JPH04187722A - Production of permanent magnet - Google Patents

Abstract

PURPOSE:To produce a high-efficiency permanent magnet of arbitrary shape with superior productivity by subjecting an ingot of an alloy containing rare earth elements, Fe, and B as essential components to hot working and then to bending under the prescribed conditions. CONSTITUTION:An ingot prepared by melting and casting an alloy containing one or more kinds among rare earth elements such as Pr and Nd, and Fe and B as essential components by proper means is subjected to hot working, such as rolling, at 500-1100 deg.C in the air. Subsequently, a prism-shaped permanent magnet is cut off from the resulting rolled ingot and subjected to bending at 600-1050 deg.C and at <=0.5/s rate of strain. Further it is desirable to perform heat treatment at 250-1100 deg.C after bending.

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.

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

[Prior art] Permanent magnets are one of the important electrical and electronic materials used in a wide range of fields, from various household appliances to peripheral terminal equipment for large computers. With the demand for increased efficiency and increased 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, Japanese Patent Application Laid-open No. 59-46008 and 9. S
Agawa.

S, Fujimura, N, Togawa, H, Yam.
amot, o 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 (wherein R is at least one rare earth element including Y), 2~28% B, and the balance Fe is a powder metallurgy-based 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
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 Ap
ril 1985. P790 discloses an R-Fe-BM stone in which fine pieces of melt-spun alloy ribbons with a very fine crystalline magnetic phase are bonded by 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 rapidly cooled flakes used in the method (2) above are obtained by a method called a two-step hot pressing method in a vacuum or an inert atmosphere to obtain a dense and anisotropic R-Fe-BE stone. 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
30 atom%, B2 to 28w%, Co50 atom% 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 magnetically anisotropic by orienting its axis in a specific direction. Further, it is disclosed in Japanese Patent Application No. 1-72733 that this magnet can be bent to have a free shape.

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

The manufacturing method for permanent magnets in (1) requires that the alloy be made into powder, but R-Fe-B alloys are highly active towards oxygen, so if they are made into powder, they will oxidize even more violently. Therefore, the degree of oxygen immersion 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, -R-Fe-B in terms of boat fishing.
Not only does the production of sintered magnets of this type require expensive equipment, but the production method has poor production efficiency, resulting in an increase in the production cost of the magnets. 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 method for manufacturing permanent magnets in (2) and (3) is as follows:
A vacuum melt spinning device is used, which
Currently, it is very inefficient and 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.

Method (4) for manufacturing permanent magnets does not involve a powder process and only requires one step of hot pressing, which simplifies the manufacturing process the most. The problem was that it was difficult to obtain. This problem was solved by the manufacturing method disclosed in Japanese Patent Application No. 1-72733, but this method had the disadvantage that the processing took a long time and the productivity was poor.

The present invention is intended to solve the above-mentioned drawbacks of the prior art, particularly the drawback (4) regarding the degree of freedom in the shape of permanent magnets, and its purpose is to create high-performance, low-cost permanent magnets of any shape. The object of the present invention is to provide a manufacturing method that can be obtained with high productivity.

[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 working at a temperature of 0℃ and then 600~1050℃
It is characterized by bending at a strain rate of 0.5/s or less at a temperature of It is characterized by

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. A small number of heavy rare earth elements, such as Dy
, '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 R8 to 25 at % is suitable.

B is an essential element for forming the R2Fe+4B 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 R2Fe+a
It is difficult to obtain phase B, and the coercive force is small.

Co is an effective element for increasing the Curie point of the present magnet, but since it reduces the coercive force, it is preferably 50 atomic % or less.

Elements such as Cu, Ag, Au, Pd, and Ga that exist together with the R-rich phase and lower the melting point of the phase have the effect of increasing coercive force. However, since these elements are non-magnetic elements, increasing the amount will reduce the residual magnetic flux density, so it is preferably 6 at % or less.

