JP3240034B2 - Rare earth sintered magnet and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Rare earth sintered magnets are manufactured using powder metallurgy techniques in which an alloy obtained by melting a raw material metal and pouring it into a mold is pulverized, formed, sintered and heat-treated. Alternatively, it is manufactured by reducing an oxide of a rare earth element with a reducing agent, diffusing the reduced rare earth element into Co powder, Fe powder, or the like to obtain an alloy powder, and pulverizing, molding, sintering, and heat treating the alloy powder. Irrespective of whether it is produced by a melting method or a reduction diffusion method, an alloy powder for a rare earth sintered magnet containing a large amount of a rare earth element is chemically very active. For this reason, oxidation is particularly severe during the pulverization process and the handling process immediately after the pulverization, and the oxygen content of the rare earth sintered magnet finally obtained becomes high, which causes a decrease in magnetic properties and hinders high performance. Had become.

As means for solving this problem, for example, JP-A-58-157924 and JP-A-61-1145 are known.
As disclosed in Japanese Unexamined Patent Application Publication No. 05, JP-A-1-303710, etc., a method has been proposed in which fine powder for a rare-earth sintered magnet is immersed in an organic solvent to form a mixture, and the mixture is wet-formed. However, the degree of oxidation of the fine powder in the mixture due to the influence of dissolved oxygen and water in the organic solvent is large, and these methods have problems in stability of magnetic properties and long-term storage of raw materials. Further, for example, Japanese Unexamined Patent Publication No. 60-91601 discloses a method of producing a rare earth magnet raw material by wet grinding in an organic solvent. However, wet pulverization has problems in that fine powder having a sharper particle size distribution cannot be obtained as compared with fine powder obtained by jet mill pulverization, and mixing of oxygen and carbon from an organic solvent in the pulverization process is inevitable.

[0004] In order to solve the above problems, the present inventors first used a mineral oil or a synthetic oil as a solvent, and jet-milled the fine powder in a nitrogen gas atmosphere in which the oxygen concentration was reduced as much as possible. A method of directly recovering the oil in the gas atmosphere without contacting the air has been proposed (Japanese Patent Application Nos. 5-59820, 5-175850, 5-200543, 5-200543, 5-317
747). According to this proposal, oxidation in the manufacturing process from pulverization to sintering was suppressed, and the level of oxygen content of the sintered body was reduced, so that high magnetic properties could be stably obtained.

[0005]

However, according to the subsequent detailed research, in the pulverization in a nitrogen gas stream in which the oxygen concentration is suppressed, the oxidation of the raw material is suppressed, but the rare earth element and the nitrogen in the raw material component are suppressed. It was found that bonding occurred and the level of nitrogen in the sintered body increased. As a result, there is a problem that the content of the rare earth element which effectively contributes to the magnetic characteristics in the sintered body is reduced, and the magnetic characteristics such as the coercive force are reduced. As a result of intensive studies on this problem, a prospect was obtained that the magnetic characteristics could be further improved by suppressing the increase in the amount of nitrogen, and the present invention was reached.

Accordingly, an object of the present invention is to provide a rare earth sintered magnet whose magnetic properties are improved by reducing the oxygen content, the nitrogen content and the carbon content to predetermined amounts or less, and a method of manufacturing the same. .

[0007]

