Permanent magnet

Claim 2

A magnetically anisotropic sintered permanent magnet of the FeBR system in which R represents the sum of R 1 and R 2 wherein: R 1 is at least one rare earth element selected from the group consisting of Dy, Tb, Gd and Ho, and at least 80 at % of R 2 consists of Nd and/or Pr, the balance being at least one other element selected from the group consisting of La, Ce and Y, said system consisting essentially of, by atomic percent, 0.2 to 5% of R 1 , 12.5 to 20% of R, 4 to 20% of B, and the balance being at least 60% Fe; said magnet having a tetragonal Fe-B-R crystal structure phase of at least 50 vol % of the entire magnet, and having a maximum energy product of at least 25 MGOe and an intrinsic coercive force of at least 13 kOe.

Claim 3

A magnetically anisotropic sintered permanent magnet of the FeBRM system in which R represents the sum of R 1 and R 2 wherein: R 1 is at least one rare earth element selected from the group consisting of Dy, Tb, Gd and Ho, at least 80 at % of R 2 consists of Nd and/or Pr, the balance being at least one other element selected from the group consisting of La, Ce and Y, and M represents additional elements M as specified hereinbelow, said system consisting essentially of, by atomic percent, 0.2 to 5% of R 1 , 12.5 to 20% of R, 4 to 20% of B, at least one of the additional elements M in the amount of no more than the atomic percentages as specified hereinbelow, and the balance being at least 60% Fe: M being: ______________________________________ 3% Ti, 3.3% Zr, 3.3% Hf, 4.5% Cr, 5% Mn, 6% Ni, 7% Ta, 3.5% Ge, 1.5% Sn, 1% Sb, 5% Bi, 5.2% Mo, 9% Nb, 5% Al, 5.5% V, and 5% W, ______________________________________ provided that, when two or more additional elements M are included, the sum of M is no more than the maximum atomic percentage among those specified above of said elements M actually added, said magnet having a tetragonal Fe-B-R crystal structure phase of at least 50 vol % of the entire magnet, and having a maximum energy product of at least 25 MGOe and an intrinsic coercive force of at least 13 kOe.

Claim 4

A magnetically anisotropic sintered permanent magnet of the FeBRM system in which R represents the sum of R 1 and R 2 wherein: R 1 is at least one rare earth element selected from the group consisting of Dy, Tb, Gd and Ho, at least 80 at % of R 2 consists of Nd and/or Pr, the balance being at least one other element selected from the group consisting of La, Ce and Y, and M represents additional elements M as specified hereinbelow, said system consisting essentially of, by atomic percent, 0.2 to 5% of R 1 , 12.5 to 20% of R, 4 to 20% of B, at least one of the additional elements M in the amount of no more than the atomic percentages as specified hereinbelow, and the balance being at least 60% Fe: M being: ______________________________________ 3% Ti, 3.3% Zr, 3.3% Hf, 4.5% Cr, 5% Mn, 6% Ni, 7% Ta, 3.5% Ge, 1.5% Sn, 1% Sb, 5% Bi, 5.2% Mo, 9% Nb, 5% Al, 5.5% V, and 5% W, ______________________________________ provided that, when two or more additional elements M are included, the sum of M is no more than the maximum atomic percentage among those specified above of said elements M actually added, said magnet having a tetragonal Fe-B-R crystal structure phase of at least 50 vol % of the entire magnet, and having a maximum energy product of at least 25 MGOe and an intrinsic coercive force of at least 13 kOe.

Claim 5

A permanent magnet as defined in claim 1 or 2, wherein by atomic percent, R 1 is 0.2-3%, R is 13-19%, and B is 5-11%.

Claim 6

A permanent magnet as defined in claim 1 or 2, wherein R 1 comprises at least one of Dy and Tb.

Claim 7

A permanent as defined in claim 1 or 2, wherein R 1 is Dy.

Claim 8

A permanent magnet as defined in claim 1 or 2, wherein R 1 is about 0.4 atomic percent.

Claim 9

A permanent magnet as defined in claim 1 or 2, wherein R 1 is about 1.5 atomic percent.

Claim 10

A permanent magnet as defined in claim 2, wherein the additional elements M comprises one or more selected from the group consisting of V, Nb, Ta, Mo, W, Cr and Al.

Claim 11

A permanent magnet as defined in claim 8, wherein M is no more than about 2 atomic percent.

Claim 12

A permanent magnet as defined in claim 1 or 2, which has been sintered at a temperature between 900° and 1200° C.

Claim 13

A permanent magnet as defined in claim 3, which has a maximum energy product of at least 30 MGOe.

Claim 14

A permanent magnet as defined in claim 11, which has a maximum energy product of at least 33 MGOe.

Claim 15

A permanent magnet as defined in claim 6, which has a maximum energy product of at least 33 MGOe.

Claim 16

A permanent magnet as defined in claim 13, which has a maximum energy product of at least 35 MGOe.

Claim 17

A permanent magnet as defined in claim 1 or 2, which has an intrinsic coercivity of at least 15 kOe.

Claim 18

A permanent magnet as defined in claim 15, which has an intrinsic coercivity of at least 17 kOe.

Claim 19

A permanent magnet as defined in claim 7, which has an intrinsic coercivity of at least 15 kOe.

Claim 20

A permanent magnet as defined in claim 17, which has an intrinsic coercivity of at least 17 kOe.

Claim 21

A permanent magnet as defined in claim 1 or 2, wherein R 2 is at least one of Nd and Pr.

Claim 22

A permanent magnet as defined in claim 1 or claim 2, which has been subjected to aging after sintering at a temperature between 350° C. and 900° C.

Claim 23

A permanent magnet as defined in claim 20, which has been subjected to aging at a temperature of no higher than 800° C.

Claim 24

A permanent magnet as defined in claim 20, which has been subjected to aging at a temperature of at least 450°.

Claim 25

A permanent magnet as defined in claim 1 or 2, wherein R 1 is Tb.

Claim 26

A permanent magnet as defined in claim 1 or 2, wherein R 1 is Ho.

Claim 27

A permanent magnet as defined in claim 1 or 2, which is substantially Co-free.

Claim 28

A permanent magnet as defined in claim 1 or 2, wherein R 2 is Nd.