JP2003017349A - Method of manufacturing magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a magnet at low cost which can manufacture the magnet little in a loss of its magnetic characteristics, excellent in corrrosion resistance and adhesion having a protective film with few possibility of contaminating the periphery of the magnet. SOLUTION: A method of manufacturing a magnet has a process for forming a polysilazane film on the surface of a rare-earth element-containing magnet main body, and a process for obtaining a glassy protective film from the polysilazane film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magnet that can be used in rotating equipment.

[0002]

2. Description of the Related Art R-TM-B based magnets containing R (R is one or more rare earth elements including Y), TM (TM is a transition element containing Fe as a main component) and boron have excellent magnetic characteristics. Known to have. However, this R-
The TM-B based magnet has a great drawback that it is easily corroded as compared with general steel materials. Therefore, in order to compensate for this drawback, various surface treatments such as plating, ion plating, and resin coating have been performed on the surface of the magnet.

In recent years, along with the miniaturization and energy saving of electric equipment, high-performance magnets are required, and at the same time, cost reduction is also required. In particular, the number of applications that do not require the performance of the conventional surface treatment is increasing, and the cost reduction of the surface treatment is strongly demanded. Further, in order to realize high efficiency of various motor devices, loss of magnetic characteristics due to a protective coating formed by subjecting a magnet to a surface treatment cannot be ignored. In particular, in an environment where energy saving of an air conditioner or the like is required and the motor itself is not affected by moisture, the moisture resistance performance conventionally required is not required. Therefore, in recent years, a small-sized, high-characteristic, inexpensive rare-earth magnet has been demanded in place of the ferrite magnet.

In order to satisfy such requirements, conventionally, as a simple rust preventive treatment method for R-TM-B magnets,
Methods such as chemical conversion treatment and immersion in alkali silicate have been proposed.

The chemical conversion treatment is roughly classified into a chromic acid treatment and a phosphate treatment, but the chromic acid treatment tends to be abolished in view of recent environmental problems.

In Japanese Examined Patent Publication No. 4-22008, RT
There is disclosed a method of forming a chemical conversion coating film composed of a phosphate on the surface of the magnet by treating the surface of the MB magnet with a phosphate. However, conventional phosphatization
When the -TM-B magnet is used, the R-rich phase is selectively eluted due to galvanic corrosion in the magnet structure and a chemical conversion film is not sufficiently formed, so that it has a drawback that required corrosion resistance cannot be obtained.

Japanese Unexamined Patent Publication No. 9-7867 and Japanese Unexamined Patent Publication No. 10-
Japanese Patent No. 154611 discloses a method of forming a glassy protective coating on the surface of a magnet by treating an R-TM-B based magnet with an aqueous alkali silicate solution and heating and drying.

However, the magnets obtained by the methods described in these publications show good corrosion resistance in a humidity resistant environment, but their glass-like protective coating contains a large amount of alkali components.
Since the alkaline component contained in this coating has a property of absorbing moisture, the corrosion resistance of the coating is likely to decrease. Further, the coating film containing an alkaline component also has a property of being redissolved when it comes into contact with moisture. If the coating film elutes, the adhesive strength of the coating film may decrease, and when incorporated into various devices, the periphery of the magnet may be contaminated. Further, in the alkali silicate treatment, when used as a compressor part of a refrigeration equipment, an alkaline component such as Na promotes the decomposition of the refrigerant and the lubricating oil. In particular, when the refrigerant is decomposed, hydrogen halide may be generated to corrode the magnet. Corrosion of the magnet causes loss of magnetic properties and contamination of the environment, which is not preferable.

On the other hand, as a method for obtaining a glassy protective coating without performing chemical conversion treatment or alkali silicate treatment,
A dry method such as CVD or a sol-gel method is known. However, in the dry method and the sol-gel method, it is difficult to obtain an inexpensive and high-performance coating due to the problems that the equipment used is expensive and the processing temperature is high.

Further, a method of polymerizing alkoxysilane to obtain a glass-like protective coating is also conceivable. However,
In this method, since an inorganic acid such as hydrochloric acid is used as a catalyst, there is a problem that sufficient corrosion resistance is not imparted to the obtained coating film.

