JPS63128606A - Permanent magnet - Google Patents

Abstract

PURPOSE:To improve temperature characteristics, oxidation-resistant properties and magnet characteristic of a rare-earth-ferrous composition permanent magnet by a method wherein the composition is expressed by R-Fe-B-F (wherein R denotes at least one of rare-earth elements including Y) and the ratios of the components are specified. CONSTITUTION:The permanent magnet of the present invention is made of material whose composition is expressed by a general formula RalphaFe(100-alpha-beta-gamma) BbetaFgamma (wherein R denotes at least one of rare-earth elements including Y) and alpha, beta and gamma are within the ranges of atomic percentages of 10<=alpha<=30, 3<=beta<=15 and 0.1<=gamma<=10 respectively and further 4<=beta+gamma<=20. The atomic percentage of R must be 10-30 %. If the percentage is less than 10 %, the coerocive force is reduced and, if the percentage is above 30 %, the flux density is degraded and the energy product is reduced. As R, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu are included and at least one of them must be contained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a permanent magnet having a rare earth-iron composition.

[Prior Art] Recently developed Nd-Fe-B rare earth permanent magnets (e.g., Japanese Patent Laid-Open No. 59-46008) have the ability to obtain unprecedented high magnetic properties and are superior to 3m-Go permanent magnets. In comparison, it is a very useful material because it is low-cost and can use materials such as Fe and Nd, which are rich in resources and inexpensive.

However, this material has drawbacks such as a low Curie point and poor temperature characteristics, low oxidation resistance, and deterioration of magnetic properties if left in air for a long time.

Fe in Nd-Fe-B alloy to improve temperature characteristics.
A method of substituting a part of
No. 2104), the Curie point increases by adding Go, but there is a problem in that the coercive force decreases as the amount added increases.

A method of substituting a portion of Nd with a heavy/rare earth element has also been proposed, but there is a problem in that the residual magnetic flux density decreases even though the temperature characteristics are improved.

Regarding oxidation resistance, a method has been proposed in which a thin film is formed on the surface of a sintered permanent magnet to prevent the penetration of moisture by resin coating, special plating, or vapor deposition (for example, Japanese Patent Application Laid-open No. 60-54406, 60). -63901
However, it is difficult to implement on objects with complicated shapes and has the problem of high cost.

[Problems to be solved by the invention] The present invention has been made in consideration of the above points.
The present invention provides a permanent magnet which has a Curie point higher than that of a d-Fe-B magnet, has excellent temperature characteristics, has improved oxidation resistance, and has excellent magnetic properties such as energy product.

[Means for Solving the Problem] As a result of intensive research to solve the above-mentioned problems, the present inventors found that when boron and fluorine coexist in a permanent magnet with a rare earth-iron composition, the temperature characteristics and acid resistance improve. The present inventors have discovered that the magnetization properties and magnetic properties are improved, and have completed the present invention.

That is, the permanent magnet of the present invention has the general formula % (R is at least one kind of rare earth element including Y), α, β
The permanent magnet has a composition in which the ranges of and γ are 10≦α≦30, 3≦β≦15, 0.1≦γ, ≦10, and 4≦β+γ≦20, respectively, in atomic percentage.

Hereinafter, the permanent magnet of the present invention will be explained in detail.

In the present invention, R needs to be 10 to 30% in atomic percentage. If it is less than 10%, the coercive force becomes small, and if it exceeds 30%, the magnetic flux density decreases and the energy product becomes small. R is Y, La, C
e.

PrSNd15m, Eu, Gd, Tb, DV.

HOlEr, Tm, "y'b and lu are male,
It is sufficient to contain at least one of these.

Moreover, a mixture of two or more types of metal, didium, etc. can also be used.

The boron content is required to be 3 to 15% in terms of atomic percentage. If it is less than 3%, the coercive force is small and the curri is too low, so it is not practical.

If it exceeds 15%, the magnetic flux density will be low and only a small energy product can be obtained.

Fluorine needs to be 0.1 to 10% in atomic percentage. If the fluorine content is less than 0.1%, the demagnetization rate and oxidation resistance due to a Curie temperature rise will not be improved, and the energy product will not improve, and if it exceeds 10%, the magnetic flux density will be low and only a small energy product can be obtained. Can not.

The method of introducing fluorine into the R-Fe-B alloy is to use at least one kind of rare earth fluoride (RF3, R is the same element as above).
This can be done by adding to the Nd-Fe-B alloy.

Further, in the present invention, it is also necessary that the atomic percentage of (boron + fluorine) be 4 to 20%. If it is less than 4%, the coercive force is small and the Curie point and oxidation resistance are not improved. If it exceeds 20%, the magnetic flux density will be low and only a small energy product can be obtained.

The most important point in the present invention is that it contains fluorine, and the R-Fe-B based intermetallic compound contains RF3.
Fluorine can be introduced by sintering after adding. Although the behavior of RFI in intermetallic compounds is not clear, one possible role is as follows. In other words, the coercive force of R-Fe-B-based intermetallic compounds is thought to be determined mainly by the ease with which reverse magnetic domains nucleate.If there are many defects at grain boundaries, the coercive force becomes a source of reverse magnetic domains, and the coercive force is low. Become. It is thought that RF3 acts as a sintering aid during sintering and acts to reduce defects at grain boundaries.

The present invention uses R-Fe-B-1 as the basic component, but Fe
Part of C01Ni, A waist Ti, cr, vn, cu, z
n, zr, Nb.

