Process for producing the rare earth alloy powders

Claim 2

A rare earth-iron-boron alloy powder which consists essentially of: 12.5 to 20 at % R wherein R 1 is 0.05 to 5 at %, 4 to 20 at % B, and 60 to 83.5 at % Fe, wherein R 1 is at least one heavy rare earth element selected from the group consisting of Gd, Tb, Dy, Ho, Er, Tm and Yb, 80 to 100 at % of R 2 consists of Nd and/or Pr, the balance in the R 2 being at least one element selected from the group consisting of rare earth elements including Y and except for R 1 , and R=R 1 +R 2 by atomic %, wherein a major phase of at least 80 vol % of the entire alloy consists of a tetragonal structure, and wherein oxygen does not exceed 10,000 ppm, carbon does not exceed 1000 ppm and calcium does not exceed 2000 ppm.

Claim 3

A rare earth-iron-cobalt-boron alloy powder which consists essentially of: 12.5 to 20 at % R wherein R 1 is 0.05 to 5 at %, 4 to 20 at % B, 45 to 82 at % Fe, and more than zero and up to 35 at % Co, wherein R 1 is at least one heavy rare earth element selected from the group consisting of Gd, Tb, Dy, Ho, Er, Tm and Yb, 80 to 100 wt % of R 2 consists of Nd and/or Pr, the balance in the R 2 being at least one element selected from the group consisting of rare earth elements including Y and except for R 1 , and R=R 1 +R 2 by atomic %, and wherein a major phase of at least 80 vol % of the entire alloy consists of a tetragonal structure, and wherein oxygen does not exceed 10,000 ppm, carbon does not exceed 1000 ppm and calcium does not exceed 2000 ppm.

Claim 4

A rare earth-iron-cobalt-boron alloy powder which consists essentially of: 12.5 to 20 at % R wherein R 1 is 0.05 to 5 at %, 4 to 20 at % B, 45 to 82 at % Fe, and more than zero and up to 35 at % Co, wherein R 1 is at least one heavy rare earth element selected from the group consisting of Gd, Tb, Dy, Ho, Er, Tm and Yb, 80 to 100 wt % of R 2 consists of Nd and/or Pr, the balance in the R 2 being at least one element selected from the group consisting of rare earth elements including Y and except for R 1 , and R=R 1 +R 2 by atomic %, and wherein a major phase of at least 80 vol % of the entire alloy consists of a tetragonal structure, and wherein oxygen does not exceed 10,000 ppm, carbon does not exceed 1000 ppm and calcium does not exceed 2000 ppm.

Claim 5

An alloy powder as defined in claim 1 or 2, wherein at least one additional element M selected from the group consisting of the following elements in amounts not exceeding the values specified below is included in place of a part of said Fe: 5.0 at % Al, 3.0 at % Ti, 5.5 at % V, 6.0 at % Ni, 4.5 at % Cr, 5.0 at % Mn, 5.0 at % Bi, 9.0 at % Nb, 7.0 at % Ta, 5.2 at % Mo, 5.0 at % W, 1.0 at % Sb, 3.5 at % Ge, 1.5 at % Sn, 3.3 at % Zr, 3.3 at % Hf, and 5.0 at % Si.

Claim 6

An alloy powder as defined in claim 1, wherein the lattice parameters of said tetragonal crystal are a of about 8.8 Å and c of about 12.2 Å, and the central composition thereof is R 2 Fe 14 B.

Claim 7

An alloy powder as defined in claim 2, wherein the lattice parameters of said tetragonal crystal are a of about 8.8 Å and c of about 12.2 Å, and the central composition thereof is R 2 (Fe,Co) 14 B.

Claim 8

An alloy powder as defined in claim 1 or 2, which is capable of providing a magnetically anisotropic sintered magnet having a maximum energy product of at least 20 MGOe and a coercive force of at least 10 kOe.

Claim 9

An alloy powder as defined in claim 2, wherein Co is 0.1 to 25 at %.

Claim 10

An alloy powder as defined in claim 2, wherein Co is at least 5 at %.

Claim 11

An alloy powder as defined in claim 1, wherein Co is about 5-about 6 at %.

Claim 12

An alloy powder as defined in claim 1 or 2, wherein oxygen does not exceed 6000 ppm.

