Rare earth magnet powder and method of producing the same

• US 20070079904A1
• Filed: 05/13/2004
• Published: 04/12/2007
• Est. Priority Date: 08/27/2003
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Mori, Katsuhiko, Kano, Makoto, Tayu, Tetsurou, Nakayama, Ryoji, Kawashita, Yoshio, Ono, Hideaki, Shimada, Munekatsu
• Granted Patent: US 7,632,360 B2
• Time in Patent Office: Days
• US Class Current: 148/105
• CPC Class Codes: C22C 1/0441 Alloys based on intermetallic compounds of the type rare earth - Co, Ni
• CPC Class Codes: C22C 38/005 containing rare earths, i.e. Sc, Y, Lanthanides
• CPC Class Codes: C22C 38/10 containing cobalt
• CPC Class Codes: H01F 1/0572 with a protective layer
• CPC Class Codes: H01F 41/0253 for manufacturing permanent magnets
• CPC Class Codes: Y10T 428/2991 Coated

Abstract

A rare earth magnet powder has a chemical composition which includes R: 5 to 20% (wherein, R represents one or two or more rare earth elements being inclusive of Y but exclusive of Dy and Tb), one or two of Dy and Tb: 0.01 to 10%, and B: 3 to 20%, with the balance comprising Fe and inevitable impurities; and an average particle diameter of 10 to 1,000 μm, wherein 70% or more of the entire surface of the rare earth magnet powder is covered with a layer being rich in the content of one or two of Dy and Tb and having a thickness of 0.05 to 50 μm.

Claims

1. A rare earth magnet powder comprising:

a chemical composition comprising R;

5 to 20 atom % (wherein R represents one, or two or more rare earth elements being inclusive of Y but exclusive of Dy and Tb), one or both of Dy and Tb;

0.01 to 10 atom %, and B;

3 to 20 atom %, with the balance comprising Fe and inevitable impurities, an average particle diameter being 10 to 1,000 μ

m, wherein

70% or more of the entire surface of the rare earth magnet powder is covered with a Dy—

Tb rich layer being rich in content of the one or both of Dy and Tb and having a thickness of 0.05 to 50 μ

m, and

a concentration of the one or both of Dy and Tb in the Dy—

Tb rich layer is such that the maximum detected intensity of the one or both of Dy and Tb, as measured by wavelength dispersive X-ray spectroscopy, is 1.2 to 5 times the average detected intensity in the central portion being present in the range of ⅓

of the particle diameter of a particle of the rare earth magnet powder.

5. A rare earth magnet powder which is excellent in magnetic anisotropy and thermal stability according to any one of claims 1 to 4, further comprising:

a recrystallization texture in which recrystallized grains, whose main phase is a R₂Fe₁₄B intermetallic compound phase that is substantially a tetragonal structure, are adjacent to each other, wherein

the recrystallization texture comprises a basic texture of a magnetically anisotropic HDDR magnet powder in which the recrystallized grains, whose ratio (b/a) of a longest particle diameter (b) to a shortest particle diameter (a) is less than 2, exists at 50 vol % or more of all the recrystallized grains and an average recrystallized grain diameter of the recrystallized grains is 0.05 to 5 μ

m.

6. A rare earth magnet produced by binding a rare earth magnet powder which is excellent in magnetic anisotropy and thermal stability according to any one of claims 1 to 4 with an organic binder or a metal binder.

7. A rare earth magnet produced by processing a rare earth magnet powder which is excellent in magnetic anisotropy and thermal stability according to any one of claims 1 to 4 with hot pressing or hot isostatic pressing.

2. A rare earth magnet powder comprising:

a chemical composition comprising R;

5 to 20 atm % (wherein R represents one, or two or more rare earth elements being inclusive of Y but exclusive of Dy and Tb), one or both of Dy and Tb;

0.01 to 10 atm %, B;

3 to 20 atm %, and M;

0.001 to 5 atm % (wherein M represents one, or two or more from among Ga, Zr, Nb, Mo, Hf, Ta, W, Ni, Al, Ti, V, Cu, Cr, Ge, C, and Si), with the balance comprising Fe and inevitable impurities, an average particle diameter being 10 to 1,000 μ

m, wherein

70% or more of the entire surface of the rare earth magnet powder is covered with a Dy—

Tb rich layer being rich in content of the one or both of Dy and Tb and having a thickness of 0.05 to 50 μ

m, and

a concentration of the one or both of Dy and Tb in the Dy—

Tb rich layer is such that the maximum detected intensity of the one or both of Dy and Tb, as measured by wavelength dispersive X-ray spectroscopy, is 1.2 to 5 times the average detected intensity in the central portion being present in the range of ⅓

of the particle diameter of a particle of the rare earth magnet powder.

