JP2002266006A - Method for controlling structure of rare-earth- containing alloy, and powder of the alloy and magnet using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the internal structure of a rare-earth-containing alloy obtained by a rotating roll method, particularly the state of distribution of R-enriched phases. SOLUTION: Melt of the molten rare-earth-containing alloy is allowed to flow onto a rotating roll to undergo solidification into a ribbon. The ribbon is ground into flakes, and the resultant alloy flakes are subjected to the control of cooling rate by a cooling medium in a storage vessel in a chamber identical with the chamber for the rotating roll. The alloy after the control of its structure is pulverized, and the resultant alloy powder is compacted and sintered into a magnet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for controlling the internal structure of a rare earth element-containing alloy, particularly a rare earth element-containing alloy for a magnet, the alloy powder obtained by the method, and a magnet using the alloy powder.

[0002]

2. Description of the Related Art Recently, Nd-Fe-B has been used as an alloy for magnets.
-Based alloys are rapidly increasing production from their high properties,
For HD (hard disk), MRI (Magnetic Resonance Imaging)
Or for various motors. Usually, a part of Nd is replaced by another rare earth element such as Pr or Dy (denoted as R), and a part of Fe is Co, N
Those which are substituted with another transition element such as i (denoted by T) are generally used, and include R-T- including Nd-Fe-B-based alloys.
It is generically called a B-based alloy.

The RTB-based alloy has a ferromagnetic phase R ₂ T ₁₄ B crystal contributing to the magnetizing action as a main phase, and a nonmagnetic, low-melting R-rich phase enriched with a rare earth element at a crystal grain boundary. Since it is an active metal, it is generally melted in a vacuum or inert gas and cast into a mold. This alloy ingot is pulverized to a powder of about 3 μm (FSSS: measured with a Fischer sub-sieve sizer), pressed in a magnetic field, and sintered at a high temperature of about 1000 to 1100 ° C. in a sintering furnace. After that, it is usually heat treated, machined, and plated for corrosion resistance and magnetized as necessary.

[0004] The R-rich phase in the alloy plays an important role in the following points. 1) It has a low melting point and becomes a liquid phase at the time of sintering, which contributes to increasing the density of the magnet and thus improving the magnetization. 2) Eliminate irregularities in grain boundaries, reduce nucleation sites in reverse magnetic domains, and increase coercive force. 3) Increasing the coercive force by magnetically insulating the main phase. Therefore, if the dispersion state of the R-rich phase is poor, the properties and corrosion resistance of the magnet are affected, so that it is important to be uniform. The distribution of the R-rich phase as the final magnet is greatly influenced by the structure of the raw material alloy ingot. That is, when cast in a mold, the cooling rate is slow, and the crystal grains often become large. As a result, the grains when pulverized are much smaller than the crystal grain size. The R-rich phase has a lamellar shape with a large thickness, and therefore has poor dispersibility. Therefore, if the grains when pulverized are smaller than the crystal grain size, grains having only the main phase containing no R-rich phase and grains having only the R-rich phase are separately present, and uniform mixing is difficult.

Another problem in mold casting is that γ-Fe is easily formed as a primary crystal due to a low cooling rate. γ-Fe transforms to α-Fe below about 910 ° C. The transformed α-Fe causes deterioration of the pulverization efficiency at the time of magnet production, and if remaining after sintering, lowers the magnetic properties. Therefore, in the case of an ingot cast in a mold, α-Fe
Must be erased.

In order to solve these problems, a strip casting method (SC method) has been introduced as a method of casting at a higher cooling rate than a die casting method, and is used in actual processes. This is done by pouring the molten metal on a copper roll whose inside is water-cooled, and casting it into a thin strip several mm below the decimal point.
Rapid solidification, refines the crystal structure,
This is to produce an alloy having a structure in which the rich phase is finely dispersed. Since the R-rich phase in the alloy is finely dispersed, the dispersibility of the R-rich phase after pulverization and sintering is improved, and the magnetic properties have been successfully improved (Japanese Patent Laid-Open No. 5-2224).
88, JP-A-5-295490). Also,
α-Fe is hardly generated.

[0007] Further, in the alloy using the SC method, hydrogen is usually crushed as a crushing method. This method particularly utilizes the property that the R-rich phase absorbs hydrogen and breaks down from the R-rich phase due to the accompanying volume expansion, and is used for pulverization before pulverization. The important point in controlling the particle size is how to control the interval between the particles.

As described above, in order to control the distribution (interval) of the R-rich phase which has an important effect on the magnet characteristics, the cooling rate during casting is important, and particularly, the temperature near the solidification of the R-rich phase. Control is important. In JP-A-8-176755, not only the crystal grain boundaries but also the main phase (R ₂ T ₁₄ B phase) is disclosed.
There is also an R-rich phase (referred to as a eutectic region in the gazette), and control of this interval is important for magnet characteristics.
To achieve this, the temperature range (800-600) until the R-rich portion existing as a liquid phase to the end solidifies.
C.) at a cooling rate of 5 ° C./sec or more. Japanese Patent Application Laid-Open No. Hei 10-36949 discloses that the average cooling rate between 800 and 600 ° C. is 1.0 ° C./sec or less to widen the interval between R-rich phases to 3 to 15 μm.

