JP3346628B2 - Manufacturing method of rare earth sintered magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an improved rare earth sintered magnet.

[0002]

2. Description of the Related Art Rare-earth sintered magnets usually melt the raw material metal and then pour it into a mold to pulverize the obtained ingot.
And then sequentially forming, sintering, is produced heat treatment and machining to. The pulverization is performed by a jet mill pulverization method in which particles collide with each other in an inert high-pressure gas atmosphere to obtain a dry powder, or a ball mill.
In general, the raw material powder is pulverized in an organic solvent using a mill or a vibration mill, and then the organic solvent is dried to obtain a dry powder. In forming the dry powder, it was weighed predetermined amounts of dry powder, which should be placed into a mold cavity, or a method of introducing into the mold cavity by leveling method using a feed box etc. taken
You . After the powder is supplied, an orientation magnetic field is applied to perform molding. In some cases, dry powder is supplied to the cavity to which a magnetic field has been applied in advance by the above-described method, followed by molding. On the other hand, the powder for the rare earth sintered magnet after the pulverization is very active chemically, so that it is rapidly oxidized in the air, resulting in deterioration of magnetic properties. As a method for preventing this, for example, Japanese Patent Application Laid-Open
No. -157924, JP 61-114505, JP-A-1-303710, No. Hei 3-1504 or <br/> JP 4-83319 is to prepare a mixture of raw material powder and an organic solvent This is supplied to the mold cavity in the same manner as the dry powder described above, and is molded in a magnetic field.
There is a disclosure of a manufacturing method in which drying, sintering, and heat treatment are sequentially performed .
According to these conventional production methods, use deterioration of magnetic properties due to oxidation by the effect of wet molding using an organic solvent a dry powder
It is somewhat relaxed compared to the case where However, organic solvents contain trace amounts of water and air, and even if hexane or toluene, which is a hydrophobic organic solvent, is used, changes over time due to oxidation of the fine powder for rare earth sintered magnets due to the contained water or air can be avoided. However, the level of the magnetic properties of the obtained rare earth sintered magnet was not satisfactory.

[0003]

The present inventors have INVENTION SUMMARY is] As a result of further study the cause no magnetic properties obtained satisfactory in the conventional wet forming process, moisture contained in the organic solvent shown above In addition to the oxidation of fine particles for rare earth sintered magnets by air, other factors were found to be involved. Strong interaction occurs between the fine powder for rare earth sintered magnet after grinding, it tends to set the bridge. Mark the orientation magnetic field for this
Even in the added state , the fine powder for the rare earth sintered magnet in the cavity locally has a nonuniform orientation. Molding for this
The orientation of the body is reduced and the final rare earth firing
Among the magnetic properties of the magnet , particularly, the residual magnetic flux density and the maximum energy product are reduced. Thus, to obtain good orientation it is necessary to prevent the formation of a bridge due to the interaction between the pulverized. The present inventors have confirmed that the organic solvent used in the conventional wet forming process no effect what such to prevent the formation of a bridge due to the interaction between the pulverized. That is, the orientation of the mixture produced by mixing the fine powder for rare earth sintered magnets and the organic solvent with respect to the orientation magnetic field is as inadequate as that of the dry powder.

[0004]

For the above reasons, rare earth elements
To obtain good magnetic properties pull the potential possessed by the fine powder for sintered magnets, as well as to prevent oxidation of the pulverized in a manufacturing process, to prevent the formation of bridging due to interaction between the fines, good It is necessary to obtain orientation. The present inventors have intensive studies results, the present inventors found that the above problems can be achieved by mixing a fine <br/> powder and vegetable oils for rare earth sintered magnet and the mixture is wet-molded in a magnetic field this This has led to the invention. In the present invention, rare earth
Fine powder for sintered magnets and vegetable oil are mixed to form a mixture.
Vegetable oil covers the surface of the pulverized, whereby oxidation since the surface of the chemically active the fines are shielded from the atmosphere is prevented. Method of mixing the pulverized and vegetable oils rather limited in particular, the fine powder and vegetable oils respectively weighed predetermined amounts, these mixers - may be mixed in like. Alternatively, a container filled with vegetable oil is installed at the fine powder outlet of the jet mill grinder, and the rare earth
Stone fines may be collected and made into a mixture. Further, ball - mill, vibration mill or attritor - be a vegetable oil by a predetermined amount introduced as a solvent pulverizer such as, and the coarse powder for the rare-earth sintered magnet by entering a predetermined amount projecting wet-milled to produce a mixture it can.

