Soft magnetic material and method for producing the same, and electric motor containing soft magnetic material

Patent metadata

Field	Value
Publication number	US-12129558-B2
Application number	US-201917414357-A
Country	US
Kind code	B2
Filing date	Sep 11, 2019
Priority date	Feb 13, 2019
Publication date	Oct 29, 2024
Grant date	Oct 29, 2024

Abstract

A soft magnetic material that is sheet-shaped or foil-shaped and has a high saturation magnetic flux density, contains iron, carbon, and nitrogen, and includes a martensite containing carbon and nitrogen, and γ-Fe, wherein the γ-Fe includes a nitrogen-containing phase. The soft magnetic material is produced by steps of heating an iron-based material that is sheet-shaped or foil-shaped, carburizing the iron-based material with a carburizing gas, dispersing a granular carbide in α-Fe in the iron-based material at a temperature equal to or lower than a eutectoid temperature, transforming the α-Fe into γ-Fe at a temperature higher than the eutectoid temperature, diffusing nitrogen into the γ-Fe using a nitrogen supply gas to form γ-Fe—N—C, and rapidly heating and then rapidly cooling the γ-Fe—N—C to transform the γ-Fe—N—C into a martensite. The result is a thermally stable soft magnetic material having a saturation magnetic flux density higher than that of pure iron.

First claim

The invention claimed is:

1. A soft magnetic material that is sheet-shaped or foil-shaped, the soft magnetic material comprising:
iron, carbon, and nitrogen having an average carbon concentration of 0.45 mass % or more and 1.12 mass % or less, and an average nitrogen concentration of 0.4 mass % or more and 1.2 mass % or less; and
a martensite containing carbon and nitrogen, and γ-Fe,
wherein the phase structure of the martensite is 80 vol. % or more,
wherein the γ-Fe includes a face-centered cubic crystal containing nitrogen, and
wherein the soft magnetic material has a saturation magnetic flux density of 2.3 T or more and a thickness of 0.01 mm or more and 1.00 mm or less.

2. The soft magnetic material according to claim 1 , wherein a volume fraction of the face-centered cubic crystal is 1 vol % or more and lower than a volume fraction of the martensite.

3. The soft magnetic material according to claim 2 , wherein the volume fraction of the face-centered cubic crystal is 1 vol % or more and 20 vol % or less.

4. The soft magnetic material according to claim 1 , wherein the martensite includes a body-centered cubic crystal and a body-centered tetragonal crystal.

5. The soft magnetic material according to claim 1 , further comprising vanadium or niobium.

6. The soft magnetic material according to claim 1 further comprising a Fe4N phase having a face-centered cubic crystal.

7. The soft magnetic material according to claim 1 , wherein the martensite is from Fe 3 C dispersed in γ-Fe—N in which the Fe 3 C is decomposed into the γ-Fe.

8. An electric motor comprising:
a core;
a coil; and
a rotor,
wherein the core contains the soft magnetic material according to claim 1 .

9. The electric motor according to claim 8 , wherein the core is a laminate of the soft magnetic material.

10. A method for producing the soft magnetic material according to claim 1 , the method comprising:
heating an iron-based material that is sheet-shaped or foil-shaped;
carburizing the iron-based material with a carburizing gas;
dispersing a granular carbide in α-Fe in the iron-based material at a temperature equal to or lower than a eutectoid temperature;
transforming the α-Fe into γ-Fe at a temperature higher than the eutectoid temperature;
diffusing nitrogen into the γ-Fe using a nitrogen supply gas to form γ-Fe—N—C; and
rapidly heating and then rapidly cooling the γ-Fe—N—C to transform the Y—Fe—N—C into a martensite.

11. The production method according to claim 10 , wherein the iron-based material has a thickness of 0.01 mm or more and 1.00 mm or less.

12. The production method according to claim 10 , wherein the iron-based material is pure iron or a low-carbon low-alloy steel.

13. The production method according to claim 10 , wherein the carburizing gas is acetylene.

14. The production method according to claim 10 , wherein the nitrogen supply gas is ammonia.

15. The production method according to claim 10 , wherein the rapid cooling is performed using liquid nitrogen.

16. The production method according to claim 10 , wherein the soft magnetic material including the martensite formed therein has an average carbon concentration of 0.45 mass % or more and 1.12 mass % or less, and an average nitrogen concentration of 0.4 mass % or more and 1.2 mass % or less.

17. The production method according to claim 10 , wherein the iron-based material contains vanadium or niobium.

Assignees

• Hitachi Ltd

Inventors

• Komuro Matahiro
• Satsu Yuichi
• Hatou Hisamitsu
• Park Seunghwan

Classifications

• H02K1/02

  characterised by the magnetic material · CPC title

• H01F1/147

  Alloys characterised by their composition {(treatment thereof for enhancing their electromagnetic properties C21D8/12)} · CPC title

• C22C2202/02

  Magnetic · CPC title

• C22C38/12

  containing tungsten, tantalum, molybdenum, vanadium, or niobium · CPC title

• C22C38/001

  containing N · CPC title