JP3222482B2 - Manufacturing method of permanent magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Object of the invention]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a permanent magnet , and to improve the Curie temperature without deteriorating magnetic properties as compared with conventional Sm-Co-based and Nd-Fe-B-based magnets. And a method for manufacturing a permanent magnet.

[0003]

2. Description of the Related Art Conventionally known and mass-produced rare earth permanent magnets include Sm-Co magnets and Nd-Fe-B magnets. These magnets contain a rare earth element such as Sm, Nd, etc., as a property developing component. That is, the rare earth element brings about a very large magnetic anisotropy derived from the behavior of 4f electrons in the crystal field, thereby increasing the coercive force and realizing a high-performance magnet. Such high-performance magnets are mainly used for electrical devices such as speakers, motors, and measuring instruments.

[0004] However, rare earth elements are generally very expensive, and it is necessary to reduce the content of rare earth elements in order to reduce the cost of the above-mentioned high-performance magnet.

[0005] As a high-performance magnet material having a reduced rare-earth content, a 1-12 rare-earth iron-based intermetallic compound having a ThMn ₁₂ type crystal structure has recently attracted attention. This intermetallic compound can be formed by a conventional Sm ₂ Co ₁₇ magnet or N
As compared with the intermetallic compound constituting the d ₂ Fe ₁₄ B ₁ magnet, the raw material cost is low due to the small amount of stoichiometric logic rare earth, and the high saturation flux density Bs and high maximum energy because the ratio of Fe is relatively high. Product (BH) _max .

[0006]

However, the permanent magnet formed of the above-mentioned 1-12 rare earth iron-based intermetallic compound has a low Curie temperature (Tc) of generally about 300 ° C. and is used under high temperature conditions. There is a problem that it is difficult to apply the present invention to a field requiring high magnetic stability with respect to temperature, such as an apparatus, a motor, and a measuring instrument.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a permanent magnet in which the Curie temperature is improved without lowering the magnetic anisotropy. [Configuration of the invention]

[0008]

SUMMARY OF THE INVENTION The present inventors have minimized the use of expensive rare earth elements and raised the Curie temperature without impairing the magnetic anisotropy of the 1-12 compound. As a result of intensive research, when a permanent magnet containing a predetermined amount of at least one of nitrogen and carbon and having a main phase of a tetragonal rare earth iron-based compound having a Th-Mn ₁₂ type crystal structure was formed, The inventors have found that it is possible to greatly increase the Curie temperature, and have completed the present invention.

[0009] That is the manufacturing method <br/> permanent magnet according to the present invention the composition formula _{R x M y A z Fe 100} -x-y-z ( wherein R
Is at least one element selected from rare earth elements including Y, M is Si, Cr, V, Mo, W, Ti, Zr, H
at least one element selected from f and Al, A is at least one element selected from N and C,
X is 4 to 20% in atomic%, y is 20% or less, and z is 0.0
And the main phase is Th · Mn _12.
400-1000 ° C. for magnet alloy powder having type crystal structure
By performing hot pressing and integrally sintering under the above temperature conditions, the Curie temperature is 370 ° C. or higher and the coercive force (iH
c) is a permanent magnet of 8 KOe or more.

The reasons for limiting the composition of the permanent magnet according to the present invention as described above are as follows.

The R is La, Ce, Pr, N
d, Sm, Eu, Gd, Td, Dy, Ho, Er, T
Rare earth elements of m, Yb, and Lu and Y are mentioned, and one or a mixture of two or more of them is used. R brings about magnetic anisotropy to the material, and is added in the range of 4 to 20 atomic% in order to give high coercive force.

When the added amount of R is less than 4 atomic%, α-
A large amount of Fe or the like precipitates and the coercive force (iHc) is greatly reduced. On the other hand, when the addition amount of R exceeds 20 atomic%, the saturation magnetic flux density (Bs) is greatly reduced, and a large amount of expensive rare earth element is used, which leads to an increase in manufacturing cost. And it becomes disadvantageous.

