JPH10135019A - Anisotropic magnetic powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rare-earth magnetic powder which is subjected to a high temperature hydrogen heat treatment and exhibits a high anisotropy. SOLUTION: A rare-earth magnetic power is made of RFeB base alloy, comprised of rare-earth elements(R) containing yttrium(Y) which are subjected to a high-temperature hydrogen heat treatment and whose anisotropy (Br/Bs when Bs is 1.6T (16kG)) is 0.70 or more, boron(B) and inevitable impurities, and iron(Fe) and RFeB base alloy containing one of gallium(Ga) and niobium(Nb). A magnetic powder exhibiting a high anisotropy is obtained by reaction of the RFeB base alloy and hydrogen at a relative reaction speed of 0.25-0.50, when the reaction speed at 83 deg.C and under pressure of hydrogen of 0.1MPa (1atm) is set to 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a rare earth element-iron-
The present invention relates to an anisotropic magnet powder made of a boron-based alloy and having high anisotropy.

[0002]

2. Description of the Related Art Conventionally, a rare-earth magnet made of an RFeB-based alloy containing a rare-earth element containing yttrium (Y) (hereinafter referred to as R), iron (Fe) and boron (B) as main components has a residual magnetic flux. Because of its excellent magnetic properties such as density and coercive force, it is widely used industrially. This rare earth magnet is disclosed in, for example, JP-A-60-257107 and JP-A-62-257107.
No. 23903 and Japanese Patent Publication No. 7-68561.

Japanese Patent Application Laid-Open No. 62-23903 discloses RF
The coercive force (iHc) is 5 kOe (398 k) by improving the dehydrogenation treatment of the high-temperature hydrogen heat treatment for performing the forward transformation and the reverse transformation of the structure of the eB-based alloy by absorbing and desorbing hydrogen.
(A / m). Here, the high-temperature hydrogen heat treatment means a heat treatment accompanied by a transformation of the structure, and is distinguished from a low-temperature hydrogen heat treatment in which only the occlusion and dehydrogenation of the hydrogen without the transformation of the structure occur.

Japanese Patent Publication No. Hei 7-68561 discloses that this high-temperature hydrogen heat treatment is improved and the RFeB alloy is
Hydrogen gas of 0 Torr (1.3 kPa) or more or 1
500 ° C. to 10 under an atmosphere of a mixed gas of hydrogen gas and an inert gas at a partial pressure of 0 Torr (13 kPa) or more.
By performing a series of high-temperature hydrogen heat treatments such as heat treatment at a temperature of 00 ° C. to absorb hydrogen in the raw material to cause forward transformation and dehydrogenation again, iHc becomes 10 kOe (7
A method for obtaining a rare-earth permanent bonded magnet having high magnetic properties of 95 kA / m) is disclosed.

[0005] Furthermore, Japanese Patent Publication No. Hei 7-68561 discloses that
Nd _12.0 Pr _1.4 Fe _80.8 temperature was increased rare earth alloy of the atomic composition of B _5.8 to 830 ° C. in 1AtmH ₂ gas, then 830 ° C. was maintained for 5 hours 10 H ₂ gas pressure during this time
To 760 Torr (1.3 kPa to 0.1 MPa), and then maintained at 830 ° C. for 1.0
The anisotropic bonded magnet was obtained by depressurizing to a degree of vacuum of × 10 ⁻⁵ Torr (1.31 × 10 ⁻³ Pa), holding for 40 minutes, and then rapidly cooling. As the bonded magnet having the most remarkable anisotropy in the embodiment, a magnetic field is applied during compression molding to bring Br from 6.1 kG (0.61 T) to 7.2 k.
G (0.72T) which is improved by about 18.2%.

[0006] Japanese Patent Publication No. Hei 4-20242 discloses that
A method is disclosed in which a rare-earth magnet is once formed by melt spinning, and then the rare-earth magnet is hot-rolled to form a structure in which the crystal directions are aligned, thereby forming a rare-earth magnet having high anisotropy.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a rare earth magnet powder that has been subjected to a high-temperature hydrogen heat treatment and has a high anisotropy,
That is, it is an object to provide a rare-earth magnet powder having a high anisotropy of Br / Bs of 0.70 or more. The method of producing a rare-earth magnet powder having a structure in which the crystal directions are aligned by hot-rolling the rare-earth magnet and having a high anisotropy has a high manufacturing cost due to the complicated operation. Further, the crystal grains of the obtained rare earth magnet powder have a flat characteristic.

