JPH09237733A - Method for manufacturing rare-earth permanent magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent waving and fracture of a capsule during rolling and make stable production in a method for manufacturing a permanent magnet in which a R-Fe-B based alloy is sealed in the metal capsule to make hot working. SOLUTION: In this manufacturing method, an alloy in which R, Fe and B are material basical components is melted and cast, and the cast ingot is airtightly sealed in a metal capsule at a melting point of 1200 deg.C or more and made hot working at a temperature of 800 to 1100 deg.C. Thereafter, a magnet is fetched out and heated, and next cut and ground to be in a desired shape. In this embodiment, when a width of the cast ingot is a and vertical and lower plate thicknesses of the metal capsule are h, a h/a value is set to be 0.1 to 4. In the case of a multiple capsule, when a most inside capsule width is c, at least a capsule or more enter the above range in h/c.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a transition metal containing R, Fe, and B to which magnetic anisotropy is imparted by hot working.
A method for producing a rare earth permanent magnet excellent in magnetic properties and mechanical strength by encapsulating an alloy ingot in a metal capsule and performing hot rolling. Regarding

[0002]

2. Description of the Related Art In a method of manufacturing a rare earth permanent magnet that imparts magnetic anisotropy by hot working, a method of encapsulating an alloy in a metal capsule and working is disclosed in, for example, Japanese Patent Laid-Open No. 1-17.
It is disclosed in Japanese Patent Publication No. 1204. In this method, the alloy ingot is covered with a metal capsule to allow processing in the atmosphere (prevention of oxidation). The internal ingot is hard to cool (heat retention). Prevents the liquid phase from jumping out even when processing in a semi-molten state. By applying a constraint, high strain rate machining is possible without cracking and high productivity. And so on.

When the alloy ingot is covered with a metal capsule for hot working, if the combination of the hot working method, the metal material of the capsule, the thickness of the capsule, the gap, the encapsulation method, etc. is inappropriate, the capsule is not processed during the working. Rippling occurs and sufficient restraining force cannot be obtained and uniform deformation cannot be obtained, the expected magnetic performance cannot be obtained, and further, the capsule breaks and the rolling itself cannot be performed, or the alloy ingot is broken. There are problems such as being lost.

However, the above publication does not describe anything about the structure of the capsule and the relationship between the capsule size and the alloy size.

As a hot working method, a hot rolling method which is excellent in mass productivity is adopted.
Details are disclosed in Japanese Patent Publication No. 8. This method is
In the method for manufacturing an e-B magnet, hot rolling is performed while enclosing a metal capsule through a lubricant (glass lubricant, BN, alumina, etc.) and then applying a constraint in the width direction of the capsule at 750 to 1150 ° C. Occurrence of cracks in the magnets by setting the upper and lower plate thicknesses of the metal capsules to be 20% or more of the alloy ingot plate thickness and setting the plate width / plate thickness ratio of the metal capsules to 1.5 or more. It is disclosed that the above can be prevented.

The plate thickness of the metal capsule in this method being 20% or more of the plate thickness of the alloy ingot improves the cooling condition of the alloy after rolling and prevents the magnet from breaking due to thermal shock due to rapid cooling. Therefore, there is no description about waviness and breakage of the capsule during rolling, and prevention of cracking caused by them.

Further, the plate width / plate thickness ratio of the metal capsule is 1.
When it is 5 or more, the binding force applied to the alloy is strengthened to prevent cracking. However, only showing the ratio of the capsule itself, regarding the alloy and the capsule size,
There is no description.

[0008]

As described above, in the method for producing a rare earth magnet in which a conventional casting alloy is encapsulated in a metal capsule and subjected to a hot rolling method, deformation of the capsule during rolling is affected by alloy size and capsule size. It is necessary to make a proper combination of sizes, but there is no explicit description about it,
It does not provide a method for stably manufacturing a large-sized magnet having high magnetic performance and mechanical strength.

If the capsule breaks during rolling, it is expected that the worst rolling itself will be impossible. Even if rolling is possible, the alloy cannot be uniformly deformed, resulting in non-uniform magnetic performance and fracture. The alloy in a semi-molten state penetrates into the part, and further, that part becomes the starting point of the crack during cooling,
The difference in heat shrinkage with the capsule leads to cracking and yield loss.

