JP2000219943A - Alloy ribbons for rare earth magnets, alloy fine powders and methods for producing them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a raw material suitable for producing a rare earth permanent magnet capable of increasing the density of a sintered body at a low temperature, and a method for preparing the raw material. SOLUTION: An RTB-based rare-earth permanent magnet raw material alloy is quenched by a roll quenching method so that the thickness of the ribbon is 30 to 30 mm.
1000 μm, 1 to 30% by volume ratio near the cooling surface
Has a chill crystal with a particle size of 3 μm or less, and the rest has a particle size of 3 to 5
0 μm granular crystal, a columnar crystal having a minor axis of 3 to 100 μm and a major axis of 20 to 600 μm, α-
It is assumed to be composed of a portion where Fe is precipitated. A fine powder obtained by coarsely pulverizing the alloy ribbon for a raw material of permanent magnet and further finely pulverizing the coarsely pulverized powder, having a particle diameter of 3 μm
It is assumed that 1 to 30% of the following fine powder is contained, and the particle size of the remaining is substantially 3 to 10 μm. The method of coarse grinding is
It is a method of performing dehydrogenation after absorbing hydrogen in the alloy ribbon for a raw material of a permanent magnet, and it is preferable that the pulverization is performed by a jet mill.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a raw material suitable for producing a rare earth permanent magnet having excellent magnetic properties and a method for producing the raw material.

[0002]

2. Description of the Related Art Rare earth permanent magnets are widely used in the field of electric and electronic equipment because of their excellent magnetic properties and economical efficiency. Among these rare-earth permanent magnets, the RTB-based rare-earth permanent magnets (R is a rare-earth element mainly composed of Nd, T is Fe, or a transition metal such as Fe and Co) are mainly used as compared with rare-earth cobalt magnets. Since the element Nd is more abundant than Sm, and expensive Co is not heavily used, raw material costs are low,
It is an extremely excellent permanent magnet, with magnetic properties far superior to rare earth cobalt magnets. Conventionally, an RTB-based rare earth permanent magnet raw material alloy has been manufactured by a mold casting method of casting a molten alloy into a mold. Primary γ-Fe precipitates during the cooling and solidification process of this alloy, and after cooling, segregates as α-Fe. α-Fe deteriorates the pulverizing ability in the fine pulverizing step in the permanent magnet manufacturing step, and if it remains in the magnet after the sintering step, it lowers the magnetic properties. for that reason,
It is necessary to perform a homogenizing heat treatment at a high temperature for a long period of time to eliminate α-Fe. However, the homogenizing heat treatment increases the crystal grain size of the main phase (R ₂ T ₁₄ B) in the alloy, and reduces the magnetic field. The characteristics are lowered, and the manufacturing cost is increased. Therefore, using a rapid cooling technique such as a strip casting method, while suppressing the segregation of α-Fe,
It has been reported that an alloy for a raw material of a permanent magnet in which the crystal grain size of the main phase is reduced is manufactured, and a permanent magnet is manufactured using the alloy.

[0003] In Japanese Patent No. 2665590, the main phase (R ₂
T ₁₄ B) The crystal is a homogeneous columnar crystal having a minor axis of 3 to 20 μm, and the coercive force (i
It is stated that a magnet having a high Hc) can be manufactured. Patent No. 26
In 39609, solidification is uniformly performed at a cooling rate of 10 to 500 ° C./sec, and the crystal grain size of the main phase has a minor axis of 0.1 to 50 μm.
An alloy for a raw material of a permanent magnet having a major axis of 0.1 to 100 μm is manufactured, and by using this, the residual magnetic flux density (B
r) is increasing. JP-A-7-176414 discloses a method of mixing a columnar crystal main phase master alloy having an average particle size of 3 to 50 μm and a grain boundary auxiliary agent having an average particle size of 0.1 to 20 μm, and absorbing hydrogen by a method of absorbing hydrogen. The properties are improved, and the grindability is also improved. Japanese Patent Application Laid-Open No. 9-170055 discloses that after casting 8
By controlling the cooling at 00 to 600 ° C. to 10 ° C./second or less, an alloy having an average particle diameter of the main phase of 20 to 100 μm and an Nd-rich phase interval of 15 μm or less is produced, and the residual magnetization is increased. Each of these reports is characterized by improving the magnetic properties by obtaining a fine powder having a uniform particle size distribution by using a homogeneous raw material alloy having a uniform average particle size.

