JP2004250781A5 - - Google Patents

Description

Sintered permanent magnet and method of manufacturing the same

The present invention relates to a high-performance sintered R-Fe-B-based permanent magnet having an improved coercive force iHc by containing a desired amount of P , and a method for producing the same, particularly excellent in uniformity of surface magnetic flux density. And high performance radial anisotropic sintered R-Fe-B permanent magnets and an efficient method for producing the same.

  R-Fe-B permanent magnets have been produced for a long time by a so-called dry molding method in which a dry fine powder is molded in a mold while applying a magnetic field. In the dry molding method, when a raw material coarse powder is finely pulverized by a jet mill, a small amount of oxygen is introduced into the jet mill, and the oxygen concentration in the nitrogen gas or Ar gas as a grinding medium is controlled to a desired range. . This is to forcibly oxidize the fine powder surface. The fine powder pulverized without the oxidation treatment is ignited upon contact with the atmosphere. The oxygen content of the oxidized fine powder is 5000 to 6000 ppm, and the oxygen content of the sintered body obtained therefrom is 4000 to 5000 ppm. Most of the oxygen in the sintered body combines with rare earth elements such as Nd and exists as oxides at grain boundaries. In order to supplement the oxidized rare earth element, it is necessary to increase the total amount of the rare earth element in the sintered body, but this causes a problem that the saturation magnetic flux density of the sintered magnet decreases.

To solve the problem of the dry molding method, a mixture of rare earth magnet powder and mineral oil or synthetic oil is injected under pressure into a mold cavity to which an orientation magnetic field is applied, and then wet molding in a magnetic field in a low oxygen atmosphere. There has been proposed a method of producing a sintered rare earth magnet by forming a ring-shaped molded body, removing a solvent from the molded body, and performing vacuum sintering (Patent Document 1). This manufacturing method can stably produce a high-performance sintered R-Fe-B permanent magnet having a small total amount of rare earth elements and a small amount of oxygen. However, since the slurry is pressurized and injected into the mold cavity to which the orientation magnetic field is applied, the R-Fe-B-based fine powder having a large spontaneous magnetization receives a large restraining force due to the interaction with the orientation magnetic field, and the powder is injected into the mold cavity. There is a problem that the packing density becomes non-uniform, and as a result, the density of the formed body becomes non-uniform, and the sintered body is deformed and cracks occur. Also, in order to pressurize and inject the slurry from the injection hole opening into the mold cavity toward the center of the core, the slurry that collides with the core and splits in two directions merges with the injection hole on the opposite side at 180 °. There is also a problem that cracks occur in the sintered body from the junction.

Further, a slurry of R-Fe-B-based magnetic powder for permanent magnet and a slurry of mineral oil, synthetic oil or vegetable oil is discharged from a slurry supply pipe inserted into a mold cavity to which a magnetic field is applied, and the slurry supply pipe is gradually discharged. The slurry filled in the cavity is molded under pressure while removing the solvent, the solvent is removed from the obtained ring-shaped molded body, and then sintered to produce a sintered R-Fe-B-based permanent magnet A method has been proposed (Patent Document 2). In this method, since the slurry is discharged into the cavity from a slurry supply pipe inserted deep into the mold cavity, even when a relatively long ring-shaped molded body is molded, the filling property of the slurry into the mold cavity is good, Since the slurry supply pipe is inserted deep into the mold cavity and the slurry supply pipe is pulled out while discharging the slurry, there is a disadvantage that the slurry supply time is long. In addition, the portion where the slurry supply pipe was located remains as a cavity in the compact, which becomes a singular point and causes cracks in the sintered R-Fe-B-based permanent magnet.

Also, as a method of manufacturing a radially anisotropic ring-shaped R-Fe-B-based permanent magnet , a powder obtained by pulverizing a quenched ribbon of an R-Fe-B-based magnet alloy was molded at room temperature and obtained. The compact is hot-pressed in an inert gas atmosphere to densify it, and the resulting hot-pressed body is subjected to hot plastic working to form a cup with magnetic anisotropy in the radial direction. A ring-shaped method has also been proposed (Patent Documents 3 and 4). However, hot plastic working of a hot pressed body in an inert gas atmosphere is performed at a relatively low temperature of about 700 to 800 ° C so as not to coarsen the crystal grains. Need to be done at Although it depends on the size of the magnet, the time required for one hot plastic working is usually 10 to 30 minutes, and the productivity is low as an industrial method for manufacturing permanent magnets. In addition, since the end of the thus-produced pressure-processed body is easily cracked, it is necessary to cut off the cracked portion. For these reasons, this manufacturing method has a high manufacturing cost. Further, the obtained ring-shaped magnet has a large variation in the magnetic characteristics. The degree of the radial anisotropy depends on the deformation amount during hot plastic working, but there is a problem that the dispersion of the surface magnetic flux density becomes large particularly in small-diameter products and long products having large hot plastic working resistance.
JP-A-7-057914 (page 3) JP-A-11-214216 (pages 3 to 5) JP-A-9-275004 (pages 3 to 5) JP-A-2001-181802 (pages 2-3)

Accordingly, an object of the present invention is to provide a high-performance sintered R-Fe-B-based permanent magnet having an improved coercive force iHc by containing a desired amount of P, and in particular, a magnetic orientation without deformation or cracking. It is an object of the present invention to provide a radially anisotropic sintered R-Fe-B permanent magnet which is excellent in quality. Another object of the present invention is to provide a method for producing a radially anisotropic sintered R-Fe-B-based permanent magnet having high magnetic properties and less variation in surface magnetic flux density with high productivity. is there.

Sintered permanent magnet of the present invention, 27 to 33.5% of R (at least one rare earth element R, including a Y) in mass% basis, and 0.5% to 2% of B, a 0.002 to 0.15 percent of N , 0.25% or less of O, 0.15% or less of C, 0.001 to 0.05% of P, and the balance of Fe, and the coercive force iHc is 1 MA / m or more. The term “sintered permanent magnet” as used herein includes both sintered bodies of permanent magnet material before and after magnetization. The coercive force is measured at room temperature (25 ° C.). P is preferably 0.003 to 0.05% by mass, and more preferably 0.008 to 0.05% by mass.

The sintered permanent magnet of the present invention has a ring shape having an outer diameter of 10 to 100 mm, an inner diameter of 8 to 96 mm, and a height of 10 to 70 mm, and a plurality of magnetic poles extending in the axial direction of the outer peripheral surface. Is preferably present. The sintered permanent magnet of the present invention has an outer diameter of 10 to 30 mm, an inner diameter of 8 to 28 mm, a height of 10 to 50 mm, particularly an outer diameter of 10 to 25 mm, an inner diameter of 8 to 23 mm, and a height of 10 to 40 mm. Small ring magnet. The sintered permanent magnet of the present invention is preferably a radial anisotropic sintered R-Fe-B permanent magnet. The sintered permanent magnet of the present invention preferably has a density of 7.52 to 7.85 g / cm ³ .

The distribution of the surface magnetic flux density B ₀ along the magnetic pole of the axis of the ring magnet is preferably in the range of 92.5% or more of the maximum value of B ₀ . That is, the variation of the surface magnetic flux density B ₀ on magnetic pole in the axial direction of the ring magnet is preferably not more than 7.5% of the maximum of B _0. Wherein the variation of the surface magnetic flux density B ₀ is represented by the maximum value of / B ₀ (minimum value of the maximum value -B ₀ of _{B 0)) × 100 (%} ). Maximum and minimum values of B ₀ are those measured in the range of the height H of the ring magnet. Distribution of the surface magnetic flux density B ₀ is measured by moving the probe of the gauss meter is vertically opposed to the outer peripheral surface of the ring magnet, and in the axial direction (length direction) of the ring magnet. More preferably the variation of the surface magnetic flux density B ₀ is within 5%, particularly preferably within 3%.

In one embodiment of the invention, R is 27-32% by weight. In another embodiment of the present invention, R is greater than 32% by weight and 33.5% by weight or less. In the latter case, the sintered permanent magnet of the present invention, the weight% based on 32% ultra and 33.5 following% R, and 0.5% to 2% of B, a O of 0.25% or less super and 0.6%, 0.01 It has a composition consisting of 0.15% C, 0.002-0.05% N, 0.001-0.05% P, and the balance Fe, with an outer diameter of 10-100 mm, an inner diameter of 8-96 mm, and 70 mm a height of the ring-shaped, has a magnetic anisotropy in the circumferential direction of the ring, the distribution of surface magnetic flux density B ₀ on magnetic pole in the axial direction of the ring of the maximum of B ₀ It is characterized by being within the range of 92.5% or more. In this case, it is preferred variation of the surface magnetic flux density B ₀ is within 7.5%, more preferably within 5%, particularly preferably within 3%. The sintered permanent magnet preferably has a density of 7.42 to 7.75 g / cm ³ .

In the sintered permanent magnet of the present invention, part of Fe is 0 to 1% Nb, 0.01 to 1% Al, 0 to 5% Co, and 0.01 to 0.5% Ga on a mass % basis. And 0 to 1% of Cu. Nb is preferably 0.05 to 1% by mass. Al is preferably 0.01 to 0.3% by mass. Co is preferably 0.3 to 5% by mass, more preferably 0.3 to 4.5% by mass. Ga is preferably 0.03 to 0.4% by mass. Cu is preferably 0.01 to 1% by mass, and more preferably 0.01 to 0.3% by mass.

  The first method of the present invention for producing a sintered permanent magnet is as follows: (a) crushing a rare earth magnet material as fine powder, directly recovering it in mineral oil, synthetic oil or a mixed oil thereof to form a slurry, b) press-injecting the slurry into a mold cavity, wet-molding in a magnetic field therein, and (c) heating the obtained molded body under reduced pressure from the molded body to the mineral oil, The synthetic oil or a mixed oil thereof is removed, and (d) the molded body is sintered in a vacuum, and the axial direction of a hole opened in the cavity of the mold for injecting the slurry under pressure is as described above. It is characterized by being off the center of the center core of the mold.

  The second method of the present invention for producing a sintered permanent magnet is as follows: (a) crushing a rare earth magnet material into fine powder, directly recovering it in mineral oil, synthetic oil or a mixed oil thereof to form a slurry, b) press-injecting the slurry into a mold cavity, wet-molding in a magnetic field therein, and (c) heating the obtained molded body under reduced pressure from the molded body to the mineral oil, The synthetic oil or a mixed oil thereof is removed, and (d) the molded body is sintered in a vacuum, and the mineral oil, the synthetic oil or the mixed oil thereof is added with sodium hypophosphite as a fluidity improver. It is characterized by mixing.

  The third method of the present invention for producing a sintered permanent magnet comprises: (a) crushing a rare earth magnet material into fine powder, directly recovering the slurry in mineral oil, synthetic oil or a mixed oil thereof to form a slurry, b) press-injecting the slurry into a mold cavity, wet-molding in a magnetic field therein, and (c) heating the obtained molded body under reduced pressure from the molded body to the mineral oil, The synthetic oil or a mixed oil thereof is removed, and (d) the molded body is sintered in a vacuum, and the axial direction of a hole opened in the cavity of the mold for injecting the slurry under pressure is as described above. The present invention is characterized in that sodium hypophosphite is mixed as a fluidity improver with the mineral oil, the synthetic oil or the mixed oil thereof, which is outside the center of the center core of the mold.

  Although sodium hypophosphite is preferably added in the form of a solution of glycerin or ethanol, it is also possible to dissolve sodium hypophosphite in a non-aqueous solvent instead of the solution of glycerin or ethanol. However, glycerin or ethanol is preferably used as the solvent in consideration of the ease of handling of the solvent.