On the other hand, the crystal grains are refined and reduced by high-temperature hydrogen heat treatment for performing a normal transformation of the structure by absorbing hydrogen and a reverse transformation of the structure by dehydrogenation, which is a feature of the rare earth magnet as a hydrogen storage alloy. There is a method of obtaining a rare-earth magnet powder by a high-temperature hydrogen heat treatment that enhances magnetic properties such as residual magnetic flux density and coercive force. The rare-earth magnet powder obtained by the high-temperature hydrogen heat treatment has an advantage that the operation is relatively simple and the production cost is low, but there is a problem that a rare-earth magnet powder having excellent magnetic properties cannot be obtained. In particular, it is extremely difficult to provide anisotropy.

In the process of high-temperature hydrogen heat treatment of a rare-earth magnet, as disclosed in the above-mentioned Japanese Patent Publication No. 7-68561, when a rare-earth alloy having a composition of Nd _12.0 Pr _1.4 Fe _80.8 B _{5.8 is} subjected to high-temperature hydrogen heat treatment, Anisotropy has been reported in which Br is increased by about 18.2% from 6.1 kG (0.61 T) to 7.2 kG (0.72 T) by applying a magnetic field during molding. One of the inventors of Japanese Patent Publication No. 7-68161 is disclosed in J. Pat. Alloys and Co
mounds 231 (1995) 51.
Hydrogen treatment of the ternary rare earth alloy of B only gives an isotropic magnet powder, but this Fe is replaced by Co and Z
NdFeCo to which elements such as r, Ga, Nb, and Hf are added
It is described that when hydrogen treatment is performed on B, anisotropy is developed.

The present inventor has studied the hydrogen treatment of rare earth magnets in detail, and as a result of repeated experiments, it has been thought that NdF, which was conventionally obtained only by isotropic magnet powder by high-temperature hydrogen heat treatment.
It has been discovered that the ternary magnet powder of eB becomes a magnet powder having extremely high anisotropy by high-temperature hydrogen heat treatment. Explaining other magnetic characteristics, Nd by conventional high-temperature hydrogen heat treatment
Br of ternary magnet powder of FeB is 0.8T (8.0k).
G) was considered to be of the order, but Br was changed from 1.2 to 1.2 without changing the composition of the ternary magnet powder of NdFeB.
It has been discovered and confirmed that it can be increased to 1.5 T (12 to 15 kG).

The present inventors have found that the high anisotropy of the ternary alloy of NdFeB by the high-temperature hydrogen heat treatment is based on NdFB.
When the rare earth alloy of eB is made to absorb hydrogen and react with hydrogen, and the structure of the rare earth alloy is forward transformed, Nd ₂ Fe ₁₄
Crystal orientation of B ₁ is stored is transferred to a number of fine Fe ₂ B, which is believed to result from the forward transformation, which is the crystal orientation of transcription conserved Fe ₂ B is reproduced in the reverse transformation of the alloy structure by dehydrogenation It is believed that the magnetic powder is transferred to fine Nd ₂ Fe ₁₄ B ₁ crystals and becomes magnet powder having extremely high anisotropy. In the present invention, cobalt (Co) is not required in the composition.

The present invention has been completed based on such a view.

[0013]

The anisotropic magnet powder of the present invention is subjected to a high-temperature hydrogen heat treatment, and has an anisotropy (Br / Bs, where Bs is 1.6 T (16 kG)) of 0.70 or more. It is characterized by comprising an RFeB-based alloy including a rare earth element (hereinafter, referred to as R) containing yttrium (Y), boron (B), and unavoidable impurities, and the balance being iron (Fe). Further, another anisotropic magnet powder of the present invention is subjected to high-temperature hydrogen heat treatment, and yttrium (Br / Bs, where Bs is 1.6 T (16 kG)) having an anisotropy of 0.70 or more is used. RFeB system comprising a rare earth element (hereinafter referred to as R) containing Y), boron (B), at least one of gallium and niobium, and unavoidable impurities, and the balance being iron (Fe) It is characterized by being made of an alloy.

