JP4618437B2 - Method for producing rare earth permanent magnet and raw material alloy thereof - Google Patents

Description

  The present invention relates to a method for producing a rare earth permanent magnet and a raw material alloy thereof.

R-T-B rare earth permanent magnets (R is one or more rare earth elements, T is Fe, or Fe and Co) have excellent magnetic properties, and Nd as the main component is Since it is abundant in resources and relatively inexpensive, it is used in electrical equipment such as various motors.
An example of a method for producing a rare earth permanent magnet is a powder metallurgy method. Powder metallurgy is widely used because it can be manufactured at low cost. In the powder metallurgy method, a raw material alloy is coarsely and finely pulverized to obtain a finely pulverized powder of several μm. The finely pulverized powder thus obtained is magnetically oriented in a magnetic field, press-molded while the magnetic field is applied, and the resulting molded body is heat treated to obtain a sintered body. And the RTB system rare earth permanent magnet is manufactured by processing to a predetermined shape, and also performing surface treatment as needed.

Here, strip cast alloys are frequently used as raw material alloys in order to improve the properties of R-T-B rare earth permanent magnets, particularly to improve the coercive force. The strip cast alloy is formed into a flake shape by rapidly cooling and solidifying a molten metal alloy having a predetermined composition on the surface of a metal roll.
Conventionally, attempts have been made to improve the magnetic characteristics by controlling the particle size and the like of the strip cast alloy (see, for example, Patent Documents 1 to 3).

JP-A-63-317643 JP-A-5-222488 JP 2000-219942 A

In spite of these various attempts, it has been found that the actual results of mass production do not always give the results as tested in the research and development stages.
In the process of heat-treating the molded body after molding, a large-scale furnace for mass production is used, but due to its large size, the uniformity of the furnace temperature distribution is inferior to that of a small furnace for testing. For this reason, even if the temperature of the furnace is set under conditions within the proper range obtained by the test, the temperature may deviate from the proper range depending on the position in the furnace. As a result, the RTB-based rare earth permanent magnet that has been heat-treated at that portion is out of the proper range, and thus high magnetic properties (particularly, coercive force HcJ) cannot be obtained.
Therefore, even if it is a raw material alloy of the same composition, a material having a large dependency of the coercive force on the heat treatment temperature is poor in production efficiency.
The present invention has been made on the basis of such a technical problem, and provides a method for producing a rare earth permanent magnet and a raw material alloy thereof capable of expanding the range of an appropriate heat treatment temperature range and improving mass productivity. With the goal.

As a result of intensive studies by the present inventors for this purpose, an appropriate range at the time of heat treatment for increasing the coercive force is obtained by setting a composition distribution in which Al becomes poor in the grain boundary phase of the strip cast alloy. I found out that I can spread
The present invention made based on this finding is a method for producing a R-T-B (R: one or more rare earth elements, T: Fe, or Fe and Co, B: boron) based rare earth permanent magnet. There is a pulverization process for pulverizing a raw material alloy having less Al content in the grain boundary phase than other regions, a molding process for molding the pulverized powder that has undergone the pulverization process in a magnetic field, and a molding obtained in the molding process. And a aging treatment step of heat-treating the sintered body obtained in the sintering step. By using such a raw material alloy, it becomes possible to widen the range of an appropriate heat treatment temperature at which a high coercive force can be obtained (hereinafter sometimes referred to as an appropriate temperature range).
At this time, when the first heat treatment in the temperature region lower than the sintering temperature in the sintering step and the second heat treatment in the temperature region lower than the temperature region in the first heat treatment are performed as the heat treatment, the temperature is particularly low. It is possible to widen the appropriate temperature range in the second heat treatment on the side.
Such a raw material alloy is in the form of a ribbon formed by quenching a molten metal on a roll.
The finally obtained rare earth permanent magnet includes a main phase crystal grain composed of an R ₂ T ₁₄ B phase and a grain boundary phase containing more R than the main phase crystal grain.
In the pulverization step, a raw material alloy piece made of a low R alloy mainly composed of R ₂ T ₁₄ B crystal grains and a raw material alloy piece made of a high R alloy containing more R than the low R alloy are crushed. In the forming step, The pulverized powder obtained by pulverizing the low R alloy and the high R alloy may be molded in a magnetic field.