In the second production method of the sintered permanent magnet of the present invention, the oxygen content of the fine powder is preferably not more than 0.25 wt% ultra and 0.6 wt%.

Sintered permanent magnet of the present invention is by the inclusion of P desired amount, has an improved coercivity iHc. Further, by the method of the present invention, it is possible to produce a radially anisotropic sintered R-Fe-B-based permanent magnet which is free from deformation and cracks and has excellent magnetic orientation. Sintered permanent magnet of the present invention is suitable as a ring magnet used in particular motor.

[1] General composition of sintered permanent magnets of the composition invention, the 27 to 33.5% of R in mass% basis (at least one rare earth element R containing Y), and 0.5% to 2% of B , 0.002 to 0.15% N, 0.25% or less O, 0.15% or less C, 0.001 to 0.05% P, and the balance Fe. The content of each element can be measured by X-ray fluorescence analysis or the like.

(A) Main elements
(1) Rare earth element R
The content of the rare earth element R is generally 27-33.5% by mass. When the content of the rare earth element exceeds 33.5% by mass, the saturation magnetic flux density decreases and the corrosion resistance deteriorates. On the other hand, when the content of the rare earth element is less than 27% by mass, the amount of liquid phase necessary for densification of the sintered body is insufficient, so that the density of the sintered body is low and the coercive force iHc is low. In a preferred first composition of the present invention, R is 27-32% by weight, and in a preferred second composition, R is more than 32% by weight and 33.5% by weight or less.

When the content of O is more than 0.25% by mass and not more than 0.6% by mass, the amount of the rare earth element R is preferably more than 32% and not more than 33.5% on a mass % basis. If the amount of the rare earth element exceeds 33.5% by mass, the amount of the rare earth rich phase inside the sintered body increases, and the morphology becomes coarse, resulting in poor corrosion resistance. On the other hand, if the amount of the rare earth element is 32% by mass or less, the amount of liquid phase necessary for densification of the sintered body is insufficient, and the density of the sintered body is reduced. The magnetic force iHc is reduced. For sintered permanent magnets that require high corrosion resistance and to suppress the R to 32% by weight or less desirable.

(2) Boron B
The content of B is generally 0.5 to 2% by mass. When the B content is less than 0.5% by mass, B required for forming the main phase, R ₂ Fe ₁₄ B phase, is insufficient, and a soft magnetic R ₂ Fe ₁₇ phase is generated, and the coercive force iHc is reduced. I do. On the other hand, if the B content exceeds 2% by mass, the B-rich phase, which is a nonmagnetic phase, increases, and the residual magnetic flux density Br decreases.

(3) Nitrogen N
The content of N is generally 0.002 to 0.15% by mass. N in the sintered body is mainly present in the R-rich phase and combines with a part of the rare earth element to form a nitride. It is considered that the formation of nitride suppresses the anodic oxidation of the grain boundary phase, thereby improving the corrosion resistance of the sintered body. However, when the N content exceeds 0.15% by mass, the rare earth element necessary for the development of the coercive force iHc decreases due to the formation of nitride, and the coercive force iHc decreases. If the N content is less than 0.002% by mass, the corrosion resistance of the sintered body is low. Since nitriding does not occur in the fine pulverization in the Ar gas atmosphere, the content of N in the sintered body is 0.002 to 0.05% by mass.

In the process of coarsening the dissolved ingot, a slight amount of nitride is generated by nitrogen in the atmosphere. If this coarse powder is finely pulverized by a jet mill in a nitrogen gas or a nitrogen-containing Ar gas which does not substantially contain oxygen, nitriding further occurs. Here, "substantially contains no oxygen" means that the oxygen content is 0.001 % or less, more preferably 0.0005 % or less, and further preferably 0.0002 % or less. Therefore, the amount of coarse powder supplied per unit time to the jet mill and the ratio of Ar gas to nitrogen gas during fine pulverization are adjusted so that the N content of the obtained sintered body does not exceed 0.15% by mass. .

(4) Oxygen O
In the preferred first composition of the present invention, the O content is 0.25% by mass or less, and in the preferred second composition of the present invention, the O content is more than 0.25% by mass and 0.6% by mass or less. When the O content exceeds 0.6% by mass, a part of the rare earth element forms an oxide, so that the amount of the magnetically effective rare earth element becomes too small, and the coercive force iHc decreases. Since R is 27 to 32% by mass in the first composition, the upper limit of the O content is 0.25% by mass. On the other hand, since R is more than 32% by mass and 33.5% by mass or less in the second composition, the upper limit of the O content can be 0.6% by mass. On the other hand, in the first composition, the lower limit of the O content is not limited, but is preferably 0.05% by mass. In particular, in the first composition, high corrosion resistance can be obtained by suppressing the oxygen content and controlling the nitrogen content.

(5) Carbon C
The content of C is generally 0.15% by mass or less. When the content of C is more than 0.15% by mass, a part of the rare earth element forms a carbide, and the magnetically effective rare earth element decreases, and the coercive force iHc decreases. The C content is preferably 0.12% by mass or less, more preferably 0.1% by mass or less. On the other hand, the lower limit of the content of C is not limited, but is preferably 0.01% by mass.

(6) Phosphorus P
It was found that the addition of a small amount of P was effective for improving the coercive force iHc of the R-Fe-B permanent magnet. 1, 15.7% of Nd in mass% basis, 7.1% of Pr, 7.5% of Dy, 1.1% of B, 2.0% of Co, 0.09% of Cu, 0.08% of Ga, x% of P, remainder Fe 3 shows a change in coercive force iHc with respect to a content x of P in a sintered body having a composition consisting of The improvement of the coercive force iHc is observed at a P content of 0.0005% by mass, but is remarkable at a P content of 0.001% by mass or more. At 0.001% by mass or more, the coercive force iHc increases as the P content increases. However, when the content of P exceeds 0.05% by mass, the strength of the sintered body decreases. Therefore, the content of P in the sintered body is set to 0.001 to 0.05% by mass. In this range, no decrease in saturation magnetization is observed.

  The reason why the coercive force iHc is improved by P is not always clear, but P exists at the pinning site that fixes the domain wall existing at the interface between the grain boundary phase of the sintered body and the main phase crystal grains, and P It is presumed to change the composition or morphology to enhance the adhesion of the domain wall. The lower limit of the content of P is preferably 0.003% by mass, and more preferably 0.008% by mass. The upper limit of the P content is preferably 0.04% by mass, and more preferably 0.02% by mass.

The method of controlling the content of P is not limited, but (1) as a raw material metal of the R-Fe-B-based permanent magnet ingot, a Fe-P alloy or a Fe-BP alloy having a known P content in the Fe raw alloy. A method of controlling the content of P in the ingot by mixing a predetermined amount of a P-containing Fe-based alloy such as an alloy, and (2) coarsely pulverizing the R-Fe-B-based permanent magnet ingot manufactured by vacuum melting. A predetermined amount of sodium hypophosphite (NaPH ₂ O ₂ ) is mixed with the obtained coarse powder of 20 to 500 μm in the form of a solution such as an aqueous solution and dried to obtain a coarse powder for R-Fe-B permanent magnets. controlling the content of P in the powder method, and (3) the slurry a mineral oil for generation, synthetic oils, or mixtures oil flow improvers as glycerin or ethanol solution form sodium hypophosphite To make the proportion of sodium hypophosphite 0.01% by mass or more, and wet molding. When obtaining efficiently molded body by using a wet molding method while preventing oxidation of the fine powder, it is the most preferred method of (3).

  In the method (3), the addition of a sodium hypophosphite solution having a P content of less than 0.001% by mass does not sufficiently improve the fluidity of the slurry. In addition, the mixing amount of the sodium hypophosphite glycerin solution or the sodium hypophosphite ethanol solution is adjusted so that the ratio of sodium hypophosphite to mineral oil, synthetic oil or a mixed oil thereof does not exceed 0.5% by mass. It is preferable to control.

The sintered permanent magnet of (B) optional elements present invention, a portion of Fe Co, Nb, Al, may be substituted by at least one selected from the group consisting of Ga and Cu. The amount of each substituting element is represented by mass percentage to the total sintered permanent magnet.

(1) Cobalt Co
The amount of Co is generally 0-5% by weight or less. Co improves the Curie point of the sintered magnet, that is, improves the temperature coefficient of saturation magnetization. However, when the amount of Co exceeds 5% by mass, both the residual magnetic flux density Br and the coercive force iHc sharply decrease. The preferable substitution amount of Co is 0.3 to 5% by mass, particularly 0.3 to 4.5% by mass. If the amount of Co is less than 0.3% by mass, the effect of improving the temperature coefficient is small.

(2) Niobium Nb
The amount of Nb is generally between 0 and 1% by weight. Nb boride generated during the sintering process suppresses abnormal growth of crystal grains. However, when the amount of Nb exceeds 1% by mass, the amount of Nb boride generated increases, so that the residual magnetic flux density Br decreases. If the amount of Nb is less than 0.05% by mass, the effect of suppressing abnormal growth of crystal grains is insufficient, so that the preferred amount of substitution of Nb is 0.05 to 1% by mass.

(3) Aluminum Al
The amount of Al is generally between 0.01 and 1% by weight. Al has the effect of increasing the coercive force iHc. When the amount of Al is less than 0.01% by mass, the effect of improving the coercive force iHc is insufficient. If the amount of Al exceeds 1% by mass, the residual magnetic flux density Br sharply decreases. The upper limit of Al is preferably 0.3% by mass.

(4) Gallium Ga
The amount of Ga is generally between 0.01 and 0.5% by weight. A small amount of Ga improves the coercive force iHc, but the effect is insufficient if the amount of Ga is less than 0.01% by mass. On the other hand, when the amount of Ga exceeds 0.5% by mass, the decrease in the residual magnetic flux density Br becomes remarkable, and the coercive force iHc also decreases. The amount of Ga is preferably between 0.03 and 0.4% by weight.

(5) Copper Cu
The amount of Cu is generally between 0 and 1% by weight. Cu traces results in improvement of the coercive force iHc but, effect of addition quantity of Cu is more than 1 wt% is saturated. When the addition amount of Cu is less than 0.01% by mass, the effect of improving the coercive force iHc is insufficient, so the amount of Cu is preferably 0.01 to 1% by mass, more preferably 0.01 to 0.3% by mass. preferable.

Sintered permanent magnet according to the first embodiment of the present invention, a 27 to 32% of R in mass% basis, and 0.5% to 2% of B, a 0.002 to 0.15 percent of N, 0.05 to 0.25% of O And 0.01 to 0.15% of C, 0.001 to 0.05% of P, and the balance of Fe.

The sintered permanent magnet according to the second embodiment of the present invention, 32% ultra and 33.5% or less of R in mass% basis, and 0.5% to 2% of B, a 0.002 to 0.05 percent of N, 0.25% It has a composition consisting of super-O and 0.6% or less of O, 0.01 to 0.15% of C, 0.001 to 0.05% of P, and the balance of Fe. A sintered body having this composition is obtained using a slurry prepared by mixing dry fine powder pulverized in an atmosphere having an oxygen content of 0.005 to 0.5% with mineral oil, synthetic oil, or a mixed oil thereof.

Also in sintered permanent magnet of any of the embodiments 0.3 to 5% of Co part in mass% basis of Fe, 0.05 to 1% of Nb, 0.01 to 1% of Al, 0.01 to 0.5% of Ga, It may be replaced with at least one selected from the group consisting of 0.01 to 1% Cu.