As the M element, Si, Cr, V, Mo,
One or a mixture of two or more selected from W, Ti, Zr, Hf and Al is used. Rare earth element R
And Fe alone cannot form a stable crystal structure, but by adding the above-mentioned M element within a range of 20 atomic% or less, a rare-earth iron-based tetragonal compound having a stable ThMn ₁₂ type crystal structure can be formed. can do. In addition,
The element M exhibits the above-mentioned effects when added in a small amount, but is preferably 0.1 atomic% or more.

When the addition amount of the element M exceeds 20 atomic%,
Since the saturation magnetic flux density (Bs) is greatly reduced, M
The addition amount of the element is set to 20 atom% or less.

The element A comprising at least one of C and N is an element effective for improving the Curie temperature (Tc). That is, C and N modulate the band structure of Fe, in particular, increase the magnetic polarization of d electrons and cause exchange interaction between d electron spins, and ultimately the Curie temperature (T
It is effective for increasing c). However, it is difficult to form a solid solution exceeding 16 atomic%, and an excessive addition causes instability of the crystal structure. Therefore, an addition exceeding 16 atomic% is not suitable. On the other hand, when the content is 0.001 at% or less, the effect of improving the Curie temperature (Tc) is not remarkable, so the addition amount of the element A is set in the range of 0.001 to 16 at%.

By substituting a part of Fe with a transition metal other than Fe, such as Co-Ni, the Curie temperature of the magnet can be further improved and the coercive force can be increased. However, if more than 50 atomic percent of iron is replaced,
Since the magnetic properties such as the saturation magnetic flux density are remarkably reduced, the substitution amount is desirably 50% or less of Fe in atomic fraction. In order to minimize the amount of expensive Co used, the amount of substitution is preferably within the above range.

Next, a method for manufacturing a permanent magnet according to the present invention will be described.

First, when C is solely added as the A element, a predetermined amount of the Fe, R, M, and A elements is melted by a method such as arc melting or the like, and then cast to prepare an alloy having a predetermined composition.

On the other hand, when N alone is added as the A element or N and C are added in a complex manner, first N
After preparing an alloy composed of components excluding the components by the above-described method, the prepared alloy is pulverized so as to have a particle size of 1 mm or less, preferably 0.5 mm or less. Thereafter, the pulverized material is placed in an N ₂ atmosphere of 20 to 1500 Torr for 300 to 1
A heat treatment is performed at 000 ° C. to occlude N ₂ in the pulverized material to produce an alloy having a predetermined composition. In this case, if necessary, N ₂
Before the occlusion treatment, the molten alloy may be heat-treated at 500 to 1000 ° C. to form a solution.

Next, the alloy obtained in this manner was used,
After finely pulverizing to 50 μm, the obtained raw material powder is filled in a predetermined mold, and hot pressed under a temperature condition of 400 to 1000 ° C. to perform integrated sintering. At this time, by pre-orienting the raw material powder in a magnetic field, a permanent magnet having higher anisotropy can be obtained. It is also possible to hot-work the obtained sintered body to express anisotropy. Note that the hot press treatment is desirably performed in an N ₂ gas atmosphere in order to prevent the N component once absorbed in the alloy from dissipating. However, in an alloy containing no N component,
It may be carried out in an inert gas such as Ar gas or in a vacuum.

The coercive force can be increased by subjecting the sintered body obtained by hot pressing to a heat treatment at a temperature of 300 to 900 ° C. for 0.1 to 5 hours.

The permanent magnet according to the present invention is produced by melting, casting, pulverizing, and sintering a predetermined composition as described above. It is also possible to manufacture by the method described below, and the manufacturing method will be described below.

