R-T-B based sintered magnet and motor

Patent metadata

Field	Value
Publication number	US-10109403-B2
Application number	US-201414909563-A
Country	US
Kind code	B2
Filing date	Aug 8, 2014
Priority date	Aug 9, 2013
Publication date	Oct 23, 2018
Grant date	Oct 23, 2018

Abstract

The present invention provides an R-T-B based sintered magnet that inhibits the demagnetization rate at high temperature even when less or no heavy rare earth elements such as Dy, Tb and the like are used. The R-T-B based sintered magnet comprises R 2 T 14 B crystal grains and two-grain boundary parts between the R 2 T 14 B crystal grains. Two-grain boundary parts formed by a phase containing R, Cu, Co, Ga and Fe with a ratio of 40≤R≤70, 1≤Co≤10, 5≤Cu≤50, 1≤Ga≤15, and 1≤Fe≤40 (wherein, R+Cu+Co+Ga+Fe=100, and R is at least one selected from rare earth elements) exists in the magnet.

First claim

What is claimed is:

1. An R-T-B based sintered magnet comprising R 2 T 14 B crystal grains and two-grain boundary parts between the R 2 T 14 B crystal grains,
wherein the two-grain boundary parts are formed at least by:
(i) a phase containing R, Cu, Co, Ga and Fe with an atomic ratio of 40≤R≤70, 1≤Co≤10, 5≤Cu≤50, 1≤Ga≤15, and 1≤Fe≤40 exist, R+Cu+Co+Ga+Fe=100, R is at least one selected from rare earth elements, T is Fe and optionally one or more other elements of iron group, and
(ii) a phase containing R, Cu, Ga, Fe and optionally Co with an atomic ratio of 10≤R≤20, 0≤Co<0.5, 0<Cu<1, and 1≤Ga≤10 exist, R+Cu+Co+Ga+Fe=100, and

the contents of the elements relative to the total mass in the R-T-B based sintered magnet are shown as follows:
R: 29.5 to 33.1 mass %;
B: 0.75 to 0.95 mass %;
Ga: 0.01 to 1.0 mass %;
Cu: 0.01 to 1.5 mass %;
Co: 0.3 to 3.0 mass %;
Al: 0.03 to 0.6 mass %;
Fe: balance, substantially;
the total content of elements other than Fe occupying the balance: 5 mass % or lower,
the ratio of Nd and Pr in R is 95 to 100 atomic %, and
the content of heavy rare earth elements in total mass of the R-T-B based sintered magnet is 1.0 mass % or less.

2. The R-T-B based sintered magnet according to claim 1 , wherein the average thickness of the two-grain boundary parts formed by said phase is 5˜500 nm.

3. A motor comprising the R-T-B based sintered magnet according to claim 1 .

4. A motor comprising the R-T-B based sintered magnet according to claim 2 .

Assignees

• Tdk Corp

Inventors

• Kanada Isao
• Ono Hiroyuki
• Kato Eiji
• Miwa Masashi

Classifications

• H01F1/0577 Primary

  sintered · CPC title

• B22F2998/10

  Processes characterised by the sequence of their steps · CPC title

• B22F3/087

  using high energy impulses, e.g. magnetic field impulses · CPC title

• B22F2202/05

  Use of magnetic field · CPC title

• C22C38/06

  containing aluminium · CPC title