JP3305786B2 - Manufacturing method of permanent magnet with excellent corrosion resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rare earth permanent magnet such as an Fe-BR based magnet, and more particularly to an ionized H-based permanent magnet.
₍₂₎ A permanent magnet whose surface has been cleaned with a gas is coated with a titanium-based compound by ion plating in a high-vacuum atmosphere to prevent gas generation from the magnet surface and to be usable even in vacuum. The present invention relates to a method for manufacturing a magnet.

[0002]

2. Description of the Related Art Heretofore, rare earth cobalt magnets having much higher magnetic properties than alnico magnets and hard ferrite magnets have been used as rare earth magnets, but R (R is at least one of rare earth elements including Y). As Nd or Pr
Fe-BR-based permanent magnets, which use light rare earths, which are rich in resources, are excellent in workability, and have Fe as a main component and exhibit an extremely high energy product of 30 MGOe or more, are widely used.

[0003] However, a permanent magnet made of an Fe-BR-based magnetic anisotropic sintered body having excellent magnetic properties is a rare earth element which is easily oxidized in air to form a stable oxide gradually. Since it contains elements and iron, for example, when incorporated in a magnetic circuit, the oxides generated on the magnet surface cause a reduction in the output of the magnetic circuit and variations between the magnetic circuits, and also cause the peripheral oxide to fall off due to the removal of the surface oxide. There was a problem of contamination of the equipment.

Conventionally, coatings formed by ion plating have excellent adhesion and high density, and are used in various industrial fields to improve corrosion resistance, lubricity, abrasion resistance, and heat resistance. . In particular, TiN and TiC films are widely used as wear-resistant coatings for tools and coatings for decorative articles because of their excellent corrosion resistance and wear resistance.

[0005] The applicant has previously reported that Al, Al is deposited on the surface of a Fe-BR-based tetragonal permanent magnet body by ion plating.
A permanent magnet having a corrosion-resistant vapor-phase plating layer made of a metal such as Ni, Cr, Cu, Co, or an alloy thereof, or Al ₂ O ₃ , Cr ₂ O ₃ , TiN, AlN, TiC, etc.
No. -150201). For example, specifically, a permanent magnet is placed in a vacuum vessel of 1 × 10 ⁻² Torr or less,
In addition to evaporating the Ti flakes by arc discharge, N ₂ gas is introduced into the vessel, and Ti evaporation and N ₂ gas ion irradiation are performed for 3 hours to form a TiN thin film on the surface of the permanent magnet. The film obtained by this method has a uniform film thickness, suppresses oxides generated on the surface of the permanent magnet material, and does not deteriorate even when a corrosive chemical or the like is used without deteriorating magnetic properties. A permanent magnet that is stable over a long period of time can be obtained.

[0006]

It is well known that contamination of the surface of a permanent magnet material prior to coating reduces the adhesion of the coating, and insufficient cleaning can cause the coating to peel. . In the conventional method, a specific method for cleaning is not proposed, but usually, washing with an organic solvent or a neutral detergent is followed by washing with water, or bombardment of Ar ions in an Ar atmosphere to remove impurities on the surface. Had been removed. However, in many cases, the coating was not successfully applied, probably because these cleaning methods were insufficient.

Further, even with a permanent magnet having an oxidation-resistant coating, a small amount of gas is inevitably generated from the magnet because the permanent magnet body is a sintered body and porous.
When a permanent magnet coated with a titanium-based coating is used in a device that places a permanent magnet in an ultra-high vacuum, such as a drift tube linear accelerator or undulator, the titanium compound coating on the surface of the permanent magnet may peel off or become uniform. If not, the gas of the permanent magnet leaks from the magnet surface and may not be used. In addition, although ion plating has good coverage of the coating, the formation of the coating is mainly limited to the portion facing the evaporation source of the permanent magnet. May be generated.

