JPH0734206A - Rare earth magnet and method and device for manufacturing it - Google Patents

Abstract

PURPOSE:To prepare a powder having high crystal orientational property by controlling crystal growth at the time of ingot casting and uniformizing the direction of crystals in an ingot and to produce a rare earth magnet having high magnetic properties and also to provide the method and device for manufacturing it. CONSTITUTION:In a rare earth magnetic alloy manufacturing process, a molten alloy is cast in a mold 1 where, among the planes to be in contact with the molten alloy, the base 6 has a recessed shape, by which the specific crystal axes of respective crystals in the alloy are aligned in the prescribed direction. Moreover, in a rare earth magnetic alloy manufacturing process, a molten alloy is cast in the mold 1 where, among the planes to be in contact with the molten alloy, the base 6 has a recessed shape and which is constituted of at least two parts consisting of a part to be cooled down to <=500 deg.C and a part to be heated up to 600-1300 deg.C, by which the specific crystal axes of alloy crystals are oriented in a direction parallel to the base of the mold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rare earth magnet alloy and a sintered permanent magnet and a plastic permanent magnet produced by using the rare earth magnet alloy.

[0002]

2. Description of the Related Art Permanent magnets are used in a wide range of fields from various electric products to small precision instruments and actuators, and they are one of the important electric and electronic materials. In recent years, there has been a demand for permanent magnets with high characteristics in order to reduce the size and increase the efficiency of equipment. In response to these demands, the demand for rare-earth permanent magnets, which are permanent magnets with high characteristics, has become extremely high. Generally, a method of manufacturing an R—Co anisotropic plastic magnet (where R is a rare earth element), which is a kind of rare earth permanent magnet, is performed as follows. First,
An alloy ingot is obtained by injecting a molten alloy composition into a mold. After heat treatment, the ingot is crushed into powder and mixed with an epoxy binder. And
This mixed powder is subjected to compression molding or extrusion molding while being magnetically oriented in a magnetic field to form a molded body, which is then subjected to a curing treatment depending on the type of epoxy binder and finally coated to obtain a product.

[0003]

In the manufacturing process of the above-mentioned plastic magnet, the characteristics of the powder obtained by crushing the ingot become a factor that greatly affects the characteristics of the product.
In conventional ingot casting, the crystal growth during solidification of the melt cannot be controlled, and the orientation of each crystal in the ingot becomes random. Therefore, even if the ingot is crushed into a powder state, the crystal orientation is low, and the magnetic field orientation of the powder is also low, so that only a permanent magnet having low magnet characteristics can be obtained.

Further, a method of manufacturing a sintered rare earth magnet is as follows.
A molten alloy having an alloy composition is poured into a mold to obtain an alloy ingot. Next, the ingot is crushed into powder, and this powder is compression-molded while being oriented in a magnetic field. Then, the green compact is sintered, and then the sintered body is subjected to heat treatment, and further processed such as processing and painting to obtain a product. In the case of sintered rare earth magnets as well as in the case of plastic magnets, the low crystal orientation in the ingot caused a decrease in the magnetic field orientation of the powder, resulting in a decrease in magnet characteristics. .

Therefore, in order to eliminate these defects, the technical problem of the present invention is to control the growth of crystals during ingot casting and align the directions of the crystals in the ingot to obtain a powder having a high crystal orientation. An object of the present invention is to provide a method of manufacturing a rare earth magnet having high magnet characteristics, and a manufacturing apparatus thereof.

[0006]

According to the present invention, there is provided a rare earth magnet alloy ingot which is elongated in one axis direction and has a shape in which one side surface along the one axis direction forms a convex curve outward in a cross section. Thus, a rare earth magnet alloy is obtained in which the specific crystal axes of crystal grains are oriented in a direction parallel to the uniaxial direction.

According to the present invention, in the rare earth magnet alloy, the Sm-Co alloy and the R ₂ T ₁₄ B magnet alloy (wherein R is a rare earth element (including Y)) and T is Fe as a main component. A rare earth magnet alloy characterized by comprising at least one of the following transition metal elements).

