DE69918915T2 - Method for producing a R-Fe-B-based permanent magnet with a corrosion-resistant layer - Google Patents

Description

Territory of invention

The The present invention relates to a method of manufacturing a Fe-B-R based permanent magnet with excellent corrosion resistance Movie. More specifically, the present invention relates to a method for producing a Fe-B-R based permanent magnet, which one on its surface excellent corrosion resistant film with excellent adhesion on the surface having the magnet formed easily and at a low cost can be without a plating treatment and a treatment using hexavalent chromium, and a stable one show high magnetic characteristics that are not affected even if the magnet is under high temperature and high humidity conditions a temperature of 80 ° C and a relative humidity of 90% is allowed to stand.

description related art

One Fe-B-R-based permanent magnet, for the one Fe-B-Nd-based Permanent magnet representative is used in practice in various applications, because he is made of a cheap material, rich in natural Resources, is produced and high magnetic characteristics having.

however For example, an Fe-B-R based permanent magnet is susceptible to oxidation by oxidation the atmosphere to corrode because it contains highly reactive R and Fe. If the Fe-B-R based permanent magnet is used without any treatment to have been subjected to corrosion of the magnet due to the presence of a small amount of acid, base and / or water away from its surface to create rust, resulting in degradation and dispersion of the magnetic properties. Further, when the magnet with rust generated therein is in a device, such as a magnetic circuit is installed, there is the Possibility, that the rust spreads, and so surrounding parts or components dirty.

There is already a proposed magnet having a corrosion-resistant metal-clad film on its surface formed by a wet-plating process such as an electroless plating method and an electroplating method to improve the corrosion resistance of the Fe-BR-based permanent magnet in view of the above Point to improve (see Japanese Patent Publication No. 3-74012). However, in this method, an acidic or alkaline solution used in the pretreatment prior to the plating treatment may remain in the pores of the magnet, whereby the magnet may in some cases corrode with the passage of time. In the EP 0 502 475 A2 For example, a method is described in which the surface of a bonded magnet is treated with a nickel solution in the presence of an organic acid salt to produce a nickel protective surface layer. In addition, the magnet is poor in resistance to chemicals, and for this reason, the surface of the magnet may be corroded during the plating treatment. Further, even if the metal-plated film is formed on the surface of the magnet as described above, if the magnet is subjected to a corrosion test under conditions of a temperature of 60 ° C and a relative humidity of 90%, the magnetic property of the magnet may be lowered Elapse of 100 hours by 10% or more from the initial value.

It also provides a conventionally proposed method a corrosion resistant film such as a phosphate film or a chromate film, on the surface is formed of a Fe-B-R-based permanent magnet (see Japanese Patent publication No. 4-22008). Of the film formed in this process is with respect to its adhesion to the surface However, if it does a corrosion test it can under conditions of a temperature of 60 ° C and a relative humidity of 90%, the magnetic property of the magnet after elapse of 300 hours by 10% or more compared to Output value are reduced.

In a conventionally proposed method for improving the corrosion resistance of the Fe-BR-based permanent magnet, that is, in a so-called aluminum chromate treatment method (see Japanese Patent Publication No. 6-66173), a chromate treatment is performed after forming an aluminum film by a vapor deposition method. This process considerably improves the corrosion resistance of the magnet. However, the chromate treatment used in this method employs hexavalent chromium, which is undesirable to the environment, and for this reason, a waste liquid treating method is complicated. It is feared that a film formed by this process will affect the human body during handling of the magnet because it will produce a small amount of heat contains xavalent chromium.

Another surface treatment is described in the patent summaries of Japan, Vol. 1995, No. 11, 26.12.1995 and JP 072 30 906 A wherein the surface of a Nd-Fe-B alloy magnet is gel-coated with an organic denatured silica film.

on the other hand exists a conventionally proposed method in which a primary Covering layer of a metal used as the main component the surface of a Fe-B-R-based permanent magnet is formed and a glass layer on the surface the primary Covering layer is formed (see Japanese Patent Application Laid-Open Publication No. 1-165105). If the primary Cover layer formed using a wet cladding The magnet may corrode over time as above described. For example, if the primary cover layer by a Vapor deposition method, such as a Vakuumaufdampfverfahren trained it will be possible To provide a magnet that does not have this problem and has excellent corrosion resistance. However, to carry out the Vapor Deposition method requires a large device and about that In addition, this device is expensive. It will be for the surface of the Magnets as a pretreatment a cleaning treatment required and around a lightly oxidized metal, as the main component is used, such as aluminum, tin, zinc and the like primary Forming cover layer, an extremely high degree of vacuum is needed. For this Reason, an evacuation treatment over a long period is required and therefore one can Complication of the manufacturing process and the extension the for the manufacturing process required time can not be avoided.

Summary the invention

Accordingly, it is an object of the present invention, a method for the preparation to provide a Fe-B-R-based permanent magnet based on his surface an excellent corrosion resistant film with an excellent adhesion on the surface of the magnet which is capable of simple and low Costs to be trained without a plating treatment and to perform a treatment using hexavalent chromium, and which can also show a stable high magnetic characteristic, which does not affect even if the magnet is under high temperature and high humidity conditions a temperature of 80 ° C and a relative humidity of 90% is allowed to stand.