[0009]

As described above, it is important to control the distribution of the R-rich phase in the alloy ingot from the viewpoint of the magnet properties. For this reason, controlling the temperature range from the liquid phase of the R-rich phase to the solidification. It is necessary to control the cooling rate. However, in the above-described SC method, the temperature range starts near the point where the temperature falls off the roll, and complete solidification has not yet been completed after falling off the roll. However, a clear method is disclosed for the temperature control method. It has not been done yet.
The only way to control the cooling speed on the roll was to change the peripheral speed of the roll or to adjust the amount of flowing metal to change the thickness, but this has various difficult problems. . That is, after the main phase has solidified, the contact with the roll changes from surface contact to point contact, and the cooling rate rapidly decreases. In order to stably obtain an alloy ingot having a good structure without αFe, the time during which the melt and the alloy in which the main phase has solidified is on the roll is at most a few seconds, and the time required for the R-rich phase to solidify on the roll. The temperature range cannot be controlled.
If the roll peripheral speed is reduced and the time during which the alloy lump is on the roll is increased, the thickness of the alloy lump increases and αFe is generated. Also, if the amount of molten metal supplied to the roll is reduced by lowering the crucible tilting speed, the temperature of the molten metal is reduced before reaching the roll, so that primary crystal γFe is easily generated. If the supply of the molten metal is further reduced, the molten metal is solidified before reaching the roll. Thus, in the SC method, R
There was no effective means for controlling the cooling rate near the solidification temperature of the rich phase so as to change the casting structure. Also, almost no concrete means for controlling the alloy structure even after the cast alloy has fallen off the roll has been disclosed. The present invention mainly controls the internal structure of an alloy, particularly R, by controlling the cooling rate of an alloy piece after falling off the roll and dropping in a conventional rotating roll method.
The purpose is to control the distribution state of the rich phase.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and has the following arrangement. (1) A rare earth element-containing alloy is melted in a vacuum or an inert gas, and the molten metal is flown on a cooled rotating roll in a room in a vacuum or an inert gas atmosphere, and cooled to form a ribbon. Immediately after being coagulated, the coagulated ribbon is crushed into flakes,
Storing the crushed alloy pieces in a storage container placed in the room,
A microstructure control method for a rare earth element-containing alloy, wherein a cooling rate of a crushed alloy piece is controlled by a cooling medium. (2) The storage container is provided with a partition plate for cooling therein, in which a gas or a liquid is circulated as a cooling medium to control the cooling rate of the crushed alloy pieces, and the storage container contains the rare earth element according to (1). A method for controlling the structure of an alloy. (3) The method for controlling the structure of a rare earth element-containing alloy according to (1), wherein the storage container is capable of controlling the cooling rate of the crushed alloy pieces by flowing an inert gas as a cooling medium therein. (4) The method of controlling a structure of a rare earth element-containing alloy according to (3), wherein the inert gas is caused to flow out from a cooling partition plate having a vent provided in the storage container. (5) The storage container is provided with a partition plate therein so that the cooling rate of the crushed alloy piece can be controlled (1) to (4).
The method for controlling the structure of a rare earth element-containing alloy according to any one of the above. (6) The method of any one of (1) to (5), further comprising a step of, after controlling a cooling rate of the crushed alloy piece, moving the crushed alloy piece from a room to another room and cooling it. Organization control method. (7) flowing the rare earth element-containing alloy melt on a rotating roll,
The method for controlling the structure of a rare earth element-containing alloy according to any one of (1) to (6), wherein the method of cooling and solidifying into a ribbon shape is a strip casting method. (8) The microstructure control of the rare earth element-containing alloy according to any one of (1) to (7), wherein the cooling rate of the crushed alloy piece is controlled so that the average interval of the R-rich phase of the rare earth element-containing alloy is 3 to 15 μm. Method. (9) The method for controlling the structure of a rare earth element-containing alloy according to any one of (1) to (8), wherein the average cooling rate of the crushed alloy pieces at 800 to 600 ° C is 10 to 300 ° C / min. (10) A rare earth element-containing alloy is an RTB-based alloy (where R is a rare earth element containing Y (Y, La, Ce, Pr,
Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
m, Yb, Lu), and T is Fe as a main component and a part thereof may be substituted with Co, Ni or the like.) The rare earth element according to any one of (1) to (9), A method for controlling the structure of an element-containing alloy. (11) A crushed alloy piece having a thickness of 0.1 to 0.6 mm and an average interval of R-rich phases of 3 to 15 μm obtained by the method according to any one of the above (1) to (10). Pulverized rare earth element-containing alloy powder. (12) A magnet obtained by molding and sintering the alloy powder of (11).

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Rare earth element-containing alloys are generally melted and cast in a melting chamber shielded from the atmosphere because of their active properties. The melting chamber is in a vacuum or an inert gas atmosphere such as argon or helium. FIG. 1 is a schematic view showing a casting method by the SC method applied to the present invention. In the crucible 2 placed in the melting chamber 1, the raw material metal and the like are melted by induction current heating and held as an alloy. next,
The molten metal is moved by the tilting of the crucible 2 to the adjacent vacuum casting chamber 1.
The roll 3 is set on the rotating roll 3, the inside of which is cooled by water, and is flowed through the gutter 4 and the tundish 5 on the rotating roll 3.

The solidified alloy is rolled in the middle of a rotating roll.
Move away from Before the solidified alloy is wound around the roll 3, the solidified alloy is dropped using an appropriate guide. When the alloy is released from the roll, the alloy is brittle at a high temperature. Therefore, the alloy breaks into a brittle shape by using a simple crushing means such as a guide roll 6 or simply hitting a baffle plate or the like, and is crushed into flakes and dropped. I do. Further, it may be crushed by an impact when dropped into the storage container 8.