[2] Manufacturing method
(A) Finely pulverized R-Fe-B-based permanent magnet coarse powder having the above composition is mixed with (a) an atmosphere consisting of nitrogen gas and / or Ar gas having an oxygen content of substantially 0%, or (b) ) Finely pulverized by a jet mill in an atmosphere composed of nitrogen gas and / or Ar gas having an oxygen content of 0.005 to 0.5% to obtain fine powder having an average particle diameter of 3 to 6 µm. In order to control the amount of N in the sintered body, it is preferable that the atmosphere in the jet mill is Ar gas, and a slight amount of nitrogen gas is introduced therein to adjust the concentration of nitrogen gas in the Ar gas.

When the inside of the jet mill is set to a nitrogen gas atmosphere, it is preferable to control the degree of N incorporation into the magnet powder by controlling the supply amount of the coarse powder during pulverization, and to control the amount of N in the obtained sintered body. Also, when coarse powder containing 0.002 to 0.15 mass% of N is finely pulverized in an atmosphere having an oxygen content of 0.005 to 0.5%, oxidation reaction of rare earth elements in the coarse powder occurs preferentially, and nitriding reaction hardly occurs. It is negligible.

(B) Slurry production At the fine powder collection port of the jet mill, a container containing mineral oil, synthetic oil or a mixture of these oils is installed, and the inside of this container is also made of nitrogen gas and / or Ar gas, and the fine powder is collected. The oil is directly recovered into mineral oil, synthetic oil, or a mixed oil thereof without being exposed to the atmosphere to form a slurry.

  It is preferable to mix sodium hypophosphite as a fluidity improver with mineral oil, synthetic oil or a mixed oil thereof. The sodium hypophosphite is preferably added in the form of a solution of glycerin or ethanol to mineral oil, synthetic oil or a mixture thereof. The concentration of the sodium hypophosphite in the glycerin or ethanol solution is not particularly limited, but the ratio of sodium hypophosphite to the mineral oil, the synthetic oil or the mixed oil thereof is preferably in the range of 0.01 to 0.5% by mass. When the proportion of sodium hypophosphite is less than 0.01% by mass, the effect of improving the fluidity of the slurry is insufficient. When a solution of glycerin or ethanol of sodium hypophosphite is mixed with a mineral oil, a synthetic oil, or a mixed oil thereof, the mineral oil, the synthetic oil or the mixed oil thereof becomes acidic, and the fine powder recovered therefrom is mixed with Reacts chemically with sodium phosphate.

  As a result, the content of P in the obtained radially anisotropic sintered R-Fe-B permanent magnet increases. In the radial anisotropic sintered R-Fe-B permanent magnet, P enters a nonmagnetic grain boundary phase which is mainly rich in rare earth elements. As a result of studies by the inventors, the content of P in the sintered body is set to 0.001 to 0.05% by mass, and the ratio of sodium hypophosphite to mineral oil, synthetic oil or a mixed oil thereof is set to 0.01 to 0.5%. It is preferable to set it to mass%. The addition of the sodium hypophosphite glycerin solution or the sodium hypophosphite ethanol solution may be performed before or after the fine powder is collected in mineral oil, synthetic oil, or a mixed oil thereof. In any case, when the fine powder is mixed with a mineral oil, a synthetic oil, or a mixed oil thereof to form a slurry, the oxidation or nitridation of the fine powder is prevented due to a shielding effect from the atmosphere by the mineral oil, the synthetic oil, or the mixed oil thereof. You. Therefore, the O and N contents of the obtained sintered body are not substantially different from the O and N contents of the fine powder.

(C) Slurry Forming FIG. 2 shows an example of a forming apparatus used in the method of the present invention. An area indicated by reference numeral 11 indicates a longitudinal section of the molding apparatus, and an area indicated by reference numeral 12 indicates a cross section of a mold of the molding apparatus and an enlarged view thereof (an area surrounded by a square). The mold has a columnar core 4, a cylindrical die member 3, a lower punch 9, and an upper punch 10, and a space surrounded by these forms a cavity 6. The cylindrical die member 3 is supported by the die case 2. A pair of magnetic field generating coils 1 are arranged above and below the core 4, and apply a magnetic field line 7 to the cavity 6 through the core 4. The die case 2 is provided with a slurry injection hole 5 opening to the cavity 6.

  In the mold for injecting the slurry under pressure, it is preferable that the axial direction of the slurry injection hole 5 opening in the cavity is deviated from the center O of the center core 4 of the mold. When the axial direction of the slurry injection hole 4 is deviated from the core center O, the fine powder slurry injected under pressure does not collide with the mold core 4 perpendicularly, but along the outer peripheral surface of the core 4 or the inner peripheral surface of the die. The ring-shaped cavity 6 is smoothly and substantially spirally filled, and a high filling density is obtained.

  On the other hand, when the axial direction of the slurry injection hole 5 coincides with the center O of the mold core, the slurry injected under pressure collides perpendicularly with the mold core 4 and is divided into right and left and the slurry injection hole 5 Merges at 180 ° opposite position. As a result, a so-called seam is formed, and cracks are generated in the obtained sintered body.

In the present invention, as shown in FIG. 2, the center axis of the slurry injection hole 5 and the radius of the mold core 4 (a straight line connecting the point A where the center axis of the slurry injection hole 5 hits the core 4 and the core center O). (Right angle or acute angle side) slightly varies depending on the size of the mold cavity 6, but is 5 ° to 90 °, preferably 10 ° to 90 °, and particularly 30 ° to 90 °. The injection pressure of the slurry into the mold cavity 6 is not limited, but is preferably 4.9 × 10 ⁴ Pa to 3.9 × 10 ⁶ Pa (about 0.5 to 40 kgf / cm ² ), and 9.8 × 10 ⁴ Pa to 2.9 × 10 ⁶ Pa (about 1 to 30 kgf / cm ² ) is more preferable, and 2.0 × 10 ⁵ Pa to 1.5 × 10 ⁶ Pa (about 2 to 15 kgf / cm ² ) is particularly preferable.

The strength of the radial orientation magnetic field applied to the mold cavity 6 for orienting the fine powder in the slurry is preferably 159 kA / m (about 2 kOe) or more, and more preferably 239 kA / m (about 3 kOe). kOe). After the slurry is injected under pressure, pressure wet molding is performed while maintaining the orientation magnetic field. If the intensity of the orientation magnetic field is less than 159 kA / m (about 2 kOe), the orientation of the fine powder is insufficient, and good magnetic properties cannot be obtained. The slurry is injected while applying an orientation magnetic field of 159 kA / m (about 2 kOe) or more to the mold cavity 6, and during or after the injection, a pressure is applied by applying an alignment magnetic field higher than the initial alignment magnetic field strength. Wet molding may be used. By wet-molding the slurry with improved fluidity under the above conditions, a molded article having a high density of 4.0 to 4.8 g / cm ³ can be obtained.

(D) Deoiling The obtained molded body is heated under reduced pressure to remove mineral oil, synthetic oil or a mixed oil thereof in the molded body. The conditions for the heat treatment of the molded body under reduced pressure are as follows: a degree of vacuum of 13.3 Pa (about 0.1 Torr) or less, for example, about 6.7 Pa (about 5.0 × 10 ^-2 Torr), and a heating of 100 ° C. or more, for example, about 200 ° C. Temperature. The heating time varies depending on the weight and processing amount of the molded body, but is preferably 1 hour or more.

(E) Sintering The sintering of the compact is performed at a vacuum of 0.13 Pa (about 0.001 Torr) or less, preferably 6.7 × 10 ^-2 Pa (about 5.0 × 10 ^-4 Torr) or less, in the range of 1000 to 1150 ° C. It is preferable to carry out in. As a result, a sintered body using a slurry finely pulverized in an atmosphere having an oxygen content of substantially 0% can obtain a density of 7.52 to 7.85 g / cm ³ and an oxygen content of 0.005 to 0.5% in an atmosphere having an oxygen content of 0.005 to 0.5%. In the sintered body using the slurry finely pulverized, a density of 7.42 to 7.75 g / cm ³ is obtained. In any case, the oxidation effect of the fine powder and the compact is prevented by the shielding effect from the atmosphere by the mineral oil, the synthetic oil or the mixed oil thereof, and the O content of the former sintered body is 0.05 to 0.25 mass%. The O content of the latter sintered body is more than 0.25% by mass and 0.60% by mass or less.

As described above, the slurry having improved fluidity is smoothly and substantially spirally pressure-injected into the ring-shaped mold cavity in the radial orientation magnetic field, so that a high filling property, and thus a high compact density, can be obtained. As a result, it is possible to prevent cracks, chips, deformation, and the like from occurring in the molded body or the sintered body. Therefore, the ring-shaped sintered permanent magnet oriented radially, outer diameter 10 to 100 mm, those having a size of inner diameter from 8 to 96 mm, height 10 to 70 mm is obtained. In particular, the present invention is suitable for manufacturing a small ring magnet having an outer diameter of 10 to 30 mm, an inner diameter of 8 to 28 mm, and a height of 10 to 50 mm.

  In addition, since the slurry is smoothly filled in the orientation magnetic field, the density of the compact is not only high but also uniform, and therefore, the distribution of the surface magnetic flux density in the axial direction of the ring magnet can be achieved. When the variation of the surface magnetic flux density in the axial direction of the ring magnet is set to 7.5% or less, cogging torque (especially higher-order cogging torque) generated when the ring magnet is used for a rotating machine can be sufficiently suppressed. When the variation of the surface magnetic flux density is 5% or less, particularly 3% or less, it is possible to configure a rotating machine with no loss of energy and with extremely low noise.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. The magnetic properties were measured at room temperature (25 ° C.). The average particle size of the powder was measured by an air permeation method.

Example 1
17.6% Nd, 7.9% Pr, 5% Dy, 1.1% B, 0.08% Al, 1.5% Co, 0.1% Cu, 0.01% P, 0.01% O, 0.004% by mass % % Of C, 0.006% of N, and the balance of Fe were produced. This ingot was pulverized to a coarse powder having a particle size of 20 to 500 μm. Analysis of the composition of this coarse powder, wt% based 17.5% of Nd, 7.7% of Pr, 5% of Dy, 1.1% of B, 0.08% of Al, 1.5% of Co, 0.1% of Cu, 0.01 % P, 0.15% O, 0.015% C, 0.006% N, balance Fe.

After 100 kg of the coarse powder was charged into the jet mill, the inside of the jet mill was replaced with Ar gas to reduce the oxygen concentration to substantially 0%. Next, nitrogen gas was introduced to adjust the concentration of nitrogen gas in the Ar gas to 0.005%. In this atmosphere, the coarse powder was finely pulverized at a pressure of 6.9 × 10 ⁵ Pa (about 7.0 kgf / cm ² ) and an amount of coarse powder supplied per hour of 12 kg / h . A container filled with mineral oil was installed at the fine powder collecting port of the jet mill, and the obtained fine powder was directly collected in mineral oil in an Ar gas atmosphere. The average particle size of the obtained fine powder was 4.5 μm. By adjusting the amount of the mineral oil, the fine powder concentration in the obtained slurry was set to 75% by mass.