[0004] Rare earth permanent magnets are obtained by pulverizing a raw material alloy produced by a die casting method or a quenching method, press-molding a fine powder in a magnetic field, and then sintering in a vacuum. Manufactured in a metallurgical process. The sintering process for rare earth permanent magnets is called liquid phase sintering. Heating a fine powder compact to about 1100 ° C (depending on the composition) increases the amount of liquid phase, shrinks and increases the density. The fact that the residual magnetic flux density is increased is utilized. When cooled after completion of sintering, the R (Nd) -rich phase, which has a low melting point, surrounds the main phase that did not become a liquid phase, and the main phase having an average particle size of 3 to 10 μm is dispersed, thereby increasing coercive force. appear. In order to increase the residual magnetic flux density, it is necessary to increase the sintering density, and it is better to increase the sintering temperature up to the temperature at which the main phase becomes completely liquid.

On the other hand, the coercive force does not mean that the sintering temperature should be increased, but generally becomes maximum at a temperature about 100 ° C. lower than the temperature at which the residual magnetic flux density becomes maximum. In other words, the coercive force is highest when the density of the sintered body is increased to about 90% of the true density, and when the density is further increased, the main phase undergoes grain growth to increase the grain size. Since the dispersibility of the phase decreases, the coercive force decreases. In particular, when heating is performed until the sintered body density exceeds 99.5% of the true density, the main phase rapidly grows and the coercive force decreases sharply, and the squareness also decreases. Therefore, generally, in consideration of the balance between the residual magnetic flux density and the coercive force, the temperature at which the sintered body density becomes 98 to 99.5% of the true density is set as the optimum sintering temperature. From the above, if it is possible to increase the density of the sintered body at a lower temperature than the conventional optimum sintering temperature, the particle size of the main phase in the sintered body will not be increased, so the residual magnetic flux density It is considered that the coercive force can be increased without impairing the value of.

To lower the optimum sintering temperature for the purpose of increasing the coercive force, a method for increasing the R-rich phase, which is a phase that easily becomes a liquid phase and has a low melting point, and a method for reducing the particle size of the fine powder There is a way to make it finer. In the former case, the sintering temperature is lowered and the coercive force is increased, but the ratio of the main phase is relatively reduced, and the residual magnetic flux density is undesirably reduced. In the latter case, the oxygen concentration increases due to an increase in the surface area of the fine powder. Oxygen reacts with R to form R ₂ O ₃ , which is not preferable because the amount of the R-rich phase decreases.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and has been made based on a finding that a raw material suitable for producing a rare earth permanent magnet capable of densifying a sintered body at a low temperature is provided. And a method for producing the raw material.

[0008]

