JP3383338B2 - Corrosion-resistant permanent magnet and its manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Fe-B-Ra-based permanent magnet having high magnetic properties and excellent corrosion resistance,
By providing a corrosion-resistant resin layer by electrodeposition coating on the surface of the magnet through a tin oxide film, corrosion resistance, especially deterioration from the initial magnet characteristics when left in an atmosphere of 80 ° C and 90% relative humidity for a long time, is extremely low. Fe-B having stable magnet characteristics
-Ra type permanent magnet and its manufacturing method.

[0002]

2. Description of the Related Art First, a light rare earth which is rich in resources centering on Nd and Pr is used as a main component of B and Fe, and does not contain expensive Sm or Co. As a new high-performance permanent magnet that greatly exceeds the characteristics, F
An e-B-Ra type permanent magnet has been proposed (Japanese Patent Laid-Open No. 59-59).
-46008, JP-A-59-89401).

The Curie point of the magnet alloy is generally 30.
It is 0 ° C to 370 ° C, but Fe-B- having a higher Curie point by substituting a part of Fe with Co.
Ra-based permanent magnet (JP-A-59-64733, JP-A-5-64733)
9-132104), and further has a Curie point equal to or higher than that of the Fe-B-Ra-based rare earth permanent magnet containing Co and a higher (BH) max, and improves its temperature characteristics, particularly iHc. In order to make the rare earth element (R
As a), a part of Ra of Co-containing Fe-B-Ra-based rare earth permanent magnets centering on light rare earths such as Nd and Pr is used as D.
By containing at least one of heavy rare earth elements such as y and Tb, extremely high (BH) m of 25 MGOe or more.
Co that has further improved iHc while holding ax
A Fe-B-Ra-based rare earth permanent magnet containing is proposed (Japanese Patent Laid-Open No. 60-34005).

However, the permanent magnet made of the Fe--B--Ra type magnetic anisotropic sintered body having the above-mentioned excellent magnetic characteristics contains iron as a main component, which is a rare earth element which is easily oxidized in air, and iron. When incorporated into a magnetic circuit, the oxide generated on the surface of the magnet causes a decrease in the output of the magnetic circuit and variations among the magnetic circuits, and there is a problem of contamination of peripheral equipment due to the loss of the surface oxide. It was

[0005]

Therefore, the above Fe-
In order to improve the corrosion resistance of B-Ra type permanent magnets, a permanent magnet (JP-A-61-130453) in which the surface of the magnet body is coated with a corrosion-resistant resin layer by electrodeposition coating has been proposed. Since the body is a sintered body and has porosity, there is a problem that the electrodeposition liquid does not sufficiently penetrate into the pores and may corrode with aging, resulting in poor adhesion and corrosion resistance.

The present invention has excellent adhesion to an Fe-B-Ra type permanent magnet base, prevents elution of the magnet surface, and improves its corrosion resistance. Particularly, the temperature is 80 ° C. and the relative humidity is 9
It is an object of the present invention to provide a Fe-B-Ra-based permanent magnet having stable high magnet characteristics and minimizing the deterioration from the initial magnet characteristics when left for a long time under 0% atmosphere condition, and a method for manufacturing the same.

[0007]

The present invention has excellent corrosion resistance, and in particular, even when left for a long time under an atmospheric condition of a temperature of 80 ° C. and a relative humidity of 90%, the adhesion to the base is excellent and the elution of the magnet surface is achieved. Fe-B with stable magnet characteristics
As a result of various studies on the surface treatment of permanent magnets for the purpose of -Ra-based permanent magnets, a tin oxide film was formed on the surface of Fe-B-Ra based magnets with specific components by a thermal decomposition method using a tin alkoxide compound solution. And excellent corrosion resistance by applying a corrosion resistant resin layer by electrodeposition coating.
Excellent adhesion between the Fe-B-Ra magnet surface, extremely stable magnetic characteristics to grade corrosion is found that the resulting low cost, and completed the present invention.