Incidentally, Japanese Patent Laid-Open No. 2000-34503,
JP-A-7-326508 and JP-A-11-13
Japanese Patent No. 5313 discloses a method for producing a magnet by using a fine powder in which a polysilazane hardened film is formed on the surface of particles of various alloy fine powders, but these methods suppress the oxidation of the powder, It does not exhibit the rust prevention effect.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to manufacture a magnet having a protective film with less loss of magnetic properties, excellent corrosion resistance and adhesiveness, and less risk of contaminating the periphery of the magnet at low cost. Is to provide a method.

[0013]

In order to achieve the above object, a method of manufacturing a magnet according to the present invention comprises a step of forming a polysilazane coating on the surface of a magnet body containing a rare earth element,
And a step of obtaining a glassy protective film from the polysilazane film.

The method for forming the polysilazane coating is not particularly limited, and the magnet body may be formed by immersing it in a polysilazane solution, or may be formed by coating the magnet body with a polysilazane solution.

The method for obtaining the glassy protective coating is not particularly limited, but it is preferable to form the polysilazane coating by heat treatment after formation. The heat treatment temperature is preferably 50 to 500 ° C. The heat treatment atmosphere is preferably a high humidity atmosphere, more preferably 70% RH or more.

The thickness of the polysilazane film formed on the surface of the magnet body is not particularly limited, but it is preferably 0.01 to 5 μm in terms of quality and magnetic properties.

The polysilazane used in the present invention preferably contains perhydropolysilazane. The polysilazane preferably has a number average molecular weight (Mn) of 600 to 20,000. The polysilazane solution is 0.5 to 200
It preferably has a viscosity of cps.

The material of the magnet body used in the present invention is not particularly limited as long as it is composed of a rare earth element, but R (R is one or more rare earth elements including Y), TM
(TM is a transition element containing Fe as a main component) and an R-TM-B rare earth magnet containing boron are preferably used.

[0019]

In the method of manufacturing a magnet according to the present invention, after forming a polysilazane coating on the surface of a magnet body containing a rare earth element, the polysilazane coating is converted by, for example, oxidation in the air or hydrolysis with water vapor. A glassy protective coating (amorphous SiO ₂ ) is obtained.

According to the present invention, the glassy protective coating can be formed on the surface of the magnet body by a simple treatment such as dipping and drying. Therefore, the magnet can be obtained at low cost. The glass-like protective coating formed on the surface of the magnet body is extremely thin. Therefore, the volume fraction of the magnet body in the magnet can be increased. As a result, the loss of magnetic properties is effectively suppressed. Further, the glass-like protective film is stable although it is extremely thin. Therefore, corrosion resistance is imparted to the obtained magnet. Moreover, the stabilized glass-like protective film does not redissolve thereafter, and the adhesive strength of the film can be maintained. Further, the glass-like protective film also has excellent solvent resistance. For this reason, even if the magnet is incorporated into a motor for a refrigerating machine or the like, the coating film is not affected by the refrigerant or the lubricating oil (refrigerating machine oil). As a result, there is no contamination around the magnet.

That is, according to the present invention, it is possible to inexpensively manufacture a magnet having a protective coating that causes little loss of magnetic properties, is excellent in corrosion resistance and adhesiveness, and is less likely to contaminate the periphery of the magnet.

The specific application of the magnet obtained by the present invention is not particularly limited, but various industrial rotary devices, consumer rotary devices, optical pickup devices, etc. are exemplified. Examples of industrial rotating equipment include various motors used in automobiles and motorcycles; drive systems for machine tools.
As consumer rotary equipment, VTR, CD, MD, DV
Various motors used for D, cassette stereo, etc .; O
Examples include motors and the like of equipment A (computer, printer, copier, etc.). The optical pickup device is for recording / reproducing information on / from an optical disc, which is a recording medium, and generally, an objective lens driving device for moving an objective lens in a tracking direction or a focus direction of the optical disc, a light source or a light receiving device on a mounting base. And an optical system block for projecting laser light onto the optical disc through the objective lens and detecting the reflected light.
When the magnet of the present invention is used in an optical pickup device, the magnet is used in a magnetic circuit that is a constituent member of an objective lens driving device.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION In the present embodiment, as an example of a rare earth magnet, an R-TM-B based sintered magnet will be cited, and an example of a method for manufacturing this magnet will be described.