3. A rare earth magnet powder comprising:

a chemical composition comprising R;

5 to 20 atm % (wherein R represents one, or two or more rare earth elements being inclusive of Y but exclusive of Dy and Tb), Co;

0.1 to 50 atm %, one or both of Dy and Tb;

0.01 to 10 atm %, and B;

3 to 20 atm %, with the balance comprising Fe and inevitable impurities, an average particle diameter being 10 to 1,000 μ

m, wherein

70% or more of the entire surface of the rare earth magnet powder is covered with a Dy—

Tb rich layer being rich in content of the one or both of Dy and Tb and having a thickness of 0.05 to 50 μ

m, and

a concentration of the one or both of Dy and Tb in the Dy—

Tb rich layer is such that the maximum detected intensity of the one or both of Dy and Tb, as measured by wavelength dispersive X-ray spectroscopy, is 1.2 to 5 times the average detected intensity in the central portion being present in the range of ⅓

of the particle diameter of a particle of the rare earth magnet powder.

4. A rare earth magnet powder comprising:

a chemical composition comprising R;

5 to 20 atm % (wherein M represents one, or two or more from among Ga, Zr, Nb, Mo, Hf, Ta, W, Ni, Al, Ti, V, Cu, Cr, Ge, C, and Si), one or both of Dy and Tb;

0.01 to 10 atm %, Co;

0.1 to 50 atm %, B;

3 to 20 atm %, and M;

0.001 to 5 atm % (wherein M represents one, or two or more from among Ga, Zr, Nb, Mo, Hf, Ta, W, Ni, Al, Ti, V, Cu, Cr, Ge, C, and Si), with the balance comprising Fe and inevitable impurities, an average particle diameter being 10 to 1,000 μ

m, wherein

70% or more of the entire surface of the rare earth magnet powder is covered with a Dy—

Tb rich layer being rich in content of the one or both of Dy and Tb and having a thickness of 0.05 to 50 μ

m, and

a concentration of the one or both of Dy and Tb in the Dy—

Tb rich layer is such that the maximum detected intensity of the one or both of Dy and Tb, as measured by wavelength dispersive X-ray spectroscopy, is 1.2 to 5 times the average detected intensity in the central portion being present in the range of ⅓

of the particle diameter of a particle of the rare earth magnet powder.

8. A method of producing a rare earth magnet powder, comprising:

milling a rare earth magnet alloy raw material in an inert gas atmosphere to an average powder particle diameter of 10 to 1,000 μ

m so as to produce a rare earth magnet alloy raw material powder;

adding to the rare earth magnet alloy raw material powder a Dy hydride powder, a Tb hydride powder, or a Dy—

Tb binary alloy hydride powder, each of which has an average powder particle diameter of 0.1 to 50 μ

m, at 0.01 to 5 mol %, followed by mixing so as to produce a mixed powder;

carrying out hydrogen absorption by heating, or heating and holding the mixed powder from room temperature to a temperature below 500°

C. in a hydrogen gas atmosphere with a pressure of 10 to 1,000 kPa so as to induce the mixed powder to absorb hydrogen;

carrying out hydrogen absorption-decomposition by heating and holding the mixed powder at a temperature in a range of 500 to 1,000°

C. in a hydrogen gas atmosphere with a pressure of 10 to 1,000 kPa so as to induce the mixed powder to absorb hydrogen and to be decomposed; and

then

carrying out hydrogen desorption by holding the mixed powder at a temperature in a range of 500 to 1,000°

C. in a vacuum atmosphere with an ultimate pressure of 0.13 kPa or below so as to forcibly release hydrogen and promote a phase transformation, followed by cooling and pulverizing.

