JPH0422104A - Method of manufacturing permanent magnet - Google Patents

Abstract

PURPOSE:To manufacture a permanent magnet by a method wherein an alloy comprising principal components such as R(a rare-earth element containing Y), Fe, and B is melted and cast, next a cast ingot is heat-processed at a specific temperature, and next it is heat-treated at a predetermined temperature for a predetermined time. CONSTITUTION:In a method of manufacturing a permanent magnet, R (R is at least one kind of rare-earth element containing Y), Fe, and B are used as raw material principal components, an alloy comprising the principal components is melted and cast, next a cast ingot is heat-processed at a temperature of higher than 500 deg.C, and next it is heat-treated in a temperature range of 250 to 1100 deg.C for more than 4 hours. The rare-earth is employed by combining one or more kinds of Y, La, Ce, Pr, and Nd, etc., with each other. Since the highest magnetic performance is obtained by the existence of Pr, practically the Pr, the alloy of Pr-Nd, or the alloy of Ce-Pr-Nd, etc., is employed. A small quantity of heavy rare-earth element, for example, Dy, Tb is effective in improvement of the coercive force.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a permanent magnet having magnetic anisotropy due to mechanical orientation, and in particular a method for manufacturing a permanent magnet having magnetic anisotropy due to mechanical orientation. )+Fe+B as the basic raw material components.

[Prior art] Permanent magnets are one of the important electrical and electronic materials used in a wide range of fields, from various household electrical products to peripheral terminal equipment for large computers, and are becoming more and more compact in recent years. With the demand for higher efficiency, permanent magnets are also required to have increasingly higher performance.

A permanent magnet is a material that generates a magnetic field without supplying electrical energy from the outside, and one that has a large coercive force and a high residual magnetic flux density is suitable.

Typical permanent magnets currently in use are alnico cast magnets, ferrite magnets, and rare earth-transition metal magnets, especially rare earth-transition metal magnets.
Co-based permanent magnets and R-Fe-B-based permanent magnets have been extensively researched and developed as permanent magnets with extremely high coercive force and energy product.

Conventionally, there are the following methods for manufacturing these R-Fe-B-based high-performance anisotropic permanent magnets.

(1) First, JP-A-59-46008, M, S
agaWa.

S., Fujimura, N., Togalla, H., Ya.
mamoto and Y, Matsu-ura; J,
Appl, Phys, Vol. 55(6), 15 Ma.
rch 1984. p2083 etc. has an atomic percentage of 8
A permanent magnet characterized by being a magnetically anisotropic sintered body consisting of ~30% R (where R is at least one rare earth element including Y), 2~28% B, and the balance Fe is a powder metallurgy permanent magnet. It is disclosed that it is manufactured by method-based sintering.

In this sintering method, an alloy ingot is produced by melting and casting, and then pulverized to obtain magnetic powder with 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 complete a molded product. The compact is sintered in argon at a temperature of around 1100° C. for 1 hour and then rapidly cooled to room temperature.

After sintering, the permanent magnet is heat-treated at a temperature of around 600'C to further improve its coercive force.

Regarding the heat treatment of this sintered magnet, Japanese Patent Application Laid-Open No. 61-2
No. 17540, Japanese Unexamined Patent Publication No. 82-165305, etc. disclose the effects of multistage heat treatment.

(2) JP-A-59-211549, R, W, Le
e; Appl.

Phys, Lett, Vol, 46(8), 15 A
pril 1985. P790 discloses an R-Fe-B magnet in which fine pieces of melt-spun alloy ribbon with a very fine crystalline magnetic phase are bonded together with a resin.

This permanent magnet is manufactured by making a quenched thin piece with a thickness of about 30 μm using a quenched ribbon manufacturing apparatus used for manufacturing an amorphous alloy, and then kneading the thin piece with a resin and press-molding it.

(3) JP-A-60-100402, R, W, Le
e; Appl.

Phys, Lett, Vol, 46(8), 15 Ap
ril 1985. For p790, the quenched flakes used in the method (2) above are processed into a dense and anisotropic R-Fe-B magnet by a method called a two-step hot pressing method in a vacuum or an inert atmosphere. It is disclosed that it can be obtained.

(4) Japanese Patent Application Laid-Open No. 62-276803 states that R (where R is at least one rare earth element including Y) 8 to
30 at%, B2~28w% + Co50 at% or less,
After melting and casting an alloy consisting of 115 at. A rare earth-iron permanent magnet is disclosed in which the cast alloy is made magnetically anisotropic by orienting its crystal axis in a specific direction.