According to the present invention, in order to achieve the object, substantially R ₂ T ₁₄ B (R is a rare earth element, T is a transition element) obtained by quenching a molten alloy by a roll quenching method. (Indicating metal), and the thickness of the ribbon is 3
0 to 1000 μm, and a volume ratio of 1 to 3 near the cooling surface.
0% has a chill crystal with a particle diameter of 3 μm or less, and a portion where α-Fe having an average particle diameter of 3 μm or less is precipitated is 1% by volume.
-10%, the balance being granular crystals with a particle size of 3-50 μm,
And a columnar crystal having a short axis of 3 to 100 μm and a long axis of 20 to 600 μm. The fine alloy powder for permanent magnet raw material is coarsely pulverized, and the coarsely pulverized powder is further finely pulverized. Fine powder having a particle size of 3 μm or less is contained in an amount of 1 to 30 vol%, and the remaining powder is contained. Particle size is substantially 3 to 1
It is assumed to be 0 μm. Further, the alloy ribbon for the raw material of the permanent magnet is coarsely pulverized, mixed with a separately coarsely pulverized auxiliary for grain boundaries, and the mixed coarsely pulverized powder is further finely pulverized, and has a particle size of 3 μm or less. Is contained in an amount of 1 to 30 vol%, and the remainder has a particle size of substantially 3 to 10 μm. In addition, in order to produce an alloy fine powder for a permanent magnet raw material, the alloy ribbon for a permanent magnet raw material is coarsely pulverized and mixed with or not mixed with a separately coarsely pulverized auxiliary for grain boundaries. Smash. The method of coarsely pulverizing the alloy ribbon for the raw material of the permanent magnet is a method of performing dehydrogenation after absorbing hydrogen in the alloy ribbon for the raw material of the permanent magnet, and the fine pulverization is performed by a jet mill. Is preferred.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The present invention relates to a chill crystal, a granular crystal part, a columnar crystal part, and α-
By using an alloy ribbon for a raw material of a permanent magnet having a crystal structure in which Fe precipitated portions are mixed, it is possible to increase the density of the sintered body at a low temperature, and the main phase in the sintered body grows in grains. R with high residual magnetic flux density and high coercive force
-It is based on the knowledge that a TB rare earth permanent magnet can be obtained. According to the roll quenching method, the present inventors have found that α-Fe having a chill crystal having a particle size of 3 μm or less with a volume ratio of 1 to 30% near the cooling surface and having an average particle size of 3 μm or less.
Is a volume fraction of 1 to 10%, the remainder is granular crystals having a particle size of 3 to 50 μm, and a short axis of 3 to 100 μm.
m, an alloy ribbon for a permanent magnet material consisting of columnar crystals having a major axis of 20 to 600 μm can be obtained. Further, by using the alloy ribbon for a permanent magnet material, the average particle size is 3 μm.
The following are contained in an amount of 1 to 30%, and the remaining particle size is 3 to 10:
A fine powder having a particle size distribution of μm and having many low-melting point R-rich and B-rich phases can be easily obtained, and by using the fine powder, a fine powder having a conventional uniform particle size distribution can be obtained. It has been found that sintering can be performed at a lower temperature of 20 to 100 ° C. than in the case where is used, and that the coercive force increases.

[0010] When the coercive force is increased by lowering the optimum sintering temperature by a method of reducing the average particle size of the fine powder, as described above, the oxygen concentration is increased, and thus the magnet is required to have higher characteristics. There was a limit to doing. However, if a fine powder containing fine particles is used without changing the average particle size, the magnet can be improved in characteristics. Specifically, when fine powder having a particle size distribution in which 1 to 30% of particles having a particle size of 3 μm or less are contained and the remaining particle size is 3 to 10 μm is used, fine powder having a particle size of 3 μm or less exists. Therefore, the optimum sintering temperature is lowered by 20 to 100 ° C., and the coercive force is increased. In this case, since the average particle diameters are almost the same, there is almost no increase in the oxygen concentration.

In order to produce a fine powder having a particle size distribution in which 1 to 30% of particles having a particle size of 3 μm or less is contained and the remaining particle size is 3 to 10 μm, a raw material alloy having a uniform crystal structure is used. It is difficult if you have been. The reason is as follows. (1) If a raw material alloy having a uniform crystal structure is used, the pulverized fine powder tends to have a uniform particle size distribution. (2) Particle size 3μ with the same average particle size by changing the pulverization conditions
If an attempt is made to increase the amount of fine powder having a particle size of m or less, a large powder having a particle size of 10 μm or more will be mixed. (3) Fine powder having a particle size of 3 μm or less and an average particle size of 3 to 10 μm
In the method of separately pulverizing and mixing the fine powder with the fine powder, the powder is not completely mixed. Further, since the fine powder is very easily oxidized and the oxygen concentration increases, it is not preferable to add a mixing step using a V blender or the like.

