JP2002313614A - Magnet material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide magnet material improved in thermal stability for the manufacture of a high-performance magnet that has a high saturation magnetization and large magnetic anisotropy. SOLUTION: This magnetic material is a compound represented by a formula, Rx Ny (Crz Siu M1-z-u )1-x-y (wherein, R contains at least one or more kinds of elements selected out of a first group composed of Y and rare earth elements, M contains one or more elements selected from a second group composed of Fe and Co, and (x), (y), (z), and (u) are so set as to satisfy the following formulas, 0.04<=x<=0.2, 0.001<=y<=0.2, 0.005<=z<=0.2, and 0.005<=u<=0.2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnetic material.

[0002]

2. Description of the Related Art Conventionally, Sm-Co-based magnets, Nd-Fe-B-based magnets and the like have been known as high-performance rare earth permanent magnets, and their mass production is currently in progress. These magnets contain a large amount of Fe or Co, which contributes to an increase in saturation magnetization. Also, the rare earth elements in these magnets are
Very large magnetic anisotropy results from the behavior of 4f electrons in the crystal field. Thereby, the coercive force is increased, and a high-performance magnet is realized. Such high-performance magnets are mainly used for electric devices such as speakers, motors, and measuring instruments.

[0003] In recent years, there has been an increasing demand for miniaturization of various electric appliances, and in order to meet the demand, a higher-performance permanent magnet having an improved maximum magnetic energy product (BH _max ) of the permanent magnet has been required.

As a material for obtaining a higher-performance permanent magnet, a combination of a rare earth element and a transition metal element such as Fe is also considered promising.
-N-based materials have been announced by Coey et al. Sm-Fe-N-based materials have high saturation magnetization comparable to Nd-Fe-B-based materials and large magnetic anisotropy that surpasses Nd-Fe-B-based materials. Is expected.

However, Sm-Fe-N-based materials have a disadvantage that they are thermally decomposed by heating at about 550 ° C. or higher, so that they cannot be densified by sintering, and are currently limited to applications as bond magnets. I have.

The thermal decomposition of the Sm-Fe-N material described above
Some attempts to curb after Coey et al.'S announcement
Has been done by a research group. For example, Sugimoto et al.
Sm _TwoFe₁₇Al, Si, T
i, V, Cr, Mn, Co, Ni, Ga, Zr, Nb,
Compounds that have been subjected to nitridation by substitution with various elements such as Mo
The thermal decomposition behavior was investigated in detail. Specifically, these
The temperature of the compound is increased and Sm_TwoFe₁₇N_xPhase X-ray diffraction
The intensity decreases and the diffraction intensity of SmN and α-Fe increases.
The starting temperature is defined as the pyrolysis temperature, and this pyrolysis temperature is measured.
Has been established. And about 10 atomic% of Fe is Cr
In the case of the substituted compound, the thermal decomposition temperature is about 661 ° C.
And found that the pyrolysis temperature increased (Proceeding
s of 12^th International Workshop on RE Magnets and
 Their Applications (1992) p218). Also, part of Fe
Is not as good as Cr when Si is replaced with Si,
The decomposition temperature becomes about 600 ° C, and the thermal decomposition temperature also rises
To find that.

[0007] However, even when a part of these Fe is replaced by Si or Cr, the decomposition temperature stops increasing when about 10 atomic% or more is replaced, and no further effect can be obtained. Therefore, the thermal stability has not yet been improved to a temperature of about 700 ° C. or higher. Therefore, when densification is performed by means such as hot pressing, a high molding pressure is required, and there is a problem from the viewpoint of mold consumption.

[0008]

As described above, high-performance magnets having high saturation magnetization and high magnetic anisotropy have a problem of low thermal stability at present.

The present invention has been made in view of the above circumstances, and has as its object to achieve high saturation magnetization,
An object of the present invention is to provide a magnet material having improved thermal stability in a high-performance magnet having a large magnetic anisotropy.