  The present invention is a raw material alloy of an R-T-B system rare earth permanent magnet, wherein the Al content in the grain boundary phase is poorer than other regions, and the R content is richer than other regions. It can also be a raw material alloy of rare earth permanent magnets characterized in that there is. At this time, in the grain boundary phase where the content of R is richer than in other regions, R is present as R or / and an R—Fe-based composition.

  According to the present invention, it is possible to increase the range of the appropriate range of the heat treatment temperature and improve the mass productivity.

The present invention will be described in detail based on the following embodiments.
First, a method for producing a rare earth permanent magnet will be described. First, the magnet to which the present invention is applied will be described.
The present invention is preferably applied to a neodymium permanent magnet represented by RTB (R is one or more rare earth elements, and T is Fe or Fe and Co). Of course, the present invention is not limited to this, and it is also effective to apply the present invention to other rare earth permanent magnets.

The RTB-based permanent magnet contains 25 to 37 wt% of a rare earth element (R). Here, R has a concept including Y. Therefore, one or two of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Selected from more than species. If the amount of R is less than 25 wt%, the R ₂ T ₁₄ B phase, which is the main phase of the R-T-B system permanent magnet, is not sufficiently generated, and α-Fe having soft magnetism is precipitated, resulting in coercive force. Is significantly reduced. On the other hand, when R exceeds 37 wt%, the volume ratio of the R ₂ T ₁₄ B phase, which is the main phase, decreases, and the residual magnetic flux density decreases. Further, R reacts with oxygen, the amount of oxygen contained increases, and accordingly, the R-rich phase effective for the generation of coercive force decreases, leading to a decrease in coercive force. Therefore, the amount of R is set to 25 to 37 wt%. A desirable amount of R is 28 to 35 wt%.

Moreover, the RTB system permanent magnet to which this invention is applied contains boron (B) 0.5 to 4.5 wt%. When B is less than 0.5 wt%, a high coercive force cannot be obtained. On the other hand, when B exceeds 4.5 wt%, the residual magnetic flux density tends to decrease. Therefore, the upper limit of B is set to 4.5 wt%. A desirable amount of B is 0.5 to 1.5 wt%, and a more desirable amount of B is 0.8 to 1.2 wt%.
The RTB-based permanent magnet to which the present invention is applied can contain Co in an amount of 5.0 wt% or less (excluding 0), preferably 0.1 to 3.0 wt%. Co forms the same phase as Fe, but is effective in improving the Curie temperature and the corrosion resistance of the grain boundary phase.

  The RTB-based permanent magnet to which the present invention is applied allows the inclusion of other elements. In the present invention, it is essential to contain Al. Addition of Al makes it possible to increase the coercive force and improve the temperature characteristics of the permanent magnet obtained, and the addition amount is preferably 0.03 to 1.0 wt%, more preferably 0.03 to 0.5 wt%. If the amount is more than the amount added, the residual magnetic flux density is lowered and the magnetic properties are lowered, and if the amount is less than the amount added, the effect of adding becomes dilute. In addition, for example, elements such as Cu, Zr, Ti, Bi, Sn, Ga, Nb, Ta, Si, V, Ag, and Ge can be appropriately contained. On the other hand, it is desirable to reduce impurity elements such as oxygen, nitrogen, and carbon as much as possible. In particular, the amount of oxygen that impairs magnetic properties is preferably 7000 ppm or less, more preferably 5000 ppm or less. This is because when the amount of oxygen is large, the rare-earth oxide phase, which is a nonmagnetic component, increases and the magnetic properties are deteriorated.

