JPH0752685B2 - Corrosion resistant permanent magnet - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a Fe—B—R rare earth permanent magnet having high magnet characteristics, and a rare earth having a significantly improved corrosion resistance of the permanent magnet due to its specific composition and simple surface treatment. ·boron·
The present invention relates to iron-based permanent magnets.

BACKGROUND ART The applicant has previously used a light rare earth, which is rich in resources, mainly N2d and pr, as a main component of B and Fe, and does not contain expensive Sm or Co. Fe-BR type permanent magnets have been proposed as new high-performance permanent magnets that greatly exceed the characteristics (Japanese Patent Laid-Open Nos. 59-46008 and 59-894).
No. 01 bulletin).

The Curie point of the magnet alloy is generally 300 ° C. to 370 ° C., but by substituting a part of Fe with Co, an Fe—BR system permanent magnet having a higher Curie point is obtained. Kakai 59-64733, JP-A-59-132104), and C
O-containing Fe-BR rare earth permanent magnets have Curie points equal to or higher than those and higher (BH) max. In order to improve their temperature characteristics, especially iHc, Nd and Pr are used as rare earth elements (R). Fe-B- mainly containing light rare earths such as Co
By including at least one of heavy rare earths such as dy and Tb in a part of R of the R rare earth permanent magnet, iHc was further improved while maintaining an extremely high (BH) max of 25MGOe or more. A Fe-BR rare earth permanent magnet containing Co was proposed (JP-A-60-34005).

However, Fe-B having the above-mentioned excellent magnetic properties
A permanent magnet made of an R-type magnetic anisotropic sintered body contains iron as a main component, which is a rare earth element and iron that easily oxidize in air to form a stable oxide. The oxides generated on the surface of the magnet cause a decrease in the output of the magnetic circuit and a variation between the magnetic circuits, and there is a problem that the peripheral devices are contaminated due to the dropping of the surface oxide.

Therefore, in order to improve the corrosion resistance of the above Fe-BR permanent magnet, the applicant has proposed a permanent magnet whose surface is coated with a corrosion-resistant metal plating layer by electroless plating or electrolytic plating (Japanese Patent Application No. However, since the permanent magnet body is a sintered body and is porous in this plating method, the acidic solution or alkaline solution in the plating pretreatment remains in this hole.
There is a risk of corrosion over time, and since the magnet body has poor chemical resistance, the magnet surface is corroded during plating, resulting in poor adhesion and corrosion resistance. Therefore, we proposed a permanent magnet with a corrosion-resistant resin layer coated on the surface of the magnet body by a spray method or a dipping method (Japanese Patent Application No. 58-171907). There was a problem that it could not be used for a long time.

The object of the present invention is to improve the corrosion resistance of the F-B-R permanent magnet material, and to improve the corrosion resistance, a simple surface treatment is applied to the F-B-based F-B excellent in corrosion resistance and dimensional accuracy.
-R system permanent magnet is intended.

Structure and Effect of the Invention The present invention has been conducted as a result of various studies on surface treatments to be applied to the surface of a Fe-BR permanent magnet for the purpose of Fe-BR permanent magnet exhibiting excellent corrosion resistance. By providing a corrosion-resistant resin layer containing a metal flakes of a specific property on the surface of,
We found that the corrosion resistance can be significantly improved,
This invention has been completed.

That is, the present invention provides R (R is at least one of Nd, Pr, Dy, Ho, Tb, or further La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu, Y.
Of at least one of 10% by atom to 30 at%, B2 at% to 28 at% and Fe at 65 at% to 80 at% as the main components, and the main phase of the sintered permanent magnet body is a tetragonal phase. A corrosion-resistant permanent magnet having a corrosion-resistant resin layer containing a thin metal piece having a thickness of 1 μm or less and a width and a length of 2 μm to 200 μm on a surface thereof.

The corrosion-resistant resin layer in the present invention is composed of a metal thin piece and a resin, that is, metal thin pieces having specific properties are laminated in the resin layer to form an excellent corrosion-resistant resin, so that it is only necessary to form a thin film on the permanent magnet body. Has a great anti-corrosion effect.

Preferred Embodiments of the Invention As the metal flakes in the present invention, there are metals and alloys thereof having good corrosion resistance with which flakes can be easily obtained, and examples thereof include stainless steel, Al, Zn, Ti, Zr, V, Nb, Cr, Mo and W. , Mn, C
Metals such as o and Ni and their alloys can be used.

