JP2564492B2 - Manufacturing method of rare earth-Fe-B cast permanent magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention manufactures a permanent magnet of a rare earth element containing Y (hereinafter referred to as R) -Fe-B alloy cast body having excellent magnetic properties. It is about how to do it.

[Conventional technology]

R-Fe-B system permanent magnets are attracting attention as magnets having excellent magnetic properties among rare earth system permanent magnets. The structure of the R-Fe-B system permanent magnet is generally a main phase R ₂ Fe ₁₄ B intermetallic compound phase (hereinafter, referred to as R ₂ Fe ₁₄ B phase) that is a ferromagnetic phase and has a tetragonal structure. ), R-rich phase and B-ric
It consists of h phase. In the R-Fe-B system permanent magnet, the magnetic properties thereof are largely dependent on the microstructure of the R-Fe-B system permanent magnet, and the excellent magnetic properties of the R-Fe-B system alloy can be utilized. Development of a permanent magnet having a tissue morphology has been conducted.

At present, the following R-Fe-B system permanent magnets are available.

(1) A permanent magnet characterized by a sintered body produced by powder metallurgy (see, for example, JP-A-59-460008).

A permanent magnet (hereinafter referred to as a sintered magnet) characterized by this sintered body is prepared by first crushing an ingot or a coarse powder of an R—Fe—B alloy by various methods to obtain a fine powder of about several μm. The fine powder is shaped into a green compact in a magnetic field or no magnetic field. Then, the green compact is heated in a vacuum or in a non-oxidizing gas atmosphere from room temperature to a sintering temperature of 900 to 12
It is manufactured by sintering at a temperature of 00 ° C. for 30 to 120 minutes, further performing heat treatment at an appropriate temperature to increase the coercive force as needed, and then cooling. The magnetic characteristics of the above sintered magnet are BH _max = 10MGOe when it is isotropic.
In the case of anisotropy, BH _max = 30 MGOe or more.

As shown in FIG. 1, the structure of the sintered magnet is R-Fe.
-R ₂ Fe ₁₄ B phase 1 which is the main phase of B type permanent magnet, and B-rich
Phase 3 and R ₂ Fe ₁₄ B phase 1 and R-rich phase 2 existing at the grain boundary of B-rich phase 3. R ₂ Fe in Fig. 1 above
_The average crystal grain size of the 14B phase is controlled to several μm to 20 μm in order to increase the coercive force.

(2) Ribbon-quenched powder obtained by the ultra-quenching method is compressed at high temperature,
A plastically processed permanent magnet (see, for example, Japanese Patent Laid-Open No. 60-100402). A permanent magnet (hereinafter referred to as a high temperature compression magnet) characterized by a substance obtained by compressing this quenching powder is prepared by first melting R
-Fe-B type alloy is obtained by rapid solidification to obtain ribbon-shaped flakes, which are heated to a temperature of 700 ° C or higher, subjected to high temperature compression and plastic working for several minutes, and then cooled. .

The magnetic characteristics of the above high temperature compression magnet are BH when it is isotropic.
_max = 13 MGOe, BH due to anisotropy due to plastic working
_max = about 30 MGOe. The structure of the high temperature compression magnet is
The main phase is an R ₂ Fe ₁₄ B phase having an average crystal grain size of several tens nm to several 100 nm, and a fine structure in which an R-rich phase or an amorphous phase is present in the grain boundary part, ₂ Fe ₁₄ B phase is single domain grain size: 0.3
The structure is controlled to be less than μm.

