JPH1064712A - R-fe-b rare earth sintered magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain greatly elevated magnetic characteristics by specifying the oxygen and carbon contacts of a rare earth sintered magnet and sintered compact density. SOLUTION: A starting material for an R-Fe-B rare earth sintered magnet (R is at least one of rare earth elements including Y) is weighed, dissolved and cast into ingot in a high frequency melting furnace. The ingot is roughly and finely pulverized, the obtd. powder is dipped in a mineral oil in an nitrogen atmosphere and then wet formed by the so-called lateral magnetic field type press having an orientation magnetic field perpendicular to the compressing direction. The obtd. compact is heat treated into a sintered product having an oxygen content of 3000ppm or less and nitrogen content of 0.1wt.% or less and sintering density of 7.58g/cm<3> or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to reduce the contents of oxygen and carbon, which are unavoidable impurities that form nonmagnetic compounds that do not contribute to the magnet properties, as much as possible to increase the ratio of the main phase and to realize a high density. The present invention relates to an R—Fe—B based rare earth sintered magnet capable of obtaining higher magnetic characteristics than before.

[0002]

2. Description of the Related Art Rare earth sintered magnets dissolve raw metal,
An ingot obtained by pouring into a mold is manufactured using powder metallurgy techniques of pulverization, molding, sintering, heat treatment, and processing. Among them, R-Fe-B based rare earth sintered magnets (R is Y , One or more of the rare earth elements) has attracted attention as a high-performance magnet. However, since the alloy powder for rare earth sintered magnets obtained by pulverizing the ingot is chemically very active, it is very rapidly oxidized in the air and causes deterioration of magnetic properties. In addition, the alloy powder for a rare earth sintered magnet not only generates heat due to rapid oxidation, but also ignites in severe cases, causing a problem in terms of safety. Conventionally, as a method for preventing such rapid oxidation, a treatment for stabilizing the surface by leaving it in an inert gas such as nitrogen or argon for a long time has been performed. There was a problem with sex. Furthermore, the alloy powder for rare earth sintered magnets has a hygroscopic property, and when left in the air, there is a problem that the moisture in the atmosphere is adsorbed and the properties of the manufactured rare earth sintered magnet are deteriorated.

[0003]

In order to solve this problem, Japanese Patent Application Laid-Open No. 61-114505 discloses an R-Fe-B (R is one or two or more rare earth elements including Y) alloy powder and an organic solvent. A method for producing a permanent magnet has been proposed in which a mixture is prepared, the mixture is compressed in a magnetic field, and an organic solvent is filtered to obtain a molded body, which is dried, sintered, and heat-treated. According to this manufacturing method, the problems of oxidation and adsorption of moisture are solved because of the wet molding. In recent years, studies for obtaining higher magnetic properties with R-Fe-B-based permanent magnets have been actively conducted, and the present inventor has also conducted studies using a wet molding method disclosed in JP-A-61-114505. As a result, although the oxygen content is certainly reduced, the use of an organic solvent such as toluene or alcohol can increase the oxygen content of the fine powder or the molded body immersed in the solvent within a relatively short time of about one week. It has been found that there is a problem that the magnetic properties of the sintered body are easily deteriorated. Therefore, an object of the present invention is to reduce the amount of oxygen in a sintered body by preventing the oxidation of fine powder and a molded body and the adsorption of moisture, and to reduce the amount of carbon in a sintered body that degrades magnetic characteristics by reducing the amount of carbon. The volume ratio of the non-magnetic compound which does not contribute to the magnet characteristics in the Fe-B based rare earth sintered magnet is extremely small, and at the same time, the density of the sintered body is substantially reduced to R-Fe.
By densifying it into a very high density region substantially corresponding to the theoretical density of -B magnets, it is possible to provide R-Fe-B rare earth sintered magnets having significantly higher magnetic properties than before. is there.

