JPH07166204A - Rare earth-iron-based permanent magnet alloy powder and bond permanent magnet - Google Patents

Abstract

PURPOSE:To produce a rare earth-iron-based permanent magnet alloy powder and a bond permanent magnet improved in magnetic properties, particularly improved in saturation magnetic flux density by improving the compsn. of a binary rare earth-iron compound. CONSTITUTION:In rare earth-iron-based permanent magnet alloy powder consisting of rare earth elements-iron-oxygen-the elements to be added, the internal structure of each grain of rare earth-iron-based permanent magnet alloy powder expressed by the general formula Rd(Fe1-gCog)100-a-e-fOeMf (where R denotes one or >= two kinds of rare earth elements elected from all lanthanoids, M denotes one or >= two kinds among Ti, V, Si and Mo and, by atom, 4<=d<=20, 1<=e<=10, 0<=f<=10 and 0<=g<=1 are satisfied) is formed of a two phase mixed state of a phase rich in oxygen and a phase contg. no oxygen. Moreover, the rare earth-iron-based permanent magnet alloy powder is pulverized, is kneaded with a binder and is formed to obtain the bond permanent magnet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth-iron based magnet alloy powder having excellent magnetic properties, particularly a large saturation magnetic flux density, and a bonded permanent magnet using the same.

[0002]

2. Description of the Related Art At present, a rare earth-iron-boron (R-Fe-B) -based permanent magnet alloy, which is a permanent magnet alloy which has been particularly attracting industrial attention, improves the magnetic properties of rare earth-iron binary compounds. Therefore, B of the third element is added to the rare earth-iron-based alloy to generate an intermetallic compound having a new crystal structure, and its high magnetic properties, particularly high saturation magnetic flux density and large anisotropic magnetic field Applications are expanding in the field of electronic alloys.

[0003]

However, R-Fe-B
Permanent magnet alloys are susceptible to the fate of the alloy, oxidation, and oxidation during the manufacturing process is a factor that significantly reduces magnetic properties. It is necessary to manufacture with large-scale equipment. Further, since the rare earth-iron compound consisting of only a binary system that does not use the third element B does not combine high saturation magnetic flux density, high Curie temperature, and large uniaxial crystal magnetic anisotropy, which are the three elements of the permanent magnet, The improvement is desired.
The present invention focuses on this binary rare earth-iron compound, and improves the composition thereof to improve magnetic properties, in particular, saturation magnetic flux density, and rare earth-iron permanent magnet alloy powder and bond permanent formed by molding the powder. It is intended to provide a magnet.

[0004]

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to solve such problems, and reversely utilize oxidation.
The present inventors have found a bonded permanent magnet having a high saturation magnetic flux density by improving the magnetic properties by effectively using oxygen in this R-Fe alloy compound, and the gist thereof is a rare earth element-iron-oxygen-added element. rare earth consists - in iron-based permanent magnet alloy powders of the general formula _{R d (Fe 1-g Co} g)
_100-def O _e M _f (where R is one or more rare earth elements selected from all lanthanoid elements including Y, M is one or more of Ti, V, Si and Mo) 4 ≦ d ≦ 20, 1 ≦ e ≦ 10, O ≦ f ≦ 10 each atomic%,
O ≦ g ≦ 1 atomic ratio. ), The internal structure of the individual particles of the rare earth-iron-based permanent magnet alloy powder is composed of a two-phase hybrid state of an oxygen-rich phase and an oxygen-free phase. It is a bond permanent magnet that is an alloy powder and is obtained by finely pulverizing the rare earth-iron-based permanent magnet alloy powder, kneading it with a binder, and molding.

The present invention will be described in detail below.