The present invention solves the above-mentioned drawbacks of the prior art and the reduction in yield due to cracking in the permanent magnet manufacturing method. The object of the present invention is to provide a large magnet having excellent mechanical strength. In R-Fe-B permanent magnets produced by various casting and hot rolling methods, the relationship between alloy size and capsule size is clarified, and by keeping the size within an appropriate range, waviness and breakage of capsules during hot rolling can be prevented. It is to prevent yield loss due to cracking and surface irregularities. As a result, it is to provide a stable manufacturing method of a high-performance, high-strength, low-cost permanent magnet.

[0011]

According to a first aspect of the present invention, an alloy containing R, Fe and B as a raw material basic component is melted and cast into a metal capsule having a melting point of 1200 ° C. or higher, which is then sealed. The entire capsule is heated to a temperature of 800 to 1100 ° C., the alloy ingot is hot-rolled together with the capsule in a semi-molten state with a liquid phase / solid phase volume ratio of 5% to 40%, and the alloy is magnetically different. In the method for producing a rare earth permanent magnet that is made to be anisotropic,
The ratio h / a of these metal capsules is 0.1 to 4, where a is the width of the alloy ingot and h is the thickness of the metal capsule in the pressing direction. It is a method of manufacturing a rare earth permanent magnet.

The invention according to claim 2 is the method for producing a rare earth permanent magnet according to claim 1, characterized in that the alloy ingot is composed of a plurality of ingots.

According to the third aspect of the present invention, when the width of the metal capsule is W and the height is H, the ratio W / H is 1.5 or more, and the h / a is 0.1 to 4. And a method for producing a rare earth permanent magnet.

According to a fourth aspect of the present invention, when the height of the alloy ingot is b, the ratio h / b of the upper and lower plate thickness of the capsule is 0.
It is 2 or more and said h / a is 0.1-4, It is a manufacturing method of the rare earth permanent magnet characterized by the above-mentioned.

According to the fifth aspect of the present invention, when the metal capsule is composed of multiplex capsules (n-fold n is a natural number of n> 2), the upper and lower plate thickness of the i-th capsule counted from the inside is h, (i- 1) When the width of the 1st capsule is c, (i
Is a natural number such that n ≧ i> 1, and the ratio of h / c is 0.1 to 4
The method for producing a rare earth permanent magnet is characterized in that there is at least one or more capsules.

The invention according to claim 6 is the method for producing a rare earth permanent magnet according to claim 1 or 5, characterized in that the material of the capsule is carbon steel having a carbon content of 1 wt% or less.

According to a seventh aspect of the invention, the workability of rolling is 70.
% -80%, It is a manufacturing method of the rare earth permanent magnet of Claim 1 or Claim 6 characterized by the above-mentioned.

The invention according to claim 8 is the method for producing a rare earth permanent magnet according to claim 1 or 6, characterized in that the average roll peripheral speed during hot rolling is 1 to 500 m / min.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The scope of the present invention will be described below.

The mechanism by which magnetic anisotropy is imparted by the manufacturing method of the present invention is considered as follows.
By heating the alloy together with the capsules to a temperature of 600 ° C. or higher, first, the grain boundary phase of the metal melts and becomes a liquid phase. At this time, since the main phase (R ₂ Fe ₁₄ B grains) remains a solid phase,
It becomes a semi-molten state in which solid and liquid are mixed. The capsules and alloys are rolled in that state, the flow of the liquid phase and the deformation of the capsule shape cause the solid phase having magnetic uniaxial anisotropy to rotate in the main phase and align in a certain direction. If it is solidified as it is, it becomes magnetically anisotropic and high magnetic performance is realized. That is, processing in a semi-molten state is essential to obtain a high-performance magnet.

The rolling temperature is preferably at least 800 ° C. or more in order to obtain a sufficient liquid phase flow, and its upper limit is 1100 in order to avoid a decrease in iHc due to a sudden coarsening of the main phase grains. It is desirable to set the temperature to ° C.

The amount of liquid phase during rolling is determined by the composition of the alloy and the working temperature, and becomes larger as the B and R become lower and the temperature becomes higher. If this liquid phase amount is less than 5% of the total volume,
The main phases contact each other without reaching the entire area, and there is a part where the main phase breaks during processing.
It becomes difficult to give sufficient anisotropy. In addition, the strain during processing cannot be sufficiently relaxed, and the strain during processing remains as a crack and reduces the yield. On the other hand, if it is more than 40%, the main phase responsible for magnetism relatively decreases, and high magnetic performance cannot be expected.