Such an R-T-B permanent magnet is manufactured through a process as shown in FIG.
Hereinafter, the content of each process is demonstrated.
<Raw material alloy production>
The raw material alloy for the RTB-based permanent magnet can be produced by a strip casting method in a vacuum or an inert gas, preferably in an Ar atmosphere. In the strip casting method, a molten metal obtained by melting a raw metal in a non-oxidizing atmosphere such as an Ar gas atmosphere is ejected onto the surface of a rotating roll. The melt rapidly cooled by the roll is rapidly solidified in the form of a thin plate or flakes (scales). This rapidly solidified alloy has a homogeneous structure with a crystal grain size of 1 to 50 μm.

In the present invention, when an R-T-B rare earth permanent magnet is obtained, an alloy mainly composed of R ₂ T ₁₄ B crystal grains (hereinafter referred to as a low R alloy) and more R than a low R alloy. A so-called mixing method using an alloy containing the alloy (hereinafter referred to as a high R alloy) can be applied.
As the mixing method, a method of mixing two or more kinds of alloy content of R is mainly different R _{2 T} 14 _B crystal grains, the content is different from R ₂ T heavy rare earths (Dy, Tb, etc.) A method of mixing two or more kinds of alloys mainly composed of ₁₄ B crystal grains can be applied.
On the other hand, the case where two or more kinds of alloys having different compositions are not used is referred to as a one-alloy method, and an R-T-B rare earth permanent magnet may be obtained by applying this one-alloy method.

In addition, in the thin plate or flaky raw material alloy obtained by the strip casting method (hereinafter sometimes referred to as a quenched ribbon alloy), the additive Al is not evenly dispersed throughout the alloy. However, it is preferable to use a material in which the amount of Al in the grain boundary phase portion where R is present as the R or / and R-Fe composition is less than in other regions. In this region, the R content is more distributed than the other regions.
Such a quenched ribbon alloy can be obtained, for example, by jetting a molten metal onto a roll and controlling the temperature of the alloy when peeling from the roll. For example, when the temperature of the alloy when peeling from the roll is set to 850 to 1100 ° C., a quenched ribbon alloy having the above distribution can be obtained. Other factors controlling the composition distribution of the quenched ribbon alloy include the temperature of the molten metal, the thickness of the alloy on the roll, the peripheral speed of the roll, and the surface condition of the roll.

<Crushing>
The obtained quenched ribbon alloy is subjected to a pulverization process. In the case of the mixing method, the low R alloy and the high R alloy are pulverized separately or together. The pulverization process includes a coarse pulverization process and a fine pulverization process. First, the rapidly quenched ribbon alloy is coarsely pulverized to a particle size of about several hundred μm. The coarse pulverization is desirably performed in an inert gas atmosphere using a stamp mill, a jaw crusher, a brown mill or the like. Prior to coarse pulverization, it is effective to perform pulverization by occluding hydrogen in the quenched ribbon alloy and then releasing it. The hydrogen releasing treatment is performed for the purpose of reducing hydrogen as an impurity as a rare earth permanent magnet. The temperature of heating and holding for releasing hydrogen is 200 ° C. or higher, desirably 350 ° C. or higher. The holding time varies depending on the relationship with the holding temperature, the thickness of the quenched ribbon alloy, etc., but is at least 30 minutes or more, preferably 1 hour or more. The hydrogen release treatment is performed in a vacuum or Ar gas flow. The hydrogen storage process and the hydrogen release process are not essential processes. This hydrogen pulverization can be regarded as coarse pulverization, and mechanical coarse pulverization can be omitted.

  After the coarse pulverization process, the process proceeds to the fine pulverization process. A jet mill is mainly used for fine pulverization, and a coarsely pulverized powder having a particle size of about several hundreds of μm has an average particle size of 1 to 10 μm, preferably 2 to 7 μm. The jet mill releases a high-pressure inert gas from a narrow nozzle to generate a high-speed gas flow, accelerates the coarsely pulverized powder with this high-speed gas flow, collides with the coarsely pulverized powder, and collides with the target or the container wall. It is a method of generating a collision and crushing. A lubricant may be added to and mixed with the coarse powder before pulverization, or a lubricant may be added and mixed after pulverization or both.