Therefore, in order to produce a fine powder having a particle size distribution in which 1 to 30% of particles having an average particle diameter of 3 μm or less is contained and the remaining particle diameter is 3 to 10 μm, a plurality of phases including chill crystals are required. It suffices to use a raw material alloy having a mixed crystal structure. An alloy for a raw material of a permanent magnet having a crystal structure in which a plurality of phases including a chill crystal are mixed is realized by a ribbon obtained by rapidly cooling a molten alloy by a roll rapid cooling method. The alloy ribbon for a raw material is manufactured by rapidly cooling a molten metal by a single roll method or a twin roll method. When the molten alloy is brought into contact with a roll and cooled and solidified, an alloy ribbon is formed, but the cooling rate in the alloy ribbon is not constant. For example, in the case of the single roll method, the alloy ribbon is sequentially cooled from the roll contact surface to the non-contact surface, but at the same time as the alloy ribbon is cooled, the calorific value moves to the roll, and the temperature of the roll rises. . Therefore, while the alloy ribbon is in contact with the roll, the temperature difference between the alloy ribbon and the roll gradually decreases, and the cooling rate decreases. In other words, the cooling speed of the roll contact surface of the alloy ribbon is high, but the cooling speed of the non-contact surface is low.

The roll is cooled during one rotation after the alloy ribbon is peeled off the roll, and the molten alloy contacts the roll again to produce the alloy ribbon. The cooling rate can be changed by changing the material, thickness, diameter, rotation speed, cooling water temperature, cooling water flow rate, etc. of the roll, thereby producing a raw material alloy having a crystal structure in which multiple phases are mixed. can do. Specifically, about 1000 near the roll contact surface
Chill crystals having a particle size of 3 μm or less are formed at a cooling rate of 0 ° C./sec or more. For the next layer, about 1000 ° C / sec to about 10,000 ° C
At a cooling rate of 1 / sec, a granular crystal having a particle size of 3 to 50 μm is produced. In the next layer, a short axis of 3 to 100 μm and a long axis of 20 to 600 μm at a cooling rate of about 200 ° C./sec to about 1000 ° C./sec.
To make columnar crystals. Next, α-Fe precipitates at a cooling rate of about 200 ° C./second or less. Here, those having a major axis less than twice the minor axis are granular crystals, and those having a major axis more than twice are columnar crystals. The quantitative ratio of the crystal phase in the alloy ribbon is such that α-Fe having a chill crystal with a particle size of 3 μm or less with a volume ratio of 1 to 30% near the cooling surface and an average particle size of 3 μm or less is precipitated. Is 10 to 10% by volume, and the remainder is 3 to 50 μm in particle size.
And the short axis is 3 to 100 μm and the long axis is 20 to
It is made of columnar crystals of 600 μm. In addition, even if there is a substance other than chill crystals, granular crystals, and columnar crystals, there is no problem as long as the volume ratio is 1% or less. If the proportion of chill crystals is less than 1% by volume, the proportion of fine powder having a particle size of 3 μm or less decreases, and the effect of the present invention cannot be obtained. On the other hand, if it exceeds 30%, the proportion of fine powder having a particle diameter of 3 μm or less increases, and the oxygen concentration increases, which is not preferable.

The R-rich phase and the B-rich phase that segregate at the same time as the segregation of α-Fe are low melting points, and have an effect of lowering the optimum sintering temperature. That is, since the R-rich phase and the B-rich phase are easily oxidized phases, they have a negative effect of increasing the oxygen concentration, but also have a positive effect of lowering the optimum sintering temperature. It was found that the positive effect was larger when the volume ratio was 1% to 10%. When the average particle size of α-Fe is 3 μm or less, which is finer than the finely pulverized particle size, α-Fe itself does not need to be pulverized, so that the pulverization ability does not deteriorate. And in this case, α-
Since Fe and the main phase coexist and follow the crystal direction of the coexisting main phase during the sintering step, the degree of orientation does not decrease and the residual magnetization does not decrease. For the above reasons, the average particle size is 3
The segregated portion of α-Fe of μm or less has a volume ratio of 1 to
Preferably, it is 10%.