The preferred composition of the permanent magnet in the present invention will be described below.

As rare earth elements, Y, La, Ce, P
r, Nd, Sm, Eu, Gd, Tb, Dy, Ho, E
r, Tm, Yb, and Lu are listed as candidates, and among these, one kind or a combination of two or more kinds is used. The highest characteristic is obtained with Pr, so Pr and Pr are practically used.
-Nd, Ce-Pr-Nd alloy or the like is used.

12-25 atomic% is suitable for the rare earth element,
If it is less than 12 atomic%, a sufficient liquid phase will not be formed, and it will be easily cracked during processing and the yield will be reduced. On the other hand, if it exceeds 25 atom%, the amount of the non-magnetic phase increases and the magnetic properties remarkably deteriorate.

Fe is preferably 65 to 85 atomic%, and 6
If it is less than 5 atomic%, the amount of the non-magnetic phase increases too much and the performance deteriorates. On the other hand, when it exceeds 85 atomic%, the amount of the rare earth element decreases, and the problem described in the explanation of the rare earth element appears.

B is preferably 2 to 8 atomic%, and 2 atomic%
If it is less than the above, a high coercive force cannot be expected because it becomes a rhombohedral R-Fe system. On the other hand, if it exceeds 8 atomic%, it is difficult to obtain fine R ₂ Fe ₁₄ B grains and the hot workability is deteriorated, and it becomes impossible to obtain a high coercive force.

Further, Co is effective for raising the Curie temperature, and the coercive force is not significantly impaired if the Fe content is replaced within 50%.

Cu, Ag, and Au have the effects of enhancing hot workability and improving coercive force and squareness, but form a nonmagnetic phase, so the addition amount is preferably 6 atomic% or less.

When the above alloy is encapsulated in a metal capsule and rolled in a semi-molten state, swelling occurs before and after a rolling roll during rolling. FIG. 1 shows a conceptual sectional view of the vicinity of a rolling roll during this hot rolling. This is because the metal is in a semi-molten state, so that the pressure of the rolling roll is transmitted to other than under the rolling roll by using the liquid phase as a medium.

This swelling pressure P acts isotropically, but there is no problem because the rolling direction (longitudinal direction) is a direction that extends in the entire direction, and the width direction also becomes a width widening direction, and a plurality of alloys are placed side by side. In that case, it does not cause a big problem because it becomes an adhesive force. The remaining rolling direction (thickness direction) works as a force that pushes the upper and lower plates of the rolling. Since the upper and lower plates become thinner by rolling, if the strength of the upper and lower plates is insufficient, the following defects will occur.

The swelling force of the upper and lower plates plastically deforms them to form a space between the alloy and the capsule. When a space is created, the liquid phase flows in, causing nonuniformity of the liquid layer. Therefore, the generation condition of the space is not uniform and so-called waviness occurs. When this waviness occurs, the reaction between the capsule and the metal becomes non-uniform, leading to cracking.

Stress concentration occurs at the corners and the capsule breaks. In the case of a single capsule, rolling is impossible, and in the case of a multiple capsule, rolling continues, but the first and second
Semi-molten metal enters between the weights and becomes the starting point of the crack during slow cooling.

If there is an unwelded part inside the capsule,
The gap expands and the semi-molten metal enters the gap and becomes the starting point of the crack. If this is repeated in each pass, the weld will break. Furthermore, it becomes the same as the above.

Here, since the liquid phase serves as a medium and the rolling roll is generally wider than the work piece, the bulging pressure P is expected to be generated substantially evenly in the width direction of the rolled material. It In addition, since the capsule itself has to be deformed under the rolling roll, the pressure P has a pressure similar to the yield stress Y of the capsule at that time just below the rolling roll. This pressure will be transmitted by the liquid phase.

Since the alloy is in a semi-molten state with a grain size of several tens of μm and a fine solid phase, the pressure P decreases as the distance from the rolling roll increases. The transmission distance depends on the liquid phase ratio. If the liquid phase is small, the distance is transmitted only in the very vicinity of the rolling roll, but if the liquid phase is increased, the distance is gradually increased. In this case, the pressure nearer to the rolling roll is higher, and
It becomes a state like. That is, the swelling pressure P is at most about the yield stress Y of the capsule.