RFe constituting the anisotropic magnet powder of the present invention
The B-based alloy is considered to have high anisotropy because it is composed of recrystallized grains having a tetragonal crystal structure of R ₂ Fe ₁₄ B ₁ . The anisotropic magnet powder of the present invention is obtained by high-temperature hydrogen heat treatment, and has a feature that its crystal grains are close to spherical, that is, the aspect ratio of the crystal grains is small.
Specifically, the size of the crystal grain is 0.1 to 1.0
μm, the aspect ratio of almost all crystal grains is 2.0
It is as follows.

Here, the crystal grains do not mean alloy powders, but individual grains of a large number of crystal grains constituting one alloy powder. The aspect ratio is a value defined by a ratio of the longest grain size to the minimum grain size of the crystal grains (longest grain size / minimum grain size). Further, the crystal grains of the hot-rolled rare-earth magnet are flat, and the shape of the crystal grains is completely different from that of the rare-earth magnet powder subjected to the high-temperature hydrogen heat treatment.

Since a normal BH tracer cannot be used for Br of the magnet powder, the following method was adopted as a method for measuring Br in the present invention. First, 74-1
The particles having a particle size of 05 μm were classified and used. Then, molding is performed so that the demagnetizing field becomes 0.2, and 4578 after orientation in the magnetic field.
Magnetize at kA / m (45 KOe), measure with VSM and B
r was determined.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The RFeB-based alloy constituting the anisotropic magnet powder of the present invention has R of 12 to 15 at% and 5.5
８8 at% of B and unavoidable impurities, the balance being F
e. If R exceeds 15 at%, Br decreases, and if it does not reach 12 at%, primary crystal α-Fe remains. On the other hand, when B exceeds 8 at%, Br decreases, and when it does not reach 5.5 at%, an Nd ₂ Fe ₁₇ phase or the like precipitates. R is Y, La, Ce, Pr, Nd, Sm,
One or more selected from Gd, Td, Dy, Ho, Er, Tm and Lu can be used. Among them, it is preferable to use Nd for reasons of cost and magnetic characteristics.

RFeB: 0.01 to 1.0 at% of Ga
The coercive force of the magnet powder obtained by blending is improved. It is considered that this Ga facilitates smoothing of the crystal grain boundaries and increases iHc. Further, Nb is set to 0.
The anisotropy can be further increased by blending the content of 01 to 0.6 at%. It is considered that this Nb improves the Br by ensuring the transfer of Fe ₂ B.

The anisotropic magnet powder of the present invention has an anisotropy (Br / Bs, where Bs is 1.6 T (16 kG)) of 0.70 or more. As other magnetic characteristics, Br is 1.2 to 1.5 T (12 to 15 kG), and iHe is 636.
１２1272 kA / m (8.0 to 16 kOe), (BH)
max is 238 to 358 kJ / m ³ (30 to 45 MGO
e) having the characteristic of The anisotropic magnet powder of the present invention comprises RFe
Hydrogen is absorbed into the B-based alloy to reduce the reaction between the hydrogen and the alloy.
It can be produced by proceeding within a relative reaction rate range of 25 to 0.50 to cause a forward transformation of the structure and then proceeding with a dehydrogenation reaction to cause a reverse transformation of the structure. The method of preparing the raw materials used in this production is not particularly limited, but high-purity rare earth, iron, and boron are used, and a predetermined amount thereof is mixed and melted in a melting furnace or the like, which is cast to form an alloy ingot. It can be manufactured and used as a raw material. Further, the ingot may be pulverized by pulverization and used as a raw material.

