MAGNETIC POWDER, SOFT MAGNETIC COMPOSITE, AND METHOD OF FORMING SAME

• US 20080008897A1
• Filed: 07/06/2007
• Published: 01/10/2008
• Est. Priority Date: 07/06/2006
• Status: Abandoned Application

• Current Assignee: Matahiro Komuro, Takao Imagawa, Yuichi Satsu
• Original Assignee: Matahiro Komuro, Takao Imagawa, Yuichi Satsu
• Inventors: Komuro, Matahiro, Satsu, Yuichi, IMAGAWA, Takao
• Application Number:
  US11/774,238
• Publication Number:
  US 20080008897A1
• Time in Patent Office: Days
• US Class Current: 428/546
• CPC Class Codes: B22F 1/16 Metallic particles coated with a non-metal coated with lubricating or binding agents or with organic material B22F1/10
• CPC Class Codes: B22F 2998/10 Processes characterised by the sequence of their steps
• CPC Class Codes: B22F 9/04 starting from solid material, e.g. by crushing, grinding or milling C22C1/1084 takes precedence; crushing, grinding or milling, in general, see the relevant subclasses, e.g. B02C
• CPC Class Codes: B22F 9/082 atomising using a fluid using centrifugal force B22F9/10
• CPC Class Codes: B22F 9/24 starting from liquid metal compounds, e.g. solutions
• CPC Class Codes: H01F 1/24 the particles being insulated
• CPC Class Codes: H01F 41/0246 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 Class Codes: Y10T 428/12014 having metal particles
• CPC Class Codes: Y10T 428/12181 Composite powder [e.g., coated, etc.]

Abstract

A magnetic powder according to the present invention comprises powder made of the iron element as a main component, and an insulator covering the surface of the powder. The powder has a spherical shape or a smoothed surface. The insulator comprises rare earth fluorides, alkaline metal fluorides, or alkaline earth metal fluorides. A soft magnetic composite formed by using this magnetic powder can suppress its eddy current loss in a wide frequency band and can also suppress its hysteresis loss due to compressed residual distortion in soft magnetic powder.

Claims

1. A magnetic powder, comprising:

powder made of the iron element as a main component, and an insulator on a surface of the powder, wherein;

the powder has a spherical shape or a smoothed surface; and

the insulator comprises rare earth fluorides, alkaline metal fluorides, or alkaline earth metal fluorides.

2. A magnetic powder according to claim 1, wherein:

the powder is obtained by milling gas atomized powder, reduced powder, or aqueous atomized powder.

3. A magnetic powder according to claim 1, wherein:

an average particle diameter of the powder is 50 to 200 μ

m.

4. A magnetic powder according to claim 3, wherein:

an average thickness of the insulator is 20 nm or more but less than 400 nm.

5. A soft magnetic composite formed by compression-molding magnetic powder the main component of which is the iron element, wherein:

an insulating layer comprising rare earth fluorides, alkaline metal fluorides, or alkaline earth metal fluorides, and having a uniform thickness, is formed along grain boundaries of the compressed particles in the soft magnetic composite, in such a way that each compressed particle is covered with the insulating layer.

6. A soft magnetic composite according to claim 5, wherein:

among each peripheral line of the compressed powder particles on a cross section of the molded soft magnetic composite, defining a peripheral line having an amplitude of 3% or more to the average particle diameter of the compressed powder particles as a waviness curve;

when arbitrary segments circumscribing each waviness curve at two contacts on the waviness curve are drawn, the ratio of compressed powder particles in which the segments cross is 20% or less of the all compressed powder particles.

7. A soft magnetic composite according to claim 5, wherein:

an average particle diameter of the compressed particles in the soft magnetic composite is 50 to 200 μ

m.

8. A soft magnetic composite according to claim 5, wherein:

an average thickness of the insulating layer is 40 nm or more but less than 800 nm.

9. A soft magnetic composite according to claim 7, wherein:

the density of the soft magnetic composite is 7.4 g/cm³ or more and 7.8 g/cm³ or less.

10. A motor, wherein:

the soft magnetic composite of claim 7 is used as the material of a core.

12. A method of forming a soft magnetic composite comprising compression-molding magnetic powder, wherein:

the magnetic powder is made of the iron element as a main component, and an insulator on a surface of the magnetic powder is formed;

wherein the magnetic powder has a spherical shape or a smoothed surface; and

the insulator comprises rare earth fluorides, alkaline metal fluorides, or alkaline earth metal fluorides;

wherein the magnetic powder is compression-molded so that the density of the soft magnetic composite becomes 7.4 g/cm³ or more and 7.8 g/cm³ or less.

11. An electric car, wherein:

the motor of claim 12 is used as a driving motor.

13. A method of forming a soft magnetic composite according to claim 12, wherein:

the compression-molded soft magnetic composite is further heated at temperatures of 600 to 700°

C.