According to the present invention, there is obtained a sintered rare earth magnet characterized by using a pulverized powder of any one of the above rare earth magnet alloys as a raw material.

According to the present invention, there is provided a method for producing a sintered rare earth magnet, characterized in that any one of the above rare earth magnet alloys is pulverized and produced by powder metallurgy.

According to the present invention, there is obtained a polymer composite type rare earth magnet characterized by using a pulverized powder of any one of the above rare earth magnet alloys as a raw material.

According to the present invention, there is provided a method for producing a rare earth composite magnet, characterized in that any one of the rare earth magnet alloys described above is crushed, mixed with a resin and compression-molded.

According to the present invention, there is provided a pair of side faces facing each other for casting the molten alloy, a pair of end faces connecting both end sides of the pair of side faces, and a bottom face, and each of these faces. A rare earth magnet alloy for casting a molten alloy into a specified space, characterized in that the contour of the bottom surface of the cross section of the space is a downwardly convex curve. Can be obtained.

According to the present invention, the apparatus for producing a rare earth magnet alloy is provided with a cooling device for cooling the bottom of the mold and a heater for heating the upper part above the bottom. An apparatus for producing a characteristic rare earth magnet alloy is obtained.

According to the present invention, in any one of the rare earth magnet alloy manufacturing apparatuses, the rare earth magnet alloy is S
It is characterized by comprising at least one of an m-Co alloy and an R ₂ T ₁₄ B magnet alloy (where R is a rare earth element (including Y) and T is a transition metal element containing Fe as a main component). An apparatus for producing a rare earth magnet alloy is obtained.

According to the present invention, the molten alloy is cast into a mold having a concave bottom surface in the contact surface with the molten alloy in which the rare earth magnet alloy is melted, whereby the specific crystal axis of the crystal grains of the alloy is cast. Is orientated in a direction parallel to the bottom surface, thereby obtaining a method for producing a rare earth magnet alloy.

According to the present invention, in the method for producing a rare earth magnet alloy, one of the two vertical parts of the mold is cooled to 500 ° C. or less, and
A method for producing a rare earth magnet alloy is obtained, in which the other of the two parts is heated to 600 to 1300 ° C. or lower and the molten alloy is cast into the mold.

According to the present invention, in any one of the methods for producing a rare earth magnet alloy, the rare earth magnet alloy is S
It is characterized by comprising at least one of an m-Co alloy and an R ₂ T ₁₄ B magnet alloy (where R is a rare earth element (including Y) and T is a transition metal element containing Fe as a main component). A method for producing a rare earth magnet alloy is obtained.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing a mold for producing a rare earth magnet alloy according to an embodiment of the present invention. As shown in FIG. 1, the mold 1 is made of Cu and has a pair of side faces 2, 3, a pair of end faces 4, 5 connecting these end portions to each other, and a bottom face 6 which is a bottom part, and casts a molten alloy. A space 7 is formed. The bottom surface 6 forms an inner cylindrical surface which is a curved line with a downward convex in the cross section.

FIG. 2A is a perspective view showing a mold for manufacturing a rare earth magnet alloy according to another embodiment of the present invention, FIG.
2B is a sectional view taken along the line AA ′ of FIG. Figure 2
As shown in (a) and (b), the mold 10 includes a mold body 13 having a mold upper portion 11 and a mold lower portion 12, and a heater 14 provided around the mold body 13.
The mold body 13 has a pair of side surfaces 15a, 1 facing each other.
5b, a space 15 defined by a pair of end faces 15c and 15d connecting the both ends of the side faces 15a and 15b, respectively, and a bottom face 15f is provided.

The lower part 12 of the mold including the bottom surface 15f is provided with a cooling water passage 16. The bottom surface 15f forms an inner cylindrical surface that is convex downward.

Next, the action generated by the mold shown in FIGS. 1 and 2 will be described.