The amount ratio of the fine powder for the rare earth sintered magnet in the mixture is 50 to 80% by weight. When the amount ratio of the fine powder is less than 50%, the proportion of the vegetable oil which is the solvent in the mixture increases, causing supernatant to occur, which makes it difficult to quantitatively supply the mixture. If the amount ratio of the fine powder is more than 80%, the proportion of the vegetable oil as the solvent is too small, so that the mixture is cut off at the time of supply, and it is also difficult to supply the mixture quantitatively. The term "vegetable oil" used herein refers to an oil extracted from a plant, and the type of the oil is not limited to a specific plant. For example, soybean oil, rapeseed oil, corn oil, red bean oil, sunflower Oil, sesame oil or
Is such as camellia oil is Oh up. A mixture of two or more vegetable oils in an appropriate amount can also be used. Further, those containing at least one kind of vegetable oil as a main component to which necessary additives are added can also be used. In addition, the orientation of a mixture obtained by mixing the fine powder for rare earth sintered magnet and vegetable oil with respect to the orientation magnetic field is improved as compared with the orientation of a mixture prepared using a dry powder or an organic solvent. This modification of the pulverized surface with lubricity of vegetable oils, especially considered that reduction of the frictional force between the pulverized mutually acts effectively. Thus, generation of the bridge due to the interaction between the pulverized is eliminated, it is considered that the orientation is improved.

There is no particular limitation on the method of filling the mixture into the mold cavity. For example, a fixed amount supply device such as a monopump may be used to supply a fixed amount to the mold cavity, or a friction feeder may be used to cut and fill the mold cavity. Method and the like. The orientation magnetic field may be applied beforehand and then the mixture is filled into the mold cavity, or the mixture may be filled and then applied to the mold cavity, and the effect is the same in both cases. The mixture may be injected under pressure using a pressure feeder or the like into the mold cavity to which the alignment magnetic field has been applied. In this case, the filling density of the fine powder in the mold cavity is increased as compared with the above-described quantitative supply method or the scraping method, so that the residual magnetic flux density among the magnetic characteristics can be particularly increased . Further, after filling the mixture into the mold cavity in the dispensing method or leveling method, like the application of the aligning magnetic field
The mixture may be additionally injected into the mold cavity under pressure using a pressure feeder or the like in the state . In this case, the residual magnetic flux density can be increased for the same reason as described above. <br/> In case of adopting the method of filling the mold cavity of any of the above mixture also aligning magnetic field strength in the magnetic field during molding are more 2 kOe. If the orientation magnetic field strength is less than 2KOe, the orientation is insufficient .
Therefore, a high residual magnetic flux density cannot be obtained. Also, pressurized filter
In the above-described method of filling or additionally filling the mixture into the mold cavity with a die or the like, the injection pressure at the time of pressurized injection is set to 1 kgf / cm ² or more. When the injection pressure is less than 1 kgf / cm ² , the injection pressure is insufficient, and a high packing density of 1.8 g / cc or more cannot be obtained, and the packing density is not different from the level in the quantitative supply method or the rubbing method. There is no point in performing pressure injection.