[0004]

Means for Solving the Problems The present inventors have disclosed Japanese Patent Application Laid-open No. Sho 61
Various investigations were conducted on the cause of the low preservability of the fine powder and the molded product in the wet molding method of -114505, and the following was found. That is, the hydrophilic organic solvent such as alcohol and acetone contains a certain amount of water, and the water reacts with the fine powder and the rare earth element in the compact to form a hydroxide. This becomes an oxide at the time of sintering and causes deterioration of the characteristics of the rare earth sintered magnet. In addition, hydrophobic organic solvents such as toluene and hexane have high oxygen solubility, and the dissolved oxygen in these organic solvents reacts with the fine powder and the rare earth element in the compact to form oxides. Deteriorates. In order to solve these problems, it is necessary that the liquid is a hydrophobic liquid and the solubility of oxygen is small. The present inventors have studied various substances, and as a result satisfying these conditions,
They have found that mineral oils or synthetic oils are suitable, and that these problems can be solved by using these mineral oils and / or synthetic oils. Further, the present inventors have reduced the volume ratio of non-magnetic compounds that do not contribute to the magnet properties by reducing the oxygen content and the carbon content, and have reduced the theoretical density of the R-Fe-B-based rare earth magnet to a very low level. An R—Fe—B-based rare earth sintered magnet having a sound sintered body structure densified in a corresponding sintered body density region can be obtained, that is, the oxygen content is 3000 ppm or less and the carbon content is 0.1 wt% or less, and the sintered body density is 7.58 g
/ Cm ³ or more, it has been found that an R—Fe—B based rare earth sintered magnet having much higher magnetic properties than conventional ones can be obtained. That is, the present invention provides an R—Fe—B system (R is one or more rare earth elements including Y)
Rare earth sintered magnet with oxygen content of 3000ppm
Hereinafter, an R-Fe-B rare earth sintered magnet sintered body density with carbon content is less than 0.1 wt% is characterized in that it is densified to 7.58 g / cm ³ or more. The magnet of the present invention has a very low volume ratio of non-magnetic compounds that do not contribute to the magnet properties, and at the same time has a sintered body density equivalent to the theoretical density of R-Fe-B based magnets, so that it is Thus, it is possible to provide an R-Fe-B-based rare earth sintered magnet having extremely high magnetic properties. Further, in the present invention, in the forming step, an R-Fe-B-based (R is one or more of rare earth elements including Y) rare earth sintered magnet raw material is oriented in the direction of the orientation magnetic field perpendicular to the compression direction. An R-filled into a cavity of a molding die and given magnetic anisotropy
A Fe-B based rare earth sintered magnet having an oxygen content of 30
R- is characterized by having a sintered body density of not more than 00 ppm, a carbon content of not more than 0.1 wt%, a sintered body density of not less than 7.58 g / cm ³ and a maximum energy product of not less than 40 MGOe. It is a Fe-B based rare earth sintered magnet. According to the present invention, 40M by so-called transverse magnetic field molding
R-Fe-B based rare earth sintered magnets of GOe or more can be stably provided. In addition, the present invention relates to a method for forming an R-
A Fe-B-based (R is one or two or more rare earth elements including Y) raw material for a sintered rare earth magnet is filled in a cavity of a molding die in which the direction of the orientation magnetic field is parallel to the compression direction. An R-Fe-B-based rare earth sintered magnet provided with magnetic anisotropy, having an oxygen content of 3000 ppm or less, a carbon content of 0.1 wt% or less, and a sintered body density of 7.58 g. The R-Fe-B based rare earth sintered magnet is characterized in that the density is increased to at least / cm ³ and the maximum energy product is at least 40 MGOe. According to the present invention, R of 40 MGOe or more by so-called longitudinal magnetic field molding
-It is possible to stably provide an Fe-B based rare earth sintered magnet.

Hereinafter, the present invention will be described in detail. The alloy for the rare earth sintered magnet in the present invention may be an R—Fe—B system, but preferably an R—Fe (Co) —BM system.
Represents 25 or more of one or more rare earth elements including Y
~ 35 wt%, B is 0.8-1.2 wt%, M is Al,
Nb, Ti, V, Zr, Mo, W, Ga, Cu, Zn,
One or more of Ge and Sn, 5% by weight or less;
Fe or Fe and Co except for inevitable contaminants
Consists of Nd-Fe-B-Al-N as alloy system
b, Nd-Fe-Co-B-Al-Nb, Nd-Fe-
B-Al-Ga, Nd-Fe-Co-B-Al-Ga,
Nd-Dy-Fe-B-Al-Nb, Nd-Dy-Fe
-Co-B-Al-Nb, Nd-Dy-Fe-B-Al
Examples include -Ga, Nd-Fe-Dy-Co-B-Al-Ga, but are not limited thereto.

