JPH0821497B2 - Anisotropic magnet and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to an R—Fe—B type anisotropic magnet and a method for producing the same, and more specifically, it is obtained by quenching an R—Fe—B type alloy. The present invention relates to an anisotropic magnet whose performance is improved by subjecting the solidified powder to be subjected to specific hot forming and specific hot working, and a method for producing the anisotropic magnet.

<< Prior Art >> As an R-Fe-B type anisotropic magnet, alloy melting → quenching → crushing (particle size adjustment) → hot forming because of the fact that the process is recently simple and the manufacturing cost is low. → The so-called rapid cooling type manufactured by hot working is attracting attention.

By the way, in the manufacturing process of the above-mentioned rapid cooling type R—Fe—B anisotropic magnet, hot forming may be performed into a cylindrical shape, and hot working may be performed into a disk shape. It is generally done.

That is, as shown in FIG. 7, the columnar product 1 obtained in the hot forming step is pressed from above to produce a disc-shaped product 1 '.
To get.

The reason for this is that if it is disc-shaped, plastic flow tends to be uniform in the plane as it is plastically deformed due to its symmetry, and as a result, uniform magnet characteristics can be obtained. This is because a cylindrical shape is preferable as the original shape for obtaining the product.

<< Problems to be Solved by the Invention >> By the way, the hot working described above, whether performed by upsetting or rolling, in any case, the mechanism of the crystal orientation accompanying the plastic deformation is still, The reality is that we do not understand it well.

However, the fact that the C-axis direction is oriented in the stress direction with machining has been confirmed, and it is understood that the problem lies in the degree of orientation of the C-axis. Conventionally, the degree of orientation of the C-axis has been mainly considered only by the strength of the applied stress.

That is, in the conventional processing methods such as upsetting and rolling, the uniaxial (or one surface) is always the free direction (or free surface) with respect to the applied stress, so that direction (or surface)
Is in the direction of stress relief (escape).

Therefore, no matter how much stress is applied, the pressure becomes substantially weak in the direction of the escape, and the orientation becomes insufficient.

FIG. 8 is a diagram for explaining this state. FIG. 8A shows the case of upsetting and FIG. 8B shows the case of rolling.

In the case of swaging, the side view (A-
1) and the same figure (A-1) AA line sectional arrow line view (A-2)
As shown in, when stress is applied to the hot-molded body 1 sandwiched between the upper and lower punches 2, 2 ′ and the uss 3 from the direction of the arrow α,
This stress escapes in the direction of arrow β due to the plastic deformation of the molded body 1.

In the case of rolling, as shown in the side view (B-1) of the same figure (B) and the sectional view (B-2) taken along the line AA of the same figure (B-1), in the direction of the arrow α. When stress is applied to the hot compact 1 sandwiched between the pair of rotating rollers 4 and 4'from the direction of the arrow α by the rotation of the rollers 4 and 4 ', this stress causes plastic deformation of the compact 1. It escapes in the direction of arrow β.

Thus, in both upsetting and rolling, in order to process the hot-molded body, the stress applied to this hot-molded body is not all spent on the processing of the hot-molded body, Not only will energy be lost, but the hot-molded body will be processed by insufficient force, making the hot-processing itself insufficient.

The present invention has been made in view of the above points, and its purpose is to reduce the escape of the above stress,
An R-Fe-B based anisotropic magnet having an improved degree of C-axis orientation and a method for producing the same.

<< Means for Solving the Problem >> In order to achieve the above object, the anisotropic magnet according to the present invention is obtained by rapidly cooling to an amorphous state, then hot forming and then hot working. An —Fe—B anisotropic magnet (one or more elements of rare earth elements including R: Y), characterized in that the magnetic orientation direction is substantially uniform.

Further, in the method for producing an anisotropic magnet according to the present invention, after being rapidly cooled to an amorphous state, it is hot molded into a rectangular parallelepiped having a width a, a length b, and a height c, and A working die including a rectangular portion having an inner dimension of approximately a × b and a trapezoidal portion having an angle θ of 45 ° to 85 ° following the rectangular portion, or (2) the die and the trapezoidal portion side of the die. The upper and lower punches are tapered to have a taper angle θ2 of 45 ° to 85 °.

In this case, the processing speed of upsetting hot working is 1
It is also characterized in that it is set to ~ 30 mm / sec.

Further, in the method for producing an anisotropic magnet according to the present invention, the above rectangular parallelepiped is rolled into a pair of rolling parts consisting of a straight part having a length b and a taper part having an angle θ of 45 ° to 85 ° following the straight part. It is also characterized by hot rolling between the rolls.

<< Operation >> In the anisotropic magnet according to the present invention, the magnetic orientation direction is substantially uniform, and this uniform magnetic orientation direction is R-Fe-B.
This serves to improve the magnet characteristics of the anisotropic magnet.