From the viewpoint of the crystal structure of the main phase, the rare earth magnet alloys currently in practical use have a 1-5 system,
It is classified into 3 types, 2-17 series and 2-14-1 series.
Each crystal has uniaxial anisotropy in the C-axis direction, and the preferential direction of crystal growth during solidification is the C-plane direction. However, Figure 3
As shown in (b), the easy magnetization direction is the C-axis direction 21,
Even if the C-plane direction 22, which is the crystal growth direction, is simply aligned, the C-axis direction 21, which is the easy magnetization direction, can take various directions.

However, according to the mold of the rare earth magnet alloy according to the embodiment of the present invention shown in FIGS. 1 and 2, when crystal growth starts from the concave portion (bottom surface 6, bottom surface 15f), the concave shape Therefore, adjacent crystal grains grow while interfering their growth directions with each other. As shown in FIG.
1 also faces the same direction. That is, the directions of the respective crystals in the ingot are aligned, and it is possible to obtain a powder having a high crystal orientation by crushing the crystals. In the figure, reference numeral 23 is a crystal growth direction.

Next, the present invention will be described in more detail with reference to specific manufacturing examples.

Example 1 As an Sm ₂ Co ₁₇ type alloy,
23.5 wt% Sm-14.0 wt% Fe-4.5 wt
% Cu-2.5wt% Zr-balCo alloying elements are weighed, high-frequency melted in an Ar atmosphere, and the melted alloy is cast into a mold 1 as shown in FIG. 1 through a tundish. An alloy ingot having a thickness of 20 mm and a length of 150 mm was produced. The mold 1 is made of copper, and has a concave recess (bottom surface 6) whose bottom cross-sectional contour forms an arc.

Next, the ingot is 118 in Ar atmosphere.
Solution treatment was performed at 0 ° C. for 15 hours. Then, as an aging treatment, the temperature was held at 800 ° C. for 2 hours, and then the temperature was lowered from 800 ° C. at a cooling rate of −1 ° C./min. The ingot was crushed to a powder particle size of 500 μm or less using a disc mill. Next, a thermosetting epoxy resin as a binder was mixed with the powder in a weight ratio of powder 97 to epoxy resin 3, and then compression molded at a pressure of 5 ton / cm ^{2 in} a magnetic field of 20 kOe. The molded body was kept at 80 ° C. for 5 hours to harden the binder to obtain a plastic magnet. The results of measuring the magnet characteristics with a BH tracer are shown in Table 1 below. Further, as Comparative Example 1, a mold made of copper and having a flat bottom surface was used as the mold, and the magnetic properties of the plastic magnet manufactured under the same conditions as in Example 1 were also shown in Table 1 below.

[0028]

[Table 1]

From Table 1 above, it can be seen that the magnet characteristics of the R—Co anisotropic plastic magnet are improved by using the ingot produced by using the mold 1 having the concave recess on the bottom surface.

Example 2 As an Sm ₂ Co ₁₇ type alloy,
25.5 wt% Sm-14.0 wt% Fe-4.5 wt
% Cu-2.5 wt% Zr-balCo alloying elements are weighed and then high-frequency melted in an Ar atmosphere, and the molten alloy is cast into the same mold 1 as in Example 1 through a tundish. , Thickness 20mm, length 150mm
An alloy ingot of was produced. Next, the ingot was coarsely crushed to a size of 500 μm or less using a disc mill, and then the powder was jet milled to have an average particle size of 3 μm.
Finely crushed. This pulverized powder was molded in a magnetic field of 20 kOe in a direction perpendicular to the magnetic field at a pressure of 1.5 ton / cm ² . Next, this green compact was sintered in vacuum at 1210 ° C. for 30 minutes, then solution-treated at 1200 ° C. for 1 hour in an Ar atmosphere, and then rapidly cooled to room temperature. Subsequently, as an aging treatment, this sintered body was held at 800 ° C. for 2 hours, cooled from 800 ° C. to 400 ° C. at a cooling rate of 1 ° C./minute, and then rapidly cooled to obtain a sintered magnet. The results of measuring the magnetization characteristics with a BH tracer are shown in Table 2 below. Further, as Comparative Example 2, a mold having a flat bottom surface made of copper was used, and the magnet characteristics of a sintered magnet produced under the same conditions as in Example 2 are also shown in Table 2 below.