Claim 13

An alloy powder which is capable of providing a magnetically anisotropic sintered magnet having a maximum energy product of at least 20 MGOe and a coercive force of at least 10 KOe, which is the product of the process comprising the steps of: providing a starting mixed powdery material by formulating at least one rare earth oxide of the rare earth elements specified below, an iron powder and at least one powder selected from the group consisting of a boron powder, a ferroboron powder and a boron oxide powder in such a manner that the resulting alloy has an alloy composition consisting essentially of: 12.5 to 20 at % R wherein R 1 is 0.05 to 5 at %, 4 to 20% B, and 60 to 83.5 at % Fe, wherein R 1 is at least one heavy rare earth element selected from the group consisting of Gd, Tb, Dy, Ho, Er, Tm and Yb, 80 to 100 at % of the R 2 consists of Nd and/or Pr, the balance in the R 2 being at least one element selected from the group consisting of rare earth elements including Y and except for R 1 , and R=R 1 +R 2 by atomic %; mixing said starting mixed powdery material with metallic calcium and/or calcium hydride in an amount of 1.2 to 3.5 times by weight of the stoichiometric amount required for reduction with respect to the amount of oxygen contained in said starting mixed powdery material, and with calcium chloride in an amount of 1 to 15% by weight of said rare earth oxides; reducing the resulting mixture at a temperature of 950° to 1200° C. in an inert atmosphere; putting the resultant reaction product into water to provide a sluried state, and treating the resultant slurry with water by stirring the slurry and removing water to recover a resultant alloy powder having a major phase of a tetragonal structure amounting to at least 80 vol % of the entire alloy until the alloy powder reaches a calcium content not exceeding 2000 ppm.

Claim 14

An alloy powder which is capable of providing a magnetically anisotropic sintered magnet having a maximum energy product of at least 20 MGOe and a coercive force of at least 10 KOe, which is the product of the process comprising the steps of: providing a starting mixed powdery material by formulating at least one rare earth oxide of the rare earth elements specified below, an iron powder and at least one powder selected from the group consisting of a boron powder, a ferroboron powder and a boron oxide powder in such a manner that the resulting alloy has an alloy composition consisting essentially of: 12.5 to 20 at % R wherein R 1 is 0.05 to 5 at %, 4 to 20% B, and 60 to 83.5 at % Fe, wherein R 1 is at least one heavy rare earth element selected from the group consisting of Gd, Tb, Dy, Ho, Er, Tm and Yb, 80 to 100 at % of the R 2 consists of Nd and/or Pr, the balance in the R 2 being at least one element selected from the group consisting of rare earth elements including Y and except for R 1 , and R=R 1 +R 2 by atomic %; mixing said starting mixed powdery material with metallic calcium and/or calcium hydride in an amount of 1.2 to 3.5 times by weight of the stoichiometric amount required for reduction with respect to the amount of oxygen contained in said starting mixed powdery material, and with calcium chloride in an amount of 1 to 15% by weight of said rare earth oxides; reducing the resulting mixture at a temperature of 950° to 1200° C. in an inert atmosphere; putting the resultant reaction product into water to provide a sluried state, and treating the resultant slurry with water by stirring the slurry and removing water to recover a resultant alloy powder having a major phase of a tetragonal structure amounting to at least 80 vol % of the entire alloy until the alloy powder reaches a calcium content not exceeding 2000 ppm.

Claim 15

An alloy powder which is capable of providing a magnetically anisotropic sintered magnet having a maximum energy product of at least 20 MGOe and a coercive force of at least 10 KOe, which is the product of the process comprising the steps of: providing a starting mixed powdery material by formulating at least one rare earth oxide of the rare earth elements specified below, an iron powder, a cobalt powder and at least one powder selected from the group consisting of a boron powder, a ferroboron powder and a boron oxide powder in such a manner that the resulting alloy has a composition consisting essentially of: 12.5 to 20% R wherein R 1 is 0.05 to 5 at %, 4 to 20 at % B, more than zero and up to 35 at % Co, and 45 to 82 at % Fe, wherein R 1 is at least one heavy rare earth element selected from the group consisting of Gd, Tb, Dy, Ho, Er, Tm and Yb, 80 to 100% R 2 consists of Nd and/or Pr, the balance in the R 2 being at least one element selected from the group consisting of rare earth elements including Y and except for R 1 , and R=R 1 +R 2 by atomic %; mixing said starting mixed powdery material with metallic calcium and/or Ca hydride in an amount of 1.2 to 3.5 times by weight ratio of the stoichiometric amount required for reduction with respect to the amount of oxygen contained in said starting mixed powdery material, and with calcium chloride in an amount of 1 to 15% by weight of said rare earth oxides, reducing the resulting mixture at a temperature of 950° to 1200° C. in an inert atmosphere, putting the resultant reaction product into water to provide a sluried state, and treating the resultant slurry with water by stirring the slurry and removing water to recover a resultant alloy powder having a major phase of a tetragonal structure amounting to at least 80 vol % of the entire alloy until the alloy powder reaches a calcium content not exceeding 2000 ppm.

