US-12620512-B2 - Soft magnetic powder and magnetic core

Abstract

A soft magnetic powder includes Fe and Co. The total content of Fe and Co with respect to the soft magnetic powder overall is 90 mass % or greater. The Fe content with respect to the total content of Fe and Co is 30-95 mass %. The average particle diameter of the soft magnetic powder is 0.10-5.0 μm. The amount of oxygen on the surface of the soft magnetic powder is 0.010 g/m 2 or less. The true density of the soft magnetic powder with respect to the theoretical density of the soft magnetic powder is 90-99%.

Inventors

• Nobuhiro Okuda
• Hiroyuki Matsumoto
• Kazuhiro YOSHIDOME

Assignees

• TDK CORPORATION

Dates

Publication Date

20260505

Application Date

20220225

Priority Date

20210329

Claims (5)

1. 1 . A soft magnetic powder comprising Fe and Co, wherein Fe and Co altogether constitute 90 mass % or more of the soft magnetic powder; Fe constitutes 30 mass % or more and 95 mass % or less of Fe and Co altogether; the soft magnetic powder has an average particle size of 0.10 μm or more and 5.0 μm or less; the soft magnetic powder has an oxygen content of 0.010 g/m 2 or less at a surface of the soft magnetic powder; and a ratio of a true density of the soft magnetic powder to a theoretical density of the soft magnetic powder is 90% or more and 99% or less.
2. 2 . The soft magnetic powder according to claim 1 further comprising a subcomponent, wherein the subcomponent constitutes 5 mass % or less of the soft magnetic powder.
3. 3 . The soft magnetic powder according to claim 2 , wherein the subcomponent comprises at least one selected from the group consisting of B, Si, P, Cu, V, Ti, Zr, Hf, Nb, Ta, Mo, W, Cr, Ni, Al, Mn, Ag, Zn, S, Sn, As, Sb, Bi, N, O, and rare-earth elements.
4. 4 . The soft magnetic powder according to claim 1 , wherein the soft magnetic powder has an average particle size of 0.1 μm or more and 1.0 μm or less.
5. 5 . A magnetic core comprising the soft magnetic powder according to claim 1 .

Description

TECHNICAL FIELD The present invention relates to a soft magnetic powder and a magnetic core. BACKGROUND Patent Document 1 discloses an invention related to an Fe—Co alloy powder or the like having an average particle size of 0.25 to 0.80 μm. The Fe—Co alloy powder can achieve a high μ′ at a high frequency band and is highly resistant to heat. PRIOR ARTS Patent Document Patent Document 1: WO 2019-142610 SUMMARY OF INVENTION Problem to be Solved by Invention It is an object of the present invention to provide a soft magnetic powder used for manufacture of a magnetic core having a high relative permeability and high DC superimposition characteristics. Means for Solving the Problem To achieve the above object, a soft magnetic powder of the present invention is a soft magnetic powder comprising Fe and Co, whereinFe and Co altogether constitute 90 mass % or more of the soft magnetic powder; Fe constitutes 30 mass % or more and 95 mass % or less of Fe and Co altogether;the soft magnetic powder has an average particle size of 0.10 μm or more and 5.0 μm or less;the soft magnetic powder has an oxygen content of 0.010 g/m2 or less at a surface of the soft magnetic powder; anda ratio of a true density of the soft magnetic powder to a theoretical density of the soft magnetic powder is 90% or more and 99% or less. The soft magnetic powder may further comprise a subcomponent, and the subcomponent may constitute 5 mass % or less of the soft magnetic powder. The subcomponent may comprise at least one selected from the group consisting of B, Si, P, Cu, V, Ti, Zr, Hf, Nb, Ta, Mo, W, Cr, Ni, Al, Mn, Ag, Zn, S, Sn, As, Sb, Bi, N, O, and rare-earth elements. The soft magnetic powder may have an average particle size of 0.1 μm or more and 1.0 μm or less. A magnetic core of the present invention comprises the above soft magnetic powder. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an example chart generated in an X-ray crystal structure analysis. FIG. 2 is a plurality of example patterns obtained by profile fitting of the chart of FIG. 1. DETAILED DESCRIPTION OF INVENTION Hereinafter, the present invention will be described based on an embodiment. (Magnetic Core) A magnetic core according to the present embodiment includes a soft magnetic powder according to the present embodiment described later. More specifically, the magnetic core according to the present embodiment is produced using a mixture of a large-size powder and a small-size powder. The large-size powder is a soft magnetic powder having an average particle size exceeding 5.0 μm. The small-size powder is the soft magnetic powder according to the present embodiment described later having an average particle size of 5.0 μm or less. Soft magnetic particles included in the large-size powder and/or the small-size powder may be insulation coated. When the magnetic core is produced using the mixture of the large-size powder and the small-size powder, the magnetic core readily has an improved packing density and an improved relative permeability, compared to when the magnetic core is produced using only the large-size powder or only the small-size powder. This is because voids between the soft magnetic particles of the large-size powder can be filled with the soft magnetic particles of the small-size powder. The large-size powder may have any composition and any microstructure. The composition and the microstructure may be appropriately selected in accordance with the purpose or the like of the magnetic core. The microstructure of the large-size powder can be checked with XRD. The microstructure of the large-size powder can also be checked with a TEM. When the large-size powder has an amorphous structure and when the large-size powder has a nanocrystalline structure, the magnetic core readily has an improved relative permeability and a decreased core loss. An amorphous structure is a structure including only an amorphous solid or a hetero-amorphous structure. A hetero-amorphous structure is a structure in which initial fine crystals are present in an amorphous solid. The initial fine crystals may have any average crystal size. The average crystal size may be 0.3 nm or more and 10 nm or less. An amorphous structure has an amorphous ratio of 85% or more, which can be confirmed with XRD. Whether the large-size powder has an amorphous structure or a hetero-amorphous structure can be confirmed with a TEM. A nanocrystalline structure is a structure mainly including nanocrystals. In the crystalline (nanocrystalline) structure, the amorphous ratio, which can be confirmed with XRD, is less than 85%. Nanocrystals included in the nanocrystalline structure have an average crystal size of 5 nm or more and 100 nm or less. In the present embodiment, a soft magnetic metal powder having an amorphous ratio X of 85% or more is deemed to have an amorphous structure or a hetero-amorphous structure, and a soft magnetic metal powder having an amorphous ratio X of less than 85% is deemed to have a cryst