JPH01111843A - Rare-earth permanent magnet material and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture a rare-earth permanent magnet material improved in workability and working costs and having superior acid resistance by mixing a powdered alloy composed principally of rare-earth elements, Cu, and Fe with a powdered intermetallic compound consisting of rare-earth elements, Fe, and B, compacting the resulting powder mixture in a magnetic field, and then subjecting the green compact to liquid-phase sintering. CONSTITUTION:A powdered alloy composed principally of one or two kinds among the compounds of R(Cu1-xFex) phase and R(Cu1-yFey)2 phase [where the symbols (x) and (y) stand for >=0 and <=0.2, respectively] is mixed with a powdered R2Fe14B intermetallic compound (where R means rare-earth elements including Y), and the resulting powder mixture is compacted in a magnetic field and then subjected to liquid-phase sintering. At this time, the ratio of the factor of shrinkage on sintering in the direction of magnetic orientation to that in a vertical direction based on the factor of shrinkage on sintering of a green compact in the direction of magnetic orientation is regulated to >=80%. By this method, the rate-earth permanent magnet excellent in workability and oxidation resistance can be easily manufactured.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an R-T-B permanent magnet mainly composed of an R2T14B intermetallic compound, and in particular to improvement of workability and processing cost of a sintered body. and a rare earth permanent magnet with excellent oxidation resistance.

[Conventional technology]

R-Fe-B magnets, represented by Nd-Fe-B, have higher magnetic properties than the Sm-Co alloy permanent magnets that have been in widespread use, and are rich in resources.

Because it has Nd-Fe as its main component, its uses are expanding, and its use as a substitute for Sm-Co permanent magnets is progressing.

These rare earth permanent magnets are used depending on their use.

Various shapes are manufactured, and the direction of magnetic field orientation is also various. Among them, there are products in which the magnetic field is oriented in the radial direction of the ring, and there are also products with multipolar radial orientation by pulse magnetization in this radial direction. .

In particular, its uses have been expanding recently.

Currently, Sm-Co permanent magnets are commercially available.

The above-mentioned products with various shapes and radial orientations have been produced without any problems.

[Problem that the invention seeks to solve]

However, when manufacturing Nd-Fe-B based magnets, a major problem is high cost. It is Sm-Co
In the Nd-Fe-B system, the shrinkage rate of the green compact due to sintering is isotropic in all directions, but in the Nd-Fe-B system, the shrinkage rate tends to vary considerably in the direction perpendicular to the magnetic field orientation direction. In general, the contraction rate in the direction perpendicular to the direction of magnetic field orientation relative to the contraction rate in the direction of magnetic field orientation is about 60 inches.

Therefore, when a ring-shaped radially oriented product is sintered using a powder compact, the sintered body has an elliptical shape, and there is a problem that a desired circular product cannot be obtained.

As a countermeasure to this, the block sintered body is cut out, or an oval-shaped sintered body that is larger than the desired size is made in advance and then subjected to centerless processing, which increases the processing cost and generates a large amount of processing waste. I was taking measures to make this happen.

Additionally, taking into account the shrinkage rate during sintering, the shape of the mold is made elliptical in advance to obtain the desired circular sintered body. The shrinkage rate during compaction changes depending on the compacted powder density, etc., so molds with different dimensions must be used to produce compacts with different compacted densities, resulting in high costs. Undesirable.

Moreover, when sintering a radial multipolar molded body, cracks occur in the sintered body due to the difference in shrinkage rate during the sintering process, making it extremely difficult to manufacture. Ta.

Furthermore, this R-Fe-B permanent magnet has another major problem. In other words, since the R-Fe solid solution phase, which is extremely easily oxidized in the atmosphere, exists in the metal structure of the two-piece magnet, when it is incorporated into a device such as a magnetic circuit, the magnet's It has the disadvantage that characteristics deteriorate and vary widely due to oxidation, and that surrounding parts are contaminated by scattering of oxides generated by magnets. As a document related to improving this corrosion resistance, JP-A No. 6
No. 0-54406 (J, P, A) and No. 60-63903
For example, the number etc.