A preferred means of producing the magnet of the present invention is a method of preventing oxidation by immersing the raw material powder for the magnet of the present invention in mineral oil or synthetic oil. In the case of dry grinding with a jet mill, etc., install a container filled with mineral oil or synthetic oil at the outlet of the fine powder of the jet mill, and expose the fine powder to mineral oil or inert gas in an inert or reducing atmosphere without contacting the atmosphere. It is desirable that the slurry is directly recovered in the synthetic oil to form a slurry-like mixture. The surface of the fines is shielded from the atmosphere by mineral oil or synthetic oil, preventing oxidation. Needless to say, a mixed oil of a mineral oil and a synthetic oil may be used.

FIG. 1 shows an example of a press apparatus suitable for wet-forming a mixture of the fine powder thus obtained and a mineral oil or a synthetic oil. An example of wet molding using the press device shown in FIG. 1 will be described below. A mixture of fine powder and mineral oil or synthetic oil is filled in the cavity of the mold 1 placed in an intermittent aligning magnetic field, and the fine powder is oriented by applying an aligning magnetic field. When applied, the mineral oil or the synthetic oil is discharged through a filter 4 placed on the lower punch 2 and through a solvent discharge hole 3 provided in the lower punch 2, and the powder is compressed and formed. While the mixture of the fine powder and the mineral oil or the synthetic oil is being compressed, the orientation magnetic field may or may not be applied. However, in order to maintain the orientation of the powder, the mold 1 and the upper and lower punches 5, 2 In order to prevent the fine powder from blowing out together with the mineral oil or synthetic oil from the clearance, it is desirable to maintain the state in which the orientation magnetic field is applied until the compression is completed. FIG. 1 shows a case where the direction of the alignment magnetic field is perpendicular to the compression direction,
A mechanism for generating an orientation magnetic field, that is, an orientation magnetic field coil 6 and a pole piece 7 may be provided so as to be parallel to the compression direction. The method of generating the alignment magnetic field is not limited to these. It is desirable that the mixture of the fine powder and the mineral oil or the synthetic oil be filled into the cavity of the mold 1 while applying pressure. This is because the residual magnetic flux density (Br) and the maximum energy product ((BH) max) are better when pressure filling is performed.
Is a high value. In particular, pressure is applied not only when the direction of the alignment magnetic field in FIG. 1 is perpendicular to the compression direction (so-called transverse magnetic field forming) but also when it is parallel to the compressing direction (so-called vertical magnetic field forming). By filling, (BH) max ≧ 40 MGOe can be stably obtained. That is, R-Fe-
Good magnetic anisotropy is provided by the B-based rare earth sintered magnet.

When the obtained compact is left in the air, the mineral oil or the synthetic oil evaporates to dry out from the surface as the mineral oil or the synthetic oil evaporates. The properties of the rare earth sintered magnet to be used. To prevent this, it is desirable that the compact be stored immediately after compaction in a sintering furnace in mineral oil or synthetic oil or a gas in a non-oxidizing or reducing atmosphere.

Next, when the molded body is sintered, if the temperature is rapidly increased from room temperature to sintering temperature of 950 to 1150 ° C., the temperature of the molded body is rapidly increased, and the mineral oil or synthetic oil remaining in the molded body Reacts with the rare earth elements in the compact to generate rare earth carbides, which prevents the generation of a sufficient amount of liquid phase for sintering, resulting in a sintered body with insufficient density and degraded magnetic properties. is there. In order to prevent this, it is desirable to carry out a demineralized oil or a de-synthetic oil treatment that is maintained at a temperature of 100 to 500 ° C. and a pressure of 10 ⁻¹ Torr or less for 30 minutes or more. By this treatment, mineral oil or synthetic oil remaining in the molded product can be sufficiently removed. The holding is not required to be performed at a single point in the temperature range of 100 to 500 ° C., and may be performed at two or more points. 10 ^-1 T
By applying a demineralized oil or a de-synthetic oil treatment at a temperature rising rate from room temperature to 500 ° C. under a pressure of not more than 10 ° C./min, preferably 5 ° C./min or less under a pressure of not more than 100 ° C. The same effect can be obtained as in the case where the pressure is maintained at a pressure of 10 ^-1 Torr or less for 30 minutes or more. Since the surface of the molded body from which the mineral oil or the synthetic oil has been removed by the above treatment is very active, the molded body enters a sintering furnace without being exposed to the atmosphere and is sintered. In the present invention, as described above, the mineral oil or the synthetic oil can prevent the oxidation of the fine powder and the compact in the steps after the pulverization. Also, the demineralized oil shown above,
By performing the de-synthetic oil treatment, mineral oil and synthetic oil in the molded body can be removed. For this reason, the amount of rare earth oxides and carbides generated in the sintering process is small, and the former is 3000 ppm or less in terms of the oxygen amount of the sintered body, and the latter is 0.1 wt% or less in terms of the carbon amount of the sintered body. be able to. Oxides and carbides generated during sintering are magnetically harmful as nonmagnetic inclusions themselves, hinder crystal grain growth during sintering and lower the density of the sintered body. In the sintered body of the magnet of the present invention in which the generation amount of oxides and carbides is extremely small, densification is easily promoted, and an extremely high density of 7.58 g / cm ³ or more can be obtained.

