JP3413789B2 - R-Fe-B sintered permanent magnet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a high magnetic property, a bending strength and / or a residual magnetic flux density.
(Br) temperature coefficient (α), intrinsic coercive force (iHc) temperature coefficient (β)
The present invention relates to an R-Fe-B system sintered permanent magnet with improved characteristics.

[0002]

2. Description of the Related Art Among sintered rare earth permanent magnets, R-Fe-B type sintered permanent magnets have attracted attention as high-performance magnets and are used in a wide range of fields. This R-Fe-B sintered permanent magnet is basically composed of R ₂ Fe ₁₄ B phase (main phase), RFe ₇ B ₆ phase (Brich phase), and R ₈₅ Fe.
_It has a structure consisting of 3 phases of ₁₅ phases (Rrich phase).

Sintering type rare earth permanent magnets containing R-Fe-B system are powder metallurgy in which raw metal is melted and an ingot obtained by pouring in a mold is crushed, molded, sintered, heat treated and processed. It is generally manufactured by a conventional process. However, the alloy powder obtained by crushing the ingot is chemically very active because it contains a large amount of rare earth elements, and is oxidized in the atmosphere to increase the oxygen content. As a result, in the sintered body after sintering, a part of the rare earth element forms an oxide, and the magnetically effective rare earth element is reduced, so that a practical magnetic characteristic level, for example, iHc ≧ 13KOe is realized. It is necessary to increase the amount of rare earth element in the R-Fe-B system sintered permanent magnet, and the addition amount of rare earth element exceeding 31% by weight is adopted in practical materials. Therefore, the conventional
The bending strength and temperature coefficient (α, β) of the magnetic properties of the R-Fe-B sintered permanent magnet were not sufficient.

For example, Japanese Unexamined Patent Publication No. 7-86015 discloses an Nd-Fe-B system sintered permanent magnet manufactured by pulverizing hexane as a wet pulverizing medium and then performing a predetermined manufacturing process. Four
Point bending strength 30.5-47.4 kg / mm ² , oxygen concentration in magnet 0.10
.About.0.30 wt% and (BH) max of 20.4 to 34.8 MGOe are disclosed. However, what about the content of carbon inevitably mixed from hexane etc. of the finely pulverized medium and the microstructure of the obtained Nd-Fe-B system sintered permanent magnet and the temperature coefficient of magnetic properties, and the correlation with bending strength Not considered.

Further, JP-A-62-133040 discloses an R-Fe-B type sintered permanent magnet containing O in an amount of less than 0.3% and C in an amount of 0.05% by weight. There is no suggestion of the temperature coefficient of strength or magnetic properties.

Japanese Patent Publication No. 5-18895 discloses an R-Fe-B sintered permanent magnet obtained by aging a primary sintered body and then hot isostatic pressing with an inert gas as a pressure medium. It has been disclosed that the mechanical strength and the maximum energy product exceeding 40 MGOe were realized by densifying the alloy, the contents of O and C which are unavoidable impurities, and the temperature coefficient of the microstructure and magnetic properties of the sintered body, No consideration has been given to the correlation with bending strength.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to find the contents of O and C which are inevitable impurities in the above-mentioned conventional unexamined area, that is, the R-Fe-B system sintered permanent magnet and the sintered body thereof. By grasping the correlation between the microstructure and the temperature coefficient (α, β) of magnetic properties, and bending strength, bending strength and magnetic properties can be maintained while maintaining high magnetic properties without the need for hot isostatic pressing. R-Fe-B with improved temperature coefficient (α, β)
A sintered sintered permanent magnet is provided.

[0008]

Means for Solving the Problems As a result of intensive investigations by the present inventors in order to improve the bending strength and the temperature coefficient of magnetic characteristics of an R-Fe-B system sintered permanent magnet, O, which is an unavoidable impurity, The C content is kept as low as possible, and at the same time, the main phase crystal grains of the R-Fe-B system sintered permanent magnet have a specific grain size distribution. The inventors have found that the strength and the temperature coefficient of magnetic properties are improved, and have arrived at the present invention.

That is, according to the present invention, R (R is Y
2 or more of rare earth elements including) 27.0
~ 31.0%, B 0.5 ~ 2.0%, O 0.25% or less, C 0.15%
Below, the area of the main phase crystal grains having the composition of the balance Fe and the sum of the areas of the main phase crystal grains having a grain size of 10 μm or less with respect to the total area of the main phase crystal grains of 80% or more and the grain size of 13 μm or more Is 10% or less and has a high density of 7.60 g / cm ³ or more, which is an R-Fe-B based sintered permanent magnet. With this configuration,
It can hold a three-point bending strength exceeding 300 N / mm ² . Further, the temperature coefficient (α) of the residual magnetic flux density (Br) at 297 to 393 K and the temperature coefficient (β) of the intrinsic coercive force (iHc) are α = -0.081 to -0.089% / K, β = -0.516 to -0.551%
It can be / K.

Since the magnet of the present invention has a very low O and C content, it is possible to perform the longitudinal magnetic field forming or transverse magnetic field formation which is described later without the need for densification treatment such as hot isostatic pressing. The density of the sintered body can be increased to 7.60 g / cm ³ or more, which is equivalent to the theoretical density of the R-Fe-B system sintered permanent magnet, by molding, followed by desolvation and sintering treatment. Therefore, iHc ≥ 1 in the magnetic characteristics measured at room temperature 293K.
3kOe and (BH) max of 35MGOe or more, preferably 40MGOe
e or more, more preferably 45 MGOe or more, particularly preferably 50 M
Can be more than GOe.

Further, the magnet of the present invention contains N in weight percentage.
When it is contained 0.02 to 0.15%, good corrosion resistance is given.

In addition, a part of Fe of the magnet of the present invention is Nb 0.1-2.0%, Al 0.02-2.0%, Co 0.3-5.
The magnetic characteristics can be improved by substituting one or more of 0%, Ga 0.01 to 0.5%, and Cu 0.01 to 1.0%.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below, but the present invention is not limited to the following.