The present invention solves the conventional problems of a rare earth permanent magnet having a titanium compound film formed by an ion plating method such as a sintered permanent magnet. It is an object of the present invention to provide a method for producing a permanent magnet having a uniform titanium compound coating, preventing generation of gas from the magnet surface, and having excellent corrosion resistance which can be used even in a vacuum.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a method for manufacturing a permanent magnet having excellent corrosion resistance, in which a titanium compound film is formed on the surface of a rare earth permanent magnet by an ion plating method. 40 permanent magnets
After heating to 0 ° C. to 600 ° C. and holding for 1 to 2 hours, 1 ×
While maintaining a degree of vacuum of 10 ^-4 to 1 × 10 ^-5 Torr, H
₂ Introduce gas, ionize by glow discharge, heat
After applying a negative charge to the permanent magnet to clean the magnet surface, in a required gas atmosphere or vacuum atmosphere, titanium is evaporated or ionized to perform ion plating, and the permanent magnet surface is coated with a titanium compound. A method for manufacturing a permanent magnet having excellent corrosion resistance.

[0010]

Further, the present invention is characterized in that, in each of the above structures, ion plating is performed by introducing N ₂ gas in a high vacuum of 1 × 10 ⁻⁴ Torr or more and evaporating or ionizing Ti. And a method for producing a permanent magnet having excellent corrosion resistance.

In the present invention, a permanent magnet coated with a titanium-based compound uses a resource-rich light rare earth element mainly composed of Nd and Pr as R, and contains B and Fe as main components.
Fe- which shows an extremely high energy product of 0 MGOe or more
Rare earth permanent magnets such as BR permanent magnets and rare earth cobalt magnets.

In the ion plating method used in the present invention, for example, arc discharge is performed using the vapor pressure of an evaporating substance in a high vacuum to ionize the evaporant and strongly coat the surface of the permanent magnet to be coated. This is a physical vapor deposition method to be generated. The ion plating method is classified into various methods according to an evaporation or ionization method.The ion plating method is a method of depositing an evaporating substance on a substrate while bombarding ions of the evaporating substance and ions of a gas. This is a method that ionizes atoms and increases their kinetic energy to increase the film quality, adhesion, and coverage with complicated substrates. The titanium-based compound coated on the surface of the permanent magnet is T
iN, TiC, etc., by this method, Si ₃ N ₄ ,
Oxidation-resistant films can be formed even with nitrides such as C-BN, HfN, and AlN.

[0014] In order to improve the adhesion of the titanium compound to the permanent magnet, it is very important to clean the surface of the permanent magnet. If the cleaning is insufficient, the adhesion of the magnet surface will be impaired, and the deposited layer will be peeled off. In the present invention,
In the cleaning step, the permanent magnet is subjected to bombard cleaning in an H ₂ atmosphere. As a cleaning method, first, the surface of the rare-earth permanent magnet is cleaned with an organic solvent or the like. Thereafter, it is preferable to perform washing with water or ultrasonic washing with a detergent, steam washing, or the like. However, this is not always enough. Next, the washed permanent magnet is inserted into the vapor deposition chamber. However, since it is necessary to sufficiently exhaust the inside of the vapor deposition chamber, it is preferable to use an ultra-high vacuum exhaust device. The exhaust gas in the deposition chamber in the present invention is 10 ⁻³ to 10 ⁻⁵ Torr.
It is desirable to perform for 40 to 50 minutes up to r.

Further, before cleaning with H ₂ gas, the permanent magnet is heated in a vacuum. Heating removes the gas adsorbed on the magnet surface and helps to diffuse the vapor deposition material to the magnet surface and promote the chemical reaction. The heating temperature is preferably from 400 ° C. to 600 ° C., and the heating holding time is preferably about 1 to 2 hours. If the heating before the cleaning treatment is performed at a temperature lower than 400 ° C., sufficient gas is not released. In particular, to release hydrogen accumulated in the magnet, heating exceeding 600 ° C. is unnecessary, and the holding time is set to 1 to 2 hours. This is to release hydrogen that is bound not only on the magnet surface but also inside the magnet.

[0016] Upon cleaning with H ₂ gas, while ionized by glow discharge in the vacuum chamber after heating the holding insert the H ₂ gas, applying a negative charge to the heated permanent magnets.
Then, the surface of the permanent magnet substrate is irradiated with ions, and an oxide layer and foreign substances on the surface are reduced to obtain a cleaned surface.
Gas that is inserted into the deposition chamber is H _2. The H ₂ gas has better coverage of the coating on the substrate surface during ion plating than the Ar gas, so that a more uniform coating can be obtained. After cleaning the magnet surface, the inside of the deposition chamber is evacuated to maintain a predetermined degree of vacuum of 1 × 10 ⁻⁴ Torr or more.
If the degree of vacuum is less than 1 × 10 ⁻⁴ Torr, a gas such as hydrogen existing in the evaporation chamber cannot be completely removed, so that 1 × 1 ^-4
It is preferably set to 0 ^-4 Torr or more.