First, when C is solely added as the element A, a mixture of powders containing predetermined amounts of R, Fe, M, and A components is alloyed by a solid-phase reaction. As a method of causing a solid-phase reaction, for example, a mechanical alloying method in which a raw material mixture is charged into a planetary ball mill, a rotary ball mill, an attritor, a vibrating ball mill, a screw ball mill, and the like, and the powder particles are mechanically alloyed is employed. it can.

According to this mechanical alloying method, the raw material powder particles are pulverized into flakes, and heterogeneous atoms are mutually diffused at portions where the flakes are in surface contact with each other, whereby the raw material mixture is homogeneously integrated. You.

When N is contained as the component A, the above solid phase reaction is carried out in an N ₂ gas atmosphere, and the N ₂ gas is absorbed in the raw material mixture to form an alloy powder having a predetermined composition. Can be prepared.

[0026]

Alloy powder prepared by the above solid-phase reaction
Performs hot pressing. Place to do this hot press
It is desirable to perform in an N ₂ gas atmosphere in order to prevent the combined N ₂ component from dissipating. Similarly, alloys containing no N component can be treated in other inert gases or in vacuum.

By performing hot pressing instead of such heat treatment, the alloy obtained by the solid phase reaction can be more firmly integrated.

Further, in order to further improve the magnetic properties of the permanent magnet, the sintered body formed by hot pressing may be further heat-treated at the above-mentioned temperature. Further, the magnetic orientation can be further enhanced by applying plasticity to the sintered body by applying pressure.

In addition to the above two manufacturing methods, an alloy powder having a predetermined composition can be prepared by a liquid quenching method, and the obtained powder can be sintered and integrated to form a permanent magnet. In this case, an alloy powder having particularly high coercive force can be obtained by the liquid quenching method, and a permanent magnet having excellent magnetic properties can be obtained.

In order to manufacture a bonded magnet from the heat-treated alloy, a method is used in which a powdery alloy is mixed with an epoxy resin, a nylon resin, or the like, and then molded. As a molding method, when the resin is an epoxy-based thermosetting resin, after compression molding, a curing treatment is performed at a temperature of 100 to 200 ° C., and when the resin is a nylon-based thermoplastic resin, injection molding may be used.

The permanent magnet according to the present invention is mainly composed of a compound phase having a stable tetragonal ThMn ₁₂ type crystal structure. In particular, since at least one of N and C is added, the Curie temperature (Tc) is reduced. Higher than the conventional binary or ternary compounds, they exhibit extremely excellent magnetic properties.

[0033]

Next, the present invention will be described more specifically based on the following examples.

Examples 1 to 3 and Comparative Examples 1 to 3 As Examples 1 to 3, high-purity Sm, Ti, Si, and Fe powders were prepared in the composition shown in Table 1 and melted in a high-frequency melting furnace.
Each ingot was prepared by pouring into a mold. Next, each of the ingots is averaged in a particle size of 150 to 200 μm by a jet mill.
m. Next, each of the obtained alloy powders was subjected to a heat treatment at a temperature of 500 ° C. for 1 hour in a 750 Torr N ₂ gas atmosphere. Further, each alloy powder was added with an average particle size of 3
μm, and oriented in a magnetic field of 20 KOe to form a green compact.
Hot pressing was performed in a N ₂ gas atmosphere of 00 Torr. Each of the obtained hot-pressed sintered bodies is heat-treated at a temperature of 600 ° C. for 1 hour in a 600 Torr N ₂ gas atmosphere, and the residual magnetic flux density (Br), coercive force (iHc),
The maximum energy product (BH) _max and the Curie temperature (Tc) were measured, and the results shown in Table 1 were obtained.

On the other hand, as Comparative Examples 1 to 3, Examples 1 to 3
Using the ingot prepared in the above, magnet bodies were similarly prepared in a state where the N component was not occluded, and their magnetic properties were measured. That is, each ingot used in Examples 1 to 3 was finely pulverized to an average particle size of 3 μm, and each obtained powder was
After being oriented by an Oe magnetic field to obtain a green compact, hot pressing was performed at 800 ° C. in an Ar gas atmosphere of 400 Torr. Next, each of the obtained sintered bodies is subjected to 400 Torr at 600 ° C.
After performing a heat treatment for 1 hour in an Ar gas atmosphere, the magnetic properties were measured. The results shown in Table 1 below were obtained.