There are various methods for defining and measuring the crystal grain size of the magnet of the present invention, and although it is not unambiguous, the present inventors have found that the grain size with respect to the total area of the main phase (R ₂ Fe ₁₄ B phase). Shows the crystal grain size distribution of the main phase by the ratio of the sum of the areas of the main phase crystal grains having a grain size of 10 μm or less and the ratio of the sum of the areas of the main phase grains having a grain size of 13 μm or more to the total area of the main phase. When used as a scale,
It was found that the bending strength and the temperature coefficient (α, β) greatly changed by this scale. This measurement is the target R-
The crystal structure of the Fe-B system sintered permanent magnet was observed with a microscope (trade name VANOX) manufactured by OLYMPUS, and this image was directly put into an image processing device (trade name LUZEX2) manufactured by NIRECO and evaluated.

FIG. 1 is a weight percentage of Nd 27.5%, Pr 0.5
%, Dy 1.5%, B 1.1%, Al 0.1%, Co 2.0%, Ga 0.08
%, N 0.06%, O 0.16%, C 0.06%, N 0.040%, balance Fe
And the grain size is 10 μm with respect to the total area of the main phase.
The sum of the areas of the following main phase crystal grains is 96%, and the crystal grain size is 13 μm
It is an observation result by an optical microscope (magnification: 1000 times) of the sintered permanent magnet of the present invention in which the sum of the areas of the main phase crystal grains is 1%. In addition, FIG. 2 shows that the sum of the areas of the main phase crystal grains having the same composition and the crystal grain size of 10 μm or less with respect to the total area of the main phase is 64
%, The sum of the areas of the main phase crystal grains with a grain size of 13 μm or more is 17
% Of the sintered permanent magnet of the comparative example (magnification 1000
Times).

Generally, in the manufacture of R-Fe-B system sintered permanent magnets, raw material coarse powder is finely pulverized, and the fine powder is compacted in a predetermined mold in a magnetic field to obtain a compact, and then sintered. Then, a method of forming a sintered body is adopted. When the raw material suitable for obtaining the magnet of the present invention is finely pulverized by using a jet mill, the magnet of the present invention is controlled by controlling the pressure of the finely pulverizing medium gas, the supply rate of coarse powder, and the like. It is possible to obtain a fine powder having an average particle size and a particle size distribution of, and manufacture using this fine powder. Moreover, the particle size distribution of the fine powder can be controlled by performing classification as necessary.

The inventors of the present invention have studied the production means suitable for mass production because the crystal grain size distribution of the main phase of the R-Fe-B system sintered permanent magnet can be set within the above specified range. The inventors have found a method of heat-treating an R-Fe-B-based quenched ribbon having a predetermined composition produced by a so-called strip casting method in a predetermined temperature range and coarsely pulverizing this to obtain a raw material coarse powder. Further, when crushing the ribbon-shaped alloy after the heat treatment, it was confirmed that it is effective to enhance the fine crushing performance by performing natural decomposing by hydrogen absorption and then performing dehydrogenation treatment. Figure 3 shows Nd 27.8%, Pr 0.45%, Dy by weight percentage.
1.7%, B 1.05%, Al 0.05%, Co 2.05%, Ga 0.08
%, Cu 0.09%, O 0.02%, N 0.004%, C 0.007%, balance
It is a cross-sectional structure of an as-cast steel ribbon having an Fe composition and manufactured by a strip casting method.
There is a dendrite-like fine structure. In the photograph, the phase observed in white has a small amount of rare earth and corresponds to the main phase of this alloy, and the phase observed in black has a large amount of rare earth and corresponds to the Rrich phase of this alloy. Since this Rrich phase becomes a starting point of fracture during fine pulverization, when a strip-shaped alloy in which this Rrich phase is finely dispersed is used, a fine powder with a fine particle size is generated stochastically. It's easy to do. However, even if this ribbon-shaped alloy was directly used as raw material coarse powder as it was in rapid cooling casting and then finely pulverized, fine powder with a good particle size distribution could not be obtained. With the bonded permanent magnet, the grain size distribution of the main phase crystal grains intended by the present invention cannot be obtained. The reason for this is that the surface of the ribbon-shaped alloy is hardened by the quenching casting, and the pulverizability during fine pulverization is remarkably deteriorated.

The present inventors have found that as a means for solving this problem, the hardened portion of the surface of the ribbon-shaped alloy can be removed by heat-treating the ribbon-shaped alloy within a specific temperature range.
The heat treatment temperature is preferably 800 to 1100 ° C. The heat treatment time should be at least 15 minutes or longer, preferably 30 minutes or longer. This is because if the heat treatment temperature is lower than 800 ° C, the hardened portion is not sufficiently removed. Further, at a temperature higher than 1100 ° C., a reaction occurs between the ribbon-shaped alloys during the heat treatment, which makes it difficult to perform the treatment in the subsequent step. Needless to say, the heat treatment must be performed in an inert gas atmosphere or in a vacuum because it is a ribbon-shaped alloy containing a large amount of active rare earth elements. Further, as described above, it is an effective means to improve fine pulverizability by causing the strip-shaped alloy after heat treatment to occlude hydrogen to spontaneously disintegrate, dehydrogenating and then coarsening this. This is because, in addition to the effect of removing the hardened portion on the surface of the ribbon alloy by the heat treatment, the effect of embrittlement of mainly the Rrich phase inside the ribbon alloy by hydrogen is added. By heat-treating the strip-shaped alloy produced by the strip casting method and using it, an R-Fe-B based sintered magnet having a main phase grain size distribution as claimed in the claims is obtained. Figure 4
Is a thin plate alloy manufactured by the strip casting method.
It is an example of a cross-sectional photograph of a state in which the magnet of the present invention is heat-treated at 900 ° C. to be in a suitable state.