[Problems to be solved by the invention]

In order for the R-Fe-B based alloy to become a permanent magnet exhibiting a high coercive force, (a) the average crystal grain size of the R ₂ Fe ₁₄ B phase, which is the main phase, is 50 μm or less, preferably single domain particles. It should be 0.3 μm or less, (b) there should be no impurities or strain that become nuclei when reverse magnetic domains are generated in the crystal grains of the main phase, and (c) the main phase R ₂ Fe ₁₄ B If the average crystal grain size of the phase is several μm to 50 μm, R-rich will be present in the grain boundary part of the R ₂ Fe ₁₄ B phase.
Phase is present and the crystal grains of the R ₂ Fe ₁₄ B phase are surrounded by the R-rich phase, and (d) the R ₂ Fe ₁₄ B phase of the magnet powder has a magnetocrystalline anisotropy. The axes of easy magnetization are aligned and magnetic anisotropy is obtained. Especially, the average crystal grain size of the R ₂ Fe ₁₄ B phase of the main phase in (a) above has a large influence on the coercive force. It is believed that.

Conventionally, in the structure of a cast body in which an R-Fe-B based alloy is simply melted and cast, or further homogenized, even if a heat treatment is performed later, the main phase R ₂ Fe ₁₄ B phase is several tens of μm or less. Due to the lack of controllability, the cast bodies did not have good magnetic properties. Therefore, a sintered magnet is used as in the conventional technique (1) or a high temperature compression magnet is used as in the conventional technique (2) to obtain the R-Fe.
-The structure of the B-based alloy was controlled.

The sintered magnet of the above-mentioned conventional technique (1) has a main phase of R ₂ Fe.
_Since it is necessary to control the average crystal grain size of the ₁₄ B phase to be several μm to 20 μm, the fine powder for sintering usually has a particle size of 3 μm or less in consideration of grain growth of the main phase in the sintering process. Must be ground to 4 μm. However, since the R-Fe-B alloy for permanent magnets becomes very active when it is made into a fine powder of 3 to 4 μm, impurities such as oxides are generated in the sintered body, and the magnetic characteristics of the sintered magnet are increased. There was a drawback that it was scattered. Still a permanent magnet, but the R ₂ Fe ₁₄ B phase preferably less 0.3μm which can be a single domain particles is a main phase, in the sintering method, oxidation during milling is intense, it can not be produced. In addition, the above-mentioned sintered magnet has a drawback that in a thin shape having a thickness of 3 mm or less, the magnetic characteristics are significantly reduced as the thickness is reduced. In order to compensate for such drawbacks, adding additional elements to the above alloy, improving the sintering process,
Processing such as coating the sintered magnet is performed, and in order to bring out the high magnetic characteristics of the sintered magnet, it is necessary to perform complicated steps and treatments.

Since the high temperature compression magnet of the above-mentioned conventional technique (2) becomes a permanent magnet only after high temperature compression and plastic working of the quenched powder,
Applications were limited in terms of the degree of freedom in magnet shape and yield. Further, since the R ₂ Fe ₁₄ B phase, which is the main phase of the microstructure due to high temperature compression and plastic working, causes grain growth and reduces the coercive force, the above high temperature compression step is very short, which is only a few minutes. It has to be performed in a long time, and in order to obtain a permanent magnet with high magnetic characteristics, the manufacturing process has to be complicated.

That is, R- of the above-mentioned conventional techniques (1) and (2)
Since all the Fe-B system permanent magnets are powders of the R-Fe-B system magnet alloy once and are sintered to manufacture the R-Fe-B system permanent magnet, the R-Fe- system permanent magnets are used. There is a problem that it is difficult to handle the B-based alloy powder, and various attention must be paid to the sintering method, and the manufacturing process must be complicated.

[Means for solving problems]

Therefore, the inventors of the present invention can easily provide excellent magnetic properties if it is possible to impart excellent magnetic properties to a cast body of an R—Fe—B alloy, which is said to not obtain excellent magnetic properties. Based on the idea that an R-Fe-B system permanent magnet having characteristics can be manufactured, as a result of research to obtain an R-Fe-B system cast permanent magnet having excellent magnetic characteristics, R And a rare earth-Fe-B alloy cast body containing Fe and B as main components are heated to a temperature of 700 to 1000 ° C in a hydrogen-free vacuum or an inert gas atmosphere, and then in a hydrogen gas atmosphere. At temperature: 700-10
Hold the temperature at 00 ° C to occlude hydrogen in the above-mentioned cast body, and subsequently, at a temperature of 700 to 1000 ° C, hydrogen gas pressure: 1 × 10 ^-1 Torr or less or hydrogen gas partial pressure: 1 × 10 ^-1 Torr or less After dehydrogenation in a non-oxidizing atmosphere and then cooling, the rare earth-Fe-B type cast body having a recrystallized texture mainly composed of R ₂ Fe ₁₄ B phase with an average recrystallized grain size: 0.05 to 50 μm It has been found that a permanent magnet can be obtained and that the rare earth-Fe-B system cast permanent magnet has excellent magnetic properties.