[0010]

Therefore, in the present invention, R _x
N _y (Cr _z Si _u M _1-zu ) _1-xy (where R contains at least one or more elements selected from the first group consisting of Y and rare earth elements, and M is the second consisting of Fe and Co) At least one element selected from the group,
≦ x ≦ 0.2, 0.001 ≦ y ≦ 0.2, 0.005 ≦
wherein z ≦ 0.2 and 0.005 ≦ u ≦ 0.2).

In the magnet material of the present invention, 20 atomic% or less of M is used for Ti, V, Mn, Ni, Cu, Zn, Zr,
It may be replaced with at least one element selected from the third group consisting of Nb, Mo, Hf, Ta, W, Al, Ga and Ge.

[0012] The magnetic material of the present invention is characterized in that 50% of N
Atomic% or less may be replaced by at least one element selected from the fourth group consisting of H, B and C.

Further, the magnetic material of the present invention is Th ₂ Zn ₁₇
A type crystal structure or a Th ₂ Ni ₁₇ type crystal structure may be used as a main phase.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Conventionally, Fm of Sm-Fe-N based material
When e is replaced by another element, for example, when replaced by Cr, the decomposition temperature increases as the replacement amount increases,
The temperature reached about 661 ° C. when about 10 atomic% was replaced. However, even if Fe is further replaced by Cr, the decomposition temperature does not rise. In the case of substitution with Si, the decomposition temperature similarly rises only to about 600 ° C.

The factors governing thermal stability are complex,
When the crystal structures are the same, it is considered that the thermal stability is sensitive to (1) the distance between each atom and (2) the number of 3d electrons.

In order to improve the thermal stability under the above conditions, various materials were examined.
When Fe of the -N-based material is replaced by Cr, the average number of 3d electrons changes to increase the thermal stability of the crystal, and when replaced by Si, the effect of reducing the unit cell of the crystal is remarkable,
It has been found that this improves the thermal stability. And, since the difference in the mechanism of such thermal stability improvement was found, in the present invention, the Sm—Fe—N-based material Fe
Was replaced with both Cr and Si, an optimum magnet material was obtained.

Therefore, in the present invention, the magnet material
As R_xN_y(Cr_zSi_uM_{1-z -u})_1-xy(However
R is selected from the first group consisting of Y and rare earth elements
M contains at least one element, M is Fe and Co
At least one element selected from the second group
0.04 ≦ x ≦ 0.2, 0.001 ≦ y ≦ 0.
2, 0.005 ≦ z ≦ 0.2, 0.005 ≦ u ≦ 0.2
Is included).

That is, Fe of the Sm—Fe—N based material is converted to C
Optimum properties are obtained when substitution is made with both r and Si. When the Fe of the Sm-Fe-N-based material is replaced with Cr or replaced with Si, the decomposition temperature, which has only increased to a certain temperature, is reduced by replacing both with Cr and Si. And a higher decomposition temperature than the conventional one is obtained.