Next, the reasons for limiting the composition of the R-Fe-B system sintered permanent magnet of the present invention will be described. The amount of rare earth element (R) is a percentage by weight reflecting the following low oxygen content and low carbon content.
It is set to 27.0 to 31.0%. When the amount of rare earth element exceeds 31.0%, the amount of Rrich phase inside the sintered body increases, and the morphology becomes coarse, resulting in poor corrosion resistance. On the other hand, if the amount of rare earth element is less than 27.0%, the amount of liquid phase required for densification of the sintered body is insufficient, the density of the sintered body decreases, and at the same time, Br and iHc decrease. The content of oxygen (O) is 0.05 to 0.25% by weight. When the oxygen content exceeds 0.25%, the oxide formation ratio of the rare earth element increases, the magnetically effective rare earth element content decreases, and iHc and the sintered body density decrease. on the other hand,
Since the level of O content of the ingot to be melted is usually 0.04% or less, it is difficult to set the O content of the sintered body to this value or less, and the O content is preferably 0.05 to 0.25%. The amount of carbon (C) is 0.01 to 0.15% by weight. When the amount of C is more than 0.15%, a large amount of rare earth element carbides are formed, and as a result, the magnetically effective rare earth element content is reduced, and iHc and the sintered body density are reduced. The C content is more preferably 0.12% or less, and particularly preferably 0.10% or less. On the other hand, the level of C content of ingots is usually
It is 0.008% or less, and it is difficult to set the C content of the sintered body to this value or less, and the C content of the sintered body is set to 0.01 to 0.15%.
A specific method of setting the O amount and C amount of the magnet of the present invention within the above specific range will be described later.

In the magnet of the present invention, a part of Fe may be replaced with one or more of Nb, Al, Co, Ga and Cu. The reasons for limiting the substitution amount of each of the above elements shown in weight percentage will be described below. The substitution amount of Nb is set to 0.1 to 2.0%. The addition of Nb produces Nb boride during the sintering process, which suppresses abnormal grain growth. When the Nb substitution amount is less than 0.1%, the effect of suppressing abnormal grain growth of crystal grains becomes insufficient. On the other hand, when the substitution amount of Nb exceeds 2.0%, the production amount of boride of Nb increases, so that Br remarkably decreases. The substitution amount of Al is 0.02 to 2.0%. Addition of Al has the effect of increasing iHc. When the Al substitution amount is less than 0.02%, the iHc improving effect is small, and when it exceeds 2.0%.
Br drops sharply. The substitution amount of Co is 0.3 to 5.0%. The addition of Co brings about the improvement of the Curie point, that is, the temperature coefficient of the saturation magnetization. When the substitution amount of Co is less than 0.3%, the effect of improving the temperature coefficient is small. If the substitution amount of Co exceeds 5.0%, Br and iHc decrease sharply. The substitution amount of Ga is 0.01 to 0.5%. Addition of a small amount of Ga brings about an improvement in iHc, but when the substitution amount is less than 0.01%, iHc
No improvement effect is recognized. On the other hand, the substitution amount of Ga is 0.5%
When it exceeds, the decrease of Br becomes remarkable and the iHc also decreases. Cu
The amount of substitution is 0.01 to 1.0%. The addition of a small amount of Cu brings about the improvement of iHc, but the effect of improving iHc becomes saturated when the substitution amount exceeds 1.0%. If the amount added is less than 0.01%, the effect of improving iHc is not observed.

Next, a method of controlling the amount of N which imparts good corrosion resistance to the magnet of the present invention will be described. There are various methods for controlling the N content of the R-Fe-B system sintered permanent magnet, and an appropriate method among them can be selected for the present invention, and is not limited. For example, R-Fe-B in a jet mill grinder
Was charged with raw meal for the system sintered permanent magnets, then the internal jet mill as the oxygen concentration in the Ar gas was replaced with Ar gas is substantially 0%, then N ₂ gas Is introduced to adjust the concentration of N ₂ gas in Ar gas (usually 0.0001 ~
0.1 vol% range). During the process of finely pulverizing the raw material coarse powder in the Ar gas atmosphere containing a small amount of N ₂ gas, the rare earth element and N in the raw material are mainly combined, and the amount of N in the recovered fine powder increases. The fine powder can be collected by coating the fine powder with a jet mill and collecting a container filled with a solvent that is a mixture of two or more mineral oils, vegetable oils, synthetic oils, etc. that can completely prevent the progress of oxidation. Place in the mouth and collect fine powder directly in the solvent in Ar gas atmosphere. The slurry-like raw material thus obtained is wet-molded in a predetermined mold in a magnetic field to obtain a molded body. Next, this molded body is heated to a temperature of about 200 ° C. in a vacuum furnace under a vacuum degree of about 5 × 10 ^-2 torr to remove the solvent contained in the molded body. Then continue to increase the temperature of the vacuum furnace to 11
The sintering temperature is raised to around 00 ° C. and sintered under a vacuum degree of about 5 × 10 ⁻⁴ torr to obtain a sintered body. After that, through a predetermined heat treatment or the like, an R-Fe-B system sintered permanent magnet having an O content of 0.25% or less and a C content of 0.15% or less can be obtained. In this case, the control of the amount of N in the sintered body is performed by controlling the concentration of the introduced N ₂ gas in the Ar gas at the time of crushing the jet mill. The degree of incorporation of N into the raw material changes depending on the capacity of the jet mill, the composition and amount of the raw material coarse powder charged, and the feed amount of the raw material coarse powder during jet mill pulverization. Therefore, in order to obtain the target amount of the sintered body N, it is necessary to determine the optimum N ₂ gas concentration in Ar gas and perform the jet mill grinding. In this way, the amount of N in the sintered body
It can be controlled to 0.02 to 0.15%.