The present inventors have various zealous studies in view performed on the above points and have as a result found that if a Fe-B-R based Permanent magnet and pieces of metal a circular or columnar Shape with a length of 0.05 mm to 10 mm can be entered in a treatment tank and in the treatment tank shaken (vibrates) and / or moved, a generated from the piece of metal fine metal powder deposited on the surface of the magnet can be to make a movie; that if a metal oxide film on the metal film is formed by a sol gel process, the Metal oxide film close to the surface of metal film on the magnet adheres to the corrosion resistance to improve the magnet; and that the influence on the human body and the environment considerably reduced by using the sol gel process can be and about it In addition, such a manufacturing process is very simple.

The The present invention is completed based on this knowledge Service. In order to accomplish the above object, according to First aspect and feature of the present invention, a method for producing a permanent magnet with a metal oxide film its surface provided with a metal film interposed therebetween the steps of placing a Fe-B-R based permanent magnet and of metal pieces a circular or columnar Shape with a length of 0.05 mm to 10 mm in a treatment tank, where they are shaken and / or be moved to a metal film on the surface of the To form magnets; Applying to the surface of the metal film of a sol solution by the hydrolytic reaction and the polymerization reaction of a Metal compound is prepared and a starting material for a metal oxide film represents; and subjecting the applied sol solution to a heat treatment, to form this metal oxide film.

According to one second aspect and feature of the present invention, in addition to first feature, the metal piece is used to form this metal film, which is made of at least one metal component made of the group selected is made of aluminum, tin and zinc, form.

According to a third aspect and feature of the present invention, in addition to the first aspect times, the thickness of the metal film is in a range of 0.01 μm to 1 μm.

According to one fourth aspect and feature of the present invention, in addition to first feature, becomes the sol solution used to make this metal oxide film made from at least one metal oxide component is that selected from the group is made of aluminum (Al) oxide, silicon (Si) oxide, zirconium (Zr) oxide and titanium (Ti) oxide consists of forming.

According to one fifth Aspect and feature of the present invention, in addition to first feature, becomes the sol solution used this metal component, which is the same metal component as the metal component of the metal film contains form.

According to one sixth aspect and feature of the present invention, in addition to First feature, the thickness of the metal oxide film is in a range of 0.01 μm up to 10 μm.

According to one seventh aspect and feature of the present invention, in addition to first feature, the content of carbon (C) is in the Metal oxide film is included, in a range of 50 ppm to 1,000 ppm.

According to one eighth aspect and feature of the present invention, in addition to first feature, the metal oxide film is formed of a metal oxide, which essentially comprises an amorphous phase.

With the method according to the present invention Invention it is possible on the surface the magnet to form an excellent corrosion-resistant film, which can be manufactured easily and at low cost without a plating treatment or a treatment using of hexavalent chromium and the excellent adhesion on the surface of the magnet, and the magnet can be a stable high magnetic Show characteristic that can not be degraded, even if the magnet for a long period under high temperature and high humidity conditions of a temperature of 80 ° C and a relative humidity of 90%. Consequently Is it possible, an Fe-B-R based permanent magnet with excellent corrosion resistance provide.

detailed Description of the invention

It Now, a method for forming a metal film on the surface of a magnet that is placing a Fe-B-R based Permanent magnets and metal pieces in a treatment tank includes where they shaken and / or moved.

It may be a metal component corresponding to a desired metal film, Used metal piece become. An example of such a piece of metal is a piece of metal that is made of at least one metal component derived from the Group selected which is aluminum, tin, zinc, copper, iron, nickel, cobalt and titanium exists. Those of these metal compounds, the one Metal film can form efficiently on a sintered magnet are Aluminum, tin and zinc. The metal piece can be made from a single piece Metal component or made of an alloy. On off a film made of a plurality of metal components can be Use of a plurality of metal pieces of different metal components be formed.

With metal pieces various shapes, such as a circular (wire-like) shape, a columnar shape Form and a massive form are used, but from the standpoint the efficient production of a fine metal powder, which is the starting material for forming the metal film, it is essential that a circular or columnar metal piece with a sharp end is used.

from Position of efficient production of a fine metal powder, which is a raw material for forming the metal film, is the length size of the piece of metal in one Range of 0.05 mm to 10 mm, preferably in a range of 0.3 mm to 5 mm, more preferably in a range of 0.5 mm up to 3 mm. metal pieces with the same shape and size can be used and metal pieces with different shapes and different sizes can be found in Combination can be used.

It is desirable that the shaking and / or movement of the magnet and the metal pieces be performed in a dry manner, in view of the magnet and the metal pieces being susceptible to oxidizing and corroding. The shaking and / or the movement of the magnet and The metal pieces can be carried out in the atmosphere and at ambient temperature. The treatment tank used in the present invention does not require a complicated structure and may be, for example, a treatment chamber in a drum apparatus. The drum apparatus is a known device of the rotation type, vibration type or centrifugal type. In the case of the rotation type, it is desirable that the rotation speed be set in a range of 20 rpm to 50 rpm. In the case of the shaking type, it is desirable that the shaking frequency is set in a range of 50 to 100 Hz and the shaking amplitude is set in the range of 3 mm to 10 mm. In the case of the centrifugal type, it is desirable that the number of rotations be set in a range of 70 rpm to 200 rpm.

It is desirable that the amount of magnet and pieces of metal placed in the treatment tank are in a range of 20 vol.% to 90 vol.% of the internal volume of the treatment tank lie. If the amount is less than 20% by volume, it is too small and not of practical use. If the amount exceeds 90% by volume it is possible, That a metal film can not be efficiently formed. The ratio of Magnet to metal pieces is desirable 3 or less as volume ratio (Magnetic / metal pieces). If the volume ratio 3 exceeds it is possible, that needs a lot of time is, and therefore is a 3 overstepping volume ratio not of practical use. The treatment time depends on the amount of treatment and is usually in the range of 1 h to 10 h.