This slurry was wet-formed in a mold cavity at a pressure of 4.9 × 10 ⁷ Pa (about 0.5 ton / cm ² ) while applying an orientation magnetic field of 796 kA / m (about 10 kOe). The direction of application of the orientation magnetic field was perpendicular to the molding direction. The resulting compact is heated at 80 ° C. for 2 hours in a vacuum of 5.3 Pa (about 4.0 × 10 ⁻² Torr) to remove mineral oil, and then 6.7 × 10 ⁻³ Pa (about 5.0 × 10 ⁻⁵ Torr). (Torr) at 1065 ° C. for 4 hours. The composition of the obtained sintered body was 17.5% Nd, 7.7% Pr, 5% Dy, 1.1% B, 0.08% Al, 1.5% Co, 0.1% Cu, 0.010 % by mass %. % P, 0.017% O, 0.070% C, 0.045% N, balance Fe. This sintered body was subjected to a heat treatment at 480 ° C. × 2 hours in an Ar gas atmosphere. After machining, a result of measurement of magnetic properties of the sintered magnet was good as shown in Table 2.

Comparative Example 1
An ingot having the same composition as in Example 1 except that P was not contained was produced, and a coarse powder was produced in the same manner as in Example 1. The composition of this coarse powder was the same as that of Example 1 except that P was not contained and O was 0.14% by mass. This coarse powder was finely pulverized in the same manner as in Example 1. The average particle size of the obtained fine powder was 4.5 μm. Analysis of the composition of the sintered bodies produced in the same manner from the pulverized as in Example 1, 17.5% of Nd in mass% basis, 7.7% of Pr, 5% of Dy, 1.1% of B, 0.08% of Al, 1.5% Co, 0.1% Cu, 0.16% O, 0.070 % C, 0.045% N, balance Fe. The sintered body was machined and its magnetic properties were measured. Table 2 shows the results. Table 2 shows that the coercive force iHc of Comparative Example 1 is lower than that of Example 1.

Example 2
19.8% Nd, 8.9% Pr, 1.3% Dy, 1.1% B, 0.10% Al, 2.5% Co, 0.2% Nb, 0.08% Ga, 0.01% O, 0.003% by mass % % Of C, 0.005% of N, and the balance of Fe were produced. This ingot was pulverized to a coarse powder having a particle size of 20 to 500 μm. Analysis of the composition of this coarse powder showed 19.7% Nd, 8.8% Pr, 1.3% Dy, 1.1% B, 0.10% Al, 2.5% Co, 0.2% Nb, 0.08 % by mass %. % Ga, 0.12% O, 0.013% C, 0.007% N, balance Fe.

To 100 kg of the coarse powder, 454 g of an aqueous solution in which 5% by mass of sodium hypophosphite was dissolved in pure water was mixed and dried in vacuum. When the composition of the coarse powder after drying was analyzed, 19.7% Nd, 8.8% Pr, 1.3% Dy, 1.1% B, 0.10% Al, 2.5% Co, 0.2% Nb were obtained based on mass %. , 0.08% Ga, 0.008% P, 0.16% O, 0.013% C, 0.009% N, and the balance Fe. This coarse powder was finely pulverized in the same manner as in Example 1. The average particle size of the obtained fine powder was 4.7 μm. Analysis of the composition of the sintered bodies produced in the same manner from the pulverized as in Example 1, 19.7% of Nd in mass% basis, 8.8% of Pr, 1.3% of Dy, 1.1% of B, 0.10% of Al, 2.5% Co, 0.2% Nb, 0.08% Ga, 0.008% P, 0.18% O, 0.067% C, 0.055% N, balance Fe. This sintered body was machined and its magnetic properties were measured. As shown in Table 2 , the results were good.

Comparative Example 2
100 kg of the same coarse powder as in Example 2 was pulverized in the same manner as in Example 1 except that an aqueous solution of sodium hypophosphite was not added. The average particle size of the obtained fine powder was 4.7 μm. Analysis of the composition of the sintered bodies produced in the same manner from the pulverized as in Example 1, 19.7% of Nd in mass% basis, 8.8% of Pr, 1.3% of Dy, 1.1% of B, 0.10% of Al, 2.5% Co, 0.2% Nb, 0.08% Ga, 0.16% O, 0.067% C, 0.050% N, balance Fe. The sintered body was machined and its magnetic properties were measured. As shown in Table 2 , the coercive force iHc was lower than that of Example 2.

Example 3
On a mass % basis, 19.85% Nd, 8.95% Pr, 1.00% Dy, 1.02% B, 0.10% Al, 2.00% Co, 0.10% Cu, 0.15% O, 0.04% C, A coarse powder for an R-Fe-B permanent magnet having a composition consisting of 0.02% of N and the balance of Fe is charged into a jet mill, and is replaced with nitrogen gas. Then, the pressure is 6.9 × 10 ⁵ Pa (7.0 kgf / cm). ² ), pulverized at a feed rate of coarse powder of 15 kg / h. The obtained fine powder was directly collected in a mineral oil (“Super Sol PA30”, manufactured by Idemitsu Kosan Co., Ltd.) without being exposed to the air to form a slurry.

  This mineral oil was preliminarily mixed with a 5% by mass sodium phosphite glycerin solution so that the ratio of sodium hypophosphite to the mineral oil was 0.1% by mass. The mass ratio of mineral oil to fine powder in the slurry was 1: 3. The average particle size of the obtained fine powder was 4.5 μm. The slurry prepared in this manner was injected under pressure into a mold cavity in which the alignment magnetic field generating coil shown in FIG. 2 was arranged, and was molded.

The angle θ between the axial direction of the slurry injection hole 5 and the radial direction of the mold core 4 was 30 °. The strength of the radial orientation magnetic field applied to the cavity was 239 kA / m (3 kOe), and the slurry injection pressure was 3.9 × 10 ⁵ Pa (4 kgf / cm ² ). After the slurry injection, while the orientation magnetic field strength was maintained at 239 kA / m (3 kOe), wet molding was performed in a magnetic field at a pressure of 7.8 × 10 ⁷ Pa (0.8 ton / cm ² ), and the outer diameter was 24.5 mm and the inner diameter was 17.4. A compact having a size of mm × 30.0 mm in height was obtained. The density of the formed body was 4.30 g / cm ³ .

The molded body was subjected to a deoiling treatment at 200 ° C. for 2 hours under a reduced pressure of 6.7 Pa (5 × 10 ⁻² Torr), and then 1050 under a reduced pressure of 2.7 × 10 ⁻² Pa (2 × 10 ⁻⁴ Torr). The sintering was performed at a temperature of 3 ° C. for 3 hours. The obtained sintered body had a size of 20.0 mm in outer diameter × 15.0 mm in inner diameter × 26.0 mm in height, and a density of 7.58 g / cm ³ . The sintered body was subjected to a heat treatment at 500 ° C. for 2 hours, and then machined to finish to a size of 19.6 mm in outer diameter × 15.4 mm in inner diameter × 25.0 mm in height. When the surface magnetic flux density was measured after the 4-pole magnetization, a high peak value was shown as shown in Table 4 .

As shown in FIG. 3, a sample 21b of 5 mm × 7 mm × 1 mm (the thickness direction of 1 mm was a magnetization direction) was cut out from the sintered body 20. Reference numeral 21 denotes a sample before cutting. When eight samples 21b were stacked in the thickness direction and the magnetic properties were measured, high values as shown in Table 4 were shown. Analysis of the composition of the sintered body, 19.85% of Nd in mass% basis, 8.95% of Pr, 1.00% of Dy, 1.02% of B, 0.10% of Al, 2.00% of Co, 0.10% of Cu, It consisted of 0.17% O, 0.06% C, 0.05% N, 0.01% P and the balance Fe. When a line was analyzed on the sample 21b by EPMA, a P peak was confirmed as shown in FIG. From FIG. 4, it can be seen that P exists mainly in the rare earth-rich phase at the crystal grain boundaries.

Example 4
The same coarse powder as in Example 3 was finely pulverized in the same manner as in Example 3, and recovered in mineral oil ("Super Sol PA30", manufactured by Idemitsu Kosan Co., Ltd.) to obtain a slurry. The mass ratio of mineral oil to fine powder was 1: 3. The average particle size of the obtained fine powder was 4.8 μm. A 10% by mass sodium hypophosphite ethanol solution was mixed with the slurry so that the ratio of sodium hypophosphite to mineral oil was 0.3% by mass. The obtained slurry was pressure-injected into a mold cavity having an angle θ of 5 ° between the axis of the slurry injection hole and the radius of the mold core in the same manner as in Example 3, and wet-molded in a magnetic field to obtain an outer diameter. A molded article having a size of 24.5 mm, an inner diameter of 17.4 mm and a height of 30.0 mm was obtained. The density of the molded product was 4.40 g / cm ³ .

This compact was deoiled and sintered in the same manner as in Example 3, to obtain a sintered body having an outer diameter of 20.1 mm, an inner diameter of 14.9 mm, and a height of 26.2 mm. The density of the sintered body was 7.56 g / cm ³ . This sintered body was subjected to a heat treatment at 500 ° C. × 2 hours. The sintered body was machined to a size of 19.6 mm in outer diameter × 15.4 mm in inner diameter × 25.0 mm in height, and subjected to 4-pole magnetization in the same manner as in Example 3. Measurement of the surface magnetic flux density showed a high peak value as shown in Table 4 .

A sample 21b was cut out from the sintered body as shown in FIG. The cutout position, dimensions, and measurement conditions of the magnetic properties of the sample 21b were the same as those in Example 3. The magnetic properties were good as shown in Table 4 . Analysis of the composition of the sintered body, 19.85% of Nd in mass% basis, 8.95% of Pr, 1.00% of Dy, 1.02% of B, 0.10% of Al, 2.00% of Co, 0.10% of Cu, 0.16 % O, 0.06% C, 0.04% N, 0.03% P, balance Fe. As a result of line analysis of the sample 21b by EPMA, a P peak was confirmed as shown in FIG.

Example 5
In the same manner as in Example 3, the slurry prepared in Example 3 was injected under pressure into a mold cavity to which an orientation magnetic field of 239 kA / m (3 kOe) was applied in the radial direction, and wet-molded in a magnetic field. The injection pressure of the slurry was 3.9 × 10 ⁵ Pa (4 kgf / cm ² ). 0.5 seconds after the start of the slurry injection, the intensity of the alignment magnetic field is increased to 398 kA / m (5 kOe). After the completion of the slurry injection, the magnetic field is maintained, and the wet forming is performed. The outer diameter is 24.5 mm and the inner diameter is 17.4 mm. X A molded body having a height of 30.0 mm was obtained. The density of the obtained molded body was 4.25 g / cm ³ .

This molded body was deoiled and sintered in the same manner as in Example 3 to obtain a sintered body having an outer diameter of 19.9 mm, an inner diameter of 15.1 mm and a height of 26.1 mm. The density of the sintered body was 7.59 g / cm ³ . This sintered body was heat-treated in the same manner as in Example 3, and was machined to a size of 19.6 mm in outer diameter × 15.4 mm in inner diameter × 25.0 mm in height. The obtained product was subjected to four-pole magnetization, and the surface magnetic flux density was measured along the magnetic poles in the axial direction. As shown in Table 4 , the results were good. When the magnetic properties of the sample cut out in the same manner as in Example 3 were measured, the sample had high values as shown in Table 4 .

Example 6
As in Example 3, the slurry prepared in Example 3 was injected under pressure into a mold cavity having an angle θ of 45 ° between the axis of the slurry injection hole and the radius of the mold core, and was wet-molded in a magnetic field. However, the mold was changed to one for large diameter ring magnets. The intensity of the radial alignment magnetic field applied to the cavity was 478 kA / m (about 6 kOe), and the injection pressure was 5.9 × 10 ⁵ Pa (about 6 kgf / cm ² ). After the slurry injection, while maintaining the orientation magnetic field strength at 478 kA / m (approximately 6 kOe), wet molding was performed in a magnetic field at a pressure of 4.9 × 10 ⁷ Pa (0.5 ton / cm ² ). A compact having a size of 95.0 mm × height of 20.5 mm was obtained. The density of the obtained molded body was 4.28 g / cm ³ .