Further, the oxygen concentration of the N ₂ gas inside the jet mill was replaced with N ₂ gas is substantially set to be 0%, comminuting raw meal in the N ₂ gas atmosphere , 0 content is 0.25% or less, C content is 0.15% or less, N content is 0.02 ~
0.15% of R-Fe-B system sintered permanent magnet is obtained. In this case, the mixing degree of N in the raw material is controlled by the charging amount of the raw material coarse powder and the feed amount of the raw material coarse powder at the time of fine pulverization to obtain a target N amount of sintered body. Since the mixing degree of N in the raw material changes depending on the type and capacity of the jet mill, the conditions are set in advance and the charging amount of the raw material coarse powder and the feed amount during fine pulverization are set. The method of recovering the finely pulverized powder is into a solvent such as mineral oil, vegetable oil, or synthetic oil, and the oxidation of the fine powder during the recovery from the solvent to the sintering is prevented. The above-mentioned atmosphere in which the oxygen concentration is substantially 0% means, for example, that R-Fe-B raw material coarse powder is
In the case of a production type jitt mill crusher that has the ability to finely pulverize about 0 kg / hour, the oxygen concentration in the atmosphere is 0.01 vol.
% Or less, more preferably 0.005 vol% or less, still more preferably 0.002 vol% or less. By the above method, O content is 0.25% or less, C content is 0.15% or less, N content is 0.0
A 2 to 0.15% R-Fe-B system sintered body can be produced, and at the same time, a quenched ribbon-shaped alloy having a predetermined composition that has been heat-treated in the temperature range of 800 to 1100 ° C described above is used as a raw material. Thus, the main phase crystal grain size distribution described in the claims can be obtained with good reproducibility. By subjecting the thus obtained sintered body to predetermined heat treatment, processing, surface treatment, etc.,
An R-Fe-B sintered permanent magnet having high magnetic properties and improved bending strength and temperature coefficient of magnetic properties can be obtained.

(Example 1) Nd 27.0%, Pr by weight percentage
0.5%, Dy 1.5%, B 1.05%, Nb 0.35%, Al 0.08%, C
o 2.5%, Ga 0.09%, Cu 0.08%, O 0.03%, C 0.005
%, N 0.004%, balance Fe composition, thickness 0.2-0.5
A strip alloy of mm was produced by the strip casting method.
This ribbon-shaped alloy was heated in an Ar gas atmosphere at 1000 ° C. for 2 hours. Next, using a hydrogen furnace, this ribbon-shaped alloy was allowed to occlude hydrogen at room temperature in a hydrogen gas atmosphere and naturally collapsed. Then, while the vacuum in the furnace was evacuated, the ribbon-shaped alloy was heated to 550 ° C., and was held at that temperature for 1 hour for dehydrogenation treatment. The collapsed alloy was mechanically crushed in a nitrogen gas atmosphere to obtain a raw material powder of 32 mesh under. Analysis of this raw material coarse powder showed that the weight percentage was Nd 27.0%, Pr 0.5%, D
y 1.5%, B 1.05%, Nb 0.35%, Al 0.08%, Co 2.5
%, Ga 0.09%, Cu 0.08%, O 0.12%, C 0.02%, N 0.
The analytical values were 008% and balance Fe. After charging the raw material coarse powder 80kg in a jet mill, the inner jet mill was replaced with N ₂ gas, substantially 0% of oxygen concentration in the N ₂ gas and (0.001 vol% oxygen analyzer value) did. Then, crushing pressure 7.0 kg / c
Jet milling was performed under the conditions of m ² and a raw material coarse powder supply rate of 10 kg / hour. The average particle size of the fine powder was 3.9 μm. A container filled with mineral oil (trade name Idemitsu Super Sol PA-30, manufactured by Idemitsu Kosan) was installed directly at the fine powder recovery port of the jet mill, and N ₂
Fine powder was recovered directly in mineral oil in a gas atmosphere. The raw material after recovery has a fine content of 80% by adjusting the amount of mineral oil.
It was a raw material slurry of wt%. This raw material slurry was wet-molded at a molding pressure of 0.8 ton / cm ² while applying an orientation magnetic field of 12 kOe in a predetermined mold cavity. The application direction of the orientation magnetic field is perpendicular to the molding direction. In addition, a large number of solvent discharge holes were provided in the upper punch of the die, and a 1 mm-thick cloth filter was applied to the upper punch surface during molding. Next, the obtained molded body was heated at a temperature of 200 ° C. in a vacuum of 5.0 × 10 ^-2 torr.
Heat for 1 hour to remove mineral oil content, then 4.0 × 10 ^-4 to
Under the condition of rr, the temperature is raised to 1070 ° C at a heating rate of 15 ° C / min,
The temperature was maintained for 3 hours for sintering. This sintered body was heat-treated once at 900 ° C. × 2 hours and 480 ° C. × 1 hour each in an Ar gas atmosphere to obtain a sintered permanent magnet of the present invention. When the composition of this sintered magnet was analyzed, it was found that the weight percentage was Nd 27.0%, P
r 0.5%, Dy 1.5%, B 1.05%, Nb 0.35%, Al 0.08
%, Co 2.5%, Ga 0.09%, Cu 0.08%, O 0.16%, C 0.
The analytical values were 07%, N 0.055% and balance Fe. The crystal grain size of this sintered magnet is 10μ with respect to the total area of the main phase crystal grains.
The sum of the areas of the main phase crystal grains of m or less is 93%, and the crystal grain size is 13μ.
The sum of the areas of the main phase crystal grains of m or more was 4%. Magnetic properties and sintered body density (ρs) at 293K after machining were measured. Br = 14.0 to 14.2kG, iHc = 14.2 to 14.3kOe, (B
Good values of (H) max = 47.2 to 47.6 MGOe and ρs = 7.60 to 7.62 g / cm ³ were obtained. Further, the temperature coefficient of Br of the magnet of the present invention measured at 297 to 393 K, α = −0.081 to −0.083%
/ K, iHc temperature coefficient β = -0.540 to -0.546% / K. Next, a total of 20 rectangular plate-shaped bending test pieces having a length of 40 mm, a width of 10 mm, and a length of 5 mm (the length direction is the direction of magnetic anisotropy) were obtained from any of the obtained magnets of the present invention. Using an Autograph AG-5000A (manufactured by Shimadzu Corp.), the three-point bending strength was measured at 293K based on JIS 1601-1981, and a good value of 320 to 325 N / mm ² was obtained. The obtained magnet of the present invention was processed into a rectangular block having a length of 8 mm × a width of 8 mm × a thickness of 2 mm, and a Ni-plated film having a film thickness of 10 to 20 μm was applied to the surface of the block to produce 2 atm × 120 ° C. × relative humidity. Ten
It was left in the condition of 0% and the degree of peeling of the Ni plating was examined with the passage of time.
No abnormalities were found in the plating, indicating good corrosion resistance.