At the The method described above is a fine metal powder consisting of the piece of metal is generated on the surface deposited of the magnet to form a metal film. The phenomenon of Deposit of fine metal powder on the surface of the Magnets are considered to be a special mechanochemical reaction. The fine metal powder is firmly deposited on the surface of the magnet and the formed metal film shows excellent corrosion resistance. From the point of view of ensuring a satisfactory corrosion resistance it is desirable the thickness of the metal film is equal to or greater than 0.01 μm. The upper limit for the film thickness is not particularly limited. However, to form a Metal film with a thickness above 1 micron needs a lot of time and therefore, this method is suitable for forming a metal film with a thickness of 1 micron Or less.

The Adhesion between the surface of the magnet and the metal film can be reinforced thereby that on the surface of the magnet formed by the method described above metal film is subjected to a heat treatment. The heat treatment can executed at this stage be, but a similar one Effect can even by a heat treatment to form a Metal oxide film are provided, which are described hereinafter becomes. It is desirable that the temperature for the Heat treatment equal to or lower than 500 ° C is because of the possibility if the temperature exceeds 500 ° C, it is degraded the magnetic property occurs or the metal film melts.

A Procedure for applying a sol solution, which by the hydrolytic Reaction and Polymerization Reaction of a Metal Compound and which is the starting material for a metal oxide film is, on the surface of the formed metal film and subjecting the applied sol solution to Heat treatment to form a metal oxide film will be described below.

Of the Metal oxide film may be one of a single metal oxide component formed film or one of a plurality of metal oxide components be educated composer movie. The metal oxide component may, for example at least one to be selected from the group consisting of aluminum (Al) oxide, silicon (Si) oxide, Zirconium (Zr) oxide and titanium (Ti) oxide.

Among the films formed of a single metal oxide, the silicon oxide film (SiO _x film: 0 <x ≦ 2) can be formed at a low temperature as compared with a case where a film of another metal oxide component is used because the sol solution is used to form the film Film is stable compared to a sol solution for forming another metal oxide film, and therefore, this silicon oxide film is advantageous in that the influence on the magnetic property of the magnet can be reduced. Zirconia film (ZrO _x film: 0 <x ≦ 2) is advantageous in that it is excellent not only in corrosion resistance but also in alkali resistance.

If the metal oxide film is one which is the same metal component as the metal component of the metal film that is a primary cladding layer (eg, when an aluminum oxide film (Al ₂ O _x film: 0 <x ≦ 3) is formed on an aluminum film), it is Film advantageous in that the adhesion at the interface between the metal film and the metal oxide film is stronger.

Examples of the composite film formed of a plurality of metal oxide components are a Si-Al composite film (SiO _x Al ₂ O _y film: 0 <x ≦ 2 and 0 <y ≦ 3), an Si-Zr composite film (SiO _x ZrO _y film: 0 <x ≦ 2 and 0 <y ≦ 2) and a Si-Ti composite film (SiO _x TiO _y film: 0 <x ≦ 2 and 0 <y ≦ 2). The composite film containing a Si oxide component is advantageous in that the sol solution is relatively stable and such a film can be formed at a relatively low temperature, and therefore the influence on the magnetic characteristic of the magnet can be reduced. A composite film containing a Zr oxide component is advantageous in that it is excellent in alkali resistance.

If the metal oxide film has the same metal component as the metal component of the metal film as primary Cover film containing composite film is (e.g., when a Si-Al composite oxide film is formed on an aluminum film or when a Si-Ti composite oxide film formed on a titanium film), this composite film is advantageous in terms of that adhesion at the interface between the metal film and the composite film is firmer.

The Sol solution used in the sol gel method is a by dissecting a metal compound which is a source for forming a metal oxide film, a catalyst, a stabilizer and water is in one organic solvents prepared solution, around a colloid through the hydrolytic reaction and polymerization reaction so that the colloid is dispersed in the solution.

Examples for the Metal compound as the source for forming the metal oxide film, which can be used are a metal alkoxide (which is an alkoxide having at least one alkoxyl group which may be substituted with an alkyl group such as methyl group and Ethyl group or substituted with a phenyl group or the like), such as methoxide, ethoxide, propoxide, butoxide; a metal carboxylate, such as oxalate, acetate, octylate and stearate; a chelate compound, such as metal acetylacetonate; and inorganic salts, such as Metal nitrate and chloride.

If the stability and costs of the solution considered it is in cases an aluminum compound used to form an aluminum oxide film and a zirconium compound used to form a zirconium oxide film desirable, an alkoxide having an alkoxyl group containing 3 to 4 carbon atoms contains such as aluminum and zirconium propoxides and butoxides, a carboxylate, such as metal acetate and octylate. In case of a Silicon (Si) compound used to form a silicon oxide film is used, it is desirable to use an alkoxide with an alkoxyl group containing 1 to 3 carbon atoms contains such as silicon methoxide, ethoxide and -propoxide. In case of a titanium (Ti) compound used to form a Ti oxide film it is desirable to use an alkoxide having an alkoxyl group, the 2 contains up to 4 carbon atoms, such as titanium ethoxide, propoxide and butoxide.