The mixture filled in the mold cavity by the above various filling methods is molded in a magnetic field . Vegetable oil, which is a solvent, remains inside the molded body. When such a compact is rapidly heated from room temperature to a sintering temperature of 950 to 1200 ° C., the internal temperature of the compact rapidly rises, and the vegetable oil remaining in the compact and the rare earth element in the compact react with each other. Rare earth carbides are formed. For this reason, the generation of a sufficient amount of liquid phase for sintering is prevented, and a sintered body with a sufficient density cannot be obtained, which may lead to deterioration of magnetic properties. To prevent this,
Temperature 50-500 ° C , preferably 50-250 ° C and pressure 10 ^-1
It is desirable to perform a de-vegetable oil treatment that is maintained for 30 minutes or more under the condition of torr or less. By this treatment, the vegetable oil remaining in the molded body can be sufficiently removed. In addition, de-vegetable oil treatment
The heating temperature is not required to be one point as long as it is in the temperature range of 50 to 500 ° C., and may be two or more points. Pressure 10 ^-1 torr or less
In and the rate of Atsushi Nobori from room temperature to 500 ° C. 10 ° C. / min or less, and preferably also by applying de-vegetable oil processing to 5 ° C. / min or less, the temperature 50 to 500 ° C., preferably at 50 to 250 ° C. A deoiling effect similar to the deoiled vegetable oil treatment maintained at a pressure of 10 ^-1 torr or less for 30 minutes or more can be obtained.

[0008]

EXAMPLES Hereinafter, the present invention will be described molding direction and the application direction of the orientation magnetic field with an embodiment according to the so-called vertical magnetic field molding is parallel Specifically, the contents of the present invention is not limited thereto , apply a molding direction called transverse magnetic field molding method and the application direction is perpendicular oriented magnetic field, radial ring mold having anisotropy in the radial direction, the diameter 2 pole molding, or <br/> polar anisotropy molding This is also effective. (Example 1) S having a composition of Sm 36.5% by weight and Co 63.5% by weight percentage.
The mCo ₅ alloy coarse powder was jet-milled in an N ₂ gas atmosphere to obtain a fine powder having an average particle size of 5.0 μm. This fine powder 6
4 kg of soybean oil was mixed with Kg to obtain a mixture. Then the obtained fine
24 hours, 48 hours, 72 hours from the point of preparation of the mixture immediately after grinding
For 96 hours and 120 hours
And subjected to molding. Each mixture was molded by a molding apparatus shown in FIG. The molding is performed by sequentially filling each mixture in the mold cavity, and then lowering the upper punch to the die surface, applying an orientation magnetic field of 8KOe to the mold cavity, and then applying the orientation magnetic field. The molding was carried out under the conditions of wet molding at a molding pressure of 3 ton / cm ² while keeping the molding, to obtain a molded body. In the mold cavity
The packing density of the fines that put was 1.6 g / cc. In this case, a filter made of cloth having a thickness of 1 mm was used. Next, the molded body was subjected to de-vegetable oil treatment at 200 ° C. × 1 hour under a pressure of 5 × 10 ⁻² torr, and then 1130 ° C. × in an Ar gas atmosphere.
Sintering was performed under sintering conditions for 4 hours. In the following, heat-treated at 800 ° C. × 2 hours in an Ar gas atmosphere in the sintered body, followed by mechanical
The density, oxygen content and carbon of each sintered magnet sample processed and obtained
When the amount and magnetic properties were measured, as shown in Table 1,
The increase in the amount of oxygen in the sintered body with the passage of the standing time was extremely small, and good magnetic properties were obtained in all samples.

(Comparative Example 1) Fine powder for the SmCo ₅ based sintered magnet prepared by finely pulverizing in Example 1 was stored in a vacuum pack, and 24 hours and 48 hours after the fine pulverization.
A fine powder which was stored for 72 hours, 96 hours and 120 hours was obtained.
Then open the vacuum pack for each storage time and remove
In the same manner as in Example 1 except that only each fine powder was used.
And then perform molding, sintering, heat treatment and machining in a magnetic field and compare
Example sintered magnet samples were obtained. At the time of molding, only each of the fine powders is sequentially cut and filled into the mold cavity of the molding apparatus shown in FIG. 1, and the filling density of the fine powder in the mold cavity is 1.
It was 6 g / cc. In this case, the upper punch was replaced with one having no oil discharge hole, and no filter was used. Obtained
When the density, oxygen content, carbon content and magnetic characteristics of each sample were measured, as shown in Table 1, the increase in the oxygen content of the sintered body with respect to the passage of the standing time was larger than that in Example 1, and with this, A remarkable decrease in coercive force was observed. The low Ikoto be seen than the initial idle time increases of the sintered body the oxygen content is not so large in residual magnetic flux density in Example 1.