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 temperature during the bending process is required to be 600° C. or higher in order to achieve high productivity and cutting speed. This is because if processing is performed at a high processing speed (high strain rate) at a temperature lower than this, cracks will occur during processing. If the processing temperature exceeds 1050° C., there is a high possibility that the coercive force will decrease due to the increase in the size of crystal grains, so it is preferable that the processing temperature is lower than this temperature.

In addition, when the strain rate is 0.5/s or more, 600 to 105
Since cracks begin to occur even in a temperature range of 0°C, it is preferable that the speed is below this temperature range.

The heat treatment temperature was set at 25°C to diffuse the Fe in the initial product.
The temperature is preferably 0°C or higher, and the R2Fe14B phase is 1100°C.
If the temperature is higher than 0.degree. C., grains will grow rapidly and the coercive force will be lost, so a temperature lower than that is preferable.

Next, examples of the present invention will be described.

[Example 1] First, using an induction heating furnace in an argon atmosphere, P r
An alloy having a composition of 17F e 7a, sB sCu 15 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, this cast ingot is placed in an iron capsule,
Degassed and sealed. This was hot-rolled in air at 950° C. and a working degree of 30% four times to give a final working degree of 76%.

From the rolled ingot thus obtained: 3X 3X 2
Cut out a 5 mm prismatic magnet and set the crosshead speed to 8.3 x 10-' mm/s to 8.0 mm at 800°C.
A three-point bending test was conducted in an Ar atmosphere at a speed varying up to 3 mm/s.

The distance between the supports in the bending test used here was 16 mm, and the maximum deflection was 4 mm.

Table 1 shows the success or failure of processing, 950℃×4 hours and 500℃×
The magnetic properties after heat treatment for 1 hour are shown. At this time, the crosshead speed is converted from the curvature of the sample surface to the tensile strain rate on that surface.

Table 2 also shows samples of the same shape at 500 to 1100℃.
crosshead speed at 8.3x 10-'m
m/S, that is, the strain rate was set to 4X 10-2/S, and the success or failure of processing when a three-point bending test was conducted in an Ar atmosphere, and the magnetic properties after heat treatment at 1000°C x 3 hours and 500°C x 1 hour. shows.

Table 1 ○: Good machining ×: Destruction Table 2 O: Good machining ×: Destruction From these results, the magnetic properties are not impaired in the temperature range of 800 to 1050°C, and the productivity is high at 4X 10-1/S. It is clear that bending can be performed at high processing speeds.

[Example 2] An alloy having the composition shown in Table 3 was melted and cast in the same manner as in Example 1. The raw materials used were also of similar purity.

Next, these cast ingots were heated in an argon atmosphere for 9
Pot pressing was performed at 50° C. to a working degree of 75%.

Then, bending was performed at T2 shown in Table 3 at a strain rate of 8X 10-'/s.
A straw magnet with R=40 mm was used.

The straw magnets of each alloy composition shown in Table 3 were subjected to heat treatment (1000'Cx 2 hours and 600'Cx
The magnetic properties after 1 hour) are shown in Table 4.

From the examples above in Table 3 and Table 4, it is clear that permanent magnets whose basic raw materials are R (where R is at least one rare earth element including Y) + Fe and B are hot-processed at 500 to 1100°C. It is made anisotropic by bending at a strain rate of 0.5/s or less at 600 to 1050 °C, and exhibits high coercive force by heat treatment at 250 to 1100 °C.
It is clear that the highest (B[()max) exceeds 30 MGOe.

[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 (Bt()max) could be significantly improved.

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

(3) 02 drift in the magnet is low.

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

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

(6) Magnets with shapes that are difficult to manufacture with conventional hot-processed magnets can be manufactured with high productivity.

that's all Applicant: Seiko Epson Corporation Agent: Patent attorney Kizobe Suzuki and 1 other university; dog

Claims (2)

[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 to 1100℃ and then 600℃
A method for manufacturing a permanent magnet, which comprises bending at a strain rate of 0.5/s or less at a temperature of ~1050°C. (2) The method for manufacturing a permanent magnet according to claim 1, characterized in that the bending process is followed by heat treatment at 250 to 1100°C.