Method for producing r-t-b based sintered magnet

Patent metadata

Field	Value
Publication number	US-2016284468-A1
Application number	US-201414915801-A
Country	US
Kind code	A1
Filing date	Sep 1, 2014
Priority date	Sep 2, 2013
Publication date	Sep 29, 2016
Grant date	—

Abstract

Disclosed is a method for producing a magnet, including a step of preparing a magnet represented by the formula: uRwBxGayCuzAlqM(balance)T, where RH is 5% or less, 0.20≦x≦0.70, 0.07≦y≦0.2, 0.05≦z≦0.5, 0≦q≦0.1; when 0.40≦x≦0.70, v and w satisfy the following inequality expressions: 50w−18.5≦v≦50w−14, and −12.5w+38.75≦v≦−62.5w+86.125; and, when 0.20≦x≦0.40, v and w satisfy the following inequality expressions: 50w−18.5≦v≦50w−15.5 and −12.5w+39.125≦v≦−62.5w+86.125, and x satisfy the following inequality expression: −(62.5w+v −81.625)/15+0.5≦x≦−(62.5w+v−81.625)/15+0.8; a high-temperature heat treatment step of heating the magnet to a temperature of 730° C. or higher and 1,020° C. or lower, and then cooling to 300° C. at a cooling rate of 20° C./min; and a low-temperature heat treatment step of heating the magnet to a temperature of 440° C. or higher and 550° C. or lower.

First claim

1 . A method for producing an R-T-B based sintered magnet comprising:
a step of preparing an R-T-B based sintered magnet material, which is represented by the following formula (1):
uBuBxGayCuzAlqM(100-u-w-x-y-z-q)T   (1)

where R is composed of light rare-earth element(s) RL and a heavy rare-earth element(s) RH, RL is Nd and/or Pr, RH is at least one of Dy, Tb, Gd and Ho, T is a transition metal element and includes Fe, M is Nb and/or Zr, and u, w, x, y, z, q, and 100-u-w-x-y-z-q are expressed in terms of % by mass; the RH accounts for 5% by mass or less of the R-T-B based sintered magnet, the following inequality expressions (2) to (5) being satisfied:
0.20≦x≦0.70   (2)

0.07≦y≦0.2   (3)

0.05≦z≦0.5   (4)

0≦q≦ 0 . 1   (5)

v=u−(6α+10β+8γ), where the amount of oxygen (% by mass) of the R-T-B based sintered magnet is α, the amount of nitrogen (% by mass) is β, and the amount of carbon (% by mass) is γ; when 0.40≦x≦0.70, v and w satisfy the following inequality expressions (6) and (7):
50 w− 18.5 ≦v≦ 50 w− 14   (6)

−12.5 w+ 38.75 ≦v≦− 62.5 w+ 86.125   (7)

and, when 0.20≦x≦0.40, v and w satisfy the following inequality expressions (8) and (9), and x satisfies the following inequality expression (10):
50 w− 18.5 ≦v≦ 50 w− 15.5   (8)

−12.5 w+ 39.125 ≦v≦− 62.5 w+ 86.125   (9)

a high-temperature heat treatment step of heating the R-T-B based sintered magnet material to a temperature of 730° C. or higher and 1,020° C. or lower, and then cooling to 300° C. at a cooling rate of 20° C./min; and a low-temperature heat treatment step of heating the R-T-B based sintered magnet material, after the high-temperature heat treatment step, to a temperature of 440° C. or higher and 550° C. or lower.

2 . The method for producing an R-T-B based sintered magnet according to claim 1 , wherein the low-temperature heat treatment step is a step of heating to a temperature of 480° C. or higher and 550° C. or lower.

3 . The method for producing an R-T-B based sintered magnet according to claim 1 , wherein the amount of oxygen of the R-T-B based sintered magnet obtained is 0.15% by mass or less.

4 . The method for producing an R-T-B based sintered magnet according to claim 1 , wherein, when 0.40≦x≦0.70, v and w satisfy the following inequality expressions (11) and (7):
50 w− 18.5 ≦v≦ 50 w− 16.25   (11)

−12.5 w+ 38.75 ≦v≦− 62.5 w+ 86.125   (7)

and, when 0.20≦x≦0.40, v and w satisfy the following inequality expressions (12) and (9), and x satisfies the following inequality expression (10):
50 w− 18.5 ≦v≦ 50 w− 17.0   (12)

−12.5 w+ 39.125 ≦v≦− 62.5 w+ 86.125   (9)

−(62.5 w+v− 81.625)/15+0.5 x ≦−(62.5 w+v− 81.625)/15+0.8   (10).

5 . The method for producing an R-T-B based sintered magnet according to claim 4 , wherein the low-temperature heat treatment step is a step of heating to a temperature of 480° C. or higher and 550° C. or lower.

6 . The method for producing an R-T-B based sintered magnet according to claim 4 , wherein the amount of oxygen of the R-T-B based sintered magnet obtained is 0.15% by mass or less.

7 . The method for producing an R-T-B based sintered magnet according to claim 2 , wherein the amount of oxygen of the R-T-B based sintered magnet obtained is 0.15% by mass or less.

8 . The method for producing an R-T-B based sintered magnet according to claim 5 , wherein the amount of oxygen of the R-T-B based sintered magnet obtained is 0.15% by mass or less.

Assignees

• Hitachi Metals Ltd

Inventors

• YAMAGATA Ryouichi
• Ishii Rintaro
• Kuniyoshi Futoshi
• Satoh Teppei

Classifications

• C22C38/06

  containing aluminium · CPC title

• C22C38/001

  containing N · CPC title

• C22C38/10

  containing cobalt · CPC title

• H01F1/0577

  sintered · CPC title

• C22C38/14

  containing titanium or zirconium · CPC title