(Example 2) Nd 22.3%, Pr by weight percentage
2.0%, Dy 5.5%, B 1.0%, Nb 0.5%, Al 0.2%, Co
2.0%, Ga 0.09%, Cu 0.1%, O 0.02%, C 0.005%, N
A strip-shaped alloy with a composition of 0.003% and the balance of Fe and a thickness of 0.2 to 0.4 mm was prepared by the strip casting method. This ribbon-shaped alloy was heated at 1100 ° C. for 1 hour in an Ar gas atmosphere. Next, using a hydrogen furnace, this ribbon-shaped alloy was allowed to occlude hydrogen at room temperature in a hydrogen gas atmosphere and naturally collapsed. Then, while the vacuum in the furnace was evacuated, the ribbon-shaped alloy was heated to 550 ° C., and was held at that temperature for 1 hour for dehydrogenation treatment.
Mechanically crush the collapsed alloy in a nitrogen gas atmosphere,
Raw material for 32 mesh under. When this raw material powder was analyzed, Nd 22.3%, Pr 2.0%, Dy
5.5%, B 1.0%, Nb 0.5%, Al 0.2%, Co 2.0%, Ga
0.09%, Cu 0.1%, O 0.11%, C 0.02%, N 0.006%,
The analytical value of the balance Fe was obtained. After charging the raw material coarse powder 100kg to the jet mill, the inner jet mill was replaced with N ₂ gas, substantially 0% of oxygen concentration in the N ₂ gas and (0.002vol% oxygen analyzer value) did. Then, crushing pressure 8.0 kg / cm ² ,
The raw material coarse powder was pulverized under the condition of a supply rate of 12 kg / hour. The average particle size of the fine powder was 3.8 μm. A container filled with mineral oil (trade name Idemitsu Super Sol PA-30, manufactured by Idemitsu Kosan Co., Ltd.) was directly installed at the fine powder recovery port of the jet mill, and the fine powder was directly recovered into the mineral oil in a N ₂ gas atmosphere. The raw material after recovery was made into a raw material slurry in which the fine powder was 77% by weight by adjusting the amount of mineral oil. This raw material slurry is placed in the mold cavity.
Wet molding was performed at a molding pressure of 1.5 ton / cm ² while applying an orientation magnetic field of 10 kOe. The application direction of the orientation magnetic field is perpendicular to the molding direction. In addition, a large number of solvent discharge holes were provided in the upper punch of the die, and a 1 mm-thick cloth filter was applied to the upper punch surface during molding. The molded body is heated in a vacuum of 5.0 × 10 ^-2 torr at 200 ° C for 2 hours to remove the contained mineral oil, and then
Under conditions of 5.0 × 10 ^-4 torr, the temperature was raised to 1090 ° C at a heating rate of 15 ° C / min, held at that temperature for 3 hours and sintered, and then 900 ° C for 2 hours in Ar gas atmosphere. Heat treatment was performed at 460 ° C. for 1 hour to obtain a sintered permanent magnet of the present invention. Analysis of this magnet revealed that it had a weight percentage of Nd 22.3%, Pr 2.0%, Dy 5.5.
%, B 1.0%, Nb 0.5%, Al 0.2%, Co 2.0%, Ga 0.09
%, Cu 0.1%, O 0.14%, C 0.06%, N 0.040%, balance Fe
I got the analysis value. As shown in FIG. 5, the particle size distribution of the main phase of this magnet is 95% of the total area of the main phase crystal grains with the area of the main phase crystal grains having a grain size of 10 μm or less. The sum of the areas of the main phase crystal grains having a diameter of 13 μm or more was 3%. It can be seen from FIG. 5 that the crystal grain size range of the main phase having the largest area ratio is in the range of 5 μm or more and less than 6 μm, which is a sharp distribution. The magnetic properties, ρs, and 3 of the obtained sintered permanent magnet were measured in the same manner as in Example 1.
Table 1 shows the results of measuring the point bending strength and the temperature coefficients α and β. It can be seen from Table 1 that the magnet of the present invention retains good magnetic properties and has good temperature coefficients α, β and three-point bending strength. Further, in the corrosion resistance evaluation test conducted in the same manner as in Example 1, no abnormality was found in the Ni plating even after 2500 hours, and good corrosion resistance was exhibited.

[0025]

[Table 1]