At this time, depending on the method of preparing the raw material, there may be a deviation in the composition distribution in the raw material. Such a deviation in the composition distribution is not preferable. Therefore, it is desirable to homogenize these raw materials. This homogenization can reduce the occurrence of bias in the composition distribution. Hydrogen is absorbed in the RFeB-based alloy of the present invention, and the reaction rate V between the alloy and hydrogen is V = V ₀ · √ (PH ₂ / P) · exp (−Ea / RT) (where V _{O is a} frequency factor, PH ₂ : hydrogen gas pressure (P
a), P _O : dissociation pressure (Pa), Ea: activation energy (kJ / mol), R: gas constant (J / molK),
T: temperature (K). ). Since this reaction rate is considered to be proportional to the transformation rate of the structure, the transformation rate of the structure was evaluated based on this reaction rate.

That is, the reaction rate of the forward transformation reaction of the structure is the reference reaction rate at which the reaction rate _Vb when the reaction temperature is 830 ° C. and the hydrogen gas pressure is 0.1 MPa is _Vb = 1. It was defined as the relative reaction rate _Vr based on the rate. V
_r can be represented by the following equation. V _r = (1 / 0.5
76) · √PH ₂ · exp (-Ea / RT) The reverse transformation of the structure is 830 ° C and the hydrogen gas pressure is 0.0
01 MPa (0.01 atm) was set as the reference reaction rate.
The relative reaction rate of the reverse transformation reaction can be similarly determined.

The activation energy Ea is 195 to 200 kJ / mol depending on the composition as shown in FIG. The activation energy Ea is determined by referring to the heat of formation of Nd and H ₂ to form NdH ₂ . Specifically, when the relative reaction rate of the forward transformation reaction is defined by the reaction temperature and the hydrogen gas pressure, it is shown in FIG. 2 showing the temperature dependence of the relative reaction rate and FIG. 3 showing the pressure dependence of the relative reaction rate.

The relative reaction rate of the forward transformation reaction is 0.25 to
In order to keep the reaction rate within the range of 0.50, the reaction temperature is in the range of 780 to 840 ° C, and the hydrogen pressure is in the range of 0.01 to 0.
The range of 06 MPa (0.1 to 0.6 atm) is good. It should be noted that the reaction temperature mentioned here is a temperature at which the RFeB-based alloy absorbs hydrogen and causes a forward transformation, and is not a control temperature of the reaction furnace.

The reaction in which the RFeB-based alloy absorbs hydrogen to cause a forward transformation is an exothermic reaction, and the start of the forward transformation causes the reaction temperature to rapidly increase. Therefore, the actual reaction temperature is significantly different from the control temperature of the reactor. It is also conceivable that the hydrogen gas pressure fluctuates greatly due to hydrogen occlusion. For example, when a mixed gas of an inert gas and a hydrogen gas is employed, hydrogen is occluded, and the hydrogen gas concentration around the RFeB-based alloy that causes a forward transformation may be greatly reduced.
In order to obtain highly anisotropic magnet powder, strict control of the reaction temperature and control of the hydrogen gas pressure are required.

The relative reaction rate of the forward transformation is 0.25 to 0.5
When the reaction rate is outside the range of 0, the anisotropy becomes small. It should be noted that magnet powder made of an RFeB-based alloy is inherently anisotropic, and it is also extremely difficult to make it completely isotropic. Here, when the anisotropy is defined as anisotropic Br / Bs (Bs = 1.6T (Bs = 16 kG)), those having a value of 0.5 or less are fully isotropic,
Those exceeding 5 and less than 0.70 are defined as isotropic, and those exceeding 0.70 are defined as anisotropic.

The relative reaction rate of the forward transformation is 0.25 to 0.5
Br / Bs (Bs = 1.6T (B
s = 16 kG)) to obtain an anisotropic magnet powder of 0.70 or more. Due to the forward transformation reaction, as explained above, N
It is considered that when a rare earth alloy of dFeB is subjected to hydrogen transformation and normal transformation, the crystal orientation of Nd ₂ Fe ₁₄ B ₁ is accurately transferred by a large number of fine Fe ₂ B, which is considered to be caused by the normal transformation. ing. When the relative reaction rate of the forward transformation is out of the reaction rate range of 0.25 to 0.50, Fe ₂ B
Transfer is not sufficient and the anisotropy is low. The present inventor believes that if the transfer to Fe ₂ B is not sufficient at present, it is impossible to increase the anisotropy in a later step.

