JPH0799107A - Manufacture of rare earth permanent magnet - Google Patents

Abstract

PURPOSE:To prevent the progress of oxidation in manufacture process and obtain uniform density in a molded body by mixing a specified powder for a rare earth permanent magnet, mineral oil or synthetic oil, and extrusion- molding this mixture, and applying a magnetic field so as to give anisotropy, and then, sintering it. CONSTITUTION:Powder for an RCo5, R2C)17, or R-Fe-B rare earth magnetic magnet and a certain kind of mineral oil or synthetic oil are mixed, and this mixture is extrusion-molded. The manufacture of a uniform molded body 1 without dispersion in density is possible by extrusion-molding the raw material 6 being mixed equally, with its mixture rate controlled strictly, by means of mold 7 under a specified condition. For this, there is necessity to manage the quantity of powder for a rare earth magnet within the mixture in the range of 50-90%, and also the addition of an organic coupling agent to material mixture is effective to improvement of the strength of the molded body. The amount of addition is 0.1-5wt.% of the powder for a rare earth magnet.

Description

Detailed Description of the Invention

[0001]

The present invention relates to R-Co ₅ system, R ₂ -C
The present invention relates to a method for producing a rare earth sintered magnet of O ₁₇ system and R-Fe-B system (R is one or more of rare earth elements including Y).

[0002]

2. Description of the Related Art Sintered rare earth magnets dissolve raw metal,
It is manufactured by crushing, molding, sintering, heat treating, and processing an ingot obtained by pouring molten metal into a mold. Alternatively, it is produced by producing a raw material powder by a so-called reduction diffusion method in which a rare earth oxide is reduced with a reducing agent, pulverizing the raw material powder, and treating the raw material powder in the same steps as described above. The crushing is performed by a jet mill crushing method in which particles are made to collide with each other in an inert high-pressure gas atmosphere to obtain a dry powder.
It is generally carried out by a wet pulverization method in which a raw material powder is pulverized in an organic solvent and then the organic solvent is dried to obtain a dry powder using a rumill, a vibration mill or the like. In molding the dry powder, a method is used in which a predetermined amount of dry powder is weighed, and this is put into the mold cavity, or is put into the mold cavity by a scraping method using a feed box or the like, After powdering, an orientation magnetic field is applied to perform molding. In some cases, a method may be adopted in which the dry powder is fed into the cavity to which a magnetic field has been applied in advance by the above-mentioned method, and molding is performed.

In recent years, the use of rare earth sintered magnets has been remarkable in this field in accordance with the demand for miniaturization and high performance of motors. The advantage of using the rare earth sintered magnet is that the magnet has a thin structure due to its high residual magnetic flux density and coercive force, which enables the motor to be made smaller and lighter. For this reason, demand for thin-walled ring-shaped rare earth sintered magnets is increasing, and this trend is expected to continue in the future.

As a method for producing a thin ring-shaped rare earth sintered magnet, for example, Japanese Patent Laid-Open Nos. 1-027208 and 1076 are available.
46, 117003, JP-A-2-03703, 272.
711 and the like, a manufacturing method in the case of imparting anisotropy in the radial direction is proposed. In these, finely pulverized dry powder is powdered and molded in the mold cavity by the general method described above. However, in such a conventional manufacturing method, since the molded body is thin, the space between the mold cavities is narrow, and it is difficult to uniformly fill the raw material dry powder deep into the cavity. There was a problem that cracks and uneven density occurred. The non-uniformity of the compact density causes cracking and material deformation at the sintering stage.
It causes variations in magnetic properties. Further, in the conventional manufacturing method shown as an example above, since fine powder for rare earth permanent magnet that is chemically very active is powdered and molded in a dry powder state, oxidation progresses in the process, and magnetic properties There was a problem of causing deterioration.

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made diligent studies to solve the above-mentioned problems of the conventional method for producing a thin ring-shaped rare earth sintered magnet, and as a result, the progress of oxidation during the production process was almost eliminated. The present invention has been completed by finding a method for producing a molded product having a uniform and uniform molded product density.