Claim 16

An alloy powder which is capable of providing a magnetically anisotropic sintered magnet having a maximum energy product of at least 20 MGOe and a coercive force of at least 10 KOe, which is the product of the process comprising the steps of: providing a starting mixed powdery material by formulating at least one rare earth oxide of the rare earth elements specified below, an iron powder, a cobalt powder and at least one powder selected from the group consisting of a boron powder, a ferroboron powder and a boron oxide powder in such a manner that the resulting alloy has a composition consisting essentially of: 12.5 to 20% R wherein R 1 is 0.05 to 5 at %, 4 to 20 at % B, more than zero and up to 35 at % Co, and 45 to 82 at % Fe, wherein R 1 is at least one heavy rare earth element selected from the group consisting of Gd, Tb, Dy, Ho, Er, Tm and Yb, 80 to 100% R 2 consists of Nd and/or Pr, the balance in the R 2 being at least one element selected from the group consisting of rare earth elements including Y and except for R 1 , and R=R 1 +R 2 by atomic %; mixing said starting mixed powdery material with metallic calcium and/or Ca hydride in an amount of 1.2 to 3.5 times by weight ratio of the stoichiometric amount required for reduction with respect to the amount of oxygen contained in said starting mixed powdery material, and with calcium chloride in an amount of 1 to 15% by weight of said rare earth oxides, reducing the resulting mixture at a temperature of 950° to 1200° C. in an inert atmosphere, putting the resultant reaction product into water to provide a sluried state, and treating the resultant slurry with water by stirring the slurry and removing water to recover a resultant alloy powder having a major phase of a tetragonal structure amounting to at least 80 vol % of the entire alloy until the alloy powder reaches a calcium content not exceeding 2000 ppm.

Claim 17

An anisotropic sintered magnet which has a maximum energy product of at least 20 MGOe and a coercive force of at least 10 KOe which is obtained by compacting in a magnetic field and sintering the product of the process comprising the steps of: providing a starting mixed powdery material by formulating at least one rare earth oxide of the rare earth elements specified below, an iron powder and at least one powder selected from the group consisting of a boron powder, a ferroboron powder and a boron oxide powder in such a manner that the resulting alloy has an alloy composition consisting essentially of: 12.5 to 20 at % R wherein R 1 is 0.05 to 5 at %, 4 to 20 at % B, and 60 to 83.5 at % Fe, wherein R 1 is at least one heavy rare earth element selected from the group consisting of Gd, Tb, Dy, Ho, Er, Tm and Yb, 80 to 100 at % of the R 2 consists of Nd and/or Pr, the balance in the R 2 being at least one element selected from the group consisting of rare earth elements including Y and except for R 1 , and R=R 1 +R 2 by atomic %; mixing said starting mixed powdery material with metallic calcium and/or calcium hydride in an amount of 1.2 to 3.5 times by weight of the stoichiometric amount required for reduction with respect to the amount of oxygen contained in said starting mixed powdery material, and with calcium chloride in an amount of 1 to 15% by weight of said rare earth oxides; reducing the resulting mixture at a temperature of 950° to 1200° C. in an inert atmosphere; putting the resultant reaction product into water to provide a sluried state, and treating the resultant slurry with water by stirring the slurry and removing water to recover a resultant alloy powder having a major phase of a tetragonal structure amounting to at least 80 vol % of the entire alloy until the alloy powder reaches a calcium content not exceeding 2000 ppm.

