JP2001006911A - Manufacture of rare earth permanent magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a rare earth permanent magnet which can obtain a rare earth permanent magnet having excellent magnetic characteristic by improving the conventional two alloy method. SOLUTION: In this manufacturing method, powder of A alloy (alloy composed of mainly R2TM14B phase where R is at least one kind of rare earth element which is mainly Nd or Pr or Dy or Tb, and TM is a transition metal element which is mainly Fe or Co) and B alloy (alloy containing R and TM where the amount of R is at least 20 atm.%) are mixed by the ratio wherein B alloy powder of 1-30 wt.% is mixed to A alloy powder of 70-99 wt.%. The obtained mixed powder is molded by applying pressure in a magnetic field, and a molded member is formed. After that, the molded member is sintered in a vacuum or inert gas atmosphere and subjected to aging process at a temperature lower than or equal to a sintering temperature. In this case, the amount of R in the A alloy is 12.4-14.0 atm.%, and the above mixed powder is molded by applying pressure in an intensive magnetic field whose magnetic field intensity is at least 1.6 T.

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 rare earth permanent magnet having excellent magnetic properties, particularly an R-TM-B permanent magnet.

[0002]

2. Description of the Related Art Rare earth permanent magnets are used in a wide range of fields, from general household products to peripheral terminals of large computers and medical equipment, and are one of the extremely important electric and electronic materials that hold the key to advanced technology. is there. Further, in recent years, computers and communication devices have been required to have higher performance in terms of reduction in size and weight, higher efficiency, and environmental protection and energy saving. Among rare earth permanent magnets, Nd-
Fe-B-based magnets are rich in Nd as a main component in terms of resources, are inexpensive, and have excellent magnetic properties.
Its use is spreading more and more. In addition, research and development for improving magnetic properties are also being made energetically, and many inventions and ideas have been proposed. Numerous inventions and inventions have been proposed for a method of producing a high performance rare earth magnet by mixing and sintering two kinds of alloy powders having different compositions (A alloy powder and B alloy powder) (hereinafter referred to as a two alloy method). (JP-A-63-9384, JP-A-63-115)
No. 307).

In the conventional two-alloy method, an R-rich amorphous alloy or microcrystalline alloy is used as the B alloy powder. However, since these have no crystalline magnetic anisotropy, they are insufficient for improving the characteristics in a magnetic field. No proper orientation was obtained. Therefore, in order to overcome such a drawback, Co is added to the B alloy powder, and in addition to the RFe ₁₄ B phase and the Nd-rich phase, RTM ₄
B phase, RTM ₃ phase, RTM ₂ phase, R ₂ TM ₇ phase, RTM
₅ phases appeared, mixed with A alloy powder, high performance Nd
A method of manufacturing a system magnet has been proposed (Japanese Patent Laid-Open No. 5-2 / 1993).
1218, JP-A-5-21219, etc.). RTM ₄ B phase, RTM ₃ phase, RTM ₂ phase, R ₂ T
Since the M ₇ phase and the RTM ₅ phase have crystal magnetic anisotropy,
The appearance of these phases causes the B alloy to be oriented at the time of orientation.

[0004]