[0010] Mineral oil or synthetic oil has a fractionation point of 3
50 ° C. or less, kinematic viscosity is 10 at room temperature in view of moldability.
cSt or less, more preferably 5 cSt or less.

[0011]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the contents of the present invention are not limited to these examples. (Example 1) Electrolytic iron, ferroboron, and Nd were weighed in predetermined amounts as starting materials for rare earth sintered magnets, and were melted and cast in a high frequency melting furnace to obtain Nd = 31.% by weight.
An ingot of 0%, B = 1.0%, Al = 0.3%, and the balance Fe was produced. This ingot was roughly pulverized, and then finely pulverized using a jet mill in a nitrogen atmosphere containing 10 ppm of oxygen. The average particle size of the fine powder was 4.1 μm. The fine powder obtained by pulverization has a fractionation point of 2 in a nitrogen atmosphere.
It was immersed in a mineral oil (manufactured by Idemitsu Kosan, trade name: MC OIL P-02) having a kinematic viscosity of 2 cSt at 00 to 300 ° C. and room temperature. This was subjected to wet molding using a so-called transverse magnetic field type press device shown in FIG. 1 in which the direction of the alignment magnetic field was perpendicular to the compression direction. That is, the fine powder immersed in the mineral oil is filled in the cavity of the mold 1, a current is applied to the coil 6 for the aligning magnetic field, and the fine powder in the mineral oil is oriented at the aligning magnetic field strength of 15 kOe. Pressure was applied by a punch 5. Most of the pressurized mineral oil was discharged through the filter 4 and the solvent discharge hole 3 provided in the lower punch 2. Thereafter, the orientation magnetic field current was turned off, and the molded product was taken out and immediately immersed in mineral oil. The obtained compact was taken out from the mineral oil, inserted into a sintering furnace, and heated from room temperature to 150 ° C. at a pressure of 5 × 10 ⁻² Torr at a rate of 1.56 ° C./min. The temperature was raised at 1.5 ° C./min to remove the mineral oil from the compact, and the pressure was 5 × 10 ⁻⁴ Torr to 500
To 1100 ° C. at a rate of 20 ° C./min, kept for 2 hours, and then cooled in a furnace. The obtained sintered body was heated at 900 ° C. for 1 hour for 6 hours.
After heat treatment at 00 ° C. for 1 hour, the sintered body was measured for oxygen content, carbon content, magnetic properties, and sintered density. As shown in Table 1, sufficient properties were obtained (sintered product oxygen content = 1890 ppm, carbon content = 0.03 wt%, Br = 13.5 kG, iHc = 11.
3 kOe, (BH) max = 41.5 MGOe, ρs = 7.5
9 g / cm ³ ) were obtained. (Example 3) Electrolytic iron, ferroboron, and Nd were weighed in predetermined amounts as starting materials for rare earth sintered magnets, and were melted and cast in a high-frequency melting furnace to obtain Nd = 29 by weight%.
%, B = 1.0%, Al = 0.3%, and the remainder was Fe ingot. This ingot was made into a sintered body which was heat-treated in the same process as in Example 1, and the amount of oxygen, the amount of carbon, the magnetic properties, and the density of the sintered body were measured. As shown in Table 1, sufficient properties were obtained. Was done. (Example 5) The compact obtained in Example 1 was stored in the same mineral oil as in Example 1 for one month to obtain a sintered body which was heat-treated in the same process as in Example 1; , Carbon content, magnetic properties, and sintered density were measured, and sufficient properties were obtained as shown in Table 1. (Example 6) The molded body obtained in Example 3 was stored in the same mineral oil as in Example 1 for one week and one month, and was subjected to heat treatment in the same process as in Example 3 to obtain a sintered body. When the amount of oxygen, the amount of carbon, the magnetic characteristics, and the density of the sintered body were measured, sufficient characteristics were obtained as shown in Table 1.

