Powder for dust cores, method for producing same, dust core and method for producing dust core

Patent metadata

Field	Value
Publication number	US-10832840-B2
Application number	US-201616064662-A
Country	US
Kind code	B2
Filing date	Dec 12, 2016
Priority date	Dec 24, 2015
Publication date	Nov 10, 2020
Grant date	Nov 10, 2020

Abstract

A powder for dust cores includes an aggregate of soft magnetic particles, each of which includes a soft magnetic metal particle, and a ferrite film that covers a surface of the soft magnetic metal particle and includes ferrite crystal grains having a spinel structure. A diffraction peak derived from the ferrite crystal grains exists in a powder X-ray diffraction pattern. By a method for producing a powder for dust cores, a raw material powder that includes an aggregate of soft magnetic metal particles is prepared. Furthermore, many ferrite fine particles are formed on a surface of each of the soft magnetic metal particles of the raw material powder. Additionally, the ferrite fine particles are coarsely crystallized through heat treatment to form a ferrite film, which includes ferrite crystal grains having a spinel structure, on the surface of the each of the soft magnetic metal particles.

First claim

The invention claimed is:

1. A powder for dust cores, comprising an aggregate of soft magnetic particles, each of which includes:
a soft magnetic metal particle; and
a ferrite film that covers a surface of the soft magnetic metal particle and includes ferrite crystal grains having a spinel structure,
wherein
a diffraction peak derived from the ferrite crystal grains exists in a powder X-ray diffraction pattern, the diffraction peak having a half-value width of 0.5° or less, and
the ferrite film includes a part where an interface between the ferrite crystal grains has a straight-line shape in a sectional view of the ferrite film.

2. The powder for dust cores according to claim 1 , wherein a size of each of the ferrite crystal grains is 10 nm or larger.

3. The powder for dust cores according to claim 1 , wherein a chemical composition of the ferrite film is M x Fe 2 O 4 , where:
M is at least one metal element selected from a group consisting of Fe, Cu, Mg, Ni, Zn, and Mn; and
X satisfies an expression 0<X≤1.

4. The powder for dust cores according to claim 3 , wherein M, which is the at least one metal element, includes Mn and Zn, or Ni and Zn.

5. The powder for dust cores according to claim 1 , wherein a thickness of the ferrite film is in a range of 20 to 600 nm.

6. A dust core that is a powder compact of the powder for dust cores recited in claim 1 , and that has its strain removed.

7. The dust core according to claim 6 , wherein a diffraction peak derived from FeO does not exist in the powder X-ray diffraction pattern.

8. A method for producing a dust core, comprising:
a powder compacting process of compacting the powder for dust cores recited in claim 1 to obtain a powder compact;
an annealing process of annealing the obtained powder compact; and
a transformation heat treatment process of re-ferritizing FeO, which is produced partially in the ferrite film included in the annealed powder compact, through heat treatment.

9. The method for producing a dust core according to claim 8 , wherein a heat treatment temperature in the transformation heat treatment process is 560° C. or lower.

10. The method for producing a dust core according to claim 8 , wherein an atmosphere in the transformation heat treatment process is a water vapor atmosphere or an inert gas atmosphere.

11. A method for producing a powder for dust cores, comprising:
preparing a raw material powder that includes an aggregate of soft magnetic metal particles;
forming many ferrite fine particles on a surface of each of the soft magnetic metal particles of the raw material powder by a spray method; and
coarsely crystallizing the ferrite fine particles through heat treatment to form a ferrite film, which includes ferrite crystal grains having a spinel structure, on the surface of the each of the soft magnetic metal particles,
wherein the heat treatment comprises heating the ferrite fine particles to a temperature in a range of 400 to 900° C.

12. The method for producing a powder for dust cores according to claim 11 , wherein an atmosphere during the heat treatment is an inert gas atmosphere or a vacuum atmosphere.

13. A dust core comprising:
a soft magnetic metal particle; and
a ferrite film that covers a surface of the soft magnetic metal particle and includes ferrite crystal grains having a spinel structure,
wherein
a diffraction peak derived from the ferrite crystal grains exists in a powder X-ray diffraction pattern,
the ferrite film includes a part where an interface between the ferrite crystal grains has a straight-line shape in a sectional view of the ferrite film, and
strain of the dust core has been removed.

Assignees

• Denso Corp

Inventors

• Matsubara Ken
• Hwang Jung Hwan
• Utsuno Seishi

Classifications

• B22F1/148

  Agglomerating · CPC title

• B22F1/16

  Metallic particles coated with a non-metal (coated with lubricating or binding agents or with organic material B22F1/10) · CPC title

• B22F1/05

  Metallic powder characterised by the size or surface area of the particles · CPC title

• C01G49/0018 Primary

  Mixed oxides or hydroxides, (C01G49/0009 takes precedence) · CPC title

• H01F3/08

  made from powder (powder coatings on sheets H01F3/02; on strips or ribbons H01F3/04; on wires H01F3/06) · CPC title