SUMMARY OF THE INVENTION The magnetism of rare earth permanent magnets
The demands on the properties are very high,
In recent years, larger orientation magnetic fields have been used for characterization
There is a tendency. Apply magnetic field to magnet powder composed of ferromagnetic particles
When added, each magnetic particle connects to a bead,
Form a chain of particles. Especially Nd_Two Fe₁₄B phase
Such magnetic particles having a large magnetic anisotropy have magnetic poles of each particle,
That is, the north pole and the south pole are joined to each other to form
Form a child chain. In this case, the magnetic field orientation
The particles rotate in the direction of the alignment magnetic field to form the chain.
However, the magnetic particles are completely
The N and S poles cannot be joined, resulting in poor orientation.
Therefore, in order to obtain rotational force that overcomes friction,
It is necessary to orient with a larger magnetic field. Used in two alloy method
Of the magnet powders used, A alloy powder is mainly R_Two TM₁₄B
It consists of a ferromagnetic material with a very strong phase, and the B alloy powder
Amorphous, microcrystalline, Nd-rich, RTM_Four 
B phase, RTM_Three Phase, RTM_Two Phase, R_Two TM₇ Phase, RTM
_Five Phase, R_Three It is made of a magnetic or non-magnetic material having a weak TM phase.
By the way, the Nd-based magnet is_Two Fe₁₄When sintering with phase B
R-rich amorphous or microcrystalline phase forming liquid phase, N
d-rich phase, RTM_Four B phase, RTM_Three Phase, RTM_Two phase,
R_Two TM₇ Phase, RTM_Five Phase, R_Three TM phase (hereinafter referred to as liquid phase
Phase) is uniformly dispersed, and Nd_Two Fe₁₄B compound
A uniform liquid phase is formed around the object. And Nd-based magnetism
To improve the stone's holding power, use Nd_Two Fe₁₄B compound
Nuclei such as lattice defects and oxide phases existing at grain boundaries
And remove grain boundaries and clean grain boundaries. I
However, in the conventional two-alloy method, high orientation in a strong magnetic field
To apply a strong magnetic field to the magnet powder used to obtain
And only A-alloy powder, which is a very strong ferromagnet, has priority
A chain of magnetic particles is formed,
As a result, the separation of A alloy and B alloy occurs,
There is a problem that coercive force is reduced. Therefore, the present invention
Has improved conventional two-alloy method and has excellent magnetic properties
Manufacture of rare earth permanent magnets that can obtain rare earth permanent magnets
The purpose is to provide a fabrication method.

[0005]

The present invention SUMMARY OF] is made A alloy (mainly R ₂ TM ₁₄ B phase, R represents Nd, Pr, Dy,
At least one or more rare earth elements mainly composed of Tb;
M is a transition metal element mainly composed of Fe and Co) and a B alloy (an alloy containing R and TM and having an R content of 20 atomic% or more)
Are mixed with 70 to 99% by weight of the A alloy powder and 1 to 30% by weight of the B alloy powder, and the resulting mixed powder is pressed and molded in a magnetic field to form a compact. Sintering in a vacuum or an inert gas atmosphere and aging at a low temperature equal to or lower than the sintering temperature, wherein the amount of R in the A alloy is 12.4 to 14.0 atomic%. ,
A method for producing a rare earth permanent magnet, wherein the mixed powder is subjected to pressure molding in a strong magnetic field having a magnetic field strength of 1.6 T or more.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION According to the method for producing a rare earth permanent magnet of the present invention, as described above, in the conventional two-alloy method, the amount of R in the A alloy is 12.4 to 14.0 at%, The mixed powder is subjected to pressure molding in a strong magnetic field having a magnetic field strength of 1.6 T or more. And, due to this feature, the A alloy gives a liquid phase during sintering,
Even under a strong magnetic field of 1.6 T or more, separation of the Nd ₂ Fe ₁₄ B phase and the liquid phase is prevented, and a rare earth permanent magnet with high orientation, high residual magnetic flux density and high coercive force can be manufactured.

The reason why the R content in the A alloy is set to 12.4 to 14.0 atomic% is that when the R amount is less than 12.4 atomic%, a sufficient liquid phase is not formed in the A alloy and the coercive force is reduced. This is because if it exceeds 14.0 atomic%, it is close to one alloy and the excellent distribution height obtained by the two alloy method is hindered. The reason for setting the magnetic field strength to 1.6 T or more is to obtain a rare earth permanent magnet having a high residual magnetic flux density and a high coercive force by performing high orientation in a strong magnetic field. This is because the A alloy powder and the B alloy powder do not separate and the magnetic properties cannot be improved.