The present invention has been made on the basis of such findings, in which a cast body of an R-Fe-B based alloy containing R, Fe and B as main components is produced in a hydrogen-free vacuum or an inert gas atmosphere. Temperature: Raise the temperature to 700-1000 ℃, and then in the hydrogen gas atmosphere, temperature: 700-1000
Hold the temperature at 00 ° C to occlude hydrogen in the above-mentioned cast body, and subsequently, at a temperature of 700 to 1000 ° C, hydrogen gas pressure: 1 × 10 ^-1 Torr or less or hydrogen gas partial pressure: 1 × 10 ^-1 Torr or less It is characterized by the method for producing an R-Fe-B based cast permanent magnet, which comprises dehydrogenation in a non-oxidizing atmosphere and then cooling.

The recrystallization texture formed by the method for manufacturing the R-Fe-B system cast permanent magnet will be described with reference to FIG.

FIG. 2 (a) is a schematic view of the structure of a cast body obtained by casting an R-Fe-B based magnet alloy. In FIG. 2 (a), 1 is the R ₂ Fe ₁₄ B phase and 2 is the R-rich phase. R-ric
The h phase 2 exists mainly at the grain boundary part of the R ₂ Fe ₁₄ B phase 1 which is the main phase. The cast body shown in FIG.
When treated by the method for producing a —Fe—B system cast permanent magnet, as shown in FIG. 2 (b), the R ₂ Fe ₁₄ B phase is regenerated in the grains of the R ₂ Fe ₁₄ B phase 1 or at the grain boundary part. Crystals 1'are generated and grow to form a texture of recrystallized 1'of the R ₂ Fe ₁₄ B phase as shown in FIG. 2 (c).

FIG. 2 (b) is a schematic diagram of the structure of the cast body at the time when the recrystallization 1 ′ of the R ₂ Fe ₁₄ B phase started to occur after the treatment of the cast body shown in FIG. 2 (a). FIG. 2C is a schematic diagram showing the structure of the cast body after the treatment of the cast body shown in FIG. 2A is completed.

Here, in the R-Fe-B system alloy shown in FIG.
_{R 2 Fe 14 R 2 Fe 14} B as shown from B-phase 1 in FIG. 2 (b)
Even if the recrystallized phase 1'of the phase is generated and grown to form a texture composed of the recrystallized phase 1'of the R ₂ Fe ₁₄ B phase as shown in FIG. (B) and (c)
The recrystallized 1'of the R ₂ Fe ₁₄ B phase formed in Fig. ₂ does not have a completely random crystal orientation in the region of the individual R ₂ Fe ₁₄ B phase 1 in Fig. 2 (a), but a constant crystal orientation. It is an organization with the orientation of.

On the other hand, the R-rich phase is as shown in Fig. 2 (b).
Although it is not clear at the beginning of recrystallization of the R ₂ Fe ₁₄ B phase, R ₂ F
When the recrystallized 1 ′ of the e ₁₄ B phase grows to have a texture shown in FIG. 2 (c) with an average crystal grain size of 0.05 μm or more, the recrystallized grains 1 ′ are mainly the above-mentioned grains. May be partially precipitated at the interface.

Therefore, the R-Fe-B type cast permanent magnet produced by the method of the present invention is a cast body having a recrystallized texture, while the R-Fe- of the conventional techniques (1) and (2) is used.
B-based permanent magnets have no recrystallized structure,
It is completely different in that it is a substance obtained by compressing a quenched powder.