  In the case of the mixing method, the timing of mixing the two kinds of alloys is not limited. However, when the low R alloy and the high R alloy are separately pulverized in the pulverization step, the pulverized low R alloy powder is used. And high R alloy powder in a nitrogen atmosphere. The mixing ratio of the low R alloy powder and the high R alloy powder may be about 50:50 to 97: 3 by weight. The mixing ratio when the low R alloy and the high R alloy are pulverized together is the same.

<Molding in magnetic field>
The finely pulverized powder (magnetic material) obtained as described above is molded in a magnetic field to obtain a molded body. In the present embodiment, an orthogonal magnetic field forming method in which the pressing direction and the direction of the applied magnetic field are orthogonal is used. A parallel magnetic field forming method, which is a forming method in which the pressing direction and the direction of the applied magnetic field are parallel, can also be used.
The molding pressure in the magnetic field molding may be in the range of 30 to 300 MPa (0.3 to 3 ton / cm ² ). The orientation becomes better as the molding pressure is lower. However, if the molding pressure is too low, the strength of the molded body will be insufficient, causing problems when handling the molded body. Considering this point, the molding pressure is selected from the above range. To do. The final relative density of the molded body obtained by molding in a magnetic field is preferably 50 to 65%.
The magnetic field applied in the present invention may be about 800 to 1600 kA / m (10 to 20 kOe). The applied magnetic field is not limited to a static magnetic field, and may be a pulsed magnetic field. A static magnetic field and a pulsed magnetic field can be used in combination. When a pulsed magnetic field is used, a magnetic field as high as about 2400 kA / m (30 kOe) can be used.

<Sintering>
The molded body obtained by molding in a magnetic field is sintered in a vacuum or an inert gas atmosphere to obtain an R-T-B permanent magnet. Although it is necessary to adjust sintering temperature by various conditions, such as a composition, a grinding | pulverization method, the difference of an average particle diameter, and a particle size distribution, what is necessary is just to sinter at 1000-1200 degreeC for about 1 to 10 hours.

<Aging heat treatment>
After sintering, the obtained sintered body can be subjected to an aging treatment. This step is an important step for controlling the coercive force (HcJ), and it is preferable to perform an aging treatment in an inert gas atmosphere or in a vacuum. As this aging treatment, a two-stage aging treatment is preferable. In the first stage aging treatment step (first heat treatment), the temperature is maintained within a range of 700 to 900 ° C. for 0.5 to 3 hours. Next, a first quenching step is provided for quenching to room temperature to 200 ° C. In the second aging treatment step (second heat treatment), the temperature is maintained within a range of 500 to 700 ° C. for 0.5 to 3 hours. Next, a second quenching step for quenching to room temperature is provided. In the case where the aging treatment is performed in one stage, the aging treatment at 500 to 900 ° C. is preferably performed.

As described above, in the grain boundary phase, the additive Al is not uniformly dispersed throughout the alloy, but the quenching thinness in which the amount of Al in the grain boundary phase portion is less than that in other portions. By using the band alloy, it is possible to widen the range of the second aging treatment temperature at which a high coercive force can be obtained.
In this way, since the range of the appropriate range of the heat treatment temperature can be widened, the R-T-B rare earth permanent having a stable and high coercive force regardless of the temperature distribution variation in the heat treatment furnace during mass production. A magnet can be obtained, and mass productivity can be improved.

Here, since the effect by using the said structure was confirmed, the result is shown below.
The following two types of quenched ribbon alloys were produced by strip casting.
(1) Low R alloy: 30 wt% Nd-0.2 wt% Al-1.2 wt% B-bal. Fe
(2) High R alloy: 45 wt% Nd-0.2 wt% Al-10 wt% Co-1.0 wt% Cu-bal. Fe
At this time, the low R alloy of (1) is obtained by changing the molten metal temperature, the alloy thickness on the roll surface, the peripheral speed of the roll, the position of the tundish for supplying the molten metal to the roll, etc. The temperature of the quenched ribbon alloy when stripped from above (strip stripping temperature) was set to be shown in Table 1.