These documents aim to improve the corrosion resistance of a magnet by forming an oxidation-resistant film such as plating or a chemical conversion film on the surface of the magnet.

However, these oxidation-resistant coatings use large amounts of water and aqueous solutions during the process.

Since the Nd-Fe solid solution phase of the magnet is oxidized during the treatment process, oxidation continues inside the magnet even after the film is formed.

Corrosion resistance cannot be improved because blistering or peeling of the film occurs.

In addition, as a method that does not use water, coating with oxidation-resistant resin such as epoxy, sputtering, which has recently become popular,
At, Ni by vapor deposition, ion blating, etc.
There are also methods such as dry plating that improve corrosion resistance by forming a metal film such as. however.

Even in unused coatings, the film may deteriorate due to long-term use, during use, or during product inspection.

If the surface of the magnet comes into contact with the atmosphere due to minute chips etc. during handling such as installation into a device, the Nd-Fe solid solution phase in the magnet structure will be removed from this area.

It is not suitable as a measure to improve corrosion resistance because it oxidizes significantly over time and spreads throughout the inside of the magnet.

As mentioned above, in any of the conventional methods for improving corrosion resistance, there is a Nd-Fe solid solution phase that is extremely easily oxidized in the magnet, so it is extremely difficult to impart the inherent corrosion resistance of each of the above measures to a water-based magnet. It was difficult.

That is, in a two-wire magnet, it is impossible to obtain sufficient corrosion resistance unless the corrosion resistance of this Nd-Fe solid solution phase is fundamentally improved.

In addition, as a countermeasure for this, Nl l Cur is added to the single magnet alloy.
Although it is possible to improve the corrosion resistance of the water-based magnet alloy by adding elements such as Smtpb and to coat the water-based magnet with various corrosion-resistant films that have previously been water-blocked, the above drawbacks can be overcome. In the conventional method, the alloy ingot obtained by adding these elements to the magnetic alloy ingot is crushed, formed, and sintered. This is not suitable as a countermeasure because the elements will diffuse in a negative manner, significantly deteriorating the magnetic properties.

Therefore, the technical problem of the present invention is to solve these two problems, and to create a sintered magnet that can reduce the processing cost compared to the conventional Nd-Fe-B magnet, and a rare earth magnet that has excellent corrosion resistance. Our goal is to provide permanent magnets.

[Means for solving problems]

According to the present invention, RT containing R-Fe-B as a main component
-B-based alloy magnet (where R is a rare earth element including Y, elemental, T
indicates a transition metal. ) by powder metallurgy, R(cut −xTx ) + R(c u , −7
Ty) 2 types or 2 types (here, 0≦x'y≦0
．． 2), R(Cu
T ), R (Cu Ty)″' 1-xx
1-7 2 is two types of compounds, Nd 2F
e A rare earth permanent magnet in which the 14B magnetic phase is wrapped is obtained.

This obtained sintered magnet has a shrinkage rate during sintering in which the ratio of the shrinkage rate in the direction perpendicular to the magnetic field orientation direction to that in the magnetic field orientation direction is 80% or more.
The directionality of the shrinkage rate during sintering is much more relaxed than that of e-B magnets. Therefore, it is possible to fabricate a multipolar molded body with radial orientation and radial shape using the mold used for the normal Sm-Co system, and then sinter the compact in the same way as a normal Nd-Fe4 magnet. .

The deformation of the sintered body is significantly improved, and cracks in the sintered body do not occur due to the difference in shrinkage rate during sintering, so compared to the conventional Nd-F
Compared to e-B type magnets, the processing cost is improved, and it is also possible to manufacture products with multipole orientation in the radial direction, which was previously considered difficult to manufacture.

In addition, in water-based magnets, R(c'', -xpex)-R(
Since one or two of Cu1-yFey)2 is used instead, the oxidation resistance of the sintered body is significantly improved.