The reason why the R-Fe-B based cast permanent magnet produced by the method of the present invention exhibits a high coercive force is that the recrystallized grain size of the main phase R ₂ Fe ₁₄ B phase is 50 μm or less, preferably a single magnetic domain. This is because the grain size is 0.05 to 3 μm, which is close to 0.3 μm that can be formed into grains, and there are no impurities or strain in the grains and grain boundaries due to the recrystallized grains. If the average recrystallized grain size of the R ₂ Fe ₁₄ B phase is smaller than 0.05 μm, it becomes difficult to magnetize and is not practical, and if it is larger than 50 μm, only a low coercive force is exhibited and R-having excellent magnetic properties is obtained. It cannot be said that it is a Fe-B cast permanent magnet.

In addition, a part of Fe of the R—Fe—B type cast permanent magnet having a recrystallized texture having the R ₂ Fe ₁₄ B phase as a main phase produced by the method of the present invention is partially replaced with Co, Ni, Cr, Mo, One of W, Ti, Zr, Hf or 2
It may be replaced with a small amount of one or more species.

The method for producing a cast permanent magnet according to the present invention is performed by heating the cast body as described above to 700 to 1000 ° C. in a vacuum or an inert gas, and maintaining the temperature at a hydrogen gas atmosphere and then a non-hydrogen gas atmosphere. The heat treatment is performed in a special two-stage atmosphere, which is completely different from the conventional method for producing a cast permanent magnet by subjecting a cast body of an R-Fe-B alloy to a normal heat treatment. The manufacturing process is much simpler than the manufacturing method of the R-Fe-B based permanent magnet manufactured from.

In the manufacturing method of the present invention, the hydrogen gas atmosphere also includes a mixed gas atmosphere of hydrogen gas and another inert gas. The hydrogen gas pressure causes hydrogen to be stored in the R ₂ Fe ₁₄ B phase,
A pressure that gives sufficient lattice strain for recrystallization is required, and at least the hydrogen gas pressure must be 0.1 Torr or higher. In a mixed gas atmosphere of hydrogen gas and other inert gas, at least hydrogen gas partial pressure of 0.1 Tor
must be greater than or equal to r.

Further, if the temperature at which hydrogen is absorbed in the R ₂ Fe ₁₄ B phase and the temperature at which dehydrogenation treatment is performed are lower than 700 ° C., the cast body becomes cracked and becomes brittle when absorbing hydrogen, and during dehydrogenation treatment. Hydrogen remains, greatly reducing the magnetic properties. Furthermore, if the temperature at which hydrogen is absorbed in the R ₂ Fe ₁₄ B phase and the temperature at which dehydrogenation is performed are higher than 1000 ° C., recrystallization is generated and grown very rapidly, and recrystallized grains can be controlled to 50 μm or less. Have difficulty.

R-Fe-B in hydrogen gas atmosphere of temperature lower than 700 ℃
When a cast body of a system magnet alloy is placed, the cast body becomes cracked and becomes brittle. Therefore, the atmosphere during the temperature rise up to 700 ° C. should be a vacuum or an inert gas atmosphere in the absence of hydrogen.

When performing dehydrogenation treatment, hydrogen gas pressure was 1 × 10 ^-1 Torr
When the dehydrogenation process is completed at a higher pressure, hydrogen remains in the cast body and the magnetic properties deteriorate.

〔Example〕

Next, the present invention will be specifically described with reference to Examples, and Comparative Examples will explain how the present invention exhibits excellent effects.

Example 1 Nd was used as a rare earth element, was melted in a high-frequency melting furnace, and was cast to produce a Nd-Fe-B system having an atomic composition of Nd.
_14.8 Fe _77.1 B _8.1 Nd-Fe-B based alloy cast body
In a gas atmosphere, the mixture was homogenized under the conditions of a temperature of 1100 ° C. and kept for 40 hours, cooled, and then cut into blocks of vertical: 8 mm × horizontal: 8 mm × height: 10 mm.