According to the research conducted by the present inventor, it was found that in the oxidation of this R-Fe alloy compound, the R-rich phase remarkably progressed in the initial stage and gradually transitioned to the main phase. The velocity was found to be several orders of magnitude slower in the main phase than in the R-rich phase. Further, when oxygen enters the main phase rare earth-iron-based alloy, it penetrates between the crystal lattices without changing the crystal structure and consequently serves to expand the crystal lattice, and due to its volume effect, magnetic characteristics, In particular, it was found that the saturation magnetic flux density is increased, the Curie temperature is increased, and uniaxial anisotropy is generated. In the present invention, the rare earth element R is an important element for realizing magnetic anisotropy by exchange interaction with Fe, and its type is all lanthanoid elements including Y, such as La, Ce, Pr. , Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm,
It is effective for one or more rare earth elements selected from the group consisting of Yb and Lu, and has a large effect of improving magnetic properties.

However, if R is simply used, its effect is halved, but among the light rare earth elements, Ce and N
By combining d, Pr, Sm and other rare earth elements, it was found that the effect was significantly increased. R must be in the range of 4 to 20%, preferably 5 to 16% in atomic percentage. If it is less than 4%, a sufficient coercive force cannot be obtained, and if it exceeds 20%, pure rare earth metal precipitation occurs. The magnetic properties of the alloy, especially the saturation magnetic flux density, decrease,
It has low performance as a practical alloy.

As the additive element (M), Ti, V, Si, M
O and the like have a great effect on the rare earth-iron system, especially the R ₁ (Fe, M) ₁₂ system. It is known that these elements have a function of stabilizing the crystallinity of the R ₁ (Fe, M) ₁₂ intermetallic compound, and even if added in a too large amount, the original magnetic characteristics, especially the saturation magnetic flux density Therefore, the range is preferably 10 atomic% or less. Fe can be replaced with Co in any amount.

Oxygen (O) was disliked as an unnecessary element for magnet alloys, but it has become clear that it is a promising element as a metal-gas reaction system, in other words, as an interstitial interstitial element. . Ordinary R-Fe based alloys, here by way of example R ₂ Fe ₁₇ and R ₁ (Fe, M) ₁₂ based alloys, especially where M is T
Let us describe the behavior of oxygen for i, V, Si, and Mo.

When oxygen (O) ions penetrate the crystal lattice of these alloys, the O ions penetrate around the R ions, and O-2p and R-5d electrons, O-2p and Fe- 3d
Hybridizes with electrons, lowers free energy and stabilizes.
Due to the hybridization of O-2p and Fe-3d electrons, a non-bonded state is created near the Fermi level of the upward spin band. The unbound state is localized near the O ion, reducing the spin moment of the closest Fe ion. Non-bonded state is O <N
The decrease becomes larger in this order because the Fermi level can be increased in the order of <C <B. The non-bonded hybrid state of O-2p and Fe-3d electrons is large near the empty 3d band, and the unoccupied downward spin band is pushed up more strongly than O-2p electron. This is the same action as the strong exchange interaction, and Fe ions separated from O ions realize the same strong ferromagnetism as Co in which the upward spin band is completely occupied.
The moment increases and the Curie temperature rises. R ₂ F
In the e ₁₇ and R ₁ (Fe, M) ₁₂ systems, they work effectively in the order of B <C <N <O. Therefore, high saturation magnetic flux density, high Curie temperature, and large magnetocrystalline anisotropy required for permanent magnet alloys are expected.

From these theoretical backgrounds, rare earth elements--
Oxygen, which is regarded as a promising third element of the iron-based alloy, has its effect halved even if it is contained in a too large amount. The oxygen content is preferably in the range of 1 to 10% in atomic percentage. If it is less than 1%, the effect is hardly seen, and if it exceeds 10%, the R-Fe phase which is the main phase is decomposed by excess oxygen, and the rare earth oxides R ₂ O ₃ and α-Fe or iron oxide Fe-. It separates from O and deteriorates the magnetic characteristics.

The R-Fe alloy is allowed to contain oxygen by the following method. The starting alloy is prepared by melting a rare earth element and iron in a high frequency induction melting furnace or an arc melting furnace under an inert atmosphere, and then casting it in a mold to form an ingot, or cooling it as it is to form an alloy ingot. Then, it is ground with a jaw crusher, a stamp mill, a brown mill, a ball mill, a jet mill, or the like. A predetermined amount of this alloy powder is supplied to an electric furnace, and after evacuation and heating,
A gas containing oxygen is introduced to react the alloy with oxygen gas for a predetermined time. Whether oxygen is taken into the alloy depends on electron beam flaw detection microanalysis (EPMA) and Auger electron spectroscopy analysis (AE
This can be easily determined by oxygen analysis of the cross section of the alloy powder particles by S) or the like.