(Example 3) Nd 20.7%, Pr by weight percentage
8.6%, Dy 1.2%, B 1.05%, Al 0.08%, Co 2.0%, Ga
0.09%, Cu 0.1%, O 0.03%, C 0.006%, N 0.004
%, The balance of Fe, 0.1-0.5 mm thick ribbon alloy was prepared by strip casting method. This ribbon-shaped alloy was heated in an Ar gas atmosphere at 900 ° C. for 3 hours. Next, using a hydrogen furnace, this ribbon-shaped alloy was allowed to occlude hydrogen at room temperature in a hydrogen gas atmosphere and naturally collapsed. Then, while the vacuum in the furnace was evacuated, the ribbon-shaped alloy was heated to 550 ° C., and was held at that temperature for 1 hour for dehydrogenation treatment. The collapsed alloy was mechanically crushed in a nitrogen gas atmosphere to obtain a raw material powder of 32 mesh under. When this raw material powder was analyzed, Nd 20.7%, Pr 8.6%, Dy 1.5%, B
1.05%, Al 0.08%, Co 2.0%, Ga 0.09%, Cu 0.1%, O
The analytical values were 0.13%, C 0.03%, N 0.009% and balance Fe. After charging 50 kg of this raw material coarse powder into a jet mill, the inside of the jet mill was replaced with Ar gas to make the oxygen concentration in Ar gas substantially 0% (oxygen analyzer value 0.002 vol%). Next, the concentration of N ₂ gas in Ar gas was set to 0.005 vol%.
Next, the crushing pressure was 7.5 kg / cm ² , and the raw material coarse powder was supplied at a rate of 8 kg / hour. A container filled with mineral oil (trade name Idemitsu Super Sol PA-30, manufactured by Idemitsu Kosan) was directly installed at the fine powder recovery port of the jet mill, and the fine powder was directly recovered into the mineral oil in an Ar gas atmosphere. The raw material after recovery was made into a raw material slurry in which the amount of fine oil was 75% by weight by adjusting the amount of mineral oil. The average particle size of the fine powder was 4.0 μm. This raw material slurry was wet-molded at a molding pressure of 0.6 ton / cm ² while applying an alignment magnetic field of 13 kOe in the mold cavity. The application direction of the orientation magnetic field is perpendicular to the molding direction. In addition, a large number of solvent discharge holes are provided on the upper punch of the mold, and 1 mm is used for molding.
A cloth filter having a thickness of 3 was applied to the upper punch surface and used. The compact is heated in a vacuum of 6.0 × 10 ^-2 torr at 180 ° C for 4 hours to remove the contained mineral oil, and then 1070 at a heating rate of 15 ° C / min under the conditions of 3.0 × 10 ^-4 torr. The temperature was raised to ℃, the temperature was maintained for 2 hours to sinter, and this sintered body was subjected to a heat treatment at 900 ° C. × 2 hours and 510 ° C. × 1 hour once in an Ar gas atmosphere. A sintered permanent magnet was obtained. When the composition of this sintered magnet was analyzed, it was found that the weight percentage was Nd 20.7%, Pr 8.6
%, Dy 1.2%, B 1.05%, Al 0.08%, Co 2.0%, Ga 0.
09%, Cu 0.1%, O 0.18%, C 0.07%, N 0.075%, balance Fe
I got the analysis value. In the obtained sintered magnet, the total area of the main phase crystal grains having a crystal grain size of 10 μm or less is 90% of the total area of the main phase crystal grains of the main phase crystal grains having a crystal grain size of 13 μm or more. The sum of the areas was 5%. Next, regarding the obtained sintered magnet, magnetic properties, ρs, 3
Table 1 shows the results of measuring the point bending strength and the temperature coefficients α and β. It can be seen from Table 1 that the magnet of the present invention has good magnetic properties and also has good temperature coefficients α, β and three-point bending strength. In addition, as a result of a corrosion resistance test performed on the obtained sintered magnet in the same manner as in Example 1, no abnormality was found in the Ni plating even after 2500 hours, and good corrosion resistance was exhibited. .

(Example 4) Nd 22.0%, Pr by weight percentage
5.0%, Dy 1.5%, B 1.1%, Al 1.0%, Co 2.5%, O
A strip-shaped alloy having a composition of 0.02%, C 0.005%, N 0.005% and the balance Fe and a thickness of 0.1 to 0.4 mm was prepared by a strip casting method. This ribbon-shaped alloy was heated in an Ar gas atmosphere at 1000 ° C. for 2 hours. The ribbon-shaped alloy after the heat treatment was mechanically crushed in a nitrogen gas atmosphere to obtain a raw material coarse powder of 32 mesh under. When this raw material powder was analyzed, Nd 22.0%, Pr 5.0%, Dy 1.5%, B 1.1
%, Al 1.0%, Co 2.5%, O 0.14%, C 0.01%, N 0.00
The analytical values were 9% and the balance Fe. After charging the raw material coarse powder 50kg in a jet mill, the inner jet mill was replaced with N ₂ gas, substantially 0% of oxygen concentration in the N ₂ gas and (0.002vol% oxygen analyzer value) did. Then, crushing pressure 7.0 kg / c
Jet milling was performed under the conditions of m ² and a raw material coarse powder supply rate of 10 kg / hour. The average particle size of the fine powder was 4.2 μm. A container filled with mineral oil (trade name Idemitsu Super Sol PA-30, manufactured by Idemitsu Kosan) was installed directly at the fine powder recovery port of the jet mill, and N ₂
Fine powder was recovered directly in mineral oil in a gas atmosphere. The raw material after recovery has a fine powder of 78% by adjusting the amount of mineral oil.
It was a raw material slurry of wt%. This raw material slurry was applied in the mold cavity while applying an orientation magnetic field of 11 kOe to 0.5 to
Wet molding was performed at a molding pressure of n / cm ² . The application direction of the orientation magnetic field is perpendicular to the molding direction. A large number of solvent discharge holes were provided in the upper punch of the die, and a 1 mm thick cloth filter was applied to the upper punch surface during molding. Molded body is 5.0
The contained mineral oil is removed by heating at 200 ° C for 2 hours in a vacuum of × 10 ^-2 torr, and then heated to 1080 ° C at a heating rate of 15 ° C / min under the condition of 2.0 × 10 ^-4 torr. , And kept at that temperature for 3 hours for sintering. This sintered body was heat-treated once at 900 ° C. × 2 hours and 600 ° C. × 1 hour each in an Ar gas atmosphere to obtain a sintered permanent magnet of the present invention. Analysis of the composition of this sintered magnet showed that it had a weight percentage of Nd 22.0%, Pr 5.0%, Dy 1.5%, B
1.1%, Al 1.0%, Co 2.5%, O 0.17%, C 0.07%, N
The analytical values were 0.060% and the balance Fe. Of this sintered magnet,
The sum of the areas of the main phase crystal grains having a crystal grain size of 10 μm or less was 88%, and the sum of the areas of the main phase crystal grains having a crystal grain size of 13 μm or more was 7% with respect to the total area of the main phase crystal grains. Next, regarding the obtained sintered magnet, magnetic properties, ρ were obtained in the same manner as in Example 1.
Table 1 shows the results of measuring s, three-point bending strength, and temperature coefficients α and β. It can be seen from Table 1 that the magnet of the present invention has good magnetic properties and also has good temperature coefficients α, β and three-point bending strength. In addition, as a result of the corrosion resistance test performed in the same manner as in Example 1, no abnormality was found in the Ni plating until 2000 hours had elapsed.