[0013] It takes at most a few seconds for the molten metal to contact the roll and break off the roll, and as mentioned earlier, at this stage the solidified alloy is still red hot and has the lowest solidification point. The R-rich phase has not completely solidified. Usually, the crushed alloy pieces 7 are dropped and stored in a box-shaped storage container 8 placed adjacent to the roll. Since the alloy is oxidized at a high temperature, this storage container is usually placed in the same casting chamber 10 as the casting apparatus and left to cool to a temperature at which the alloy is not oxidized. Japanese Patent Application Laid-Open No. Hei 9
In JP-A-155507, a storage container containing shard alloy pieces was moved to an adjacent separate room, where it was cooled using an inert gas or the like. However, this cooling is not intended to control the structure of the alloy.

In the present invention, first, in order to control the structure at the freezing point, in particular, the R-rich phase having a low melting point, a storage container of a crushed alloy piece (hereinafter, referred to as an alloy piece) after casting is placed in a casting chamber, where a cooling medium is placed. This is a method of controlling the cooling temperature of the alloy piece by using In this method, since the alloy pieces can be simultaneously cooled while being dropped into the storage container, the cooling becomes uniform as compared with the method in which the storage container is moved to a separate chamber and cooled after the completion of casting as described in the patent publication. Further, since there is no temperature decrease until the start of the control of the cooling rate, the control temperature range can be widened. This method particularly affects the alloy structure.
It becomes easy to control the cooling rate between 00 and 600 ° C. Secondly, the cooling rate after the R-rich phase is completely solidified and the internal structure is hardened does not affect the internal structure, and since it is required in the process to take out the alloy shards as quickly as possible, the oxidation rate does not progress. It is preferable to cool as quickly as possible in an inert atmosphere or the like until the temperature can be taken out to the atmosphere of about 200 ° C.

To achieve the above two points, for example, a stainless steel net 233 is provided at the lower part of the container as shown in FIG.
From there, a container through which an inert cooling gas 23 such as helium can flow is provided. Immediately after the alloy pieces are dropped and stored, the gas is introduced, and the cooling rate of the alloy pieces can be changed by changing the gas amount. When the temperature exceeds the R-rich phase solidification temperature between 800 to 600 ° C. described above, it can be cooled at the maximum gas flow rate until it can be taken out to the next atmosphere.

In the above example, the alloy flakes are largely deposited, and cooling is performed by gas phase contact of the gas flowing between the deposits. Therefore, when the container is large, the deposits overlap and the cooling rate may be limited. . Alternatively, cooling in the container tends to vary. In such a case, as shown in FIG. 3, the inside of the storage container is divided by a hollow partition plate 211, and a cooling medium 22 is allowed to flow through the partition plate to cause contact cooling between the partition plate and the alloy plate to cool the alloy plate. Can be accelerated. In this method, the cooling medium does not come into contact with the alloy pieces,
In addition to the inert gas, a gas such as air or a liquid such as water can be used as the cooling medium. Further, the cooling can be performed as shown in FIG. FIG. 4 shows a method in which a cooling inert gas 23 is partially flown into a container through a vent 212A below a cooling partition plate 212 to cool the alloy pieces. It is more efficient to cool as soon as possible after the internal structure of the alloy has solidified, especially when performing continuous casting. As described above, rapid cooling may be performed in the casting chamber, or the storage container may be moved to another chamber and rapidly cooled there.

When the storage container is transferred to another room, the container can be covered with a lid, taken out of the casting room, sent to another inert gas room, and cooled again. The container at this time may not be a completely closed container, and it is sufficient that the inert gas is kept flowing only to the extent that it overflows from the container only during transfer. Or if the transfer time is short, after the gas is full,
The gas supply may be stopped with the lid on the top of the container.
In this case, disconnect the gas supply hose, etc. from the container and plug the connection, and if the container and lid are not completely sealed, the inert gas such as argon leaks from the container because it is heavier than the atmosphere. Nothing. Other methods for letting out the inert gas include a hollow partition plate 21 as shown in FIG.
It is also possible to provide a vent 213A on the side surface of 3 and allow the gas to flow out therefrom.

FIG. 5 and FIG. 6 show a case where a partition plate 24 for partitioning the inside of the container is inserted in the middle of the container. Without this partitioning plate, the alloy pieces may be unevenly distributed in the container and may be in a lump, which may hinder cooling. Cooling is performed by the cooling partition plate 21
213A or stainless steel net 2 at the bottom of the container
This is performed by flowing an inert gas from 33 into the container. As a cooling method, a method as shown in FIGS. 3 and 4 may be used. Removal of the storage container after the cooling is completed can be performed by, for example, providing an openable and closable door on a side surface of the casting chamber.

By the method of controlling the two-stage cooling rate in the vessel as described above, the distribution of the R-rich phase can be controlled by controlling the temperature in the first high-temperature region. Further, regardless of the cooling rate in the first temperature range, the second temperature range which does not affect the internal structure can be rapidly cooled, so that the process can be smoothly performed.

According to this method, almost 0.1 to
When an alloy piece having a thickness of 0.6 mm is cast, the temperature of the alloy piece when it separates from the roll and falls into the container becomes close to 800 ° C. From there, various cooling methods in the above-described container are selected, and the cooling rate in the first temperature range is reduced to increase the interval of the R-rich phase, and by increasing the cooling rate, the interval of the R-rich phase is increased. Can be narrowed. The casting method in the present invention is not limited to the SC method as shown in FIG. 1, but may be a method using twin rolls and flowing molten metal between rotating rolls. According to the method of the present invention, RT-
B-based alloys or the like (where R is a rare earth element containing Y (Y, L
a, Ce, Pr, Nd, Sm, Eu, Gd, Tb, D
y, Ho, Er, Tm, Yb, Lu), and T is Fe as a main component, and one part thereof may be replaced with Co, Ni or the like.) Interval of R-rich phase of rare earth element-containing alloy Can be controlled to about 3 to 15 μm. In order to set the interval of the R-rich phase in this range, the average cooling rate between 800 and 600 ° C. is suitably 10 to 300 ° C./min, preferably 1 to 300 ° C./min.
The temperature is 0 to 200 ° C / min, more preferably 10 to 50 ° C / min.