Hereinafter, the magnet material R _x N _y (Cr _z S) of the present invention will be described.
i _u M _1-zu ) _1-xy (where R includes at least one element selected from the first group consisting of Y and rare earth elements, and M represents at least one selected from the second group consisting of Fe and Co) It contains one or more elements, and 0.04 ≦ x ≦ 0.
2, 0.001 ≦ y ≦ 0.2, 0.005 ≦ z ≦ 0.
2, 0.005 ≦ u ≦ 0.2) will be described in detail. (1) RR contains at least one or more elements selected from the first group consisting of Y and rare earth elements. All of these elements bring a large magnetic anisotropy to the magnet material and impart a high coercive force. R is preferably blended in a range of about 4 to 20 atomic% based on the total of M, Cr and Si in the magnet material. If the compounding ratio of R is less than about 4 atomic%, a large amount of α-Fe precipitates and a large coercive force cannot be obtained, while if it exceeds about 20 atomic%, the saturation magnetization is remarkably reduced, which is not preferable. A more preferable compounding ratio of R is about 8 to 12 atomic%, and further preferably about 9 to 11 atomic%.
As R, it is preferable to use Sm, Nd, and Pr, and particularly, Sm is preferably used. By setting Sm to about 50 atomic% or more, preferably about 70 atomic% or more of R, it is effective to enhance the performance of the magnet material, especially the coercive force. (2) N N mainly exists at the interstitial position (intrusion position) of the main phase in the crystal, and enlarges the crystal lattice and changes the electronic structure as compared with the case where N is not included. This has the function of improving the Curie temperature, magnetic anisotropy, and saturation magnetization. The compounding ratio of N is preferably about 0.1 to 20 atomic% with respect to the total of M, Cr and Si in the magnet material. About 0.1 atomic% of N
If the amount is less than the above, the effect of adding N cannot be sufficiently obtained. On the other hand, if the amount exceeds about 20 atomic%, the saturation magnetization decreases, which is not preferable. A more preferable N compounding ratio is about 10 to 15 atomic%. The same effect can be obtained by substituting about 50 atomic% or less of N with at least one element selected from the fourth group consisting of H, B, and C. If the substitution by H, B, or C exceeds about 50 atomic%, the magnetic anisotropy is significantly reduced, which is not preferable. (3) MM contains at least one element selected from the second group consisting of Fe and Co. This is mainly responsible for the magnetization of the magnet material. The saturation magnetization of the magnet material can be increased by adding a large amount of M, but if it is added excessively, the coercive force may be reduced due to the precipitation of α-Fe. In addition, about 20 atom% or less of M
Ti, V, Mn, Ni, Cu, Zn, Zr, Nb, M
A similar effect can be obtained when substituted with at least one element selected from the third group consisting of o, Hf, Ta, W, Al, Ga, and Ge. There are also effects such as suppression of precipitation and formation of a grain boundary phase to increase coercive force. However, it is not preferable to replace M by more than about 20 atomic% with these elements, since the saturation magnetization is significantly reduced. (4) Cr, Si Cr and Si are effective elements for improving the thermal stability of the magnet material of the present invention and increasing the thermal decomposition temperature.
These elements mainly replace the sites occupied by M in the main phase. Cr improves the thermal stability of the crystal by changing the number of d electrons in the crystal. Further, Si enhances the thermal stability of the crystal by reducing the size of the crystal lattice.

If the compounding ratio of Cr is less than about 0.5 atomic% of the total of M, Cr and Si, the effect of compounding Cr cannot be sufficiently obtained. On the other hand, if the mixing ratio of Cr is larger than about 20 atomic% of the total of M, Cr, and Si, the saturation magnetization decreases. More preferred C
The compounding ratio of r is about 5 to 5 of the total of M, Cr, and Si.
15 atomic%.

If the mixing ratio of Si is less than about 0.5 atomic% of the total of M, Cr and Si, the effect of mixing Si cannot be sufficiently obtained. On the other hand, the compounding ratio of Si is set to about 20 atomic% of the total of M, Cr, and Si.
If it is larger, the saturation magnetization decreases. A more preferable mixing ratio of Si is about 5 to 15 atomic% of the total of M, Cr, and Si.

The magnetic material of the present invention can be made of Th ₂ Zn ₁₇ phase, Th ₂ Ni ₁₇ phase, T ₂
BCU ₇ phase, ThMn ₁₂ phase, R ₃ Fe ₂₉ phase (R is Y or a rare earth element) may be, eg a main phase, Th ₂ Z
When the n ₁₇ phase or the Th ₂ Ni ₁₇ phase is the main phase, particularly high magnet properties can be obtained. Here, the main phase means the phase having the largest volume occupancy among the crystalline phases and the amorphous phases constituting the magnet material. Further, the magnet material of the present invention allows inclusion of unavoidable impurities such as oxides.

Next, an example of a method for manufacturing a magnet material according to the present invention will be described.

First, an alloy powder containing predetermined amounts of R, Cr, Si, and M elements is prepared. The alloy powder can be obtained by pulverizing the alloy ingot obtained by casting after arc melting or high frequency melting, and it is also possible to prepare the alloy ribbon by the liquid quenching method and then pulverize it to adjust the alloy powder. it can.
Further, as another method of preparing the alloy powder, a mechanical alloying method, a mechanical grinding method, a gas atomizing method, a reduction diffusion method, or the like may be adopted.