From the above, the state of the upper and lower plates in the vicinity of the rolling roll can be approximated to the state in which a force is evenly applied to the doubly supported beams. It is known that the limit pressure Pe that can be applied to the beam at this time is determined by the plate thickness h and the width a and is given by the following equation. (Reference: Basic Engineering Complete Book 3 Plasticity, Hideaki Kudo, Morikita Publishing P20) Pe = 4h ² / 3a ² Y (where Y is the yield stress of the beam material) When a pressure of Pe or more is applied to the beam, this beam yields. It will cause plastic deformation. The swelling pressure P is this limit pressure P
If it is e or less, the material is only elastically deformed, plastic deformation does not occur, and waviness and breakage of the capsule basically do not occur.
It is obvious that this limit pressure is below the yield stress,
When h / a is 0.866 or more, Pe exceeds the calculated yield stress. Therefore, even if h is further increased, there is no effect on the bulging pressure. That is, the initial thickness h of the upper and lower plates is 0 .. when the working ratio is r (r = final thickness / initial thickness).
Even if it is 866 / r or more, there is no effect.

That is, if h is made thicker than this,
The cost increases only by increasing the size of the rolled material.

From the magnetic performance, the workability of the rolled material is required to be 30% or more, preferably 70 to 80%. At 80% or more of processing, the orientation of particles that have been aligned evenly begins to be disturbed, and the magnetic performance deteriorates.

From the above, the initial capsule thickness h is h /
It is sufficient for a to be 4, and even if the thickness is made thicker, the effect against the swelling pressure does not become large, and only the cost increases.

The above does not depend much on the material of the capsule if it can be rolled. For example, even if the material strength of the capsule is doubled in preparation for swelling, the deformation resistance immediately below the roll is also doubled, so that the swelling pressure generated is also doubled. This is because the ratio of the yield stress and the swelling pressure P is the same, and h / a is irrelevant.

Considering that the capsules are rolled at 1100 ° C., it is necessary to make the capsules having a melting point higher than that. It is preferable that the melting point is 1200 ° C. or higher. Furthermore, the capsules should be able to be rolled relatively easily. If a metal with a yield stress higher than necessary is used, not only will the rolling load increase, but also the load on the rolling mill will increase.
The amount of reduction per pass cannot be taken and sufficient orientation cannot be obtained. On the other hand, if the yield stress is lower than necessary, only the capsule will be deformed, and the amount of deformation necessary for the orientation of the magnet cannot be obtained. In addition, the shape of the magnet is also dulled. Therefore, the capsule contains 1w of carbon with an appropriate yield stress.
A low alloy steel of t% or less is desirable. Preferably 0.3w
Low carbon steel of t% or less is desirable.

It is desirable that the rolling speed is higher in consideration of productivity. If the roll peripheral speed is less than 1 m / min, the rolled material is cooled by the roll, the liquid phase is solidified, the substantial liquid layer is reduced, the orientation cannot be sufficiently performed, and the desired magnetic performance cannot be obtained. Furthermore, there is a risk that it may lead to illness.

In the rolling, a more uniform magnet is obtained by performing the reverse rolling from the flow of the liquid phase. Performing reverse rolling at a roll peripheral speed of 500 m / min or more puts a burden on the rolling mill and is not a good idea. Further, it is preferable to consider increasing the amount of reduction per pass rather than increasing the peripheral speed any more.

Considering the above conditions, h /
Various values of a were set, and h / a which can withstand the bulging pressure P was investigated. Rolling was performed at each temperature, and the presence or absence of cracks in the cross section of the magnet after rolling and swelling of the upper and lower plates were observed. As a result, the result as shown in FIG. 2 was obtained. In the figure, no cracks and no blisters are indicated by a circle, no cracks were observed but a blister is indicated by a triangle, and cracks or breaks during rolling are indicated by a cross. Further, the shape of the cross section of the rolled material is schematically shown in FIG.

When the value of h / a is 0.25 or more, the upper and lower plates after rolling are flat, and the magnet can be flat and crack-free. In addition, with the same 0.1, some swelling remains after rolling,
It shows that the upper and lower plates have been plastically deformed, but it can be done without breaking the magnet. If the ratio is less than 0.1, cracks may occur or the upper and lower plates may be broken during rolling. This tendency became more remarkable as the temperature was higher and the temperature was higher. From the above, h / a
It is understood that the value of is required to be 0.1 or more, preferably 0.25 or more.

