Method for producing rare-earth magnet

• US 10,056,177 B2
• Filed: 01/30/2015
• Issued: 08/21/2018
• Est. Priority Date: 02/12/2014
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Sakuma, Noritsugu, Shoji, Tetsuya, Haga, Kazuaki
• Primary Examiner(s): Su, Xiaowei
• Application Number:
  US14/610,229
• Publication Number:
  US 20150228386A1
• Time in Patent Office: 1,299 Days
• Field of Search: None
• CPC Class Codes: B22F 1/07 Metallic powder characterised by particles having a nanoscale microstructure nanosized particles B22F1/054
• CPC Class Codes: B22F 2009/048 by pulverising a quenched ribbon
• CPC Class Codes: B22F 2998/10 Processes characterised by the sequence of their steps
• CPC Class Codes: B22F 2999/00 Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B22F 3/02 Compacting only
• CPC Class Codes: B22F 3/10 Sintering only
• CPC Class Codes: B22F 3/24 After-treatment of workpieces or articles B22F3/1146 takes precedence
• CPC Class Codes: B22F 3/26 Impregnating making ferrous alloys by impregnation C22C33/0242
• CPC Class Codes: C22C 2202/02 Magnetic
• CPC Class Codes: C22C 33/025 having an intermetallic of the REM-Fe type which is not magnetic
• CPC Class Codes: C22C 33/0257 characterised by the range of the alloying elements
• CPC Class Codes: C22C 38/001 containing N
• 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 38/10 containing cobalt
• CPC Class Codes: H01F 1/0557 sintered
• CPC Class Codes: H01F 1/0577 sintered
• CPC Class Codes: H01F 41/0266 Moulding; Pressing H01F41/0273 takes precedence; hard magnetic particles H01F1/06, H01F1/11
• CPC Class Codes: H01F 41/0293 diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets

Abstract

The present invention is a method capable of producing a rare-earth magnet with excellent magnetization and coercivity. The method includes producing a sintered body including a main phase and grain boundary phase and represented by (R1_1-xR2_x)_aTM_bB_cM_d (where R1 represents one or more rare-earth elements including Y, R2 represents a rare-earth element different than R1, TM represents transition metal including at least one of Fe, Ni, or Co, B represents boron, M represents at least one of Ti, Ga, Zn, Si, Al, etc., 0.01≤x≤1, 12≤a≤20, b=100−a−c−d, 5≤c≤20, and 0≤d≤3 (all at %)); applying hot deformation processing to the sintered body to produce a precursor of the magnet; and diffusing/infiltrating melt of a R3-M modifying alloy (rare-earth element where R3 includes R1 and R2) into the grain boundary phase of the precursor.

Claims

1. A method for producing a rare-earth magnet, comprising:

a first step of producing a sintered body with a structure including a main phase and a grain boundary phase, the sintered body consists of Nd, Pr, Fe, B, and M wherein the sintered body has a composition expressed by a formula;

(Nd_1-xPr_x)_aFe_bB_cM_d where B represents boron, M is at least one selected from the group consisting of Ti, Ga, Zn, Si, Al, Nb, Zr, Ni, Co, Mn, V, W, Ta, Ge, Cu, Cr, Hf, Mo, P, C, Mg, Hg, Ag, and Au, 0<

x <

0.5, 12≤

a≤

20, b=100−

a−

c−

d , 5≤

c ≤

20, and 0≤

d ≤

20, and 0≤

d ≤

3 all by at %;

a second step of applying hot deformation processing to the sintered body to produce a precursor of a rare-earth magnet; and

a third step of providing a Nd-Cu alloy consisting of Nd and Cu on a surface of the precursor of the rare-earth magnet and then heat treating the precursor of the rare-earth magnet to diffuse and infiltrate a melt of the Nd-Cu alloy into the grain boundary phase of the precursor of the rare-earth magnet to produce a rare-earth magnet,

wherein the rare-earth magnet has a main phase with a core-shell structure, wherein a composition of a shell formed around the core is a (NdPr)FeB phase, in which a content of Nd is more than a content of Pr,

wherein a proportion of the main phase to the entire structure of the rare-earth magnet being is 95% or greater by volume percent, and

the rare-earth magnet has a coercivity at 200°

C. of higher than 4.8 kOe and less than 5.6 kOe.