(1) First, the magnet body is prepared. In this embodiment, the magnet body is an R-TM-B-based rare earth magnet containing R (R is one or more rare earth elements containing Y), TM (TM is a transition element containing Fe as a main component), and B. Composed.

The contents of R, TM and B are 5.5 at% ≦ R ≦ 30 at%, 42 at% ≦ TM ≦ 90 at%,
It is preferable that 2 atomic% ≦ B ≦ 28 atomic%. Note that TM is basically composed of Fe and inevitable impurities.
In particular, when the permanent magnet body is manufactured by the sintering method, the following composition is preferable.

As the rare earth element R, Nd, Pr, H
at least one of o and Tb, or further L
a, Sm, Ce, Gd, Er, Eu, Pm, Tm, D
Those containing at least one of y, Yb and Y are preferable. When two or more elements are used as R, a mixture of misch metal or the like can be used as a raw material.

The content of R is preferably 5.5 to 30 atom%. If the content of R is too small, the crystal structure of the magnet will be a cubic crystal structure having the same structure as α-iron, so a high coercive force (Hcj) cannot be obtained, and if it is too large, an R-rich non-magnetic phase will form. And the residual magnetic flux density (Br) decreases.

The TM content is preferably 42 to 90 atom%. If the TM content is too low, Br decreases, and if it is too high, Hcj decreases. By replacing a part of Fe with Co, the temperature characteristics can be improved without impairing the magnetic characteristics. In this case, if the Co substitution amount exceeds 50% of Fe, the magnetic characteristics deteriorate, so the Co substitution amount is preferably 50% or less.

The content of B is preferably 2 to 28 atom%. If the B content is too low, the crystal structure of the magnet will be a rhombohedral structure, and thus Hcj will be insufficient. If the B content is too high, the B-rich nonmagnetic phase will increase, and Br will decrease.

In addition to R, TM and B, Ca, O, C and the like may be contained as inevitable impurities in an amount of 3 atomic% or less of the whole.

Further, by substituting a part of B with at least one of C, P and S, it is possible to realize improvement in productivity and cost reduction. In this case, the substitution amount is preferably 4 atom% or less of the whole. Also, improvement of coercive force,
Cu, Al, T to improve productivity and reduce cost
i, V, Cr, Mn, Bi, Nb, Ta, Mo, W, S
You may add 1 or more types, such as b, Ge, Sn, Zr, Ni, Si, Hf. In this case, the total addition amount is preferably 10 atomic% or less.

The magnet body has a main phase having a substantially tetragonal crystal structure. The particle size of the main phase is preferably about 1 to 100 μm. And, usually, the volume ratio is 1 to
It contains a non-magnetic phase of 50%.

To manufacture such a magnet body, it is preferable to use the powder metallurgy method. The magnet body is manufactured by the powder metallurgy method as follows. First, an alloy having a desired composition is manufactured by using various alloy manufacturing processes such as a casting method and a strip casting method. Then, the obtained alloy is coarsely crushed to a particle size of about 10 to 100 μm using a coarse crusher such as a jaw crusher, a brown mill and a stamp mill, and then finely crushed with a fine crusher such as a jet mill and an attritor. Finely pulverize to a particle size of about 5 to 5 μm. Then, the obtained powder is molded, preferably in a magnetic field. The magnetic field strength during molding is preferably 600 kA
/ M or more. Molding pressure is preferably 0.5 to 5 t
It is about on / cm ² . Then, the obtained molded body is sintered at 1000 to 1200 ° C. for 0.5 to 10 hours and rapidly cooled. The atmosphere during sintering is preferably in an inert gas such as Ar gas or in vacuum. After this, preferably in an inert gas atmosphere or in a vacuum, 500-
Heat treatment (aging treatment) at 900 ° C for 1 to 5 hours,
Process into any shape. The magnet body manufactured in this way is particularly excellent in magnetic characteristics when R is Nd, for example.