This compact was deoiled and sintered in the same manner as in Example 3, to obtain a sintered body having an outer diameter of 92.5 mm, an inner diameter of 81.5 mm and a height of 18 mm. The density of the sintered body was 7.57 g / cm ³ . The sintered body was subjected to a heat treatment at 500 ° C. for 2 hours. The sintered body was machined and finished to dimensions of 91.5 mm in outer diameter × 80.5 mm in inner diameter × 16 mm in height. When the surface magnetic flux density was measured along the magnetic poles in the axial direction by performing 16-pole magnetization, the results were good as shown in Table 4 . When four samples of 5 mm × 10 mm × 2 mm cut out from the sintered body were stacked in the thickness direction and the magnetic characteristics were measured, the values were high as shown in Table 4 .

Example 7
As in Example 3, the slurry prepared in Example 3 was injected under pressure into a mold cavity in which the angle θ between the axis of the slurry injection hole and the radius of the mold core was 15 °, and was wet-molded in a magnetic field. However, the mold was changed to a medium-diameter long ring magnet. The intensity of the radial alignment magnetic field applied to the cavity was 199 kA / m (about 2.5 kOe), and the injection pressure was 2.0 × 10 ⁵ Pa (about 2 kgf / cm ² ). After the slurry injection, the orientation magnetic field strength was increased to 637 kA / m (8 kOe), and wet molding was performed in a magnetic field at a pressure of 3.9 × 10 ⁷ Pa (0.4 ton / cm ² ) while maintaining this orientation magnetic field strength. A molded body having a diameter of 50 mm, an inner diameter of 40 mm and a height of 76 mm was obtained. The density of the formed body was 4.15 g / cm ³ .

This compact was deoiled and sintered in the same manner as in Example 3, to obtain a sintered body having an outer diameter of 40.4 mm, an inner diameter of 35.0 mm and a height of 65.2 mm. The density of the sintered body was 7.59 g / cm ³ . The sintered body was subjected to a heat treatment at 500 ° C. for 2 hours. This sintered body was machined and finished to dimensions of 40.0 mm in outer diameter × 35.4 mm in inner diameter × 64.2 mm in height. Eight-pole magnetization was performed and the surface magnetic flux density was measured along the magnetic poles in the axial direction. As shown in Table 4 , the results were good. When eight samples of 5 mm × 8 mm × 1 mm cut out from the sintered body were stacked in the thickness direction and the magnetic characteristics were measured, the magnetic characteristics were high as shown in Table 4 .

Comparative Example 3
The same coarse powder as in Example 3 was finely pulverized in the same manner as in Example 3, and the obtained fine powder was recovered in mineral oil ("Super Sol PA30", manufactured by Idemitsu Kosan Co., Ltd.) to obtain a slurry. The mass ratio of mineral oil to fine powder was 1: 3. The average particle size of the fine powder was 4.5 μm. A 5% by mass sodium hypophosphite glycerin solution was previously mixed with the mineral oil so that the ratio of sodium hypophosphite to the mineral oil was 1% by mass. The obtained slurry was injected under pressure into a mold cavity in the same manner as in Example 3, and wet-molded in a magnetic field to obtain a molded product having an outer diameter of 24.5 mm, an inner diameter of 17.4 mm and a height of 30.0 mm. The density of the formed body was 4.35 g / cm ³ .

This compact was deoiled and sintered in the same manner as in Example 3, to obtain a sintered body having an outer diameter of 20.2 mm, an inner diameter of 15.1 mm and a height of 25.9 mm. The density of the sintered body was 7.58 g / cm ³ . The sintered body was subjected to a heat treatment at 500 ° C. for 2 hours. An attempt was made to machine this sintered body. However, the mechanical strength of the sintered body was so low that the sintered body was broken by a load during working and could not be evaluated. Eight pieces of 5 mm × 7 mm × 1 mm samples cut out from the pieces of the sintered body were stacked in the thickness direction, and the magnetic properties were measured. Table 4 shows the results. Analysis of the composition of the sintered body, 19.85% of Nd in mass% basis, 8.95% of Pr, 1.00% of Dy, 1.02% of B, 0.10% of Al, 2.00% of Co, 0.10% of Cu, 0.16 % O, 0.07% C, 0.04% N, 0.09% P, balance Fe.

Comparative Example 4
The same coarse powder as in Example 3 was finely pulverized in the same manner as in Example 3, and the obtained fine powder was recovered in mineral oil ("Super Sol PA30", manufactured by Idemitsu Kosan Co., Ltd.) to obtain a slurry. The mass ratio of mineral oil to fine powder was 1: 3. The average particle size of the fine powder was 4.5 μm. No fluidity improver (sodium hypophosphite glycerin solution or sodium hypophosphite ethanol solution) was mixed with either the mineral oil or the slurry. This slurry was pressure-injected into a mold cavity as in Example 3, and wet-molded in a magnetic field.However, the fluidity of the slurry during pressure injection was poor, and the filling property into the mold cavity was low. The dimensions of the obtained molded body were 24.5 mm in outer diameter × 17.4 mm in inner diameter × 26.5 mm in height. The density of the molded product was 3.80 g / cm ³ .

This compact was deoiled and sintered in the same manner as in Example 3, to obtain a sintered body having an outer diameter of 19.7 mm, an inner diameter of 14.8 mm and a height of 23.3 mm. The density of the sintered body was 7.57 g / cm ³ . Since the filling property of the slurry on the upper punch side was poor, the upper punch side of the sintered body was deformed into an elliptical shape. Due to the deformation, the sintered body could not be machined to the desired product dimensions. The sintered body was subjected to a heat treatment at 500 ° C. × 2 hours, and a sample of 5 mm × 7 mm × 1 mm was cut out from a portion other than the deformed portion. Magnetic properties were measured by stacking eight samples in the thickness direction. Table 4 shows the results. Analysis of the composition of the sintered body, 19.85% of Nd in mass% basis, 8.95% of Pr, 1.00% of Dy, 1.02% of B, 0.10% of Al, 2.00% of Co, 0.10% of Cu, 0.16 % O, 0.07% C, 0.06% N, balance Fe. This sintered body was subjected to line analysis by EPMA. As shown in FIG. 6, there was no P peak present in the sintered bodies of Examples 3 and 4.

Comparative Example 5
Similarly to Example 3, the slurry prepared in Example 3 was pressure-injected into a mold cavity in which the axial direction of the slurry injection hole coincided with the radial direction of the mold core (θ = 0 °), and wet-slurried in a magnetic field. It was molded to obtain a molded body having an outer diameter of 24.5 mm, an inner diameter of 17.4 mm and a height of 30.0 mm. The density of the formed body was 4.29 g / cm ³ . This compact was deoiled and sintered in the same manner as in Example 3, to obtain a sintered body having an outer diameter of 20.1 mm, an inner diameter of 15.1 mm and a height of 25.9 mm. The density of the sintered body was 7.60 g / cm ³ . In the obtained sintered body, a crack in the longitudinal direction was generated at a position 180 ° opposite to the injection hole. Due to cracks, this sintered body could not be machined to the desired dimensions. Magnetic properties were measured by stacking eight 5 mm × 7 mm × 1 mm samples cut out from a crack-free site in the thickness direction. Table 4 shows the results.

Comparative Example 6
The slurry prepared in Example 3 was pressure-injected into a mold cavity in the same manner as in Example 3, and wet-molded in an orientation magnetic field of 79.6 kA / m (1.0 kOe) to obtain an outer diameter of 24.5 mm × an inner diameter of 17.4 mm × A compact having a height of 30.0 mm was obtained. The density of the formed body was 4.32 g / cm ³ . This molded body was deoiled and sintered in the same manner as in Example 3, to obtain a sintered body having an outer diameter of 20.3 mm, an inner diameter of 15.2 mm and a height of 25.8 mm. The density of the sintered body was 7.59 g / cm ³ . This sintered body was subjected to a heat treatment at 500 ° C. × 2 hours. This sintered body was machined and finished to dimensions of 19.6 mm in outer diameter × 15.4 mm in inner diameter × 25.0 mm in height. After performing 4-pole magnetization, the surface magnetic flux density was measured. As shown in Table 4 , the peak value was lower than that in Example 3. When eight samples of 5 mm × 7 mm × 1 mm cut out from the sintered body were stacked in the thickness direction and the magnetic properties were measured, the results were lower than those of Example 3 as shown in Table 4 .

Example 8
22.00% Nd, 5.50% Pr, 5.00% Dy, 1.03% B, 0.08% Al, 1.00% Co, 0.12% Cu, 0.10% Ga, 0.09% O, 0.03% by mass % % of C, 0.015% of N, after the coarse powder for R-Fe-B permanent magnet having a composition the balance being Fe was charged into a jet mill was replaced with nitrogen gas, 6.4 × 10 ⁵ Pa (6.5 It was pulverized at a pressure of kgf / cm ² ) and at a feed rate of coarse powder of 20 kg / h. During the pulverization, a small amount of oxygen was introduced into the jet mill, and the oxygen concentration in the nitrogen gas was controlled at 0.080 to 0.120%. The particle size of the obtained fine powder was 5.0 μm. The composition of the fines is 22.00% Nd, 5.50% Pr, 5.00% Dy, 1.03% B, 0.08% Al, 1.00% Co, 0.12% Cu, 0.10% Ga, 0.48 % by mass %. % O, 0.06% C, 0.015% N, balance Fe.

This fine powder was mixed with mineral oil ("Super Sol PA30", manufactured by Idemitsu Kosan Co., Ltd.) to form a slurry. The mineral oil contained a 5% by mass sodium phosphite glycerin solution so that the ratio of sodium hypophosphite to the mineral oil was 0.2% by mass. The mass ratio of mineral oil to fine powder was 1: 3. As in Example 3, the obtained slurry was pressure-injected into a ring-shaped mold cavity to which an orientation magnetic field was applied in the radial direction, wet-molded, and had an outer diameter of 24.5 mm x an inner diameter of 17.4 mm x a height of 30.0 mm. mm was obtained. The density of the molded product was 4.45 g / cm ³ .

This compact was sintered at 1070 ° C. for 3 hours under a reduced pressure of 6.7 Pa (5 × 10 ⁻⁵ Torr) to obtain a sintered body having an outer diameter of 20.3 mm, an inner diameter of 15.1 mm and a height of 25.8 mm. The density of the sintered body was 7.61 g / cm ³ . The sintered body was subjected to a heat treatment at 550 ° C. × 2 hours. This sintered body was machined to a size of 19.6 mm in outer diameter × 15.4 mm in inner diameter × 25.0 mm in height, and was subjected to 8-pole magnetization. Table 4 shows the measurement results of the surface magnetic flux density. The cut out sample of the same size as the example 3 sintered body was measured magnetic properties were good as shown in Table 4. The Analysis of the composition of the sintered body, 22.00% by mass% based Nd, 5.50% of Pr, 5.00% of Dy, 1.03% of B, 0.08% of Al, 1.00% of Co, 0.12% of Cu, 0.10% Ga, 0.46% O, 0.06% C, 0.015% N, 0.02% P, and the balance Fe.