Considering the material cost, the welding cost and the yield of the magnet in one rolling, it is obvious that h / a should be as small as possible.

The details of the present invention will be described below with reference to examples.

Example 1 Using an induction heating furnace in an argon atmosphere, an alloy having a composition of Pr ₁₇ Fe ₇₇ B _5.2 Cu _0.8 was melted and then cast in a copper mold. At this time, rare earth,
Iron and copper raw materials having a purity of 99.9% were used, and ferroboron was used as boron. As a result, a columnar crystal structure having an average grain size of 15 μm has a thickness of 20 mm and a width of 500.
A cast ingot having a size of mm × height 250 mm was obtained.

Next, an ingot sample having a width (thickness) of 16 mm, a length of 80 mm and a height of 38 mm was cut out from this cast ingot to prepare a billet. This billet is made of SS400 steel as shown in Table 1 (0.17 wt% carbon content,
It was placed in a capsule of 0.3 wt% of silicon and 1.56 wt% of manganese, and was evacuated and sealed. The symbols are shown in FIG.

[0051]

[Table 1]

The capsule was made by welding each edge of each steel plate. Welding is checked by measuring the leak value of the capsule with a helium leak detector, and measuring 1 × 10 ⁻⁸ torr ·
It was confirmed that it was 1 / s or less. Make a hole for evacuation in the capsule, and in the vacuum chamber, 2 × 10 ^-4
After keeping the pressure below torr for 1 hour, the hole was sealed with an electron beam and the inside of the capsule was evacuated. The electron beam welds were color checked and confirmed to be free of defects. Prepare 4 capsules each, 800, 900, 1000, 1
Rolling was performed at each temperature of 100 ° C. The heating was performed in an electric furnace in the air for 1 hour, and reheating was performed for 15 minutes for each rolling pass.
The rolling roll has a diameter of 300 mm. In the pass schedule, rolling with a workability of 30% is performed four times in reverse, and the total workability is 76%.
And The average roll peripheral speed is 25 m / min.

After rolling, it was returned to the furnace at each temperature, and after the rolled material reached each heating temperature, it was cooled in the furnace. It took 50 hours to reach 200 ° C.

The results are shown in FIG. The adhesiveness of the multi-billet ones was good, and the effect of the capsule size was not observed. In the figure, no cracks, no swelling, no waviness are indicated by a circle, blisters, no waviness, no cracks are indicated by a triangle, and cracks or breaks during rolling are indicated by an x mark. The dotted line is broken to indicate the boundary with or without swelling. Further, the shape of the cross section of the rolled material is schematically shown in FIG. FIG. 4A is a schematic view of what is taken in a healthy shape, FIG. 4B is what is swollen and cracked, and FIG.

When the value of h / a was 0.25 or more, the upper and lower plates after rolling at each temperature were flat as shown in FIG. 3 (a), and the magnets could be flat and crack-free. . In addition, 0.
In No. 1, it was shown that some blisters remained after rolling and the upper and lower plates were plastically deformed. However, the magnet was made without being revealed. If the ratio is less than 0.1, as shown in FIGS. 3 (b) and 3 (c), cracks are formed or the upper and lower plates are broken during rolling.
This tendency became more remarkable as the liquid temperature increased and the temperature increased.

From the above, it is understood that the value of h / a needs to be 0.1 or more, preferably 0.25 or more.

With the above-mentioned structure, a large-sized magnet can be produced with good yield without cracking.

Example 2 An ingot of the same composition and the same size was obtained by the same method as in Example 1. From this, an ingot sample with a width (thickness) of 16 mm and a length of 80 mm is cut out to form a billet, the height is adjusted, and one to three billets are combined to form a capsule having a length of 160 mm with the dimensions shown in Table 2. I put it in. The material of the capsule is SS
400 (0.18 wt% carbon, 0.21 wt% silicon,
Manganese 0.95 wt%). In the same manner as in Example 1, the confirmation of welding, the evacuation, and the rolling were performed. The symbols in the table are shown in FIG.

[0059]

[Table 2]

The rolling temperature was 1000 ° C., and other conditions were the same as in Example 1.

After the rolling, the cut surface was observed and the magnetism was measured by a BH tracer.

The results are shown in Table 3. In the table, the magnet height ratio is the ratio of height / charging height when the entire black scale is taken when the entire width is taken in the lengthwise 15 mm band in the central portion in the length direction after rolling. .

