JPH09260120A - R-fe-b type permanent magnet superior in electric insulation, heat resistance and corrosion resistance and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an R-Fe-B type permanent magnet superior in electric insulation, heat resistance and corrosion resistance by covering a specified Al or Zn surface metal layer of specified thickness on the surface of this magnet with a polyimide resin through a chromate-treated film by the vacuum evaporation polymerization. SOLUTION: An Al or Zn first metal film of 1.0-10.0μm thick is formed on the surface of an R-Fe-B type permanent magnet having a tetragonal main phase and polyimide film of 2.0-10μm thick is formed on this metal film to form a magnet superior in electric insulation, heat resistance and corrosion resistance. The manufacturing method thereof comprises cleaning the surface of this magnet having the tetragonal main phase, forming the Al or Zn metal film of 1.0-10.0μm on the surface of the magnet by the plating or vapor phase forming method, treating the metal film with chromate, and forming a polyimide film layer of 2.0-10μm thick in vacuum by the evaporation polymerization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an R—Fe—B system permanent magnet and a manufacturing method thereof, and a base metal of Al or Zn having a predetermined film thickness formed on the surface of the R—Fe—B system permanent magnet. By providing a chromate film on the film and then using a polyimide resin by vapor deposition polymerization method, the electrical insulation, heat resistance and corrosion resistance required for permanent magnets for automobile motors have been achieved. The present invention relates to an R-Fe-B based permanent magnet having excellent corrosion resistance and a method for manufacturing the same.

[0002]

2. Description of the Related Art R-Fe-B permanent magnets have the best magnetic properties among the practically used magnets, but in order to use them as permanent magnets for multi-pole type motors for automobiles. First, in order to prevent the generation of eddy currents in the permanent magnets, it is necessary to wear a coating having excellent electrical insulation properties. Also, in an automobile, the temperature of the engine room in which the motor is placed during traveling is 200 As the temperature rises to ℃, it is required for the magnet to be used that has both heat resistance and corrosion resistance.

R-Fe-B system permanent magnets have the drawback of poor corrosion resistance and temperature characteristics of magnetic properties. Therefore, it is proposed to coat the magnet surface with a resin in order to improve the corrosion resistance (Japanese Patent Laid-Open No. 60-63902). However, even if the corrosion resistance is improved by the above method, there is a problem that the heat resistance is not sufficient and the electric insulation is poor, and an R-Fe-B permanent magnet having excellent magnetic characteristics is used in automobiles. It is the cause that cannot be used for the motor.

[0004]

The inventors of the present invention use R-Fe-B based permanent magnets having excellent magnetic properties in motors for automobiles, and therefore improve and improve not only corrosion resistance but also electric insulation and heat resistance. Therefore, as a result of various studies, it was found that by covering the surface of the magnet with a polyimide resin, excellent magnetic properties are provided, and in addition to corrosion resistance, electric insulation and heat resistance are greatly improved.

When a polyimide resin is directly applied to the surface of a magnet by vapor deposition polymerization, water is generated on the surface of the magnet during the imidization treatment under normal pressure after the polymerization reaction, and the water reacts with the surface of the magnet. It was found that there is a problem that the adhesion of the polyimide resin to the magnet surface is impaired, and as a result of further investigation, the magnet surface was cleaned by an ion sputtering method or the like, and then a plating method or an ion method was applied to the magnet surface. By a vapor phase thin film forming method such as a plating method, an ion sputtering method, or a vapor deposition method, an Al having a specific film thickness with good adhesion to an R-Fe-B system permanent magnet and adhesion to a polyimide resin.
Alternatively, an underlying metal film made of a metal such as Zn or an alloy film is formed, and then a polyimide resin is formed thereon by vapor deposition polymerization to form an R-Fe-B system excellent in electrical insulation, heat resistance and corrosion resistance. It was proposed that a permanent magnet be obtained (Japanese Patent Application No. 7-354673).

However, since the Al coating film and the Zn coating film deposited by the plating method or the vapor deposition method are deposited and formed on the surface of the magnet body, the density is insufficient, and it is very porous and has many pinholes. In the imidization reaction at the time of forming the polyimide film, water that has generated water and has diffused through the polyimide film at high temperature and high humidity reaches the interface, and at the pinhole portion, the reaction between the R-Fe-B based magnet body and water. It was found that there is a problem in that sufficient corrosion resistance cannot be obtained due to corrosion.

