Process for production of permanent magnet alloy having improved resistence to oxidation

In a process for producing a permanent magnet alloy based on an R--Fe--B--C system where R is at least one of the rare earth elements including Y, comprising the steps of preparing a molten crude alloy, producing a powder directly therefrom or by casting it into an alloy ingot and then grinding it into the powder, compacting the thus obtained powder and sintering the compacted product, the improvement comprising part or all of a C source material being added to a raw material mixture in a step which is after said step of preparing a molten crude alloy, but before said step of compacting the powder so as to produce a permanent magnet alloy based on a R--Fe--B--C system whose individual magnetic crystal grains are covered with an oxidation-resistant protective film which has a C content of 0.05-16 wt % and higher than that of said individual crystal grains and wherein the composition of said magnet alloy as the sum of the magnetic crystal grains and the oxidation-resistant protective film comprises 10-30% R, less than 2%, not inclusive of zero percent, of B, 0.1-20% C, all percentages being on an atomic basis, with the balance being Fe and incidental impurities.

In a process for producing a permanent magnet alloy based on a R--Fe--B--C system where R is at least one of the rare earth elements including Y, comprising the steps of preparing a molten crude alloy, producing a powder directly therefrom or by casting it into an alloy ingot and then grinding it into the powder, compacting the thus obtained powder and sintering the compacted product, the improvement comprising part or all of a C source material being added to the raw material mixture in a step which is after said step of preparing a molten crude alloy, but before said step of compacting the powder, and in that the alloy ingot or powder in a step before said compacting step being subjected to a heat treatment which is carried out at a temperature of 500.degree.-1,100.degree. C. for a period of up to 24 hours so as to produce a permanent magnet alloy based on a R--Fe--B--C system whose individual magnetic crystal grains are covered with an oxidation-resistant protective film which has a C content of 0.05 to 16 wt % and higher than that of said individual crystal grains and wherein the composition of said magnet alloy as the sum of the magnetic crystal grains and the oxidation-resistant protective film comprises 10-30% R, less than 2%, not inclusive of zero percent, of B, 0.1-20% C, all percentages being on an atomic basis, with the balance being Fe and incidental impurities.

In a process for producing a permanent magnet alloy based on a R--Fe--Co--B--C system where R is at least one of the rare earth elements including Y, comprising the steps of preparing a molten crude alloy, producing a powder directly therefrom or by casting it into an alloy ingot and then grinding it into the powder, compacting the thus obtained powder and sintering the compacted product, the improvement comprising the ingot or powder of the alloy before being sent to the compacting step being subjected to a heat treatment which is carried out at a temperature of 500.degree.-1,100.degree. C. for a period of up to 24 hours so as to produce a permanent magnet alloy based on a R--Fe--Co--B--C system whose individual magnetic crystal grains are covered with an oxidation-resistant protective film which has the C content of 0.05-16 wt % and higher than that of said individual crystal grains and wherein the composition of said magnet alloy comprises 10-30% R, less than 2%, not inclusive of 0 atom %, of B, 0.1-20% C, up to 40%, not inclusive of 0 atom %, of Co, all percentages being on an atomic basis, with the balance being Fe and incidental impurities.

In a process for producing a permanent magnet alloy based on a R--Fe--Co--B--C system where R is at least one of the rare earth elements including Y, comprising the steps of preparing a molten crude alloy, producing a powder directly therefrom or by casting it into an alloy ingot and then grinding it into the powder, compacting the thus obtained powder and sintering the compacted product, the improvement comprising part or all of a C source material and/or Co source material being added to a raw material mixture in a step which is after said step of preparing a molten crude alloy, but before said step of compacting the powder so as to produce a permanent magnet alloy based on a R--Fe--Co--B--C system whose individual magnetic crystal grains are covered with an oxidation resistant protective film which has a C content of 0.05 to 16 wt % and higher than that of said individual crystal grains and wherein the composition of said magnet alloy comprises 10-30% R, less than 2%, not inclusive of 0 atom %, of B, 0.1-20% C, up to 40%, not inclusive of 0 atom %, of Co, all percentages being on an atomic basis, with the balance being Fe and incidental impurities.