[0006]

The first essential point of the present invention for producing a thin-walled ring-shaped molded product having a uniform density is the RCo ₅ system, R ₂ Co ₁₇ system or R-Fe-B system. The purpose is to mix fine powders for rare earth permanent magnets with a certain kind of mineral oil or synthetic oil, and to extrude this mixture. By extruding a raw material mixture in which the mixing ratio is strictly controlled and uniformly mixed from a mold under a predetermined condition, it is possible to manufacture a uniform molded body without variations in the density of the molded body. For this purpose, it is necessary to control the amount of the fine powder for rare earth magnets in the mixture within the range of 50 to 90% by weight. When the amount of the fine powder is less than 50%, the amount of the mineral oil or the synthetic oil as the solvent is too large, and even if the mixture is homogeneously mixed in the initial mixing stage, the fine powder and the solvent can be mixed in a short time. And the concentration of fine powder in the mixture becomes non-uniform, which causes variation in the density of the molded body in the extrusion molding process. On the other hand, when the amount of the fine powder is more than 90%, the amount of the solvent, that is, the mineral oil or the synthetic oil, is too small, so that the extrusion is not smoothly performed, which causes variations in the density of the molded body. The method for mixing the fine powder for rare earth magnets and the mineral oil or synthetic oil as the solvent is not particularly limited, and a predetermined amount of the fine powder and the solvent are weighed and mixed with a V-type mixer, mixer, kneader, etc. be able to. Alternatively, the fine powder discharge port of the jet mill pulverizer and these mixers may be directly connected to collect and mix a predetermined amount of fine powder with a predetermined amount of solvent in the mixer. Furthermore, it is also possible to prepare a mixed raw material by weighing a predetermined amount of the rare earth permanent magnet coarse powder and the above solvent, and wet pulverizing these with a vibration mill, a ball mill, an attritor, or the like. In order to maintain the uniformity of these raw material mixtures, it is desirable to adopt a method in which a stirring tank is provided near the raw material feeding part of the extrusion molding machine and the raw material mixture is fed into the extrusion molding machine while being uniformly stirred.

The second essential point of the present invention is that mineral oil or synthetic oil is used as a solvent constituting the raw material mixture. These have extremely low water content and oxygen content as compared with general organic solvents, and coat the surface of the fine powder for rare earth permanent magnets to shield them from the atmosphere. For this reason, the progress of oxidation of the raw material mixture using these as solvents becomes extremely small as compared with the case where dry powder is handled in the atmosphere. Furthermore, the effect of mineral oil or synthetic oil as a solvent is not limited to this,
The frictional force between the mold and the molded body during extrusion molding is reduced, and smooth molding is supported. This has a great effect on making the density of the molded body uniform. In addition, due to the lubricating effect of the mineral oil or the synthetic oil remaining inside the molded body, the orientation of the fine powder when a magnetic field is applied, which will be described later, is promoted and a high orientation is obtained. However, the mineral oil or synthetic oil used as a solvent has a distillation point of 400 ° C or higher and a kinematic viscosity of 10 cst at room temperature.
Limited to: If the fractional point and the kinematic viscosity are larger than these values, the desolvation treatment before the sintering is not performed smoothly, and the amount of residual C in the sintered body increases, resulting in good magnetic properties. I can't.

The molding machine for extrusion-molding the above raw material mixture to produce a molded body is not particularly limited, and the extrusion system can be selected from various types such as a screw type and a piston type. The extrusion speed and pressure are not particularly limited. However, when extrusion molding the above raw material mixture prepared for a rare earth permanent magnet,
It is necessary to set the density of the molded body to 2.0 to 5.0 g / cc, and in order to keep the density of the molded body within this range, the conditions of variable factors such as the extrusion speed and pressure of the extrusion molding machine must be set. I have to. Molded product density is 2.0g / cc
If it is smaller than the above range, the strength of the molded body is lowered. On the other hand, when the density of the molded body is larger than 5.0 g / cc, the degree of orientation when a magnetic field is applied does not increase and good magnetic properties cannot be obtained.

When the compact density is within the above range, the addition of an organic binder to the raw material mixture is effective for improving the compact strength. Typical examples of the organic binder include, but are not limited to, PVA, diethylene glycol, and methyl cellulose. The amount added is 0.1 to 5% by weight of the fine powder for rare earth permanent magnets. If the added amount is less than 0.1%, the effect as a binder is small and the strength of the molded body is not improved. 5 added
When it is more than 0.1%, a small amount is left even in the treatment with the organic binder, resulting in deterioration of magnetic properties.