Here, the interval between the R-rich phases is determined by measuring the cross section of the alloy piece in the thickness direction with emery paper, and then buffing the surface using alumina, diamond, or the like with a reflection of a scanning electron microscope (SEM). Determined by observation with an electronic image. R
Since the rich phase has a higher average atomic number than the R ₂ Fe ₁₄ B phase as the main phase, it is observed brighter than the main phase in the backscattered electron image. The interval between the R-rich phases is determined as follows by observing the cross section in the thickness direction. At the center of the thickness plane, a line segment is drawn parallel to the roll surface (the direction parallel to the roll axis), and the length of the line segment is divided by the number of R-rich phases traversed by the line segment. The average value when this is repeated for five visual fields is defined as the R-rich phase interval.

The interval between the R-rich phases can be set to 3 to 15 μm, preferably 3 to 12 μm, more preferably 4 to 10 μm by the method of the present invention. When the interval between the R-rich phases exceeds 15 μm, the dispersion state of the R-rich phase becomes worse, and the ratio of powder particles in which the R-rich phase is present decreases when the powder is finely pulverized to 3 to 5 μm for magnetic field molding. Therefore, the dispersion state of the R-rich phase after the magnetic field molding is also deteriorated, causing a decrease in sinterability, and a decrease in magnetization and coercive force after magnetization. In addition, the uneven distribution of the R-rich phase causes a partial decrease in coercive force and a decrease in squareness after magnetization. On the other hand, if it is less than 3 μm, there is a problem that magnetic properties are deteriorated due to excessively fine crystal grains.

Next, a high-performance anisotropic magnet can be manufactured by pulverizing, shaping, and sintering the above alloy piece.

The pulverization is usually performed in the order of hydrogen pulverization, medium pulverization and fine pulverization, and is generally made into a powder of about 3 to 5 μm (FSSS).

Here, the hydrogen disintegration is divided into a pre-process hydrogen storage process and a post-process dehydrogenation process. In the hydrogen occlusion step, hydrogen is occluded mainly in the R-rich phase of the alloy piece in a hydrogen gas atmosphere at a pressure of 2.7 × 10 ⁴ Pa to 4.9 × 10 ⁶ Pa, and R-hydrogen generated at this time is absorbed. Utilizing the fact that the R-rich phase expands in volume due to the oxide, the alloy pieces themselves are finely divided or countless fine cracks are generated. In the case of the alloy pieces of the present invention, cracks can be generated along most of the R-rich phase. In particular, an R-rich phase exists at the main phase grain boundaries, and most of the crystal grain boundaries can be cracked by absorbing hydrogen. Therefore, most of the powder produced through the medium pulverization and the fine pulverization becomes a single crystal, and the magnetic properties can be improved. This hydrogen storage is carried out in the range of room temperature to about 600 ° C., but is preferably carried out in the range of room temperature to about 100 ° C. in order to increase the volume expansion of the R-rich phase and to split it efficiently. The preferred treatment time is one hour or more. The R-hydride produced in this hydrogen storage step is unstable in the air and easily oxidized,
It is preferable to perform a dehydrogenation treatment at about 0 ° C. in a vacuum of 130 Pa or less. By this treatment, R-hydride can be converted to be stable in the atmosphere. The preferred processing time is 30 minutes or more. When atmosphere control for preventing oxidation is performed in each step from hydrogen absorption to sintering, the dehydrogenation treatment can be omitted. It should be noted that medium pulverization and fine pulverization can also be performed without performing the hydrogen pulverization.

The term “medium pulverization” refers to pulverization of an alloy piece in an inert gas atmosphere such as argon gas or nitrogen gas to, for example, 500 μm or less. A pulverizer for this purpose is, for example, a brown mill pulverizer. In the case of the hydrogen-crushed alloy piece of the present invention, since it is already finely cracked or has an infinite number of fine cracks inside, the pulverization can be omitted.

Fine grinding refers to grinding to about 3 to 5 μm (FSSS). A crusher for this purpose is, for example, a jet mill device. In this case, the atmosphere during the pulverization is an inert gas atmosphere such as an argon gas or a nitrogen gas. 2% by mass or less, preferably 1% by mass or less of oxygen may be mixed into these inert gases. As a result, the pulverization efficiency is improved, and the oxygen concentration of the pulverized powder is 1000 to 10000 ppm, and the oxidation resistance is improved. Also, abnormal grain growth during sintering can be suppressed.

Molding is carried out in a magnetic field. In order to reduce the friction between the powder and the inner wall of the mold during the magnetic field molding and to reduce the friction between the powders to improve the orientation, stearic acid is added to the powder. It is preferable to add a lubricant such as zinc. A preferable addition amount is 0.01 to 1% by mass. The addition may be performed before or after the pulverization, but it is preferable that the addition is sufficiently performed by using a V-type blender or the like in an inert gas atmosphere such as an argon gas or a nitrogen gas before molding in a magnetic field.

The finely pulverized powder is pressed by a molding machine in a magnetic field. The mold is manufactured by combining a magnetic material and a non-magnetic material in consideration of the direction of the magnetic field in the cavity. The molding pressure is preferably 0.5 to ² t / cm ² . The magnetic field in the cavity during molding is preferably 5 to 20 kOe. Also,
The atmosphere at the time of molding is preferably an inert gas atmosphere such as an argon gas or a nitrogen gas. However, in the case of the above-mentioned oxidation-resistant powder, it can be performed in the air.