The thus obtained (1) quenched R ribbon alloy of low R alloy was analyzed with an X-ray microanalyzer (EPMA).
The results are shown in FIGS. In these drawings, a portion having a small amount of Fe and a large amount of Nd (portion surrounded by a dotted line in the drawing) is an Nd-rich phase, that is, a grain boundary phase.
In addition, the average crystal grain diameter in Table 1 was calculated | required by the space | interval of the Nd-rich phase.
In these FIG. 3, in Comparative Example 1 in which the strip peeling temperature is less than 850 ° C., the Al amount is almost uniformly dispersed throughout the alloy without changing from the other regions even in the Nd-rich phase. On the other hand, as shown in FIG. 2, in the example in which the strip peeling temperature is 850 ° C. or more, it can be seen that the amount of Al is clearly lower than that in other regions in the Nd-rich phase.

  Each of the obtained alloys (1) and (2) was occluded with hydrogen at room temperature, and then dehydrogenated at 600 ° C. for 1 hour in an Ar atmosphere to obtain coarsely pulverized powder. The raw material alloy pieces were coarsely pulverized to about several hundred μm by the dehydrogenation treatment.

  0.05 wt% of zinc stearate as a lubricant was added to the coarsely pulverized powder obtained by the hydrogen pulverization treatment. The coarsely pulverized powder to which zinc stearate was added was finely pulverized with a jet mill until the average particle size became 5.0 to 6.0 μm. The pulverized particle size was measured with HELOS & RODOS manufactured by Sympatech.

Then, the fine powders of the obtained alloys (1) and (2) were made into a desired final composition: 31.5 wt% Nd-1.0 wt% Co-0.1 wt% Cu-0.2 wt% Al-1.1 wt. % B-bal. It mixed for 30 minutes with a Nauta mixer so that it might become Fe.
In addition, the mixing ratio (weight ratio) of the alloy (1) which is a high R alloy and the alloy (2) which is a low R alloy is 90:10.

After sufficient time had passed after the above treatment, the finely pulverized powder was molded in a magnetic field. In addition, shaping | molding in a magnetic field was performed on the conditions of shaping | molding pressure: 140MPa and applied magnetic field: 1110kA / m.
The molded body obtained by molding in a magnetic field was sintered. Sintering was carried out under conditions of holding at 1060 ° C. for 4 hours in a vacuum. Next, the obtained sintered body was subjected to a two-stage aging treatment of 900 ° C. × 1 hour and 510-590 ° C. × 1 hour (both in an Ar atmosphere).

The coercivity (HcJ) of the rare earth permanent magnet thus obtained was measured.
As a result, as can be seen from the absolute value data shown in FIG. 4 (a), although the absolute value of the coercive force is improved by reducing the crystal grain size, the appropriate range of the second aging treatment temperature is not widened. As shown in FIG. 4 (b), when compared using the coercive force when the second aging treatment temperature is 530 ° C. as a reference, the second aging treatment temperature is obtained when the quenched ribbon alloys of Comparative Examples 1 and 2 are used. When the temperature exceeds 550 ° C., the coercive force is rapidly decreased, whereas when the quenched ribbon alloy of the example is used, the coercive force does not decrease until the second aging temperature exceeds 570 ° C. I understand that.
That is, it can be seen that the range of the second aging temperature at which a high coercive force can be obtained can be expanded by using a quenched ribbon alloy in which the amount of Al falls in the grain boundary phase.

Then, the case where only one stage of aging treatment was considered was also examined.
In the same manner as in Example 1, two types of quenched ribbon alloys of low R alloy and high R alloy of Example and Comparative Example 1 were prepared, and these were coarsely pulverized and finely pulverized, and formed by forming in a magnetic field. The body was sintered.
Next, the obtained sintered body was subjected to a one-step aging treatment of only 510 to 590 ° C. × 1 hour (both in an Ar atmosphere).

The coercivity (HcJ) of the rare earth permanent magnet thus obtained was measured.
As a result, as shown in FIG. 5, when the quenched ribbon alloy of Comparative Example 1 was used, the coercive force rapidly decreased when the aging treatment temperature exceeded 550 ° C. When the band alloy is used, it can be seen that the coercive force does not decrease until the aging treatment temperature exceeds 570 ° C.