9. A method of producing a rare earth magnet powder, comprising:

milling a rare earth magnet alloy raw material in an inert gas atmosphere to an average powder particle diameter of 10 to 1,000 μ

m so as to produce a rare earth magnet alloy raw material powder;

adding to the rare-earth magnet alloy raw material powder a Dy hydride powder, a Tb hydride powder, or a Dy—

Tb binary alloy hydride powder, each of which has an average powder particle diameter of 0.1 to 50 μ

m, at 0.01 to 5 mol %, followed by mixing so as to produce a mixed powder;

carrying out hydrogen absorption by heating, or heating and holding the mixed powder from room temperature to a temperature below 500°

C. in a hydrogen gas atmosphere with a pressure of 10 to 1,000 kPa so as to induce the mixed powder to absorb hydrogen;

carrying out hydrogen absorption-decomposition by heating and holding the mixed powder at a temperature in a range of 500 to 1,000°

C. in a hydrogen gas atmosphere with a pressure of 10 to 1,000 kPa so as to induce the mixed powder to absorb hydrogen and to be decomposed;

carrying out intermediate heat treatment by holding the mixed powder subjected to the hydrogen absorption-decomposition at a temperature in a range of 500 to 1,000°

C. in an inert gas atmosphere with a pressure of 10 to 1,000 kPa; and

then

carrying out hydrogen desorption by holding the mixed powder at a temperature in a range of 500 to 1,000°

C. in a vacuum atmosphere with an ultimate pressure of 0.13 kPa or below so as to forcibly release hydrogen and promote a phase transformation, followed by cooling and pulverizing.

10. A method of producing a rare earth magnet powder, comprising:

milling a rare earth magnet alloy raw material in an inert gas atmosphere to an average powder particle diameter of 10 to 1,000 μ

m so as to produce a rare earth magnet alloy raw material powder;

adding to the rare-earth magnet alloy raw material powder a Dy hydride powder, a Tb hydride powder, or a Dy—

Tb binary alloy hydride powder, each of which has an average powder particle diameter of 0.1 to 50 μ

m, at 0.01 to 5 mol %, followed by mixing so as to produce a mixed powder;

carrying out hydrogen absorption by heating, or heating and holding the mixed powder from room temperature to a temperature below 500°

C. in a hydrogen gas atmosphere with a pressure of 10 to 1,000 kPa so as to induce the mixed powder to absorb hydrogen;

carrying out hydrogen absorption-decomposition by heating and holding the mixed powder at a temperature in a range of 500 to 1,000°

C. in a hydrogen gas atmosphere with a pressure of 10 to 1,000 kPa so as to induce the mixed powder to absorb hydrogen and to be decomposed;

carrying out heat treatment in depressurized hydrogen with some hydrogen remaining in the mixed powder by holding the mixed powder subjected to the hydrogen absorption-decomposition at a temperature in a range of 500 to 1,000°

C. in a hydrogen atmosphere with an absolute pressure of at least 0.65 but less than 10 kPa or in a mixed hydrogen/inert gas atmosphere with a hydrogen partial pressure of at least 0.65 but less than 10 kPa; and

then

carrying out hydrogen desorption by holding the mixed powder at a temperature in a range of 500 to 1,000°

C. in a vacuum atmosphere with an ultimate pressure of 0.13 kPa or below so as to forcibly release hydrogen and promote a phase transformation, followed by cooling and pulverizing.

12. A method of producing a rare earth magnet powder according to any one of claims 8 to 11, wherein the rare earth magnet alloy raw material has been homogenized by holding in a vacuum or Ar gas atmosphere at a temperature of 600 to 1,200°

C.

18. A method of producing a rare earth magnet, comprising:

binding a rare earth magnet powder which is excellent in magnetic anisotropy and thermal stability produced by the method according to any one of claims 8 to 11 and 13 to 16 with an organic binder or a metal binder.

19. A method of producing a rare earth magnet, comprising:

molding a rare earth magnet powder which is excellent in magnetic anisotropy and thermal stability produced by the method according to any one of claims 8 to 11 and 13 to 16 so as to produce a green compact; and

processing the green compact with hot pressing or hot isostatic pressing at a temperature of 600 to 900°

C.

20. A method of producing a rare earth magnet powder according to any one of claims 8 to 11 and 13 to 16, wherein

the rare earth magnet alloy raw material comprises:

a chemical composition comprising R′

;

10 to 20 atm % (wherein R′

represents one, or two or more rare earth elements being inclusive of Y but exclusive of Dy and Tb) and B;

3 to 20 atm %, with the balance comprising Fe and inevitable impurities;

a chemical composition comprising R′

;

10 to 20 atm %, B;

3 to 20 atm %, and M;

0.001 to 5 atm % (wherein M represents one, or two or more from among Ga, Zr, Nb, Mo, Hf, Ta, W, Ni, Al, Ti, V, Cu, Cr, Ge, C, and Si), with the balance comprising Fe and inevitable impurities;

a chemical composition comprising R′

;

10 to 20 atm %, Co;

0.1 to 50 atm %, and B;

3 to 20 atm %, with the balance comprising Fe and inevitable impurities;

or

a chemical composition comprising R′

;

10 to 20 atm %, Co;

0.1 to 50 atm %, B;

3 to 20 atm %, and M;

0.001 to 5 atm %, with the balance comprising Fe and inevitable impurities.