Example 2 Sm 25.0%, Fe 14.0%, Cu 4.5%, Z
Sm ₂ Co ₁₇ system having a composition of r2.5% and Co54.0%
The alloy coarse powder was ball-milled in corn oil to recover a mixture of crushed fine powder and corn oil. Weight ratio of fines accounted for the mixture Ri 65% der, the average particle size of fine powder in the mixture was 5.0 .mu.m. Then the crop of the resulting mixture
24 hours, 48 hours, 72 hours, 96 hours and 120 hours from the time of manufacture
The mixtures left for a while were prepared and subjected to molding. Each mixture was molded by a molding apparatus shown in FIG. Molding, filled sequentially Suriki' each mixture into the mold cavity, then
After lowering the upper punch to the die surface with the above, an orientation magnetic field of 6 KOe is applied to the mold cavity, and then wet molding is performed at a molding pressure of ² ton / cm ² with the orientation magnetic field applied.
A molded article was obtained. The packing density of the fines that put into the mold cavity was 1.5 g / cc. In this case, a 0.5 mm thick metal filter was used. Next, 5 × 10 ^{-2 was added}
After subjecting to vegetable oil removal at 100 ° C. × 1 hour under torr pressure, sintering was performed at 1200 ° C. × 2 hours in an H ₂ Ar gas atmosphere. The obtained sintered body was heated to 1180 in an Ar gas atmosphere.
A solution treatment at 1 ° C. × 1 hour and an aging treatment at 750 ° C. × 20 hours were performed. Then machined, each of the sintered magnet samples obtained
When the density, oxygen content, carbon content and magnetic properties were measured,
As shown in Table 1, the increase in the oxygen amount of the sintered body with the passage of the standing time was extremely small, and good magnetic properties were obtained in all the samples.

Comparative Example 2 The coarse powder of the Sm ₂ Co ₁₇ alloy used in Example 2 was ball-milled in toluene, and then dried to obtain a fine powder having an average particle size of 5.0 μm. This fine powder is stored in a vacuum pack, and after 24 hours , 48 hours, 72 hours, 96 hours
For 120 hours. Then each of the storage times
Unpack the vacuum pack and remove each fine powder only.
Except for use, molding in a magnetic field , sintering, heat treatment and machining were performed in the same manner as in Example 2 to obtain a sintered magnet sample of the comparative example.
Obtained. At the time of molding, only each of the fine powders was sequentially cut and filled into the mold cavity of the molding apparatus shown in FIG. 1, and the filling density of the fine powder in the mold cavity was 1.5 g / cc. In this case, in this case, replace the upper punch with one without an oil discharge hole,
No filters were used. Density of each sample obtained , acid
When the elementary amount, the carbon amount and the magnetic properties were measured, as shown in Table 1, the increase in the oxygen amount of the sintered body with respect to the elapse of the standing time was larger than that in Example 2, and the coercive force was remarkably increased accordingly.
Significant decline was seen. In addition, the residual magnetic flux density was lower than that of Example 2 from the initial standing time in which the increase in the oxygen amount of the sintered body was not so large.
Low Ikoto is seen compared to.

