JPH0422105A - Method of manufacturing permanent magnet - Google Patents

Abstract

PURPOSE:To manufacture a permanent magnet having a high coercive force by a method wherein an alloy comprising principal components such as R (R is a rare-earth element containing Y), Fe, and B is melted and cast, an ingot is heat-processed at more than a specific temperature, next it is heat-treated at a specific temperature, and thereafter it is cooled at a specific cooling speed in specific range of temperature. CONSTITUTION:In a manufacturing method of a permanent magnet, R (R is at least 1 kind of rare-earth element containing Y), Fe, and B are 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, next it is heat-treated in a temperature range of 250 to 1100 deg.C, and thereafter it is cooled at a cooling speed less than 10 deg.C/min. in a range of 200 to 800 deg.C. The rare-earth is employed by combining one or more kinds of Y, La, Ce, Pr, Nd, etc., with each other. A temperature for heat-processing is desired to be higher than a re-crystallized temperature and preferably higher than 500 deg.C in the R-Fe-B system alloy of the present invention.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for producing a permanent magnet having magnetic anisotropy due to mechanical orientation, and in particular R (where R is at least one rare earth element including Y). ), Fe.

This invention relates to a method for producing a permanent magnet using B as a basic raw material component.

[Prior art] Permanent magnets are important electrical and electronic materials that are used in a wide range of fields, from various household electrical appliances to peripheral terminal equipment for large computers. 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 - Tokukai Sho F+! 1l-dRnnR compromise
M(UσUri.

S, Fujimura, N, Togawa, H, Yam.
amoto and Y, Matsu-ura; J,
Appl, Phys, Vol, 55(6), 15 M
arch 1984. p2083 etc. must be a magnetically anisotropic sintered body consisting of 8 to 30% R (at least one rare earth element including Y) in atomic percentage, 2 to 28% B, and the balance Fe. It is disclosed that a permanent magnet characterized by the following is manufactured by sintering based on a powder metallurgy method.

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, permanent magnets are heat-treated at a temperature of around 600°C to further improve their coercive force.

Regarding the heat treatment of this sintered magnet, Japanese Patent Application Laid-Open No. 61-2
The effects of multi-stage heat treatment are disclosed in Japanese Patent Laid-Open No. 17540, Japanese Patent Application Laid-open No. 165305/1983, and the like.

(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 A
pril 1985. For p790, obtain a dense and anisotropic R-Fe-B magnet by using the quenched flakes used in the method (2) above in a vacuum or in an inert atmosphere by a method called a two-step hot pressing method. is disclosed.

(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
30i atomic%, B2~28 atomic% + Co 5o atomic%
Hereinafter, after melting and casting an alloy consisting of 15 atomic percent or less of A-yu, and the balance consisting of iron and other impurities unavoidable in manufacturing,
The cast alloy is made magnetically anisotropic by hot working the cast ingot at a temperature of 500°C or higher to refine the crystal grains and orient the crystal axes in a specific direction. A rare earth-iron permanent magnet is disclosed.

[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 additional oxidation. The oxygen concentration in the sintered body inevitably increases.

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 poor 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 and can reduce mass production costs. There was a problem that the magnet was slightly lower than that of the sintering method, and cracks and chips occurred in the magnet after heat treatment.

The present invention solves the above-mentioned drawbacks of the prior art, particularly (4) the problem of the performance drawback and cracking of permanent magnets,
The purpose is to provide a high-performance, low-cost method of manufacturing permanent magnets.

[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 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 500°C or higher, and then heat treated at a temperature of 250 to 1100°C. After heat treatment, 200°C ~ 8
It is characterized by cooling the range of 00°C at a cooling rate of 10°C/min or less.

In other words, it was found that defects such as cracks and chips in magnets mainly occur during solidification and shrinkage of the grain boundary phase, and that defects can be avoided by slow cooling in the temperature range of 800°C to 200°C after heat treatment. .

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 in practice P r + P r N d alloy,
Ce-PrNd alloy or the like is used. A small amount of heavy rare earth elements such as Dy and 'rb are effective in improving coercive force.