Claim 18

An anisotropic sintered magnet which has a maximum energy product of at least 20 MGOe and a coercive force of at least 10 KOe which is obtained by compacting in a magnetic field and sintering the product of the process comprising the steps of: providing a starting mixed powdery material by formulating at least one rare earth oxide of the rare earth elements specified below, an iron powder and at least one powder selected from the group consisting of a boron powder, a ferroboron powder and a boron oxide powder in such a manner that the resulting alloy has an alloy composition consisting essentially of: 12.5 to 20 at % R wherein R 1 is 0.05 to 5 at %, 4 to 20 at % B, and 60 to 83.5 at % Fe, wherein R 1 is at least one heavy rare earth element selected from the group consisting of Gd, Tb, Dy, Ho, Er, Tm and Yb, 80 to 100 at % of the R 2 consists of Nd and/or Pr, the balance in the R 2 being at least one element selected from the group consisting of rare earth elements including Y and except for R 1 , and R=R 1 +R 2 by atomic %; mixing said starting mixed powdery material with metallic calcium and/or calcium hydride in an amount of 1.2 to 3.5 times by weight of the stoichiometric amount required for reduction with respect to the amount of oxygen contained in said starting mixed powdery material, and with calcium chloride in an amount of 1 to 15% by weight of said rare earth oxides; reducing the resulting mixture at a temperature of 950° to 1200° C. in an inert atmosphere; putting the resultant reaction product into water to provide a sluried state, and treating the resultant slurry with water by stirring the slurry and removing water to recover a resultant alloy powder having a major phase of a tetragonal structure amounting to at least 80 vol % of the entire alloy until the alloy powder reaches a calcium content not exceeding 2000 ppm.

Claim 19

An anisotropic sintered magnet which has a maximum energy product of at least 20 MGOe and a coercive force of at least 10 KOe which is obtained by compacting in a magnetic field and sintering the product of the process comprising the steps of: providing a starting mixed powdery material by formulating at least one rare earth oxide of the rare earth elements specified below an iron powder, a cobalt powder and at least one powder selected from the group consisting of a boron powder, a ferroboron powder and a boron oxide powder in such a manner that the resulting alloy has a composition consisting essentially of: 12.5 to 20% R wherein R 1 is 0.05 to 5 at %, 4 to 20 at % B, more than zero and up to 35 at % Co, and 45 to 82 at % Fe, wherein R 1 is at least one heavy rare earth element selected from the group consisting of Gd, Tb, Dy, Ho, Er, Tm and Yb, 80 to 100% R 2 consists of Nd and/or Pr, the balance in the R 2 being at least one element selected from the group consisting of rare earth elements including Y and except for R 1 , and R=R 1 +R 2 by atomic %; mixing said starting mixed powdery material with metallic calcium and/or Ca hydride in an amount of 1.2 to 3.5 times by weight ratio of the stoichiometric amount required for reduction with respect to the amount of oxygen contained in said starting mixed powdery material, and with calcium chloride in an amount of 1 to 15% by weight of said rare earth oxides, reducing the resulting mixture at a temperature of 950° to 1200° C. in an inert atmosphere, putting the resultant reaction product into water to provide a sluried state, and treating the resultant slurry with water by stirring the slurry and removing water to recover a resultant alloy powder having a major phase of a tetragonal structure amounting to at least 80 vol % of the entire alloy until the alloy powder reaches a calcium content not exceeding 2000 ppm.

Claim 20

An anisotropic sintered magnet which has a maximum energy product of at least 20 MGOe and a coercive force of at least 10 KOe which is obtained by compacting in a magnetic field and sintering the product of the process comprising the steps of: providing a starting mixed powdery material by formulating at least one rare earth oxide of the rare earth elements specified below an iron powder, a cobalt powder and at least one powder selected from the group consisting of a boron powder, a ferroboron powder and a boron oxide powder in such a manner that the resulting alloy has a composition consisting essentially of: 12.5 to 20% R wherein R 1 is 0.05 to 5 at %, 4 to 20 at % B, more than zero and up to 35 at % Co, and 45 to 82 at % Fe, wherein R 1 is at least one heavy rare earth element selected from the group consisting of Gd, Tb, Dy, Ho, Er, Tm and Yb, 80 to 100% R 2 consists of Nd and/or Pr, the balance in the R 2 being at least one element selected from the group consisting of rare earth elements including Y and except for R 1 , and R=R 1 +R 2 by atomic %; mixing said starting mixed powdery material with metallic calcium and/or Ca hydride in an amount of 1.2 to 3.5 times by weight ratio of the stoichiometric amount required for reduction with respect to the amount of oxygen contained in said starting mixed powdery material, and with calcium chloride in an amount of 1 to 15% by weight of said rare earth oxides, reducing the resulting mixture at a temperature of 950° to 1200° C. in an inert atmosphere, putting the resultant reaction product into water to provide a sluried state, and treating the resultant slurry with water by stirring the slurry and removing water to recover a resultant alloy powder having a major phase of a tetragonal structure amounting to at least 80 vol % of the entire alloy until the alloy powder reaches a calcium content not exceeding 2000 ppm.