Iron-based soft magnetic powder and production method thereof

Patent metadata

Field	Value
Publication number	US-9589712-B2
Application number	US-201213709598-A
Country	US
Kind code	B2
Filing date	Dec 10, 2012
Priority date	Jan 12, 2012
Publication date	Mar 7, 2017
Grant date	Mar 7, 2017

Abstract

Disclosed is an iron-based soft magnetic powder obtained by preparing an iron-oxide-based soft magnetic powder through water atomization, and thermally reducing the iron-oxide-based soft magnetic powder. The iron-based soft magnetic powder has an average particle size of 100 μm or more and has an interface density of more than 0 μm −1 and less than or equal to 2.6×10 −2 μm −1 , where the interface density is determined from a cross-sectional area (μm 2 ) and a cross-sectional circumference (μm) of the iron-based soft magnetic powder. The iron-based soft magnetic powder obtained by preparing an iron-oxide-based soft magnetic powder through water atomization and thermally reducing the iron-oxide-based soft magnetic powder, when used for the production of a dust core, can give a dust core having a low coercive force. Also disclosed is a duct core having a low coercive force and exhibiting superior magnetic properties.

First claim

What is claimed is:

1. A method for producing an iron-based soft magnetic powder for a dust core, the method comprising:
preparing an iron-oxide-based soft magnetic powder through water atomization,
controlling a particle size of the iron-oxide-based soft magnetic powder by sieve classification so as to have a mass-cumulative particle size D 10 of from 120 μm to 170 μm and by having an interface density of the iron-based soft magnetic powder of more than 0 μm −1 and less than or equal to 2.1×10 −2 μm −1 , thereby reducing a coercive force of the iron-oxide-based soft magnetic powder; and
thermally reducing the size-controlled iron-oxide-based soft magnetic powder at 900° C. or higher, thereby obtaining the iron-based soft magnetic powder,
wherein the interface density is determined from a cross-sectional area (μm 2 ) and a cross-sectional circumference (μm) of the iron-based soft magnetic powder according to following Expression (1):
Interface density=Σ(cross-sectional circumferences of iron-based soft magnetic powder particles)/2/Σ/(cross-sectional areas of iron-based soft magnetic powder particles)  (1).

2. The method of claim 1 , further comprising controlling a particle size of the iron-based soft magnetic powder obtained from the thermal reduction, thereby obtaining an average particle size of 100 μm or more.

3. A method for producing a dust core, the method comprising:
compacting an iron-based soft magnetic powder produced by the method of claim 1 to give a powder compact; and
thermally treating the powder compact.

4. The method of claim 1 , comprising controlling the particle size by sieve classification and removing powder particles of 100 μm or less.

5. The method of claim 1 , comprising controlling the particle size by sieve classification and removing powder particles of 150 μm or less.

Assignees

• Kobe Steel Ltd

Inventors

• Miyamura Takeo
• Mitani Hiroyuki
• Hojo Hirofumi

Classifications

• H01F1/344 Primary

  Ferrites, e.g. having a cubic spinel structure (X2+O)(Y23+O3), e.g. magnetite Fe3O4 · CPC title

• H01F41/0246

  Manufacturing of magnetic circuits by moulding or by pressing powder (magnetic cores made by moulding or by pressing powder H01F27/255; soft magnetic particles H01F1/20, H01F1/36) · CPC title

• H01F41/02

  for manufacturing cores, coils, or magnets (H01F41/14 takes precedence; for dynamo-electric machines H02K15/00) · CPC title

• Y10T428/12181

  Composite powder [e.g., coated, etc.] · 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