The obtained alloy ribbon is coarsely pulverized. For the coarse pulverization, ordinary pulverization means such as a brown mill can be employed.
However, in the coarse pulverization step, it is more preferable to carry out hydrogenation coarse pulverization in which hydrogen is occluded and then dehydrogenation is performed instead of coarsely pulverizing the alloy ribbon with a Brown mill or the like. This is because the lattice spacing expands due to hydrogen occlusion, cracks occur, and coarse powder is formed. This is preferable because coarse powder easily breaks at the grain boundaries of the crystal structure during fine pulverization. . In the dehydrogenation step, heating is performed at 400 to 700 ° C. in a vacuum. By heating, sufficient hydrogen is released from the main phase. In the case of the one alloy method, the obtained coarse powder is finely pulverized by a jet mill or the like. Also,
In the case of the two-alloy method, it is mixed with an auxiliary coarse powder for grain boundaries which has been coarsely pulverized by a brown mill or the like, and the mixed coarse powder is finely pulverized by a jet mill or the like.

In the pulverization with a jet mill, the particle size is 3
Chill crystals having a particle size of not more than μm are pulverized into fine powder having a particle size of not more than 3 μm, and the other portions are pulverized into fine powder having a particle size of 3 to 10 μm. The ratio of the fine powder by particle size is such that 1 to 30 vol% of fine powder having a particle size of 3 μm or less is contained, and the particle size of the remaining portion is substantially 3 to 10 μm. When the volume of the fine powder having a particle diameter of 3 μm or less is 1 vol% or less, the temperature of the liquid phase sintering becomes high, and when it exceeds 30 vol%, the oxygen concentration increases and the required magnetic properties cannot be obtained. The obtained fine powder is subjected to pressure molding in a magnetic field for orientation. afterwards,
The molded body is sintered in a vacuum at a temperature lower by 20 to 100 ° C. than when a fine powder prepared by a conventional method is used. The present invention has been described in terms of the ratio when a plurality of crystal structures are present in a ribbon and the effects of the same. In short, even if there are variations in the ribbon including the thickness, etc., the overall volume Α-Fe having a chill crystal with a particle size of 3 μm or less at a rate of 1 to 30% and an average particle size of 3 μm or less
Is a volume fraction of 1 to 10%, the remainder is granular crystals having a particle size of 3 to 50 μm, and a short axis of 3 to 100 μm.
m and a columnar crystal having a major axis of 20 to 600 μm. This means that the production conditions of the ribbon are wide, and it is very preferable to use the alloy ribbon of the present invention in order to continue production stably.

[0017]

The present invention will be described below with reference to examples.
The present invention is not limited to these. [Example 1] Composition formula 12.5Nd-6.0B-1.5C
A metal melt having a composition of o-80.0Fe (atomic%)
The alloy ribbon was manufactured by cooling in a single roll method in an r atmosphere. The average thickness of the entire alloy ribbon is about 280.
11% of chill crystals near the cooling surface, and 35% of granular crystals having a particle size of 5 to 30 μm, and 48% of columnar crystals having a minor axis of 5 to 40 μm and a major axis of 50 to 260 μm. Average particle size of 6% by volume on the uncooled surface side
8 μm consisted of a segregated portion of α-Fe.
FIG. 1 shows a structure photograph of a cross section of the alloy ribbon by a typical polarizing microscope. The lower part of the cross-sectional photograph is the roll contact surface, where chill crystals are formed. FIG. 2 is an enlarged backscattered electron composition image of a portion surrounded by a square at the upper left of FIG. 1 where the crystal size is not well understood by the polarizing microscope, and α-Fe is a black portion. 20. The manufactured alloy ribbon was coarsely pulverized by a Brown mill to an average particle diameter of 200 μm to obtain a main phase master alloy, and 90% by weight of the alloy alloy was separately coarsely pulverized to an average particle diameter of 200 μm by a Brown mill.
0Nd-10.0Dy-6.0B-44.0Co-2
10 wt% of a grain boundary auxiliary having a composition of 0.0Fe (each atomic%) was mixed, and then finely pulverized by a jet mill.