An orientation magnetic field is applied to the molded product molded by extrusion to impart anisotropy. The magnetic field may be applied by applying a static magnetic field, applying a pulse magnetic field, or a combination of both. Further, the number of times of application can be once or more than once as necessary. The direction of imparting anisotropy can be various depending on the shape of the orientation yoke and the combination of the coils. Incidentally, when the density of the compact formed by extrusion molding of the rare earth permanent magnet is set within the range shown above, the strength of the orientation magnetic field needs to be 5 KOe or more. When the orientation magnetic field strength is less than 5 KOe, a sufficient degree of orientation cannot be obtained, and the residual magnetic flux density Br is lowered.
1 and 2 show a representative example of the oriented magnetic circuit according to the embodiment of the present invention.

Solvents such as mineral oil and synthetic oil and an organic binder remain inside the molded article produced by the above method. These molded bodies were sintered at room temperature to a sintering temperature of 1000 to 12
When the temperature rises rapidly to 00 ° C., the internal temperature of the molded body rises sharply, and the solvent or organic binder remaining in the molded body reacts with the rare earth element in the molded body to form rare earth carbide. Therefore, generation of a liquid phase in a sufficient amount for sintering is hindered, and a sintered body having a sufficient density cannot be obtained, which may lead to deterioration of magnetic characteristics. To prevent this, a temperature of 50
It is desirable to carry out a desolvation / deorganization binder treatment in which the temperature is kept at -500 ° C and the pressure is 10 ^-1 torr or less for 30 minutes or more. By this treatment, the solvent and organic binder remaining in the molded body can be sufficiently removed. In addition, holding is 50
It does not have to be one point and may be two or more points as long as it is in the temperature range of up to 500 ° C. Further, at a pressure of 10 ^-1 torr or less, the temperature rising rate from room temperature to 500 ° C is 10 ° C / min
Hereinafter, the temperature of 50 to 500 can be obtained even by performing desolvent treatment and deorganic binder treatment at preferably 5 ° C./min or less.
It is possible to obtain the same effect as the treatment of holding for 30 minutes or more under the condition of ° C and pressure of 10 ^-1 torr or less.

[0012]

EXAMPLES The present invention will be specifically described below with reference to examples, but the contents of the present invention are not limited thereto. (Example 1) Sm 36.5% in weight percentage, Co63.
The SmCo ₅ rare earth raw material coarse powder having a composition of 5% was jet-milled in an N ₂ gas atmosphere to have an average particle size of 5.0 μm.
m of fine powder. This fine powder 8 kg has a fractionation point of 200 to 3
2 Kg of mineral oil (manufactured by Idemitsu Kosan, trade name MC, OIL, P-02) having a kinematic viscosity of 2.0 cst at 00 ° C. and room temperature was mixed to prepare a mixture. This mixture was extrusion-molded by the extruder shown in FIG. 1 and cut into a molded body. The density of the molded body is 3.
It was 0 g / cc. Similarly, an orientation pulse magnetic field of 7 KOe was applied to the molded body by the orientation magnetic circuit shown in FIG.
It imparted radial anisotropy. Next, 5 × 10 ^{-2 on the} molded body
After demineralizing oil treatment at 350 ° C. for 1 hour under a pressure of torr, sintering was performed at 1135 ° C. for 2 hours in an Ar gas atmosphere. The size and shape of the sintered body were good. Further, the sintered body was heat-treated in an Ar gas atmosphere at 830 ° C. for 1 hour. After machining, the surface magnetic flux density was measured, and good values as shown in Table 1 were obtained.