Further, in the method for producing the anisotropic magnet according to the present invention,
The R-Fe-B system molten alloy is rapidly cooled to an amorphous state.

The powder obtained by this quenching is first of all width a, length b, height c
Hot forming into a rectangular parallelepiped.

Next, the above rectangular parallelepiped is swaged and hot worked using a working die including a rectangular portion having an inner dimension of approximately a × b and a trapezoidal portion having an angle θ of 45 ° to 85 ° following the rectangular portion.

In this way, since the processing die having the rectangular portion having the same size and shape as the processing rectangular parallelepiped is used, the processing rectangular parallelepiped is a portion that comes in contact with the upper and lower punches that are vertically movable in the processing die. Of these, the portion of the working die located in the rectangular portion is shared before and after the upsetting hot working.

Therefore, the escape of the stress applied to the rectangular parallelepiped to be processed during the upsetting hot working occurs in a portion other than this shared portion, and the stress is used for the hot working of the rectangular parallelepiped to be processed with a small loss.

Furthermore, in the method for producing the anisotropic magnet according to the present invention,
Using a processing die of the above size and shape and an upper and lower punch with a taper angle θ2 of 45 ° to 85 ° processed on the trapezoidal portion side of the die, heat up the rectangular parallelepiped. Process between.

In this case, the rectangular parallelepiped to be processed is similar to the above case,
In addition to the fact that the portion of the machining die that is located in the rectangular portion of the upper and lower punches is shared before and after the upsetting hot working, the taper of the vertical angle θ2 that is processed by the upper and lower punches is used. The sandwiching action due to is synergistic.

As a result, the relief of the stress applied to the rectangular parallelepiped during upsetting hot working occurs in a much smaller range than in the above case, and the stress is extremely small loss and is used for hot working of the rectangular parallelepiped to be processed. Will be done.

Further, in the method for producing the anisotropic magnet according to the present invention,
The above rectangular parallelepiped is hot-worked by rolling using a pair of rolling rolls each having a straight part having a length b and a taper part having an angle θ of 45 ° to 85 ° following the straight part.

In this case, due to the sandwiching action of the taper of the rolling roll at the angle θ, the relief of the stress applied to the rectangular parallelepiped during the rolling process occurs in the direction in which the taper contracts, and the loss of stress is caused by the above-mentioned upsetting heat. Less, but less than hot working.

<< Example >> Example 1 A master alloy was arc-melted so that the composition was Nd ₁₅ Fe ₇₉ B ₆ . Using a single-roll method, apply Cu from a quartz tube with a small hole with a diameter of 0.3φ at a peripheral speed of 25 m / sec, a jet pressure of 1.2 kg / cm ^2.
It was jetted onto the roll surface and quenched. The flaky powder obtained is ground in an inert gas atmosphere to give a particle size of 40
It was set to 0 μm or less.

 This powder had a coercive force iHc = 16.7 kOe.

The powder, in a vacuum, and hot pressing (hot working) at a pressure of 0.9 t / cm ² at 700 ° C., a = 15 mm (width), b = 15
A rectangular parallelepiped sample of mm (length) and c = 30 mm (height) was obtained.

For comparison, a columnar test of 16.9 φmm × 30 mm was prepared under the same conditions.

Next, these samples were subjected to hot working under the following conditions.

Hot working condition: Temperature 730 ℃ Pressure 0.9 ton / cm ² Machining rate 50% constant ¹⁾ Machining speed 5mm / sec 1) Machining rate = (Height before machining H ₀ −Height after machining H) / H ₀ × 100 (%) Molds and punches used: For rectangular parallelepiped samples (examples of the present invention); those showing the plan view of FIG. 1 (a) and the sectional view of FIG. 1 (b) (a = b = 15 mm, θ = 80 °) ).

What is shown in the plan view of FIG. 2 (a) and the sectional view of FIG. 2 (b) (a = b = 15 mm, c = 30 mm, θ ₁ = 80 °, θ ₂ = 80)
゜).

Regarding the cylindrical sample (comparative example); those shown in the sectional view of FIG. 7 (a) and the plan view of FIG. 7 (b) (d ₁ = 16.9 mmφ, d ₂ = 30 mmφ, θ ₃ = 90 °).

What is shown in the sectional view of FIG. 7 (a) and the plan view of FIG. 7 (b) (d ₁ = 16.9 mmφ, d ₂ = 50 mmφ, θ ₃ = 80 °).

In addition, FIG. 1 (a), (b), FIG. 2 (a),
(B), FIGS. 7 (a), (b), and FIG. 9 (A-1,2), the same reference numerals indicate the same parts as in FIG. 9 (A-1,2), and 10 indicates the present invention. The working dies in the manufacturing method according to the present invention and the reference numerals 12 and 12 'are the upper and lower punches in the manufacturing method according to the present invention.

