to mechanically soften the soft magnetic alloy powder by adding a metal element having a low Young's modulus such as Sn, In, Zn, etc., but the soft magnetism of the soft magnetic metal alloy powder having the amorphous structure as described above Since both properties and mechanically hard properties are attributed to the amorphous structure, a technology that achieves both high soft magnetic properties and mechanically soft physical properties that are difficult to accumulate stress has not yet been realized.

The problem to be solved by the present invention is how to reduce the internal stress and improve the magnetic permeability when producing a magnetic core using a soft magnetic alloy powder containing an amorphous phase.

In order to solve the above problems, the soft magnetic alloy powder of the present invention is composed of at least two kinds of phases, a magnetic phase and a stress relaxation phase, the magnetic phase is particles containing Fe, and the stress relaxation phase has a Young's modulus. Is 70 GPa or less, and a plurality of the magnetic phases are bound via the stress relaxation phase to form mixed phase grains. The magnetic phase preferably has a particle size of 100 μm or less, and the stress relaxation phase preferably has a thickness of 5 to 100 nm.

By using the soft magnetic alloy powder of the present invention, a magnetic core for a magnetic device having a high magnetic permeability can be obtained.

It is a figure of the soft magnetic alloy powder of this invention.

The soft magnetic alloy powder of the present invention is composed of at least two kinds of phases of a magnetic phase A and a stress relaxation phase B, the magnetic phase A contains Fe, the stress relaxation phase B has a Young's modulus of 70 GPa or less, The magnetic phase A is bound through the stress relaxation phase B, and mixed phase grains C are formed.

The premagnetic phase A will be described in more detail. As long as the magnetic phase A contains Fe, elements other than Fe may be contained, and elements other than Fe that are preferably contained include Si, B, P, C, Cr, Zr, Nb, Hf, Cu, Ag, etc. are mentioned. The fine structure of the magnetic phase A includes an amorphous or metallic glass portion, and may be a mixed phase of an amorphous or metallic glass portion and a crystalline portion. In this case, the crystal grain size of the crystal part is particularly preferably a fine crystal of 60 nm or less. The inclusion of Si, B, C, P in the magnetic phase A facilitates the formation of an amorphous state, and the inclusion of Zr, Hf, Nb facilitates miniaturization of the crystal portion, which makes the crystal magnetic anisotropic The coercive force derived from the nature becomes small, and a soft magnetic alloy powder with high magnetic permeability and low loss can be obtained. Further, the inclusion of Cu and Ag becomes a crystal nucleus of the crystal portion, and it becomes easy to form a fine crystal.

The particle size of the magnetic phase A is preferably 100 μm or less. When the particle size of the magnetic phase A exceeds 100 μm, the intragranular eddy current of the magnetic phase A increases, and the loss component derived from eddy current loss increases. Further, if the particle size is 100 μm or less, it is also preferable that the particle size distribution has a plurality of frequency maxima. The particle size distribution of the magnetic phase A is a distribution of the equivalent circle diameter of the projected area when the cut surface or fracture surface of the magnetic core prepared using the mixed phase particle C or the mixed phase particle C is observed with a microscope. The average value of the particle size distribution.

The stress relaxation phase B is made of a glass composition (hereinafter referred to as glass) containing a metal, alloy, metal oxide having a low Young's modulus, or a mixture thereof. Examples of metals and alloys having a low Young's modulus include In, Sn, Al, Bi, and alloys thereof. As the glass, for example, a composition having a Young's modulus of 70 GPa or less can be selected from silicate glass, borate glass, borosilicate glass, aluminosilicate glass, phosphate glass, tellurate, germanate and the like.

The method for producing the soft magnetic alloy powder shown in the present embodiment is not particularly limited. For example, the composition of the magnetic phase A, the microstructure, the composition of the raw material powder A1 having the particle diameter and the stress relaxation phase B After the raw material powder B1 having each of the above is prepared, the raw material powder A1 and the raw material powder B1 are mixed, and mixed phase treatment is performed by a mechanical mixed phase method such as a mechanical alloying method or a mechanofusion method, thereby generating mixed phase particles C. be able to. When the raw material powder B1 is a metal, the temperature during the mixed phase treatment is preferably equal to or higher than the melting point of the raw material powder B1, and when the raw material powder B1 is glass, the temperature is preferably equal to or higher than the glass transition point of the raw material powder B1. .