It is impossible with a normal furnace to control the relative reaction rate of the forward transformation, which accelerates with the reaction, within the range of 0.25 to 0.50. For this reason, as a new heat treatment furnace, the present inventors have filed Japanese Patent Application No. 8-20.
A furnace having an endothermic means for canceling the heat generated during the reaction described in the specification of No. 6231 was developed and used. This heat absorbing means arranges a hydrogen storage alloy in a tube, puts the tube into a furnace, reduces the hydrogen gas pressure in the tube in reverse to the heat generated by the reaction, advances the dehydrogenation reaction, absorbs heat, and generates heat by the reaction. Absorb and offset. Thereby, the control temperature of the furnace and the reaction temperature can be made substantially equal.

This forward transformation reaction ideally ends in about 30 minutes, but industrially, the reaction time depends on the throughput.
After completion of the forward transformation, at least 1
The coercive force of the magnetic powder obtained by continuing the heat treatment for a long time is improved. This is thought to be related to the relaxation of the internal strain caused by the forward transformation. It is considered that if the internal strain remains, the structure becomes uneven after the reverse transformation, and the coercive force decreases.

Thereafter, the absorbed hydrogen is dehydrogenated to cause reverse transformation. This reverse transformation is to transfer the crystal orientation of Fe ₂ B to the crystal orientation of Nd ₂ Fe ₁₄ B ₁ which produces the crystal orientation. In order to transfer the orientation of Fe ₂ B at the time of this reverse transformation, it is preferable to cause the orientation to occur within a relative reaction rate range of 0.1 to 0.4. Specifically, this reverse transformation is achieved by maintaining the hydrogen gas pressure at 1/10 to 1/100 of the hydrogen gas pressure of the forward transformation. Note that the reverse transformation is an endothermic reaction opposite to the normal transformation, and the reaction temperature decreases at an accelerated rate due to the start of the reverse transformation. Therefore, in order to keep the actual reaction temperature in the range of 780 to 840 ° C., a furnace having the same capability as in the forward transformation is required.

This reverse transformation theoretically ends within 10 minutes. Industrially, it depends on the throughput. After the completion of the reverse transformation, it is preferable to maintain the temperature of the reverse transformation for at least 25 minutes to remove hydrogen contained in the rare-earth magnet powder having the generated Nd ₂ Fe ₁₄ B ₁ crystal. This improves the coercive force. If the dissociated hydrogen remains in the alloy, the coercive force will be significantly impaired. After cooling, the anisotropic magnet of the present invention is obtained. Cooling is at least 5 ° C / min.
It is desirable to carry out at a cooling rate of

When an ingot-like raw material is used, the obtained ingot-like rare-earth permanent magnet can be easily ground in a mortar or the like. Also, when using powdery raw materials,
Although it may be solidified due to aggregation or the like, it can be easily pulverized in a mortar or the like. The rare-earth permanent bonded magnet is manufactured using the obtained rare-earth permanent magnet powder and a resin serving as a binder for the magnet powder. At this time, a thermosetting resin such as an epoxy resin can be used as the resin,
Under a predetermined magnetic field for magnetization, a mixture obtained by mixing the resin and the magnet powder is molded by pressure molding or the like, and then heat-treated to thermally cure the resin, thereby forming an anisotropic rare earth element. A permanent bonded magnet can be formed.

[0032]

The anisotropic magnet powder of the present invention has a Br / Bs
(Here, Bs is 1.6 T (16 kG)), which is 0.70 or more and has an extremely large anisotropy. The residual magnetic flux density and the coercive force were 1.2 T (12 kG) and 636 kA, respectively.
/ M (8 kOe) or more. The anisotropic bonded magnet using these magnet powders is 135 kJ /
It has a high (BH) max of m ³ (17MGOe) or more.