In order to form a composite oxide film, a plurality of metal compounds in the form of a mixture thereof may be used, and a metal composite compound such as a metal composite oxide may be used alone or in combination with a metal compound. For example, to form a Si-Al composite oxide film, an Si-Al composite compound such as a Si-Al composite oxide having a Si-O-Al bond and alkoxyl groups (some of which have an alkyl group such as methyl group and Ethyl group or substituted with a phenyl group or the like) containing 1 to 4 carbon atoms. Specific examples of such compounds are (H ₃ CO) ₃ -Si-O-Al- (OCH ₃ ) ₂ and (H ₅ C ₂ O) ₃ -Si-O-Al- (OC ₂ H ₅ ) ₂ .

If a composite oxide film using a plurality of metal compounds is to be formed, is the mixing ratio of each metal compound not particularly limited and can according to the circumstances of components for the wished Composite oxide film are set.

For example, when an Si-Al composite oxide film is to be formed on an aluminum (Al) film, it is desirable that a Si compound and an Al compound be mixed in use, or a Si compound and a Si-Al composite compound for use, the molar ratio (Al / Si + Al) of aluminum to the total number of moles of silicon (Si) and aluminum (Al) contained in the Si-Al composite oxide film is equal to or greater than 0.001. By mixing such compounds in the above-described molar ratio, the reactivity at the interface to the aluminum film can be increased while excellent properties (the sol solution is stable and the film can be formed at a relatively low temperature) are obtained in the silicon oxide film. When a heat treatment (to be described later) is carried out at 150 ° C or lower after application of the sol solution to the surface of the metal film, the molar ratio is desirably 0.5 or less. If such a Be When the reaction is carried out at 100 ° C or lower, the molar ratio is desirably 0.2 or lower. This is because it is necessary to raise the temperature in the heat treatment, because the ratio of mixed aluminum is increased.

The ratio of metal compound compounded to the sol solution is desirably in the range of 0.1% by weight to 20% by weight (in terms of the ratio of the metal oxide, for example, the ratio of SiO ₂ in the case of a compound and the ratio SiO ₂ + Al ₂ O ₃ in case of Si compound of Al compound). If the ratio is smaller than 0.1% by weight, there is a possibility that an excess cycle of the film-forming step is necessary to form a film having a satisfactory thickness. If the ratio exceeds 20% by weight, there is a possibility that the viscosity of the sol solution is increased, thereby making it difficult to form the film.

Acids like about acetic acid, nitric acid and hydrochloric acid can used alone or in combination as a catalyst. The suitable amount of added (added) acid (s) is by the hydrogen ion concentration in the prepared Sollösung defined, and it is desirable that the acid (s) is added so that the pH of the sol Range from 2 to 5 lies. If the pH is less than 2 or 5 exceeds it is possible, that the hydrolytic reaction and the polymerization reaction at the time of preparing a sol solution, which is used to form a Films is suitable, can not be controlled.

If necessary, the stabilizer used to stabilize the sol solution, dependent from the chemical stability a metal compound used, are suitably selected but there will be a connection to using to form a chelate the metal, such as a β-diketone such as acetylacetone, and a β-ketoester, such as ethylacetoacetate, preferred.

The Amount of the blended stabilizer is desirably the same or less than 2 in terms of molar ratio (stabilizer / metal compound), when β-diketone is used. If the molar ratio exceeds 2, it is possible to that the hydrolytic reaction and the polymerization reaction can be hindered to produce the sol reaction.

water can the sol solution be supplied directly or indirectly by a chemical reaction, e.g. by using an esterification reaction with a carboxylic acid produced water when an alcohol is used as a solvent, or by using water vapor from the atmosphere. If Water is fed directly or indirectly to the sol solution, the molar ratio of Water / metal compound desirably equal to or less than 100. If the molar ratio exceeds 100, it is possible to that stability the solubility solution being affected.

The organic solvents is not limited and can be any solvent which is capable of producing an entire metal compound, to homogeneously dissolve a catalyst, a stabilizer and water, which Components of the sol solution are such that the produced colloid is dispersed homogeneously in the solution is. Examples for the organic solvent, which can be used are a lower alcohol such as ethanol; a hydrocarbon ether alcohol such as ethylene glycol monoalkyl ester; an acetate of hydrocarbon ether alcohol such as ethylene glycol monoalkyl ether acetate; an acetate of a lower alcohol such as ethyl acetate; and a Ketone, such as acetone. From the point of view of safety during treatment and the cost out it is desirable that lower alcohols, such as ethanol, isopropyl alcohol and butanol used alone or in combination.

The viscosity of the sol solution depends on the combination of the various components contained in the sol solution and is desirably generally equal to or less than 0.02 N · s / m ² (20 cP). If the viscosity exceeds 0.02 N · s / m ² (20 cP), there is a possibility that it becomes difficult to uniformly form a film and cracks may be generated during the heat treatment.

The Time and temperature for preparing the sol solution depend on the combination of different in the Sollösung contained components. Usually the production time is in the range of 1 min to 72 h, and the production temperature lies in the range of 0 ° C up to 100 ° C.

Examples the method of applying the sol solution to the surface of the Metal film that can be used are a dip coating method, a spraying process and a spin coating method.

To Applying the sol solution on the surface of the metal film becomes the applied sol solution of a heat treatment subjected. The necessary heating temperature may be at a level sufficient to at least the organic one solvent to evaporate. For example, if ethanol as an organic solvent is used, the minimum temperature is 80 ° C, which is a boiling point of ethanol is. On the other hand, if a sintered magnet is used, if the heating temperature Exceeds 500 ° C, the possibility, that the degradation of the magnetic property of the magnet is caused and the metal film is melted. Therefore, the heat temperature desirably in the range of 80 ° C up to 500 ° C, and more preferably in the range of 80 ° C to 250 ° C, from the standpoint of the possible Preventing the generation of cracks during cooling after the heat treatment. If a bonded magnet is used, the temperature condition must for the heat treatment under consideration the heat resistant Temperatures of a resin used to be adjusted. For example, if a made using an epoxy resin or a polyamide resin Bonded magnet is used, the heating temperature is desirable in the range of 80 to 200 ° C in view of the heat-resistant temperatures of these resins. Usually is the heating time in the range of 1 min to 1 h.