The A alloy powder is preferably produced by a strip casting method. The strip casting method is a method of manufacturing a thin alloy body by continuously supplying a melt of a magnet alloy to a single-roll or twin-roll quenching roll. At this time, in the Nd ₂ Fe ₁₄ B phase of the A alloy, the a-axis, which is the axis of difficulty in magnetization, grows from the roll surface to form columnar crystals. Since the liquefied phase exists between these columnar crystals, when the alloy thin body is pulverized, the liquefied phase does not exist in the a-axis direction but exists only in the c-axis direction. And A
When the alloy powder and the B alloy powder are mixed and then oriented under a strong magnetic field, the liquid phase in the A alloy powder preferentially becomes Nd ₂
Supposed to exist between the chain of the magnetic particles of Fe ₁₄ B phase, since Nd ₂ Fe ₁₄ B phase and liquidus phase is uniformly distributed, the coercive force is not reduced.

A alloy powder or a mixture of A alloy powder and B alloy powder
When the mixed powder is subjected to hydrogenation and dehydrogenation, the A alloy powder becomes
Cracks are formed along the liquid phase and are crushed. Plus Nd
_Two Fe₁₄Pulverization with B phase and liquid phase attached
In the case of orientation under a strong magnetic field, Nd_Two Fe₁₄
The phase B and the liquid phase are not separated, and Nd_Two Fe ₁₄
The B phase and the liquid crystal phase are uniformly distributed, and the coercive force is increased.
Do not lower.

When a strong magnetic field is generated, the use of a pulsed magnetic field makes it easy to obtain a strong magnetic field and easily obtain a high orientation. However, a strong magnetic field due to a pulsed magnetic field has a steep rise of the magnetic field and has a high energy for rotating the magnetic particles when a magnetic field is applied, but the Nd ₂ Fe ₁₄ B phase and the liquid phase are easily separated.

[0011]

EXAMPLES Examples of the present invention will be specifically described below, but the present invention is not limited to these examples. (Example 1, Comparative Example 1) Nd, F having a purity of 99.9% by weight
Compositional formula 12.5Nd using e-metal and ferroboron
After casting an alloy ingot of -81.5Fe-6B (atomic%) in an Ar atmosphere of a high-frequency melting furnace, the alloy ingot was heated at 1070 ° C. in an Ar atmosphere.
This was solution-treated for a time, and this was used as an A alloy. Next, using Nd, Dy, Fe, Co metal and ferroboron having the same purity of 99.9% by weight, the composition formula is 20Nd-10Dy-20F.
An alloy ingot of e-44Co-6B was melt-cast in an Ar atmosphere of a high-frequency melting furnace to obtain a B alloy. The A-alloy ingot and the B-alloy ingot are each separately coarsely pulverized in a nitrogen atmosphere to 30 mesh or less, and then the A-alloy coarse powder is weighed to 90% by weight, and the B-alloy coarse powder is weighed to 10% by weight. In a V blender for 30 minutes.
This mixed coarse powder was finely pulverized with a jet mill using high-pressure nitrogen gas to an average particle size of about 5 μm. While orienting the obtained mixed fine powder in a static magnetic field of 17 kOe, about 1 tonf
/ Cm ² to obtain a molded body. Next, this molded body was sintered at 1070 ° C. for 1 hour in a sintering furnace in an Ar atmosphere, further subjected to aging treatment at 530 ° C. for 1 hour, and rapidly cooled to produce a magnet alloy C of Example 1. The composition of this magnet is 13.1Nd-0.8Dy-76.6Fe-3.5.
Co-6.0B. For comparison, an alloy ingot having a composition formula of 12.0Nd-82Fe-6B was used as the A alloy, and a composition formula of 27Nd-11Dy-8Fe- was used as the B alloy.
Example 1 was prepared using an alloy ingot of 48Co-6B.
It was produced in the same manner as described above. Next, using A and B, a magnet alloy C of Comparative Example 1 was produced in the same manner as in Example 1 below. Table 1 shows the values of the magnetic properties of the sintered magnets obtained from the magnet alloy C of Example 1 and Comparative Example 1. In the magnetic characteristics of Example 1, the coercive force was greatly improved, and the residual magnetic flux density and the maximum energy product were also larger than those of Comparative Example 1.