Ti, which is a deposition material, is disposed on a positive electrode in a deposition chamber, and is melted and ionized by a high-voltage DC plasma discharge or an electron beam. A masking member is provided between the film and the permanent magnet to be coated. Intervening. Further, N ₂ gas having a dew point of −70 ° C. to −60 ° C. is introduced while evacuation of the deposition chamber is continued to increase the degree of vacuum. When ionization of the deposition material is stabilized, the masking is removed and the deposition material is brought closer to the permanent magnet. Then, the ions of the evaporated deposition material repeatedly collide with molecules of the N ₂ gas several times on the way, and then arrive at the surface of the permanent magnet.
It is also deposited on the surface of the permanent magnet that does not face the deposition material. The deposition time during this is preferably 2-3 hours. Since the amount of evaporation of the deposition material can be controlled by changing the voltage of the arc current, the required amount of deposition of the deposition material can be obtained.

In the ion plating method of the present invention, although the covering of the coating is good due to, for example, the scattering effect of N ₂ gas, the formation of the coating is mainly biased to the portion facing the deposition material, so that the film pressure unevenness. It is preferable to use a jig for obtaining a coating free from defects. The jig preferably rotates and revolves so that the permanent magnet receives the ionized vapor deposition material over the entire surface by axial rotation of the jig to which the permanent magnet to be coated is attached. This jig may be appropriately selected according to the type, size, shape, etc. of the permanent magnet to be coated. However, since it is necessary to form a coating on the entire surface of the permanent magnet, a multi-axis rotation jig, a self-revolution jig, etc. Can be used. In addition, because the unevenness of the coating is likely to be generated at the bonded part between the permanent magnet and the jig,
It is desirable to put a permanent magnet in a net-shaped jig and to make a contrivance such that ions of the vapor deposition material are wrapped around the entire surface of the permanent magnet.

[0019]

According to the present invention, as a process prior to ion plating, after heating and holding for a predetermined time, H ₂ gas is introduced to ionize, and a negative charge is applied to the heated permanent magnet to clean the magnet surface. By the cleaning treatment, the gas adsorbed on the magnet surface is released, the diffusion of the deposited material to the magnet surface and the chemical reaction are promoted, and the oxidized layer and foreign substances on the surface are reduced to obtain a cleaned surface. As a result, the titanium compound film to be coated becomes uniform and dense, and gas generation from the magnet surface is prevented.

According to the high vacuum ion plating method of the present invention, a rare earth permanent magnet can be uniformly and densely coated with a titanium compound film, and has excellent corrosion resistance which does not generate gas even when used in a vacuum. It is possible to obtain In addition, since this titanium compound coating is decorative in gold, has a corrosion resistance and water resistance, and is a strong coating having a Pickers hardness Hv of 1900 to 2400 or more, it is used as an ultra-high vacuum device part. It can withstand long-term use.

[0021]

EXAMPLE A test piece having a size of 12 mm × 10 mm × 9 mm cut out from a Nd—Fe—B based magnet alloy was used as a rare earth magnet, and coating was performed by ion plating according to the present invention. As a pretreatment, the test piece was subjected to alkali washing, water washing, and washing with an organic solvent. FIG. 1 is a schematic explanatory view of the ion plating apparatus used in this embodiment. The vacuum vessel 1 has an intake system 2 for the introduced gas.
A plurality of stainless steel rod-shaped rotating jigs 5 are rotatable on a horizontal axis at predetermined intervals around the circumference of a rotating disk 4 rotating on a horizontal axis. A test piece 7 is fixed to the tip of a radial projection 6 around the rotation axis of the rotation jig 5.
Thus, the rotation jig 5 revolves and the rotation jig 5 itself rotates. Further, a crucible 8 having a heating device is held by a supporting device 9 so as to be horizontally movable, and a masking portion 10 is arranged outside the rotating disk 4 on which the rod-shaped rotation jig 5 is mounted. Heat and melt the Ti flake of
When held in a sufficiently evaporated state, the supporting device 9 moves the rotating disk 4 toward the center of the rotation axis.