According to the above described method may be a substantially amorphous phase containing metal oxide film, which in terms of corrosion resistance is excellent, trained. For example, includes in a Si-Al composite oxide film, its structure is a large number Si-O-Si bonds and a large number of Si-O-Al bonds, in the case of a Si-rich Films, and includes a big one Number of Al-O-Al bonds and a big one Number of Si-O-Al bonds in case of Al-rich film. The conditions Both components in the film are characterized by the ratio of the mixed metal compound established.

According to the above contains described method the metal oxide film carbon (C) due to the metal compound and the stabilizer. The essentially an amorphous phase, the excellent in corrosion resistance, comprehensive Metal oxide film is easily made by the inclusion of carbon, and it is desirable that the carbon (C) content ranges from 50 ppm to 1,000 ppm (weight per weight). If the C content is smaller than 50 ppm, it is possible to that cracks are generated in the film. If the C content exceeds 1,000 ppm, it is possible, that no sufficient compression of the film occurs.

Of the formed by the method described above metal oxide film has excellent corrosion resistance, if its thickness is the same or greater than 0.01 μm is. The upper limit for the Thickness of the film capable of doing so by the one described above Method to be formed is not limited but equal to or less than 10 μm, preferably equal to or less than 5 μm, more desirably the same or smaller than 1 μm, from the viewpoint of necessity for reducing the size of the magnet yourself and the standpoint of ensuring durability, when the magnet is installed in a part whose temperature is far varies, as in a motor for an automobile. Naturally can, if necessary, apply the sol solution to the surface of the Metal film and the subsequent heat treatment repeated several times carried out become.

It can be shot peening (a method for modifying the surface by Bouncing hard particles against the surface) as a previous step before the formation of the metal oxide film performed the metal film become. The metal film can be smoothed by performing shot peening whereby the formation of a metal oxide film that is thin, but has excellent corrosion resistance, facilitated can be.

It is desirable for shot peening, a powder having a hardness equivalent to or more than Hardness of trained metal film is used. Examples of such powders are spherical Hard particles with a Mohs hardness of 3 or more, such as steel balls or glass beads. if the average particle size of the powder smaller than 30 μm is, the pressing force exerted on the metal film is smaller and it will therefore take a lot of time for the treatment is needed. On the other hand, if the average particle size of the powder Exceeds 3,000 μm, it is possible, that the smoothness the surface is too big and the finished surface is uneven. Therefore, the average particle size of the powder is more desirable in Range of 30 microns up to 3,000 μm and more desirably in the range of 40 microns up to 2,000 μm.

The shot peening pressure is desirably in the range of 0.098 MPa (1.0 kg / cm ² ) to 0.49 MPa (5.0 kg / cm ² ). If the jet thrust is lower than 0.098 MPa (1.0 kg / cm ² ), there is a possibility that the thrust force applied to the metal film is smaller and much for the treatment Time is needed. If the jet pressure exceeds 0.49 MPa (5.0 kg / cm ² ), there is a possibility that the thrust force applied to the metal film is nonuniform, accompanied by a reduction in the smoothness of the surface.

The Shot blasting time desirably should be in the range from 1 minute to 1 hour. If the beam time is shorter than 1 min the possibility, that no uniform Treatment of the entire surface can be achieved. If the beam time exceeds 1 h, it is possible to that a degradation of the smoothness the surface entry.

One in a Fe-Br-R-based permanent magnet contained in the present The rare earth element (R) used in the invention is desirably at least one element of Nd, Pr, Dy, Ho, Tb and Sm, in addition thereto at least one element of La, Ce, Gd, Er, Eu, Tm, Yb, Lu and Y.

Usually One of them (R) is enough, but in practice it can be a mixture of 2 or more rare earth elements (mischmetal and didymium and the like) for reasons procurement convenience.

Of the Content of R in a Fe-B-R based permanent magnet is more desirable in a range of 10 at% to 30 at%. If the R content lower than 10 at.%, the crystal structure is the same cubic Crystal structure as in α-Fe and for that reason, no high magnetic property, in particular no high coercive force (iHc). receive. If otherwise the R content exceeds 30 atomic%, the Content of an R-rich, non-magnetic phase and the residual Magnetic flux density (Br) is reduced so that no permanent magnet can be made with an excellent property.

Of the Fe content is desirably in a range of 65 at.% to 80 at.%. If the Fe content lower than 65 at%, becomes the residual magnetic flux density (Br) diminished. If the Fe content exceeds 80 atomic%, no high coercive force (iHc) can be obtained. It is possible the temperature characteristic without degradation of the magnetic property of the produced magnet by exchanging a portion of Fe with Co. If but exceeds the amount of substituted Co 20 of the iron, the magnetic property is degraded and therefore becomes a such amount is not preferred. The amount of substituted Co in in a range of 5 at.% to 15 at.% is to provide a High magnetic flux density desirable, because the residual magnetic flux density (Br) is increased, in comparison to a case where no part of Fe is substituted.