Although the method for producing the raw material powder A1 is not particularly limited, a spraying powder forming method such as atomization, a solid phase reduction method, a hydrothermal synthesis method, or the like can be used. Desired by pulverizing and classifying the prepared raw material powder as appropriate. The particle size can be adjusted.

The method for producing the raw material powder B1 is not particularly limited. However, when the raw material powder B1 is a metal, it can be produced using a spraying powder forming method such as atomization, a solid phase reduction method, a hydrothermal synthesis method, etc. When B1 is glass, it can be prepared by preparing a metal oxide powder in accordance with the composition of the raw material powder B1 and rapidly cooling after melting. The prepared raw material powder can be adjusted to a desired particle size by appropriately pulverizing and classifying.

Since the stress relaxation phase B has a low Young's modulus, the mixed phase grains C having a shape in which the magnetic phase A is bound via the stress relaxation phase B are formed into a desired shape to form a magnetic core. Even when an external force is applied, the stress relaxation phase B is distorted so that the stress is relaxed, and no internal stress remains in the magnetic phase A. Therefore, even when the magnetic phase A has a relatively large magnetostriction constant, magnetic anisotropy derived from magnetostriction does not appear, and a magnetic core having a high magnetic permeability can be obtained.

Although it is preferable from the viewpoint that the stress relaxation effect becomes larger as the thickness of the stress relaxation phase B increases, the nonmagnetic gap between the plurality of magnetic phases A adjacent to each other through the stress relaxation phase B increases. In addition, when the magnetic core is formed, the magnetic permeability is decreased and the saturation magnetic flux density is decreased. The thickness of the stress relaxation phase B in the present embodiment is preferably 5 to 100 nm.

The external force applied at the time of molding is not limited only to the pressure at the time of compression molding, but also due to volume changes that occur when the kneaded resin is cured or when organic solvents, moisture, etc. are dried. Since an external force is applied to the magnetic phase A, the effect of increasing the magnetic permeability can be obtained even when molding at a relatively low pressure by using the mixed phase grains C of the present invention.

The above embodiment will be described in more detail with reference to an example together with a comparative example.

(Examples 1 to 13, Comparative Example 1)
Fe, B, Cr, and Si were weighed in predetermined amounts, and these raw materials were dissolved in a high-frequency induction heating apparatus in a reduced pressure Ar atmosphere to produce an ingot. This ingot is melted by putting it in a molten crucible, and molten alloy is injected from the molten metal nozzle of the molten metal crucible, and an argon gas flow is injected from a separate gas sprayer to atomize the molten alloy. The molten metal was quenched to obtain a metal glass alloy powder. The obtained powder was classified into a desired particle size by a mesh permeation method, a centrifugal separation method, a sedimentation method, or the like, and then heat treated at a predetermined temperature to obtain a raw material powder A1 of magnetic phase A. Next, a predetermined amount of each of Al, In, Sn, and Bi was weighed and pulverized and classified by the same method as the raw material powder A1 to obtain a raw material powder B1 of the stress relaxation phase B. Raw material powder A1 and raw material powder B1 were loaded into a mechanical alloying device, heated to a predetermined temperature, and subjected to a phase mixing treatment for a predetermined time to obtain mixed phase particles C. The thickness of the stress relaxation phase B was changed by changing the average particle diameter of the raw material powder B1, the mixing ratio of the raw material powder A1 and the raw material powder B1, and the treatment temperature. Furthermore, the composition of the raw material powders A1 and B1 was changed by changing the charging ratio of each element at the time of preparing the raw material powders A1 and B1. The composition of the magnetic phase A and the stress relaxation phase B of the obtained mixed phase grain C, the particle diameter of the magnetic phase A, and the thickness of the stress relaxation phase B were observed by a particle cross section SEM and a particle cross section EDS. The obtained values are shown in Table 1. Furthermore, after adding a thermosetting epoxy resin, a curing initiator, and acetone to the obtained mixed phase particle C and kneading with a homogenizer, the mixture was heated at 50 ° C. for 3 hours to evaporate the acetone, and then crushed into granules. The obtained granule was molded into a toroidal shape having an inner diameter of 9 mm, an outer diameter of 11 mm, and a thickness of 3 to 4 mm, and then heated at 180 ° C. for 2 hours to cure the resin to obtain a toroidal core. The obtained toroidal core was wound with 30 Turn, the inductance was measured with an LCR meter, and the magnetic permeability was determined from the obtained inductance. Moreover, the core loss was measured with the AC BH analyzer.
(Comparative Examples 2 and 3)
The raw material powder A1 was prepared by the same method as in the above (Examples 1 to 13, Comparative Example 1), and the raw material powder A1 and B1 were not mixed and the raw material powder A1 alone was used (Examples 1 to 13). A toroidal core was prepared and evaluated in the same manner as in Comparative Example 1).
Table 1 shows the permeability values at 100 kHz and the core loss values at 3 MHz and 10 mT of the toroidal cores created in Examples 1 to 13 and Comparative Examples 1 to 3.