The alloy powder thus obtained or the alloy before pulverization may be subjected to a heat treatment, if necessary, to homogenize it. It is also possible to control the type and volume occupancy of the main phase by adjusting the alloy powder and heat treatment conditions.

Next, N is added to the alloy powder to complete a magnet material. As this method, about 0.1
It is desirable to perform the heat treatment at a temperature of about 300 to 900 ° C. for about 0.1 to 100 hours in a nitrogen gas atmosphere of about 100 atm. As the atmosphere for this heat treatment, a nitrogen compound gas such as ammonia may be used instead of the nitrogen gas. The nitridation reaction can be controlled by using a mixture of a nitrogen gas or a nitrogen compound gas and a hydrogen gas. It is possible to partially replace N with H by using a nitrogen compound gas such as ammonia or by mixing hydrogen gas. When a part of N is replaced with C and B, C and B may be contained in the alloy powder before the nitrogen-containing treatment, or it may be contained using a carbon compound gas or the like.

When a magnet body is manufactured from the magnet material of the present invention, a magnet material containing a predetermined amount of R, N, Cr, Si, M is hot pressed, hot isostatically pressed, discharge plasma sintered or the like. It can be manufactured by being integrated as a compact having a high density. Since the magnetic material of the present invention has high thermal stability as described above, molding at a higher temperature is possible, and it becomes possible to obtain a dense molded body with a lower molding pressure as compared with the related art.

The magnetic material of the present invention can be used as a bonded magnet. As the binder, a resin such as an epoxy-based resin or a nylon-based resin may be used as before, but it is also possible to manufacture a metal-bonded magnet using a low-melting-point metal or a low-melting-point alloy as a binder.
Also in this case, since the magnetic material of the present invention has high thermal stability, the kinds of binders that can be used are increased, and there is an advantage that a high-performance bonded magnet can be provided at lower cost.

Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. (First to Eighth Embodiments) First, the respective raw materials are prepared at the composition ratios shown in (Table 1), and are melted by high frequency in an Ar atmosphere to produce a mother alloy ingot. Subsequently, the mother alloy ingot is heat-treated at about 1000 ° C. for about 3 days in an Ar atmosphere, and then pulverized to about 45 μm or less using a mortar. Subsequently, this alloy powder is subjected to a heat treatment at a temperature (nitriding temperature) shown in (Table 1) for about 4 hours in a nitrogen gas atmosphere of about 1 atm to obtain magnet materials of the first to eighth embodiments, respectively. . (Comparative Examples 1 to 3) A magnet material is formed in the same manner as in the first to eighth embodiments, except that the composition ratio of each raw material and the nitriding temperature are as shown in Table 1.

[0030]

[Table 1]

When the generated phase for producing the magnet material of each embodiment and each comparative example was examined by X-ray diffraction using X-rays using CuKα as a radiation source, all of the magnet materials of the first to eighth embodiments were mainly used. It was confirmed that the phase was a Th ₂ Zn ₁₇ phase. FIG. 1 shows the result of X-ray diffraction of the magnet material of the first embodiment. From FIG. 1, it can be seen that all the diffraction peaks are indexed by a Th ₂ Zn ₁₇ type structure except for a slight peak from α-Fe, and are almost a single phase of the Th ₂ Zn ₁₇ phase.

Further, in order to confirm the thermal decomposition temperature of the magnetic material of each embodiment and each comparative example, DSC measurement was performed. The measurement conditions were about 20 ° C./min, and the measurement of the thermal decomposition temperature was performed at the peak value of the thermal decomposition. (Table 1) shows the peak value of thermal decomposition (DSC peak temperature) of each embodiment and each comparative example.
Is shown. FIG. 2 shows a DSC measurement result of the first embodiment as an example of the measurement result. FIG. 2 shows that in the case of the magnet material of the first embodiment, a large peak indicating thermal decomposition of the compound is observed at about 820 ° C. The reaction start temperature in this DSC measurement is about 750 ° C., and the definition of the thermal decomposition temperature described by Sugimoto et al. In the prior art is considered to be close to the reaction start temperature.