Comparative Example 7
The dry fine powder prepared in Example 8 was filled in the same mold cavity as in Example 8 without mixing with mineral oil, and was placed in an orientation magnetic field of 239 kA / m (3 kOe) at 7.8 × 10 ⁷ Pa (0.8 ton / cm). Molding was performed under the pressure of ² ) to produce a molded body having an outer diameter of 24.5 mm, an inner diameter of 17.4 mm, and a height of 30.0 mm. The density of the molded product was 3.78 g / cm ³ . This compact was sintered under a reduced pressure of 2.7 Pa (2 × 10 ⁻⁵ Torr) at 1070 ° C. for 3 hours to obtain a sintered body having an outer diameter of 20.1 mm × an inner diameter of 15.0 mm × a height of 25.9 mm. The density of the sintered body was 7.59 g / cm ³ . This sintered body was subjected to a heat treatment at 550 ° C. × 2 hours, and was then machined into dimensions of 19.6 mm in outer diameter × 15.4 mm in inner diameter × 25.0 mm in height. This was magnetized to 8 poles, and the surface magnetic flux density was measured along the magnetic poles in the axial direction. As shown in Table 4 , the result was lower than that of Example 8. When eight samples of 5 mm × 7 mm × 1 mm cut out from the sintered body were stacked in the thickness direction and the magnetic properties were measured, the results were lower than those of Example 8 as shown in Table 4 .

Comparative Example 8
The mold fine cavity of Example 8 was filled with the dry fine powder prepared in Example 8 from above without being mixed with mineral oil, and was placed in an orientation magnetic field of 318 kA / m (4 kOe) at 7.8 × 10 ⁷ Pa (0.8 on). / cm ² ) to produce a first molded body having an outer diameter of 24.5 mm × an inner diameter of 17.4 mm × a height of 10.0 mm. Next, the lower punch is lowered, and the first compact is filled with the dry fine powder again, and the pressure is 7.8 × 10 ⁷ Pa (0.8 ton / cm ² ), and the first compact is integrated with the first compact at the same volume. A second molded body (outer diameter 24.5 mm × inner diameter 17.4 mm × height 10.0 mm) was produced. Further, filling and molding were performed a third time in the same manner, and a third molded body having the same volume was integrally formed. The dimensions of the obtained integral molded body were 24.5 mm in outer diameter × 17.4 mm in inner diameter × 30.0 mm in height. The density of the formed body was 3.74 g / cm ³ .

This compact was sintered at 1070 ° C. for 3 hours under a reduced pressure of 6.7 Pa (5.0 × 10 ⁻⁵ Torr) to obtain a sintered body having an outer diameter of 20.0 mm × an inner diameter of 14.9 mm × a height of 26.1 mm. The density of the sintered body was 7.58 g / cm ³ . This sintered body was subjected to a heat treatment at 550 ° C. × 2 hours, and was then mechanically processed into dimensions of 19.6 mm in outer diameter × 15.4 mm in inner diameter × 25.0 mm in height. This was magnetized to eight poles, and the surface magnetic flux density was measured along the magnetic poles in the axial direction. As shown in Table 4 , the magnetic flux density was higher than Comparative Example 7 but lower than Example 8. When 8 pieces of 5 mm x 7 mm x 1 mm samples cut out from the sintered body were stacked in the thickness direction and the magnetic properties were measured, as shown in Table 4 , it was higher than Comparative Example 7, but Example 8 It was lower. Further, the surface magnetic flux density was locally reduced at the joint portion of the three-stage sintering of the sintered body, and the cogging characteristics when incorporated in the motor were worse than in Example 8.

Example 9
On a mass % basis, 20.50% Nd, 9.25% Pr, 0.25% Dy, 1.03% B, 0.08% Al, 2.00% Co, 0.10% Cu, 0.13% O, 0.04% C, A coarse powder for an R-Fe-B permanent magnet having a composition consisting of 0.02% of N and the balance of Fe is charged into a jet mill and purged with nitrogen gas, and then 6.9 × 10 ⁵ Pa (7.0 kgf / cm ^2). ) And a coarse powder feed rate of 20 kg / h. The obtained fine powder was directly collected in a mineral oil (“Super Sol PA30”, manufactured by Idemitsu Kosan Co., Ltd.) without being exposed to the air to form a slurry.

This mineral oil was preliminarily mixed with a 5% by mass sodium phosphite glycerin solution so that the ratio of sodium hypophosphite to the mineral oil was 0.2% by mass. The mass ratio of mineral oil to fine powder was 1: 3. The average particle size of the fine powder was 4.7 μm. The slurry thus prepared was injected under pressure into a mold having an angle θ of 45 ° between the axis of the slurry injection hole 5 and the radius of the mold core 4 shown in FIG. The strength of the radial orientation magnetic field applied to the cavity was 239 kA / m (about 3 kOe), and the slurry injection pressure was 2.9 × 10 ⁵ Pa (about 3 kgf / cm ² ). After the slurry injection, while maintaining the orientation magnetic field strength at 239 kA / m (about 3 kOe), wet molding was performed in a magnetic field at a pressure of 3.9 × 10 ⁷ Pa (about 0.4 ton / cm ² ), and the outer diameter was 25.3 mm × A compact having an inner diameter of 17.5 mm and a height of 21.8 mm was obtained. The density of the molded product was 4.40 g / cm ³ .

The molded body is subjected to a deoiling treatment at 180 ° C. for 4 hours under a reduced pressure of 6.7 Pa (about 5.0 × 10 ⁻² Torr), and then under a reduced pressure of 6.7 × 10 ⁻² Pa (about 5.0 × 10 ⁻⁴ Torr). At 1040 ° C. for 3 hours. The dimensions of the obtained sintered body were 20.6 mm in outer diameter × 15.3 mm in inner diameter × 18.8 mm in height, and the density was 7.56 g / cm ³ . The sintered body was subjected to a heat treatment at 480 ° C. × 2 hours. This sintered body was machined and finished to dimensions of outer diameter 20.1 mm × inner diameter 15.9 mm × height 17.2 mm. The unit weight (weight of sintered body after processing / weight of sintered body before processing × 100%) was 72.7%. The unit weight is sometimes called the processing rate.

The surface magnetic flux density B ₀ along the axial direction of the magnetic poles on the outer peripheral surface of the 4-pole magnetized ring magnet was measured with a probe of the Hall sensor. From the measurement results of the surface magnetic flux density B _0, the peak value of the surface magnetic flux density B ₀ (maximum value) and (minimum value of the maximum value -B ₀ of B ₀₎ variation [a surface magnetic flux density B ₀ / B maximum value of ₀ ] X 100 (%). The results are shown in Table 6 and FIG. In FIG. 7, the ordinate indicates the surface magnetic flux density B ₀ (T) along the magnetic pole in the axial direction of the ring magnet, and the abscissa indicates the distance (mm) of moving the probe along the axial direction of the ring magnet. . The distance H corresponds to the axial length of the ring magnet (17.2 mm). Table 6 As is apparent, the peak value of the surface magnetic flux density B ₀ is high, the variation of the surface magnetic flux density B ₀ was small.

Similarly the sintered body 20 produced cut out 4 mm × 7 mm × 1 mm sample 21b as shown in FIG. 3, was measured magnetic properties 8 layers of the sample 21b in the thickness direction, in Table 6 It had a high value as shown. Analysis of the composition of the sintered body, 20.50% of Nd in mass% basis, 9.25% of Pr, 0.25% of Dy, 1.03% of B, 0.08% of Al, 2.00% of Co, 0.10% of Cu, 0.15 % O, 0.06% C, 0.05% N, 0.018% P, balance Fe. In addition, when the sample 21b was subjected to line analysis by EPMA, a P peak was confirmed as shown in FIG. From FIG. 8, it can be seen that P exists mainly in the rare earth-rich phase at the crystal grain boundaries.

Example 10
The same coarse powder as in Example 9 was pulverized in the same manner as in Example 9 and recovered in mineral oil ("Super Sol PA30", manufactured by Idemitsu Kosan Co., Ltd.) to obtain a slurry. The mass ratio of mineral oil to fine powder was 1: 3. The average particle size of the obtained fine powder was 4.6 μm. This slurry was mixed with a 10% by mass sodium hypophosphite ethanol solution so that the ratio of sodium hypophosphite to mineral oil was 0.4% by mass. As in Example 9, this slurry was pressure-injected into a mold cavity having an angle θ of 30 ° between the axis of the slurry injection hole and the radius of the mold core, wet-molded in a magnetic field, and had an outer diameter of 25.3 mm. A molded body having an inner diameter of 17.5 mm and a height of 21.8 mm was obtained. The density of the formed body was 4.35 g / cm ³ . The number of molded bodies produced per hour was 123. The unit weight of the product was 72.9%.

This molded body was deoiled and sintered in the same manner as in Example 9 to obtain a sintered body having an outer diameter of 20.6 mm, an inner diameter of 15.3 mm and a height of 18.75 mm. The density of the sintered body was 7.55 g / cm ³ . This sintered body was subjected to a heat treatment at 480 ° C. × 2 hours. This sintered body was machined to a size of 20.1 mm in outer diameter × 15.9 mm in inner diameter × 17.2 mm in height. After similarly 4 poles as in Example 9 was measured for the surface magnetic flux density B ₀ along the pole axis direction, the high peak value of the surface magnetic flux density B ₀ As shown in Table 6 Indicated. When the variation of the surface magnetic flux density _{B0 in} the axial direction was calculated, it was small as shown in Table 6 .

A sample was cut out from the sintered body as shown in FIG. Table 6 shows the measurement results of the magnetic properties. Analysis of the composition of the sintered body showed that, on a mass % basis, 20.50% Nd, 9.25% Pr, 0.25% Dy, 1.03% B, 0.08% Al, 2.00% Co, 0.10% Cu, 0.16% % O, 0.07% C, 0.06% N, 0.037% P, balance Fe. Further, as a result of line analysis of the sintered body by EPMA, a peak of P was confirmed as shown in FIG.

Example 11
The slurry prepared in Example 9 was pressure-injected into a mold cavity in which the angle θ between the axis of the slurry injection hole and the radius of the mold core was 60 ° as in Example 9, and was wet-molded in a magnetic field. However, the dimensions of the cavity of the mold were changed. The intensity of the radial orientation magnetic field applied to the cavity was 398 kA / m (about 5 kOe), and the injection pressure was 5.9 × 10 ⁵ Pa (about 6 kgf / cm ² ). After the slurry injection, while maintaining the orientation magnetic field strength at 398 kA / m (about 5 kOe), wet molding was performed in a magnetic field at a pressure of 7.8 × 10 ⁷ Pa (about 0.8 ton / cm ² ), and the outer diameter was 33.4 mm × A molded body having an inner diameter of 24.3 mm and a height of 55.1 mm was obtained. The number of molded bodies produced per hour was 125. The density of the molded product was 4.45 g / cm ³ .

This molded body was deoiled and sintered in the same manner as in Example 9, to obtain a sintered body having an outer diameter of 27.4 mm, an inner diameter of 21.1 mm and a height of 47.4 mm. The density of the sintered body was 7.57 g / cm ³ . The sintered body was subjected to a heat treatment at 480 ° C. × 2 hours. The sintered body was machined to a size of 26.8 mm in outer diameter × 21.8 mm in inner diameter × 45.0 mm in height. The unit weight of the product was 75.5%. When the surface magnetic flux density was measured along the magnetic poles in the axial direction by performing 4-pole magnetization, the peak value and the variation were good as shown in Table 6 . When 8 samples of 4 mm × 7 mm × 1 mm cut out from the sintered body were stacked in the thickness direction and the magnetic characteristics were measured, the magnetic characteristics were high as shown in Table 6 .