However, it has been found that even if oxygen penetrates all regions in the alloy particles, it cannot be said that the magnetic properties of the alloy are fully utilized. It has been found by the present inventors that when oxygen penetrates into the entire particles, magnetic properties, particularly crystalline magnetic anisotropy, are deteriorated and performance is deteriorated.
In order to solve this problem, the alloy powder described above is treated at a high temperature on the verge of decomposing into rare earth oxides and iron oxides, and for a short time, so that the oxygen-rich phase inside each particle becomes By realizing a two-phase hybrid state with a phase not containing oxygen, the saturation magnetic flux density could be increased without lowering the coercive force. From the above, it is not necessary to completely react the particles with oxygen, and there is an advantage that the processing time can be shortened. The obtained alloy powder can suppress activation of the surface of the alloy powder by treatment in an oxygen-containing gas, and is stable without further oxidation even when treated in the atmosphere. Therefore, it was possible to obtain a highly corrosion resistant powder which does not require conventional large-scale equipment for suppressing the invasion of oxygen and is easy to handle.

The R-Fe alloy powder obtained by the present invention is
It is suitable as a powder for bonded permanent magnets because its magnetic properties, especially the saturation magnetic flux density are improved. The bonded permanent magnet may be manufactured by a known manufacturing method. For example, the alloy powder obtained by the oxidation treatment of the present invention is pulverized in a nitrogen gas atmosphere with a jet mill to an average particle size of about 3 μm, and the obtained fine powder is obtained. Is mixed with a binder at a weight ratio of 97: 3, and is molded with a pressing die at a pressing pressure of 10 ton / cm ^{2 in} a magnetic field of 15 kOe, and then heat-cured at 100 ° C. for 1 hour. As the binder, a thermosetting resin such as an epoxy resin or a phenol resin, a thermoplastic resin such as a nylon resin, or a metal such as Zn, Sn, or Pb can be used. If the amount of these binders added is less than 2% by weight, the binding strength will be insufficient, and if it exceeds 20% by weight, the magnetic properties, especially the saturation magnetic flux density will be deteriorated. In the case of a resin binder, in addition to the above press molding, injection molding and extrusion molding methods can be used.
If these moldings are carried out while heating, the heat treatment or curing step after molding can be omitted.

[0014]

EXAMPLES The embodiments of the present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. (Examples 1 to 4 and Comparative Examples 1 to 3) Using Sm having a purity of 99.9% and electrolytic iron having a purity of 99.9%, Sm 11.0% and F in atomic percentage were obtained.
e 89.0% was compounded to a composition ratio, and a raw material alloy was produced in a high frequency induction melting furnace in an argon atmosphere. The obtained alloy lump is 11
The mixture was homogenized at 00 ° C for 12 hours. Observation of the internal metallographic structure of this alloy lump with an electron microscope revealed that it had a single phase. This alloy block was crushed in a nitrogen atmosphere using a jaw crusher and a brown mill to obtain a coarse powder having an average particle size of about 30 μm. In order to contain oxygen in this powder, an oxidation treatment was performed under the conditions shown in Table 1 using a gas in which 10% by volume of oxygen was mixed with argon gas. The magnetic properties and the amount of oxygen contained are shown in Table 1. The oxygen contents are shown as weight percentages by measuring the alloy powder by an infrared absorption method. For example, the contents of 0.049 and 2.950 wt% are 0.222 and 5.14 atom% when expressed as atomic percentages, respectively.
Also, when observing the cross section of the particle with EPMA, the contrast of the backscattered electron image is darker in the peripheral part of the particle than in the center, and elemental analysis shows that oxygen is not contained near the center but a large amount in the peripheral part. Oxygen was detected. As Comparative Examples 1 to 3, treatment was carried out under the oxidizing conditions shown in Table 1 except that R-Fe alloys having the same compositions as those in Examples 1 to 4 were used, and the results are shown in Table 1.