[Problems to be Solved by the Invention] The conventional methods for manufacturing R-Fe-B permanent magnets (1) to (4) above have the following drawbacks.

The manufacturing method for permanent magnets in (1) requires that the alloy be made into powder, but since R-Fe-B alloys are highly active against oxygen, making them into powder will cause unnecessary oxidation. becomes intense, and the oxygen concentration in the sintered body inevitably becomes high.

Also, when compacting the powder, a compacting aid, such as zinc stearate, must be used, which is removed beforehand during the sintering process, and the dispersion in the compacting aid is limited to the size of the magnet. This carbon remains in the form of carbon, which is undesirable because it significantly reduces the magnetic performance of the R-Fe-B magnet.

The molded body after press molding with the addition of a molding aid is called a green body, which is extremely brittle and difficult to handle.

Therefore, a major drawback is that it takes a considerable amount of effort to arrange them neatly in the sintering furnace.

Because of these drawbacks, generally speaking, manufacturing RFe-B sintered magnets not only requires expensive equipment, but also the manufacturing method has poor production efficiency, which ultimately increases the manufacturing cost of the magnet. becomes high. Therefore, it is not possible to take advantage of the advantages of R-Fe-B magnets, which have relatively low raw material costs.

Next, the permanent magnet manufacturing methods (2) and (3) use a vacuum melt spinning device, but this device currently has very low productivity and is expensive.

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

The method (3) for manufacturing permanent magnets is a unique method of using hot press in two stages, but it cannot be denied that it is inefficient when considering actual mass production.

Furthermore, in this method, at high temperatures, for example, 800° C. or higher, the crystal grains become significantly coarsened, resulting in an extremely low coercive force iHc, making it impossible to produce a practical permanent magnet.

The method of manufacturing permanent magnets in (4) does not involve a powder process and requires only one step of hot pressing, so it is the manufacturing method that simplifies the manufacturing process the most and can reduce costs, but the magnetic properties There was a problem that it was lower than the sintering method.

The present invention is intended to solve the above-mentioned drawbacks of the prior art, particularly the drawback (4) in terms of performance of permanent magnets, and its purpose is to provide a high-performance, low-cost manufacturing method for permanent magnets. It's about doing.

[Means for Solving the Problems] The method for manufacturing a permanent magnet of the present invention uses R (where R is at least one rare earth element including Y).

Fe and B are used as the basic raw material components, and the alloy containing the basic components is melted and cast, and then the cast ingot is
Hot worked at a temperature above 250~1100°
It is characterized by heat treatment at a temperature of C for 4 hours or more.

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

Rare earths include Y, La, Ce, Pr,
Nd.

Sm, Eu, Gd, Tb, Dy,
Candidates include Ho, Er, Tm, Yb, and Lu, and one or more of these may be used in combination. The highest magnetic performance is obtained with Pr, so Pr, Pr-Nd alloy, Ce-Pr-N
d alloy etc. are used. Small amounts of heavy rare earth elements, e.g. py
, 'rb, etc. are effective for improving coercive force.

The main phase of the R-Fe-B magnet is R2Fe+aB.

Therefore, if R is less than 8 at %, the above-mentioned compound is no longer formed and high magnetic properties cannot be obtained. On the other hand, if R exceeds 30 atomic %, the nonmagnetic R-rich phase increases and the magnetic properties deteriorate significantly. Therefore, the appropriate range of R is 8 to 30 atomic %. However, for high residual magnetic flux density, preferably R
8 to 25 atom % is suitable.

B is an essential element for forming the R2Fe+aB phase, and if it is less than 2w%, it becomes a rhombohedral R-Fe system, so a high coercive force cannot be expected. Also, if it exceeds 28 children%, it is B.
The amount of non-magnetic phase rich in ions increases, and the residual magnetic flux density decreases significantly. However, in order to obtain a high coercive force, B88 atoms or less are preferable, and if it is more than that, fine R2Fe1
It is difficult to obtain the 4B phase, and the coercive force is small.

The temperature during hot working is desirably higher than the recrystallization temperature, preferably 500°C in the R-Fe-B alloy of the present invention.
That's all.

The heat treatment temperature was set at 25°C to diffuse the primary Fe.
The temperature is preferably 0°C or higher, and the R2FezB phase is] 100°C
If the temperature is higher than that, the grains will grow rapidly and the coercive force will be lost, so a temperature lower than that is preferable.

The heat treatment time is required to be at least 4 hours in order to obtain a large coercive force through the diffusion of primary Fe and the cleaning of the grain boundary phase, and even if it is extended to 100 hours, the deterioration due to being too long is ignored. can.