That is, according to the present invention, 100 C is added to the surface of the Fe-B-Ra type permanent magnet body whose main phase is a tetragonal phase.
It is a corrosion-resistant permanent magnet having a corrosion-resistant resin layer formed by electrodeposition coating through a tin oxide film having a film thickness of 500 Å or less containing ppm to 1000 ppm.

Further, according to the present invention, after the surface of the Fe-B-Ra type permanent magnet body whose main phase is a tetragonal phase is cleaned, the magnet body is immersed in a tin alkoxide compound solution or the magnet surface is applied. After applying the tin alkoxide compound solution, a tin oxide film layer containing 100 ppm to 1000 ppm of C is formed by a heat treatment of holding at 200 ° C. to 450 ° C. for 30 minutes to 10 hours, and further, the magnet body is dipped in a resin solution. Electrodeposition coating treatment to form a corrosion-resistant resin layer on the surface of the magnet body, which is a method for producing a corrosion-resistant permanent magnet.

In the present invention, the tin oxide coating layer on the surface of the magnet is a tin alkoxide compound solution (general formula Sn).
(OR) n, R: alkyl group or alkyl group + other functional group, n: oxidation number) The surface of the magnet body dipped or sprayed is dried and then heat-treated at 200 ° C to 450 ° C for 30 minutes to 10 hours to form a film. Therefore, the thickness of the tin oxide film is preferably 500 Å or less. If the tin oxide film thickness exceeds 500Å, the adhesion strength of the film is reduced, and the corrosion-resistant resin layer adhered to the surface of the tin oxide film may peel off. Therefore, the thickness is set to 500Å or less. Further, in the tin oxide film of the present invention, C of 100 p
It is characterized by containing pm to 1000 ppm, but C
When the amount is 100 ppm, cracks occur in the film,
This is because if it exceeds ppm, thermal decomposition is not sufficient, which is not preferable.

Further, in the present invention, in order to form the corrosion resistant resin layer by electrodeposition coating, the permanent magnet body having the tin oxide film adhered on the surface is dipped in the aqueous paint, and the permanent magnet body is used as an anode or a cathode. , Supplying a direct current between the permanent magnet body and the counter electrode to electrically coat the entire permanent magnet body,
An electrodeposition coating method for forming a corrosion-resistant resin layer on the surface can be adopted.Anion electrodeposition coating method with the treated permanent magnet body as the anode or cation electrodeposition coating method with the treated permanent magnet body as the cathode is used. Can be adopted. The resin used in the anion electrodeposition coating method is a polycarboxylic acid resin having a drying oil, polyester, polybutadiene, epoxy ester, polyacrylic acid ester and the like as a nucleus, and usually,
It is neutralized with an organic amine or a base such as caustic potash, made into an aqueous solution or dispersed in water, and becomes negatively charged. The resin used in the cationic electrodeposition coating method is mainly a polyamine resin having an epoxy resin, an acrylic resin or the like as a nucleus, and is usually neutralized with an organic acid to be an aqueous solution or a water dispersion. It is positively charged. The thickness of the corrosion-resistant resin layer formed by electrodeposition coating is preferably 50 μm or less, and more preferably 5 to 30 μm. Further, for the purpose of improving the rust preventive coating reinforcement, the above resin may contain a rust preventive pigment such as zinc oxide, zinc chromate, zinc strontium chromate, and red lead, or one containing benzotriazole. But it's okay.

Rare earth element R used in the permanent magnet of the present invention
a occupies 10 atomic% to 30 atomic% of the composition, but N
At least one of d, Pr, Dy, Ho, Tb, or further La, Ce, Sm, Gd, Er, Eu,
Those containing at least one of Tm, Yb, Lu and Y are preferable. Usually, only one kind of Ra is sufficient, but in practice, a mixture of two or more kinds (Misch metal, didymium, etc.) can be used for reasons of availability. It should be noted that this Ra does not have to be a pure rare earth element, and may contain impurities that are unavoidable in manufacturing within a range that is industrially available. Ra is an essential element in the above-mentioned permanent magnet, and if less than 10 atomic%, the crystal structure is α-.
Since it has a cubic structure with the same structure as iron, high magnetic properties, especially high coercive force, cannot be obtained. If it exceeds 30 atomic%, the Ra-rich nonmagnetic phase increases and the residual magnetic flux density (Br) decreases. A permanent magnet with excellent characteristics cannot be obtained. Therefore, R
The range of 10 at% to 30 at% is desirable.