The present invention satisfies the electric insulation and heat resistance required for a permanent magnet of a multi-pole type motor for an automobile,
In addition, after forming a base metal film of a metal or alloy film such as Al or Zn having a specific film thickness, which was developed for the purpose of providing an R-Fe-B based permanent magnet excellent in corrosion resistance, a polyimide resin is vapor-deposited and polymerized thereon. The R-Fe-B system permanent magnet formed by the method eliminates the problem that the underlying metal film in the R-Fe-B system permanent magnet is porous, and has sufficient corrosion resistance and excellent electric insulation and heat resistance. It is intended to provide a manufacturing method thereof.

[0008]

In order to solve the drawbacks of the Al coating or Zn coating of the underlying metal film, the inventors have
As a result of various studies, by performing chromate treatment on the Al coating surface or the Zn coating surface of the underlying metal film, chromate is filled in the pinholes of the Al coating or Zn coating, and The present invention has been completed by finding that the corrosion resistance is further improved by being formed on the coating surface or the Zn coating surface.

That is, according to the present invention, the film thickness of 1.0 provided on the surface of the R-Fe-B system permanent magnet body whose main phase is tetragonal.
A film having a thickness of 2.0 μm to 1 is formed on the underlying metal film of Al or Zn having a thickness of μm to 10.0 μm via a chromate treatment film.
It is an R-Fe-B based permanent magnet having a 0 μm polyimide film and excellent in electrical insulation, heat resistance and corrosion resistance.

Further, according to the present invention, after cleaning the surface of the R-Fe-B system permanent magnet body whose main phase is tetragonal, a film thickness of 1.0 is formed on the surface of the magnet body by a plating method or a vapor deposition method.
After forming a base metal film of Al or Zn having a thickness of μm to 10.0 μm, the metal film is subjected to a chromate treatment, and the magnet body is housed in a vacuum container to form a film having a thickness of 2.0 μm by a vapor deposition polymerization method. It is a method for producing an R-Fe-B based permanent magnet excellent in electrical insulation, heat resistance and corrosion resistance, which forms a polyimide film layer having a thickness of 10 µm.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, after the magnet surface is cleaned by an ion sputtering method or the like, R-Fe-B is formed on the magnet body surface by a vapor phase thin film forming method such as a plating method or an ion plating method. After forming a base metal film of an Al film or a Zn film of a specific thickness having good adhesion with a permanent magnet and adhesion with a polyimide resin, chromate treatment is applied to the metal film to form the chromate film. By forming a polyimide resin on the above by vapor deposition polymerization, it is possible to obtain a desired high-performance R-Fe-B based permanent magnet having excellent electrical insulation, heat resistance, and corrosion resistance, which can be particularly used for automobile motors. Characterize.

In the present invention, the reason why the thickness of the Al coating or Zn coating of the underlying metal film provided on the cleaned magnet surface is limited to 1.0 μm to 10.0 μm is 1.0 μm.
If it is less than m, the adhesion to the magnet surface is insufficient and 10.0
When the thickness exceeds μm, there is no problem in terms of effectiveness, but the cost of the underlayer increases, which is not practical and preferable.
The Al film or Zn film thickness of the underlying metal film is 1.0 μm
The thickness is 10.0 μm. In addition, the method for forming the underlying metal film is
A plating method such as an electrolytic plating method or an electroless plating method, or a vapor phase thin film forming method such as an ion plating method, an ion sputtering method, or a vapor deposition method may be used.

In the present invention, the thickness of the chromic acid coating is preferably 0.01 μm to 0.1 μm. If it is less than 0.01 μm, sufficient corrosion resistance cannot be obtained, and if it exceeds 0.1 μm, peeling in the chromate coating occurs. Is likely to occur and is not preferable. Further, a known method can be adopted for the chromate treatment,
2-250 g of chromic anhydride or alkali chromate
/ L, if necessary, sulfuric acid, nitric acid, fluoride as an additive,
A solution containing a tungsten compound or the like is used to form a film by dipping or spraying.

In the present invention, the vacuum degree of the vacuum vessel for vapor deposition polymerization is preferably 1 Pa to 10 ^-3 Pa, and when it exceeds 1 Pa, the polymerization reaction becomes non-uniform and the film quality deteriorates.
If it is less than 10 ^-3 Pa, the evaporation of the monomer is extremely small,
It is not preferable because a stable polymerization reaction does not occur. Also,
The temperature of the substrate magnet during vapor deposition polymerization is preferably set to 150 ° C. to 200 ° C. When the temperature is lower than 150 ° C., the adhesion to the magnetic substrate is not sufficient, and when it exceeds 200 ° C., the vapor deposition polymerization reaction on the magnetic substrate occurs. The temperature of the substrate magnet is preferably set to 150 ° C. to 200 ° C. because it does not proceed promptly.