The resulting fine powder had an average particle size of 4.5 μm, of which 8% had a particle size of 3 μm or less, and the average particle size was 1.9 μm. FIG. 3 shows the particle size distribution of this fine powder. Another peak is seen below 3 μm. The obtained fine powder was molded under pressure at a pressure of 1 ton / cm ² while being oriented in a magnetic field of 15 kOe. This molded body was sintered at 1040 ° C. for 2 hours in vacuum,
An aging heat treatment was performed for 1 hour in an r atmosphere to produce a magnet alloy.

Example 2 The same alloy ribbon as in Example 1 was roughly pulverized by hydrogenation coarse pulverization. In the hydrogenation coarse pulverization, a hydrogen storage treatment is performed at room temperature for 2 hours, and then 600
The mixture was heated at 2 ° C. for 2 hours to perform a dehydrogenation treatment. Thereafter, a fine powder was obtained in the same manner as in Example 1. The average particle size of the obtained fine powder was 4.5 μm, of which 12% had a particle size of 3 μm or less, and the average particle size was 1.5 μm.
FIG. 4 shows the particle size distribution of this fine powder. Another peak, seen below 3 μm, was higher. Using this fine powder, the sintering temperature was 103 ° C. lower than that of Example 1;
A magnet alloy was produced in the same manner as in Example 1 except that the temperature was set to 0 ° C. This 1030 ° C. is the optimum sintering temperature for the fine powder used in this example.

[Comparative Example 1] A granular crystal having the same composition as in Example 1 and having an average thickness of about 270 µm and a volume ratio of 4% and a particle size of 5 to 35 µm near the cooling surface by a single roll method,
An alloy ribbon for a raw material was manufactured, the remainder of which was composed of columnar crystals having a short axis of 5 to 35 μm and a long axis of 50 to 270 μm. Thereafter, a magnet alloy was produced in the same manner as in Example 2, except that the sintering temperature was set to 1080 ° C., which is the optimum sintering temperature of this alloy, which was 50 ° C. higher than that of Example 2. The average particle size of the fine powder obtained on the way is 4.6 μm, of which 2
%, And the average particle size was 2.6 μm. FIG. 5 shows the particle size distribution of this fine powder. No peak is observed below 3 μm.

[Comparative Example 2] The same sintering temperature as in Example 2 was used.
A magnet alloy was produced in the same manner using the same alloy ribbon as in Comparative Example 1 except that the temperature was 030 ° C. Comparative Example 3 An alloy ribbon for a main phase was manufactured by the single roll method using the same composition as in Example 1. The obtained alloy ribbon has an average thickness of about 300 μm and a volume ratio of 1 near the cooling surface.
0% chill crystals, then 15% granular crystals with a particle size of 5-40 μm, then 52% short axes 5-40 μm, long axis 6
0 to 280 μm columnar crystal, 23 by volume ratio on the uncooled surface side
% Of 2.1-μm α-Fe segregated. Thereafter, a magnet alloy was produced in the same manner as in Example 2 except that the sintering temperature was set to 1050 ° C., which is 20 ° C. higher than that in Example 2, which is the optimum sintering temperature when this alloy ribbon was used. The average particle size of the fine powder obtained in the middle was 4.5 μm, of which 13% had a particle size of 3 μm or less, and the average particle size was 1.5 μm.