Example 3 Nd 28.0%, Pr 1.5%, Dy 1.0%, B1.
0%, Nb1.0%, Co3.5% , Al0.3%, Nd-Fe-B based alloy coarse powder having a composition of the balance Fe and jet mill in _{N 2} gas atmosphere, fine exhaust crusher A container filled with rapeseed oil was installed at the outlet, and the discharged fine powder was directly collected in rapeseed oil in a N ₂ gas atmosphere to form a mixture. The weight ratio of fine powder in the mixture Ri 70% der, the average particle size of the fine powder
It was 3.9 μm. Then, the resulting mixture immediately after pulverization
24 hours, 48 hours, 72 hours, 96 hours and
Each mixture left for 120 hours was prepared and subjected to molding.
Was. Each mixture was molded by a molding apparatus shown in FIG. Molding is performed by filling the mold cavity by rubbing each mixture in order , then lowering the upper punch to the die surface, applying an orientation magnetic field of 3KOe to the mold cavity, and then molding while applying the orientation magnetic field. conditions to be wet-molded at a pressure of 1.0ton / cm ²
And a molded article was obtained. The packing density of the fine powder in the mold cavity was 1.6 g / cc. In this case, a filter obtained by welding a porous metal material to the upper punch was used. Then, under a pressure of 5 × 10 ^-2 torr in the molded body is subjected to heating rate 5 ° C. / min of de vegetable oil processing to 500 ° C. from room temperature, then to 1070 ° C. 30 ° C. at the same pressure / min The temperature was raised at the temperature rising rate, and the temperature was maintained for 4 hours for sintering. Next, the sintered body was heated in an Ar gas atmosphere at 900 ° C for 1 hour and at 600 ° C for 1 hour.
Each time heat treatment was performed once. Then machined and obtained
Density, oxygen content, carbon content and magnetic characteristics of each sintered magnet sample
When the properties were measured, as shown in Table 1, the increase in the amount of oxygen in the sintered body with the passage of the standing time was extremely small, and good magnetic properties were obtained in all the samples.

Comparative Example 3 The coarse powder of the Nd—Fe—B alloy used in Example 3 was jet-milled to an average particle size of 4.0 μm in an N ₂ gas atmosphere.
Directly recovered fines during the connection gas tight container in the fine powder discharge port of the crushing machine, by storing, 24 hours milling, 48
Time, 72 hours, 96 hours and 120 hours
Was. Then, each of the storage times was taken out of the airtight container.
In the same manner as in Example 3 except that only the fine powder was used,
Molding was performed in a magnetic field . Upon molding, established the molding apparatus shown in Figure 1 in an Ar gas atmosphere, the the mold cavity was filled with Suriki' only each <br/> fine, the packing density of <br/> fines in the mold cavity It was 1.6 g / cc. In this case, the upper punch was replaced with one without a vegetable oil discharge hole, and no filter was used. Do not bring each compact immediately after molding into contact with the atmosphere.
And then enter the sintering furnace.
To sintering, the sintered magnet of Comparative Example by heat treatment and machining
A sample was obtained. Density of each sample obtained, the oxygen content, carbon content及
Measurement of the fine magnetic properties, as shown in Table 1, large increase in the sintered body oxygen content compared to the Example 3 on the course of the standing <br/> time, a significant decrease in the coercive force along with this It was observed. Further, us go low residual magnetic flux density from the initial idle time increases of the sintered body the oxygen content is not so large as compared with Example 3
I understand .

Example 4 Nd27.5%, Pr2.5%, Dy1.5%, B1.
0%, Nb 0.6%, Co 2.5%, Al 0.2%, Ga 0.2%,
Nd-Fe-B-based alloy coarse powder having the balance of Fe
₂ jet milled in a gas atmosphere, set up a container filled with oil mixture of soybean oil and rapeseed oil in fine powder discharge port of the crusher to recover a discharge fines directly mixed oil in N ₂ gas atmosphere, the mixture And The weight ratio of fines in this mixture is 70
% Der is, the average particle size of fine powder was 4.0 .mu.m. Next
The obtained mixture was molded by a molding apparatus shown in FIG. Upon molding, after lowering the upper punch to the die surface, applying an orientation magnetic field of 8KOe the mold cavity, then
While the orientation magnetic field was applied , the mold cavities were filled with the respective mixtures sequentially filled in the pressurized supply apparatus at an injection pressure of 10 kgf / cm ² . Packing density of fines definitive the mold cavity was 2.8 g / cc. After filling the mixture into the mold cavity, the mixture was wet-molded at a molding pressure of 1.0 ton / cm ² while applying an orientation magnetic field to obtain a molded body. In this case, the filter is 1mm
Thick cloth was used. Next, 5 × 10
Under a pressure of ^-2 torr, subjected to a de-vegetable oil processing heating rate of 5 ° C. / min up to 500 ° C. from room temperature, then at the same pressure 1100
The temperature was raised to 30 ° C. at a rate of 30 ° C./min, and the temperature was maintained for 4 hours for sintering. Next, the sintered body was subjected to heat treatment once each in an Ar gas atmosphere at 900 ° C. × 1 hour and 600 ° C. × 1 hour. Then machined, the density of the obtained sintered magnet sample,
When the amount of oxygen, the amount of carbon and the magnetic properties were measured, good values shown in Table 1 were obtained.