Example 12
In the same manner as in Example 11, the slurry prepared in Example 11 was applied to a mold cavity to which an orientation magnetic field of 159 kA / m (about 2 kOe) was applied in the radial direction to 3.9 × 10 ⁵ Pa (about 4 kgf / cm ² ). And wet-molded in a magnetic field. 0.5 seconds after the start of the injection of the slurry, the intensity of the orientation magnetic field was increased to 318 kA / m (about 4 kOe). After the completion of the injection, wet molding was performed in a magnetic field while maintaining the magnetic field intensity. A compact having a size of mm × 54.8 mm in height was obtained. The density of the molded product was 4.45 g / cm ³ . The number of molded bodies produced per hour was 121.

This compact was deoiled and sintered in the same manner as in Example 9 to obtain a sintered body having an outer diameter of 27.4 mm, an inner diameter of 21.1 mm and a height of 47.1 mm. The density of the sintered body was 7.57 g / cm ³ . This sintered body was heat-treated in the same manner as in Example 9, and was machined to a size of 26.8 mm in outer diameter × 21.8 mm in inner diameter × 45.0 mm in height. The unit weight of the product was 6.0%. When the surface magnetic flux density _B0 was measured after the four-pole magnetization, the peak value and the variation were good as shown in Table 6 . When the magnetic characteristics of the sample cut out in the same manner as in Example 9 were measured, the sample had high values as shown in Table 6 .

Example 13
Similarly to Example 9, the slurry prepared in Example 9 was pressure-injected into a mold cavity having an angle θ of 15 ° between the axis of the slurry injection hole and the radius of the mold core, and wet-molded in a magnetic field. However, the dimensions of the cavity of the mold were changed. The intensity of the radial orientation magnetic field applied to the cavity was 223 kA / m (2.8 kOe), and the injection pressure was 3.9 × 10 ⁵ Pa (about 4 kgf / cm ² ). After the slurry injection, while maintaining the orientation magnetic field strength at 223 kA / m (2.8 kOe), wet molding was performed in a magnetic field at a pressure of 3.9 × 10 ⁷ Pa (about 0.4 ton / cm ² ). A molded body having a size of 11.1 mm and a height of 16.4 mm was obtained. The density of the molded product was 4.40 g / cm ³ . The number of molded articles produced per hour was 140.

This compact was deoiled and sintered in the same manner as in Example 9 to obtain a sintered body having an outer diameter of 14.6 mm, an inner diameter of 9.6 mm, and a height of 14.2 mm. The density of the sintered body was 7.58 g / cm ³ . The sintered body was subjected to a heat treatment at 480 ° C. × 2 hours. The sintered body was machined and finished to dimensions of 14.0 mm in outer diameter × 10.0 mm in inner diameter × 12.5 mm in height. The unit weight of the product was 69.8%. When the surface magnetic flux density was measured along the magnetic poles in the axial direction by performing 4-pole magnetization, the peak value and the variation were good as shown in Table 6 . When eight pieces of 3 mm × 7 mm × 1 mm samples cut out from the sintered body were stacked in the thickness direction and the magnetic properties were measured, the magnetic properties were high as shown in Table 6 .

Comparative Example 9
The same coarse powder as in Example 9 was pulverized in the same manner as in Example 9 and recovered in mineral oil ("Super Sol PA30", manufactured by Idemitsu Kosan Co., Ltd.) to obtain a slurry. The mass ratio of mineral oil to fine powder was 1: 3. The average particle size of the obtained fine powder was 4.6 μm. The mineral oil and the slurry were not mixed with a sodium hypophosphite glycerin solution or a sodium hypophosphite ethanol solution. This slurry was injected under pressure in the same manner as in Example 9, and wet-molded in a magnetic field. However, the filling property of the mold cavity was low due to poor fluidity of the slurry, and the dimensions of the obtained molded body were 25.3 mm in outer diameter × 17.5 mm in inner diameter × 19.5 mm in height. The density of the formed body was 3.85 g / cm ³ . The number of molded bodies produced per hour was 116.

This compact was deoiled and sintered in the same manner as in Example 9, to obtain a sintered body having an outer diameter of 20.3 mm, an inner diameter of 15.0 mm and a height of 15.9 mm. The density of the sintered body was 7.55 g / cm ³ . However, due to the poor filling property of the slurry, the upper punch side portion of the sintered body was deformed into an elliptical shape, and the sintered body did not become the product dimensions even when machined. The sintered body was subjected to a heat treatment at 480 ° C. × 2 hours, a sample of 4 mm × 7 mm × 1 mm was cut out from a portion other than the deformed portion, and eight samples were stacked in the thickness direction to measure magnetic properties. Table 6 shows the results. Analysis of the composition of the sintered body showed that, based on mass % , 20.50% Nd, 9.25% Pr, 0.25% Dy, 1.03% B, 0.08% Al, 2.00% Co, 0.10% Cu, 0.15% % O, 0.07% C, 0.05% N, balance Fe. The sintered body was subjected to line analysis by EPMA, and it was confirmed that there was no P peak as shown in FIG.

Comparative Example 10
The slurry prepared in Example 9 was pressure-injected into a mold cavity in which the axial direction of the slurry injection hole was the radial direction of the mold core (θ = 0 °) in the same manner as in Example 9, and wet-molded in a magnetic field. Thus, a molded product having an outer diameter of 25.3 mm, an inner diameter of 17.5 mm and a height of 21.7 mm was obtained. The density of the formed body was 4.38 g / cm ³ . The number of molded bodies produced per hour was 118. This compact was deoiled and sintered in the same manner as in Example 9, to obtain a sintered body having an outer diameter of 20.6 mm, an inner diameter of 15.3 mm and a height of 18.7 mm. The density of the sintered body was 7.56 g / cm ³ . In the sintered body, a longitudinal crack was generated at a position 180 ° opposite to the injection hole. Due to cracks, machining the sintered body did not reduce the product dimensions. Magnetic properties were measured by stacking eight 4 mm × 7 mm × 1 mm samples cut out from a crack-free site in the thickness direction. Table 6 shows the results.

Comparative Example 11
22.25% Nd, 10.00% Pr, 0.25% Dy, 1.03% B, 0.07% Al, 2.00% Co, 0.12% Cu, 0.10% Ga, 0.15% O, 0.03% by mass % % of C, 0.015% of N, after the coarse powder for R-Fe-B permanent magnet having a composition the balance being Fe was charged into a jet mill was replaced with nitrogen gas, 6.4 × 10 ⁵ Pa (6.5 The powder was finely ground at a pressure of kgf / cm ² ) and a feed rate of coarse powder of 30 kg / h. During the pulverization, a small amount of oxygen was introduced into the jet mill, and the oxygen concentration in the nitrogen gas was controlled at 0.080 to 0.120%. The particle size of the obtained fine powder is 4.8 μm, and its composition is 22.25% Nd, 10.00% Pr, 0.25% Dy, 1.03% B, 0.07% Al, 2.00% Co, based on mass % . 0.12% Cu, 0.10% Ga, 0.52% O, 0.06% C, 0.015% N, balance Fe.

The obtained dry fine powder was not mixed with mineral oil, filled into the same mold cavity as in Example 9 from above except that there was no slurry injection hole and the cavity depth was 1/3, and 398 kA / m (about A first compact was produced at a pressure of 7.8 × 10 ⁷ Pa (about 0.8 ton / cm ² ) in an orientation magnetic field of 5 kOe). Next, the lower punch is lowered, and the first compact is filled with the dry fine powder again, and the pressure is 7.8 × 10 ⁷ Pa (0.8 ton / cm ² ), and the first compact is integrated with the first compact at the same volume. A second molded body was produced. Further, filling and molding were performed a third time in the same manner, and a third molded body having the same volume was integrally formed. The dimensions of the obtained integral molded body were 25.3 mm in outer diameter × 17.5 mm in inner diameter × 21.5 mm in height. The density of the molded product was 3.80 g / cm ³ . The number of molded bodies produced per hour was 48.

This compact was sintered under a reduced pressure of 6.7 × 10 ^-3 Pa (about 5 × 10 ^-5 Torr) at 1070 ° C. for 3 hours to obtain a sintered body having an outer diameter of 20.7 mm × an inner diameter of 15.4 mm × a height of 18.8 mm. Got. The density of the sintered body was 7.52 g / cm ³ . This sintered body was subjected to a heat treatment at 480 ° C. × 2 hours. The dimensions were 20.1 mm in outer diameter, 15.9 mm in inner diameter, and 17.2 mm in height by mechanical processing. The unit weight of the product was 72.3%. The sintered body was magnetized in four poles, and the surface magnetic flux density was measured along the magnetic poles in the axial direction.As shown in Table 6 and FIG. 11, the peak value was lower than that in Example 9 and the variation was three-staged. Was large due to the influence of the joint. When eight samples of 4 mm × 7 mm × 1 mm cut out from the sintered body were stacked in the thickness direction and the magnetic characteristics were measured, the results were lower than those of Example 9 as shown in Table 6 . Further, the surface magnetic flux density B ₀ of the sintered body was locally low at the joint part of the three-stage lamination molding, and the cogging when incorporated in the motor was larger than that of Example 9.

Comparative Example 12
The dry fine powder was not mixed with the mineral oil, but was filled from above into the same mold cavity as Comparative Example 11 except that there was no slurry injection hole and the cavity depth was 1/3. The first compact was produced at a pressure of 7.8 × 10 ⁷ Pa (about 0.8 ton / cm ² ) in an orientation magnetic field of 478 kA / m (about 6 kOe). Next, the lower punch is lowered, and the first compact is filled with the dry fine powder again, and the pressure is 7.8 × 10 ⁷ Pa (0.8 ton / cm ² ), and the first compact is integrated with the first compact at the same volume. A second molded body was produced. Further, filling and molding were performed a third time in the same manner, and a third molded body having the same volume was integrally formed. The dimensions of the obtained integral molded body were 33.4 mm in outer diameter × 24.3 mm in inner diameter × 54.6 mm in height. The density of the molded product was 3.75 g / cm ³ . The number of molded bodies produced per hour was 45.

This compact was sintered under a reduced pressure of 6.7 × 10 ^-3 Pa (about 5 × 10 ^-5 Torr) at 1070 ° C. for 3 hours to obtain a sintered body having an outer diameter of 27.3 mm × an inner diameter of 21.4 mm × a height of 47.5 mm. Got. The density of the sintered body was 7.51 g / cm ³ . This sintered body was subjected to a heat treatment at 480 ° C. × 2 hours. Further, the dimensions were 26.8 mm in outer diameter × 21.8 mm in inner diameter × 45.0 mm in height by mechanical processing. The unit weight of the product was 80.1%. This was magnetized in four poles, and the surface magnetic flux density was measured along the magnetic poles in the axial direction. As shown in Table 6 , the peak value was lower than in Example 11 and the dispersion was large. When eight 4 mm × 7 mm × 1 mm samples cut out from the sintered body were stacked in the thickness direction and the magnetic properties were measured, the results were lower than those of Example 11 as shown in Table 6 . Further, the surface magnetic flux density B ₀ of the sintered body was locally low at the joint portion formed by the three-stage lamination, and the cogging when incorporated in the motor was larger than that of Example 11.

Comparative Example 13
A master alloy having a composition consisting of 30.0% Nd, 0.90% B, 5.00% Co, 0.20% Ga, and the balance Fe on a mass % basis was put into a quartz nozzle having a hole at the bottom, and the inside of the quartz nozzle was 0.4 mm. The pressure was reduced to Pa (about 3 × 10 ⁻³ Torr). The master alloy is melted by high frequency in an atmosphere in which Ar gas is introduced until a pressure of 5.3 × 10 ⁴ Pa (about 400 Torr) is obtained, and the obtained molten metal is melted at an Ar pressure of 270 g / cm ³ at a peripheral speed of 30 m. / squirted onto a rotating Be-Cu roll. As a result, a ribbon-shaped alloy having an average thickness of 30 μm was obtained.