In the method for producing anisotropic magnet powder according to the present invention, the relative reaction rate of the normal transformation reaction in the high-temperature hydrogen heat treatment is set to a predetermined rate. Thereby, a rare-earth magnet powder having large anisotropy can be easily obtained.

[0034]

The present invention will be specifically described below with reference to examples. (Example 1) Nd: 12.5 at%, B: 6.2 at%
%, The alloy consisting of the balance Fe was melted by button arc melting, homogenization was completed at 1140 ° C., and then hydrogen treatment was performed under the conditions shown in Table 1.

More specifically, the sample was placed in a quartz tube as small as about 15 g, which was extremely small, and connected to a gas pressure controller via a conduit so that the hydrogen gas pressure in the quartz tube could be controlled. An infrared heating furnace was used as the heating furnace. The temperature was measured using a thermocouple, the temperature of the sample and the temperature of the atmosphere were measured, and the furnace was controlled based on these temperatures. The hydrogen gas pressure shown in Table 1 was introduced into the quartz tube, and heated in that state to reach the reaction temperature in about 60 minutes. Then, when the temperature of the sample exceeds the temperature of the atmosphere, the heating is stopped immediately, the temperature of the atmosphere is lowered by cooling by heat radiation, and the heat generated by the reaction is absorbed.
The sample temperature was kept within the target reaction temperature + 5 ° C. Since the sample amount was as small as 15 g and the infrared furnace was used, the ambient temperature in the quartz tube could be controlled relatively easily.

Thereafter, at 820 ° C. and a hydrogen gas pressure of 0.02 MPa
Heat treatment was performed at a (0.2 atm) for 3 hours. Thereafter, the hydrogen gas pressure in the quartz tube was released to achieve a reverse transformation relative velocity of 0.26, thereby achieving dehydrogenation, and the reverse transformation reaction was advanced. In the reverse transformation reaction by this dehydrogenation, the control method is such that the hydrogen gas pressure is delicately controlled, and when the temperature starts to decrease due to the endothermic reaction, the reduction of the hydrogen gas pressure is stopped, and when the temperature returns to the predetermined temperature, the pressure is restarted again. And the target temperature-
The temperature is controlled within the range of 5 ° C, and the hydrogen gas pressure when storing hydrogen gas is 1
0.0001 MPa (0.001 at or less)
m).

From the start of the reverse transformation reaction by this dehydrogenation, 3
The heat treatment at a predetermined temperature was continued until 0 minutes later. Thereafter, the system was cooled and the hydrogen treatment was completed. This produced a rare earth magnet powder. The residual magnetic flux density of the obtained rare earth magnet powder was measured, and the anisotropic ratio was determined. Table 1 shows the relative transformation rate of the forward transformation, the processing temperature, and the hydrogen gas pressure during hydrogen storage together with the residual magnetic flux density and the anisotropic ratio. The aspect ratio was determined as an average value of 25 samples by measuring the maximum diameter and the minimum diameter of each crystal grain using an electron microscope. When the reaction rate is in the range of 0.25 to 0.5, Nd
_Although the orientation of 2Fe ₁₄ B is transferred to Fe ₂ B and high anisotropy is obtained, if the relative reaction rate is out of this range, the transfer is not successful and only an isotropic powder is obtained. On the other hand, when the reaction rate is low, the reaction becomes non-uniform and a high Bs is obtained, but NdFeB remains and a high coercive force (i
Hc) cannot be obtained. Embodiment 2. FIG. No. 1 of Example 1 was mainly used. Table 2 shows the results of forward transformation of the alloy structure by hydrogen storage under the hydrogen storage conditions of 1.
The heat treatment after the forward transformation was performed at the holding temperature, the holding hydrogen gas pressure and the holding time shown in (No. 54, hydrogen storage under No. 52 hydrogen storage conditions of Example 1 and order of alloy structure Perverted.). Thereafter, the hydrogen gas pressure was reduced at the holding temperature so that the reverse transformation relative velocity became 0.26, a reverse transformation reaction by dehydrogenation was caused as in Example 1, and then a heat treatment after the reverse transformation reaction was performed as in Example 1. 8
It was kept at 20 ° C. under vacuum for 30 minutes and then cooled. Thus, the rare earth magnet powder shown in Table 2 was produced.