When Example 3 and Examples 9 to 13 and Comparative Examples 1 to 3 are compared, the magnetic permeability is improved by creating a magnetic core using the mixed phase grains C having the stress relaxation phase B having a Young's modulus of 70 GPa or less. It can be confirmed. Further, it can be confirmed from Examples 1 to 6 that a particularly remarkable effect of improving the magnetic permeability can be obtained by setting the thickness of the stress relaxation phase to 5 to 100 nm. Further, it can be confirmed from Examples 3, 7 and 8 that when the particle diameter of the magnetic phase A exceeds 100 μm, a high magnetic permeability can be obtained, but the loss is remarkably increased.

(Examples 14 to 24, Comparative Example 4)
Raw material powder A1 was prepared in the same manner as in Examples 1 to 13 and Comparative Example 1. A metal oxide powder was prepared according to the composition of the stress relaxation phase B, a glass powder was prepared by a melting method, and pulverized and classified to a desired particle size distribution to obtain a raw material powder B1. Thereafter, mixed powder C1 is produced by subjecting raw material powder A1 and raw material powder B1 to a mixed phase treatment in the same manner as in Examples 1 to 13 and Comparative Example 1, and a toroidal core is created and evaluated using mixed phase particles C. Went. Table 2 shows the initial permeability value at 100 kHz and the core loss value at 3 MHz and 10 mT of the toroidal cores produced in Examples 14 to 24 and Comparative Example 4.

When Examples 16 and 22 to 24 and Comparative Examples 2 to 4 are compared, the magnetic permeability is improved by forming the magnetic core using the mixed phase grains C having the stress relaxation phase B having a Young's modulus of 70 or less. I can confirm. Moreover, it can be confirmed from Examples 14 to 19 that a remarkable permeability improvement effect is obtained when the thickness of the stress relaxation phase is 5 to 100 nm. Furthermore, it can be confirmed from Examples 16, 20, and 21 that when the particle size of the magnetic phase A exceeds 100 μm, a high magnetic permeability can be obtained, but the loss is remarkably increased.

The present invention is effective as a magnetic core for inductors, reactors, transformers, choke coils and the like.

A Magnetic phase B Stress relaxation phase C Mixed phase grain

Claims (5)

The magnetic phase is composed of at least two kinds of phases of a magnetic phase and a stress relaxation phase, the magnetic phase is particles containing Fe, the stress relaxation phase has a Young's modulus of 70 GPa or less, and the magnetic phase is the stress relaxation phase. A soft magnetic alloy powder characterized in that mixed phase grains are formed through binding. The soft magnetic alloy powder according to claim 1, wherein the stress relaxation phase has a thickness of 5 to 100 nm. The soft magnetic alloy powder according to claim 1, wherein the magnetic phase is a particle having a particle diameter of 100 μm or less. The soft magnetic alloy powder according to any one of claims 1 to 3, wherein the stress relaxation phase is an alloy containing one or more selected from In, Sn, Al, and Bi. The soft magnetic alloy powder according to claim 1, wherein the stress relaxation phase is a glass composition containing a metal oxide.

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