[0031]

[Table 2]

From Table 2 above, the bottom surface has a concave shape (see FIG. 1).
It can be understood that the magnet characteristics of the R—Co based sintered magnet are improved by using the ingot produced by using the mold 1 having the bottom surface 6) of FIG.

Example 3 As an Nd ₂ Fe ₁₄ B type alloy, 33.4 wt% Nd-65.5et% Fe-1.1
After weighing each element so that the alloy composition is wt% B, Ar
High-frequency melting in an atmosphere, and the same mold 1 as in Example 1
Then, the molten alloy is cast through the tender to a thickness of 2
An alloy ingot having a length of 0 mm and a length of 150 mm was produced.
Next, the ingot is 500μ using a disc mill.
The powder was coarsely pulverized to a particle size of not more than m, and then the powder was finely pulverized with a ball mill to an average particle size of 2.4 μm. This finely pulverized powder was applied in a magnetic field of 20 kOe in the direction perpendicular to the magnetic field for 1.5
It was molded at a pressure of ton / cm ² . Next, the green compact 10
Sintered in vacuum at 80 ° C. for 2 hours. Then at 630 ℃ 1
Heat treatment was applied for a period of time to obtain a sintered magnet. The results of measuring the magnet characteristics with a BH tracer are shown in Table 3 below. In addition, as Comparative Example 3, a magnet characteristic of a sintered magnet manufactured under the same conditions as in Example 3 except that a mold made of copper and having a flat bottom surface was used is also shown in Table 3 below.

[0034]

[Table 3]

From Table 3 above, the bottom surface has a concave shape (see FIG. 1).
It can be seen that the magnet characteristics of the Nd-Fe-B system sintered magnet are improved by using the ingot produced by using the mold 1 having the bottom surface 6).

Example 4 As an Sm ₂ Co ₁₇ type alloy,
23.5 wt% Sm-14.0 wt% Fe-4.5 wt
% Cu-2.5 wt% Zr-balCo, each element is weighed and then high-frequency melted in an Ar atmosphere, and the molten alloy is put into a mold 10 as shown in FIG. 2 through a tundish. Casting, thickness 9mm, length 120mm
An alloy ingot of was produced. The lower part 11 of the mold is made of copper with a water-cooling mechanism having a water-cooling channel 13 and has a temperature of 150 ° C.
It has been cooled to ˜200 ° C., and as shown in FIGS. 2 (a) and 2 (b), it has a concave recess (bottom surface 15f) whose cross section forms an arc. The upper part 12 of the mold is made of copper and is heated to 700 ° C. to 800 ° C. by the heater 15.

Next, the ingot is 118 in Ar atmosphere.
Solution treatment was performed at 0 ° C. for 15 hours. Then, as an aging treatment, the temperature was kept at 800 ° C. for 2 hours, and then the temperature was lowered from 800 ° C. at a cooling rate of 1 ° C./min. The ingot was crushed to a powder particle size of 500 μm or less using a disc mill. Then, the powder was mixed with a thermosetting epoxy resin as a binder in a weight ratio of powder 97: epoxy resin 3 and then 20 k
Compression molding was performed in a magnetic field of Oe at a pressure of 5 ton / cm ² . The molded body was kept at 80 ° C. for 5 hours to harden the binder to obtain a plastic magnet. The results of measuring the magnet characteristics with a BH tracer are shown in Table 4 below. In Comparative Example 4, the mold is made of copper, the bottom surface is flat, and the lower part of the mold is equipped with a water cooling mechanism, but the upper part of the mold is an unheated mold. The magnetic properties of the plastic magnet manufactured in Step 1 are also shown in Table 4 below.