The residual magnetic flux density of the obtained rare earth magnet powder,
The intrinsic coercive force and (BH) max were measured to determine the anisotropic ratio. Table 2 shows the co-transformation relative reaction rate, holding time, holding temperature, holding pressure, residual magnetic flux density, anisotropic rate, specific coercive force, and (BH) max of the magnet powder together with the coercive force and anisotropic ratio. . After completion of the forward reaction in the same manner as in Example 1, heat treatment was continued at the holding temperature and pressure to alleviate the strain associated with the forward transformation, and then dehydrogenation (hydrogen pressure 0.0001 MPa (0.
001 atm)), the result was that high anisotropy was maintained as in Example 1. Then, by holding for 60 minutes or more, the coercive force becomes higher as compared with the first embodiment. On the other hand, the anisotropy is not lost by holding for a short time, but the coercive force is low. When the reaction rate is high, the anisotropy is lost, and the anisotropy does not recover even if the retention and dehydrogenation are performed continuously. Embodiment 3 FIG. No. 2 of Example 2 was mainly used. Under the hydrogen storage condition of 7, the alloy structure was forward transformed by hydrogen storage, and then 180
The sample temperature, the reverse transformation relative velocity, and the reverse transformation hydrogen gas pressure of 0.0001 MPa (0.00
1 atm), and then heat-treated at 820 ° C. under vacuum for 30 minutes, and then quenched (N 2
o. As for No. 56 of Example 1, Hydrogen was absorbed under the hydrogen storage conditions of 52 to perform a normal transformation of the alloy structure. ). In this way, rare earth magnet powders shown in Table 3 were produced.

The residual magnetic flux density of the obtained rare earth magnet powder,
The intrinsic coercive force and (BH) max were measured to determine the anisotropic ratio. Forward transformation relative reaction rate, retention time, reverse transformation relative velocity, sample temperature, residual magnetic flux density, anisotropy rate, intrinsic coercivity, and (BH) m of the magnet powder together with coercivity and anisotropic ratio
Table 3 also shows ax. When the reverse transformation reaction rate is in the range of 0.1 to 0.4, the transferred orientation is transferred to Nd ₂ Fe ₁₄ B without disturbing and anisotropy is obtained. As can be seen from FIG. 55, when the reverse transformation reaction rate is higher than that, the anisotropy decreases and high characteristics cannot be obtained.

On the other hand, no. As shown in 56, when the reaction rate of the transformation is high, anisotropy cannot be obtained even if the subsequent treatment is good. Embodiment 4. FIG. No. 3 of Example 3 Normal transformation like 11
After heat treatment and reverse transformation, heat treatment was performed at the holding temperature and holding time shown in Table 4. (Note that No. 5
No. 6 of Example 3 is No. 6. 54 were subjected to forward transformation, heat treatment and reverse transformation. Thus, the rare earth magnet powder shown in Table 4 was produced.

Using the obtained powdered magnet powder, 3 g of a phenol resin was used as a thermosetting resin per 100 g of the powdered magnet, and compression-molded in a mold to obtain a bonded magnet. In addition, two types, one in which a magnetic field of 2.0 T (20 kOe) was applied at the time of molding and one without a magnetic field, were obtained. The residual magnetic flux density, intrinsic coercive force and (BH) max of the obtained rare earth magnet powder were measured to determine the anisotropic ratio.
Further, residual hydrogen contained in this magnet was determined. The value of the residual hydrogen was shown in terms of% by weight when the whole was taken as 100% by weight. Furthermore, the maximum energy product (BH) ma of the bonded magnet
x was measured.

Table 4 shows the processing conditions of the forward transformation relative reaction rate, the holding time, the reverse transformation relative rate, the holding temperature and the holding time after the reverse transformation, together with the coercive force and the anisotropic rate, and Table 5 shows the measured magnetic properties. Shown in It can be seen that by holding the dehydrogenation time for 25 minutes or longer, a sufficient coercive force can be obtained without sufficient loss of hydrogen and loss of anisotropy. On the other hand, when the holding time is short, a little hydrogen remains, and a high coercive force cannot be obtained.