Comparative Example 4 The mixture prepared in Example 4 was molded by a molding apparatus shown in FIG. Before Upon molding, lowering the upper punch to the die surface, then that while applying an orientation magnetic field of 1KOe the mold cavity was filled into a mold cavity pressurized feed device
The mixture was filled at an injection pressure of 10 kgf / cm ² . The packing density of the fines that put into the mold cavity was 3.0 g / cc. After filling the mixture into the mold cavity, the mixture was wet-molded at a molding pressure of 1.0 ton / cm ² while applying an orientation magnetic field to obtain a molded body.
In this case, a filter made of cloth having a thickness of 1 mm was used. Then, under a pressure of 5 × 10 ^-2 torr in the molded body is subjected to heating rate 5 ° C. / min of de vegetable oil processing to 500 ° C. from room temperature, then to 1100 ° C. 30 ° C. at the same pressure / min The temperature was raised at the temperature rising rate, and the temperature was maintained for 4 hours for sintering. Obtained
Was 900 ° C. × 1 hour and 600 ° C. × in an Ar gas atmosphere sintered
Heat treatment for one hour was performed once each. Then machined and obtained
When the density, oxygen content, carbon content and magnetic properties of the obtained sintered magnet sample were measured, as shown in Table 1, the residual magnetic flux density and the maximum energy product were much lower than those in Example 4. there were.

Comparative Example 5 The mixture prepared in Example 4 was molded by a molding apparatus shown in FIG. Upon molding, the upper punch is lowered to the die surface, then while applying a magnetic field of 8KOe the mold cavity, the mold cavity, the <br/> mixture filled in the pressurized feed system 0.5 kgf / cm ² At an injection pressure of. The packing density of the fines that put the mold cavity after filling was 1.2 g / cc. After filling the mixture into the mold cavity, the mixture was wet-molded at a molding pressure of 1.0 ton / cm ² while applying an orientation magnetic field to obtain a molded body. In this case, a filter made of cloth having a thickness of 1 mm was used. Then, under a pressure of 5 × 10 ^-2 torr in the molded body is subjected to heating rate 5 ° C. / min of de vegetable oil processing to 500 ° C. from room temperature, then to 1100 ° C. 30 ° C. at the same pressure / min The temperature was raised at the temperature rising rate, and the temperature was maintained for 4 hours for sintering. The obtained sintered body was subjected to heat treatment once each in an Ar gas atmosphere at 900 ° C. × 1 hour and 600 ° C. × 1 hour. Then machine
When the magnetic properties and the like of the obtained sintered magnet sample were measured, as shown in Table 1, the residual magnetic flux density and the maximum energy were significantly lower than those of Example 4.