In the present invention, the two kinds of raw material monomers used for vapor deposition polymerization are aromatic carboxylic acid dianhydride and aromatic diamine, and as aromatic carboxylic acid dianhydride, pyromellitic acid anhydride and acid dianhydride. As the aromatic diamine, diaminodiphenyl ether, p-phenyldiamine and the like are used. In addition, the reason for accelerating vapor deposition of two types of raw material monomers at 200 ° C. to 250 ° C. in a vacuum container is that the amount of evaporation is insufficient below 200 ° C.
When the temperature exceeds ℃, the evaporation rate is too high and it is difficult to control the film thickness.
Because it is not preferable.

Further, in the present invention, if the imidization temperature for forming the polyimide resin is less than 280 ° C., the imidization reaction does not proceed sufficiently, the adhesion to the underlying metal is not sufficient, and if it exceeds 380 ° C. 280 ° C. to 38 because resin deteriorates and becomes brittle, cracks and the like occur and peeling occurs
Set to 0 ° C.

Rare earth element R used in the permanent magnet of the present invention
Accounts for 10 to 30 atomic% of the composition, but Nd,
At least one of Pr, Dy, Ho, and Tb; or La, Ce, Sm, Gd, Er, Eu, T
Those containing at least one of m, Yb, Lu, and Y are preferable. Also, usually one of R is sufficient,
In practice, a mixture of two or more kinds (mish metal, dymium, etc.) can be used for reasons such as convenience in obtaining. Note that R may not be a pure rare earth element, and may contain impurities which are unavoidable in production within the industrially available range.

[0018] R is an essential element in the R-Fe-B system permanent magnet, and if it is less than 10 atomic%, the crystal structure has a cubic crystal structure of α-iron with the same structure, so that high magnetic properties, especially high coercive force are obtained. If it exceeds 30 atomic%, the R-rich non-magnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet having excellent characteristics cannot be obtained. Therefore, R is l
A range of 0 to 30 atomic% is desirable.

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

Fe is an essential element in the above-mentioned permanent magnets. If it is less than 65 atom%, the residual magnetic flux density (Br) is lowered, and if it exceeds 80 atom%, a high coercive force cannot be obtained. % To 80 atomic% is desirable.
Further, substituting part of Fe with Co can improve the temperature characteristics without impairing the magnetic characteristics of the obtained magnet. However, when the amount of Co exceeds 20% of Fe, the conversely occurs. 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 R, B, and Fe, it is possible to allow the presence of unavoidable impurities in industrial production. For example, a part of B may be 4.0 wt% or less of C, 2.0 wt% or less of P, .0
By replacing at least one of S by wt% or less and Cu by 2.0 wt% or less with a total amount of 2.0 wt% or less, it is possible to improve the productivity and reduce the cost of the permanent magnet.
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 added to the R—Fe—B system permanent magnet because it is effective in improving the coercive force, squareness of demagnetization curve, improving manufacturability, and reducing cost. can do. The upper limit of the addition amount is (BH) max of 20 MGOe or more for the magnet material,
Since r) is required to be at least 9 kG or more, a range satisfying the condition is desirable.

Further, 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 nonmagnetic phase of 1% to 50% by volume ( (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.

[0023]

EXAMPLE A cast ingot of 17Nd-1Pr-75Fe-7B composition was crushed, finely crushed, formed, sintered, and heat-treated to obtain a magnet body test piece having a diameter of 12 mm × 2 mm. Table 1 shows the magnet characteristics.

The inside of the vacuum chamber was evacuated to 1 × 10 ⁻³ Pa or less, and surface sputtering was performed at Ar gas pressure of 3 Pa and −300 V for 20 minutes to clean the surface of the magnet body. Table 2 on the magnet surface under
After forming the underlying metal coating layer of Al (Example 1) or Zn (Example 2) shown in Fig. 3, as chromate treatment conditions, Alsurf 600N (trade name, made by Nippon Paint) 2%, pH 2, 40 ° C 3 It was immersed for a minute to form a chromate film with a thickness of 0.03 μm.