(Comparative Example 1) When the same ingot as in Example 1 was pulverized in the same manner as in Example 1 and opened to the atmosphere without being recovered in mineral oil, it was immediately ignited to recover fine powder. could not. (Comparative Example 2) The same ingot as in Example 1 was pulverized in the same manner as in Example 1 and collected in an airtight container in nitrogen gas.
Fine powder in the atmosphere in which the stabilization treatment time atmospheric pressure nitrogen gas, the orientation magnetic field intensity 15 kOe, and molded at a molding pressure of 1 ton / cm ^2, from room temperature and the resulting molded body 5 × 10 ^-4 Torr 110
The temperature was raised to 0 ° C. at a rate of 20 ° C./min, kept for 2 hours, and then cooled in the furnace. After the obtained sintered body was heat-treated at 900 ° C. for 1 hour and at 600 ° C. for 1 hour, the oxygen amount, carbon amount, magnetic properties, and sintered body density of the sintered body were measured. The results showed that the amount of oxygen was higher than in the examples, and the magnetic properties and the sintered body density were lower than those in the examples. (Comparative Example 3) The same ingot as in Example 1 was pulverized in the same manner as in Example 1 and collected in an airtight container in nitrogen gas.
The fine powder stabilized in a nitrogen gas at atmospheric pressure for a time is molded in the atmosphere at an orientation magnetic field strength of 15 kOe and a molding pressure of 1 ton / cm ² , and the obtained molded body is subjected to a pressure of 5 × 10 ^-4 Torr from room temperature. 1
The temperature was raised to 100 ° C. at a rate of 20 ° C./min, kept for 2 hours, and then cooled in the furnace. The obtained sintered body is heated at 900 ° C. for 1 hour and at 600 ° C. for 1 hour.
After heat treatment for a period of time, the amount of oxygen, the amount of carbon, the magnetic properties, and the density of the sintered body were measured. As shown in Table 1, the amount of oxygen was higher than in the examples, and the density of the sintered body and the magnetic properties were also measured. The result was lower than the example. (Comparative Example 4) The same ingot as in Example 1 was pulverized, recovered in n-hexane, and wet-molded in the same manner as in Example 1,
The obtained molded body is heated from room temperature to 110 at a pressure of 5 × 10 ⁻⁴ Torr.
The temperature was raised to 0 ° C. at a rate of 20 ° C./min, kept for 2 hours, and then cooled in the furnace. After the obtained sintered body was heat-treated at 900 ° C. for 1 hour and at 600 ° C. for 1 hour, the oxygen amount, carbon amount, magnetic properties, and sintered body density of the sintered body were measured. Although the amount of oxygen was slightly higher than that of the example, the amount of carbon was high and the density of the sintered body was small, and the magnetic properties were lower than those of the example. (Comparative Example 5) The same ingot as in Example 1 was pulverized in the same manner as in Example 1, collected in n-hexane, and wet-molded.
After storage for one week and one month in n-hexane, a sintered body was heat-treated in the same process as in Example 1. When the oxygen content, carbon content, magnetic properties, and sintered density of the obtained sintered body were measured, the carbon content and the sintered density were the same as those in Example 1, but the oxygen content was higher than that in Example 1. Example 1
Lower results were obtained.

[0013]

[Table 1]

Example 7 As starting materials for a rare earth sintered magnet, electrolytic iron, ferroboron, and Nd were weighed to a predetermined amount.
By melting and casting in a high frequency melting furnace, Nd = 31%, B = 1.0%, Al = 0.3%, and the balance F by weight%
e was produced. This ingot is roughly pulverized, and then the oxygen content of the atmosphere is 10 pp using a jet mill.
Milled in m2 nitrogen. Average particle size of fine powder is 4.0μ
m. The fine powder obtained by the pulverization was immersed in a synthetic oil (manufactured by Idemitsu Kosan Co., Ltd., trade name: Daphne Cleaner H) having a fractionation point of 200 to 300 ° C. and a kinematic viscosity of 2 cSt at room temperature in a nitrogen atmosphere. This was subjected to molding, sintering, and heat treatment under the same conditions as in Example 1, and the oxygen content, carbon content, magnetic properties, and sintered density of the sintered body were measured. As shown in Table 2, sufficient properties were obtained. Obtained.

