Method of making material alloy for iron-based rare earth magnet

• US 6,695,929 B2
• Filed: 08/05/2002
• Issued: 02/24/2004
• Est. Priority Date: 02/07/2001
• Status: Expired due to Term

• Current Assignee: Sumitomo Special Metals Co Ltd (Hitachi, Ltd.)
• Original Assignee: Sumitomo Special Company Limited
• Inventors: Kanekiyo, Hirokazu, Hirosawa, Satoshi
• Primary Examiner(s): SHEEHAN, JOHN P
• Application Number:
  US10/203,023
• Publication Number:
  US 20030136468A1
• Time in Patent Office: 568 Days
• Field of Search: 148/101, 148/102, 148/103, 148/538, 148/540, 164/463, 164/474, 164/475, 164/477, 164/479, 164/488, 164/489, 164/490
• US Class Current: 148/101
• CPC Class Codes: B22D 11/0611 formed by a single casting wheel, e.g. for casting amorphous metal strips or wires
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: C22C 1/0441 Alloys based on intermetallic compounds of the type rare earth - Co, Ni
• CPC Class Codes: C22C 38/002 containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• CPC Class Codes: C22C 38/005 containing rare earths, i.e. Sc, Y, Lanthanides
• CPC Class Codes: H01F 1/0571 in the form of particles, e.g. rapid quenched powders or ribbon flakes
• CPC Class Codes: H01F 1/0578 bonded together
• CPC Class Codes: H01F 1/0579 with exchange spin coupling between hard and soft nanophases, e.g. nanocomposite spring magnets
• CPC Class Codes: H01F 1/058 and IVa elements, e.g. Gd2Fe14C

Abstract

A melt of an iron-based rare earth material alloy, represented by (Fe_1-mT_m)_100-x-y-zQ_xR_yM_z, is prepared, wherein T is Co and/or Ni; Q is B and/or C; R is selected from Y (yttrium) and the rare earth elements; M is selected from Al, Si, Ti, V, Cr, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au and Pb; 10≦x≦30 at %; 2%≦y<10 at %; 0≦z≦10 at % and 0≦m≦0.5. The melt is fed onto a guide to form a flow of the melt thereon and move the melt onto a melt/chill roller contact region, where the melt is rapidly cooled by the chill roller to make a rapidly solidified alloy. An oxygen concentration of the melt yet to be fed onto the guide is controlled at about 3,000 ppm or less in mass percentage.

Claims

1. A method of making a material alloy for an iron-based rare earth magnet, the method comprising the steps of:

preparing a melt of an iron-based rare earth material alloy, the material alloy having a composition represented by the general formula;

(Fe_1-mT_m)_100-x-y-zQ_xR_yM_z, where T is at least one element selected from the group consisting of Co and Ni;

Q is at least one element selected from the group consisting of B and C;

R is at least one element selected from the group consisting of Y (yttrium) and the rare earth elements; and

M is at least one element selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au and Pb, the mole fractions x, y, z and m satisfying the inequalities of;

10 at %≦

x≦

30 at %;

2 at %≦

y<

10 at %;

0 at %≦

z≦

10 at %; and

0≦

m≦

0.5, respectively;

feeding the melt of the material alloy onto a guide and forming a flow of the melt on the guide for transfer to a chill roller so as to move the melt onto a region where the melt comes into contact with the chill roller;

rapidly cooling the melt using the chill roller to make a rapidly solidified alloy; and

controlling an oxygen concentration of the melt yet to be fed onto the guide such that the oxygen concentration is about 3,000 ppm or less in mass percentage.

2. The method of claim 1, further comprising the step of controlling a kinematic viscosity of the melt yet to be fed onto the guide such that the kinematic viscosity of the melt is about 5×

10<sup>−

6</sup> m²/sec or less.

3. The method of claim 1, wherein the rapid cooling step comprises the step of using, as the guide, a shoot that controls the flow of at least a portion of the melt running down toward the surface of the chill roller rotating to bring the melt into contact with the surface of the chill roller such that the melt has a predetermined width in an axial direction of the chill roller, the shoot being disposed near the chill roller and including a melt drain that has the predetermined width in the axial direction of the chill roller, and wherein the rapid cooling step further comprises the step of making the rapidly solidified alloy from the melt that has come into contact with the chill roller.

4. The method of claim 1 wherein the rapid cooling step comprises the step of precipitating an R₂Fe₁₄B phase.

5. A method for producing a permanent magnet, the method comprising the step of heat-treating the rapidly solidified alloy, prepared by the method of claim 1 to form a structure in which three or more crystalline phases, including at least R₂Fe₁₄B, α

-Fe and boride phases, are present, an average crystal grain size of the R₂Fe₁₄B phase is between about 20 nm and about 150 nm, and an average crystal grain size of the α

-Fe and boride phases is between about 1 nm and about 50 nm.

6. The method of claim 5 wherein the heat-treating step comprises the step of maintaining the rapidly solidified alloy at a temperature of about 550°

C. to about 850°

C. for approximately 30 seconds or more.

7. The method of claim 5 wherein the boride phase comprises an iron-based boride phase with ferromagnetic properties.

8. The method of claim 1 wherein the iron-based boride phase comprises at least one of Fe₃B and Fe₂₃B₆.

9. A method for producing a permanent magnet by using a powder of the rapidly solidified alloy that has been prepared by the method of claim 1.

10. A method for producing a bonded magnet, the method comprising the steps of:

preparing a powder of the permanent magnet according to the method of claim 5; and

processing the powder of the permanent magnet into the bonded magnet.