Of the B content is desirable in a range of 2 at.% to 28 at.%. If the B content is less than 2 atomic%, a rhombohedral structure is the main phase, and no high coercive force (iHc) is obtained. If the B content exceeds 28 atomic%, the content of a B-rich, non-magnetic phase will increase and the residual magnetic flux density (Br) is decreased so that no permanent magnet with excellent characteristics becomes.

Around improve the production of the magnet and reduce costs, may be 2.0 wt .-% P and / or 2.0 wt .-% S in a quantitative amount of 2.0 wt .-% or less contained in the magnet. Furthermore, can the corrosion resistance of the magnet by substituting a Proportion of B with 30 wt .-% or less of carbon (C) improved become.

Further, the addition is at least one of Al, Ti, V, Cr, Mn, Bi, Nb, Ta, Mo, W, Sb, Ge, Sn, Zr, Ni, Si, Zn, Hf and Ga for improving the coercive force and the perpendicularity of Demagnetisierungskurve and to improve the production and reduce costs effectively. It is desirable that at least one of these substances is added in an amount in a range that satisfies the condition that at least 0.9 T (9 kG) of Br is needed to ensure that the maximum energy product (BH) max equals or greater than 160 kJ / m ² (20 MGOe).

In addition to R, Fe and B can be the Fe-B-R based permanent magnet in industrial Production of the magnet included inevitable impurities.

The Fe-BR-based permanent magnet used in the present invention has a feature that it includes a main phase comprising a compound having a tetragonal crystal structure with an average crystal grain size in the range of 1 μm to 80 μm and 1 to 50 vol .-% of a non-magnetic phase (excluding an oxide phase). The magnet shows iHc ≧ 80 kA / m (1 kOe), Br> 0.4 T (4 kG) and (BH) max ≧ 80 kJ / m ³ (10 MGOe), with the maximum value of (BH) max 200 kJ / m ³ (25 MGOe) or more achieved.

On The metal oxide film of the present invention may have another Film to be trained. By using such a configuration is possible, to enhance the characteristic of the metal oxide film and the metal oxide film another functionality to give.

Examples

When Example was as described in U.S. Patent No. 4,770,723 pulverized and then sequentially presses, a sintering, a heat treatment and a surface treatment subjected, whereby a sintered magnet with a size of 23 × 10 × 6 mm and a composition of 17Nd - 1Pr - 75Fe - 7B was (hereinafter referred to as "magnet test piece") becomes). The magnet test piece was subjected to the following experiment using the thickness of a metal film measured using a fluorescent X-ray thickness gauge and the thickness of a metal oxide film by observing a broken surface of the film was measured with an electron microscope. The salary Carbon (C) in the metal oxide film was measured by a glow discharge mass spectrometer measured. additionally The structure of the metal oxide film was measured by using an X-ray diffractometer analyzed.

you It should be noted that the present invention is not limited to one limited to sintered Fe-B-R based magnets and also based on a Fe-B-R Bonded magnets is applicable.

example 1

150 Magnet test pieces (with a dummy volume of 0.5 l and a weight of 1.6 kg) and short columnar aluminum pieces with a diameter of 0.8 mm and a length of 1 mm (and a dummy volume of 20 l and weighing 100 kg) were placed in a treatment chamber with a volume of 50 l in a shaker-type pulverizer (their total amount was 40% by volume of the inner volume of the treatment chamber). they were then a dry treatment for 5 hours under the conditions of a vibration frequency of 60 Hz and an amplitude of 1.8 mm, resulting in an aluminum film on the surface of the magnet has been formed. The trained aluminum film had one Thickness of 0.05 μm.

A sol solution was prepared from components: an aluminum compound, a catalyst, a stabilizer, an organic solvent and water shown in Table 1 in a composition, a viscosity and a pH shown in Table 2. The sol solution was applied to the magnet by a dip coating process, which applied the aluminum film at a tensile rate shown in Table 3, and then subjected to a heat treatment shown in Table 3 to form an aluminum oxide film on the aluminum film. The formed film (Al ₂ O _x film: 0 <x ≦ 3) had a thickness of 1 μm. The content of carbon (C) in the film was 450 ppm. The structure of the film was amorphous.

The magnet with the aluminum oxide film on its surface with the interposed aluminum film was subjected to a corrosion resistance acceleration test in which it was allowed to stand under high temperature / high humidity conditions of a temperature of 80 ° C and a relative humidity of 90 for 300 hours. The magnetic properties before and after the test and the change in appearance after the test are shown in Table 4. As a result, it was found that even if the magnet was allowed to stand under the high temperature / high humidity conditions over the long period of time, the magnetic characteristic and the appearance of the magnet were little affected and a required corrosion resistance was sufficiently satisfied. The magnet was bonded to a cast iron-made tensioner with a modified acrylate-based adhesive (Product No. Hard loc G-55, manufactured by Denki Kagaku Kogyo Kabushiki Kaisha) and allowed to stand for 24 hours and then subjected to another test, namely Compressive shear test using an Amsler test machine to measure a shear bond strength of the magnet, providing an excellent value of 32.4 MPa (331 kgf / cm ² ).

Example 2

A sol solution having a composition, a viscosity and a pH as shown in Table 2 was prepared from the components: an Si compound, a catalyst, a stabilizer, an organic solvent and water shown in Table 1. The sol solution was prepared as in Example 1 and the aluminum film of 0.05 μm on its surface having a magnet applied at a pulling rate shown in Table 3 by a dip coating process and then subjected to a heat treatment shown in Table 3 to form a Si oxide film on the aluminum film. The formed film had a thickness of 0.8 μm (SiO _x film: 0 <x ≦ 2). The content of carbon in the film was 450 ppm. The structure of the film was amorphous.