[0038]

[Table 4]

From Table 4 above, it was prepared by using the mold 10 shown in FIG. 2 in which the bottom surface has a concave depression (15f in FIG. 2), the lower mold portion 12 is water-cooled, and the upper mold portion 11 is heated. It can be seen that the magnet characteristics of the R-Co anisotropic plastic magnet are improved by using the ingot.

Example 5 As an Sm ₂ Co ₁₇ type alloy,
25.5 wt% Sm-14.0 wt% Fe-4.5 wt
% Cu-2.5 wt% Zr-balCo alloying elements were weighed and then high-frequency melted in an Ar atmosphere, and the molten alloy was cast into the same mold 10 as in Example 4 through a tundish, An alloy ingot having a thickness of 9 mm and a length of 120 mm was produced. Next, the ingot was coarsely pulverized to a size of 500 μm or less using a disc mill, and then the powder was finely pulverized to an average particle size of 3 μm using a jet mill. This pulverized powder was molded in a magnetic field of 20 kOe in a direction perpendicular to the magnetic field at a pressure of 1.5 ton / cm ² . Then the green compact was sintered in vacuum at 1210 ° C for 30 minutes,
After that, after solution treatment at 1200 ° C. for 1 hour in an Ar atmosphere, it was rapidly cooled to room temperature. Subsequently, as an aging treatment, the sintered body was held at 800 ° C. for 2 hours, cooled from 800 ° C. to 400 ° C. at a cooling rate of 1 ° C./minute, and then rapidly cooled to obtain a sintered magnet. The results of measuring the magnet characteristics with a BH tracer are shown in Table 5 below. As Comparative Example 5, a copper mold was used, the bottom surface was flat, the lower part of the mold was equipped with a water-cooling mechanism, and the upper part of the mold was an unheated mold. The magnet characteristics of the sintered magnet are also shown in Table 5 below.

[0041]

[Table 5]

From Table 5 above, a concave recess (see FIG. 2) is formed on the bottom.
It is possible to improve the magnet characteristics of the R-Co based sintered magnet by using an ingot manufactured by using the mold 10 having the bottom surface 15f) of the mold, the mold lower part 12 being water cooled and the mold upper part 11 being heated. Recognize.

Example 6 As an Nd ₂ Fe ₁₄ B-based alloy, 33.4 wt% Nd-65.5et% Fe-1.1
After weighing each element so that the alloy composition is wt% B, Ar
High-frequency melting in an atmosphere, and the same mold 10 as in Example 4
Molten alloy is cast into the tundish and the thickness is 9m
An alloy ingot having a length of m and a length of 120 mm was produced. Next, the ingot was coarsely pulverized to 500 μm or less using a disc mill, and then the powder was finely pulverized to an average particle size of 2.4 μm using a ball mill. 20 of this finely ground powder
1.5 t / c in the direction perpendicular to the magnetic field of kOe
Molded at a pressure of m ² . Next, this green compact was sintered in vacuum at 1080 ° C. for 2 hours. After that, heat treatment was performed at 630 ° C. for 2 hours to obtain a sintered magnet. The results of measuring the magnet characteristics with a BH tracer are shown in Table 6 below. Further, as Comparative Example 6, a mold made of copper and having a flat bottom surface and a water cooling mechanism at the lower part of the mold but not heated at the upper part of the mold was used. The magnetic properties of the binder magnet are also shown in Table 6 below.

[0044]

[Table 6]

From Table 6 above, a concave recess (see FIG.
The magnet characteristics of the Nd-Fe-B system sintered magnet are improved by using the ingot produced by using the mold 10 having the bottom surface 15f) of the mold, the mold lower part 12 being water cooled and the mold upper part 11 being heated. I understand things.

In each of the above-mentioned embodiments, an alloy having one composition has been described, but the same applies to alloys in which a certain amount of each alloy component is changed or alloys containing a few elements are added. Needless to say, those skilled in the art can easily estimate that the above effect is obtained.

[0047]

As described above, according to the present invention, it is possible to provide a rare earth magnet alloy capable of producing a rare earth magnet having high characteristics, whereby a sintered type or polymer composite having high characteristics can be provided. It has become possible to provide type rare earth magnets.