Comparative Example 6 The Nd—Fe—B-based alloy coarse powder used in Example 4 was pulverized by a jet mill in an N ₂ gas atmosphere, and the same compounding as in Example 4 was performed at the fine powder outlet of the pulverizer. from soybean oil and rapeseed oil ratio
It becomes mixed oil established a container filled with, collect the discharged fine powder directly mixed oil in an N ₂ gas atmosphere and the mixture. The weight ratio of fine powder in the mixture Ri 40% der, the average particle size of fine powder was 4.1 .mu.m. This mixture was molded using the molding apparatus shown in FIG. 2 under the same conditions as in Example 4.
A supernatant is formed due to too much vegetable oil in the mixture,
The supply amount is not stable at the time of pressurized supply of the mixture by the pressurized supply device, and the packing density and the size of the compact greatly fluctuate every molding,
Furthermore, this also caused variations in magnetic properties,
The product could not be.

(Comparative Example 7) The Nd-Fe-B alloy coarse powder used in Example 4 was pulverized by a jet mill in an N ₂ gas atmosphere, and the same compounding as in Example 4 was performed at the fine powder discharge port of the pulverizer. from soybean oil and rapeseed oil ratio
It becomes mixed oil established a container filled with, collect the discharged fine powder directly mixed oil in an N ₂ gas atmosphere and the mixture. The weight ratio of fine powder in the mixture Ri 90% der, the average particle size of fine powder was 3.8 .mu.m. Next, the mixture was molded using the molding apparatus shown in FIG. 2 under the same conditions as in Example 4. However, the amount of fine powder in the mixture was too large, and the mixture was cut off. The supply amount was not stable at the time of supply, and the packing density and the size of the compact greatly fluctuated with each molding, and this also caused variations in the magnetic characteristics, so that the product could not be manufactured.

Example 5 Nd 28.0%, Dy 4.0%, B 1.0%, Nb1.
0%, Co4.5%, Al0.3% , Nd-Fe-B based alloy coarse powder having a composition of the balance Fe and jet mill in _{N 2} gas atmosphere to obtain a fine powder having an average particle size of 3.8 .mu.m. 4.5 kg of this fine powder was mixed with 4.5 kg of sesame oil, and mixed to obtain a total of 10 kg. This mixture was molded by a molding apparatus shown in FIG. Upon molding, the mold cavity was frayed and filled with the mixture, and then the upper punch was lowered to the die surface . To the next,
While applying an orientation magnetic field of 10KOe the mold cavity, the mold cavity, the mixture filled in the pressurized feed device 20
Additional filling was performed at an injection pressure of Kgf / cm ² . The packing density of the fines that put the mold cavity after additional charging was 2.9 g / cc. After the mixture was additionally filled in the mold cavity, the mixture was wet-molded at a molding pressure of 1.0 ton / cm ² while applying an orientation magnetic field to obtain a molded body. In this case, a filter made of cloth having a thickness of 1 mm was used. Then, under the pressure of the molded body 5 × 10 ^-2 torr, subjected to a de-vegetable oil processing heating rate 7 ° C. / min up to 500 ° C. from room temperature, then up to 1100 ° C. 20 ° C. at the same pressure / min The temperature was raised at the temperature rising rate, and the temperature was maintained for 2 hours for sintering. Next, the sintered body was subjected to heat treatment once each in an Ar gas atmosphere at 900 ° C. × 1 hour and 550 ° C. × 1 hour. Then machined , the density, oxygen content and carbon content of the obtained sintered magnet sample
When the magnetic properties were measured, good values shown in Table 1 were obtained.

[0020] In a pressure of Comparative Example 8 Example 5 5 × 10 ^-2 torr to compact molded with, subjected to a de-vegetable oil processing heating rate of 15 ° C. / min up to 500 ° C. from room temperature, then the same pressure to 1100 ° C. the temperature was raised at a heating rate of 20 ° C. / min, and sintered by holding at that temperature for 2 hours. Next, the sintered body was subjected to heat treatment once each in an Ar gas atmosphere at 900 ° C. × 1 hour and 550 ° C. × 1 hour. Then, machining was performed, and the carbon content, magnetic properties, and the like of the obtained sintered magnet sample were measured. As shown in Table 1, the carbon content was higher than that of Example 5; Density, maximum energy product and coercivity were low.