The size of the metal flakes is 1 μm or less in thickness, 2 to 200 μm in width and length, and 0.5 μm in thickness.
Hereinafter, the width and length of 5 to 100 μm are preferable for forming a uniform resin layer.

Further, as the resin in the present invention, an epoxy resin,
It is a synthetic resin for paints such as thermosetting acrylic resin, phenol resin, urethane resin, melamine resin, silicone resin, vinyl resin, or a composite resin thereof.

The amount of metal flakes contained in the resin is 0.01 PHR to 60 PHR, preferably 1 PHR to, from the viewpoint of corrosion resistance and formation of a uniform resin layer.
30PHR, and further, a rust preventive pigment such as zinc oxide, zinc chromate, or lead may be contained in the above resin, or benzotriazole may be contained.

Further, in the present invention, as a method of coating the resin layer on the surface of the permanent magnet body, it is applied by a spray method, a brush coating method, a dipping method or the like and then baked. This resin layer needs to be 5 μm, and 25 μm to obtain excellent dimensional accuracy.
The thickness is preferably m or less.

Reasons for Limiting Components of Permanent Magnet The rare earth element R used in the permanent magnet of the present invention has a composition of 10
It occupies at least 30 atomic%, but at least one of Nd, Pr, Dy, Ho and Tb, or further La, Ce, Sm, Gd,
Those containing at least one of Er, Eu, Tm, Yb, Lu and Y are preferable.

Also, one type of R is usually sufficient, but it is practically 2
Mixtures of more than one species (Misch metal, didymium, etc.) can be used for reasons of availability.

It should be noted that this R does not have to be a pure rare earth element, and may contain an impurity that is unavoidable in manufacturing within the industrially available range.

R is an essential element in the above-mentioned permanent magnet,
If it is less than 30% by atom, the crystal structure will be a cubic structure having the same structure as α-iron, so that high magnetic properties, particularly high coercive force, cannot be obtained. However, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics cannot be obtained. Therefore, the rare earth element is 10 atomic%
The range is up to 30 atom%.

B is an essential element in the permanent magnet according to the present invention, and if it is less than 2 atomic%, the rhombohedral structure becomes the main phase and a high coercive force (iHc) cannot be obtained. If it exceeds 28 atoms, B is rich. An excellent permanent magnet cannot be obtained because the amount of nonmagnetic phase increases and the residual magnetic flux density (Br) decreases. Therefore, B
Is in the range of 2 atom% to 28 atom%.

Fe is an essential element in the above-mentioned permanent magnet, and the residual magnetic flux density (Br) decreases if it is less than 65 atomic%, and a high coercive force cannot be obtained if it exceeds 80 atomic%.
The content is up to 80 atom%.

Further, in the permanent magnet of the present invention, substituting a part of Fe with Co can improve the temperature characteristics without deteriorating the magnetic characteristics of the obtained magnet.
If it exceeds 20%, the magnetic characteristics are deteriorated, which is not preferable. The substitution amount of Co is 5 atom% to 15 in the total amount of Fe and Co.
In the case of atomic%, (Br) increases as compared with the case of not substituting, so that it is preferable to obtain a high magnetic flux density.

Further, the permanent magnet of the present invention can tolerate the presence of impurities that are unavoidable in industrial production in addition to R, B and Fe.
Manufacture of a permanent magnet by substituting at least one of C of 0 atomic% or less, P of 3.5 atomic% or less, S of 2.5 atomic% or less, and Cu of 3.5 atomic% or less, and a total amount of 4.0 atomic% or less. It is possible to improve productivity and reduce prices.

Further, at least one of the following additional elements is RB-
It can be added to the Fe-based permanent magnet because it is effective in improving the coercive force and squareness of the demagnetization curve, or in improving the manufacturability and lowering the cost.

9.5 atomic% or less Al, 4.5 atomic% or less Ti, 9.5 atomic% or less V, 8.5 atomic% or less Cr, 8.0 atomic% or less Mn, 5.0 atomic% or less Bi, 9.5 atomic% or less Nb, 9.5 Ta less than atomic%, Mo less than 9.5 atomic%, W less than 9.5 atomic%, Sb less than 2.5 atomic%, Ge less than 7 atomic%, Sn less than 3.5 atomic%, Zr less than 5.5 atomic%, 9.0 atomic % Or less Ni, 9.0 atom% or less Si, 1.1 atom% or less Zn, and 5.5 atom% or less Hf, at least one kind is added, but when two or more kinds are contained, the maximum content is By containing at most atomic% of the additive element having the maximum value,
It is possible to increase the coercive force of the permanent magnet.