This cast block was placed in a heat treatment furnace and 1 × 10 ^-5 Torr
After evacuating to a vacuum of room temperature to 810 ℃ in that vacuum
Up to 810 ° C for 30 minutes to make the temperature of the casting block uniform at 810 ° C, and then add hydrogen gas at 1 Nl / min.
(Temperature: 20 ℃) Flow into the heat treatment furnace up to 1 atm,
While maintaining the hydrogen gas pressure in the furnace at 1 atm, hydrogen gas was allowed to flow to occlude hydrogen in the cast block, and the temperature was maintained at 810 ° C.-hydrogen gas pressure: 1 atm for 5 hours, and the cast body was maintained. After hydrogen is evenly occluded in the block, it is evacuated at a temperature of 810 ° C. for 1 hour, and the atmosphere in the heat treatment furnace is set to a vacuum of 1 × 10 ⁻⁵ Torr to dehydrogenate the cast block. It was Then Ar until 1 atm in the furnace
Nd-Fe-
A B-type cast permanent magnet was obtained.

FIG. 3 shows a heat treatment pattern for obtaining the recrystallized structure of the Nd—Fe—B system cast permanent magnet of the present invention in Example 1 above.

The cast permanent magnet obtained above was crushed to a particle size of 200 me.
When X-ray diffraction was performed using this powder as sh or less powder, the diffraction lines of the main phases Nd ₂ Fe ₁₄ B phase and Nd-rich phase were clearly observed.

The structure of the cast permanent magnet was observed with a scanning electron microscope, and the composition was analyzed with EPMA (electron probe microanalyzer).

FIG. 4 (a) is a scanning electron micrograph of the cast permanent magnet obtained in this example, and FIG. 4 (b) is the cast only subjected to the homogenization treatment in Example 1. 3 shows a scanning electron micrograph of the above.

As a result of the composition analysis by EPMA (electron probe microanalyzer), the bases of the scanning electron micrographs of FIGS. 4 (a) and 4 (b) are both Nd ₂ Fe ₁₄ B phase, and Nd-
There was a rich phase. The Nd ₂ Fe ₁₄ B phase of the cast body that has been subjected to the homogenization treatment shown in FIG. 4 (b) is several tens to several thousands μ.
m was a dendrite-like coarse crystal grain. Fourth above
It was found that the cast permanent magnet obtained in this Example 1 in FIG. (A) had the main phase Nd ₂ Fe ₁₄ B phase having recrystallized grains of about 1.5 μm. Analysis equipment)
The result of the composition analysis by the method also confirmed that the recrystallized grains were the Nd ₂ Fe ₁₄ B phase.

Therefore, from FIG. 4 (a), the cast body permanent magnet of the present invention is not a mere cast body structure, but has a large number of recrystallized grains of new Nd ₂ Fe ₁₄ B phase of about 1.5 μm. It can be seen that it has a crystal texture.

Furthermore, it can be seen that this recrystallized texture can be obtained by performing the heat treatment shown in FIG.

The results of the magnetic characteristics of the permanent magnet obtained in Example 1 are shown in Table 1.

Comparative Examples 1 and 2 The same homogenization treatment as in Example 1 above was performed: length: 8 mm
× width: 8mm × height: 10mm cast block put in a heat treatment furnace, after evacuating to a vacuum of 1 × 10 ^-5 Torr, the temperature is raised from room temperature to 810 ℃ in the vacuum, temperature: 810 ℃ After holding for 30 minutes to make the temperature of the cast block uniform at 810 ℃, Ar gas
Flow into the heat treatment furnace at a flow rate of Nl / min (20 ° C) up to 1 atm,
Ar gas was flowed while maintaining the furnace at 1 atm, and the temperature: 810 ° C-Ar gas pressure: 1 atm was maintained for 5 hours, and then exhausted at temperature: 810 ° C for 1 hour to obtain the atmosphere in the heat treatment furnace. Was set at 1 × 10 ⁻⁵ Torr vacuum. After that, Ar gas was flown into the furnace to 1 atm to rapidly cool the cast block to obtain a Nd-Fe-B type cast permanent magnet (Comparative Example 1).