Next, examples of the present invention will be described.

[Example] [Example 1] Using an induction heating furnace in an argon atmosphere, Pt+sNd
2Fe7gB5. An alloy having the composition sCu+, s was melted and then cast. At this time, rare earth, iron, and copper raw materials with a purity of 99.9% were used, and boron was ferroboron.

Next, a cylindrical sample was cut out from this cast ingot, an iron ring was fitted around it, and the sample was hot pressed at 950°C in an argon atmosphere to a working degree of 80%. The press pressure at this time is 0.2 to 0.9 tons
/am2, and the strain rate is 10-' to 10-'
/see.

During this hot working, the axis of easy magnetization of the crystal was oriented parallel to the direction in which the alloy was pressed, creating magnetic anisotropy.

Thereafter, it was heat treated at 1000°C for 3 hours, then at 500°C for 1 hour, cut and polished, and its magnetic properties were measured.

The magnetic properties of this magnet are shown in Table 1 along with the values in the case without heat treatment as a comparative example.

All magnetic properties are B- after pulse magnetization at 40 kOe.
It was measured using an H tracer.

As shown in Table 1, it is clear that the magnet of the present invention has improved coercive force and maximum energy product compared to the case without heat treatment.

Table 1 [Example 2] Pr+sTb+, 5FeseCo+aBa, sCu+,
Alloy with a composition of + (sample 7° 2a) and Pr+@Ndy
Alloy with composition Fevs, 5BsCu+, eGaa, s (sample 7'le 2b) and Ce+, aNdx, 5DyzF
ers, sBs, 3Cu1. An alloy having the composition aAls, t (Pumbul 2c) was melted and cast in the same manner as in Example 1 to obtain a cast ingot.

These cast ingots were then placed in iron capsules and sealed. This was hot-rolled at 9756C with a working degree of 15% in the air four times, and then hot-rolled with a working degree of 20% in the air three times to reach a final working degree of 73%. .

Thereafter, these rolled ingots were heat treated under the following conditions.

Condition 1: After heat treatment at 950°C for 1 hour, it was taken out from the heat treatment furnace and cooled in air.

Condition 2: After heat treatment at 950'C for 2 hours, it was taken out from the heat treatment furnace and cooled in air.

Condition 3: After heat treatment at 950°C for 2 hours, take out from the heat treatment furnace and air cool, then heat treat at 550°C for 2 hours,
Remove from heat treatment furnace and cool in air.

Condition 4: After heat treatment at 950'C for 4 hours, it was taken out from the heat treatment furnace and cooled in air.

Condition 5: After heat treatment at 950°C for 2 hours, controlled cooling was performed so that the temperature decreased linearly to 300°C over 2 hours, and the product was taken out of the heat treatment furnace and cooled in air.

Condition 6: After heat treatment at 950°C for 4 hours, it was taken out from the heat treatment furnace and cooled in air, and then after heat treated at 550°C for 4 hours, it was taken out from the heat treatment furnace and cooled in air.

The coercive force value of each sample after these six types of heat treatment was
Shown in the table.

Table 2 It can be seen that heat treatment is effective in improving coercive force.

From the above examples, it can be seen that a permanent magnet whose basic raw materials are R (where R is at least one rare earth element including Y), Fe, and B can be made anisotropic by hot working at 500°C or higher. , It is clear that a heat treatment at 250 to 1100°C for 4 hours or more shows a high coercive force, and the highest (BH)max exceeds 30 MGOe.

[Effects of the Invention As described above, the method for manufacturing a permanent magnet of the present invention includes (1) c.
The axial orientation rate can be increased, the residual magnetic flux density Br can be significantly increased, the coercive force iHc can be increased by making the crystal grains finer, and the maximum energy product (B
[()max could be significantly improved.

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

(3) Compared to conventional sintering methods, processing man-hours and production investment can be significantly reduced.

(4) Compared to the conventional method of producing magnets using melt spinning, it is possible to produce magnets with high performance and at low cost.

(5) Magnetic properties can be improved compared to conventional hot-processed magnets.

that's all Applicant: Seiko Epson Corporation

Claims (1)

[Claims] (1) R (where R is at least one rare earth element including Y), Fe, and B are used as the basic raw material components, and the alloy containing the basic components is melted and cast, and then the cast ingot is
Hot worked at a temperature of 00℃ or higher and then 250~11
A method for producing a permanent magnet, characterized by heat treatment at a temperature of 00°C for 4 hours or more.