(Embodiment 8) As starting materials for a rare earth sintered magnet, electrolytic iron, ferroboron, and Nd were weighed in predetermined amounts.
An ingot consisting of Nd = 31.0%, B = 1.0%, Al = 0.3% and the balance Fe by weight was manufactured by melting and casting in a high frequency melting furnace. This ingot is roughly pulverized, and the oxygen content of the atmosphere is reduced to 1 using a jet mill.
Milled in 0 ppm nitrogen. The average particle size of the fine powder is 4.
It was 2 μm. The fine powder obtained by pulverization has a fractionation point of 200 to 300 ° C. in a nitrogen atmosphere and a kinematic viscosity at room temperature of 2.0.
cSt mineral oil (made by Idemitsu Kosan, trade name: MC OIL
P-02). Next, a so-called vertical magnetic field type press device having upper and lower punches having the same structure as that shown in FIG. 1, but provided with an aligning magnetic field coil and a pole piece so that the direction of the aligning magnetic field is parallel to the compression direction is provided. The immersion raw material was injected into the cavity to be used for molding. Specifically, using a dice having a raw material injection port, 10 kgf was applied to the cavity to which a magnetic field of 10 kOe was applied via the injection port.
The immersion raw material was injected under pressure at a pressure of / cm ² . After the injection, molding was performed with a pressure of 1 ton / cm ² while maintaining the applied magnetic field to obtain a molded body. The obtained compact was thereafter subjected to sintering and heat treatment under the same conditions as in Example 1, and the oxygen content, carbon content, magnetic properties, and sintered density of the sintered compact were measured. Characteristics were obtained.

Example 9 As starting materials for a rare earth sintered magnet, electrolytic iron, ferroboron, ferroniob, Nd,
By weighing a predetermined amount of Dy, melting and casting in a high frequency melting furnace, Nd = 29.0% by weight%, Dy = 2.0
%, B = 1.0%, Al = 0.3%, Nb = 0.3%,
An ingot having a balance of Fe was manufactured. This ingot was roughly pulverized, and then finely pulverized using a jet mill in a nitrogen atmosphere containing 10 ppm of oxygen. The average particle size of the fine powder was 4.0 μm. Mineral oil having a fractionation point of 200 to 300 ° C. and a kinematic viscosity of 2.0 cSt at room temperature (made by Idemitsu Kosan, trade name: MC O
ILP-02). Then, molding was performed under the same conditions as in Example 8, and sintering and heat treatment were further performed under the same conditions to measure the oxygen content, carbon content, magnetic properties, and sintered density of the sintered body. Sufficient characteristics were obtained.

(Example 10) Electrolytic iron, Co, Ga, ferroboron, ferroniob, Nd, Pr, and Dy are weighed as predetermined starting materials for a rare earth sintered magnet, and are melted and cast in a high frequency melting furnace. Nd = 3% by weight
0.0%, Pr = 0.5%, Dy = 1.0%, B = 1.
0%, Al = 0.3%, Nb = 0.3%, Co = 2.0
%, Ga = 0.1%, with the balance being Fe. This ingot was roughly pulverized, and then finely pulverized using a jet mill in a nitrogen atmosphere containing 10 ppm of oxygen.
The average particle size of the fine powder was 4.1 μm. The fine powder obtained by pulverization has a fractionation point of 200 to 300 ° C. in a nitrogen atmosphere,
Mineral oil with a kinematic viscosity of 2.0 cSt at room temperature (Idemitsu Kosan,
(Product name: MC OIL P-02). Then, molding was performed under the same conditions as in Example 8, and further sintering and heat treatment were performed under the same conditions, and the oxygen content, carbon content, magnetic characteristics,
When the density of the sintered body was measured, sufficient characteristics were obtained as shown in Table 2.

Example 11 As starting materials for rare earth sintered magnets, electrolytic iron, ferroboron, ferroniob, N
A predetermined amount of d and Dy is weighed, melted and cast in a high-frequency melting furnace, so that Nd = 29.0% by weight and Dy =
2.0%, B = 1.0%, Al = 0.3%, Nb = 0.
An ingot consisting of 3% and the balance Fe was produced. This ingot was roughly pulverized, and then finely pulverized using a jet mill in a nitrogen atmosphere containing 10 ppm of oxygen. The average particle size of the fine powder was 3.8 μm. The fine powder obtained by pulverization was immersed in a nitrogen atmosphere in a synthetic oil having a fractionation point of 200 to 300 ° C. and a kinematic viscosity at room temperature of 2.5 cSt (trade name: Daphne Cleaner H, manufactured by Idemitsu Kosan Co., Ltd.). Then, molding was performed under the same conditions as in Example 8, and sintering and heat treatment were further performed under the same conditions to measure the oxygen content, carbon content, magnetic properties, and sintered density of the sintered body. Sufficient characteristics were obtained.

