JPH05315113A - Manufacture of permanent magnet - Google Patents

Abstract

PURPOSE:To mold an R-Fe-B cast and hot-processed magnet by hot bending. CONSTITUTION:This magnet has R (R is at least one kind out of rare earth elements including Y), Fe, and B for its basic ingredients of raw material. In the process of fusing and casting alloy having the said basic ingredients, and next, hot-bending the cast ingot at a temperature of 500 deg.C or more, and next, hot-bending it, it is processed, up to 80% of the maximum flexural distortion epsilonmax. being expressed by epsilonmax.=t/(2r+t) to the radius r of curvature of the inside periphery and the thickness t, at a distortion speed 1 of 5X10<-3>/s or less, and, thereafter, at a distortion speed 2 not more than 1X10<-3>/s and not less than the first distortion speed 1. The occurring of cracking by bending is suppressed, and the time required for bending can be shortened.

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. Many R-Fe-B permanent magnets have been researched and developed as a permanent magnet having an extremely high coercive force and energy product.

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

(1) First, Japanese Patent Laid-Open No. 59-46008 and M. Sagaw
a, S.Fujimura, N.Togawa, H.Yamamoto and Y.Matsu-ura; J.
Appl.Phys.Vol.55 (6), 15 March 1984, p2083, etc., 8 to 30% R (provided that 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 magnetically 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 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 compact is sintered in argon for 1 hour at a temperature around 1100 ° C,
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, see Japanese Patent Laid-Open Nos. 61-217540 and 62-165305.
The effect of multi-step heat treatment is disclosed.

(2) Japanese Patent Laid-Open No. 59-211549 and RWLee; A
Vol. 46 (8), 15 April 1985, p790, ppl. Phys. Lett.
Fe-B magnets are disclosed. This permanent magnet is a quenching ribbon manufacturing device used to manufacture amorphous alloys.
It is manufactured by making a quenched thin piece having a thickness of about 30 μm, kneading the thin piece with a resin, and press-molding.

(3) JP-A-60-100402 and RWLee; A
Vol.46 (8), 15 April1985, p790, ppl.Phys.Lett. Vol. 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 consisting of less than 15 atomic% and the balance of iron and other impurities that are unavoidable in production, the cast ingot is subjected to hot working at a temperature of 500 ° C. or higher to refine the crystal grains and the crystals. Disclosed is a rare earth-iron-based permanent magnet characterized by orienting its axis in a specific direction to magnetically anisotropy the cast alloy.

In addition, this method has a drawback that the degree of freedom in shape is low, but in order to compensate for this, a plate-shaped permanent magnet that is anisotropy by hot working is bent by hot working. A method of molding by carrying out is disclosed in JP-A-2-252222.
It is disclosed in the publication. It is also shown in Japanese Patent Application No. 2-315397. This is because the magnet material is extremely brittle R ₂ F
While utilizing the e ₁₄ B intermetallic compound as a main phase, it has a low melting point grain boundary phase and is in a semi-molten state at a high temperature, so that it is easily plastically deformed. Further, when bending is performed, it is possible to form without causing cracks, with respect to the inner radius of curvature r and the plate thickness t, the maximum bending strain εmax represented by εmax = t / (2r + t) is 0. It is shown in Japanese Patent Application No. 3-095692 that the number is 2 or less.

[0013]

The conventional methods for manufacturing R-Fe-B system 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 has been 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 after press-molding by adding a molding aid is called a green body, 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 the R--Fe--B system sintered magnet, but also the production method thereof has poor production efficiency. Eventually, the manufacturing cost of the magnet increases. Therefore, the advantages of the R-Fe-B based magnet, which has a relatively low raw material cost, cannot be utilized.

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, at 800 ° C. or higher, which causes a coercive force iH.
c becomes extremely low and it does not become 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 working. Therefore, the manufacturing process is most simplified and the mass production cost can be reduced. However, when the magnet has a low degree of freedom in shape and the shape of the magnet is complicated, there is a problem that processing costs such as cutting and grinding become high. Further, the plate magnet can be bent, but the bending depends on the strain rate, the processing temperature, and the plate thickness. Especially when the strain rate exceeds 1 × 10 ⁻³ / s, There was a problem that cracks were likely to occur.

The present invention has the above-mentioned drawbacks of the prior art, particularly (4)
To solve the problem regarding the degree of freedom in shape of the permanent magnet of the present invention, and an object thereof is to provide a high-performance and low-cost manufacturing method of a permanent magnet by preventing the occurrence of cracks during bending. It is in.