The sintering is performed at 1000 to 1100 ° C. Before sintering, it is necessary to completely remove the lubricant and hydrogen from the compact. A preferable condition for removing the lubricant is to keep the molded body at 300 to 500 ° C. for 30 minutes or more in a vacuum of 1.3 Pa or less or in a reduced pressure argon atmosphere. The preferable conditions for removing hydrogen are 1.3 P
a to be maintained at 700 to 900 ° C. for 30 minutes or more in a vacuum of a or less. The atmosphere during sintering is preferably an argon gas atmosphere or a vacuum atmosphere of 1.3 Pa or less. The holding time is preferably one hour or more.

After sintering, heat treatment can be performed at 500 to 650 ° C. as needed to improve coercive force. A preferred atmosphere is an argon gas atmosphere or a vacuum atmosphere.
The preferred holding time is 30 minutes or more.

[0032]

The results of controlling the structure (R-rich phase) will be described below with reference to examples. (Example 1) Alloy composition: Nd: 30.0% by mass, B:
1.00% by mass, Co: 2.0% by mass, Al: 0.30
% By mass, Cu: 0.10% by mass, with the balance being iron,
Mixing metal neodymium, ferroboron, cobalt, aluminum, copper, and iron, using an alumina crucible, and melting in a high-frequency melting furnace (crucible) in an atmosphere of 1 atmosphere of argon gas, the molten metal has a peripheral speed of 0.97 m / sec. Diameter 4 rotating at
Flowed through a tundish on a 0 cm copper roll.
The total weight of the molten metal was 15 kg, and the temperature of the molten metal at the start of casting was 1450 ° C. During the casting, the inside of the copper roll was water-cooled.

The alloy solidified on the copper roll was crushed by a guide roll provided at a position where the alloy was separated and dropped from the copper roll, and stored in a box-shaped storage container provided thereunder. The storage container was 31 cm in length, 21 cm in width, and 40 cm in height in outer dimensions, and was made of a 5 mm-thick iron plate. Further, as shown in FIG. 2, a stainless steel net having a mesh width of 5 mm was placed at a height of 1 cm from the bottom plate at the bottom of the storage container, and the crushed alloy pieces were stored on the net. The argon gas was continuously flowed from the bottom to the top of the stainless steel net at a flow rate of 30 liter / min from immediately before the start of casting to 10 minutes after the end of casting.

Considering that the temperature at the time of dropping the alloy is almost the same as the temperature of the alloy pieces stored in the storage container, a small hole was made in the side surface of the storage container, and the alloy was set so as to protrude from the hole into the storage container. It was determined by measuring with a thermocouple. The temperature at the time of dropping of the alloy piece determined by this method was 780 ° C.
The alloy pieces were then cooled slowly, taking 5 minutes to cool to 600 ° C. End of casting 10
After one minute, the flow rate of the argon gas flowing from the bottom to the top of the stainless steel net was increased to 100 liter / minute to cool the alloy pieces. After 2 hours, the temperature of the alloy piece was 98 ° C. Thereafter, the alloy piece was taken out into the atmosphere, and the average thickness was measured by a micrometer, and the interval of the R-rich phase was measured by using a cross-sectional photograph by a backscattered electron image of a SEM.
Table 1 shows the measurement results.

(Example 2) A raw material metal and the like were blended so as to have the same composition as in Example 1, and using the apparatus of Example 1,
An alloy piece was prepared. The container shown in FIG. 2 was used. However, immediately before the start of casting, helium gas was continuously flowed from the bottom of the container at a flow rate of 100 liter / min. The temperature at the time of dropping of the alloy piece was 750 ° C., and the time required for cooling to 600 ° C. was 40 seconds. After casting is finished,
When the helium gas was kept flowing as it was to cool the alloy pieces, the temperature of the alloy pieces was 96 ° C. 30 minutes after the end of casting.
Went down. Thereafter, the alloy piece was taken out into the atmosphere, and the average thickness was measured by a micrometer, and the interval of the R-rich phase was measured by using a cross-sectional photograph by a backscattered electron image of a SEM. Table 1 shows the measurement results.

(Example 3) Raw materials and the like were blended so as to have the same composition as in Example 1, melted under the same conditions as in Example 1, and the molten metal was cast on a copper roll similar to that in Example 1. did. The alloy solidified on the copper roll was crushed by the same guide roll as in Example 1, and stored in a box-shaped storage container installed thereunder. The storage container is 31cm in length and 21c in width.
m, a height of 40 cm, and a 5 mm-thick iron plate. Further, as shown in FIG. 3, two iron partition plates 211 having a thickness of 7 cm were installed at equal intervals along the direction perpendicular to the rotation axis of the copper roll inside the storage container. The structure was such that the gas flowing into each partition plate did not leak into the storage container. Argon gas was continuously flowed into each partition plate at a flow rate of 100 liter / min immediately before casting.

The temperature at the time of dropping of the alloy obtained in the same manner as in Example 1 was 790 ° C. The alloy pieces were then cooled slowly, taking 7 minutes to cool to 600 ° C. After the casting was completed, the alloy piece was cooled by continuing the flow of argon gas as it was.
After a time, the temperature of the alloy slab dropped to 106 ° C. Thereafter, the alloy piece was taken out into the atmosphere, and the average thickness was measured by a micrometer, and the interval of the R-rich phase was measured by using a cross-sectional photograph by a backscattered electron image of a SEM. The measurement results are shown in Table 1.