In a process for producing a permanent magnet alloy based on a R--Fe--B--C system where R is at least one of the rare earth elements including Y, comprising the steps of preparing a molten crude alloy, producing a powder directly therefrom or by casting it into an alloy ingot and then grinding it into the powder, compacting the thus obtained powder and sintering the compacted product, the improvement comprising the ingot or powder of the alloy before being sent to the compacting step being subjected to a heat treatment which is carried out at a temperature of 500.degree.-1,100.degree. C. for a period of up to 24 hours so as to produce a permanent magnet alloy based on a R--Fe--B--C system whose individual magnetic crystal grains are covered with an oxidation-resistant protective film which has a C content of 0.05-16 wt % and higher than that of said individual crystal grains and wherein the composition of said magnet alloy as the sum of the magnetic crystal grains and the oxidation-resistant protective film comprises 10-30% R, less than 4%, not inclusive of zero percent, of B, 0.1-20% C, all percentages being on an atomic basis, with the balance being Fe and incidental impurities.

In a process for producing a permanent magnet alloy based on an R--Fe--B--C system where R is at least one of the rare earth elements including Y, comprising the steps of preparing a molten crude alloy, producing a powder directly therefrom or by casting it into an alloy ingot and then grinding it into the powder, compacting the thus obtained powder and sintering the compacted product, the improvement comprising part or all of a C source material being added to a raw material mixture in a step which is after said step of preparing a molten crude alloy, but before said step of compacting the powder so as to produce a permanent magnet alloy based on a R--Fe--B--C system whose individual magnetic crystal grains are covered with an oxidation-resistant protective film which has a C content of 0.05-16 wt % and higher than that of said individual crystal grains and wherein the composition of said magnet alloy as the sum of the magnetic crystal grains and the oxidation-resistant protective film comprises 10-30% R, less than 4%, not inclusive of zero percent, of B, 0.1-20% C, all percentages being on an atomic basis, with the balance being Fe and incidental impurities.

In a process for producing a permanent magnet alloy based on a R--Fe--B--C system where R is at least one of the rare earth elements including Y, comprising the steps of preparing a molten crude alloy, producing a powder directly therefrom or by casting it into an alloy ingot and then grinding it into the powder, compacting the thus obtained powder and sintering the compacted product, the improvement comprising part or all of a C source material being added to the raw material mixture in a step which is after said step of preparing a molten crude alloy, but before said step of compacting the powder, and in that the alloy ingot or powder in a step before said compacting step being subjected to a heat treatment which is carried out at a temperature of 500.degree.-1,100.degree. C. for a period of up to 24 hours so as to produce a permanent magnet alloy based on a R--Fe--B--C system whose individual magnetic crystal grains are covered with an oxidation-resistant protective film which has a C content of 0.05 to 16 wt % and higher than that of said individual crystal grains and wherein the composition of said magnet alloy as the sum of the magnetic crystal grains and the oxidation-resistant protective film comprises 10-30% R, less than 4%, not inclusive of zero percent, of B, 0.1-20% C, all percentages being on an atomic basis, with the balance being Fe and incidental impurities.

In a process for producing a permanent magnet alloy based on a R--Fe--Co--B--C system where R is at least one of the rare earth elements including Y, comprising the steps of preparing a molten crude alloy, producing a powder directly therefrom or by casting it into an alloy ingot and then grinding it into the powder, compacting the thus obtained powder and sintering the compacted product, the improvement comprising the ingot or powder of the alloy before being sent to the compacting step being subjected to a heat treatment which is carried out at a temperature of 500.degree.-1,100.degree. C. for a period of up to 24 hours so as to produce a permanent magnet alloy based on a R--Fe--Co--B--C system whose individual magnetic crystal grains are covered with an oxidation-resistant protective film which has the C content of 0.05-16 wt % and higher than that of said individual crystal grains and wherein the composition of said magnet alloy comprises 10-30% R, less than 4%, not inclusive of 0 atom %, of B, 0.1-20% C, up to 40%, not inclusive of 0 atom %, of Co, all percentages being on an atomic basis, with the balance being Fe and incidental impurities.

In a process for producing a permanent magnet alloy based on a R--Fe--Co--B--C system where R is at least one of the rare earth elements including Y, comprising the steps of preparing a molten crude alloy, producing a powder directly therefrom or by casting it into an alloy ingot and then grinding it into the powder, compacting the thus obtained powder and sintering the compacted product, the improvement comprising part or all of a C source material and/or Co source material being added to a raw material mixture in a step which is after said step of preparing a molten crude alloy, but before said step of compacting the powder so as to produce a permanent magnet alloy based on a R--Fe--Co--B--C system whose individual magnetic crystal grains are covered with an oxidation resistant protective film which has a C content of 0.05 to 16 wt % and higher than that of said individual crystal grains and wherein the composition of said magnet alloy comprises 10-30% R, less than 4%, not inclusive of 0 atom %, of B, 0.1-20% C, up to 40%, not inclusive of 0 atom %, of Co, all percentages being on an atomic basis, with the balance being Fe and incidental impurities.