Mo, Ru, Rh, Pd, Hf, Ta5W, Re, QS
, lr, etc. can also be substituted.

The amount of these additives is about 15% of Fe, and if the amount is more than this, the magnetic flux density becomes small and only a low energy product can be obtained. Further, in addition to the above-mentioned metal elements, oxygen may be present in an amount of 3% or less in atomic percentage.

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

First, an alloy having a composition of 15% Nd, 77% Fe, and 88% Fe is produced in atomic percentage. Next, the alloy is pulverized using a pulverizing means such as a ball mill. In order to obtain good magnetic properties after sintering, the particle size is preferably 10 μm or less. If the particle size is 10 μm or more, the coercive force becomes small. The pulverized alloy and a predetermined amount of rare earth fluoride are mixed using a suitable mixing device to form a raw material powder. In this case, the average particle size of the rare earth fluoride is preferably 10 μm or less; if it is 10 μm or more, it is difficult to mix uniformly and the coercive force cannot be improved.

Next, the raw material powder is molded into a desired shape while being oriented by applying a magnetic field of 15 KOe.

Sintering is carried out at 1000 ml in an inert gas atmosphere such as Ar.
~1200°C for 0.5~3 hours, followed by 500~i
Aging treatment is performed at ooo°C for 1 to 20 hours.

In this way, a permanent magnet with excellent magnetic properties can be obtained.

[Example] Hereinafter, the present invention will be roughly explained in detail using examples.

Examples 1 to 9 Atomic percentages of neodymium (Nd) 15%, iron (Fe>7
Each metal element was blended to give 7% boron (B) and 8% boron (B), and arc melting was performed in a water-cooled steel boat under an Ar atmosphere. The obtained alloy was coarsely ground in a N2 atmosphere, and then finely ground to a grain size of 5 μm or less using a rough ball mill. .

Various rare earth fluorides (RF3) with an average particle size of 5μ or less are added to the fine powder so that the atomic percentage of fluorine (F) in the permanent magnet after sintering is 3%, and mixed in an N2 atmosphere. It was made into raw material powder.

The raw material powder was placed in a mold and compression molded at a pressure of 2 kg/cm 2 while applying a magnetic field of 15) (Qe).The obtained molded body was sintered in an Ar atmosphere at 100°C for 1 hour, and then heated to room temperature. It was then rapidly cooled to 850°C in an Ar atmosphere for 1
After aging at 650℃ for 2 hours,
It was rapidly cooled to room temperature.

The composition of the permanent magnet obtained here is Nd1 in atomic percentage.
4.4R1, OF"73.9B7.7 F3.0.

Residual magnetic flux density (Br) and coercive force IH of the obtained permanent magnet
c), maximum energy product [(BH)I11ax], Curie temperature (TC>), and temperature coefficient of magnetic flux density were measured. Oxidation resistance was also evaluated.

Comparative Example 1 Sintering and aging treatment were performed under the same conditions as in Example 1 except that rare earth fluoride was not added to the raw material powder.

Table 1 shows the magnetic properties, oxidation resistance, etc. of the permanent magnets obtained in the above Examples and Comparative Example 1.

However, among the descriptions in Table 1, temperature coefficient of 3r = rate of decrease at 20 to 140°C, oxidation resistance = rate of decrease in Br after standing for 1000 hours at 80°C x 90% RH.

Table 1 Examples 10 to 12 Sintered in the same manner as in Example 1 except that terbium fluoride was added to the raw material powder so that the atomic percentage of fluorine in the alloy was 0.3.6.9%. , subjected to aging treatment. Table 2 shows the magnetic properties of the obtained permanent magnet.

Comparative Example 2 Sintering and aging were performed in the same manner as in Example 1 except that terbium fluoride was added to the raw material powder so that the atomic percentage of fluorine in the alloy was 15%. Table 2 shows the magnetic properties of the permanent magnets.

Table 2 Examples 13 to 15 Permanent magnets having the alloy compositions shown in Table 3 were prepared using praseodymium fluoride as the rare earth fluoride and using the same method as in Example 1. The magnetic properties are shown in Table 3.

'X43 Table Examples 16 to 18 Permanent magnets having the alloy compositions shown in Table 4 were prepared using dysprosium fluoride as the rare earth fluoride and using the same method as in Example 1. The magnetic properties are shown in Table 4.

Table 4 [Example 21 Atomic percentage: 15% neodymium, 70% iron, 7% cobalt
%, and each metal element was blended so that the boron content was 8%, and then finely pulverized in the same manner as in Example 1. The atomic percentage of fluorine in the permanent magnet after sintering is 3% in the fine powder.
Terbium fluoride was added to give a permanent magnet, and sintering and aging were performed in the same manner as in Example 1 to obtain a permanent magnet.

As for the magnetic properties, (BH) max was 39.6 MGOe, the Curie temperature was 340°C, the temperature coefficient of Br was -0.05, and the oxidation resistance was 0.6%.

Effects of the Invention] As explained above, the permanent magnet of the present invention has a higher energy product than conventional permanent magnets, has a small demagnetization rate due to temperature rise, and has excellent oxidation resistance, so it is suitable for practical use. It's extremely useful.

Claims (1)

[Claims] General formula R_αFe_(_1_0_0_-_α_-_β_
-_γ_) B_β・F_γ (where R is at least one rare earth element including Y), where α, β and γ are each in atomic percentage, 10≦α≦30 3≦β≦15 0.1≦γ≦ 10 and 4≦β+γ≦20.