[0063]

[Table 3]

In Table 3, since the workability is 76%, the magnet height ratio is a theoretical value of 0.24, and the difference from 0.24 can be regarded as the difference in the polishing amount.

From Table 3, as shown in Table 2, even if W / H is 1.5 or more, and h / a is 0.1, swelling or waviness that may lead to cracking occurs even if the performance appears. It can be seen that the yield of products is reduced. Furthermore, h /
When a is less than 0.1 and W / H is less than 1, cracking occurs and performance is not obtained.

From the above results, by setting h / a to 0.25 or more and W / H to 1.5 or more, cracks and swelling and waviness of the capsule are eliminated, and a high-performance large magnet with high yield is obtained. You can see that you can get it.

Example 3 By the same method as in Example 1, an ingot of the same composition and the same size was obtained. From this, an ingot sample having a width (thickness) of 16 mm and a length of 80 mm is cut out, the height is adjusted, two or three billets are combined, and h / a is 0.05 to 1 and h / b is 0.15. ~
Capsules similar to those in Example 1 were prepared and rolled by changing each within the range of 3.5. Rolling temperature is 1000 ℃
And Other conditions are the same as in the first embodiment.

After rolling, it was returned to the furnace, and after it was confirmed that the rolled material had become 1000 ° C., it was controlled and gradually cooled in the furnace. 5 ° C / m
It was cooled to 200 ° C. at an in-steady slow cooling rate. After cooling with air, when the temperature reached room temperature, the magnet was taken out. The appearance and cut surface of the magnet were observed.

The results are shown in FIG. The symbols o, Δ, and x and the dotted line have the same meanings as in Example 1. From this figure, as in the prior art, when h / b of the capsule is 0.2 or less, cracking that seems to have occurred during slow cooling occurred.
Even if b is 0.2 or more, cracking occurs when h / a is 0.1 or less.

From the above results, by setting h / a to 0.25 or more and h / b to 0.2 or more, cracks during rolling can be reduced,
It can be seen that the swelling and waviness of the capsule are eliminated, and cracks during slow cooling can be prevented, and a large magnet can be obtained with a high yield.

Example 4 By the same method as in Example 1, an ingot of the same composition and the same size was obtained. Next, from this cast ingot, width (thickness) 17.5 mm x length 250 m
An ingot sample of m × high 225 mm was cut out and used as a billet. 6 billets are arranged in the thickness direction, and SS
400 steel plate (carbon content 0.05 wt%, silicon 0.01 w
t%, manganese 0.23 wt%) to cover six capsules. Each edge of the steel sheet was welded, leak-checked and vacuum-sealed in the same manner as in Example 1. As shown in FIG. 6, the outside of the capsule is made of SS400 (with a carbon content of 0.16).
wt%, silicon 0.29 wt%, manganese 1.52 wt
%) And each edge was welded to form a triple capsule. The outermost shape is 1000 mm x 400 mm x 17
00 mm. Two types of capsule size were prepared as shown in Table 4, and after hot rolling, the cut surface was observed. Rolling
Heated at 1000 ℃ soaking for 8 hours, 345 → 290 → 2
The pass schedule was 35 → 185 → 145 → 120 → 100 (working rate 75%). Rolling roll diameter is φ1
200 mm. The peripheral speed is 45 m / min. Reheating on the way between each pass was not performed. Immediately after completion of rolling, the product was placed in a slow cooling box and cooled to 200 ° C. for 120 hours.

[0072]

[Table 4]

The capsules are called the first, second and third capsules from the inside. As a result of observation of the cut surface, Example,
In both Comparative Examples, the upper and lower plates of the first capsule were thin and indistinguishable. However, in the comparative example, swelling and partial breakage were observed on the upper and lower plates of the second capsule, and swelling of the upper and lower plates of the third capsule, separation and emptying of the second and third capsules were observed. Perhaps because of this, large irregularities on the surface of the inner magnet were observed.

The rolled material of this example is partially composed of the second and third parts.
Although the separation of the capsules was observed, it was not as empty as the comparative example. The magnet was taken out soundly.