The present invention, which has solved the above-mentioned problems, comprises an RCo ₅ system, an R ₂ Co ₁₇ system or R-Fe-B.
(R is one or more of the rare earth elements including Y) The raw material coarse powder for the rare earth sintered magnet has an oxygen concentration of 30 p.
pm or less in an Ar gas atmosphere, and the fine powder obtained by the pulverization is recovered in a mineral oil, a synthetic oil or a vegetable oil from an Ar gas atmosphere having an oxygen concentration of 30 ppm or less. This is a method for producing a rare-earth sintered magnet that is subjected to de-oiling, sintering and heat treatment after wet molding in a magnetic field using a mixture. According to the present invention, since pulverization is performed in an Ar gas atmosphere, there is almost no contamination of nitrogen during the pulverization process, and the level of nitrogen content of the rare earth sintered magnet finally obtained is equal to the initial raw material coarseness for the rare earth sintered magnet. Nitrogen level of flour (3
(Less than 00 ppm). The oxygen concentration in the Ar gas atmosphere is preferably as low as possible, but if the oxygen concentration is 30 ppm or less, the level of the oxygen content of the finally obtained rare earth sintered magnet becomes 2000 ppm or less, and high magnetic properties can be stably obtained. Thus, the oxygen concentration in the Ar gas atmosphere is preferably 30 ppm or less. Subsequently, in an Ar gas atmosphere having an oxygen concentration of 30 ppm or less, the above-mentioned fine powder for a rare earth sintered magnet having low levels of oxygen content, nitrogen content and carbon content is mixed with mineral oil, synthetic oil or vegetable oil. The raw material mixture composed of the above-mentioned fine powder and oil is directly introduced without being brought into contact with the atmosphere.
Specifically, it is preferable to attach a container filled with the oil to the crusher. Since the fine powder in the raw material mixture is shielded from the atmosphere by the mineral oil, the synthetic oil or the vegetable oil, the promotion of oxidation and nitridation is hindered, and the level of the low oxygen content and the low nitrogen content is maintained. When a conventional organic solvent (toluene, hexane, or the like) is used, the amount of oxygen in the fine powder increases greatly due to the effect of oxygen and moisture contained in the conventional organic solvent, and the magnetic properties deteriorate.

Further, the present invention relates to an R—Fe—B based rare earth sintered magnet (R is one or more rare earth elements including Y), wherein the oxygen content is 2000 ppm or less and the nitrogen content is 2000 ppm or less. 300ppm or less, carbon content is 1000p
pm or less and a maximum energy product (BH) max of more than 42.6 MGOe.

[0009] The present invention also relates to RCo ₅ or R ₂ Co
₁₇ type rare earth sintered magnet (R is one or two or more rare earth elements including Y), and has an oxygen content of 200
0 ppm or less, nitrogen content is 300 ppm or less, carbon content is 1000 ppm or less, and 19.7 MGO
It is a rare earth sintered magnet having a maximum energy product (BH) max exceeding e.

The type of mineral oil or synthetic oil used in the present invention is not specified, but it has a kinematic viscosity of 1 at room temperature.
When it exceeds 0 cst, the bonding force between the fine powders is increased due to the increase in viscosity, which adversely affects the orientation of the fine powders during wet molding in a magnetic field. Therefore, the kinematic viscosity of the mineral oil or the synthetic oil at room temperature is preferably 10 cst or less. If the fractional point of the mineral oil or the synthetic oil exceeds 400 ° C., it becomes difficult to remove the oil, the amount of carbon remaining in the sintered body increases, and the magnetic properties deteriorate. Therefore, the fractionation point of mineral oil or synthetic oil is 400
C. or less is preferred. Vegetable oil refers to oil extracted from a plant, and its type is not limited to a particular plant.
For example, soybean oil, rapeseed oil, corn oil, banana oil, sunflower oil and the like can be mentioned. In the above, the amount ratio of the fine powder for rare earth sintered magnet in the raw material mixture is 5% by weight.
0 to 85%. When the amount ratio of the fine powder is less than 50%, the ratio of the oil in the raw material mixture is increased, resulting in a supernatant, which makes it difficult to supply the raw material mixture quantitatively. Also,
If the amount ratio of the fine powder is more than 85%, the ratio of the oil is too small, so that the supply of the raw material mixture is cut off, which also makes it difficult to quantitatively supply the raw material mixture.