The processing die 10 and punches 2, 2'of FIGS. 1 (a) and (b),
When the rectangular parallelepiped sample 1 is swaged and hot-worked by using the processing die 10 and the punches 12 and 12 'of FIGS. 2 (a) and (b), the stress applied to the rectangular parallelepiped sample 1 by this processing is In the plan view of FIGS. 3A and 3A, the cross-sectional view of FIG. 3B, and the plan views of FIGS. 3B and 3A and the cross-sectional view of FIG.

That is, in the case of FIGS. 1 (a) and 1 (b), as shown in FIGS. 3 (A-1 and 2), the height of the sample is increased in the direction of contraction in the plane direction and in the cross-sectional direction. In the direction perpendicular to the vertical direction, in the case of Fig. 2 (a) and (b), as shown in Fig. 3 (B-1, 2), contraction occurs in both the plane direction and the cross-sectional direction to the trapezoidal upper surface side. Run in the direction you want to.

On the other hand, the die 01 and punch shown in FIGS. 7 (a) and 7 (b) are used.
When the columnar sample 1 is swaged and hot-worked using 2,2 ′, the stress applied to the columnar sample 1 by this process is as shown by the arrow β in FIG. Run in the direction.

As described above, in the method according to the present invention using the die and punch shown in FIGS. 1 and 2, the stress escapes much more than the comparative method shown in FIG. 7 using the die and punch. Less.

From the sample obtained as above, 10mmφ × 10mmH
When the BH loop was measured by cutting out the measurement sample of, the results shown in Table 1 were obtained.

Example 2 In the same manner as in Example 1, a = 15 mm, b = 15 mm, c = 30 mm
A (height) rectangular parallelepiped sample was obtained.

This was sandwiched between a pair of rolling rolls 14 and 14 'shown in FIG. 4, and hot working was performed by rolling.

The dimensions and shape of the rolling rolls 14 and 14 'and rolling conditions were as follows.

θ = 80 ° b = 15mm Temperature 730 ° C Atmosphere in argon gas Working rate 50% constant ²⁾ 2) One working rate (rolling rate) is about 10% and reciprocating between rolling rolls 14 and 14 'multiple times. To 50%.

In this case, the stress applied to the rectangular parallelepiped sample 1 by rolling is in the direction of arrow β in FIG. 4, that is, the rolling rolls 14 and 14 ′.
Since the tape escapes in the taper shrinking direction, there is little stress escape.

A 10 mmφ × 10 mmH measuring sample was cut out from the sample obtained as described above, the BH loop was measured, and the results are shown in Table 2.

In addition, for comparison, the measurement results of the case where a normal roll of θ = 90 ° was processed under the same conditions as above except for Table 2
It was shown to.

Example 3 FIG. 5 (a) of sample No. 2 obtained in Example 1
5 m from the schematic position shown in the plan view and the cross-sectional view of FIG.
A measurement sample of mφ × 6 mmH was cut out and each BH loop was measured.

 The obtained results are shown in Table 3.

As is clear from Table 3, there is almost no variation in the magnet characteristics depending on the position of the sample, and high characteristics are exhibited. Therefore, it can be seen that the present invention is extremely advantageous as a method for making a magnet anisotropic by hot plastic working.

Example 4 Sample Nos. 1 to 4 obtained in Example 1 were crushed by using a jaw crusher in an inert atmosphere to prepare particles having a particle size of 400 μm or less and 200 μm or more.

This was kneaded with 3 wt% of an epoxy resin, molded at a pressure of 4 ton / cm ² in a magnetic field of 15 kOe, and then cured at 120 ° C. for 1 hour. Obtained sample (10mm × 10mm
The BH loop of (× 20 mm) was measured, and the results are shown in Table 4.

Example 5 The particles used in Example 4 were further crushed in the same manner to obtain a particle size of 200.
It was set to not more than μm.

This was kneaded with a 10 wt% nylon resin (nylon 66) and injection molded in a magnetic field of 10 kOe. Obtained sample (10m
A BH loop of m × 10 mm × 20 mm) was measured, and the results are shown in Table 5.

Example 6 A die and punch (however, a as shown in FIGS. 2A and 2B)
= B = 15 mm, θ ₁ = θ ₂ = 80 °), a rectangular parallelepiped sample of a = 15 mm, b = 15 mm, c = 30 mm obtained by the same process as in Example 1 is referred to as Example 1. Plastic working was performed at various working speeds.

 The processing temperature was 730 ° C and the processing rate was constant at 50%.

A 10 mmφ × 10 mmH sample was cut out from the obtained sample, and the BH loop was measured. The result is shown in FIG. 6 in comparison with the processing speed.

As is clear from Fig. 6, the slower the machining speed,
Although it will be plastically deformed slowly and the degree of orientation will be good, the coercive force will be long because it will be exposed to high temperature for a long time.
On the contrary, iHc decreases and moves away from the practical value.