Comparative Example 4 An alloy ribbon for a main phase was manufactured by the single roll method using the same composition as in Example 1. The obtained alloy ribbon has an average thickness of about 1000 μm, a granular crystal having a particle size of 5 to 40 μm with a volume ratio of 6% near the cooling surface, and a short axis of 5 to 45 μm and a major axis of 200 to 64%. 7. 700 μm columnar crystal, average particle size of 30% by volume on the uncooled surface side
The alloy ribbon was composed of a portion where 2 μm α-Fe was segregated. Thereafter, the sintering temperature was 70 ° C. higher than that in Example 2, which is the optimum sintering temperature when this alloy ribbon was used.
A magnet alloy was produced in the same manner as in Example 2 except that the temperature was changed to 100 ° C. The average particle size of the fine powder obtained during the process is 5.5 μm.
1% of which have a particle size of 3 μm or less, and the average particle size is 2.8%.

Table 1 shows the thickness of the alloy ribbon, the crystal structure and its ratio, the presence or absence of hydrogenation coarse pulverization, and the fine powder for Examples 1 and 2 and Comparative Examples 1 to 4 in which magnets were produced by the two-alloy method. Average particle size and a ratio of 3 μm or less, the sintering temperature of the obtained magnet alloy,
The average particle size of the main phase, magnetic properties (residual magnetic flux density Br, coercive force iHc, maximum energy product (BH) max), and sintered density ρ are shown.

[0024]

[Table 1]

In Comparative Example 1 using an alloy ribbon in which neither chill crystals nor α-Fe having an average particle size of 3 μm or less exist, it is necessary to sinter at 1080 ° C. in order to sufficiently increase the density of the sintered body. there were. On the other hand, in Examples 1 and 2 where chill crystals exist, the density of the sintered body was sufficiently increased at 1040 ° C. and 1030 ° C., respectively. The iHc is high because the phases do not grow and the average particle size is kept small. Further, in Example 2 in which the hydrogenation coarse pulverization was performed, the proportion of the fine powder having a particle size of 3 μm or less was larger than that in Example 1, and the optimum sintering temperature was further lowered. More desirable results were obtained. Comparative Example 2 was the same method as in Example 2 except that the same alloy ribbon was used as in Comparative Example 1 and the sintering temperature was the same as in Example 2.
However, the result is that the density of the sintered body is low and Br and (BH) max are low.

Comparative Example 3 is a case of an alloy ribbon having a chill crystal and a segregated portion of α-Fe having an average particle size of 2.1 μm and having a volume fraction of 23%. In this case, the amount of particles having a particle size of 3 μm or less in the fine powder increases, and the average particle size decreases, so that the oxygen concentration in the sintered body increases, and
The amount of d ₂ O ₃ increases, the amount of the R-rich phase decreases, and iHc decreases. In Comparative Example 4, a portion where α-Fe having an average particle size of 8.2 μm was segregated was 3% by volume.
This is the case of a 0% alloy ribbon. In this case, not only does the oxygen concentration increase, but also the α of the average particle size of 8.2 μm.
The presence of -Fe deteriorates the pulverizability and increases the average particle size of the fine powder, resulting in lower iHc. From the above, it has a chill crystal and an average particle size of 3 μm.
m or less of the precipitated α-Fe is 1 to 1 by volume ratio.
To produce a magnet alloy using 0% alloy ribbon,
It can be seen that this is effective for improving the magnetic characteristics.

Next, the composition formula 13.2Nd-0.8Dy-
Examples 3 to 4 and Comparative Examples 5 to 8 were produced by using the alloy of 6.0B-4.5Co-75.5Fe (each atomic%) and producing a magnet alloy by a one-alloy method. And Comparative Example 5
Table 2 shows the measurement results of items similar to Table 1 for
Shown in The production method using the one-alloy method is the same as the two-alloy method except that no auxiliary material for grain boundaries is mixed.

[0028]

[Table 2]

It has chill crystals of 8% by volume and has an average particle size of 3%.
The portion where α-Fe of μm or less is precipitated is 4% by volume.
The magnetic properties of Examples 3 and 4 using a certain alloy ribbon are high, and even in the case of the one-alloy method, a portion having a chill crystal and having α-Fe having an average grain size of 3 μm or less is deposited. It has been shown that manufacturing a magnet alloy using an alloy ribbon having a volume ratio of 1 to 10% is effective for improving magnetic properties.