When the reaction rate of the anisotropic reaction is high,
Although a high coercive force is obtained, the anisotropy is completely eliminated and only an isotropic powder is obtained. Embodiment 5 FIG. Nd: 12.5 at%, B: 6.2 at%,
The trace amounts of Ga and Nb shown in Table 6 were added to the alloy consisting of the balance Fe, melted by button arc melting in the same manner as described in Example 1, and homogenized at 1140 ° C. High-temperature hydrogen heat treatment was performed under the conditions shown. Thereafter, the magnetic properties were measured in the same manner as in Example 4. Table 7 shows the measurement results. The addition of Ga has a cleaning effect on grain boundaries for suppressing the generation of reverse magnetic domains, and provides a high coercive force. Further, the addition of Nb has a function of improving the transfer effect. As a result, Ga, N
350k, which has not been obtained by adding a trace amount of element b
High characteristics of J / m ³ (44.0 MGOe) can be obtained.

The anisotropic magnet powder of the present invention is anisotropic (Br)
/Bs=1.6T (16KG)) is 0.65 or more. By using this anisotropic magnet powder, an anisotropic bonded magnet having a high (BH) max can be obtained. Further, the anisotropic magnet powder of the present invention can be produced by setting the forward transformation rate of hydrogen storage within a predetermined range.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between an alloy composition and a reaction rate of a forward transformation reaction of a rare earth alloy.

FIG. 2 is a diagram showing a relationship between a reaction temperature and a reaction rate of a forward transformation reaction of a rare earth alloy.

FIG. 3 is a diagram showing a relationship between a hydrogen gas pressure and a reaction rate in a forward transformation reaction of a rare earth alloy.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01F 1/053 H01F 1/04 H

Claims (8)

[Claims] 1. An anisotropic (Br / B) heat-treated with hydrogen at a high temperature.
s, where Bs is 1.6T (16 kG)).
RFeB composed of a rare earth element (hereinafter, referred to as R) containing yttrium (Y) of 70 or more, boron (B), and unavoidable impurity elements, and the balance of iron (Fe)
Anisotropic magnet powder comprising a base alloy. 2. The method according to claim 1, wherein the RFeB alloy is 12 to 15 at.
2. The anisotropic magnet powder according to claim 1, wherein the powder contains R of 5.5% to 8 at%, and unavoidable impurities, and the balance is Fe. 3. The anisotropic magnet powder according to claim 1, wherein the aspect ratio of the crystal grains of the RFeB-based alloy is 2.0 or less. 4. A residual magnetic flux density (Br) of 1.2T to 1.T.
5T (12-15 kG), specific coercive force (iHc) is 63
6 to 1272 kA / m (8.0 to 16 kOe), (B
H) max is 238 to 358 kJ / m ³ (30 to 45 M
The anisotropic magnet powder according to claim 1, which is GOe). 5. A high-temperature hydrogen heat treatment and anisotropic (Br / B
s, where Bs is 1.6T (16 kG)).
A rare earth element containing yttrium (Y) of 70 or more (hereinafter referred to as R), boron (B), and gallium (G
An anisotropic magnet powder comprising an RFeB-based alloy containing at least one of a) and niobium (Nb) and an unavoidable impurity element, and the balance being iron (Fe). 6. The composition of R is 12 to 15 at%, the composition of B is 5.5 to 8 at%, and the composition of Ga is 0.06 at%.
1 to 1.0 at%, and the composition of Nb is 0.01 to 0.6 at%.
The anisotropic magnet powder according to claim 5, which is at%. 7. The anisotropic magnet powder according to claim 5, wherein the aspect ratio of crystal grains of the RFeB-based alloy is 2.0 or less. 8. A residual magnetic flux density (Br) of 1.2T-1.
5T (12-15 kG), specific coercive force (iHc) is 63
6 to 1272 kA / m (8.0 to 16 kOe), (B
H) max is 238 to 358 kJ / m ³ (30 to 45 M
The anisotropic magnet powder according to claim 5, which is GOe).