B is an essential element in the above-mentioned permanent magnet, and if it is less than 2 atomic%, the rhombohedral structure becomes the main phase and a high coercive force (iHc) cannot be obtained, and if it exceeds 28 atomic%, it is rich in B. Non-magnetic phase increases and residual magnetic flux density (Br)
, The excellent permanent magnet cannot be obtained. Therefore, B is preferably in the range of 2 atom% to 28 atom%.

Fe is an essential element in the above-mentioned permanent magnets. If it is less than 65 atomic%, the residual magnetic flux density (Br) is lowered, and if it exceeds 80 atomic%, a high coercive force cannot be obtained. % To 80 atomic% is desirable.
Further, substituting a part of Fe with Co can improve the temperature characteristics without deteriorating the magnetic characteristics of the obtained magnet. However, when the Co substitution amount exceeds 20% of Fe, it is contrary. It is not preferable because the magnetic properties deteriorate. When the amount of substitution of Co is 5 at% to 15 at% in terms of the total amount of Fe and Co, (Br) is increased as compared with the case where no substitution is made, which is preferable for obtaining a high magnetic flux density.

In addition to Ra, B, and Fe, the presence of impurities that are inevitable in industrial production can be tolerated. For example, part of B is 4.0 wt% or less of C, 2.0 wt% or less of P, 2 .0
By substituting at least one of S of 2.0 wt% or less and Cu of 2.0 wt% or less with a total amount of 2.0 wt% or less, it is possible to improve the manufacturability of the permanent magnet and reduce the cost.
Furthermore, Al, Ti, V, Cr, Mn, Bi, Nb, T
a, Mo, W, Sb, Ge, Sn, Zr, Ni, Si,
At least one of Zn and Hf is Fe-B-Ra.
It can be added to a permanent magnet material because it is effective in improving the coercive force, squareness of demagnetization curve, improving manufacturability, and reducing cost. In addition, the upper limit of the addition amount is to set (BH) max of the magnetic material to 20 MGOe or more,
Since (Br) is required to be at least 9 kG or more, a range satisfying the condition is desirable.

The permanent magnet of the present invention comprises a compound having a tetragonal crystal structure having an average crystal grain size in the range of 1 to 80 μm as a main phase, and a volume ratio of 1% to 50% of a nonmagnetic phase ( (Excluding an oxide phase). The permanent magnet according to the present invention exhibits a coercive force iHc ≧ 1 kOe, a residual magnetic flux density Br> 4 kG, and a maximum energy product (BH).
max indicates (BH) max ≧ 10 MGOe, and the maximum value reaches 25 MGOe or more.

[0017]

The Fe-B-Ra-based permanent magnet having the corrosion-resistant resin layer formed by electrodeposition coating through the tin oxide film according to the present invention is
Under severe atmospheric conditions, there is little deterioration from the initial magnet characteristics, and the reason why the magnet characteristic values are extremely stable is not yet clear. However, when the surface of the Fe-B-Ra-based sintered magnet body is directly coated with the corrosion-resistant resin layer by electrodeposition coating, the temperature is kept at 60 ° C. and the relative humidity is 90% under the severe corrosion resistance test conditions for 100 hours. , The magnet characteristic value deteriorates and becomes unstable. On the other hand, by forming a corrosion resistant resin layer by electrodeposition coating on the surface of the sintered magnet body through a tin oxide film having a specific film thickness, It has been revealed that the adhesion to the base is improved and the corrosion-resistant resin layer becomes dense, and the permanent magnet can be completely protected against changes in the external environment such as moisture and gas.

