Process for producing hard-magnetic parts

• US 5,733,384 A
• Filed: 02/11/1997
• Issued: 03/31/1998
• Est. Priority Date: 06/14/1995
• Status: Expired due to Fees

• Current Assignee: Institut FUER Festkoerper-Und Werkstoffschung Dresden EV
• Original Assignee: Institut FUER Festkoerper-Und Werkstofforschung
• Inventors: Cao, Lei, Neu, Volker, Schultz, Ludwig, Mueller, Karl-Hartmut, Handstein, Axel
• Primary Examiner(s): SHEEHAN, JOHN P
• Application Number:
  US08/793,156
• Time in Patent Office: 413 Days
• Field of Search: 148/101, 148/103, 148/104, 148/105
• US Class Current: 148/104
• CPC Class Codes: C22C 1/0441 Alloys based on intermetallic compounds of the type rare earth - Co, Ni
• CPC Class Codes: H01F 1/058 and IVa elements, e.g. Gd2Fe14C

Abstract

A process is provided for a technologically controllable, economic production of hard-magnetic parts from Sm₂ --(Fe,M)₁₇ --C_y -base work materials with interstitial inclusions, where M designates gallium and/or at least one metallic element serving to stabilize a rhombohedral 2:17 structure. A Sm₂ Fe_17-x M_x C_y powder mixture is produced, where x>0.1 and 3≧y≧0. The mixture is subjected to an intensive fine grinding process in a ball mill. The finely ground mixture is heat-treated in a temperature range from 650° C. to 900° C. for partial or complete recrystallization. The resulting ultra-fine-grain Sm₂ Fe_17-x M_x C_y magnetic powder is compacted to produce magnet bodies by a hot pressing processing in a temperature range from 650° C. to 900° C. The process is applicable, for example, for the production of hard-magnetic parts based on interstitial Sm₂ Fe₁₇ C_y compounds.

Claims

1. A process for the production of hard-magnetic parts from Sm₂ --(Fe,M)₁₇ --C_y -base work materials, where M designates at least one of gallium and at least one metallic element serving to stabilize a rhombohedral 2:

17 structure, comprising the steps of;

a) producing a Sm₂ Fe_17-x M_x C_y powder mixture, where x>

0.1 and 3≧

y≧

0;

b) subjecting the mixture to an intensive fine grinding process in a ball mill;

c) heat-treating the finely ground mixture in a temperature range from 650°

C. to 900°

C. for partial or complete recrystallization; and

d) compacting the resulting ultra-fine-grain Sm₂ Fe_17-x M_x C_y magnetic powder to produce a magnet body by means of a hot pressing processing in a temperature range from 650°

C. to 900°

C.

2. The process according to claim 1, wherein the compacted magnet body is provided with a preferred magnetic orientation by means of a hot deformation process at a temperature ranging from 650°

C. to 900°

C. and at a pressure of more than 200 MPa.

3. The process according to claim 1, wherein samarium is mixed with iron, M and carbon or with an iron-carbon alloy and M in finely dispersed form, the mixture being in a ratio corresponding to the composition of Sm₂ Fe_17-x M_x C_y, where x>

0.1 and 3≧

y≧

0, in order to produce the powder mixture in process step a).

4. The process according to claim 3, wherein the metallic element M includes at least one element from the group of elements consisting of gallium, aluminum, molybdenum, niobium, tantalum, titanium and zirconium in process step a).

5. The process according to claim 3, wherein:

the powder mixture is produced in process step a) with a quantity of samarium such that a samarium content of less than 10 to 3 At-% results in the magnet body;

a grain size of less than 200 nm is generated in step b) from the powder mixture by selection of grinding intensity and grinding duration; and

the grain growth is limited to a value of less than 200 nm in steps c) and d) and, in the event of a subsequent hot deformation of the magnet body, by selection of the heat treatment parameters.

6. The process according to claim 1, wherein, in order to produce the powder mixture according to process step a), a Sm₂ Fe_17-x M_x C_y alloy is produced by melt-metallurgy, where x>

0.1 and 3≧

y≧

0, the alloy is subjected to homogenizing annealing in a temperature range of 900°

C. to 1200°

C. after solidification, and the alloy is then comminuted to a powder.

7. The process according to claim 1, wherein the metallic element M includes at least one element from the group of elements consisting of gallium, aluminum, molybdenum, niobium, tantalum, titanium and zirconium.

8. The process according to claim 1 wherein:

in order to produce the powder mixture according to process step a) an alloy is produced with samarium in an amount such that the samarium content in the magnet body is less than 10 to 3 At-%;

a grain size of less than 200 nm is generated in process step b) by selection of grinding intensity and grinding duration; and

the grain growth is limited to a value of less than 200 nm in steps c) and d) and, in the event of a subsequent hot deformation of the magnet body, by selection of the heat treatment parameters.

9. The process according to claim 1, wherein:

in order to produce the powder mixture in accordance with process step a), a Sm₂ Fe_17-x Ga_x C_y alloy is produced by melt-metallurgical methods, where x>

0.1 and 2≧

y≧

0;

after solidification the alloy is subjected to a homogenizing annealing in a temperature range of 900°

C. to 1200°

C.;

the alloy is then comminuted to a powder which is then subjected to an annealing treatment at temperatures from 600°

C. to 900°

C. in hydrogen gas and then under a vacuum; and

the powdered alloy is then alloyed up to a Sm₂ Fe_17-x Ga_x C_y alloy, where y≦

3, by means of heat treatment in a temperature range from 400°

C. to 600°

C. in a carbon-containing gas.

10. The process according to claim 9, wherein CH₄ or C₂ H₂ is used as carbon-containing gas to alloy the powder.

11. The process according to claim 6 wherein the metallic element M includes at least one element from the group of elements consisting of gallium, aluminum, molybdenum, niobium, tantalum, titanium and zirconium.

12. The process according to claim 6 wherein:

the alloy is produced with samarium in an amount such that the samarium content in the magnet body is less than 10 to 3 At-%;

a grain size of less than 200 mn is generated in process step b) by selection of grinding intensity and grinding duration; and

the grain growth is limited to a value of less than 200 nm in steps c) and d) and, in the event of a subsequent hot deformation of the magnet body, by selection of the heat treatment parameters.