The method of wet molding the raw material mixture produced as described above is not particularly limited. The raw material mixture may be filled into the mold cavity by abrasion, and may be subjected to pressure molding in a magnetic field by applying an orientation magnetic field. Alternatively, the raw material mixture may be quantitatively weighed and directly injected into the mold cavity, and an orientation magnetic field may be applied to perform pressure molding in the magnetic field. Further, it is also possible to apply an orientation magnetic field to the mold cavity, then inject the raw material mixture under pressure from an injection hole formed in the mold, and then perform pressure molding in a magnetic field. In any of these molding methods, a hole for discharging the solvent is provided on the upper punch or lower punch surface, and a filter made of cloth or paper is used to prevent the fine powder from flowing out during pressure molding. Alternatively, it is necessary to devise a method such as using a part of the upper punch or the lower punch as a porous filter material.

[0012] Since the oil remains in the molded body after the molding, if normal sintering is performed as it is, the remaining oil evaporates during heating and contaminates the inside of the sintering furnace. The part decomposes and remains in the sintered body. For this reason, the residual carbon content of the sintered body increases, the sintered body density decreases, and the residual magnetic flux density Br and the maximum energy product (BH) max decrease. Therefore, it is necessary to sinter the molded body after performing the deoiling treatment. The deoiling treatment is performed by keeping the molded body in a temperature range of 100 to 500 ° C. for 30 minutes or more under reduced pressure of 0.1 Torr or less. In addition, holding | maintenance does not need to be one point if it is the range of 100-500 degreeC, and may be two or more points. Further, the temperature is reduced from room temperature to 50 under reduced pressure of 0.1 Torr or less.
Deoiling can also be performed by setting the rate of temperature rise to 0 ° C to 10 ° C / min or less. The compact after the deoiling process is subsequently heated to a sintering temperature, and further maintained at the sintering temperature for a predetermined time to form a sintered body. The obtained sintered body is subjected to a heat treatment to obtain the rare earth sintered magnet of the present invention.

[0013]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the contents of the present invention are not limited to the examples. (Example 1) Sm36.7% in weight percentage, the oxygen concentration raw coarse powder of SmCo ₅ rare earth sintered magnet having a main component composition Co63.3% are jet milled in an Ar gas flow of 20 ppm. Subsequently, a synthesis where the fractionation point filled in the container installed at the fine powder discharge port of the pulverizer held in an Ar gas stream having an oxygen concentration of 20 ppm is 200 to 300 ° C. and the kinematic viscosity at room temperature is 1.0 cst. Oil (made by Idemitsu Kosan, trade name DN.
Roll oil. The discharged fine powder was directly collected in AL-35) to prepare a raw material mixture. The ratio of the fine powder in the raw material mixture was 55% by weight percentage, and the average particle size of the fine powder was 5.0 μm. This raw material mixture was molded by a molding apparatus shown in FIG. Molding conditions are 8 for mold capacity
With the KOe magnetic field applied, the raw material mixture charged into the pressurized supply apparatus was injected and filled at an injection pressure of 10 kgf / cm ² . After filling the raw material mixture into the mold cavity,
The molding pressure is 4.0 ton / cm ² while the orientation magnetic field is applied.
To obtain a molded body. In this case, the filter is 1
A cloth of mm thickness was used. Next, 5 × 1
Under the pressure of 0 ^-2 Torr, a de-synthesis oil treatment is performed at a rate of 5 ° C./min from room temperature to 500 ° C., and then the temperature is increased to 1135 ° C. at a rate of 30 ° C./min at the same pressure. And
It was kept at that temperature for 4 hours for sintering. The obtained sintered body was further subjected to a heat treatment at 800 ° C. × 1 hour in an Ar gas atmosphere to obtain a sintered magnet of the present invention. Table 1 shows the results of measuring the content of oxygen, the content of nitrogen, the content of carbon, the density of the sintered body, and the magnetic properties after machining this magnet. Table 1 shows that good magnetic properties were obtained.