(Example 2) Sm 26.0 by weight percentage
%, Fe 13.5%, Cu 4.8%, Zr 2.2%, C
Sm ₂ Co ₁₇ rare earth raw material coarse powder having a composition of 3.5% was ball-milled in toluene and dried in an Ar gas atmosphere to obtain fine powder having an average particle size of 5.2 μm.
To 8.2 kg of this fine powder, 1.8 kg of a mineral oil having a fractionation point of 200 to 400 ° C. and a kinematic viscosity at room temperature of 5.0 cst (manufactured by Idemitsu Kosan, trade name MC, OIL, P-05) and an organic binder A mixture was prepared by mixing 40 g of diethylene glycol. This mixture was extrusion-molded by the extruder shown in FIG. 1 and cut into a molded body. The density of the molded body was 3.3 g / cc. An oriented static magnetic field of 8 KOe was applied to this molded body in the same manner as in the oriented magnetic circuit shown in FIG. 1 to impart anisotropy in the radial direction. Next, the molded body was subjected to demineralized oil and deorganic binder treatment at a temperature rising rate from room temperature to 500 ° C. of 5 ° C./min under a pressure of 5 × 10 ⁻² torr, and then 1200 pressure was applied at the same pressure. The temperature was raised to 30 ° C. at a heating rate of 30 ° C./min, and the temperature was maintained for 3 hours for sintering. The size and shape of the sintered body were good. The sintered body was subjected to solution treatment at 1180 ° C. for 4 hours and aging treatment at 750 ° C. for 20 hours in an Ar gas atmosphere. After machining, the surface magnetic flux density was measured, and good results as shown in Table 1 were obtained.

(Example 3) The raw material mixture prepared in Example 2 was extrusion-molded by the extruder shown in FIG. 1 and cut into a molded body. The compact density in this case was 3.5 g / cc. This molded body was subjected to 1 by the orientation magnetic circuit shown in FIG.
Anisotropy was imparted by applying an orientation pulse magnetic field of 0KOe. The molded body was subjected to demineralized oil, deorganic binder treatment, sintering, solution treatment and aging treatment under the same conditions as in Example 2. The size and shape of the sintered body were good. When the surface magnetic flux density was measured after machining, good results as shown in Table 2 were obtained as the peak value.

(Comparative Example 1) The raw material mixture prepared in Example 1 was extrusion-molded by the extrusion molding machine shown in FIG. 1 and cut into a molded body. In this case, by adjusting the extrusion pressure and speed of the extruder, the density of the obtained molded product is 1.5.
It was g / cc. Then, an anisotropic pulse magnetic field of 7 KOe was applied to this compact by the same orientation magnetic circuit as shown in FIG. 1 to impart anisotropy. In this process, the compact had a weak strength and was damaged. I couldn't. (Comparative Example 2) The raw material mixture produced in Example 2 was extrusion-molded by the extrusion molding machine shown in FIG. 1 and cut into a molded body.
In this case, by adjusting the conditions of the extruder,
The density of the obtained molded body was 5.5 g / cc. 8 KOe was applied to this molded body by the orientation magnetic circuit shown in FIG.
A static magnetic field for orientation was applied to impart anisotropy in the radial direction. The molded body was subjected to demineralized oil, deorganic binder treatment, sintering, solution treatment and aging treatment under the same conditions as in Example 2. After machining to the same dimensions as in Example 2, the surface magnetic flux density was measured, and as shown in Table 1, the value was significantly lower than the value in Example 2. (Comparative Example 3) The raw material mixture produced in Example 2 was extruded by the extrusion molding machine shown in FIG. 1 and cut into a molded body.
The density of the molded body was 3.3 g / cc. An oriented static magnetic field of 4 KOe was applied to the molded body in the same manner as in the oriented magnetic circuit shown in FIG. 1 to impart radial anisotropy. The molded body was subjected to demineralized oil, deorganic binder treatment, sintering, solution treatment and aging treatment under the same conditions as in Example 2. After machining to the same dimensions as in Example 2, the surface magnetic flux density was measured, and as shown in Table 1, the value was significantly lower than the value in Example 2.