In the heat treatment of Example 1, the same heat treatment as in Example 1 was performed in a vacuum of 1 × 10 ⁻⁵ Torr without using hydrogen gas to obtain a Nd—Fe—B based cast permanent magnet. (Comparative example 2).

The heat treatment patterns of Comparative Examples 1 and 2 are shown in FIGS. 3-1 and 3-2.

The structures of the cast permanent magnets obtained in Comparative Examples 1 and 2 are similar to those of the structure shown in FIG.
₂ Fe ₁₄ B phase had coarse dendrite-like grains.

The results of the magnetic properties of the cast permanent magnets obtained in Comparative Examples 1 and 2 are also shown in Table 1.

From Table 1, the cast permanent magnet of the present invention has a coercive force of 1
High as 2.5KOe and soon It can be seen that the magnetic properties are shown.

Examples 2 to 10 and Comparative Examples 3 to 5 Nd and Pr were used as rare earth elements, and the Nd-Pr-Fe-B system produced by melting and casting in an electron beam melting furnace had an atomic composition of Nd _14.6 Pr _0.3 Fe. A cast body of _78.4 B _6.7 Nd-Pr-Fe-B system alloy was cut into a block having a length of 8 mm, a width of 8 mm, and a height of 10 mm. This cast block was put into a heat treatment furnace, and after being evacuated to a vacuum of 2 × 10 ⁻⁵ Torr, the temperature was raised from room temperature to the hydrogen storage temperature in Table 2 in the vacuum, and the hydrogen storage temperature in Table 2 was increased. After keeping the temperature of the casting block uniform for 30 minutes, hydrogen gas is flown into the heat treatment furnace at a flow rate of 0.6 Nl / min (temperature: 20 ° C) until the hydrogen gas pressure becomes 500 Torr, and the inside of the furnace is heated. While maintaining the hydrogen gas pressure: 500 Torr, the hydrogen gas was decompressed and allowed to occlude hydrogen in the casting block, and the hydrogen absorption temperature in Table 2 above-hydrogen gas pressure: 500 To.
The state of rr was maintained for 2 hours to uniformly occlude hydrogen in the cast block.

Then, evacuation was performed for 1 hour at the dehydrogenation temperature shown in Table 2 above, and the atmosphere in the heat treatment furnace was set to a vacuum of 1 × 10 ⁻⁵ Torr,
The cast block was dehydrogenated. After that, Ar gas was flown into the furnace to rapidly cool the cast block to obtain an Nd-Pr-Fe-B-based cast permanent magnet. The structure of the obtained cast permanent magnet was observed, the presence or absence of a recrystallization texture was examined, and the magnetic characteristics were measured. The results are shown in Table 2.

It can be seen from Table 2 above that when the temperature is raised to 700 to 1000 ° C. in vacuum and the hydrogen absorption and dehydrogenation treatment is performed at the temperature of 700 to 1000 ° C., the cast block has recrystallization. It can be seen that it has high magnetic properties particularly in hydrogen storage and dehydrogenation treatment in the temperature range of 800 to 900 ° C.