In the comparative example, h / a and h / c are both less than 0.1, and plastic deformation occurs in each of the first, second, and third capsules, which causes the magnet to be broken, resulting in a large amount. Roughness was generated and the yield of magnets deteriorated. On the other hand, in the present embodiment, the h ₂ / c ₁ of the second capsule is set to 0.
When it is 25 or more, the swelling of the upper and lower plates of the second capsule can be suppressed, and as a result, the swelling of the third capsule can be suppressed even when h ₃ / c ₂ is less than 0.1, and the soundness is uniform. It can be seen that various rolling was performed.

From the above results, even in the case of multiple capsules, at least one capsule has an h / c of 0.1 or more, preferably 0.25 or more, so that cracks and swelling and waviness of the capsules are eliminated and the yield is improved. It can be seen that a large magnet can be obtained.

[0077]

The following effects can be obtained by adopting the structure of the present invention.

(1) Large magnets having high mechanical strength, which cannot be obtained by the sintering method, can be stably produced.

(2) From the case of the conventional hot working method,
As a result, it is possible to prevent the magnet surface from becoming uneven, thereby significantly improving the yield and reducing the cost.

(3) Since there is no risk of capsule breakage, it can be processed safely in the atmosphere, resulting in high production efficiency and cost reduction.

(4) Since there is no unevenness on the surface of the magnet, the work of removing unnecessary black skin is minimized, the number of man-hours for secondary processing can be reduced, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a conceptual cross-sectional view near a rolling roll for explaining the present invention.

FIG. 2 is a graph showing temperature and h / a in the example of the present invention.

FIG. 3 is a schematic view of a slit for explaining an embodiment of the present invention. (A) Rolled material cross section in a sound state. (B) Rolled material cross section with swelling and cracking. (C) Cross-section of rolled material with capsule fracture.

FIG. 4 is an assembled sectional view of an alloy and a capsule for explaining the present invention.

FIG. 5 is a graph showing h / b and h / a in the example of the present invention.

FIG. 6 is a schematic cross-sectional view of multiple capsules according to an embodiment of the present invention.

[Explanation of symbols]

 1: Rolling roll 2: Alloy 3: Capsule top and bottom plate 31: First capsule top and bottom plate 32: Second capsule top and bottom plate 33: Third capsule top and bottom plate 4: Arrow indicating rolling direction 5: Arrow indicating rolling direction 6: Capsule Horizontal plate 7: Bulging 8: Weak 9: Capsule rupture portion 10: Weld groove

Claims (8)

[Claims] 1. An alloy containing R (where R is at least one of rare earth elements including Y), Fe and B as a basic component of a raw material is melted and cast into a metal capsule having a melting point of 1200 ° C. or higher. , Sealed, 800-110 per capsule
The alloy ingot is heated to a temperature of 0 ° C., and the alloy ingot is hot-rolled together with the capsule in a semi-molten state having a liquid phase / solid phase volume ratio of 5% to 40%,
In the method for producing a rare earth permanent magnet for magnetically anisotroping the alloy, the size of the metal capsule is a, the width of the alloy ingot is a, and the thickness of the metal capsule in the pressing direction is h and h.
And the ratio h / a of these is 0.1 to 4, a method for producing a rare earth permanent magnet. 2. The method for producing a rare earth permanent magnet according to claim 1, wherein the alloy ingot is composed of a plurality of ingots. 3. When the width of the metal capsule is W and the height is H, the ratio W / H is 1.5 or more, and the h / a is 0.1 to 4. And a method of manufacturing a rare earth permanent magnet. 4. The ratio h / b to the upper and lower plate thickness of the capsule is 0.2 or more, and h / a is 0.1 to 4, where b is the height of the alloy ingot. A method for producing a rare earth permanent magnet, characterized by: 5. The multiple capsules (n
In the case where the stacking n is a natural number of n> 2), the upper and lower plate thickness of the i-th capsule counted from the inside is h, (i-1)
When the width of the th capsule is c (i is a natural number with n ≧ i> 1), there is at least one capsule having a h / c ratio of 0.1 to 4 and a rare earth permanent. Magnet manufacturing method. 6. The material of the capsule is carbon steel having a carbon content of 1 wt% or less.
A method for producing the described rare earth permanent magnet. 7. The method for producing a rare earth permanent magnet according to claim 1, wherein the workability of rolling is 70% to 80%. 8. The average roll peripheral speed during hot rolling is 1 to 5
It is 00 m / min, Claim 1- Claim 7 characterized by the above-mentioned.
A method for producing the described rare earth permanent magnet.