(Embodiment 5) With a magnetic field of 10 kOe applied in the cavity of a die of a pressing machine provided with a coil for orientation magnetic field and a pole piece so that the direction of the orientation magnetic field is perpendicular to the compression direction, Via the raw material inlet of the mold,
The raw material slurry of Example 1 was pressure-injected at a pressure of 10 kgf / cm ² , and after the injection, the material was molded under a pressure of 1 ton / cm ² while maintaining the applied magnetic field to obtain a molded body. A sintered magnet of the present invention was obtained in the same manner as in 1. When the composition of this sintered magnet was analyzed, it was found that the weight percentage was Nd 27.0%, Pr 0.5%, Dy
1.5%, B 1.05%, Nb 0.35%, Al 0.08%, Co 2.5%, G
a 0.09%, Cu 0.08%, 0.14%, C 0.06%, N 0.061%,
The analytical value of the balance Fe was obtained. In this sintered magnet, the total area of the main phase crystal grains with a grain size of 10 μm or less is 94%, and the total area of the main phase crystal grains with a grain size of 13 μm or more is It was 4%. Next, the magnetic properties, ρs, three-point bending strength, and temperature coefficients α and β of the obtained sintered magnet were measured in the same manner as in Example 1 and the results are shown in Table 1.
Shown in. It can be seen from Table 1 that the magnet of the present invention has good magnetic properties and also has good temperature coefficients α, β and three-point bending strength. In particular, by pressure-filling the slurry in the orientation magnetic field, so-called transverse magnetic field molding (BH)
R-Fe with max ≧ 50 MGOe and iHc ≧ 13 kOe, and improved bending strength and temperature coefficient (α, β)
-A B-type sintered permanent magnet can be obtained. Further, when a corrosion resistance test was conducted in the same manner as in Example 1, it showed the same corrosion resistance as in Example 1.

(Embodiment 6) With a magnetic field of 10 kOe applied in the cavity of a die of a pressing machine provided with a coil for orientation magnetic field and a pole piece so that the direction of orientation magnetic field is parallel to the compression direction, Via the raw material inlet of the mold,
The raw material slurry of Example 1 was pressure-injected at a pressure of 10 kgf / cm ² , and after the injection, the material was molded under a pressure of 1 ton / cm ² while maintaining the applied magnetic field to obtain a molded body. A sintered magnet of the present invention was obtained in the same manner as in 1. When the composition of this sintered magnet was analyzed, it was found that the weight percentage was Nd 27.0%, Pr 0.5%, Dy
1.5%, B 1.05%, Nb 0.35%, Al 0.08%, Co 2.5%, G
a 0.09%, Cu 0.08%, O 0.15%, C 0.06%, N 0.051
%, Balance Fe was obtained. In this sintered magnet, the total area of the main phase crystal grains with a grain size of 10 μm or less is 93% of the total area of the main phase crystal grains, and the total area of the main phase grains with a grain size of 13 μm or more is It was 4%. Next, regarding the obtained sintered magnet, magnetic properties, ρs, 3
Table 1 shows the results of measuring the point bending strength and the temperature coefficients α and β. It can be seen from Table 1 that the magnet of the present invention has good magnetic properties and also has good temperature coefficients α, β and three-point bending strength. In particular, by filling the slurry under pressure in the orientation magnetic field, so-called longitudinal magnetic field molding is possible.
(BH) max ≧ 45MGOe and iHc ≧ 13kOe can be realized, and bending strength and temperature coefficient (α, β) are improved.
An R-Fe-B system sintered permanent magnet is obtained. Further, when a corrosion resistance test was conducted in the same manner as in Example 1, it showed the same corrosion resistance as in Example 1.

(Comparative Example 1) The ribbon-shaped alloy produced in Example 1 was directly placed in a hydrogen furnace without heat treatment and allowed to occlude hydrogen in a hydrogen gas atmosphere at room temperature to spontaneously collapse. Then, dehydrogenation treatment and mechanical crushing were performed under the same conditions as in Example 1 to obtain a raw material coarse powder of 32 mesh under. Analysis of this raw material coarse powder showed that the weight percentage was Nd 27.0%, Pr 0.5%, D
y 1.5%, B 1.05%, Nb 0.35%, Al 0.08%, Co 2.5%, G
a 0.09%, Cu 0.08%, O 0.10%, C 0.02%, N 0.007
%, Balance Fe was obtained. This raw material coarse powder was finely pulverized under the same conditions as in Example 1, and the average particle size of the fine powder was 4.4 μm, which was coarser than that in Example 1. Subsequent steps such as fine powder collection, raw material slurry preparation, wet molding, demineralized oil and sintering, and heat treatment were also performed under the same conditions as in Example 1. When the composition of the obtained sintered magnet was analyzed,
Nd 27.0%, Pr 0.5%, Dy 1.5%, B 1.05 by weight percentage
%, Nb 0.35%, Al 0.08%, Co 2.5%, Ga 0.09%, Cu
The analytical values were 0.08%, O 0.14%, C 0.06%, N 0.045% and balance Fe. In this sintered magnet, the sum of the areas of the main phase crystal grains with a grain size of 10 μm or less to the total area of the main phase grains is 78%, and the sum of the areas of the main phase grains with a grain size of 13 μm or more is It was 12%. Magnetic properties of the sintered magnet of this comparative example, ρ
s, three-point bending strength, and temperature coefficients α and β of Example 1 respectively.
The results measured in the same manner as in Table 1 are shown in Table 1. From Table 1, the Br and iHc of this comparative example are slightly lower than those of the above examples,
It can be seen that the temperature coefficient β and the three-point bending strength are inferior. The corrosion resistance evaluated in the same manner as in Example 1 is 1200.
No abnormality was observed in the Ni plating until the time elapsed, but a small amount of peeling was observed in the local area of the Ni plating after the lapse of 2000 hours.