[Brief description of drawings]

FIG. 1 is a view showing a mold used for producing a rare earth magnet alloy according to an example of the present invention.

FIG. 2 is a view showing a mold and a heating device used for manufacturing a rare earth magnet alloy according to another embodiment of the present invention.

3A and 3B are diagrams showing a relationship between a crystal growth direction and a crystal orientation, FIG. 3A showing the present invention, and FIG. 3B showing a general case of unidirectional solidification.

[Explanation of symbols]

 1 Mold 2, 3 Sides 4, 5 End Face 6 Bottom 7 Space 10 Mold 11 Mold Upper 12 Mold Lower 13 Mold Main Body 14 Heater 15 Space 16 Cooling Water Flow Channel 21 C-axis Direction 22 C-Plane Direction 23 Crystal Growth Direction

Claims (12)

[Claims] 1. An ingot of a rare earth magnet alloy, which is elongated in a uniaxial direction and has a shape in which one side surface forms a convex curve outward in a cross section along the uniaxial direction, wherein a specific crystal axis of a crystal grain is A rare earth magnet alloy characterized by being oriented in a direction parallel to the uniaxial direction. 2. The rare earth magnet alloy according to claim 1, wherein the Sm—Co alloy and the R ₂ T ₁₄ B magnet alloy (wherein R is a rare earth element (including Y)) and T is Fe as a main component. Transition metal element), which is a rare earth magnet alloy. 3. A sintered rare earth magnet, characterized by using the pulverized powder of the rare earth magnet alloy according to claim 1 as a raw material. 4. A method for producing a sintered rare earth magnet, which comprises pulverizing the rare earth magnet alloy according to claim 1 or 2 and producing the alloy by powder metallurgy. 5. A polymer composite type rare earth magnet, which is made of the pulverized powder of the rare earth magnet alloy according to claim 1 or 2. 6. A method for producing a rare earth composite magnet, which comprises crushing the rare earth magnet alloy according to claim 1 or 2 and mixing with a resin to perform compression molding. 7. A space defined by a pair of side surfaces facing each other for casting a molten alloy, a pair of end surfaces connecting both end sides of the pair of side surfaces, and a bottom surface, and defined by each of these surfaces. 1. A rare earth magnet alloy manufacturing apparatus, which is a mold for casting a molten alloy therein, wherein a bottom surface of a cross section of the space has a contour that is convex downward. 8. The apparatus for producing a rare earth magnet alloy according to claim 7, further comprising a cooling device for cooling the bottom portion of the mold, and a heater for heating an upper portion above the bottom portion. Characteristic rare earth magnet alloy manufacturing equipment. 9. The apparatus for producing a rare earth magnet alloy according to claim 7, wherein the rare earth magnet alloy is Sm—Co.
Rare earths characterized by comprising at least one of a group alloy and an R ₂ T ₁₄ B system magnet alloy (where R is a rare earth element (including Y) and T is a transition metal element containing Fe as a main component). Magnet alloy manufacturing equipment. 10. The molten alloy is cast into a mold having a concave bottom surface in the contact surface with the molten alloy in which the rare earth magnet alloy is melted, whereby specific crystal axes of crystal grains of the alloy are A method for producing a rare earth magnet alloy, which comprises orienting in a parallel direction. 11. The method for producing a rare earth magnet alloy according to claim 10, wherein one of the two vertical parts of the mold is cooled to 500 ° C. or less,
A method for producing a rare earth magnet alloy, characterized in that the other of the two parts is heated to 600 to 1300 ° C. or less and a molten alloy is cast into the mold. 12. The method for producing a rare earth magnet alloy according to claim 10, wherein the rare earth magnet alloy is Sm.
-Co alloy and R ₂ T ₁₄ B magnet alloy (Here, R includes a rare earth element (Y), T is a transition metal element as a main component Fe) and characterized in that it consists of at least one of A method for producing a rare earth magnet alloy.