[0018]

【Example】

Example 1 A known casting ingot was crushed, finely crushed, molded, sintered, and heat-treated, and then 14Nd-0.5Dy-7B-78.
A magnet body test piece of 5Fe composition having a diameter of 12 mm and a thickness of 2 mm was obtained. The magnet characteristics are shown in Table 1. Next, Sn (O
C ₃ H ₇ ) ₄ 1 gr was dissolved in triethanolamine 1 l to prepare a Sn alkoxide solution, and this solution was well stirred, and then the magnet test piece was dipped and pulled up to remove excess liquid. After drying at 80 ° C, 4 in Ar atmosphere
A tin oxide film was formed by heat treatment at 00 ° C. for 5 hours to obtain a film having a film thickness of 200Å. The amount of C in the film was 300 ppm.

Further, epoxy-based Svia CED, S-20 (manufactured by Shinto Paint Co., Ltd.) is used as the cationic electrodeposition paint, and Nd-Dy-B coated with the tin oxide film on the surface is used.
Using an Fe-based permanent magnet as a cathode and a SUS316 material as an anode, electrodeposition coating was performed at a temperature of 28 ° C., a voltage of 150 V for 3 minutes, followed by washing with water, drying, and further heating at 180 ° C. for 30 minutes.
After holding for a minute, an epoxy resin layer was formed on the surface. The resin layer thickness was 16 μm.

After that, the obtained permanent magnet having a corrosion-resistant resin layer formed by electrodeposition coating through the tin oxide film according to the present invention was allowed to stand for 500 hours at a temperature of 80 ° C. and a relative humidity of 90%. The characteristics and the deterioration status thereof were measured.
The results are shown in Table 1.

Comparative Example 1 On the sintered magnet body obtained under the same composition and under the same manufacturing conditions as in Example 1, an epoxy resin layer was directly formed by the same electrodeposition coating as in Example 1. The resin layer thickness was 17 μm. Then, the permanent magnet of Comparative Example was heated at a temperature of 80 ° C. and a relative humidity of 90%
When left for 300 hours under the above condition, swelling occurred in the edge portion, and after leaving for 500 hours, rust was partially generated. Table 1 shows the results of measuring the magnet characteristics after leaving for 500 hours and the deterioration thereof.

[0022]

[Table 1]

[0023] The permanent magnet of this invention, the temperature 80 ° C., magnetic properties after 500 hours under a relative humidity of 90%, and the result of measuring the deterioration condition represents the Table 1, further 1000
No rust is generated even on the surface after a lapse of time, and the magnet characteristics are almost unchanged. On the other hand, the deterioration of the magnet characteristics of the comparative sintered magnet body before and after the corrosion resistance test was as follows: temperature 80 ℃, relative humidity 90
The characteristics after standing for 500 hours under the condition of 100% are as shown in Table 1, and after 1000 hours, rust was partially generated on the surface.

[0024]

The Fe-B-Ra-based permanent magnet body according to the present invention was left standing for 1000 hours under severe corrosion resistance test conditions, particularly at a temperature of 80 ° C. and a relative humidity of 90%, as in Examples. , There is almost no deterioration of its magnet characteristics,
It is extremely suitable as the most demanded high-performance and inexpensive permanent magnet.

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-63-77102 (JP, A) JP-A-2-162035 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01F 1/00 C25D 13/12 C22C 38/00 303 C23C 28/00 H01F 41/00

Claims (2)

(57) [Claims] 1. Fe-B-Ra whose main phase is a tetragonal phase
100ppm-1000pp of C on the system permanent magnet body surface
A corrosion-resistant permanent magnet, characterized in that it has a corrosion-resistant resin layer formed by electrodeposition coating through a tin oxide film having a thickness of 500 Å or less and containing m. 2. Fe-B-Ra whose main phase is a tetragonal phase
After cleaning the surface of the system permanent magnet body, after dipping the magnet body in a tin alkoxide compound solution or applying a tin alkoxide compound solution to the magnet surface,
A tin oxide film layer containing 100 ppm to 1000 ppm of C is formed by a heat treatment of holding at 450 ° C. for 30 minutes to 10 hours, and further, the magnet body is immersed in a resin solution and subjected to electrodeposition coating treatment, and then the surface of the magnet body is coated. A method for producing a corrosion-resistant permanent magnet, which comprises forming a corrosion-resistant resin layer.