Therefore, 2. Usual oxidation-resistant medaki such as Ni and Cr, resin c
It is possible to impart the inherent corrosion resistance of oatiltg and the like to aqueous magnets, which is extremely useful industrially. Here, in the rare earth permanent magnet in the present invention, R(Cu1-xFex) and R(Cu1
-yFe,) in one or two of the two phases, 0≦x, y
≦0.2 because if it is 0.2 or more, other phases will be formed instead of the R(CuFe) and R(CuFe) two phases that are the object of the present invention, and excessive Fe will not be present in the sintered body. 0≦Xs7 to remain in the Fe phase and significantly deteriorate the magnetic properties.
It is necessary to satisfy ≦0.2.

In addition, for a 9-piece magnet, the ratio of the contraction rate in the direction perpendicular to the magnetic field orientation direction to the contraction rate in the magnetic field orientation direction during sintering of the compact is 80% or more, which is smaller than 80%. This is because, in this region, the deformation of the sintered body is significant, making it impossible to reduce processing costs, and cracking of the sintered body occurs due to the difference in shrinkage rate, which is not in accordance with the object of the present invention.

〔Example〕

Hereinafter, two embodiments of the present invention will be described with reference to the drawings.

<Example-1> Using Nd-Fe-B with a purity of 95% or more, 28 Nd.1. OB
-Nd2Fe14 with a composition of Febat (wt%)
An ingot containing phase B as the main phase was obtained. This ingot was coarsely ground, and the resulting coarse powder was used as material I.

Next, using Nd-Fe-Cu-B equivalent to the above, 61.3Nd・37.7Cu・1. OB, 61
．． 5Nd-35,7Cu ・1.7 Fe” 1.O
B.

61.6Nd ・34. ICu ・3.3Fe ・1.
OB, 61.8Nd・32.2Cu・5. OF
e・1. OB, 61.9Nd・30.4Cu
・6.7Fe ・1, OB, 62Nd ・28.6
Cu ・8.4Fe-1, OB (both wt4,
The Fe/Cu ratios are O/1 and 0.0510.
95.

0.110.9, 0.1510.85, 01210
．． Six types of coarse powders (■ materials) having a composition of 0.8, 0.2510.75) were obtained.

The weight is 85 wt% for I material and 15 wt% for the remainder.
Six types of coarse powder were obtained by mixing and weighing six types of materials.

Next, each of these coarse powders was wet-milled using a ball mill with an average particle size of about 4 μm to obtain fine powders. Next, the obtained fine powder was heated in a magnetic field of 20 KOe for 1. Ot on/cr
It was molded using n2 to obtain a green compact. 1000 of these compacts
Sintered at ˜1150° C. in 0˜4 hrAr. The obtained sintered body was heated at 500 to 900°C for 1 to 5 hours, and then rapidly cooled.

Figure 1 shows the highest magnetic properties among these sintered bodies. From FIG. 1, it can be seen that when the Fe/Cu ratio of the Nd-Cu-Fe-B powder of material (2) is between 071 and 0210.8, high magnetic properties are exhibited.

<Example-2> Among the ■materials obtained in Example-1 and the ■materials obtained in Example-1, 61.3Nd・37.7Cu・1. OB
15 wt % of powder having the composition was added and mixed.

This powder was treated in the same manner as in Example-1 to obtain a fine powder.

Next, this fine powder was placed in a magnetic field of 15 KOe to obtain a cylindrical molded body of φ20×10 so as to have radial orientation.

Further, the same powder was magnetized to 100 KOe to obtain a 6-pole radial multipolar molded body having dimensions of φ20×φ12×10.

Next, 32Nd4.0B-F, which is a comparative material of Example-1.
Using a fine powder having the composition of ebat, a molded body having a radial orientation having the same dimensions as above and a molded body having a six-pole multipolar radial orientation were obtained.

These compacts were then sintered in Ar at 1100° C. for 2 hours.

These sintered bodies were subjected to measurement of their shrinkage rate and observation of their appearance.

The results are shown in Table 1.

As shown in Table 1 below, the magnet sintered body according to the present invention has a small difference in shrinkage rate between the orientation direction and the perpendicular direction, and the deformation of the sintered body is also small. In addition, in the comparative example, cracks occurred in the sintered body of the multipolar radially oriented product.

The sintered magnet according to the present invention does not suffer from cracking in two.

The deformation of the sintered body was also small.