[0014]

[Table 1]

Comparative Example 1 The same raw material powder of the SmCo ₅ based rare earth sintered magnet used in Example 1 was pulverized by a jet mill in a nitrogen gas stream having an oxygen concentration of 20 ppm. Subsequently, the discharged fine powder was collected in the same synthetic oil as in Example 1 filled in the container provided at the fine powder discharge port of the pulverizer held in the nitrogen gas stream having the same oxygen concentration to prepare a raw material mixture. The weight percentage of the fine powder in the raw material mixture was 55%, and the average particle size of the fine powder was 4.8 μm. Thereafter, molding, desynthesis oil treatment, sintering and heat treatment were performed under the same conditions as in Example 1 except that this raw material mixture was used, and a sintered magnet of a comparative example was obtained. After machining this magnet, the oxygen content, nitrogen content, carbon content, sintered body density and magnetic properties were measured. Table 1 shows the results. Table 1 shows that the nitrogen content is higher and iHc and (BH) max are lower than those in Example 1.

Example 2 Sm 25.2%, Fe 13.8%, Cu
The raw material powder of the Sm ₂ Co _17- based rare earth sintered magnet having a main component composition of 4.5%, Zr 2.0%, and Co 54.5% was jet-milled in an Ar gas stream having an oxygen concentration of 10 ppm. Subsequently, the fine powder discharged into vegetable oil (soy oil: corn oil = 50%: 50% mixed oil) filled in a container provided at the fine powder discharge port of the crusher maintained in an Ar gas atmosphere having the same oxygen concentration. Was directly recovered to produce a raw material mixture. The weight percentage of the fine powder in this raw material mixture is 80%
The average particle size of the fine powder was 5.3 μm. Next, this raw material mixture was molded by a molding apparatus shown in FIG. The molding conditions were as follows: the raw material mixture was scraped and filled into the mold cavity, an orientation magnetic field of 10 KOe was applied, and then the molding pressure was 2.0 ton / c with the orientation magnetic field applied.
Wet molding was performed under the conditions of m ² to obtain a molded body. In this case, a filter made of paper having a thickness of 0.3 mm was used.
Next, the molded body was heated at 200 ° C. under a pressure of 5 × 10 ⁻² Torr.
× 2 hours of de-vegetable oil treatment, then 12 hours at the same pressure
The temperature was raised to 00 ° C. at a temperature rising rate of 20 ° C./min, and the temperature was maintained for 2 hours for sintering. Next, A was added to the obtained sintered body.
Solution treatment at 1180 ° C for 4 hours in r gas atmosphere and 7
An aging treatment at 50 ° C. × 24 hours was performed to obtain a sintered magnet of the present invention. After machining this magnet, the oxygen content, nitrogen content, carbon content, sintered body density and magnetic properties were measured. Table 1 shows the results. Table 1 shows that high magnetic properties were obtained.

Comparative Example 2 The raw material coarse powder of the same Sm ₂ Co _17- based rare earth sintered magnet as in Example 2 was jet-milled in a nitrogen gas stream having an oxygen concentration of 10 ppm. Subsequently, the discharged fine powder was recovered in the same vegetable oil as in Example 2 filled in a container installed at the fine powder discharge port of the crusher maintained in a nitrogen gas atmosphere having the same oxygen concentration to prepare a raw material mixture. The ratio of the fine powder (average particle size: 5.0 μm) in this raw material mixture was 85% by weight percentage.
Met. Thereafter, molding, devegetable oil treatment, sintering, and heat treatment were performed under the same conditions as in Example 2 except that this raw material mixture was used, to obtain a sintered magnet of a comparative example. After machining this magnet, the oxygen content, nitrogen content, carbon content, sintered body density and magnetic properties were measured. Table 1 shows the results. Table 1 shows that the sintered body has a higher nitrogen content and a lower iHc and (BH) max than those of Example 2.