(2) Next, in this embodiment, the obtained magnet body is subjected to pretreatment such as cleaning.

This pretreatment is an optional treatment in the present invention, but by performing this pretreatment, the corrosion resistance of the coating can be further improved. However, not performing the pretreatment does not significantly impair the coating performance.

When carrying out the pretreatment, it is preferable to apply the following process.

First, barrel polishing is performed to remove burrs and the like on the surface of the magnet body. Next, a degreasing process is performed to remove dirt on the surface of the magnet body, and after cleaning, ultrasonic cleaning is performed in ion-exchanged water. The degreasing liquid used in the degreasing treatment is not particularly limited as long as it is used for ordinary steel. It is more preferable to use an alkaline degreasing liquid because it has a large cleaning effect, and it is more preferable to use an alkaline degreasing liquid that contains a chelating agent in the components because it has the effect of slightly etching the magnet surface. As a component of the degreasing liquid, generally caustic soda (NaOH) is the main component, and other additives are not specified.

When the surface of the magnet body after degreasing is further cleaned, chemical etching may be performed. Nitric acid is preferably used as the acid used in the chemical etching. When plating general steel materials, non-oxidizing acids such as hydrochloric acid and sulfuric acid are often used. But,
When the magnet body contains a rare earth element like the magnet body in the present embodiment, if treatment is performed using these acids,
Hydrogen generated by the acid is occluded on the surface of the magnet body, and the occluded site becomes brittle and a large amount of powdery undissolved material is generated. Since this powdery undissolved substance causes surface roughness, defects and poor adhesion after surface treatment, it is preferable not to include the above-mentioned non-oxidizing acid in the chemical etching treatment liquid. Therefore, it is preferable to use nitric acid, which is an oxidizing acid that generates less hydrogen.

The amount of dissolution of the surface of the magnet body by such pretreatment is preferably 5 μm or more, and preferably 10 to 15 μm in average thickness from the surface. By completely removing the altered layer and oxide layer due to the processing of the surface of the magnet body,
It is possible to reduce the starting point of corrosion on the magnet surface and further improve the corrosion resistance.

The nitric acid concentration of the treatment liquid used for the pretreatment is
It is preferably 1 normal or less, and particularly preferably 0.5 normal or less. If the nitric acid concentration is too high, the rate of dissolution of the magnet body is extremely high, and it becomes difficult to control the amount of dissolution. In particular, in large-scale processing such as barrel processing, variations become large, and the dimensional accuracy of the product cannot be maintained. Further, if the nitric acid concentration is too low, the amount of dissolution will be insufficient. For this reason, it is desirable that the nitric acid concentration be 1 normal or lower, particularly 0.5 to 0.05 normal or lower. The amount of Fe dissolved at the end of the treatment is 1 to 10 g /
It is about l.

In order to completely remove a small amount of undissolved substances and residual acid components from the surface of the magnet body which has been pretreated, it is preferable to carry out cleaning using ultrasonic waves. This ultrasonic cleaning is preferably carried out in pure water containing very few chlorine ions that cause rust on the surface of the magnet body. Further, similar water washing may be performed before and after the ultrasonic cleaning and in each step of the pretreatment, if necessary.

(3) Next, the surface of the pretreated magnet body is treated with a polysilazane solution to form a polysilazane coating on the surface of the magnet body.

In this embodiment, a method of immersing the magnet body in a polysilazane solution and drying it to form a polysilazane coating on the surface of the magnet body is adopted, but the present invention is not limited to this.

The polysilazane that can be used in the present invention may be any polysilazane having at least a Si--H bond or an N--H bond in the molecule, and may be polysilazane alone, or a polysilazane and another polymer. It may be a copolymer or a mixture of polysilazane and another compound.

The polysilazanes that can be used in the present invention include those having a chain structure, a cyclic structure or a crosslinked structure, or those having a plurality of these structures simultaneously in the molecule, and these may be used alone or It can also be used as a mixture.

Examples of polysilazanes usable in the present invention include those having a repeating unit represented by the following formula (1).