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

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 for R is 8 to 301%. 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 2 atomic %, it becomes a rhombohedral R-Fe system, so a high coercive force cannot be expected. Moreover, when it exceeds 28 at %, the amount of B-rich nonmagnetic phase increases, and the residual magnetic flux density decreases significantly. However, in order to obtain a high coercive force, preferably B
It is better to have 88 atoms or less, and if it is more than 88 atoms, fine R2FezB
It is difficult to obtain a 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 R2Fe+aB phase is 11nn.
'l' 111 1- -ta L+ @ 铓田 l
-$6 m jE I te l”l Ktt
Temperatures below 71 of +7'-e-A are preferred.

The rationale for the temperature range for slow cooling is that 800°C is best in order to slowly cool from above the melting point of the grain boundary phase, and if slow cooling is stopped before 200°C, the strain caused by the main phase passing through the Curie temperature will increase. Defects such as cracks may occur. Therefore, the range for slow cooling is preferably 800 to 200°C.

As for the cooling rate, if it is faster than 10°C/min, large thermal distortion will occur in the magnet, which will cause defects such as cracks in the magnet. Therefore, in order to prevent cracking, a cooling rate lower than this is desirable.

Next, examples of the present invention will be described.

[Example] [Example 1] Using a rust induction heating furnace in an argon atmosphere, Pry5Tb
+, aFessCO+sBa, eCu+2 alloy (7 Nblan and Pr+ aNd7Fe7s,
5Bscu+ QGas, alloy with composition s (1 6lb and Ce+, 1INdz, 5Dy2Fets
, sBs 3Cu+, i+A1e 7 An alloy (Humple LC) with a composition of
A poem of l-le-surva-,- Ejuzu Scissors 7 Barto As the raw materials for the scissors and gallium, those with a purity of 99.9% were used, and for the boron, ferroboron was used.

These cast ingots were then placed in iron capsules and sealed. This was then hot rolled at 975°C with a working degree of 15% in air four times, and then hot rolled at a working degree of 20% in air three times, until the final working degree was 73%. I made it.

Thereafter, these rolled magnets were subjected to heat treatment under the following conditions.

Condition 1: After heat treatment at 950°C for 4 hours, it was taken out from the heat treatment furnace and cooled in air. The cooling rate at this time was approximately 256 C/min up to 200°C.

Condition 2 After heat treatment at 950°C for 2 hours, controlled cooling so that the temperature decreased linearly to 200°C in 140 minutes (5,
4°C/min) and then removed from the heat treatment furnace and cooled in air.

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

Table 1 From Table 1, it can be seen that after heat treatment, cooling in the range from 800°C to 200°C at a cooling rate of 10°C/min or less is effective in improving the coercive force.

In addition, cracking and chipping during heat treatment of the magnet occurred in sample la under condition 1.
and lb, but not in the condition 2 sample. From this, after heat treatment, from so o'c to 200
It can be seen that cooling at a cooling rate of 10°C/min or less in the range up to 10°C is effective in preventing cracking and chipping.

[Example 2] An alloy having the composition Pr+5Dy2Fe7aBs2Cu+,s 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 then hot rolled at 950°C with a workability of 10% in air four times, then hot rolled at a workability of 15% in air four times, and then hot rolled at a workability of 2°%. The process was carried out twice in air to achieve a final processing degree of 78%.

Then, heat treatment was performed at 950'C for 3 hours, followed by 80'C heat treatment for 3 hours.
After heat treatment at 0°C for 1 hour, controlled cooling was performed under various conditions. Table 2 shows the presence or absence of defects such as cracks and chips in the magnets and the coercive force results when the rolled magnets were cooled after heat treatment under various conditions.

From this table, it can be seen that after heat treatment, cooling in the range from 800°C to 200°C at a cooling rate of 10°C/min or less is effective in preventing cracking and chipping.

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 shows high coercive force by heat treatment at 250-1100'C, and after the heat treatment, it shows a high coercive force from 8QO °C to 20
It is clear that a magnet free from cracks and chips can be obtained by cooling down to 0°C at a cooling rate of 10'C/min or less.

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

(1) The c-axis orientation rate can be increased, and the residual magnetic flux density B
By making the crystal grains finer, the coercive force iHc could be increased, and the maximum energy product (BH) 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 costs can be significantly reduced.

(4”l conventional meltsbinine) fNote L’”10s KuT
Compared to small-scale magnetization methods, 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 Co., Ltd.

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 working at a temperature of 00°C or higher, then 250~1
After heat treatment at a temperature of 100°C, 2
A method for manufacturing a permanent magnet characterized by cooling in the range of 00°C to 800°C at a cooling rate of 10°C/min or less