In the comparative example, the thermal decomposition temperature of the magnet material of Comparative Example 1 in which neither Si nor Cr was added was the lowest,
In Comparative Examples 2 and 3, in which Cr and Si were independently added, although the thermal decomposition temperature was high, they did not reach each embodiment of the present invention.

In each embodiment, since both Cr and Si are contained, the magnet material has a high thermal decomposition temperature and good thermal stability. Further, it can be seen that the same effect can be obtained even when the mixing ratio of Cr or Si is changed within the range of the present invention. Furthermore, similar effects can be obtained even if the compounding ratio of the substance and the raw material is not in these embodiments, as long as it is within the scope of the present invention. (Ninth to eleventh embodiments) Using the magnet materials of the sixth to eighth embodiments, the temperature is about 770 ° C and the pressure is about 220M.
Hot pressing was performed as Pa to produce magnet bodies, which were set as the ninth to eleventh embodiments, respectively. This creation condition is
Conventionally, the temperature was set to about 550 ° C. and the pressure was set to about 1000 MPa. Therefore, it can be said that the temperature is higher and the pressure is lower than before.

The density (magnet density) of these magnets was about 7.5 to 7.9 g / cm ^{3 as} shown in Table 2. When the coercive force, residual magnetization, and maximum energy product of these magnets were measured, as shown in Table 2, each magnet had a coercive force of about 600 to 900 kA / m and a residual magnetization of about 0.7 kA / m. ~ 0.9T, maximum energy product is about 80
It was confirmed to have excellent magnetic properties of 100 kJ / m ³ .

[0036]

[Table 2]

Therefore, by forming a magnet body using the magnet material of the present invention, it is possible to obtain excellent magnetic properties, and it is possible to produce a dense compact at a low molding pressure because of its high thermal stability. The effect is obtained.

[0038]

As described in detail above, according to the present invention,
It is possible to provide a magnet material which improves the thermal stability of a high-performance magnet having a high saturation magnetization and a large magnetic anisotropy, and capable of producing a dense compact at a low molding pressure with little consumption of a mold.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a magnetic material according to a first embodiment of the present invention;
It is a figure which shows a line diffraction pattern.

FIG. 2 is a graph showing D of the magnet material according to the first embodiment of the present invention.
It is a figure showing an SC measurement result.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Takahiro Hirai 1 Toshiba R & D Center, Komukai Toshiba, Kawasaki-shi, Kanagawa F-term (reference) 4K018 AA12 AA27 AB03 AC03 BA06 BA18 BC01 BD01 DA33 EA02 EA13 FA44 KA45 5E040 AA06 BD01 CA01 HB15 NN01

Claims (4)

[Claims] 1. R _x N _y (Cr _z Si _u M _1-zu ) _1-xy (where R contains at least one element selected from the first group consisting of Y and rare earth elements, and M is Fe and Co
At least one element selected from the second group consisting of 0.04 ≦ x ≦ 0.2, 0.001 ≦ y ≦ 0.
2, 0.005 ≦ z ≦ 0.2, 0.005 ≦ u ≦ 0.2
The magnetic material is a compound represented by the formula: 2. The method according to claim 1, wherein 20% by atom or less of M is
i, V, Mn, Ni, Cu, Zn, Zr, Nb, Mo,
2. The magnet material according to claim 1, wherein said magnet material is substituted with at least one element selected from the third group consisting of Hf, Ta, W, Al, Ga and Ge. 3. A method according to claim 1, wherein 50% by atom or less of said N is H,
2. The magnet material according to claim 1, wherein said magnet material is substituted with at least one element selected from the fourth group consisting of B and C. 4. A Th ₂ Zn ₁₇ type crystal structure or Th ₂ N
claim, characterized in that the i ₁₇ type crystal structure as a main phase 1
4. The magnet material according to any one of claims 1 to 3.