[0015]

[Table 1]

(Examples 5-8, Comparative Examples 4-6) Purity 99.9
% Nd, 99.9% pure electrolytic iron and 99.9% pure Ti, atomic percentage of Nd 8.0%, Fe 84.3%, Ti 7.7%
A raw material alloy was prepared in a high frequency induction melting furnace in an argon atmosphere. The obtained alloy ingot is heated at 1100 ° C for 12
Homogenization treatment was performed. Observation of the internal metallographic structure of the alloy block with an electron microscope revealed that it had a single phase. This alloy block was crushed in a nitrogen atmosphere using a jaw crusher and a brown mill, and the average particle size was about 40 μm.
The crude powder of was obtained. In order to contain oxygen in this powder, an oxidation treatment was carried out under the conditions shown in Table 2 using a gas in which argon was mixed with 10% by volume of oxygen. The magnetic properties and the amount of oxygen contained are shown in Table 2. The oxygen content is measured by infrared absorption method of the alloy powder and is shown as a weight percentage. For example, the contents of 0.056 and 2.170 wt% are 0.217 and 7.85 atom%, respectively. Also,
When the cross section of the particle was observed with EPMA, the contrast of the backscattered electron image was darker in the peripheral part of the particle than in the center, and elemental analysis showed that oxygen was not contained near the center, but a large amount of oxygen was detected in the peripheral part. Was done. As Comparative Examples 4 to 6, Examples 5 to 8 were treated under the oxidizing conditions shown in Table 2 except that R-Fe alloys having the same composition were used, and the results are shown in Table 2.

[0017]

[Table 2]

Example 9 and Comparative Example 7 Bond permanent magnets were produced using the alloy powders of Example 4 and Comparative Example 1 above. Each alloy powder was pulverized in a nitrogen gas atmosphere with a jet mill to an average particle size of about 3 μm. The fine powder thus obtained was kneaded with an epoxy resin in a weight ratio of 97: 3, and molded with a pressing die at a pressing pressure of 10 ton / cm ² and a magnetic field of 15 kOe,
Then, it was heat-cured at 100 ° C. for 1 hour. As a result of measuring the magnetic characteristics of the obtained bonded magnet with a vibrating sample magnetometer, a coercive force of 6.0 kOe and a maximum energy product of 18.5 MGOe were obtained when the powder of Example 4 was used. When the powder of Comparative Example 1 was used, the coercive force was 0.4 kOe and the maximum energy product was 2.2 MGOe.

[0019]

INDUSTRIAL APPLICABILITY According to the present invention, the magnetic properties of the rare earth-iron-based permanent magnet alloy powder, particularly the saturation magnetic flux density are improved, which makes it extremely useful in practice as a magnetic alloy. It is highly valuable as an alloy powder, and it is possible to provide a bonded permanent magnet having a high magnetic property obtained by molding the powder, and its utility value in industry is extremely high.

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Claims (2)

[Claims] 1. In a rare earth-iron-based permanent magnet alloy powder comprising a rare earth element-iron-oxygen-added element, the internal structure of each particle of the rare earth-iron-based permanent magnet alloy powder represented by the following general formula is oxygen. A rare earth-iron-based permanent magnet alloy powder, characterized by comprising a two-phase hybrid state of a rich phase and a phase not containing oxygen. R _d (Fe _1-g Co _g ) _100-def O _e M _f (where R is one or more rare earth elements selected from all lanthanoid elements including Y, M is Ti, V,
1 or 2 or more of Si and Mo, 4≤d≤20, 1
≤ e ≤ 10, O ≤ f ≤ 10 atomic%, O ≤ g ≤ 1 atomic ratio. ) 2. A bond permanent magnet obtained by finely pulverizing the rare earth-iron-based permanent magnet alloy powder according to claim 1, kneading with a binder, and molding.