PROCESS FOR PRODUCING SINTERED R-T-B MAGNET

• US 20140329007A1
• Filed: 02/28/2013
• Published: 11/06/2014
• Est. Priority Date: 03/30/2012
• Status: Abandoned Application

• Current Assignee: Hitachi Metals (Thailand) Ltd.
• Original Assignee: Hitachi Metals (Thailand) Ltd.
• Inventors: Obata, Tohru
• Application Number:
  US14/362,140
• Publication Number:
  US 20140329007A1
• Time in Patent Office: Days
• US Class Current: 427/127
• CPC Class Codes: B22F 2999/00 Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B22F 3/00 Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
• CPC Class Codes: B22F 3/003 Apparatus, e.g. furnaces in general F27B
• CPC Class Codes: B22F 3/1007 Atmosphere B22F3/1021 takes precedence
• CPC Class Codes: B22F 3/26 Impregnating making ferrous alloys by impregnation C22C33/0242
• CPC Class Codes: C22C 19/03 based on nickel
• CPC Class Codes: C22C 21/00 Alloys based on aluminium
• CPC Class Codes: C22C 33/02 by powder metallurgy working metallic powder B22F
• CPC Class Codes: C22C 33/0278 with at least one alloying element having a minimum content above 5%
• CPC Class Codes: C22C 38/00 Ferrous alloys, e.g. steel alloys cast-iron alloys C22C37/00
• 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: C22C 38/02 containing silicon
• CPC Class Codes: C22C 38/06 containing aluminium
• CPC Class Codes: C22C 38/10 containing cobalt
• CPC Class Codes: C22C 38/16 containing copper
• CPC Class Codes: F27B 5/04 adapted for treating the charge in vacuum or special atmosphere
• CPC Class Codes: F27B 5/10 Muffles
• CPC Class Codes: F27D 5/00 Supports, screens, or the like for the charge within the furnace travelling or movable supports F27D3/12
• CPC Class Codes: F27D 7/06 Forming or maintaining special atmospheres or vacuum within heating chambers F27D7/02 takes precedence
• CPC Class Codes: H01F 1/0577 : sintered
• CPC Class Codes: H01F 41/0293 : diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets

Abstract

A method according to the present disclosure includes the steps of: stacking RH diffusion sources and sintered R-T-B based magnet bodies alternately one upon the other with a flat plate holding member having openings interposed between each pair of the diffusion source and the magnet body, thereby forming a multilayer structure; loading the multilayer structure in a process vessel; (A) performing an RH supply-diffusion process at a pressure of 2.0 Pa to 50 Pa and at a temperature of 800° C. to 950° C. in the process vessel; and (B) performing an RH diffusion process at a pressure of 150 Pa to 2 kPa and at a temperature of 800° C. to 950° C. in the process vessel. The method includes the step of carrying out the steps (A) and (B) alternately and repeatedly at least twice.

Claims

1. :

A method for producing a sintered R-T-B based magnet, the method comprising the steps of;

stacking RH diffusion sources (each being a metal or alloy, of which at least 80 at % is a heavy rare-earth element RH that is at least one of Dy and Tb) and sintered R-T-B based magnet bodies (where R is at least one of the rare-earth elements and T is at least one of the transition metal elements and always includes Fe) alternately one upon the other with a flat plate holding member having openings interposed between each pair of the diffusion source and the magnet body, thereby forming a multilayer structure;

loading the multilayer structure in a process vessel;

(A) performing an RH supply-diffusion process at a pressure of 2.0 Pa to 50 Pa and at a temperature of 800°

C. to 950°

C. in the process vessel; and

(B) performing an RH diffusion process at a pressure of 150 Pa to 2 kPa and at a temperature of 800°

C. to 950°

C. in the process vessel, and

wherein the method includes the step of carrying out the steps (A) and (B) alternately and repeatedly at least twice.

2. :

The method of claim 1, wherein the holding member has a thickness of 0.1 mm to 4 mm.

3. :

The method of claim 1, comprising the step of cooling the temperature in the process vessel to 500°

C. at a cooling rate of 1°

C./min to 15°

C./min after the steps (A) and (B) have been alternately carried out at least twice.

4. :

The method of claim 1, wherein the process vessel is subjected to an evacuation process using either a rotary pump alone or a rotary pump and a mechanical booster pump in combination.