JPH05135920A - Manufacture of permanent magnet - Google Patents

Abstract

PURPOSE:To realize low-cost and high-performance in R-Fe-B permanent magnet manufacture. CONSTITUTION:The basic components of the material are R (R is at least one kind of rare earth elements including Y), Fe and B. Composition of it expressed in atom % is RxFeyBzM100-x-y-z (where M is at least one of the elements other than R, Fe and B, 100-x-y-z=0). Here, the alloy specified by x-2z>0, 2<=100-17z<=35 is melted and molded. More than two molded ingots are put in a metal capsule whose melting point is above 600 deg.C and then sealed. Then, hot working is done between 500-1100 deg.C. When the molded ingots are put in the metal capsule as above, columnar crystal development direction of ingots are all aligned and then sealded up fort hot working at 500-1100 deg.C.

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 permanent magnet having magnetic anisotropy due to mechanical orientation, especially R (where R is
Is at least one of rare earth elements including Y), Fe,
The present invention relates to a method for producing a permanent magnet containing B as a raw material basic component.

[0002]

2. Description of the Related Art Permanent magnets are one of the important electric and electronic materials used in a wide range of fields from various household electric appliances to peripheral terminals for large computers.
With the recent demand for miniaturization and high efficiency of electrical products,
Permanent magnets are also required to have higher performance.

The permanent magnet is a material for generating a magnetic field without supplying electric energy from the outside, and a material having a large coercive force and a high residual magnetic flux density is suitable.

Typical permanent magnets currently in use are alnico type cast magnets, ferrite magnets and rare earth-transition metal type magnets, especially R-Co type permanent magnets which are rare earth-transition metal type magnets. The R-Fe-B system permanent magnet has been extensively researched and developed as a permanent magnet having an extremely high coercive force and energy product.

Conventionally, there are the following methods for producing these R—Fe—B type high-performance anisotropic permanent magnets.

(1) First, Japanese Patent Laid-Open No. 59-46008 and M. Saga
wa, S.Fujimura, N.Togawa, H.Yamamoto and Y.Matsuura; J.
Appl.Phys.Vol.55 (6), 15 March 1984, p2083, etc., 8 to 30% R (where R is at least one rare earth element including Y) and 2 to 28% B in atomic percentage. It is disclosed that a permanent magnet characterized by being a magnetic anisotropic sintered body composed of Fe and the balance Fe is manufactured by sintering based on the powder metallurgy method.

In this sintering method, an alloy ingot is produced by melting and casting and crushed to obtain a magnetic powder having an appropriate particle size (several μm). The magnetic powder is kneaded with a binder, which is a molding aid, and press-molded in a magnetic field to form a molded body. The molded body is sintered in argon at a temperature of around 1100 ° C for 1 hour,
Then it is rapidly cooled to room temperature. After sintering, the coercive force of the permanent magnet is further improved by heat treatment at a temperature of around 600 ° C.

Regarding the heat treatment of this sintered magnet, Japanese Patent Laid-Open No. 61-217540, Japanese Patent Laid-Open No. 62-165305, etc.
The effect of multi-step heat treatment is disclosed.

(2) Japanese Patent Laid-Open No. 59-211549 and RWLee;
Appl. Phys. Lett. Vol. 46 (8), 15 April 1985, p790 describes a resin-bonded fine piece of melt-spun alloy ribbon with a very fine crystalline magnetic phase.
Fe-B magnets are disclosed. This permanent magnet is manufactured by a quenching ribbon production apparatus used for producing an amorphous alloy, by making a quenching thin piece having a thickness of about 30 μm, kneading the thin piece with a resin and press-molding.

(3) Japanese Patent Laid-Open No. 60-100402 and RWLee; A
ppl. Phys. Lett. Vol. 46 (8), 15 April1985, p790 describes the quenched thin piece used in the method of (2) above in a method called a two-step hot pressing method in vacuum or in an inert atmosphere. It is disclosed to obtain a dense and anisotropic R-Fe-B magnet.

(4) In JP-A-62-276803, R (where R is at least one of rare earth elements including Y) 8
~ 30 atom%, B 2 ~ 28 atom%, Co 50 atom% or less, A
After melting and casting an alloy containing 15 atomic% or less and the balance of iron and other impurities unavoidable in production, the cast ingot is subjected to hot working at a temperature of 500 ° C. or more to refine the crystal grains and Disclosed is a rare earth-iron-based permanent magnet characterized by orienting the crystal axis in a specific direction to magnetically anisotropy the cast alloy.