(Example 4) Nd 30.0 by weight percentage
%, Pr1.0%, Dy0.75%, B1.0%, Nb
Nd having a composition of 0.3%, Al 0.2% and balance Fe
-Fe-B type rare earth raw material coarse powder is jet mill pulverized in an N ₂ gas atmosphere, and a fractionation point of 200 is obtained at the fine powder discharge port of the pulverizer.
Install a container filled with mineral oil (made by Idemitsu Kosan Co., Ltd., trade name MC, OIL, P-02) with a kinematic viscosity of 2.0 cst at room temperature to 300 ° C., and pulverize the fine powder directly in a N ₂ gas atmosphere. It was collected in oil to give a mixture. The weight ratio of the fine powder in the mixture of the mineral oil and the fine powder was 85%. The average particle size of the fine powder was 4.0 μm. This mixture was extrusion-molded by the extruder shown in FIG. 1 and cut into a molded body. The density of the molded product was 2.2 g / cc. In this molded body,
Similarly, in the orientation magnetic circuit shown in FIG. 1, an orientation pulse magnetic field of 6 KOe was applied to impart anisotropy in the radial direction. Then, the molded body is heated from room temperature to 500 at a pressure of 3 × 10 ^-2 torr.
Demineralized oil treatment with a heating rate of 3 ℃ / min up to ℃, and then at the same pressure up to 1100 ℃ at 20 ℃ / min
The temperature was raised at a heating rate of, and the temperature was maintained for 2 hours for sintering. The size and shape of the sintered body were good. Sintered body is Ar
Heat treatments at 900 ° C. × 1 hour and 580 ° C. × 1 hour were performed once in a gas atmosphere. After machining, the surface magnetic flux density was measured, and good values as shown in Table 1 were obtained.

(Example 5) Nd 27.0 by weight percentage
%, Pr2.0%, Dy2.5%, B1.0%, Nb
0.5%, Al0.2%, Co2.5%, Ga0.1
%, The rest of the Nd-Fe-B-based rare earth raw material coarse powder having a composition of Fe was oscillated by oscillating milling in n-hexane.
After drying in a gas atmosphere, fine powder having an average particle size of 4.3 μm was obtained. This fine powder 7.0 kg has a distillation point of 200-300.
Synthetic oil with a kinematic viscosity of 1.0 cst at room temperature at room temperature (Idemitsu Kosan, product name DN, roll oil, AL-35) 3.0K
g and 140 g of organic binder diethylene glycol were mixed to form a mixture. This mixture was extrusion-molded by the extruder shown in FIG. 1 and cut into a molded body. The density of the molded body was 4.0 g / cc. An orientation pulse magnetic field of 10 KOe was applied to this molded body in the same manner as in the orientation magnetic circuit shown in FIG. 1 to impart anisotropy in the radial direction. Next, the molded body is subjected to a desynthetic oil / deorganic binder treatment at 400 ° C. for 2 hours under a pressure of 5 × 10 ^-2 torr, and then at the same pressure for 10 minutes.
The temperature was raised up to 80 ° C. at a heating rate of 15 ° C./min, and the temperature was maintained for 4 hours for sintering. The size and shape of the sintered body were good. Sintered body is 900 ° C in Ar gas atmosphere
Heat treatments of 1 hour and 600 ° C. × 1 hour were performed once. After machining, the surface magnetic flux density was measured, and good values as shown in Table 1 were obtained.

Example 6 Nd 28.0 by weight percentage
%, Dy 4.0%, B 1.0%, Nb 0.3%, Al
The Nd-Fe-B rare earth raw material coarse powder having a composition of 0.2% and the balance Fe was ground by a jet mill in an N ₂ gas atmosphere to obtain fine powder having an average particle size of 3.8 μm. This fine powder 8.
Mineral oil having a fractional distillation point of 200 to 300 ° C. at 5 kg and a kinematic viscosity of 2.0 cst at room temperature (made by Idemitsu Kosan, trade name MC, OI
L, P-02) 1.5 kg and organic binder methylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name Metroz 3000) 85 g
Were mixed to form a mixture. This mixture was extrusion-molded by the extruder shown in FIG. 1 and cut into a molded body. The density of the molded body was 3.0 g / cc. This molded body is also shown in Figure 1.
An orientation pulse magnetic field of 12 KOe was applied in the orientation magnetic circuit shown in (1) to impart radial anisotropy. Next, the molded body is subjected to demineralizing oil treatment and deorganic binder treatment at a temperature rising rate of 2 ° C / min from room temperature to 500 ° C under a pressure of 2 × 10 ^-2 torr, and then at 1100 ° C at the same pressure. Up to 20
The temperature was raised at a temperature rising rate of ° C / min, and the temperature was maintained for 4 hours for sintering. The size and shape of the sintered body were good. Sintered body is 900 ° C x 1 hour and 620 ° C in Ar gas atmosphere
The heat treatment of × 1 hour was performed once each. After machining, the surface magnetic flux density was measured, and good values were obtained as shown in Table 1.