[Margin below]

[0037]

[Table 1]

As is clear from the results shown in Table 1, according to Examples 1 to 3, since the rare earth iron-based tetragonal compound constituting the magnet is stabilized by N, it is compared with Comparative Examples 1 to 3. It has been found that the magnetic properties are excellent, and the Curie temperature (Tc) is particularly greatly improved.

When the crystal structures of the magnet bodies prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were measured by an X-ray diffraction method, it was found that all of them had a ThMn ₁₂ type crystal structure. confirmed.

Examples 4 to 9 As Examples 4 to 6, rare earth powders having an average particle size of 0.5 mm, Fe, Mo, and the like having an average particle size in the range of 5 to 40 μm.
Each of the Si, Ti, and C powders was prepared to have the composition shown in Table 2 to prepare a raw material mixture. Each of the obtained raw material mixtures was put into a ball mill, and pulverized and mixed in an Ar gas atmosphere for 60 hours. The raw material powder was alloyed with a mechanical alloy.

Next, each of the obtained alloy powders was filled in a molding die, and hot pressed at 800 ° C. in an Ar gas atmosphere to form a magnet body. The magnetic properties of each of the obtained magnet bodies were measured in the same manner as in Examples 1 to 3, and the results shown in Table 2 were obtained.

The powders of the respective elements are shown in Table 2 as Examples 7 to 9.
Formulated into compositions shown in raw material mixture was prepared, obtained and put into the raw material mixture in a ball mill, a N ₂ gas was 180 hours pulverized and mixed under N ₂ gas atmosphere of 760Torr to each raw material powder While occluded, alloyed with a mechanical alloy.

Next, each of the obtained alloy powders was filled in a molding die, and hot pressed at 800 ° C. in an N ₂ gas atmosphere of 600 Torr to form a magnet body. The magnetic properties of the obtained magnet bodies were measured in the same manner as in Examples 4 to 6, and the results shown in Table 2 below were obtained.

[0044]

[Table 2]

As is clear from the results shown in Table 2, C was added in Examples 4 to 6 to stabilize the crystal composition and increase the Curie temperature, and in Examples 7 to 9, C was added.
Since N and N are added in combination, a magnet having excellent magnetic properties and a high Curie temperature (Tc) is obtained.

[0046]

As described above, according to the present invention, since a rare earth iron-based tetragonal compound having a stable ThMn ₁₂ type crystal structure containing at least one of N and C is formed as a main phase, the magnetic properties are improved. A permanent magnet having a high Curie temperature can be provided without deteriorating characteristics.

Continuation of front page (56) References JP-A-63-273302 (JP, A) JP-A-62-136550 (JP, A) JP-A-5-65603 (JP, A) Less-Common Met. 136 (1988), p. 207-IEEE Trans. Mag. , Mag-23 (1987), pp. 3101-(58) Fields investigated (Int. Cl. ⁷ , DB name) H01F 1/08 H01F 1/04 C22C 38/00

Claims (1)

(57) [Claims] 1. A composition formula _R x _M y _A z Fe
_100-xyz (wherein R is at least one element selected from rare earth elements including Y, M is Si, Cr,
At least one element selected from V, Mo, W, Ti, Zr, Hf and Al, A is at least one element selected from N and C, and x is 4 to 2 in atomic%.
0%, y is 20% or less, and z is 0.001 to 16%), and the main phase has a Th.Mn _12- type crystal structure. A method for producing a permanent magnet, wherein a permanent magnet having a Curie temperature of 370 ° C. or more and a coercive force (iHc) of 8 KOe or more is obtained by pressing and integrally sintering.