Thereafter, the inside of the vacuum vessel was set to a vacuum degree of 1 × 10 ^-2 Pa, pyromellitic dianhydride was heated at 220 ° C. as one evaporation source, and diaminodiphenyl as another evaporation source. The ether is heated at 210 ° C., the magnet substrate is further heated at 170 ° C., and the treatment is performed for 1 hour, and the raw material monomer is vapor-deposited and polymerized on the surface of the magnet to form a polyamic acid film. Next, under normal pressure, it was heated in a nitrogen atmosphere at 300 ° C. for 1 hour for imidization treatment to form a polyimide resin film, thereby forming a polyimide resin film with a thickness of 5 μm.

Thereafter, the permanent magnet test piece having the obtained polyimide resin film on the surface was subjected to a temperature of 80 ° C. and a relative humidity of 90.
%, The magnetic properties, volume resistivity and heat distortion temperature were measured. The measurement results are shown in Table 3. The volume resistivity is used to evaluate the electrical insulation property, and the electrode resistance is measured, and the resistance between the coating surface and the magnet is measured and calculated from the following equation (1). ρ = R · S / l (1) where ρ: volume resistivity Ω · cm, R: resistance Ω, S: electrode area cm ² , l: polyimide film thickness cm. It was evaluated and was set to a temperature at which discoloration, cracks and the like of the coating film were left in the atmosphere at that temperature for 20 hours.

Comparative Example 1 A magnet test piece having the same composition as that of the example was surface-cleaned under the same conditions as the example, and then a polyimide resin film was directly formed on the surface of the magnet to a thickness of 5 μm under the same conditions as the example. Then, under the same temperature of 80 ° C. and relative humidity of 90% as in the example, 5
The magnetic properties, volume resistivity and heat distortion temperature after standing for 00 hours were measured, and the results are shown in Table 3.

Comparative Example 2 A magnet body test piece having the same composition as that of the example was surface-cleaned under the same conditions as those of the example, and then an Al coating layer was formed as a base metal layer on the surface of the magnet under the same conditions as the example. After the polyimide resin was formed to a thickness of 5 μm under the same conditions as in the example, magnetic properties, volume resistivity, and heat distortion temperature were measured after standing for 500 hours under the same temperature of 80 ° C. and relative humidity of 90% as in the example. The results are shown in Table 3.

Comparative Example 3 A magnet body test piece having the same composition as that of the example was surface-cleaned under the same conditions as the example, and then a Zn coating layer was formed on the surface of the magnet as a base metal layer under the same conditions as the example. After forming a polyimide resin film with a thickness of 5 μm under the same conditions as in the example, magnetic properties, volume resistivity, and heat distortion temperature were measured after standing for 500 hours under the same temperature of 80 ° C. and relative humidity of 90% as in the example. The results are shown in Table 3.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

The R-Fe-B system permanent magnet according to the present invention is made of Al having a specific predetermined film thickness provided on the surface of the present system permanent magnet.
Alternatively, as shown in the examples, excellent electrical insulation, heat resistance, and sufficient corrosion resistance can be obtained by coating with a polyimide resin by a vapor deposition polymerization method via a chromate-treated film on a Zn base metal layer. Has been achieved, and R-Fe-B
It can provide excellent magnet characteristics originally possessed by system-based permanent magnets to severe applications such as permanent magnets for multi-pole type automobile motors.
It is possible to contribute to the reduction in size and weight of the motor.

Claims (2)

[Claims] 1. A chromate-treated film is formed on an underlying metal film of Al or Zn having a thickness of 1.0 μm to 10.0 μm provided on the surface of an R—Fe—B system permanent magnet body whose main phase is tetragonal. R-Fe excellent in electrical insulation, heat resistance, and corrosion resistance having a polyimide film with a film thickness of 2.0 μm to 10 μm
-B system permanent magnet. 2. A film having a thickness of 1.0 .mu.m-10.0 .mu.m formed on the surface of the magnet body by a plating method or a vapor deposition method after cleaning the surface of the R--Fe--B system permanent magnet body whose main phase is tetragonal.
After forming a base metal film of Al or Zn of m, the metal film is subjected to a chromate treatment, and the magnet body is further housed in a vacuum container to form a film having a thickness of 2.0 μm to 10 μm by a vapor deposition polymerization method.
Electrical insulation and heat resistance to form a μm polyimide film layer
A method for manufacturing an R-Fe-B based permanent magnet having excellent corrosion resistance.