Examples 15 to 17 and Comparative Examples 11 and 12 Nd and Dy were used as rare earth elements, and the Nd-Dy-Fe-B system prepared by melting and casting in a high-frequency melting furnace had an atomic composition of Nd-Dy-Fe-B.
A Nd _14.8 Dy _0.3 Fe _78.1 B _6.8 Nd-Dy-Fe-B alloy cast body was homogenized and cooled in an Ar gas atmosphere at a temperature of 1080 ° C for 60 hours, and then cooled. Vertical: 8 mm ×
Width: 8 mm × height: cut into 10 mm blocks. This cast block was put in a heat treatment furnace, and after it was evacuated to a vacuum of 1 × 10 ^-5 Torr, the temperature was raised from room temperature to 830 ° C. in that vacuum, and the temperature was maintained at 830 ° C. for 1 hour. Temperature 830
After homogenizing at ℃, add hydrogen gas at 0.2Nl / min (Temperature: 20
℃) flow into the heat treatment furnace up to 600 Torr, hydrogen gas is depressurized while maintaining hydrogen gas pressure in the furnace at 600 Torr to occlude hydrogen in the above cast block, temperature: 830 ℃ -hydrogen gas pressure After holding the state of: 600 Torr for 10 hours to occlude hydrogen evenly in the above cast block, exhaust the gas at a temperature of 820 ° C and set the atmosphere in the heat treatment furnace to hydrogen gas pressure: 1 x 10 ^-6 Torr (Example 15), 1x
10 ⁻³ Torr (Example 16), 1 × 10 ⁻¹ Torr (Example 17), 2
The cast block was dehydrogenated until a vacuum of × 10 ^-1 Torr (Comparative Example 11) and 1 Torr (Comparative Example 12) was achieved. Then, Ar gas was flown into the furnace until the pressure reached 1 atm and the cast block was rapidly cooled to obtain a Nd-Dy-Fe-B-based cast permanent magnet.

When the structure of the obtained cast permanent magnet was observed,
All of the cast permanent magnets obtained in Examples 15 to 17 and Comparative Examples 11 and 12 had a recrystallized structure, and their magnetic properties were measured, and the results are shown in Table 3. It was

From Table 3 above, the cast permanent magnet manufactured by the method of the present invention has a hydrogen gas pressure of 1 × when subjected to dehydrogenation treatment.
It can be seen that excellent magnetic properties are exhibited when the dehydrogenation treatment is completed at a pressure of 10 ^-1 Torr or less.

Examples 18 to 19 and Comparative Examples 13 and 14 In the above Examples 15 to 17 and Comparative Examples 11 and 12, the Nd-Dy-Fe-B-based alloy castings which have been subjected to the homogenization treatment have a vertical length of 8 mm.
× width: 8 mm × height: 10 mm, cast block cut into a heat treatment furnace and evacuated to a vacuum of 1 × 10 ^-5 Torr, then 1 atm
Ar gas is flowed in, the temperature is raised from room temperature to 830 ° C while Ar gas is flowing, the temperature of the cast block is kept uniform at 830 ° C for 1 hour, and then the Ar gas flow is stopped. Hydrogen gas at a flow rate of 0.2 Nl / min (temperature: 20 ° C) into the heat treatment furnace to replace the hydrogen gas in the furnace with 1 atm in the furnace.
While maintaining at, hydrogen gas is caused to flow into the above-mentioned cast body block to occlude hydrogen, and temperature: 830 ° C-hydrogen gas pressure: 1 at
After holding the m state for 10 hours to evenly store hydrogen in the casting block, stop the hydrogen gas flow and restart the hydrogen gas flow.
Ar gas was flown in, the inside of the furnace was replaced with Ar gas, and the furnace was maintained for 30 minutes to create an atmosphere of Ar gas of 1 atm. At this time, hydrogen gas still remained in the Ar gas atmosphere. Then the temperature: 8
At a temperature of 20 ° C., the atmosphere consisting of Ar gas and residual hydrogen gas in the heat treatment furnace was adjusted to a hydrogen gas partial pressure of 5 × 10 ⁻⁴ Torr (Example 1
8), 8 × 10 ^-2 Torr (Example 19), 2 × 10 ^-1 Torr (Comparative Example 13) and 1 Torr (Comparative Example 14) were evacuated, and the cast block was dehydrogenated. It was The hydrogen gas partial pressure was measured by gas chromatogram analysis, and the carrier gas was converted from the volume ratio of hydrogen gas using Ar. After that, Ar gas was flown into the furnace until it reached 1 atm and the cast block was rapidly cooled to obtain a Nd-Dy-Fe-B-based cast permanent magnet.