[0047]

[Chemical 1]

Here, in the formula (1), R ¹ , R ² and R ³ are each independently a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, or other than these groups, directly bonded to silicon. Represents a group having a carbon atom, an alkylsilyl group, an alkylamino group or an alkoxy group. Provided that at least one of R ¹ , R ² and R ³
One is a hydrogen atom.

Among these, R ¹ in the above formula (1),
Perhydropolysilazane (PHPS) in which all of R ² and R ³ are hydrogen atoms is preferable. This perhydropolysilazane can be produced, for example, by the method described in JP-B-63-16325.
One structural example of perhydropolysilazane is shown in the following formula (2).

[0050]

[Chemical 2]

The polysilazane usable in the present invention preferably has a number average molecular weight (Mn) of 600 to 20,000, more preferably 600 to 200.
It is 0. If the molecular weight is too small, the coating film is not sufficiently formed and the reactivity is high, so the bath life may be significantly shortened. On the contrary, if the molecular weight is too large, the reactivity is poor,
This may cause a disadvantage that the film becomes thick easily.

The polysilazane usable in the present invention is dissolved in a suitable solvent and used as a polysilazane solution. Examples of the solvent include aliphatic hydrocarbons, alicyclic hydrocarbons, hydrocarbon solvents of aromatic hydrocarbons, halogenated hydrocarbons such as halogenated methane, halogenated ethane, and halogenated benzenes, aliphatic ethers, alicyclics. Examples include ethers such as formula ether. These solvents are used to control the solubility of polysilazane and the evaporation rate of the solvent.
Two or more types can be mixed and used. Among them, preferred solvents are halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, bromoform, ethylene chloride, ethylidene chloride, trichloroethane and tetrachloroethane; ethyl ether, isopropyl ether, ethyl butyl ether, butyl ether, 1,2-dioxyethane. , Ethers such as dioxane, dimethyldioxane, tetrahydrofuran, tetrahydropyran; pentanehexane, isohexane, methylpentane, heptane, isoheptane, octane, isooctane, cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, ethylbenzene. Hydrocarbons such as;

It is also preferable to add a metal-based or organic-based catalyst to the polysilazane solution in order to promote the formation of a glass-like protective film described later. Examples of the metal-based catalyst include Pt, Pd, Au, Ag, Ni, and the like, and one or more kinds can be used. Of these, Pt and Pd are preferable. As the organic catalyst, for example, amines are preferable, and pyridine and its derivatives, 1,8-diazabicyclo [5.4.0] -7-undecene (DBU), 1,5-diazabicyclo [4.3.
0] -5-nonene (DBN) and the like, and one kind or two or more kinds can be used. Above all, DBU, DBN
Is preferred. The addition amount of the catalyst to the polysilazane solution is preferably 0.01 to 0.1 part by weight, more preferably 0.05 to 0.1 part by weight with respect to 100 parts by weight of polysilazane.
It is about 0.1 part by weight. If necessary, various additives such as various pigments, leveling agents, defoaming agents, antistatic agents, pH adjusters, dispersants, surface modifiers, plasticizers, drying accelerators, anti-flow agents, etc. are added to the polysilazane solution. The agent may be further added. The addition amount in this case may be appropriately determined within a range that does not impair the object of the present invention.

The polysilazane solution used in the present invention is
The viscosity (η) is adjusted to preferably 0.1 to 200 cps, more preferably 0.6 to 50 cps.
When the viscosity of the solution is too low, the film is not sufficiently formed.
On the other hand, if the viscosity is too high, a large number of gas pinholes are generated in the coating film due to the evaporation of the solvent. In this embodiment, the magnet body is dipped in a polysilazane solution and dried to form a polysilazane coating on the surface of the magnet body. The polysilazane solution may be dried to such an extent that the solvent component on the coating surface is removed, and may be left at room temperature. However,
In order to improve workability, it is preferably 50 to 200 ° C.
Drying may be performed at a temperature of about 1 to 120 minutes. The drying method is not particularly limited, and may be a method of blowing air. If necessary,
The immersion in the polysilazane solution and the drying treatment may be performed twice or more. The thickness of the polysilazane coating formed on the surface of the magnet body is preferably 0.01 to 5 μm, more preferably 0.05 to 3 μm. If the thickness of the coating film formed is too thin, it is difficult to obtain sufficient corrosion resistance. On the other hand, if the coating is too thick, it will be difficult to obtain a uniform thickness, and the loss of magnetic properties will increase. That is, it is preferable to form the film within the above range from the viewpoint of minimizing the loss of magnetic properties as much as possible and obtaining a uniform film thickness while sufficiently maintaining the corrosion resistance.