[0030]

As described above, when a magnetic alloy is manufactured using the fine powder of the present invention, the sintering temperature can be reduced without impairing the residual magnetic flux density Br and the maximum energy product (BH) max. The coercive force iHc can be increased. Also,
By using the alloy ribbon of the present invention, the ratio of the fine powder having a particle size of 3 μm or less can be increased without changing the average particle size. Also, an alloy ribbon having a plurality of phases is produced more than an alloy ribbon having a uniform crystal grain size over the entire area between the cooling surface (roll contact surface) and the non-cooling surface (roll non-contact surface). Since the conditions are wide, it is easy to continue the production stably, and it is very preferable to use the alloy ribbon of the present invention.

[Brief description of the drawings]

FIG. 1 is a micrograph of a structure of a thin alloy ribbon in Example 1 taken by a polarizing microscope.

FIG. 2 is a tissue photograph in which an upper left square portion of FIG. 2 is enlarged.

FIG. 3 is a graph showing the particle size distribution of fine powder in Example 1.

FIG. 4 is a graph showing the particle size distribution of fine powder in Example 2.

FIG. 5 is a graph showing a particle size distribution of a fine powder in Comparative Example 1.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichi Hirota 2-5-1-5 Kitafu, Takefu City, Fukui Prefecture Inside the Magnetic Materials Research Laboratory, Shin-Etsu Chemical Co., Ltd. (72) Inventor Takehisa Minowa 2-1-1 Kitafu, Takefu City, Fukui Prefecture No.5 Shin-Etsu Kagaku Kogyo Co., Ltd. Magnetic Materials Laboratory F-term (reference) 4E004 DB02 TA02 TA03 4K017 AA04 BA06 BB06 BB12 CA07 DA04 EA03 EA08 EC02 5E040 AA04 BD01 CA01 HB17 NN06 NN17

Claims (5)

[Claims] 1. A thin strip substantially composed of R ₂ T ₁₄ B (R is a rare earth element and T is a transition metal) obtained by quenching a molten alloy by a roll quenching method. Saga 3
0 to 1000 μm, and a volume ratio of 1 to 3 near the cooling surface.
0% has a chill crystal with a particle diameter of 3 μm or less, and a portion where α-Fe having an average particle diameter of 3 μm or less is precipitated is 1% by volume.
-10%, the balance being granular crystals with a particle size of 3-50 μm,
An alloy ribbon for a raw material of a permanent magnet, comprising a columnar crystal having a short axis of 3 to 100 µm and a long axis of 20 to 600 µm. 2. A fine powder obtained by coarsely pulverizing the alloy ribbon for a permanent magnet raw material according to claim 1 and further finely pulverizing the coarsely pulverized powder, wherein the fine powder having a particle size of 3 μm or less is 1 to 3. 30v
%, and the remaining particle size is substantially 3 to 10 μm. 3. A fine powder obtained by coarsely pulverizing the alloy ribbon for raw material of a permanent magnet according to claim 1, mixing with a coarsely pulverized auxiliary for grain boundary, and further finely pulverizing the mixed coarsely pulverized powder. An alloy fine powder for use as a raw material for permanent magnets, characterized in that 1 to 30 vol% of fine powder having a particle size of 3 μm or less is contained and the remaining particle size is substantially 3 to 10 μm. 4. The method according to claim 1, wherein the alloy ribbon for raw material of a permanent magnet according to claim 1 is coarsely pulverized, and the coarsely pulverized powder is further finely pulverized without mixing or mixing with a coarsely pulverized auxiliary for grain boundaries. The method for producing an alloy fine powder for a raw material of a permanent magnet according to claim 2 or 3. 5. The method according to claim 4, wherein the method of coarsely pulverizing the alloy ribbon for a raw material of permanent magnet is a method of performing dehydrogenation after absorbing hydrogen in the alloy ribbon for a raw material of permanent magnet. A method for producing an alloy fine powder for a raw material of a permanent magnet, wherein the fine pulverization is performed by a jet mill.