Rare earth permanent magnet and method for making same

• US 6,302,939 B1
• Filed: 02/01/1999
• Issued: 10/16/2001
• Est. Priority Date: 02/01/1999
• Status: Expired due to Term

• Current Assignee: Magnequench International Incorporated
• Original Assignee: Magnequench International Incorporated
• Inventors: Rabin, Barry H., Sellers, Charles H.
• Primary Examiner(s): SHEEHAN, JOHN P
• Application Number:
  US09/241,978
• Time in Patent Office: 988 Days
• Field of Search: 753/33, 753/34, 753/38, 753/39
• US Class Current: 75/338
• CPC Class Codes: B22F 1/08 Metallic powder characterised by particles having an amorphous microstructure
• CPC Class Codes: B22F 1/142 Thermal or thermo-mechanical treatment
• CPC Class Codes: B22F 2998/00 Supplementary information concerning processes or compositions relating to powder metallurgy
• CPC Class Codes: B22F 9/008 Rapid solidification processing
• CPC Class Codes: B22F 9/10 using centrifugal force
• CPC Class Codes: C22C 1/0441 Alloys based on intermetallic compounds of the type rare earth - Co, Ni
• CPC Class Codes: H01F 1/0574 obtained by liquid dynamic compaction
• CPC Class Codes: H01F 1/058 and IVa elements, e.g. Gd2Fe14C
• CPC Class Codes: H01F 1/059 and Va elements, e.g. Sm2Fe17N2

Abstract

A rare earth permanent magnet alloy having a composition expressed as R_xF_{100−(x+y+z+m+n)}B_yT_zM_mD_n. In this formula, R is one or more of rare earthy elements, such as neodymium, lanthanum, cerium, dysprosium and/or praseodymium; F is Fe or Fe and up to 20 atomic percent of Co by substitution; B is boron; T is one or more elements selected from the group of Ti, Zr, Cr, Mn, Hf, Nb, V, Mo, W and Ta; M is one or more elements selected from the group of Si, Al, Ge, Ga, Cu, Ag, and Au; and D is one or more elements selected from the group of C, N, P, and O. In this formula, x, y, z, m, n are atomic percentages in the ranges of 3<x<15, 4<y<22, 0.5<z<5, 0.1<m<2, and 0.1<n<4. Fine amorphous particles of such alloy are made by atomization and/or splat-quenching. Both substantially-spherical, irregular and substantially plate-like particles are simultaneously produced.

Claims

1. Method for producing a mixture of particles of different morphologies comprising one or more rare earth elements, iron and boron, said method comprising the steps of:

providing a molten alloy comprising rare earth, iron and boron;

introducing said molten alloy onto a rotating disk to produce droplets of said alloy;

cooling said droplets by subjecting said droplets to a gaseous cooling medium such that a first portion of said droplets solidifies into substantially spherical or irregular particles and a second portion of said droplets remains molten;

impacting said second portion of said droplets and said substantially spherical or irregular particles, after being cooled by said gaseous cooling medium, onto a splat shield such that said second portion of said droplets impact said splat shield to form substantially plate-like particles.

2. The method of claim 1, wherein the substantially spherical or irregular particles have diameters ranging between 1 and 200 micrometers.

3. The method of claim 1, wherein the plate-like particles have sizes ranging between 50 and 500 micrometers in length and between 20 and 100 micrometers in thickness.

4. The method of claim 1, wherein said impacting of said second portion of said droplets is performed at a cooling rate of between 10,000 and 100,000°

K/second.

5. The method of claim 1, wherein said substantially plate-like particles are formed at a rate of between 0.5 and 100 kg/minute.

6. The method of claim 1, wherein said gaseous cooling medium is helium gas.

7. The method of claim 1, wherein said splat shield is a stationary or rotating water-cooled splat quenching shield.