Here, since the effect by using the said structure was confirmed, the result is shown below.
By the strip casting method, the following rapidly quenched ribbon alloy was produced by the single alloy method.
27 wt% Nd-4.5 wt% Dy-0.2 wt% Al-1.5 wt% Co-0.1 wt% Cu-1.0 wt% B-bal. Fe
At this time, by the same method as in Example 1, the temperature of the quenched ribbon alloy when stripped from the roll surface (strip stripping temperature) was controlled to be 900 and 850 ° C.

  The obtained alloy was made into a coarsely pulverized powder and a finely pulverized powder under the same conditions as in Example 1.

Then, the fine powder of the obtained alloy was molded in a magnetic field. In addition, shaping | molding in a magnetic field was performed on the conditions of shaping | molding pressure: 140MPa and applied magnetic field: 1110kA / m.
The molded body obtained by molding in a magnetic field was sintered. Sintering was carried out under conditions of holding at 1090 ° C. for 4 hours in a vacuum. Next, the obtained sintered body was subjected to a two-stage aging treatment of 850 ° C. × 1 hour and 520-590 ° C. × 1 hour (both in an Ar atmosphere).

The coercivity (HcJ) of the rare earth permanent magnet thus obtained was measured.
As a result, as shown in FIG. 6 (a), when a rapidly stripped ribbon alloy having a strip peeling temperature of 850 ° C. is used, the coercive force rapidly decreases when the second aging temperature exceeds 570 ° C. On the other hand, when a rapidly stripped ribbon alloy having a strip peeling temperature of 900 ° C. is used, it can be seen that the coercive force does not decrease until the second aging temperature exceeds 580 ° C.
That is, it can be seen that by increasing the strip peeling temperature to 900 ° C., the range of the second aging treatment temperature at which a high coercive force can be obtained can be expanded.

Subsequently, a total of four types of quenched ribbon alloys were obtained by strip casting using the following two types of alloys under two types of conditions described later.
(1) High Dy alloy: 25.5 wt% Nd-6 wt% Dy-0.2 wt% Al-1.5 wt% Co-0.1 wt% Cu-1.0 wt% B-bal. Fe
(2) Low Dy alloy: 28.5 wt% Nd-3 wt% Dy-0.2 wt% Al-1.5 wt% Co-0.1 wt% Cu-1.0 wt% B-bal. Fe
At this time, both the alloys (1) and (2) change the molten metal temperature, the alloy thickness on the roll surface, the peripheral speed of the roll, the position of the tundish for supplying the molten metal to the roll, and the like. The temperature of the quenched ribbon alloy when stripped from the roll surface (strip stripping temperature) was controlled to be 900 and 850 ° C.

  Each of the obtained alloys (1) and (2) was occluded with hydrogen at room temperature, and then dehydrogenated at 600 ° C. for 1 hour in an Ar atmosphere to obtain coarsely pulverized powder. The raw material alloy pieces were coarsely pulverized to about several hundred μm by the dehydrogenation treatment.

  0.05 wt% of zinc stearate as a lubricant was added to the coarsely pulverized powder obtained by the hydrogen pulverization treatment. The coarsely pulverized powder to which zinc stearate was added was finely pulverized with a jet mill until the average particle size became 4.5 to 5.0 μm. The pulverized particle size was measured with HELOS & RODOS manufactured by Sympatech.

And among the fine powders of the obtained alloys (1) and (2), fine powders obtained from an alloy having the same strip peeling temperature are mixed into a desired final composition: 27 wt% Nd-4.5 wt% Dy-1. 5 wt% Co-0.1 wt% Cu-0.2 wt% Al-1.0 wt% B-bal. Fe
The mixture was mixed with a Nauta mixer for 30 minutes.
In addition, the mixing ratio of the fine powder obtained from the alloy (1) which is a high Dy alloy and the fine powder obtained from the alloy (2) which is a low Dy alloy was 50:50.