In addition, in the method of manufacturing this hot-worked magnet,
Japanese Patent Laid-Open No. 2-252218 discloses that a plurality of cast ingots are placed in a metal capsule and hot-rolled. Further, in the case of rolling a plurality of cast ingots in combination, it is necessary to grind and polish the cast ingots so that the surface roughness Rmax is 50 μm or less, and then hot-roll them in a metal capsule. -095700.

[0013]

The conventional methods for manufacturing R-Fe-B based permanent magnets (1) to (4) above have the following drawbacks.

The method of producing a permanent magnet of (1) essentially requires that the alloy be made into powder. However, since the R-Fe-B alloy is very active with respect to oxygen, it cannot be powdered. Oxidation becomes excessive, and the oxygen concentration in the sintered body inevitably increases.

When molding the powder, it is necessary to use a molding aid such as zinc stearate, which is removed beforehand in the sintering process. However, it remains in the form of carbon in the magnet body, and this carbon remarkably deteriorates the magnetic performance of the R-Fe-B magnet, which is not preferable.

The green body is a green body after press-molding by adding a molding aid, which is very brittle and difficult to handle. Therefore, it takes a great deal of time and effort to put them neatly in the sintering furnace, which is a big drawback.

Due to these drawbacks, generally speaking, not only expensive equipment is required for producing an R--Fe--B system sintered magnet, but also the production method is inferior in production efficiency. Eventually, the manufacturing cost of the magnet increases. Therefore, it is not possible to take advantage of the advantages of the R-Fe-B magnets, which have relatively low raw material costs.

Next, in the manufacturing methods of the permanent magnets of (2) and (3), a vacuum melt spinning apparatus is used, but this apparatus is currently very poor in productivity and expensive.

Since the permanent magnet of (2) is isotropic in principle, it has a low energy product, the squareness of the hysteresis loop is poor, and it is disadvantageous in terms of temperature characteristics and use.

The method (3) for producing a permanent magnet is a unique method in which hot pressing is used in two steps.
It cannot be denied that it is inefficient considering mass production. Further, in this method, the crystal grains are remarkably coarsened at a high temperature, for example, 800 ° C. or higher, and the coercive force iHc is extremely lowered by this, and it cannot be a practical permanent magnet.

The method of manufacturing the permanent magnet of (4) does not include a powder process and requires only one step of hot pressing, so that the manufacturing process is most simplified and the mass production cost can be reduced. , The magnetic properties are slightly lower than those of the sintering method,
When hot working by combining two or more ingots,
Adhesion between the ingots depends on the surface condition of the ingots, and there is a problem that cracking of the magnet occurs at the joint surface of the ingots.

The present invention has the above-mentioned drawbacks of the prior art, particularly (4).
The problem to be solved by the invention is to provide a method of manufacturing a permanent magnet with high performance and low cost.

[0023]

In the method for producing a permanent magnet of the present invention, R (where R is at least one of rare earth elements including Y), Fe and B are used as raw material basic components and expressed in atomic%. Its composition is R _x Fe _y B _z M _100-xyz (where M is at least 1 of elements other than R, Fe and B).
, Including the case where 100-x-y-z = 0), x-2z> 0 2 ≤ 100-17z ≤ 35 is melted and cast to obtain the obtained casting. The invention is characterized in that two or more ingots are placed in a metal capsule having a melting point of 600 ° C. or more, sealed, hot-worked at a temperature of 500 to 1100 ° C., and then heat-treated at 250 to 1100 ° C. Further, in the case of an ingot having a structure in which columnar crystals have developed, in order to further obtain the effect of preventing cracks,
When the cast ingot is put into a metal capsule, the columnar crystal growth directions of the ingot are put in the same direction, sealed, and then 50
Hot working at a temperature of 0 to 1100 ° C, then 250
Characterized by heat treatment at ˜1100 ° C.

Further, in order to further increase the coercive force and the performance, it is characterized in that after the hot working, the heat treatment is carried out at 750 to 1100 ° C. and then at the temperature of 250 to 750 ° C.

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

As rare earth elements, Y, La, Ce, Pr,
Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
m, Yb, and Lu are listed as candidates, and one or more of these are used in combination. Since the highest magnetic performance can be obtained with Pr, practically, Pr, P
An r-Nd alloy, a Ce-Pr-Nd alloy, etc. are used.
A small amount of heavy rare earth element, such as Dy or Tb, is effective for improving the coercive force.

The main phase of the R-Fe-B magnet is R ₂ Fe ₁₄ B.
Is. Therefore, if R is less than 8 atomic%, the above compound is no longer formed and high magnetic properties cannot be obtained. On the other hand, when R exceeds 30 atom%, the nonmagnetic R-rich phase is increased and the magnetic properties are remarkably deteriorated. Therefore, the range of R is suitably 8 to 30 atomic%. However, for high residual magnetic flux density, R8 to 25 atomic% is preferable.