(Example 4) A raw material metal and the like were blended so as to have the same composition as in Example 1, and using the apparatus of Example 3,
An alloy piece was prepared. The storage container is as shown in FIG. 3 except that water was continuously flowed into each partition plate at a flow rate of 30 liter / min immediately before casting. The temperature at the time of falling of the alloy obtained in the same manner as in Example 1 was 790 ° C. The alloy pieces were then cooled slowly, taking 6 minutes to cool to 600 ° C. After casting is finished,
When the alloy pieces were cooled by continuously flowing water, the temperature of the alloy pieces dropped to 98 ° C. two hours after the end of casting. Thereafter, the alloy piece was taken out into the atmosphere, and the average thickness was measured by a micrometer, and the interval of the R-rich phase was measured by using a cross-sectional photograph by a backscattered electron image of a SEM.
Table 1 shows the measurement results.

Example 5 Raw materials and the like were blended so as to have the same composition as in Example 1, melted under the same conditions as in Example 1, and the molten metal was cast on the copper roll of Example 1. The alloy solidified on the copper roll was crushed by the guide roll of Example 1 and stored in a box-shaped storage container installed thereunder. The storage container is 31cm long, 21cm wide and 40cm high in external dimensions.
And was made of a 5 mm-thick iron plate. Further, as shown in FIG. 4, two iron partition plates 212 each having a thickness of 7 cm and having a structure in which gas flows out from the lower portion toward the inside of the container are installed at equal intervals along the direction perpendicular to the rotation axis of the copper roll. . Immediately before casting, an argon gas was continuously flown through each vent plate 212A at a flow rate of 30 liter / min.

The temperature at the time of dropping of the alloy obtained in the same manner as in Example 1 was 780 ° C. The alloy pieces were then cooled slowly, taking 5 minutes to cool to 600 ° C. Ten minutes after the completion of casting, the flow rate of argon gas flowing through each partition plate was increased to 100 liters / minute, and a lid was placed on the upper part of the storage container. Moved. Even after the storage container was moved to another room for both reducing the oxygen concentration in the room and cooling the alloy pieces that were increased with this operation, each partition plate still contained argon at a flow rate of 100 liter / min. The gas continued to flow.
Two hours after the end of casting, the temperature of the alloy piece was 94 ° C. Thereafter, the alloy piece was taken out into the atmosphere, and the average thickness was measured by a micrometer, and the interval of the R-rich phase was measured by using a cross-sectional photograph by a backscattered electron image of a SEM.
Table 1 shows the measurement results. When the oxygen concentration of this alloy piece was measured, it was 140 ppm, which was equivalent to the oxygen concentration of the alloy piece of Example 1 of 130 ppm. From this, no oxidation of the alloy pieces due to the movement of the storage container was observed.

Example 6 The alloy composition was Nd: 29.0.
% By mass, Dy: 3.5% by mass, B: 1.05% by mass, C
o: 1.0% by mass, Al: 0.30% by mass, Cu: 0.
10% by mass, metal neodymium, metal dysprosium, ferroboron, cobalt, aluminum, copper and iron are blended so that the balance is iron, and melted in a high-frequency melting furnace in an atmosphere of 1 atm of argon gas using an alumina crucible. did.
This molten metal was flowed on the copper roll of Example 1 through the same tundish as in Example 1. The total weight of the melt is 1
The molten metal temperature at the start of casting was 1450 ° C. The roll peripheral speed was 0.97 m / sec.

The alloy solidified on the copper roll was crushed by the guide roll of Example 1 and stored in a box-shaped storage container installed thereunder. The storage container is 31cm in length and 21c in width.
m, a height of 40 cm, and a 5 mm-thick iron plate. Further, as shown in FIG. 5, two partitioning plates 24 each having a thickness of 2 cm were placed inside the container at regular intervals along the direction perpendicular to the rotation axis of the copper roll. This partition plate is a refractory mainly composed of alumina,
Is 0.2 kcal / (mh ° C.) (0.23
W / m · ° C.). In addition, an iron cooling partition plate 213 having a thickness of 3 cm was provided between the partition plates. This partition plate has a hollow inside, and many holes 213A having a diameter of 1 mm are formed on both side surfaces, and an inert gas is poured into the storage container through these holes to cool the alloy pieces. . The argon gas was flowed through the partition plate at a flow rate of 10 liters / minute from just before the start of the casting to 10 minutes after the end of the casting, and the alloy pieces were cooled with the argon gas flowing out of the holes on the side surfaces of the partition plate.

The temperature at the time of dropping of the alloy obtained in the same manner as in Example 1 was 690 ° C. The alloy pieces were then cooled slowly, taking 6 minutes to cool to 600 ° C. Ten minutes after the end of casting, the flow rate of argon gas flowing through each partition plate was increased to 50 liter / min, and the alloy pieces were cooled with argon gas blown out from holes in the side surfaces of the partition plates. The temperature of the alloy piece after 2 hours is 101 ° C
Met. Thereafter, the alloy was taken out into the atmosphere, and the average thickness was measured using a micrometer, and the distance between R-rich phases was measured using a cross-sectional photograph based on a backscattered electron image of a SEM. Table 1 shows the measurement results.

(Example 7) Raw materials and the like were blended so as to have the same composition as in Example 6, melted under the same conditions as in Example 1, and the molten metal was cast on the copper roll of Example 1. The alloy solidified on the copper roll was crushed by the guide roll of Example 1 and stored in a box-shaped storage container installed thereunder. As for the storage container, three partition plates having a thickness of 2 cm are installed at regular intervals in the storage container along the direction perpendicular to the rotation axis of the copper roll in the container of Example 1, as shown in FIG. Structured. The material of the partition plate is the same as that of the sixth embodiment. From just before the start of casting to 10 minutes after the end of casting, argon gas was supplied at a flow rate of 1 from the bottom to the top of the stainless steel mesh at the bottom of the container.
Flowed at 0 liter / min.