Example 7 Nd 23.0 by weight percentage
%, Pr6.5%, Dy2.5%, B1.0%, Nb
Nd-Fe-B rare earth raw material coarse powder having a composition of 0.2%, Al 0.3%, Co 3.0% and balance Fe was jet milled in an N ₂ gas atmosphere to have an average particle size of 4.1 μm.
Got fine powder. This fine powder has a fractionation point of 200 to 5.8 kg.
4.2 kg of synthetic oil (produced by Idemitsu Kosan Co., Ltd., trade name DN, Cleaner H) having a kinematic viscosity of 2.5 cst at 300 ° C. and room temperature, and methylcellulose of organic binder (produced by Shin-Etsu Chemical Co., Ltd., trade name Metro-Z) 3,000 g of 145 g was mixed to obtain a mixture. This mixture was extrusion-molded by the extruder shown in FIG. 1 and cut into a molded body. The density of the molded body was 3.5 g / cc. An anisotropic magnetic field of 9 KOe was applied to the molded body by the magnetic alignment circuit shown in FIG. 2 to impart anisotropy. Next, the molded body is subjected to a desynthetic oil / deorganic binder treatment at 350 ° C. for 2 hours under a pressure of 5 × 10 ^-2 torr, and then at the same pressure for 11
The temperature was raised up to 00 ° C. at a heating rate of 20 ° C./min, and the temperature was maintained for 2 hours for sintering. The size and shape of the sintered body were good. Sintered body is 900 ° C in Ar gas atmosphere
A heat treatment of 2 hours and 600 ° C. × 2 hours was performed once. After machining, the surface magnetic flux density was measured, and good peak values as shown in Table 2 were obtained.

(Comparative Example 4) The raw material mixture produced in Example 4 was extrusion-molded by the extrusion-molding machine shown in FIG. 1 and cut into a molded body. In this case, by adjusting the extrusion pressure of the extruder, the density of the obtained molded product is 1.6 g / c.
It was c. Next, an oriented pulse magnetic field of 6 KOe was applied to this compact by the same orientation magnetic circuit as shown in FIG. 1 to impart anisotropy. In this process, the compact had a weak strength and was damaged. I couldn't. (Comparative Example 5) The raw material mixture produced in Example 5 was extruded by the extrusion molding machine shown in FIG. 1 and cut into a molded body.
In this case, the density of the obtained molded product was 5.8 g / cc by changing the extrusion conditions of the extruder. An orientation pulse magnetic field of 10 KOe was applied to this molded body in the same manner as in the orientation magnetic circuit shown in FIG. 1 to impart anisotropy in the radial direction. Next, the molded body was subjected to desynthetic oil, deorganic binder treatment, sintering, and heat treatment under the same conditions as in Example 5. After machining to the same dimensions as in Example 5, the surface magnetic flux density was measured, and as shown in Table 1, Example 5
It was significantly lower than the value in.

(Comparative Example 6) An oriented pulse magnetic field of 4 KOe was applied in the oriented magnetic circuit shown in FIG. 1 to a molded article produced by extrusion molding in Example 4 and having a density of 2.2 g / cc. , And gave anisotropy in the radial direction. Next, the molded body was subjected to demineralization oil treatment, sintering, and heat treatment under the same conditions as in Example 4. After machining to the same dimensions as in Example 4, the surface magnetic flux density was measured, and as shown in Table 1, the value was significantly lower than the value in Example 4. (Comparative Example 7) Fine powder 9.5K having an average particle size of 3.8 μm produced in Example 6
g has a fractionation point of 200 to 300 ° C. and a kinematic viscosity at room temperature of 2.
0 cst mineral oil (made by Idemitsu Kosan, trade name MC, OIL,
P-02) (0.5 Kg) and an organic binder, methyl cellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name Metroz 3000) (95 g) were mixed to prepare a mixture. Attempts were made to extrude this mixture with the extruder shown in FIG. 1, but the extrusion did not go smoothly, and it was not possible to obtain a molded article of good shape.