[0024]

According to 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 the basic components are used. In the process of melting and casting the alloy, hot working the cast ingot at a temperature of 500 ° C. or higher, and then hot bending, εmax = t for the inner radius of curvature r and the plate thickness t. 5 / maximum bending strain εmax represented by / (2r + t)
In × 10 ^-3 / s less strain rate (strain rate 1), it is in subsequent to 1 × 10 ^-3 / s or less, and strain rate (strain rate is (strain rate 1) ≧ (strain rate 2) It is characterized by being processed in 2).

Further, in order to further increase the coercive force and the performance, it is characterized by performing heat treatment at a temperature of 250 to 1100 ° C. after bending.

As described above, the magnet obtained by subjecting the cast ingot to the hot working has a low degree of freedom in shape, and when the magnet has a complicated shape, the processing cost such as cutting and grinding becomes high. There was a problem. To solve this problem, Japanese Patent Application Laid-Open No. 2-252222 and Japanese Patent Application No. 2-315397 disclose a method of forming a plate-shaped magnet alloy by hot bending. There is a problem that cracks are likely to occur depending on the strain rate, processing temperature and plate thickness. In the present invention, by analyzing the progress of bending,
If the strain rate in processing after the amount of strain due to processing reaches 80% of the maximum bending strain ε max is 1 × 10 ⁻³ / s or less,
It has been found that, when processing up to 80% of the maximum bending strain ε max, the occurrence of cracks due to bending can be suppressed even if processing is performed at a higher strain rate. This method also has the effect of shortening the processing time and improving the productivity.

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

As rare earths, 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 elements, such as Dy and 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 atomic%, the nonmagnetic R-rich phase increases and the magnetic properties remarkably deteriorate. 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 is formed, so that a high coercive force cannot be expected. On the other hand, if it exceeds 28 atomic%, the amount of non-magnetic phase rich in B is increased and the residual magnetic flux density is remarkably 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.

Co is an element effective in increasing the Curie point of the present system magnet, but since it reduces the coercive force, it is 50
Atomic% or less is good.

An element that is present together with an R-rich phase such as Cu, Ag, Au, Pd, and Ga and that lowers the melting point of that phase has the effect of increasing coercive force. However, since these elements are non-magnetic elements, the residual magnetic flux density decreases as the amount of these elements increases, so 6 atomic% or less is preferable.

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.

During bending, the maximum bending strain εmax represented by εmax = t / (2r + t) is 0.2 or less for the inner radius of curvature r and the plate thickness t. It is necessary to bend without cracking.

The temperature in bending is required to be 600 ° C. or higher in order to realize the processing at a processing speed with high productivity without causing cracks during the processing. If the processing temperature exceeds 1050 ° C., the coercive force is likely to decrease due to the coarsening of crystal grains, so a temperature lower than this is desirable.

The heat treatment temperature after bending is preferably 250 ° C. or higher for cleaning the grain boundaries and diffusing primary crystal Fe, and when the R ₂ Fe ₁₄ B phase exceeds 1100 ° C., grain growth rapidly occurs. Since the coercive force is lost, a temperature lower than that is preferable.

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 near the melting point of the R-rich phase at the grain boundary, that is, 750 ° C or less, and 25
If the temperature is 0 ° C. or lower, the effect of the heat treatment takes too long, so the temperature is preferably higher.

Next, examples of the present invention will be described.

[0039]

【Example】

(Example 1) Using an induction heating furnace in an argon atmosphere,
Alloys having the compositions shown in Table 1 were melted and cast. At this time, raw materials of rare earths, iron and copper were used with a purity of 99.9% and ferroboron was used as boron.

The cast ingot thus obtained was placed in an iron capsule, degassed, sealed, and processed at a processing temperature of 950 ° C.
Was hot-rolled. At this time, rolling with a height reduction amount of 30% in one rolling was carried out for 4 passes so that the total working amount became 76%.

During this hot working, the easy axis of magnetization of the crystal was oriented so as to be parallel to the rolling direction of the alloy. From the rolled magnet thus obtained, width 10 mm x length 4
A 0 mm × 4 mm thick sample was cut out. After heating this plate-shaped sample to 1000 ° C. in an inert gas, it was molded into an arc-shaped magnet having an outer diameter of 22 mm and an inner diameter of 18 mm. At this time, for 5 samples per condition, the following 3
Molding was performed under various processing conditions.