Example 3 Nd 27.0%, Pr 3.0%, Dy1.
0%, B1.0%, Nb0.7%, Al0.2%, Ga
R-Fe-B having a main component composition of 0.1% and the balance of Fe
Raw material coarse powder of a rare earth sintered magnet
Jet mill pulverization was performed in an r gas stream. Subsequently, the fractionation point filled in the container provided at the fine powder discharge port of the pulverizer held in the Ar gas atmosphere having the same oxygen concentration is 200 to 30.
The discharged fine powder was collected in a mineral oil (manufactured by Idemitsu Kosan Co., Ltd., trade name: MC.OIL.P-02) having a kinematic viscosity of 2.0 cst at 0 ° C. and normal temperature to prepare a raw material mixture. The ratio of the fine powder (average particle size of 4.2 μm) in this raw material mixture was 7% by weight.
It was 0%. Using this raw material mixture, molding was performed using a molding apparatus shown in FIG. Molding condition is 10K for mold cavity
After applying a magnetic field of Oe, the raw material mixture charged into the pressurized supply device was injected and filled at an injection pressure of 15 kgf / cm ² . After the raw material mixture was filled in the mold cavity, wet molding was performed at a molding pressure of 1.0 ton / cm ² while an orientation magnetic field was applied to obtain a molded body. In this case, the filter is 1mm
Thick cloth was used. Next, 3 × 10
Under a pressure of ^-2 Torr, a demineralized oil treatment is performed at a temperature rise rate of from room temperature to 500 ° C at a rate of 7 ° C / min. ,
The temperature was maintained for 4 hours for sintering. Thereafter, the obtained sintered body was heated in an Ar gas atmosphere at 900 ° C. for 1 hour and 550 ° C.
Heat treatment was performed once each at a temperature of 1 ° C. × 1 hour to obtain a sintered magnet of the present invention. After machining this magnet, the oxygen content, nitrogen content, carbon content, sintered body density and magnetic properties were measured. Table 1 shows the results. Table 1 shows that high magnetic properties were obtained.

Comparative Example 3 The raw material coarse powder of the same R—Fe—B rare earth sintered magnet as in Example 3 was pulverized by a jet mill in a nitrogen gas stream having an oxygen concentration of 5 ppm. Subsequently, the discharged fine powder was recovered in the same mineral oil as in Example 3 filled in the container installed at the fine powder discharge port of the pulverizer maintained in the nitrogen gas atmosphere having the same oxygen concentration to prepare a raw material mixture. The ratio of the fine powder (average particle size: 4.1 μm) in the raw material mixture was 7% by weight.
It was 0%. Thereafter, molding, demineralizing oil treatment, sintering, and heat treatment were performed under the same conditions as in Example 3 except that this raw material mixture was used, to obtain a sintered magnet of a comparative example. After machining this magnet, the oxygen content, nitrogen content, carbon content, sintered body density and magnetic properties were measured. Table 1 shows the results. Table 1
Thus, the nitrogen content of the sintered body was higher than that of Example 3,
It can be seen that iHc and (BH) max are low.

Example 4 Nd 28.3%, Dy 1.0%, B1.0 by weight percentage
%, Nb 1.0%, A10.2%, Co 2.0%, and the raw material powder of the R-Fe-B based rare earth sintered magnet having the main component composition of Fe in an Ar gas stream having an oxygen concentration of 3 ppm. Jet mill pulverization. Subsequently, a mineral oil having a fractionation point of 200 to 300 ° C. and a kinematic viscosity at room temperature of 2.0 cst filled in a container installed at the fine powder discharge port of the pulverizer held in an Ar gas atmosphere having the same oxygen concentration. The discharged fine powder was collected in (made by Idemitsu Kosan, trade name: MC.OIL.P-02) to prepare a raw material mixture. The ratio of the fine powder (average particle size: 4.5 μm) in the raw material mixture was 60% by weight. Using this raw material mixture, molding was performed using a molding apparatus shown in FIG. The molding conditions were as follows: the raw material mixture was scraped and filled in the mold cavity, and then wet-molded at a molding pressure of 1.3 ton / cm ² while applying an orientation magnetic field of 12 KOe to obtain a molded body. In this case, a filter made of cloth having a thickness of 1 mm was used. Next, the molded body is subjected to a demineralized oil treatment at 180 ° C. × 4 hours under a pressure of 5 × 10 ⁻² Torr, and then heated to 1080 ° C. at the same pressure at a rate of 15 ° C./min. It was kept at the temperature for 3 hours and sintered. Next, the obtained sintered body was heated at 900 ° C. for 1 hour in an Ar gas atmosphere for 53 hours.
Heat treatment at 0 ° C. × 1 hour was performed once each to obtain a sintered magnet of the present invention. After machining this magnet, the oxygen content, nitrogen content, carbon content, sintered body density and magnetic properties were measured. Table 1 shows the results. Table 1 shows that good magnetic properties were obtained.