All of the cast permanent magnets thus obtained also had a recrystallized structure, and the magnetic properties of these cast permanent magnets were measured, and the results are shown in Table 4.

It can be seen from Table 4 above that when the cast permanent magnet obtained by the method of the present invention is subjected to the dehydrogenation treatment, the dehydrogenation treatment is completed at a hydrogen gas partial pressure of 1 × 10 ⁻¹ Torr or less. It can be seen that it exhibits excellent magnetic properties.

〔The invention's effect〕

As described above, R-Fe-B produced by the method of the present invention
The cast permanent magnet has excellent magnetic properties because it has a recrystallized texture with the R ₂ Fe ₁₄ B phase as the main phase, and by controlling the recrystallized grain size, the cast permanent magnet Magnetic properties, oxidation resistance, heat resistance, etc. can also be improved, and the magnetic properties can be maintained even as a thin magnet.

Further, the R-Fe-B type cast body permanent magnet manufactured by the method of the present invention is one in which the cast body block is subjected to hydrogen storage and dehydrogenation treatment without sintering the R-Fe-B type alloy powder. R-Fe- produced by sintering conventional powder from
The manufacturing process is much simpler than that of the B-based permanent magnet, and the productivity and economy are excellent.

[Brief description of drawings]

FIG. 1 is an explanatory view of the structure of a conventional sintered magnet, FIG. 2 (a) is an explanatory view of the structure of a cast body of an R—Fe—B alloy, and FIG. 2 (b) is a second view. FIG. 2 (c) is an explanatory view showing a structure in which a cast body having the structure shown in FIG. (A) is treated to generate recrystallization of the R ₂ Fe ₁₄ B phase, and FIG. 2 (c) is shown in FIG. 2 (b). Of the recrystallized texture obtained by growing the recrystallized texture of Fig. 3, Fig. 3 is the heat treatment pattern of Example 1, Fig. 3-1 is the heat treatment pattern of Comparative Example 1, and Fig. 3-2. The figure shows the heat treatment pattern of Comparative Example 2, FIG. 4 (a) is a metallographic photograph of the cast permanent magnet obtained in Example 1 by a scanning electron microscope, and FIG. 4 (b) is the image of Example 1. The metallographic photograph by the scanning electron microscope of the homogenized casting is shown. 1 ...... R ₂ Fe ₁₄ B phase, 2 ... R-rich phase, 3 .... B-rich phase, 1 '... recrystallized R ₂ Fe ₁₄ B phase.

Front Page Continuation (72) Inventor Tamotsu Ogawa 1-297 Kitabukuro-cho, Omiya City, Saitama Prefecture, Central Research Laboratory, Mitsubishi Metals Co., Ltd. (56) Reference JP-A-61-238915 (JP, A) JP-A-62-23902 ( JP, A) JP 62-198103 (JP, A)

Claims (2)

(57) [Claims] 1. A cast body of R (Fe is a rare earth element containing Y) and an R—Fe—B based alloy containing Fe and B as main components, and a vacuum or inert gas atmosphere free of hydrogen. Temperature: 700 ~ 1000 ℃ in the following, and subsequently in a hydrogen gas atmosphere, temperature: 700 ~ 1000
Hold the temperature at ℃ to occlude hydrogen in the above casting, and then continue at a temperature of 700 to 1000 ℃, hydrogen gas pressure: 1
A rare earth-Fe-B based cast permanent magnet, characterized by being dehydrogenated in a non-oxidizing atmosphere of not more than × 10 ^-1 Torr or a hydrogen gas partial pressure of not more than 1 × 10 ^-1 Torr, and then cooled. Manufacturing method. 2. A cast body of an R—Fe—B alloy containing R, Fe and B as main components is heated to 700 to 1000 ° C. in a vacuum or an inert gas atmosphere in the absence of hydrogen and held. The method for producing a rare earth-Fe-B system permanent magnet according to claim 1, wherein