Example 2 and Comparative Example 2 An alloy ingot having a composition formula of 13.0Nd-79.3Fe-1.7Co-6B was used as an A alloy, and a composition formula of 16Nd-22 was used as an B alloy.
An alloy ingot of Dy-3Fe-53Co-6B was produced in the same manner as in Example 1. Next, using 95% by weight of the A alloy and 5% by weight of the B alloy, a magnet alloy C of Example 2 was produced in the same manner as in Example 1 below. For comparison, a composition formula of 13.2 Nd-1.0 Dy-7 was used as an A alloy.
An alloy ingot of 6.9Fe-2.9Co-6B was
Composition formula 20Nd-10Dy-35Fe-2 as B alloy
Ingots of 9Co-6B were produced in the same manner as in Example 1. Next, 97 weight% of A alloy and B alloy 3
The magnet alloy C of Comparative Example 2 was produced in the same manner as in Example 1 using the weight%. Table 1 shows the values of the magnetic properties of the sintered magnets obtained from the magnet alloys C of Example 2 and Comparative Example 2.
Regarding the magnetic characteristics of Example 2, the residual magnetic flux density and the maximum energy product were greatly improved as compared with Comparative Example 2 even though the coercive force was almost equal.

(Examples 3-7, Comparative Examples 3-4) As shown in Table 2, according to the alloy compositions of Examples 3-7, respective A alloys and B alloys were prepared. A sintered magnet was produced in the same manner as in Example 1 under the conditions. For comparison, A alloys and B alloys were prepared according to the alloy compositions of Comparative Examples 3 and 4 as shown in Table 1, and sintered magnets were produced in the same manner as in Example 1 under the conditions of Table 1. Produced. Table 2 shows Examples 3 to
Table 7 shows the magnetic properties of the sintered magnets of Comparative Examples 3 and 4.
Comparative Examples 3 and 4 show that the magnetic properties are not improved when the amount of R in the A alloy is 12.4 to 14.0 atomic% at the time of a weak orientation magnetic field. Examples 3 to 7 show that the magnetic properties are improved by the strip casting method, hydrogenation, dehydrogenation, and strong magnetic field orientation by a pulsed magnetic field, indicating that the present invention is effective.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

According to the present invention, even in a strong magnetic field, which is difficult to carry out by the conventional two-alloy method, high orientation can be achieved without separating the A alloy and the B alloy.
A rare earth permanent magnet having a high residual magnetic flux density and a high coercive force can be manufactured. Therefore, the present invention
As a method for manufacturing high-performance magnets for various electric and electronic devices,
It is expected to be widely used.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 1/053 H01F 1/04 H

Claims (4)

[Claims] 1. A alloy (mainly composed of R ₂ TM ₁₄ B phase, R is at least one or more rare earth element mainly composed of Nd, Pr, Dy, Tb, TM is transition metal mainly composed of Fe, Co) Element) and a B alloy (an alloy containing R and TM and having an R content of 20 atomic% or more),
B alloy powder 1 to 30% by weight is mixed with 99% by weight,
After pressing the obtained mixed powder in a magnetic field to form a molded body, the molded body is sintered in a vacuum or an inert gas atmosphere,
In the method for producing a rare earth permanent magnet subjected to aging treatment at a low temperature equal to or lower than the sintering temperature, the amount of R in the A alloy is from 12.4 to
14.0 atomic%, and the mixed powder was treated with a magnetic field strength of 1.6.
A method for producing a rare-earth permanent magnet, which comprises performing pressure molding in a strong magnetic field of T or more. 2. The method for producing a rare earth permanent magnet according to claim 1, wherein the A alloy powder is produced by a strip casting method. 3. The method for producing a rare earth permanent magnet according to claim 1, wherein the A alloy powder or the mixed powder is subjected to hydrogenation and dehydrogenation. 4. The method for producing a rare earth permanent magnet according to claim 1, wherein the mixed powder is subjected to pressure molding by applying a pulse magnetic field having a magnetic field strength of 1.6 T or more.