A) A bending strain amount of 7% (a strain amount of 70% of the maximum bending strain εmax) is processed at a strain rate of 1.5 × 10 ⁻³ / s, and thereafter, a strain rate of 3.0 ×. Processing at 10 ^-4 / s b) Strain rate of 1.5 × 10 ^-3 from the beginning to the end of bending
/ S c) Strain rate from the beginning to the end of bending 3.0 × 10 ^-4
Processing with / s The results are shown in Table 2. Here, the number of successes is the number of samples that have been subjected to bending without cracking due to the processing, out of the five samples processed under the same conditions.

[0043]

[Table 1]

[0044]

[Table 2]

From these results, it is understood that, in bending, by changing the strain rate in two steps according to the strain amount, the processing time can be shortened without causing cracks due to the processing.

[0046] Similarly to Example 2 Example 1, using an induction heating furnace in an argon atmosphere, Pr _15.5 Fe _{78 .7} B
An alloy having a composition of _5.1 Cu _0.7 was melted and cast. At this time, as the raw materials of the rare earths, iron and copper, those having a purity of 99.9% were used as in Example 1, and ferroboron was used as the boron.

The cast ingot thus obtained was placed in an iron capsule, degassed, sealed, and hot-rolled at a working temperature of 950 ° C. as in Example 1. At this time, rolling with a workability of 30% was performed four times so that the final workability was 76%.

A width of 10 m is obtained from the rolled magnet thus obtained.
m x length 20mm x thickness 2mm, width 10mm x length 40
mm x thickness 4 mm, width 10 mm x length 60 mm x thickness 6
A mm-shaped plate sample was cut out. This plate-shaped sample was heated to 1000 ° C. in an inert gas and then subjected to die bending to form an arc-shaped magnet having a bending strain of 7.5%. At this time, the central angles of the arc-shaped magnets are all 90 °.
In addition, bending was performed on 5 samples per condition, and the following 4 types of steps were taken.

A) The amount of bending strain is 3.9% (maximum bending strain εma
processing at a strain rate of 8.0 × 10 ⁻⁴ / s up to 52% of x),
Subsequent processing at a strain rate of 1.0 × 10 ⁻⁴ / s b) Bending strain amount of 4.8% (64% of maximum bending strain εmax)
Processed at a strain rate of 8.0 × 10 ^-4 / s up to a strain rate of 1.0 × 10 ^-4 / s c) Bending strain amount is 5.7% (76% of maximum bending strain εmax) )
Processed at a strain rate of 8.0 × 10 ^-4 / s, and then processed at a strain rate of 1.0 × 10 ^-4 / s d) Bending strain amount of 6.6% (88% of maximum bending strain εmax) )
Processing up to a strain rate of 8.0 × 10 ⁻⁴ / s, and thereafter processing at a strain rate of 1.0 × 10 ⁻⁴ / s. The results are shown in Table 3. Here, the number of successes is the number of samples which have been bent without cracks among the 5 samples processed under the same conditions.

[0050]

[Table 3]

From the above examples, for the inner radius of curvature r and the plate thickness t, processing up to 80% of the maximum bending strain εmax represented by εmax = t / (2r + t) is performed.
In × 10 ^-3 / s less strain rate (strain rate 1), it is in subsequent to 1 × 10 ^-3 / s or less, and strain rate (strain rate is (strain rate 1) ≧ (strain rate 2) By processing in 2), it is apparent that the time required for bending can be shortened, the productivity can be improved, and the occurrence of cracks during bending can be prevented.

[0052]

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

(1) The manufacturing process is simple and the cost is low.

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

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

(4) A magnet having a shape which is difficult to manufacture by the conventional method of manufacturing a magnet by the hot working method can be manufactured at low cost and with good productivity.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI technical display location // H01F 7/02 B (72) Inventor St. Arai 3-3-5 Yamato, Suwa City, Nagano Prefecture Seiko Epson Corporation (72) Inventor Koji Akioka 3-3-5 Yamato, Suwa City, Nagano Seiko Epson 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, an alloy having the basic components is melted and cast, and then the cast ingot is heated to 500 ° C. or higher. 80% of the maximum bending strain εmax represented by εmax = t / (2r + t) for the inner radius of curvature r and the plate thickness t in the process of hot working at the temperature Up to 5
In × 10 ^-3 / s less strain rate (strain rate 1), it is in subsequent to 1 × 10 ^-3 / s or less, and strain rate (strain rate is (strain rate 1) ≧ (strain rate 2) A method for manufacturing a permanent magnet, characterized by being processed in 2). 2. After the bending process according to claim 1, 250 to 1
A method for manufacturing a permanent magnet, characterized by performing heat treatment at 100 ° C.