Also, if the processing speed is fast, the time to be exposed to high temperature is short, so iHc is large, but since plastic deformation is rapid,
The degree of orientation disappears.

From the above, it can be seen that the value of (BH) _max shows the highest value under these intermediate conditions.

<< Effects of the Invention >> As described in detail above, in the method for manufacturing an anisotropic magnet according to the present invention, by reducing the degree of freedom of stress relief applied during plastic deformation by hot working, 4πIm and
It is possible to improve Br and also Br / 4πIm.

Further, a so-called compression-bonded or injection-molded anisotropic bonded magnet produced by crushing the magnet block obtained by the manufacturing method according to the present invention and kneading it with a resin also exhibits good squareness.

This means that at the stage of the magnet block, the degree of orientation in the vertical pressing direction (that is, the degree of C-axis orientation) is improved. That is, it means that it is closer to uniaxial anisotropy, and as a result, it can be understood that the properties as a bonded magnet, particularly the squareness (Br / 4πIm), are improved.

As described above, according to the manufacturing method of the present invention, the degree of freedom of plastic deformation in a working die having a specific shape is limited, and the escape is reduced, thereby improving the degree of C-axis orientation of crystals, Characteristics, especially squareness can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a working die used in upsetting hot working of a method for manufacturing an anisotropic magnet according to the present invention.
FIG. 2A is a plan view, FIG. 2B is a cross-sectional view, and FIG. 2 is a processing die and upper and lower punches used in upsetting hot working in the method for manufacturing an anisotropic magnet according to the present invention. FIG. 1A is a plan view, FIG. 1B is a cross-sectional view, and FIG. 3 is a swaging heat using a die and a punch shown in FIGS. FIG. 4 is a view for explaining a stress relief condition during hot working, FIG. 4 is a view showing an embodiment of a rolling roll used in hot rolling for rolling of an anisotropic magnet manufacturing method according to the present invention, FIG. The figure shows the positions cut out from the sample in order to measure the magnet characteristics at each position of the sample obtained by using the processing die shown in FIG. 1, and FIG. (B) is a cross-sectional view, and Fig. 6 is the processing speed of the sample obtained by swaging hot working using the working die and punch of Fig. 2 at various processing speeds. Fig. 7 is a graph showing the measurement results of magnet characteristics according to Fig. 7, Fig. 7 is a diagram showing the dimensions and shapes of the working die and punch used in the comparative example, the shape of the sample, and the relief direction of the stress applied during hot working, Fig. 8 Is a diagram showing the shape of a conventional hot-molded body and the shape of a sample obtained by hot working the molded body, and FIG. 9 is a view for explaining the defects in the conventional hot-molded body and the hot working method. In the figure, the figure (A-1, 2) is the same as the figure (B-1,
FIG. 2) is a diagram for explaining the case of rolling hot working of a cylindrical hot compact. 1 ... Hot compact 10 ... Processing die 12,12 '... Upper and lower punch 14,14' ... Rolling roll

Claims (5)

[Claims] 1. An R—Fe—B type anisotropic magnet (one or more of rare earth elements including R: Y) obtained by being rapidly cooled to an amorphous state, followed by hot forming and then hot working. Element),
An anisotropic magnet characterized in that the magnetic orientation direction is substantially uniform. 2. After being rapidly cooled to an amorphous state, it is hot-molded into a rectangular parallelepiped having a width a, a length b and a height c, and the rectangular parallelepiped has an inner dimension of approximately a.
A method for producing an anisotropic magnet, comprising hot working up by a working die comprising a rectangular portion of × b and a trapezoidal portion having an angle θ of 45 ° to 85 ° following the rectangular portion. 3. After being rapidly cooled to an amorphous state, it is hot-molded into a rectangular parallelepiped having a width a, a length b and a height c, and the rectangular parallelepiped has an inner dimension of approximately a.
Machining die consisting of a rectangular portion of × b and a trapezoidal portion with an angle θ1 of 45 ° to 85 ° following the rectangular portion, and a top and bottom with a taper having a taper angle θ2 of 45 ° to 85 ° on the trapezoidal portion side. A method for producing an anisotropic magnet, comprising hot working by swaging with a punch. 4. The processing speed of upsetting hot working is from 1 to 30.
4. The method for producing an anisotropic magnet according to claim 2, wherein mm / sec is set. 5. After being rapidly cooled to an amorphous state, it is hot-molded into a rectangular parallelepiped having a width a, a length b, and a height c, and the rectangular parallelepiped is provided with a straight portion having a length b and an angle θ that follows the straight portion. A method for producing an anisotropic magnet, characterized in that hot rolling is performed between a pair of rolling rolls each having a taper portion of 45 ° to 85 °.