The ribbon-shaped alloy was coarsely pulverized to 500 μm or less, and the obtained coarse powder was mixed with 0.2% by mass of scale graphite and 0.3% by mass of a bismuth borosilicate-based amorphous glass having a low melting point. The resulting coarse powder mixture was cold pressed at a pressure of 4.9 × 10 ⁸ Pa (about 5 ton / cm ² ) to obtain a green compact having a density of 5.8 g / cm ³ . This green compact is hot-pressed at 740 ° C. and 2 × 10 ⁸ Pa (2 ton / cm ² ) in a vacuum of 0.67 Pa (5.0 × 10 ^-3 Torr), and sintered with a density of 7.40 g / cm ^3. Body. This sintered body was further subjected to hot plastic working at 740 ° C. in a vacuum of 0.67 Pa (5.0 × 10 ⁻³ Torr) to have an outer diameter of 22.0 mm × inner diameter of 14.5 mm × height of 48.0 mm and a bottom thickness of 10 mm. mm cup body. To impart radial anisotropy, the number of hot plastic workings per hour was as small as three. The bottom of the cup was cut off by machining. The end where a crack occurred on the side opposite to the bottom was also cut. The inner and outer circumferences of the obtained ring were machined to obtain product dimensions of 20.1 mm in outer diameter × 15.9 mm in inner diameter × 28.0 mm in height. The unit weight of the hot-worked product was as low as 17.0%.

Quadrupole magnetization was performed on this ring magnet in the same manner as in Example 9. When the surface magnetic flux density was measured, as shown in Table 6 and FIG. 12, the peak value was lower than that in Example 9, the surface magnetic flux density at both ends in the axial direction was lower, and the variation in the surface magnetic flux density was larger. As a result of measuring the magnetic properties of the sample of 4 mm × 7 mm × 1 mm cut out from the product, as shown in Table 6 , the result was lower than that of Example 9. The cogging when the product was incorporated in the motor was larger than that in Example 9.

Comparative Example 14
A ribbon was prepared in the same manner as in Comparative Example 13 from a mother alloy having a composition of 28.0% Nd, 0.50% Ce, 0.90% B, 3.0% Co, 0.15% Ga, and the balance Fe on a mass % basis. The ribbon was pulverized into coarse powder. A green compact of 5.7 g / cm ³ was prepared from the coarse powder in the same manner as in Comparative Example 13 and hot-pressed to a density of 7.30 g / cm ³ at 720 ° C. in a vacuum of 0.4 Pa (3 × 10 ⁻³ Torr). did. The obtained pressed body was subjected to hot plastic working at 720 ° C. in a vacuum of 0.4 Pa (3 × 10 ⁻³ Torr) in the same manner as in Comparative Example 13 to obtain an outer diameter of 30.0 mm × inner diameter of 19.5 mm × height of 65.0 mm. A cup with a bottom thickness of 10 mm was obtained. The number of hot plastic working per hour was 4.

The bottom of the cup was cut off by machining. The end where a crack occurred on the side opposite to the bottom was also cut. The inner and outer circumferences of the obtained ring were machined to obtain product dimensions of 26.8 mm in outer diameter × 21.8 mm in inner diameter × 45.0 mm in height. The unit weight of the hot-worked product was as low as 29.1%. This product was subjected to 4-pole magnetization in the same manner as in Example 11. Was subjected to measurement of the surface magnetic flux density, as shown in Table 6, the peak value than in Example 11 is low, a low surface magnetic flux density B ₀ in the axial direction end portions, the variation of the surface magnetic flux density B ₀ was great. As a result of the measurement of the magnetic properties of the sample of 4 mm × 7 mm × 1 mm cut out from the product, the result was lower than that of Example 11 as shown in Table 6 . The cogging when incorporated in the motor was greater than in Example 11.

INDUSTRIAL APPLICABILITY The present invention can be used for a high-performance radially anisotropic sintered R-Fe-B permanent magnet and a method for producing the same. In particular, it can be used for a high-performance radially anisotropic sintered R-Fe-B permanent magnet excellent in uniformity of surface magnetic flux density and an efficient manufacturing method thereof.

Is a graph showing the relationship between the content of the coercive force iHc and P of sintered permanent magnets. 1 is a schematic view showing a molding apparatus for performing the method of the present invention. (a) is a schematic perspective view showing a state of cutting a sample from a ring-shaped sintered body, and (b) is a cross-sectional view showing a state of cutting a sample from a ring-shaped sintered body. 9 is a graph showing an EPMA line analysis result of the sintered body of Example 3. 14 is a graph showing an EPMA line analysis result of the sintered body of Example 4. 14 is a graph showing an EPMA line analysis result of the sintered body of Comparative Example 4. 30 is a graph showing the surface magnetic flux density distribution of the ring magnet of Example 9. 31 is a graph showing an EPMA line analysis result of the sintered body of Example 9. 31 is a graph showing an EPMA line analysis result of the sintered body of Example 10. 14 is a graph showing an EPMA line analysis result of the sintered body of Comparative Example 9. 21 is a graph showing the surface magnetic flux density distribution of the ring magnet of Comparative Example 11. 14 is a graph showing the surface magnetic flux density distribution of the ring magnet of Comparative Example 13.

Explanation of reference numerals

1 magnetic field generating coil, 2 die case, 3 cylindrical die member, 4 core,
5 slurry injection hole, 6 cavity, 7 magnetic field line, 9 lower punch,
10 Upper punch, 11 Vertical section of molding equipment, 12 Cross section of mold and its enlarged view,
20 Sintered body, 21 Sample before cutting, 21b sample

Claims (25)

And 27 to 33.5% of R in mass% basis (at least one rare earth element R containing Y), and 0.5% to 2% of B, a 0.002 to 0.15% of N, and O of 0.25%, 0.15% A sintered permanent magnet having a composition comprising the following C, 0.001 to 0.05% P, and the balance Fe, and having a coercive force iHc of 1 MA / m or more. 2. The sintered permanent magnet according to claim 1, wherein P is 0.003 to 0.05% by mass. 3. The sintered permanent magnet according to claim 2, wherein P is 0.008 to 0.05% by mass. The sintered permanent magnet according to any one of claims 1 to 3, wherein a part of Fe is 0 to 1% Nb, 0.01 to 1% Al, and 0 to 5% Co based on mass %. , 0.01-0.5% of Ga and, sintered permanent magnet is characterized that you have been substituted by at least one selected from the group consisting of 0 to 1% of Cu. In sintered permanent magnet according to claim 4, sintered permanent magnet Nb is characterized by 0.05 to 1% by mass Rukoto. The sintered permanent magnet according to claim 4 or 5, wherein Al is 0.01 to 0.3% by mass . In sintered permanent magnet according to any one of claims 4-6, sintered permanent magnet Co is characterized by 0.3 to 5% by mass Rukoto. In sintered permanent magnet according to claim 7, sintered permanent magnet Co is characterized by 0.3 to 4.5% by mass Rukoto. The sintered permanent magnet according to any one of claims 4 to 8, wherein Ga is 0.03 to 0.4 mass%. The sintered permanent magnet according to any one of claims 4 to 9, wherein Cu is 0.01 to 1% by mass. 11. The sintered permanent magnet according to claim 10, wherein Cu is 0.01 to 0.3% by mass. The sintered permanent magnet according to any one of claims 1 to 11, wherein O is 0.05 to 0.25% by mass. The sintered permanent magnet according to any one of claims 1 to 12, wherein C is 0.01 to 0.15% by mass. The sintered permanent magnet according to any one of claims 1 to 13, which has a ring shape having an outer diameter of 10 to 100 mm, an inner diameter of 8 to 96 mm, and a height of 10 to 70 mm, and an outer peripheral surface. A plurality of magnetic poles extending in the axial direction of the sintered permanent magnet. The sintered permanent magnet according to claim 14, wherein the surface magnetic flux density B on the magnetic pole in the axial direction of the ring. ₀ Distribution is B ₀ A sintered permanent magnet characterized by being in the range of 92.5% or more of the maximum value. The sintered permanent magnet according to claim 15, wherein the surface magnetic flux density B ₀ A sintered permanent magnet characterized in that the variation of the sintered type is within 5%. 17. The sintered permanent magnet according to claim 1, wherein said R is 27 to 32% by mass. 17. The sintered permanent magnet according to claim 1, wherein the R is more than 32% by mass and 33.5% by mass or less. R of more than 32% and 33.5% or less (R is at least one rare earth element including Y), 0.5 to 2% of B, O of more than 0.25% and 0.6% or less, and 0.01 to 0.15% by mass. % C, 0.002 to 0.05% N, 0.001 to 0.05% P, and the balance Fe, with an outer diameter of 10 to 100 mm, an inner diameter of 8 to 96 mm, and a 10 to 70 mm. mm, has a magnetic anisotropy in the circumferential direction of the ring, and has a surface magnetic flux density B on a magnetic pole in the axial direction of the ring. ₀ Distribution is B ₀ A sintered permanent magnet characterized by being in the range of 92.5% or more of the maximum value. The sintered permanent magnet according to claim 19, wherein the surface magnetic flux density B ₀ A sintered permanent magnet characterized in that the variation of the sintered type is within 5%. (a) crushing the rare-earth magnet material as fine powder, directly recovering it in mineral oil, synthetic oil or a mixed oil thereof to form a slurry, (b) press-injecting the slurry into a mold cavity, Wet molding in a magnetic field in (c) heating the obtained molded body under reduced pressure to remove the mineral oil, the synthetic oil or a mixed oil thereof from the molded body, (d) the molded body A sintered permanent magnet for sintering in a vacuum, wherein the axial direction of a hole opened in the cavity of the mold to inject the slurry under pressure is from the center of the center core of the mold. A method for manufacturing a sintered permanent magnet, wherein the permanent magnet is not provided. 22. The method for producing a sintered permanent magnet according to claim 21, wherein the oxygen content of the fine powder is more than 0.25% by mass and 0.6% by mass or less. (a) crushing the rare-earth magnet material as fine powder, directly recovering it in mineral oil, synthetic oil or a mixed oil thereof to form a slurry, (b) press-injecting the slurry into a mold cavity, Wet molding in a magnetic field in (c) heating the obtained molded body under reduced pressure to remove the mineral oil, the synthetic oil or a mixed oil thereof from the molded body, (d) the molded body Sintering in a vacuum, comprising mixing sodium hypophosphite as a fluidity improver with said mineral oil, synthetic oil or a mixture thereof. A method for producing a permanent magnet. (a) crushing the rare-earth magnet material as fine powder, directly recovering it in mineral oil, synthetic oil or a mixed oil thereof to form a slurry, (b) press-injecting the slurry into a mold cavity, Wet molding in a magnetic field in (c) heating the obtained molded body under reduced pressure to remove the mineral oil, the synthetic oil or a mixed oil thereof from the molded body, (d) the molded body A sintered type permanent magnet for sintering in a vacuum, wherein the axial direction of a hole opened in the cavity of the mold for injecting the slurry under pressure is from the center of the center core of the mold. A method for producing a sintered permanent magnet, wherein said method is characterized in that sodium hypophosphite is mixed as a fluidity improver with said mineral oil, synthetic oil or a mixed oil thereof. 25. The method for producing a sintered permanent magnet according to claim 23, wherein sodium hypophosphite is added as a solution of glycerin or ethanol.