(Comparative Example 2) An R-Fe-B alloy ingot having the same composition as in Example 2 was produced. The compositional analysis value of this alloy is Nd 22.3%, Pr 2.0%, Dy 5.5 by weight percentage.
%, B 1.0%, Nb 0.5%, Al 0.2%, Co 2.0%, Ga 0.09
%, Cu 0.1%, O 0.01%, C 0.004%, N 0.002%, balance F
It was e. Precipitation of α-Fe was found in the structure of the alloy, and in order to eliminate it, the alloy ingot was subjected to liquefaction treatment at 1100 ° C for 6 hours in an argon gas atmosphere. Next, the alloy ingot was put into a hydrogen furnace and allowed to occlude hydrogen at room temperature to spontaneously collapse. The alloy after natural disintegration was subjected to dehydrogenation treatment and mechanical crushing under the same conditions as in Example 2 to obtain a raw material coarse powder of 32 mesh under. When this raw material coarse powder was analyzed, Nd 22.3%, Pr 2.0%, Dy 5.5%, B
1.0%, Nb 0.5%, Al 0.2%, Co 2.0%, Ga 0.09%, Cu
The analytical values were 0.1%, O 0.10%, C 0.02%, N 0.005% and balance Fe. This raw material coarse powder was finely pulverized under the same conditions as in Example 2. The average particle size of the obtained fine powder was 4.7 μm,
It was coarse compared to the case of Example 2. Then pulverize the finely ground powder into Ar
After carrying out a stabilization treatment in which it is collected in a raw material storage container kept in an atmosphere and stored for 48 hours, only this fine powder is fed into a predetermined mold, and a magnetic field is applied in the same atmosphere as in Example 2 in an Ar gas atmosphere. A molded body was manufactured by dry-molding under pressure conditions, and then, a predetermined treatment such as sintering and heat treatment was performed in the same manner as in Example 2 to obtain a sintered magnet. When the composition of this sintered magnet was analyzed, it was found that the weight percentage was Nd 22.3%, Pr 2.0
%, Dy 5.5%, B 1.0%, Nb 0.5%, Al 0.2%, Co 2.
0%, Ga 0.09%, Cu 0.1%, O 0.38%, C 0.06%, N 0.
The analytical values of 030% and balance Fe were obtained. As shown in FIG. 6, the relationship between the particle size distribution of main phase crystal grains and the area ratio of this sintered magnet is as shown in FIG. The sum was 61%, and the sum of the areas of the main phase crystal grains having a grain size of 13 μm or more was 22%. Compared with FIG. 5, it can be seen that in FIG. 6, the area ratio of the main phase crystal grains of 13 μm or more is large. The magnetic characteristics of the sintered magnet of this comparative example,
Table 1 shows the results obtained by measuring ρs, three-point bending strength, and temperature coefficients α and β in the same manner as in Example 1. From Table 1,
It can be seen that the iHc, the temperature coefficients α, β, and the three-point bending strength of this comparative example are inferior to those of Example 2.
Further, the corrosion resistance evaluated in the same manner as in Example 1 showed that no abnormality was found in the Ni plating until 1000 hours passed.
Abnormality was found in the Ni-plated area at the time point of 00 hours.

[0032]

As described above, according to the present invention, the R-Fe-B system sintered permanent type having high magnetic properties and improved bending strength and temperature coefficient (α, β) is obtained. A magnet can be provided.

[Brief description of drawings]

[Fig. 1] The total area of the main phase is 96% of the total area of the main phase crystal grains with a grain size of 10 μm or less, and 1% of the total area of the main phase crystal grains with a grain size of 13 μm or more. 3 is a photograph of a metal structure of a bonded permanent magnet.

[Fig. 2] The total area of the main phase is 64% of the total area of the main phase crystal grains with a grain size of 10 µm or less, and 17% of the total area of the main phase crystal grains with a grain size of 13 µm or more. 3 is a photograph of a metal structure of a bonded permanent magnet.

FIG. 3 shows a strip-shaped alloy produced by the strip casting method.
It is a photograph of the metal structure of an As-cast cross section.

FIG. 4 shows a ribbon-shaped alloy produced by the strip casting method.
It is a metallographic photograph of the cross section of what was heat-treated at 900 ° C.

[Fig. 5] The sum of the areas of the main phase grains with a grain size of 10 µm or less is 95% and the sum of the areas of the main phase grains with a grain size of 13 µm or more is 3% with respect to the total area of the main phase grains. It is a figure which shows the main phase particle size distribution of a certain magnet of this invention.

FIG. 6 shows that the sum of the areas of the main phase grains having a grain size of 10 μm or less is 61% and the sum of the areas of the main phase grains having a grain size of 13 μm or more is 22% with respect to the total area of the main phase grains. It is a figure which shows the main phase particle size distribution of the sintered magnet of a certain comparative example.

Front Page Continuation (72) Kensuke Sasaki Kensuke Sasaki 6010 Mikajiri, Kumagaya, Saitama Hitachi Metals Co., Ltd. Production Systems Research Laboratory (56) References JP-A-4-7804 (JP, A) JP-A-9-232173 ( JP, A) JP-A-9-260122 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01F 1/08 H01F 1/053 C22C 38 B22F

Claims (5)

(57) [Claims] 1. R in weight percentage (R is one or more of rare earth elements including Y) 27.0 to 31.0%, B 0.5 to 2.0
%, O 0.25% or less, C 0.15% or less, and the balance Fe, and the total area of main phase crystal grains with a grain size of 10 μm or less is 80% or more with respect to the total area of the main phase crystal grains and The sum of the areas of the main phase crystal grains with a diameter of 13 μm or more is 10% or less, and the sintered body density is 7.
R-Fe-B characterized by being densified to 60 g / cm ³ or more
Sintered permanent magnet. 2. The R-Fe-B system sintered permanent magnet according to claim 1, wherein the content of N is 0.02 to 0.15% by weight. 3. A part of Fe by weight percentage is Nb 0.1 to 2.0.
%, Al 0.02 to 2.0%, Co 0.3 to 5.0%, Ga 0.01 to 0.5
%, Cu 0.01 to 1.0%, and one or more of them are substituted, R-F according to claim 1 or 2.
eB sintered permanent magnet. 4. The R-Fe-B according to claim 1, wherein the intrinsic coercive force iHc is 13 kOe or more.
Sintered permanent magnet. 5. The R-F according to claim 1, wherein the maximum energy product is 35 MGOe or more.
eB sintered permanent magnet.