B is an essential element for forming the R ₂ Fe ₁₄ B phase, and if it is less than 2 atomic%, a rhombohedral R-Fe system cannot be obtained, so that a high coercive force cannot be expected. On the other hand, if it exceeds 28 atomic%, the non-magnetic phase rich in B is increased and the residual magnetic flux density is significantly lowered. However, in order to obtain a high coercive force, B8 atom% or less is preferable, and if it is more than that, fine R ₂
It is difficult to obtain the Fe ₁₄ B phase, and the coercive force is small.

Within the above preferable composition range, the composition of the alloy is R _x Fe _y B _z M _100-xyz (where M is at least 1 of elements other than R, Fe and B).
It is desirable that the composition range is defined by x-2z> 0 2 ≦ 100-17z ≦ 35 when represented by the formula (including the case where 100-x-y-z = 0). x-2z ≦
In the composition range of 0, R is not contained in the grain boundary phase, which hinders deformation during hot working, which causes deterioration of magnetic properties and causes cracking. Is a magnetic phase
Since the R ₂ Fe ₁₄ B phase is hard and brittle, it is necessary to have a low-melting-point grain boundary phase for effective orientation. But,
In the case of 100-17z> 35, the ratio of the grain boundary phase is too high, the ratio of the R ₂ Fe ₁₄ B phase becomes small, and a high residual magnetic flux density cannot be obtained, and the magnetic performance deteriorates. On the other hand, in the case of 100-17z <2, the grain boundary phase amount is not sufficient for effective orientation and deformation is hindered, which causes deterioration of magnetic properties and cracking. Therefore, in order to prevent cracking due to hot working, obtain a good orientation of crystal axes, and obtain high magnetic properties, it is more desirable that the composition range is 2 ≦ 100−17z ≦ 35.

The temperature during hot working is preferably a recrystallization temperature or higher, and is preferably 500 ° C. or higher in the R—Fe—B type alloy of the present invention. And above 1100 ℃ R ₂ F
Since the e ₁₄ B phase rapidly grows to lose the coercive force, a temperature lower than that is preferable.

The heat treatment temperature is preferably 250 ° C. or higher for diffusing primary crystal Fe, and the R ₂ Fe ₁₄ B phase is 1100 ° C.
If the temperature is higher than 0 ° C, the grain size will be rapidly grown and the coercive force will be lost.

In the case of performing the heat treatment in two or more steps, the temperature in the first step is set to 750 so that the primary Fe diffuses quickly.
℃ or more is preferable, and the second stage is a temperature below the melting point of the R-rich phase at the grain boundary, that is, 750 ° C or less, preferably 250 ° C.
In the following, the effect of the heat treatment takes too much time, so more is preferable.

Next, examples of the present invention will be described.

[0034]

Example 1 An alloy having the composition shown in Table 1 was melted and cast in an argon atmosphere using an induction heating furnace.
At this time, raw materials of rare earth, iron and copper were used with a purity of 99.9% and ferroboron was used as boron. At this time, the ingot structure was not a structure in which columnar crystals were strongly developed, but a structure close to equiaxed crystals. This cast ingot was cut and polished into a size of 200L × 200H × 25T. The surface roughness Rmax of the ingot at this time is 3
It was 0 μm ≦ Rmax ≦ 45 μm.

Next, after washing these casting ingots with an organic solvent and arranging them five by 5 to make 200 L × 200 H × 125 W, they were placed in a 600 L × 450 H × 600 W SS41 steel capsule, deaerated and sealed. On the other hand, hot rolling was performed at a processing temperature of 975 ° C. At this time, hot rolling with a workability of 20% was performed twice in air, and then hot rolling with a workability of 30% was performed three times in air, so that the workability finally reached 78%. During this hot working, the easy axis of magnetization of the crystal was oriented so as to be parallel to the pressing direction of the alloy, and magnetic anisotropy was formed. After that, the sample cut out from this rolling ingot was subjected to a heat treatment at a temperature of 1000 ° C. for 20 hours in an Ar atmosphere furnace, and then subjected to 5 hours in the furnace.
Cooled to 00 ° C. The cooling rate at this time is 10 ° C./minute. After that, heat treatment was subsequently performed at 500 ° C. for 4 hours.

Table 2 shows the magnetic characteristics of these heat-treated samples and the lengths of boundaries visually observed at the four bonding surfaces between the ingots. The total length of the boundary is 3150 mm
And the magnetic characteristics are all 40 kOe and after pulse magnetization B
It was measured using a -H tracer.