11. A method of producing a rare earth magnet powder, comprising:

milling a rare earth magnet alloy raw material in an inert gas atmosphere to an average powder particle diameter of 10 to 1,000 μ

m so as to produce a rare earth magnet alloy raw material powder;

adding to the rare earth magnet alloy raw material powder a Dy hydride powder, a Tb hydride powder, or a Dy—

Tb binary alloy hydride powder, each of which has an average powder particle diameter of 0.1 to 50 μ

m, at 0.01 to 5 mol %, followed by mixing so as to produce a mixed powder;

carrying out hydrogen absorption by heating, or heating and holding the mixed powder from room temperature to a temperature below 500°

C. in a hydrogen gas atmosphere with a pressure of 10 to 1,000 kPa so as to induce the mixed powder to absorb hydrogen;

carrying out hydrogen absorption-decomposition by heating and holding the mixed powder at a temperature in a range of 500 to 1,000°

C. in a hydrogen gas atmosphere with a pressure of 10 to 1,000 kPa so as to induce the mixed powder to absorb hydrogen and to be decomposed;

carrying out intermediate heat treatment by holding the mixed powder subjected to the hydrogen absorption-decomposition at a temperature in a range of 500 to 1,000°

C. in an inert gas atmosphere with a pressure of 10 to 1,000 kPa;

carrying out heat treatment in depressurized hydrogen with some hydrogen remaining in the mixed powder by holding the mixed powder subjected to the intermediate heat treatment at a temperature in a range of 500 to 1,000°

C. in a hydrogen atmosphere with an absolute pressure of at least 0.65 but less than 10 kPa or in a mixed hydrogen/inert gas atmosphere with a hydrogen partial pressure of at least 0.65 but less than 10 kPa; and

then

carrying out hydrogen desorption by holding the mixed powder at a temperature in a range of 500 to 1,000°

C. in a vacuum atmosphere with an ultimate pressure of 0.13 kPa or below so as to forcibly release hydrogen and promote a phase transformation, followed by cooling and pulverizing.

13. A method of producing a rare earth magnet powder, comprising:

subjecting a rare earth magnet alloy raw material to hydrogen absorption by heating, or heating and holding the rare earth magnet alloy raw material from room temperature to a temperature below 500°

C. in a hydrogen gas atmosphere with a pressure of 10 to 1,000 kPa so as to induce the rare earth magnet alloy raw material to absorb hydrogen;

milling the hydrogen-absorbing rare earth magnet alloy raw material to an average powder particle diameter of 10 to 1,000 μ

m so as to produce a hydrogen-absorbing rare earth magnet alloy raw material powder;

adding to the hydrogen-absorbing rare earth magnet alloy raw material powder a Dy hydride powder, a Tb hydride powder, or a Dy—

Tb binary alloy hydride powder, each of which has an average powder particle diameter of 0.1 to 50 μ

m, at 0.01 to 5 mol %, followed by mixing so as to produce a hydrogen-containing raw material mixed powder;

carrying out hydrogen absorption-decomposition by heating and holding the hydrogen-containing raw material mixed powder at a temperature in a range of 500 to 1,000°

C. in a hydrogen gas atmosphere with a pressure of 10 to 1,000 kPa so as to induce the hydrogen-containing raw material mixed powder to absorb further hydrogen and to be decomposed; and

then

carrying out hydrogen desorption by holding the hydrogen-containing raw material mixed powder at a temperature in a range of 500 to 1,000°

C. in a vacuum atmosphere with an ultimate pressure of 0.13 kPa or below so as to forcibly release hydrogen and promote a phase transformation, followed by cooling and pulverizing.

17. A method of producing a rare earth magnet powder according to any one of claims 13 to 16, wherein a rare earth magnet alloy raw material for producing the hydrogen-absorbing rare earth magnet alloy raw material powder has been homogenized by holding in a vacuum or Ar gas atmosphere at a temperature of 600 to 1,200°

C.