The magnet prepared by the above-described method and having an Si oxide film on its surface with an aluminum film interposed therebetween was subjected to a corrosion resistance acceleration test under the same conditions as in Example 1. Table 4 shows the results. As a result, it was found that the produced magnet satisfies a required corrosion resistance sufficiently. The magnet was further subjected to another test, namely a compression shear test under the same conditions as in Example 1, to measure a shear bond strength of the magnet, thereby providing an excellent value of 26.9 MPa (274 kgf / cm ² ).

Example 3

A sol with a composition, viscosity and pH, as in table 2, was made from the components: a Zr compound, a catalyst, a stabilizer, an organic solvent and water shown in Table 1. The sol solution was changed to that in Example 1 produced and the aluminum film of 0.05 microns on its surface Magnets at a pulling rate shown in Table 3 by a dip coating process and then a heat treatment shown in Table 3 to form a Zr oxide film on the aluminum film. The formed film had a thickness of 1 μm (ZrOx film: 0 <x ≦ 2). The amount at carbon in the film was 450 ppm. The structure of the movie was amorphous.

Of the produced by the method described above and the Zr oxide film on its surface with inserted in between Aluminum film-bearing magnet was subjected to a corrosion resistance acceleration test subjected under the same conditions as in Example 1. The results are shown in Table 4. As a result, it was found that the produced magnet sufficiently satisfies the required corrosion resistance Fulfills.

Example 4

A sol solution having a composition, viscosity and pH as shown in Table 2 was prepared from the catalyst, a stabilizer, an organic solvent and water shown in Table 1. The sol solution was applied to the aluminum film of Example 1 and Al 0.05 μm on its surface-bearing magnet was applied by a dip coating process and then subjected to a heat treatment shown in Table 3 to form a Ti oxide film on the aluminum film. The formed film had a thickness of 1 μm (TiO _x film: 0 <x ≦ 2). The content of carbon in the film was 320 ppm. The structure of the film was amorphous.

Tabelle 2

Anm. 1:

in Bezug auf Al₂O₃

Anm. 2:

in Bezug auf SiO₂

Anm. 3:

in Bezug auf ZrO₂

Anm. 4:

in Bezug auf TiO₂

Anm. 5:

unter Verwendung von Wasserdampf in der Atmosphäre.

Tabelle 3

Tabelle 4

Vergl. =

Vergleichs–

The magnet prepared by the above-described process and having a Ti-oxide film on its surface with the aluminum interposed therebetween was subjected to a corrosion resistance acceleration test under the same conditions as in Example 1. Table 4 shows the results. As a result, it was found that the produced magnet sufficiently satisfied a required corrosion resistance. Table 1

Table 2

Note 1:

with respect to Al ₂ O ₃

Note 2:

with respect to SiO ₂

Note 3:

in terms of ZrO ₂

Note 4:

in terms of TiO ₂

Note 5:

using water vapor in the atmosphere.

Table 3

Table 4

Comp. =

comparison

Comparative Example 1

The Magnet test piece was degreased, into an acid immersed in a 4.6 g / L zinc and 17.8 g / L phosphate treatment solution with a temperature of 70 ° C immersed, whereby a phosphate film with a thickness of 1 micron on the surface of the magnet has been formed. The manufactured magnet became one Corrosion resistance acceleration test under the same conditions as in Example 1 subjected. The results are presented in Table 4. As a result, the produced magnet was in terms of its magnetic characteristic degraded and rusted.

Comparative Example 2

The Magnet test piece became a corrosion resistance acceleration test subjected under the same conditions as in Example 1. The results are shown in Table 4. As a result, the magnetic section was with respect to its magnetic properties diminished and rusted.

Example 5

A sol solution was prepared from the following components: a Si compound, an aluminum compound, a catalyst, a stabilizer, an organic solvent, and water shown in Table 5 at a composition, a viscosity, and a pH in Table 6 are shown. The sol solution was coated on the magnet prepared in Example 1 and having the aluminum film of 0.05 μm on its surface at a pulling rate shown in Table 7 by a dip coating process and then subjected to a heat treatment shown in Table 7 to obtain a Si-Al composite oxide film on the aluminum film. The formed film (SiO _x Al ₂ O _y film: 0 <x ≦ 2 and 0 <y ≦ 3) had a thickness of 0.9 μm. The content of carbon (C) in the film was 290 ppm. The structure of the film was amorphous.

Anm. 1:

Verbindung repräsentiert durch (H₅C₂O)₃SiOAl(OC₂H₅)₂

The magnet prepared by the above-described process and having the Si-Al composite oxide film on its surface with the aluminum film interposed therebetween was subjected to a corrosion resistance acceleration test under the same conditions as in Example 1. The results are shown in Table 8. As a result, it was found that the produced magnet sufficiently satisfied a required corrosion resistance. The magnet was further subjected to another test, a compression shear test under the same conditions as in Example 1, to measure a shearing strength of the magnet, which showed an excellent value of 31.7 MPa (323 kgf / cm ² ). Table 5

Note 1:

Compound represented by (H ₅ C ₂ O) ₃ SiOAl (OC ₂ H ₅ ) ₂

Table 6

Table 7

Table 8

Example 6

30 Magnet test pieces (with a dummy volume of 0,1 l and a weight of 0,32 kg) and short columnar Sn pieces with a diameter of 0.8 mm and a length of 1 mm (and a dummy volume of 2 l and weighing 11 kg) were placed in a treatment chamber with a volume of 3.5 l in a shaker-type pulverizer (their total amount was 60% by volume of the inner volume of the treatment chamber). they were then a dry treatment for 5 h under conditions of a vibration frequency of 60 Hz and a Amplitude of 1.5 mm subjected to a Sn film on the surface of the To form magnets. The trained Sn movie had a thickness of 0.4 μm.