After the pretreatment cleaning, the test piece 7 was mounted on a stainless steel rotation jig 5 shown in FIG. 1C, and a plurality of rotation jigs 5 were mounted on the circumference of the rotating disk 4. Thereafter, the vacuum vessel 1 was evacuated to a degree of vacuum of 1 × 10 ⁻⁵ Torr, and the test piece 7 was heated and maintained at about 400 ° C. for 1 hour. Further, while maintaining the inside of the container at a degree of vacuum of the order of 1 × 10 ⁻⁴ Torr, H ₂ gas was introduced from the suction line 2, a voltage of 500 V to 1 kV was applied to the test piece, and hydrogen ions were applied to the surface of the magnet. Was reduced and cleaned.
Further, while evacuating again to maintain 10 ⁻⁴ Torr, the Ti flakes of the coating material are melted in the masking section 10 by an arc discharge of 500 V to 1 kV in the crucible 8, and when the evaporation of Ti is stabilized, the dew point is −70. ° C N
_{2 The} gas was accelerated at an extraction voltage of 40 V, an ionization current of 100 mA, and a beam size of 4 × 10 cm ² ,
Then, the crucible 8 was moved to the center side of the rotating disk 4 and Ti evaporation and N ₂ gas ion irradiation were performed at an evaporation angle of ± 50 ° for 3 hours to form a 3 to 4 μm thick TiN thin film. After holding for 4 hours in the vacuum chamber 1, the test piece coated with TiN was taken out, and a uniform film without peeling or swelling was obtained. No corrosion occurred at all and good results were obtained.

Further, the test piece coated with TiN according to the present invention and a test piece not coated with a magnet similar to the test piece used in the examples were placed in a vacuum vessel and evacuated for 50 hours. There was a difference in the degree of vacuum. Ti
The gas release of the magnet coated with N was reduced to one-third or less as compared with the uncoated magnet, and it was found that no gas was generated even in a high vacuum, and the magnet was usable.

[0024]

According to the present invention, a rare-earth permanent magnet is formed by a high-vacuum ion plating method in which a permanent magnet whose surface is cleaned by ionized H ₂ gas is coated with a titanium compound by an ion plating method in a high vacuum atmosphere. A uniform and dense titanium compound film can be coated on the magnet, and a permanent magnet excellent in adhesion, corrosion resistance and water resistance can be obtained. Further, since this titanium compound coating is a uniform coating without dog bone or peeling, a permanent magnet having excellent corrosion resistance which does not generate gas even when used in a high vacuum can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of an ion plating apparatus according to the present invention, wherein A denotes a Ti flake heated and melted, B denotes an ion plating, and C denotes a rotation jig.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Intake path 3 Exhaust path 4 Rotating disk 5 Rotating jig 6 Projection part 7 Test piece 8 Crucible 9 Support device 10 Masking part

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01F 41/02 C23C 14/06 C23C 14/32 H01F 1/053

Claims (2)

(57) [Claims] 1. A method for producing a permanent magnet having excellent corrosion resistance for forming a titanium-based compound film on a rare earth-based permanent magnet surface by ion plating method, the permanent magnet surface cleaning with an organic solvent, 400 ° C. to 600 Heat to ℃ 1
After holding for about 2 hours, 1 × 10 ^-4 to 1 × 10 ^-5 Torr
Glow discharge by introducing H ₂ gas while maintaining the vacuum degree
After applying a negative charge to the heated permanent magnet to clean the magnet surface, in a required gas atmosphere or vacuum atmosphere, Ti is evaporated or ionized to perform ion plating, and the titanium surface is coated with titanium. A method for producing a permanent magnet having excellent corrosion resistance, characterized by coating a base compound. 2. N 2 in a high vacuum of 1 × 10 ⁻⁴ Torr or more.
_The method for producing a permanent magnet having excellent corrosion resistance according to claim 1 , wherein _two gases are introduced and Ti is evaporated or ionized to perform ion plating.