In other words, the permanent magnet according to the present invention has a small machining allowance, so the machining cost can be reduced, and moreover, the permanent magnet according to the present invention can reduce the machining cost.
It can be seen that it is extremely easy to manufacture multipolar radially oriented products, which were considered difficult to manufacture with magnets based on magnets.

<Example 3> The sintered body obtained in Example 1 was subjected to electrolytic Ni plating with CuT base plating and colored chromate treatment. Further, as a comparative example, 32Nd・1. In OB: An ingot having the composition of Tebat was obtained by high frequency melting in the same manner as in Example-1.

Next, as in Example-1, coarse pulverization, fine pulverization and molding in a magnetic field,
A sintered body was obtained by sintering and heat treatment. This sintered body was then subjected to the same surface treatment as above.

It was used as a comparison material. When the film thickness of these surface treatments was measured, it was 2 to 25 μm.

Each of these test pieces was subjected to a constant temperature and humidity test at 60°C x 90% for 3 times.
Added 00 hr.

The results are shown in Table 2.

Table 2 ◎... No change ○... Slight red rust on edges etc. Δ... Spotted white oxide or red rust on the surface ×...
The magnet of the present invention has red rust and white oxide on the entire surface and the margin below the peeling of the film.9 From Table 2, the magnet of the present invention is
It can be seen that the corrosion resistance is significantly superior to that of −'− type magnets.

〔Effect of the invention〕

As explained above, Nd(Cu, -xFeρ or Nd(C
A sintered body manufactured by a conventional powder metallurgy method by heating a powder whose main phase is one or more of the following phases: u1-yFey)2 (O≦x, y≦0.2) The magnet is +Nd (C
u 1-xFe x ), or Nd(Cu1-yFe
y) It has a structure in which a K t Nd2Fe14B phase is dispersed in a matrix of one or more of the two phases.

This sintered magnet not only has excellent magnetic properties, but also has a significantly smaller shrinkage rate during sintering than conventional Nd-Fe-B magnets. Therefore, the deformation due to the difference in shrinkage rate of radially oriented products can be reduced, the processing margin can be reduced, and processing costs can be reduced. In addition, it is easy to manufacture polycavity-type radially oriented products using water-based magnets, which were considered difficult to manufacture using conventional Nd-Fe-B. In addition, water-based magnets are different from conventional Nd-
Since corrosion resistance is significantly improved compared to Fe-B magnets, oxidation-resistant plating such as Ni, chemical conversion coating, oxidation-resistant resin c
It becomes possible to provide the inherent corrosion resistance of O+Lting and the like.

Although only the Nd-Fe4 system has been described above, it can be easily inferred that similar effects can be expected for rare earth element (R)/Fe-B system alloys including Y.

[Brief explanation of the drawing]

FIG. 1 shows Nd(Cu1-
The graph shows the relationship between the amount of Fe substitution in a sintered body obtained by mixing powders of xFex)B (x=0 to 0.25) and magnetic properties. Figure 1 hem, ratio + rnol)

Claims (1)

[Claims] 1) R_2Fe_1_4B intermetallic compound (where R is
R・Fe・Cu・
In B-based permanent magnets, Nd(Cu_1_-_xFe_
x), Nd(Cu_1_-_yFe_y)_2, wherein the R_2Fe_1_4B phase is dispersed in a matrix mainly composed of one or two compounds (where 0≦x, y≦0.2). Rare earth permanent magnet. 2) In the rare earth permanent magnet according to claim 1, the ratio of the sintering shrinkage rate in the magnetic field orientation direction and the perpendicular direction to the sintering shrinkage rate in the magnetic field orientation direction of the powder compact is 80% or more. A rare earth permanent magnet material characterized by: 3) R_2Fe_1_4B intermetallic compound powder (here R
indicates a rare earth element containing Y) and R (Cu_1_-_x
Fe_x), one or two compounds of R(Cu_1_-_yFe_y)_2 phase (where 0≦x, y≦0.2)
A rare earth permanent magnetic material characterized by comprising a mixing step of mixing alloy powders mainly composed of to form a mixed powder, and a sintering step of forming the mixed powder in a magnetic field and sintering it in a liquid phase. manufacturing method.