The fact that the main phase of the crystal phase is a tetragonal crystal is indispensable for producing a sintered permanent magnet having excellent magnetic properties from a fine and uniform alloy powder.

The permanent magnet of the present invention has an average crystal grain size of 1 to 80 μm.
The compound having a tetragonal crystal structure in the range of 1) as the main phase and containing 1% to 50% by volume of the nonmagnetic phase (excluding the oxide phase) is characterized.

The permanent magnet according to the present invention exhibits a coercive force iHc ≧ 1 kOe and a residual magnetic flux density Br> 4 kG, and a maximum energy product (BH) max shows (BH) max ≧ 10 MGOe,
The maximum value reaches 25MGOe or more.

Further, the main component of R of the permanent magnet according to the present invention is 50
% Of light rare earth metal mainly composed of Nd and Pr, R12 atom% to 20 atom%, B4 atom% to 24 atom%, Fe74
(BH) max35M when the main component is from atomic% to 80 atomic%
It shows excellent magnetic properties over GOe, and its maximum value reaches over 45MGOe especially when the light rare earth metal is Nd.

Further, in the present invention, in a corrosion resistance test of leaving it in an environment of 60 ° C and a relative temperature of 90% for a long time, Nd11at% ~ 15at%, Dy0.2at% ~ 3.0at%, and Nd11at% ~ 15at% as a permanent magnet showing extremely high corrosion resistance. And the total amount of Dy is 12at% ~ 17at%, B5at% ~ 8at%, Co0.5at
% To 13 at%, Al 0.5 at% to 4 at%, C 1000 ppm or less, and the balance Fe and inevitable impurities are preferable.

Example: As starting materials, electrolytic iron with a purity of 99.9%, ferroboron alloy, and ND, Dy, Co, and Al with a purity of 99.7% or more were used, and after mixing these, high-frequency melting was performed and then cast in a water-cooled copper mold.
An ingot having a composition of Nd-0.5Dy-7B-6Co-2Al-remaining Fe (at%) was obtained.

After that, the ingot is coarsely crushed and then finely crushed to obtain an average particle size of 3
A fine powder of μm was obtained.

Insert this fine powder into the mold and orient it in a 12kOe magnet,
It was molded at a pressure of 1.5 t / cm ^{2 in} the direction perpendicular to the magnetic field.

The obtained molded body was sintered at 1100 ° C. for 1 hour in Ar, then allowed to cool, and further subjected to an aging treatment at 580 ° C. for 2 hours in Ar to produce a permanent magnet.

From the obtained permanent magnet, a test piece was cut into a size of length 20 mm × width 10 mm × thickness 8 mm.

Next, after washing this test piece with a solvent and drying it, the average thickness
Epoxy resin with 0.3 μm, average width of 8 μm, and average length of 10 μm dispersed is applied using a sprayer, dried at room temperature for 3 hours, and then baked at 90 ° C for 1 hour to give a surface. A 20 μm to 25 μm resin layer was applied to obtain a permanent magnet of the present invention.

The resin layer contained 18 PHR of stainless steel flakes.

For comparison, an epoxy resin that does not contain stainless steel flakes is applied by spraying, dried at room temperature for 3 hours, then at 90 ° C.
Then, a comparative test piece having a surface coated with a resin layer of 20 μm to 20 μm was prepared.

Next, the above test was left for 1000 hours in an atmosphere of a temperature of 60 ° C. and a relative humidity of 90% to measure the rusting condition and the magnet characteristics before and after the corrosion resistance test of the permanent magnet material. The results are shown in Table 1.

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Claims (1)

[Claims] 1. R (R is at least one of Nd, Pr, Dy, Ho and Tb, or further La, Ce, Sm, Gd, Er, Eu, T
m, Yb, Lu, Y consisting of at least 11 kinds) 10 atom% to 30 atom%, B2 atom% to 28 atom%, Fe65 atom% to 80 atom% as main components, and the main phase from the tetragonal phase Of 1 μm or less in thickness and 2 μm in width and length on the surface of the sintered permanent magnet body
A corrosion-resistant permanent magnet having a corrosion-resistant resin layer containing a corrosion-resistant metal flakes of up to 200 μm.