In the present invention, the polysilazane film (for example, perhydropolysilazane film) formed on the surface of the magnet body is converted into the glass-like protective film by the reaction mechanism of the following formulas (3) to (4). _{(-SiH 2 -NH -) + O} 2 → SiO 2 + NH 3 ... (3) (-SiH 2 -NH -) + 2H 2 O → SiO 2 + NH 3 + 2H 2 ... (4)

In the present invention, the polysilazane coating can be converted into the glass-like protective coating even if it is left at room temperature, but after drying, if necessary, heat treatment may be carried out to accelerate the formation of the glass-like protective coating. preferable. The heat treatment temperature is preferably 50 to 500 ° C., more preferably 150 to 450.
℃. If the heat treatment temperature is too low, there is not much difference from that at room temperature, and the conversion time to the glass-like protective coating may take a long time. On the other hand, if the heat treatment temperature is too high, the magnetic properties deteriorate. By exposing the polysilazane film to a high humidity atmosphere, it is possible to hydrolyze the film and convert it into a glassy protective film. in this case,
The heat treatment temperature is preferably 50 to 200 ° C, more preferably 50 to 100 ° C, and the humidity is preferably 70%.
RH or more, more preferably 80% RH or more. Through the steps described above, a permanent magnet having a stabilized protective coating formed on the surface of the magnet body is manufactured.

In this embodiment, the polysilazane coating formed on the surface of the R-TM-B system sintered magnet body is converted to form a stabilized glass-like protective coating. Since a glassy protective film can be formed by simple treatment such as immersion and drying,
A magnet having such a coating can be obtained at low cost. Since the formed glass-like protective coating is extremely thin, the volume fraction of the magnet body in the magnet can be increased, and the loss of magnetic properties can be effectively suppressed. In addition, the glass-like protective coating is stable even though it is extremely thin, so that the obtained magnet is provided with corrosion resistance and
The stabilized glassy protective coating does not subsequently redissolve and the adhesive strength of the coating can be maintained. Further, since the glassy protective coating has excellent solvent resistance, even if the magnet is incorporated into a motor for refrigeration equipment or the like, the coating is not attacked by the refrigerant, and the periphery of the magnet is not contaminated.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and may be implemented in various modes without departing from the scope of the present invention. Of course.

[0059]

EXAMPLES The embodiments of the present invention will be specifically described below with reference to examples and comparative examples. The present invention is not limited to these.

Example 1 14.7Nd-77.6 prepared by powder metallurgy
An ingot having a composition of Fe-1.6Co-6.1B (numbers are atomic ratios) was roughly pulverized, and further jet mill pulverized with an inert gas to obtain fine powder having an average particle diameter of about 3.5 μm.
The obtained fine powder was filled in a mold, and a magnetic field of 1185 kA / m was applied to mold at a pressure of 1.0 ton / cm ² . Next, a sintered body was obtained through sintering and heat treatment in vacuum. The obtained sintered body is 10 mm × 20 mm × thickness 3 m
It was cut into a size of m and further barrel-polished and alkali-degreased to obtain a permanent magnet body.

Next, polysilazane (Mn≈1000)
Polysilazane solution prepared by diluting xylene with xylene (product number L110 manufactured by Tonensha Co., Ltd., viscosity: 0.6 cps :)
Immerse the obtained permanent magnet body once in room temperature (2
The polysilazane film was formed on the surface of the permanent magnet body by drying at 5 ° C. for 30 minutes. The film thickness of the polysilazane film was 0.3 μm. Then, the polysilazane coating was converted into a glass-like protective coating by heat treatment at 300 ° C. for 60 minutes. Thereby, a permanent magnet sample was obtained. The film thickness of the converted glassy protective coating was 0.3 μm.