The sol solution was prepared from the components: a silicon (Si) compound, a catalyst, a stabilizer, an organic solvent, and water shown in Table 9, with a composition, a viscosity, and a pH in Table 10 are shown. The sol solution was coated on the magnet with the Sn film at a tensile rate shown in Table 11 by a dip coating process and then subjected to a heat treatment shown in Table 11 to form a Si oxide film on the Sn film. The formed film (SiO _x film: 0 <x ≦ 2) had a thickness of 0.3 μm. The content of carbon (C) in the film was 350 ppm. The structure of the film was amorphous.

Of the produced by the method described above and the Si oxide film on its surface with inserted in between Sn film-bearing magnet was subjected to a corrosion resistance acceleration test subjected under the same conditions as in Example 1. In table 12, the results are shown. As a result, it was found that the magnet produced sufficient corrosion resistance required satisfied.

Example 7

150 Magnet test pieces (with a dummy volume of 0.5 l and a weight of 1.6 kg) and short columnar Zn pieces with a diameter of 1 mm and a length of 1 mm (and a dummy volume of 20 l and weighing 100 kg) were placed in a treatment chamber with a volume of 50 l in a shaker-type pulverizer (their total amount was 40% by volume of the inner volume of the treatment chamber). they were then a dry treatment for 5 h under conditions of a vibration frequency of 60 Hz and a Amplitude of 1.8 mm subjected to a Zn film on the surface of the To form magnets. The formed Sn film had a thickness of 0.2 μm.

The sol solution was prepared from the components: a silicon (Si) compound, a catalyst, a stabilizer, an organic solvent, and water shown in Table 9 at a composition, a viscosity, and a pH are shown in Table 10. The sol solution was coated on the magnet with the Zn film at a pulling rate shown in Table 11 by a dip coating process and then subjected to a heat treatment shown in Table 11 to form a Si oxide film on the Zn film. The formed film (SiO _x film: 0 <x ≦ 2) had a thickness of 0.7 μm. The content of carbon (C) in the film was 450 ppm. The structure of the film was amorphous.

The magnet prepared by the above-described method and having the Si oxide film on its surface with the Zn film interposed therebetween was subjected to a corrosion resistance acceleration test under the same conditions as in Example 1. Table 12 shows the results. As a result, it was found that the produced magnet had a required corrosion resistance satisfied satisfied.

Example 8

The sol solution was prepared from the components: a silicon (Si) compound, a catalyst, a stabilizer, an organic solvent, and water shown in Table 9, with a composition, a viscosity, and a pH in Table 10 are shown. The sol solution was applied to the magnet having the Zn film of 0.2 μm on its surface at a pulling rate shown in Table 11 by a dip coating process and then subjected to a heat treatment shown in Table 11 to form a Zr oxide film on the Zn film train. The formed film (ZrO _x film: 0 <x ≦ 2) had a thickness of 0.6 μm. The content of carbon (C) in the film was 140 ppm. The structure of the film was amorphous.

Tabelle 10

Anm. 1:

in Bezug auf SiO₂

Anm. 2:

in Bezug auf ZrO₂

The magnet prepared by the above-described method and having the Zr oxide film on its surface with the Zn film interposed therebetween was subjected to a corrosion resistance acceleration test under the same conditions as in Example 1. Table 12 shows the results. As a result, it was found that the produced magnet sufficiently satisfied a required corrosion resistance. Table 9

Table 10

Note 1:

with respect to SiO ₂

Note 2:

in terms of ZrO ₂

Table 11

Table 12

Claims (8)

Process for producing a permanent magnet with a metal oxide film on its surface with an interposed one Metal film comprising the steps in which one based on Fe-B-R Permanent magnet and pieces of metal with a needle-shaped Shape or a columnar Shape with a length of 0.05 mm to 10 mm into a treatment tank, where shaken her and / or moved so as to form a metal film on the surface of the Magnets to form, on the surface of the metal film, a sol solution, the by the hydrolytic reaction and the polymerization reaction a metal compound is prepared and a starting material for one Represents metal oxide film, is applied and the applied sol a heat treatment is subjected to form this metal oxide film. The method of claim 1, wherein the metal piece is used is to this metal film, which consists of at least one metal component is made, which is selected from the group consisting of aluminum (Al), tin (Sn) and zinc (Zn) to form. The method of claim 1, wherein the thickness of this Metal film is in a range of 0.01 microns to 1 micron. The method of claim 1, wherein said sol solution is used to form this metal oxide film consisting of at least one metal oxide component is selected from the group consisting of aluminum (Al) oxide, Silicon (Si) oxide, zirconium (Zr) oxide and titanium (Ti) oxide exist to form. The method of claim 1, wherein the sol solution is used is added to this metal oxide film, which is the same metal component as the metal component of this metal film contains form. The method of claim 1, wherein the thickness of this Metal oxide film is in a range of 0.01 microns to 10 microns. The method of claim 1, wherein the content of carbon (C) contained in this metal oxide film in a range from 50 ppm to 1,000 ppm. The method of claim 1, wherein said metal oxide film is formed from a metal oxide, which is essentially an amorphous Phase includes.