14. A method of producing a rare earth magnet powder, comprising:

adding to a hydrogen-absorbing rare earth magnet alloy raw material powder a Dy hydride powder, a Tb hydride powder, or a Dy—

Tb binary alloy hydride powder, each of which has an average powder particle diameter of 0.1 to 50 μ

m, at 0.01 to 5 mol %, followed by mixing so as to produce a hydrogen-containing raw material mixed powder;

carrying out hydrogen absorption-decomposition by heating and holding the hydrogen-containing raw material mixed powder at a temperature in a range of 500 to 1,000°

C. in a hydrogen gas atmosphere with a pressure of 10 to 1,000 kPa so as to induce the hydrogen-containing raw material mixed powder to absorb further hydrogen and to be decomposed;

carrying out intermediate heat treatment by holding the hydrogen-containing raw material mixed powder subjected to the hydrogen absorption-decomposition at a temperature in a range of 500 to 1,000°

C. in an inert gas atmosphere with a pressure of 10 to 1,000 kPa; and

then

carrying out hydrogen desorption by holding the hydrogen-containing raw material mixed powder at a temperature in a range of 500 to 1,000°

C. in a vacuum atmosphere with an ultimate pressure of 0.13 kPa or below so as to forcibly release hydrogen and promote a phase transformation, followed by cooling and pulverizing.

15. A method of producing a rare earth magnet powder, comprising:

adding to a hydrogen-absorbing rare earth magnet alloy raw material powder a Dy hydride powder, a Tb hydride powder, or a Dy—

Tb binary alloy hydride powder, each of which has an average powder particle diameter of 0.1 to 50 μ

m, at 0.01 to 5 mol %, followed by mixing so as to produce a hydrogen-containing raw material mixed powder;

carrying out hydrogen absorption-decomposition by heating and holding the hydrogen-containing raw material mixed powder at a temperature in a range of 500 to 1,000°

C. in a hydrogen gas atmosphere with a pressure of 10 to 1,000 kPa so as to induce the hydrogen-containing raw material mixed powder to absorb further hydrogen and to be decomposed;

carrying out heat treatment in depressurized hydrogen with some hydrogen remaining in the hydrogen-containing raw material mixed powder by holding the hydrogen-containing raw material mixed powder subjected to the hydrogen absorption-decomposition at a temperature in a range of 500 to 1,000°

C. in a hydrogen atmosphere with an absolute pressure of at least 0.65 but less than 10 kPa or in a mixed hydrogen/inert gas atmosphere with a hydrogen partial pressure of at least 0.65 but less than 10 kPa; and

then

carrying out hydrogen desorption by holding the hydrogen-containing raw material mixed powder at a temperature in a range of 500 to 1,000°

C. in a vacuum atmosphere with an ultimate pressure of 0.13 kPa or below so as to forcibly release hydrogen and promote a phase transformation, followed by cooling and pulverizing.

16. A method of producing a rare earth magnet powder, comprising:

adding to a hydrogen-absorbing rare earth magnet alloy raw material powder a Dy hydride powder, a Tb hydride powder, or a Dy—

Tb binary alloy hydride powder, each of which has an average powder particle diameter of 0.1 to 50 μ

m, at 0.01 to 5 mol %, followed by mixing so as to produce a hydrogen-containing raw material mixed powder;

carrying out hydrogen absorption-decomposition by heating and holding the hydrogen-containing raw material mixed powder at a temperature in a range of 500 to 1,000°

C. in a hydrogen gas atmosphere with a pressure of 10 to 1,000 kPa so as to induce the hydrogen-containing raw material mixed powder to absorb further hydrogen and to be decomposed;

carrying out intermediate heat treatment by holding the hydrogen-containing raw material mixed powder subjected to the hydrogen absorption-decomposition at a temperature in a range of 500 to 1,000°

C. in an inert gas atmosphere with a pressure of 10 to 1,000 kPa; and

then

carrying out heat treatment in depressurized hydrogen with some hydrogen remaining in the hydrogen-containing raw material mixed powder by holding the hydrogen-containing raw material mixed powder subjected to the intermediate heat treatment at a temperature in a range of 500 to 1,000°

C. in a hydrogen atmosphere with an absolute pressure of at least 0.65 but less than 10 kPa or in a mixed hydrogen/inert gas atmosphere with a hydrogen partial pressure of at least 0.65 but less than 10 kPa; and

then

carrying out hydrogen desorption by holding the hydrogen-containing raw material powder at a temperature in a range of 500 to 1,000°

C. in a vacuum atmosphere with an ultimate pressure of 0.13 kPa or below so as to forcibly release hydrogen and promote a phase transformation, followed by cooling and pulverizing.