Example 2 The same as Example 1 except that a polysilazane film having a thickness of 0.5 μm was formed on the surface of the permanent magnet body using a polysilazane solution whose viscosity was adjusted to 1 cps by changing the amount of dilution with xylene. Then, the polysilazane film was converted into a glassy protective film to obtain a permanent magnet sample. The film thickness of the converted glassy protective coating was 0.5 μm.

Example 3 Example 1 was repeated except that a polysilazane film having a thickness of 2 μm was formed on the surface of the permanent magnet body by using a polysilazane solution whose viscosity was adjusted to 10 cps by changing the amount of dilution with xylene.
The polysilazane film was converted into a glassy protective film in the same manner as in 1. to obtain a permanent magnet sample. The film thickness of the converted glassy protective coating was 2 μm.

Example 4 A polysilazane solution prepared by changing the amount of dilution with xylene to have a viscosity of 1 cps was used, except that the number of immersions was 5 and a polysilazane film having a thickness of 2 μm was formed on the surface of the permanent magnet body. In the same manner as in Example 1, the polysilazane coating was converted into a glassy protective coating to obtain a permanent magnet sample. The film thickness of the converted glassy protective coating was 2 μm.

Example 5 A permanent magnet sample was obtained by converting the polysilazane film into a glassy protective film in the same manner as in Example 2 except that the heat treatment condition of the polysilazane film was 450 ° C. for 60 minutes. The film thickness of the converted glassy protective coating was 0.5 μm.

Example 6 A permanent magnet sample was obtained by converting the polysilazane film into a glassy protective film in the same manner as in Example 2 except that the heat treatment condition of the polysilazane film was 200 ° C. for 300 minutes. The film thickness of the converted glassy protective coating was 0.5 μm.

Comparative Example 1 Instead of immersing the obtained permanent magnet body in the polysilazane solution, the surface of the permanent magnet body was plated with nickel.
A nickel coating having a film thickness of 1 μm was formed to obtain a permanent magnet sample.

Comparative Example 2 A permanent magnet sample was obtained in the same manner as in Comparative Example 1 except that a nickel coating having a film thickness of 5 μm was formed.

Comparative Example 3 An epoxy resin solution prepared by diluting an epoxy resin with methyl ethyl ketone was used in place of the polysilazane solution, and the obtained permanent magnet body was immersed once in the epoxy resin solution at room temperature (25 An epoxy resin coating was formed on the surface of the permanent magnet body by drying at 10 ° C.) for 10 minutes. After that, by heat treatment at 150 ° C for 30 minutes,
A cured coating was produced to obtain a permanent magnet sample. The film thickness of the cured film was 4 μm.

Comparative Example 4 An epoxy resin solution prepared by diluting an epoxy resin with methyl ethyl ketone was used in place of the polysilazane solution, and this epoxy resin solution had a cured film with a thickness of 9 μm.
A permanent magnet sample was obtained in the same manner as in Comparative Example 3 except that the permanent magnet body was immersed once so that

Comparative Example 5 A sodium silicate aqueous solution having a weight ratio of 20% (molar ratio n = (was prepared by dissolving JIS-3 sodium silicate (manufactured by Asahi Denka Co., Ltd.) in pure water instead of the polysilazane solution. S
iO ₂ / Na ₂ O) = 3) was used. Immerse the obtained permanent magnet body once in this sodium silicate aqueous solution,
By leaving at room temperature (25 ° C) for 30 minutes to dry,
A sodium silicate coating having a film thickness of 1 μm was formed on the surface of the permanent magnet body. Then, immersion in pure water prepared at 50 ° C. was performed for 10 minutes, and drying was performed at 100 ° C. for 20 minutes to convert the sodium silicate film into a silicic acid protective film.
A permanent magnet sample was obtained in the same manner as in Example 1 except for these. The thickness of the generated silicic acid protective film was 1 μm.

Comparative Example 6 A permanent magnet sample was obtained in the same manner as in Comparative Example 5 except that the number of immersions in the sodium silicate aqueous solution was changed to 3.
The thickness of the generated silicic acid protective film was 3 μm.