Example 6 Nd 28.0%, Dy 1.5%, B 1.0%, Nb 1.
Nd—Fe— having a composition of 2%, Al 0.3%, and the balance Fe
The B based alloy coarse powder with a jet mill ground in N ₂ gas atmosphere, established a container filled with sunflower oil to a fine powder discharge port of the crusher to recover a discharge fines into direct sunflower oil in an N ₂ gas atmosphere And a mixture. The weight ratio of fine powder in the mixture Ri 75% der, the average particle size of fine powder was 3.7 .mu.m. This mixture was molded by a molding apparatus shown in FIG.
In this case, use a die with two injection holes and pressurize
The material supply hose from the damper also used a forked part on the way. Upon molding, filled with Suriki' the mixture into the mold cavity, it is then lowered over the punch to the die surface
Was. To the next, before the mold cavity to the mold cavity while applying an orientation magnetic field of 4 KOe, filled into pressurized feed device
The mixture was additionally charged at an injection pressure of 10 kgf / cm ² . The packing density of the fines that put the mold cavity after the addition filling 2.7g
/ cc. After additional filling of the mixture into the mold cavity,
With the orientation magnetic field being applied, wet molding was performed at a molding pressure of 1.0 ton / cm ² to obtain a molded body. In this case, a filter obtained by welding a porous metal material to the upper punch was used. Then, under the pressure of the molded body 5 × 10 ^-2 torr, subjected to heating rate 3 ° C. / min of de vegetable oil processing to 500 ° C. from room temperature, then to 1060 ° C. at the same <br/> Ji pressure Was heated at a heating rate of 30 / min , and kept at that temperature for 3 hours for sintering. Ar is added to the obtained sintered body .
Heat treatment at 900 ° C. × 1 hour and 600 ° C. × 1 hour were performed once each in a gas atmosphere. Then machined and obtained sintered magnet
When the density, oxygen content, carbon content and magnetic properties of the sample were measured, good values shown in Table 1 were obtained.

[0022]

[Table 1]

[0023]

As described above in detail, the raw material preparation and molding method of the present invention improves the orientation of the rare earth sintered magnet and improves the oxidation resistance, so that the high performance rare earth sintered magnet can be stably obtained. Now it can be mass-produced.

[Brief description of the drawings]

FIG. 1 is a partial longitudinal sectional view of a molding apparatus used in Examples and Comparative Examples of the present invention.

FIG. 2 is a partial longitudinal sectional view of a molding apparatus used in another example of the present invention and a comparative example.

FIG. 3 is a partial longitudinal sectional view of a molding apparatus used in another example of the present invention and a comparative example.

[Explanation of symbols]

1. Upper punch, 2 filters, 3 lower punches, 4 dies, 5 orientation coils, 6 scraping feeder, 7 raw material mixture, 8 raw material supply hose, 9 raw material supply feeder.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-276303 (JP, A) JP-A-4-97957 (JP, A) Patent 2731337 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01F 1/00-1/117 B22F 3/00 H01F 41/02

Claims (3)

(57) [Claims] An RCo ₅ system, an R ₂ Co ₁₇ system or R
-Mixing of fine powder for Fe-B based rare earth sintered magnets (R is at least one of rare earth elements including Y) and vegetable oil, molding the resulting mixture in a magnetic field, and then sequentially removing vegetable oil , have rows sintering and heat treatment, and getting into the mixture
Adjust the amount of vegetable oil to 20 to 50% by weight, and
A method for producing a rare-earth sintered magnet, comprising shaping . 2. The molded body is heated at a temperature of 50 to 500 ° C. and a pressure of 10 ° C.
^The method for producing a rare earth sintered magnet according to claim 1, wherein a de-vegetable oil treatment is performed for maintaining the condition at ⁻¹ torr or less for 30 minutes or more. 3. The devegetable oil treatment according to claim 1, wherein the compact is maintained at a pressure of 10 ^-1 torr or less and a temperature rising rate in a temperature range from ordinary temperature to 500 ° C. of 10 ° C./min or less. Of manufacturing rare earth sintered magnets.