Isotropic magnets and process for producing same

Claim 2

A powder metallurgically sintered, isotropic permanent magnet having a mean crystal grain size of 1-80 microns and consisting essentially of, by atomic percent, 12-20 percent R wherein R is at least one element selected from the group consisting of Nd, Pr, La, Ce, Tb, Dy, Ho, Er, Eu, Sm, Gd, Pm, Tm, Yb, Lu and Y and wherein at least 50% of R consists of Nd and/or Pr, 5-18 percent B, and at least 62 percent Fe in which Fe amount Co is substituted for Fe in an amount greater than zero and not exceeding 25 percent of the magnet and at least 50 vol % of the entire magnet is occupied by a ferromagnetic compound having a an (Fe,Co)-B-R-type tetragonal crystal structure which has a higher Curie temperature than a corresponding ferromagnetic Fe-B-R base compound containing no Co, the magnet having a maximum energy product of at least 4 MGOe and an intrinsic coercivity of at least 1 kOe.

Claim 3

A powder metallurgically sintered, isotropic permanent magnet having a mean crystal grain size of 1-80 microns and consisting essentially of, by atomic percent, 12-20 percent R wherein R is at least one element selected from the group consisting of Nd, Pr, La, Ce, Tb, Dy, Ho, Er, Eu, Sm, Gd, Pm, Tm, Yb, Lu and Y and wherein at least 50% of R consists of Nd and/or Pr, 5-18 percent B, at least one additional element M selected from the group given below in the amounts not exceeding the atomic percentages specified below, wherein the sum of M does not exceed the maximum value of any one of the values specified below for M actually added and at least 62 percent Fe in which Fe amount Co is substituted for Fe in an amount greater than zero and not exceeding 25 percent on the magnet: ______________________________________ 7.3% Al, 3.6% Ti, 7.3% V, 6.8% Cr, 6.6% Mn, 4.4% Zr, 4.2% Hf, 9.5% Nb, 8.2% Ta, 7.5% Mo, 4.7% Ge, 1.9% Sb, 3.0% Sn, 3.8% Bi, 3.6% Ni, and 7.9% W, ______________________________________ in which a ferromagnetic compound having a an (Fe,Co)-B-R type tetragonal crystal structure and having a higher Curie temperature than a corresponding ferromagnetic Fe-B-R base compound containing no Co occupies at least 50 vol % of the entire magnet, said permanent magnet having a maximum energy product of at least 4 MGOe and an intrinsic coercivity of at least 1 kOe.

Claim 4

A powder metallurgically sintered, isotropic permanent magnet having a mean crystal grain size of 1-80 microns and consisting essentially of, by atomic percent, 12-20 percent R wherein R is at least one element selected from the group consisting of Nd, Pr, La, Ce, Tb, Dy, Ho, Er, Eu, Sm, Gd, Pm, Tm, Yb, Lu and Y and wherein at least 50% of R consists of Nd and/or Pr, 5-18 percent B, at least one additional element M selected from the group given below in the amounts not exceeding the atomic percentages specified below, wherein the sum of M does not exceed the maximum value of any one of the values specified below for M actually added and at least 62 percent Fe in which Fe amount Co is substituted for Fe in an amount greater than zero and not exceeding 25 percent on the magnet: ______________________________________ 7.3% Al, 3.6% Ti, 7.3% V, 6.8% Cr, 6.6% Mn, 4.4% Zr, 4.2% Hf, 9.5% Nb, 8.2% Ta, 7.5% Mo, 4.7% Ge, 1.9% Sb, 3.0% Sn, 3.8% Bi, 3.6% Ni, and 7.9% W, ______________________________________ in which a ferromagnetic compound having a an (Fe,Co)-B-R type tetragonal crystal structure and having a higher Curie temperature than a corresponding ferromagnetic Fe-B-R base compound containing no Co occupies at least 50 vol % of the entire magnet, said permanent magnet having a maximum energy product of at least 4 MGOe and an intrinsic coercivity of at least 1 kOe.

Claim 5

A magnet as defined in claim 1 or 2, in which Co is at least 0.1 atomic %.

Claim 6

A magnet as defined in claim 1 or 2, in which Co is at least 5 atomic %.

Claim 7

A magnet as defined in claim 1 or 2, in which Co does not exceed 15 atomic %.

Claim 8

A magnet as defined in claim 1 or 2, in which R is about 15 atomic %, and B is about 8 atomic %.

Claim 9

A magnet as defined in claim 1 or 2, in which Si is present in an amount not exceeding 5 atomic %.

Claim 10

A magnet as defined in claim 1, in which the sintered magnet has a mean crystal grain size of 3-30 microns.

Claim 11

A magnet as defined in claim 2, in which the sintered magnet has a mean crystal grain size of 2-40 microns.

Claim 12

A magnet as defined in claim 9, in which the sintered magnet has a mean crystal grain size of 3-15 microns.

Claim 13

A magnet as defined in claim 1 or 2, which contains 1 vol % or higher of a rare earth rich phase.

Claim 14

A magnet as defined in claim 2, in which M is at least one additional element selected from the group consisting of V, Nb, Ta, Mo, Cr and Al.

Claim 15

A magnet as defined in claim 1, in which, by atomic percent, R is 12-16 percent, B is 6-18 percent, and Fe is at least 66 percent.

Claim 16

A magnet as defined in claim 2, in which by atomic percent, R is 12-16 percent, B is 6-18 percent, Fe is at least 66 percent, and the additional element M is at least one selected from the group given below in the amounts not exceeding the atomic percentages specified below, wherein the sum of M is not exceeding the maximum value of any one of the values specified below for M actually added: ______________________________________ 2.0% Al, 1.0% Ti, 2.0% V, 1.4% Cr, 1.7% Mn, 1.1% Zr, 0.9% Hf, 1.7% Nb, 1.7% Ta, 2.2% Mo, 1.3% Ge, 0.3% Sb, 0.5% Sn, 0.7% Bi, 1.0% Ni, and 3.0% W. ______________________________________

Claim 17

A magnet as defined in claim 13 or 14, which has a maximum energy product of at least 5 MGOe.

Claim 18

A magnet as defined in claim 1 or 2, which has a magnetic resonance of at least 4 kG.

Claim 19

A magnet as defined in claim 13 or 14, which has a magnetic remanence of at least 5 kG.

Claim 20

A magnet as defined in in claim 15, which has a magnetic remanence of at least 5.8 kG.

Claim 21

A magnet as defined in claim 15, which has a maximum energy product of at least 6 MGOe.

Claim 22

A magnet as defined in claim 19, which has a magnetic remanence of at least 6 kG.

Claim 23

A magnet as defined in claim 19, which has a maximum energy product of at least 7 MGOe.

Claim 24

A magnet as defined in claim 1 or 2, in which said tetragonal crystal structure has lattice parameters Ao of about 8.8 angstroms and Co of about 12.2 angstroms.

Claim 25

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