Comparative Example 7 A permanent magnet sample was obtained in the same manner as in Comparative Example 5 except that the number of immersions in the aqueous sodium silicate solution was changed to 5.
The thickness of the generated silicic acid protective film was 5 μm.

The permanent magnet samples obtained in Examples 1 to 6 and Comparative Examples 1 to 7 were used to evaluate the humidity resistance (corrosion resistance), solvent resistance (contamination resistance), and magnetic properties. . The film thicknesses described above were measured with a micrometer.

The "moisture resistance" was measured by using a permanent magnet sample of 85
It was carried out by observing the change in appearance after the test piece was placed in a 85% RH test tank at 300C for 300 hours. And "no change"
The case was evaluated as having corrosion resistance, and the case where "rust occurred" was evaluated as having no corrosion resistance. The "solvent resistance" was performed by immersing the permanent magnet sample in each solvent of toluene and methylene chloride, and observing the appearance change after standing at room temperature (25 ° C) for 1 week. Then, the case of "no change" was evaluated as having solvent resistance, and the case of "part of the coating film was peeled off and discolored" was evaluated as having no solvent resistance.

The "magnetic characteristic" was determined by measuring the magnetic flux of the permanent magnet sample with a flux meter and determining the difference in the surface magnetic flux before and after the test as the demagnetization rate. When the demagnetization rate is "1% or less", it is ○ (good), when it is "1% or more and less than 5%", it is △ (somewhat bad), and when it is "5% or more", it is ×
Each was evaluated as (poor).

The results are shown in Table 1.

[0078]

[Table 1]

As shown in Table 1, the magnet samples of Examples 1 to 6 having the glassy protective coating obtained from the polysilazane coating formed by the dipping treatment with the polysilazane solution were the same as those of Comparative Examples 1 to 7. By comparison, it was confirmed that all of the moisture resistance (corrosion resistance), the solvent resistance and the magnetic properties were excellent.

[0080]

As described above, according to the present invention, there is little loss of magnetic properties, excellent corrosion resistance and adhesiveness,
It is possible to provide a method for manufacturing a magnet that can inexpensively manufacture a magnet having a protective coating that is less likely to contaminate the periphery of the magnet.

Continued front page    (72) Inventor Goichi Nishizawa             1-13-1, Nihonbashi, Chuo-ku, Tokyo             -In DC Inc. (72) Inventor Riki Ishizaka             1-13-1, Nihonbashi, Chuo-ku, Tokyo             -In DC Inc. F-term (reference) 4K022 AA02 AA37 AA44 BA15 BA20                       BA33 DA06 DA09 EA01                 5E062 CD04 CG03 CG07

Claims (10)

[Claims] 1. A method of manufacturing a magnet, comprising: a step of forming a polysilazane coating on the surface of a magnet body containing a rare earth element; and a step of obtaining a glassy protective coating from the polysilazane coating. 2. The method for producing a magnet according to claim 1, wherein the magnet body is dipped in a polysilazane solution, or the magnet body is coated with a polysilazane solution to form the polysilazane coating. 3. The method for producing a magnet according to claim 1, wherein the polysilazane coating is heat-treated to obtain the glassy protective coating. 4. The method for producing a magnet according to claim 3, wherein the temperature of the heat treatment is 50 to 500 ° C. 5. The method for producing a magnet according to claim 3, wherein the heat treatment atmosphere is an atmosphere of 70% RH or more. 6. The polysilazane film having a thickness of 0.01 to 5 μm is formed on the surface of the magnet body.
The method for producing a magnet according to any one of 1. 7. The method for producing a magnet according to claim 1, wherein the polysilazane contains perhydropolysilazane. 8. The polysilazane is 600 to 2000.
The method for producing a magnet according to claim 1, having a number average molecular weight (Mn) of 0. 9. The polysilazane solution is 0.5 to 20.
The method for producing a magnet according to claim 1, which has a viscosity of 0 cps. 10. The R-TM-B based rare earth magnet, wherein the magnet body contains R (R is one or more rare earth elements containing Y), TM (TM is a transition element containing Fe as a main component) and boron. The method for manufacturing a magnet according to any one of claims 1 to 9, which is configured.