(Comparative Example 8) 4.0 kg of fine powder having an average particle size of 3.8 µm prepared in Example 6 has a fractionation point of 200 to 30.
6.0 kg of mineral oil (manufactured by Idemitsu Kosan, trade name MC, OIL, P-02) with a kinematic viscosity of 2.0 cst at 0 ° C. and room temperature, and methylcellulose (trade name Metro-, manufactured by Shin-Etsu Chemical Co., Ltd.) as an organic binder. (3000 g) 40 g was mixed to form a mixture. This mixture was extrusion-molded by the extruder shown in FIG. 1 and cut into a molded body. The average density of the molded body was 2.2 g / cc. An orientation pulse magnetic field of 12 KOe was applied to the formed body in the same manner as in the orientation magnetic circuit shown in FIG. 1 to impart radial anisotropy. Next, when the molded body was subjected to demineralized oil treatment, deorganic binder treatment and sintering under the same conditions as in Example 6, a partial deformation occurred in the sintered body, which made it a product. There wasn't. (Comparative Example 9) Mineral oil having a fractionation point of 200 to 300 ° C. and a kinematic viscosity of 2.0 cst at room temperature (8.5 kg, fine powder having an average particle size of 3.8 μm) manufactured in Example 6 (manufactured by Idemitsu Kosan Co., Ltd. Name MC, OIL, P-02)
A mixture of 1.5 kg and 510 g of an organic binder, methyl cellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: Metroze 3000) was mixed. This mixture was extrusion-molded by the extruder shown in FIG. 1 and cut into a molded body. The average density of the molded body was 2.8 g / cc. An orientation pulse magnetic field of 12 KOe was applied to the formed body in the same manner as in the orientation magnetic circuit shown in FIG. 1 to impart radial anisotropy. Next, the molded body was subjected to demineralized oil, deorganic binder treatment, sintering, and heat treatment under the same conditions as in Example 6. After machining to the same dimensions as in Example 6, the surface magnetic flux density was measured, and Table 1
As shown in, the value was significantly lower than the value in Example 6. In addition, the density of the sintered body is lower than in the case of Example 6,
The residual C amount was high.

Comparative Example 10 8.5 kg of fine powder having an average particle size of 3.8 μm prepared in Example 6 has a fractionation point of 300 to 5
1.5 kg of mineral oil (made by Idemitsu Kosan, trade name MC, OIL, S-32) having a kinematic viscosity of 31.5 cst at 00 ° C. and room temperature
And 85 g of an organic binder, methyl cellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: Metroze 3000) were mixed to form a mixture. This mixture was extrusion-molded by the extruder shown in FIG. 1 and cut into a molded body. The density of the molded body was 3.2 g / cc. An orientation pulse magnetic field of 12 KOe was applied to the formed body in the same manner as in the orientation magnetic circuit shown in FIG. 1 to impart radial anisotropy. Next, the molded body was subjected to demineralized oil, deorganic binder treatment, sintering, and heat treatment under the same conditions as in Example 6. After machining to the same dimensions as in Example 6, the surface magnetic flux density was measured, and as shown in Table 1, Example 6
It was significantly lower than the value in. In addition, the density of the sintered body was low and the amount of residual C was high as compared with the case of Example 6. (Comparative Example 11) An anisotropy was imparted to a molded product produced by extrusion molding in Example 7 and having a density of 3.5 g / cc by applying an orientation magnetic field under the same conditions as in Example 7. The compact was heated from room temperature to 1100 ° C. at a temperature rising rate of 20 ° C./min under a pressure of 5 × 10 ⁻² torr, and was held at that temperature for 2 hours for sintering. This sintered body was subjected to heat treatment at 900 ° C. × 2 hours and 600 ° C. × 2 hours once in an Ar gas atmosphere. After machining into the same dimensions as in Example 7, the surface magnetic flux density was measured, and as shown in Table 2, the peak value was significantly lower than that in Example 7. In addition, the density of the sintered body is lower than in the case of Example 7,
The residual C amount was high. (Comparative Example 12) The average particle size produced in Example 7 is 4.1μ.
4.2 kg of deionized pure water of 5.8 kg of fine powder of m
And 145 g of an organic binder, Methyl Cellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name Metrose 3000) were mixed to form a mixture. This mixture was extrusion-molded by the extruder shown in FIG. 1 and cut into a molded body. The density of the molded body was 3.0 g / cc. Anisotropy was imparted to this molded body by applying an orientation magnetic field under the same conditions as in Example 7. Next, 5 × 10 ^-2 to
Under the pressure of rr, 80 ° C. × 1 hour, then 350 ° C. × 2 hours of deionized water and organic binder removal treatment, and then the same pressure up to 1100 ° C. at a heating rate of 20 ° C./min. The temperature was maintained for 2 hours for sintering. Sintered body is Ar
Heat treatments of 900 ° C. × 2 hours and 600 ° C. × 2 hours were performed once in a gas atmosphere. When the surface magnetic flux density was measured after machining to the same dimensions as in Example 7, the peak value was significantly lower than that in Example 7, as shown in Table 2. In addition, the density of the sintered body was low and the amount of residual O ₂ was high as compared with the case of Example 7.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