Then, the fine powder of the obtained alloy was molded in a magnetic field. In addition, shaping | molding in a magnetic field was performed on the conditions of shaping | molding pressure: 140MPa and applied magnetic field: 1110kA / m.
The molded body obtained by molding in a magnetic field was sintered. Sintering was carried out under conditions of holding at 1090 ° C. for 4 hours in vacuum. Next, the obtained sintered body was subjected to a two-stage aging treatment of 850 ° C. × 1 hour and 520-590 ° C. × 1 hour (both in an Ar atmosphere).

The coercivity (HcJ) of the rare earth permanent magnet thus obtained was measured.
As a result, as shown in FIG. 6 (b), in the case where a rapidly stripped ribbon alloy having a strip peeling temperature of 850 ° C. is used, the coercive force rapidly decreases when the second aging temperature exceeds 560 ° C. On the other hand, when a rapidly stripped ribbon alloy having a strip peeling temperature of 900 ° C. is used, it can be seen that the coercive force does not decrease until the second aging temperature exceeds 580 ° C.
That is, it can be seen that by increasing the strip peeling temperature to 900 ° C., the range of the second aging treatment temperature at which a high coercive force can be obtained can be expanded.

It is a flowchart which shows the manufacturing process of the RTB system rare earth permanent magnet in this Embodiment. It is a figure which shows the analysis result by the X-ray microanalyzer of the quenching thin strip alloy in an Example. It is a figure which shows the analysis result by the X-ray microanalyzer of the quenching thin ribbon alloy in a comparative example. It is a figure which shows the relationship between a 2nd aging treatment temperature and a magnetic characteristic (coercive force (HcJ)), (a) is data of an absolute value, (b) is a retention when a 2nd aging treatment temperature is 530 degreeC. It is data based on relative values based on magnetic force. It is a figure which shows the relationship between the aging treatment temperature of only 1 step | paragraph, and a magnetic characteristic (coercive force (HcJ)), (a) is data of an absolute value, (b) is the retention when an aging treatment temperature is 530 degreeC. It is data based on relative values based on magnetic force. It is a figure which shows the relationship between the 2nd aging treatment temperature at the time of changing strip stripping temperature in 1 alloy method and a mixing method, and a magnetic characteristic (coercive force (HcJ)).

Claims (6)

R-T-B (R: one or more of rare earth elements, T: Fe, or Fe and Co, B: boron), a method for producing a rare earth permanent magnet,
A pulverization step of pulverizing a raw material alloy in which the content of Al in the grain boundary phase is smaller than in other regions;
A molding step of molding the pulverized powder that has undergone the pulverization step in a magnetic field;
A sintering step of sintering the molded body obtained in the molding step;
A heat treatment step of heat treating the sintered body obtained in the sintering step;
A method for producing a rare earth permanent magnet. The heat treatment is a first heat treatment in a temperature region lower than a sintering temperature in the sintering step,
The method for producing a rare earth permanent magnet according to claim 1, wherein a second heat treatment in a temperature region lower than a temperature region in the first heat treatment is performed.   3. The method for producing a rare earth permanent magnet according to claim 1, wherein the raw material alloy is in the form of a ribbon formed by quenching a molten metal on a roll. 4. The rare earth permanent magnet, the main phase crystal grains consisting of R 2 _T 14 _B phase, in any one of claims 1 to 3, characterized in that it comprises a grain boundary phase containing a large amount of R than said main phase crystal grains The manufacturing method of the rare earth permanent magnet of description. In the pulverization step, a raw material alloy piece made of a low R alloy mainly composed of R ₂ T ₁₄ B crystal grains and a raw material alloy piece made of a high R alloy containing more R than the low R alloy are crushed,
The rare earth permanent magnet production according to any one of claims 1 to 4, wherein in the forming step, the pulverized powder obtained by pulverizing the low R alloy and the high R alloy is formed in a magnetic field. Method. R-T-B (R: one or more of rare earth elements, T: Fe, or Fe and Co, B: boron) based rare earth permanent magnet alloy,
A raw material alloy for a rare earth permanent magnet, characterized in that the content of Al in the grain boundary phase is poorer than in other regions, and the content of R is richer than in the other regions.

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