Process for producing the rare earth alloy powders

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.sub.1 is 0.05 to 5 at %, 4 to 20% B, and 60 to 83.5 at % Fe,
• wherein R.sub.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.sub.2 consists of Nd and/or Pr, the balance in the R.sub.2 being at least one element selected from the group consisting of rare earth elements including Y and except for R.sub.1, and R=R.sub.1 +R.sub.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.degree. to 1200.degree. 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.

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.sub.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.sub.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.sub.2 consists of Nd and/or Pr, the balance in the R.sub.2 being at least one element selected from the group consisting of rare earth elements including Y and except for R.sub.1, and R=R.sub.1 +R.sub.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.degree. to 1200.degree. 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.

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.sub.1 is 0.05 to 5 at %, 4 to 20 at % B, and 60 to 83.5 at % Fe,
• wherein R.sub.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.sub.2 consists of Nd and/or Pr, the balance in the R.sub.2 being at least one element selected from the group consisting of rare earth elements including Y and except for R.sub.1, and R=R.sub.1 +R.sub.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.degree. to 1200.degree. 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.

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.sub.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.sub.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.sub.2 consists of Nd and/or Pr, the balance in the R.sub.2 being at least one element selected from the group consisting of rare earth elements including Y and except for R.sub.1, and R=R.sub.1 +R.sub.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.degree. to 1200.degree. 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.