[0037]

[Table 1]

[0038]

[Table 2]

The composition expressed in atomic% is R _x Fe _y B _z M _100-xyz (where M is at least 1 of elements other than R, Fe and B).
And including a case where 100-x-y-z = 0), the cracks are generated by the composition within the range defined by x-2z> 0 2 ≦ 100-17z ≦ 35. It can be seen that good adhesion can be obtained which can be prevented and the boundary cannot be visually observed. In addition, in the composition within this range, good magnetic performance is obtained.

Example 2 Alloys having the compositions shown in Table 3 were melted and cast in the same manner as in Example 1. At this time, casting was performed so that the ingot structure became a structure in which columnar crystals were strongly developed. The raw materials used had the same purity. All of these compositions are within the composition range defined by x-2z> 0, 2 ≦ 100-17z ≦ 35, which showed the effect in Example 1. This cast ingot was cut into a size of 25T by 200L × 200H and polished. The surface roughness Rmax of the ingot at this time is 1
It is about 00 μm. After washing this, 4 pieces are lined up for 200
L × 200H × 100W, 500L × 400H × 3
It was put into a capsule made of SS41 steel having a size of 20 W, which was then vacuum-sealed and hermetically sealed. At this time, two types were prepared: one in which the columnar crystal growth directions were aligned and combined (condition 1), and one in which the columnar crystal growth directions were combined at right angles to each other (condition 2). After this is heated to 950 ° C, hot rolling with a working rate of 30% is performed four times in the air, and finally the working rate is 76%.
I tried to become.

Thereafter, a sample was cut out from this rolled ingot, polished, and then heat-treated at 1020 ° C. for 20 hours in an Ar atmosphere furnace, and cooled to 400 ° C. at a rate of 15 ° C./min by gas cooling in the furnace. Then 500
Heat treatment at ℃ for 4 hours, room temperature up to 10 ℃ /
Cooled at a rate of minutes.

Table 4 shows the adhesion status of these samples after the heat treatment.

[0043]

[Table 3]

[0044]

[Table 4]

From the above examples, two or more cast ingots containing R (where R is at least one of rare earth elements including Y), Fe and B as basic raw material components are combined and placed in a metal capsule and heated. When performing hot rolling, atomic%
The composition represented by R _x Fe _y B _z M _100-xyz (where M is at least 1 of elements other than R, Fe and B)
(Including the case where 100-x-y-z = 0)), it is possible to prevent cracking during hot rolling by defining x-2z> 0 2 ≤100-17z ≤35. In the case of a cast ingot of an alloy that has good adhesion of more than one ingot and has a structure in which columnar crystals have further developed, when combining two or more ingots and putting them in a metal capsule, combine them so that the columnar crystal directions are aligned. It is clear that by doing so, cracking is eliminated and a stronger adhesive effect is obtained.

[0046]

As described above, the method for manufacturing a permanent magnet of the present invention has the following effects.

(1) The c-axis orientation ratio can be increased, the residual magnetic flux density Br can be remarkably increased, and the coercive force iHc can be increased by refining the crystal grains, and the maximum energy product (BH) I was able to improve max significantly.

(2) The cost is low because the manufacturing process is simple.

(3) Compared with the conventional sintering method, the processing man-hour and the production investment amount can be remarkably reduced.

(4) As compared with the conventional method of manufacturing a magnet by the melt spinning method, a magnet having high performance and low cost can be manufactured.

(5) As compared with the conventional hot-worked magnet, a large magnet without cracks can be manufactured.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor St. Arai 3-3-5 Yamato, Suwa-shi, Nagano Seiko Epson Corporation (72) Inventor Koji Akioka 3-3-5 Yamato, Suwa-shi, Nagano Seiko Epson Within the corporation

Claims (2)

[Claims] 1. R (where R is at least one of rare earth elements including Y), Fe and B as raw material basic components, and the composition expressed in atomic% is R _x Fe _y B _z M _100-xyz. (However, M is at least 1 of the elements other than R, Fe, and B.
And the case where 100-x-y-z = 0) is included), an alloy defined by x-2z> 0 2 ≦ 100-17z ≦ 35 is melted and cast, and the obtained casting is obtained. A permanent magnet characterized in that two or more ingots are placed in a metal capsule having a melting point of 600 ° C. or higher, sealed, hot-worked at a temperature of 500 to 1100 ° C., and then heat-treated at 250 to 1100 ° C. Production method. 2. When a cast ingot is put into a metal capsule, the columnar crystal growth directions of the ingot are put in the same direction, sealed, hot-worked at a temperature of 500 to 1100 ° C., and then at 250 to 1100 ° C. A method for producing a permanent magnet, characterized by heat treatment.