Method for producing R-Fe-B-based, sintered magnet

A method for producing an R-Fe-B-based, sintered magnet, wherein R is one or more of rare earth elements including Y, comprising the steps of:

• mixing fine R-Fe-B-based magnet powder with a mineral oil and/or a synthetic oil to prepare a mixture, wherein the mineral oil and the synthetic oil, used alone or in combination, have a fractional distillation temperature range of 150.degree.-400.degree. C. and a kinetic viscosity of 10 cSt or less at room temperature;
• charging said mixture into a die cavity under pressure so as to have a filling density of 1.8 g/cm.sup.3 or more while applying an oriented magnetic field to said die cavity;
• subjecting said mixture to a wet molding while orienting said powder to prepare a green body;
• and then
• sintering said green body.

A method for producing an R-Fe-B-based, sintered magnet, wherein R is one or more of rare earth elements including Y, comprising the steps of:

• finely pulverizing an R-Fe-B-based magnet material in an inert gas atmosphere to prepare fine R-Fe-B-based magnet powder in a dry state;
• introducing said fine R-Fe-B-based magnet powder into a mineral oil and/or a synthetic oil in an inert gas atmosphere to prepare a mixture, wherein the mineral oil and the synthetic oil, used alone or in combination, have a fractional distillation temperature range of 150.degree.-400.degree. C. and a kinetic viscosity of 10 cSt or less at room temperature;
• charging said mixture into a die cavity under pressure so as to have a filling density of 1.8 g/cm.sup.3 or more while applying an oriented magnetic field to said die cavity;
• subjecting said mixture to a wet molding while orienting said powder to prepare a green body;
• and then
• sintering said green body.

A method for producing an R-Fe-B-based, sintered magnet, wherein R is one or more of rare earth elements including Y, comprising the steps of mixing fine R-Fe-B-based magnet powder with a mineral oil and/or a synthetic oil having a fractional distillation temperature range of 150.degree.-400.degree. C. and a kinetic viscosity of 10 cSt or less to prepare a mixture;

• charging said mixture under pressure so as to have a filling density of 1.8 g/cm.sup.3 or more into a die cavity equipped with a filter while removing said mineral oil and/or said synthetic oil from said mixture;
• compressing said mixture in said die cavity to carry out a wet molding for preparing a green body;
• heating said green body to a temperature up to 500.degree. C. at a temperature-elevating speed of 10.degree. C./min or less under pressure of 10.sup.-1 Torr or less for 30 minutes or more to remove said mineral oil and/or said synthetic oil from said green body;
• and then sintering said green body.

A method for producing an R-Fe-B-based, sintered magnet, wherein R is one or more of rare earth elements including Y, comprising the steps of mixing fine R-Fe-B-based magnet powder with a mineral oil and/or a synthetic oil having a fractional distillation temperature range of 150.degree.-400.degree. C. and a kinetic viscosity of 10 cSt or less to prepare a mixture;

• charging said mixture under pressure so as to have a filling density of 1.8 g/cm.sup.3 or more into a die cavity equipped with a filter, to which an orientated magnetic field is applied, while removing said mineral oil and/or said synthetic oil from said mixture;
• compressing said mixture in said die cavity to carry out a wet molding while orientating said powder to prepare a green body;
• heating said green body to a temperature up to 500.degree. C. at a temperature-elevating speed of 10.degree. C./min or less under pressure of 10.sup.-1 Torr or less for 30 minutes or more to remove said mineral oil and/or said synthetic oil from said green body;
• and then sintering said green body.

A method for producing as R-Fe-B-based, sintered magnet, wherein R is one or more of rare earth elements including Y, comprising the steps of finely pulverizing an R-Fe-B-based magnet material in an inert gas atmosphere to prepare fine R-Fe-B-based magnet powder in a dry state;

• introducing said fine R-Fe-B-based magnet powder in an inert gas atmosphere into a mineral oil and/or a synthetic oil having a fractional distillation temperature range of 150.degree.-400.degree. C. and a kinetic viscosity of 10 cSt or less;
• mixing said fine R-Fe-B-based magnet powder with said mineral oil and/or said synthetic oil to prepare a mixture;
• charging said mixture under pressure so as to have a filling density of 1.8 g/cm.sup.3 or more into a die cavity equipped with a filter, to which an orientated magnetic field is applied, while removing said mineral oil and/or said synthetic oil from said mixture;
• compressing said mixture in said die cavity to carry out a wet molding while orientating said powder to prepare a green body;
• heating said green body to a temperature up to 500.degree. C. at a temperature-elevating speed of 10.degree. C./min or less under pressure of 10.sup.-1 Torr or less for 30 minutes or more to remove said mineral oil and/or said synthetic oil from said green body;
• and then sintering said green body.