The temperature at the time of dropping of the alloy obtained in the same manner as in Example 1 was 690 ° C. The alloy pieces were then cooled slowly, taking 6 minutes to cool to 600 ° C. Ten minutes after the completion of casting, the gas flowing from the bottom to the top of the stainless steel mesh at the bottom of the storage container was changed to helium gas, and the gas was flowed at a flow rate of 100 liter / minute to cool the alloy. After 30 minutes, the temperature of the alloy piece was 103 ° C. Thereafter, the alloy was taken out into the atmosphere, and the average thickness was measured using a micrometer, and the distance between R-rich phases was measured using a cross-sectional photograph based on a backscattered electron image of a SEM. Table 1 shows the measurement results.

(Comparative Example 1) Raw materials and the like were blended so as to have the same composition as in Example 1, melted under the same conditions as in Example 1, and the molten metal was cast on the copper roll of Example 1. The alloy solidified on the copper roll was crushed by the guide roll of Example 1 and stored in a box-shaped storage container installed thereunder. The storage container is 31cm long, 21cm wide and 40cm high in external dimensions.
And was made of a 5 mm-thick iron plate. However, without providing a net, a cooling partition plate, a partition partition plate as in Examples 1 to 7 in the storage container, without cooling with an inert gas or the like,
The cooling rate of the alloy pieces in the container was not controlled.

The temperature at the time of dropping of the alloy obtained in the same manner as in Example 1 was 790 ° C. The subsequent cooling rate of the alloy piece was extremely low, and the alloy piece was cooled slowly, and the time required for cooling to 600 ° C. was 1 hour. further,
The lower the temperature of the alloy slab, the slower the cooling rate,
The temperature of the alloy slab reached 200 ° C. in the atmosphere where oxidation did not proceed, 8 hours after the end of casting, and it took a very long time. Thereafter, when the alloy was taken out into the atmosphere, the alloy pieces were firmly fused together, and it was not possible to measure the average thickness with a micrometer. It is possible to measure the interval of the R-rich phase using a cross-sectional photograph based on the backscattered electron image of the SEM, and the measurement results are shown in Table 1.

[0048]

[Table 1]

Production of Magnet (Example 8) The alloy pieces obtained in Example 1 were pulverized in the order of hydrogen pulverization, medium pulverization and fine pulverization. The condition of the hydrogen storage step, which is a step before the hydrogen disintegration step, was kept at 100% hydrogen atmosphere and 1 atm for 1 hour. The temperature of the alloy piece at the start of the hydrogen storage reaction was 25 ° C. The condition of the dehydrogenation step, which is a subsequent step, was maintained at 500 ° C. for 1 hour in a vacuum of 13 Pa.
Using a brown mill apparatus for the medium pulverization, the powder pulverized with hydrogen was pulverized to 425 μm or less in a 100% nitrogen atmosphere. 0.07% by mass of zinc stearate powder was added to this powder, and the mixture was sufficiently mixed with a V-type blender in a 100% nitrogen atmosphere, and then 3.2 μm (FSS) with a jet mill device.
Finely pulverized to S). Atmosphere during grinding is 4000pp
m in a nitrogen atmosphere mixed with oxygen. Thereafter, the mixture was again sufficiently mixed in a V-type blender in a 100% nitrogen atmosphere. The oxygen concentration of the obtained powder was 2500 ppm. From the analysis of the carbon concentration of this powder, it was calculated that the zinc stearate powder mixed with the powder was 0.05% by mass.

Next, the obtained powder was press-molded in a horizontal magnetic field in a 100% nitrogen atmosphere using a molding machine. Molding pressure is 1.2
t / cm ² and the magnetic field in the mold cavity is 15 kO
e. The obtained molded body is kept at 500 ° C. for 1 hour in a vacuum of 1.3 × 10 ⁻³ Pa, and then 1.3 × 10 ⁻³ P
a. The solution was kept at 800 ° C. for 2 hours in a vacuum to remove zinc stearate and hydrogen, and then kept in a vacuum of 1.3 × 10 ⁻³ Pa for 1 hour.
It was kept at 060 ° C. for 2 hours for sintering. The sintered density is 7.
The density was 52 g / cm ³ , which was a sufficiently large density. Further, this sintered body was heat-treated at 540 ° C. for 1 hour in an argon atmosphere.

When the magnetic properties of this sintered body were measured using a DC BH curve tracer, Br = 13.9 kG, iH
c = 10.6 kOe, (BH) max = 45.4MGO
e. The oxygen concentration of this sintered body was 3100 ppm. The cross section of the sintered body was mirror-polished, and the surface was observed with a polarizing microscope. The average size of the crystal grains was 15 to 20 μm, which was almost uniform.

(Comparative Example 2) The alloy piece obtained in Comparative Example 1 was pulverized in the same manner as in Example 8 and crushed to 3.3 μm (F
SSS) size powder was obtained. The oxygen concentration of the powder is 26
It was 00 ppm. This powder was molded in a magnetic field and sintered in the same manner as in Example 8 to produce an anisotropic magnet. However, when the sintering temperature is 1060 ° C., the sintering density is 7.
38 g / cm ³ , and sintering was insufficient. For this reason, the sintering temperature was increased to 1090 ° C.