[0019]

[Table 2]

[0020]

As described in detail above, the R-Fe of the present invention
-B-based rare earth sintered magnets have the following distinguished and excellent effects, and are extremely useful as they can greatly contribute to the high performance of various magnet applied products. (1) R-Fe-B-based rare earths by preventing oxidation of fine powder and compacts and adsorption of moisture to reduce the amount of oxygen in the sintered body and the amount of carbon in the sintered body that deteriorates magnetic properties. 6. The volume ratio of the non-magnetic compound which does not contribute to the magnet characteristics in the sintered magnet is extremely small, and the density of the sintered body substantially corresponds to the theoretical density of the R-Fe-B based magnet.
By densifying to a high-density region of 58 g / cm ³ or more, R-Fe
-It has become possible to provide a B-based rare earth sintered magnet. (2) Only transverse magnetic field molding is used as the molding means to prevent oxidation of fine powder and compacts and adsorption of moisture, thereby reducing the oxygen content of the sintered compact and reducing the carbon content of the sintered compact which deteriorates the magnetic characteristics. By doing so, the volume ratio of the non-magnetic compound which does not contribute to the magnet properties in the R-Fe-B based rare earth sintered magnet is extremely reduced, and at the same time, the sintered body density is substantially reduced to R-Fe.
7.58 g / cm ³ which approximately corresponds to the theoretical density of a B-based magnet
By densifying to the above high density region, 40MGOe
It has become possible to provide an R-Fe-B based rare earth sintered magnet having the above high magnetic properties. (3) Only vertical magnetic field molding is used as the molding means to prevent oxidation of fine powder and compacts and adsorption of moisture, thereby reducing the oxygen content of the sintered compact and reducing the carbon content of the sintered compact which deteriorates the magnetic properties. By doing so, the volume ratio of the non-magnetic compound which does not contribute to the magnet properties in the R-Fe-B based rare earth sintered magnet is extremely reduced, and at the same time, the sintered body density is substantially reduced to R-Fe.
7.58 g / cm ³ which approximately corresponds to the theoretical density of a B-based magnet
By densifying to the above high density region, 40MGOe
It has become possible to provide an R-Fe-B based rare earth sintered magnet having the above high magnetic properties.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part showing an example of a press apparatus suitable for manufacturing an R—Fe—B based rare earth sintered magnet of the present invention.

[Explanation of symbols]

1 mold, 2 lower punches, 3 solvent discharge holes, 4 filters, 5 upper punches, 6 orientation magnetic field coils, 7 pole pieces.

Claims (3)

[Claims] An R—Fe—B-based (R is one or two or more rare earth elements including Y) sintered rare earth magnet having an oxygen content of 3000 ppm or less and a carbon content of 0.1 wt%. And the sintered body density is 7.58
g / cm ³ or more.
Fe-B based rare earth sintered magnet. 2. In the forming step, an R-Fe-B-based (R is one or more of rare earth elements including Y) rare earth sintered magnet raw material is oriented in the direction of the orientation magnetic field perpendicular to the compression direction. An R-Fe-B based rare earth sintered magnet filled in a cavity of a molding die and given magnetic anisotropy, wherein the content of oxygen is 3000 ppm or less and the content of carbon is 0.1 wt% or less. And the sintered body density is 7.58
g / cm ³ or more, and the maximum energy product is 40 MGOe or more.
-B type rare earth sintered magnet. 3. An R-Fe-B-based (R is one or more rare earth elements including Y) rare earth sintered magnet raw material in the forming step, and the direction of the orientation magnetic field is parallel to the compression direction. An R-Fe-B based rare earth sintered magnet filled in a cavity of a molding die and given magnetic anisotropy, wherein the content of oxygen is 3000 ppm or less and the content of carbon is 0.1 wt% or less. And the sintered body density is 7.58
g / cm ³ or more, and the maximum energy product is 40 MGOe or more.
-B type rare earth sintered magnet.