Comparative Example 4 The same raw material powder of the same R—Fe—B rare earth sintered magnet as in Example 4 was jet-milled in a nitrogen gas stream having an oxygen concentration of 3 ppm. Subsequently, the discharged fine powder was recovered in the same mineral oil as in Example 4 filled in the container provided at the fine powder discharge port of the pulverizer held in the nitrogen gas atmosphere having the same oxygen concentration to prepare a raw material mixture. . The ratio of the fine powder (average particle size: 4.3 μm) in the raw material mixture was 6% by weight.
It was 0%. Thereafter, molding, demineralizing oil treatment, sintering, and heat treatment were performed under the same conditions as in Example 4 except that this raw material mixture was used, to obtain a sintered magnet of Comparative Example. After machining this magnet, the oxygen content, nitrogen content, carbon content, sintered body density and magnetic properties were measured. Table 1 shows the results. Table 1
Therefore, the nitrogen content was higher than that of Example 4, and iH
It can be seen that c and (BH) max are low.

[0022]

As described above in detail, according to the present invention, by controlling the content of oxygen, the content of nitrogen and the content of carbon to specific values or less, the magnetic properties are further improved as compared with the prior art. An R—Fe—B based rare earth sintered magnet and a method for manufacturing the same can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing an example of a molding apparatus used in the present invention.

FIG. 2 is a sectional view of a main part showing another example of a molding apparatus used in the present invention.

[Explanation of symbols]

Reference Signs List 1 upper punch, 2 lower punch, 3 die, 4 coil for alignment magnetic field, 5 filter, 6 solvent discharge hole, 7 raw material mixture, 8 pressure supply device, 9 yoke.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01F 1/03-1/08 H01F 41/02 B22F 1 / 00,3 / 00 C22C 33/02

Claims (3)

(57) [Claims] An R-Co ₅ system, an R ₂ -Co ₁₇ system or R-
A raw material powder for a Fe-B-based (R is one or more of rare earth elements including Y) rare earth sintered magnet raw material is crushed in an Ar gas atmosphere having an oxygen concentration of 30 ppm or less, and is obtained by crushing. The recovered fine powder is recovered in a mineral oil, a synthetic oil or a vegetable oil from an Ar gas atmosphere having an oxygen concentration of 30 ppm or less, wet-molded in a magnetic field using a mixture of the recovered fine powder and oil, and then deoiled. A method for producing a rare earth sintered magnet, comprising sintering and heat treating. 2. An R—Fe—B based rare earth sintered magnet (R is Y
And at least one kind of rare earth element containing at least 2,000 ppm of oxygen and 2,000 ppm or less of nitrogen.
00 ppm or less, the carbon content is 1000 ppm or less, and the maximum energy product of more than 42.6 MGOe (B
H) A rare earth sintered magnet having a max. A 3. RCo ₅ system or _R 2 _{Co 17} based rare-earth sintered magnet (R is one or at two or more rare earth elements including Y), the following oxygen content 2000 ppm, nitrogen content is 300 ppm or less, carbon content is 10
Not more than 00 ppm and a maximum of more than 19.7 MGOe
A rare-earth sintered magnet having an energy product (BH) max .