When the magnetic properties of the obtained sintered body were measured by the same direct current BH curve tracer as in Example 8, when the sintering temperature was 1060 ° C., Br = 13.5 kG and iHc =
9.8 kOe, (BH) max = 42.8 MGOe. When the sintering temperature is 1090 ° C., 13.8 k
G, iHc = 7.4 kOe, (BH) max = 35.2
MGOe. The oxygen concentration of the magnet was 3100 ppm and 3200 ppm, respectively. The cross section of these sintered bodies was mirror-polished, and the surfaces were observed with a polarizing microscope. The size of the crystal grains of the sintered body at a sintering temperature of 1060 ° C. was 15 to 20 μm on average, and was almost uniform. It was the size of. However, in the case of a sintered body at a sintering temperature of 1090 ° C., most of the crystal grains were almost uniform and had a size of 20 to 25 μm on average, but grew to several tens to several hundreds of μm in some places. Crystal grains were observed. In order to investigate the reason why the density did not become sufficiently large at the sintering temperature of 1060 ° C., the cross section of the finely pulverized particles was observed with a reflection electron image of a scanning electron microscope. As a result, in Example 8, a large number of particles having an R-rich phase were found at the end, whereas in Comparative Example 2, such particles were considerably small, and particles having only the R-rich phase were conspicuous. Was. From this, it was found that in the powder of Comparative Example 2, the dispersibility of the R-rich phase was poor, so that a sintered body having a sufficient density was not obtained at the same sintering temperature as in Example 8.

[0054]

According to the method of the present invention, the distribution of the R-rich phase of the alloy can be easily controlled by controlling the cooling rate of the alloy pieces in the container, especially the cooling rate between 800 and 600 ° C. Further, since the cooling can be rapidly performed in a temperature range lower than that, the cooling time of the alloy slab after casting can be shortened, which is very effective in operation. Further, the magnet obtained by sintering the alloy powder produced by the method of the present invention has a good R-rich phase dispersion and good magnet properties.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a method for melting and casting a rare earth element-containing alloy.

FIG. 2 is a view showing one method of cooling a cast and crushed alloy piece in a storage container.

FIG. 3 is a diagram showing another example of the cooling method according to the first embodiment.

FIG. 4 is a view showing still another example of the cooling method according to the first embodiment.

FIG. 5 is a view showing still another example of the cooling method of the above.

FIG. 6 is a view showing still another example of the cooling method of the above.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 melting chamber 2 crucible 3 roll 4 gutter 5 tundish 6 guide roll 7 alloy piece 8 storage container 10 casting chamber 211, 212 cooling partition plate 212A ventilation port 213 cooling partition plate 213A ventilation port 22 inert gas or cooling liquid 23 non Activated gas 233 Stainless steel net 24 Partition board

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 1/053 H01F 41/02 G 1/06 1/04 H 41/02 1/06 A F term (reference 4K017 AA04 BA06 BB12 BB18 CA03 DA04 EA03 ED01 5E040 AA04 BD01 CA01 HB19 NN06 NN18 5E062 CD04 CE04 CG03

Claims (12)

[Claims] 1. A rare earth element-containing alloy is melted in a vacuum or an inert gas, and the melt is flown over a cooled rotating roll in a room in a vacuum or an inert gas atmosphere.
Immediately after being cooled and solidified into a thin strip, the solidified thin strip is crushed into pieces, the crushed alloy pieces are placed in a storage container placed in the room, and the cooling rate of the crushed alloy pieces is reduced by a cooling medium. A method for controlling the structure of a rare earth element-containing alloy, comprising controlling the structure. 2. A storage container, wherein a cooling partition plate is provided inside, and a gas or a liquid as a cooling medium is circulated in the partition plate to control a cooling rate of the crushed alloy pieces.
2. The method for controlling the structure of a rare earth element-containing alloy according to item 1. 3. The structure control method for a rare earth element-containing alloy according to claim 1, wherein the storage container is capable of controlling the cooling rate of the crushed alloy pieces by flowing an inert gas as a cooling medium therein. 4. The structure control method for a rare earth element-containing alloy according to claim 3, wherein the inert gas is caused to flow out from a cooling partition plate having a vent provided in the storage container. 5. The method for controlling the microstructure of a rare earth element-containing alloy according to claim 1, wherein the storage container has a partitioning plate provided therein so as to control a cooling rate of the crushed alloy pieces. . 6. The rare earth element-containing alloy according to claim 1, further comprising, after controlling the cooling rate of the crushed alloy piece, moving the crushed alloy piece from a room to another room and cooling it. Organization control method. 7. The method of flowing a rare earth element-containing alloy according to any one of claims 1 to 6, wherein the method of flowing the rare earth element-containing alloy melt on a rotating roll, cooling and solidifying the molten metal into a thin strip shape is a strip casting method. Organization control method. 8. The rare earth element-containing alloy according to any one of claims 1 to 7, wherein a cooling rate of the crushed alloy pieces is controlled so that an average interval between R-rich phases of the rare earth element-containing alloy is 3 to 15 μm. Organization control method. 9. The method for controlling the structure of a rare earth element-containing alloy according to claim 1, wherein an average cooling rate of the crushed alloy pieces between 800 and 600 ° C. is 10 to 300 ° C./min. 10. A rare earth element-containing alloy is an RTB-based alloy (where R is a rare earth element containing Y (Y, La, C
e, Pr, Nd, Sm, Eu, Gd, Tb, Dy, H
o, Er, Tm, Yb, Lu)
The method for controlling the structure of a rare earth element-containing alloy according to any one of claims 1 to 9, wherein the seed and T are Fe as a main component and a part thereof may be substituted with Co, Ni, or the like. 11. The method according to claim 1, wherein the thickness obtained by the method according to claim 1 is 0.1 to 0.6 mm,
A rare earth element-containing alloy powder obtained by crushing a crushed alloy piece having an average rich phase interval of 3 to 15 μm. 12. A magnet obtained by molding and sintering the alloy powder of claim 11.