As described above in detail, according to the raw material preparation and molding method of the present invention, a compact having a uniform compacting density with almost no progress of oxidation can be obtained. Magnets can be manufactured with high yield.
The effect of the present invention is particularly remarkable in the production of a thin ring-shaped rare earth sintered magnet, but it goes without saying that it is also effective in the production of a rectangular, round, or irregular shaped rare earth sintered magnet.

[Brief description of drawings]

FIG. 1 is a diagram showing an extruder and an oriented magnetic circuit suitable for carrying out the manufacturing method of the present invention.

FIG. 2 is a preferred oriented magnetic circuit for carrying out the manufacturing method according to the present invention.

[Explanation of symbols]

1 molded body, 2 magnetic yoke, 3 coil, 4 magnetic shaft, 5 non-magnetic shaft, 6 raw material mixture, 7 extrusion molding machine, 8 cutting device

Claims (9)

[Claims] 1. RCo ₅ system, R ₂ Co ₁₇ system or R-F
e-B system (R is one or more kinds of rare earth elements including Y) Fine powder for rare earth permanent magnet and mineral oil or synthetic oil are mixed, and this mixture is extruded to obtain a formed body, A method for producing a rare earth permanent magnet, which comprises applying an orienting magnetic field to a compact to impart anisotropy and then sintering. 2. The method for producing a rare earth permanent magnet according to claim 1, wherein the amount of the fine powder for rare earth permanent magnet in the mixture is 50 to 90% by weight. 3. The method for producing a rare earth permanent magnet according to claim 1, wherein an organic binder is added to the mixture. 4. The method for producing a rare earth permanent magnet according to claim 3, wherein the addition amount of the organic binder is 0.1 to 5% by weight of the fine powder for a rare earth permanent magnet. . 5. The method for producing a rare earth permanent magnet according to any one of claims 1 to 4, wherein a mineral oil or synthetic oil having a fractional distillation point of 400 ° C. or less and a kinematic viscosity at room temperature of 10 cst or less is used. And manufacturing method. 6. The method of manufacturing a rare earth permanent magnet according to claim 1, wherein the density of the molded body after extrusion molding is 2.0 to 5.0 g / cc. 7. The method for producing a rare earth permanent magnet according to claim 1, wherein the orientation magnetic field strength for imparting anisotropy to the compact is 5 KOe or more. 8. The method for producing a rare earth permanent magnet according to any one of claims 1 to 7, wherein the molded body obtained has a temperature of 50 to 5
A process for producing a demineralized oil, desynthesized oil and deorganic binder, which is held for 30 minutes or longer under conditions of 00 ° C. and a pressure of 10 ⁻¹ torr or less, and then sintering. 9. The method for producing a rare earth permanent magnet according to any one of claims 1 to 7, wherein the obtained molded body has 10 ^-1 torr.
Characterized by performing demineralized oil, desynthesized oil, and deorganic binder treatment at a temperature rising rate of 10 ° C./min or less in a temperature range from room temperature to 500 ° C. under a pressure of r or less, and then sintering. Manufacturing method.