JP3877552B2 - Method for manufacturing metal member - Google Patents

Description

上記の噴射条件によって形成された皮膜の厚さ（膜厚）は表１に示す通りである。実施例１〜６および比較例について、塩水噴霧試験前の磁気特性を測定したところ、表１に記載のようになった。なお、実施例１〜６については皮膜形成後の磁気特性を測定した（比較例は皮膜なし）。
次いで、実施例１〜６および比較例について、ＪＩＳ Ｃ ００２３での塩水噴霧試験方法に則り、５ｗｔ％３５℃の塩水噴霧下において１００時間まで試験を行い、発錆の有無を観察した。その結果を表１に併せて示す。なお、磁気特性については、５ｗｔ％３５℃の塩水を２４時間噴霧した試料に対して試験前後の磁気特性を比較した。
【００４１】
【表１】

【００４２】
表１に示すように、皮膜の膜厚が厚いほど、発錆が抑制されていることがわかる。特に、Ｓｎ粉末からなる皮膜を１０.２μｍ形成した実施例２およびＺｎ粉末からなる皮膜を９.６μｍ形成した実施例４は、１００時間後においても発錆が観察されなかったところから、緻密でかつ密着力の強い皮膜が形成されていることが伺える。なお、この試験では、皮膜の材質による発錆の程度の差異は、観察されなかった。
【００４３】
前述のように、皮膜形成前の磁気特性は、残留磁束密度Ｂｒが１．２７Ｔ、保磁力Ｈｃｊが１６９５ｋＡ／ｍであった。これに対して、皮膜形成後の磁気特性は、表１に示す通りであって、皮膜形成による磁気特性の低下はほとんどないといってよい。したがって、本実施例による皮膜形成方法は、磁石にとって望ましい。
塩水噴霧試験前後の磁気特性を比較すると、前述した発錆の程度と傾向が一致する。つまり、塩水噴霧試験を１００時間経過した時点で発錆の観察されない実施例２および実施例４は、磁気特性の劣化がないかあるいは僅かである。塩水噴霧試験が２４〜１００時間で発錆の観察された実施例１，３，５および６は、若干の磁気特性の劣化が観察されたが、皮膜を形成していない比較例に比べると、劣化の度合いが少ない。
【００４４】
【発明の効果】
本発明によれば、樹脂やカップリング剤などの第三の成分を用いることなく、しかも磁気特性を低下させることなく、希土類金属を含む基材上に耐食性皮膜を形成することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rare earth metal member having a film formed on its surface and a method for producing the same.
[0002]
[Prior art]
R (rare earth metal element) -Fe-B permanent magnets represented by Nd-Fe-B permanent magnets are made of resource-rich and inexpensive materials compared to Sm-Co permanent magnets, and Have high magnetic properties. Therefore, in particular, R—Fe—B permanent magnets are used in various fields today.
In recent years, in the electronics industry and household electrical appliance industry in which rare earth permanent magnets are used, parts have been downsized and downsized, and accordingly, the magnets themselves have been urged to be downsized and complicated shapes.
[0003]
By the way, since the rare earth permanent magnet contains R that is easily oxidized and corroded in the atmosphere, it is usually subjected to a surface treatment. If it is used without such surface treatment, corrosion will proceed from the surface due to the influence of slight acid, alkali or moisture, and rust will be generated, resulting in deterioration and dispersion of magnetic properties. Because it becomes. In addition, when a magnet with rust is incorporated into an apparatus such as a magnetic circuit, the rust may scatter and contaminate peripheral components.
[0004]
[Problems to be solved by the invention]
Not only rare earth permanent magnets but also base materials containing rare earth metal elements are easily oxidized, and various rust prevention methods have been applied to suppress this. For example, as a rust prevention method using a Zn or Sn metal film, a plating method (for example, JP-A-1-231303, JP-A-1-321610), resin coating using Sn alkoxide (JP-A-4-353007) ), Coating of a Zn, Sn film with a barrel (Japanese Patent Laid-Open No. 12-031962) is known.
However, in the case of the plating method, the rare earth metal may be corroded by the plating solution or the remaining plating solution. Further, the resin coating using Sn alkoxide has a disadvantage that the adhesion strength is low, and it is necessary to increase the temperature during film formation in order to increase the adhesion strength. However, when the temperature during film formation is increased, there is a concern about oxidation of rare earth metals.
[0005]
In addition, it is possible to impart conductivity to the entire surface of the bonded magnet and to prevent rust by plating using the conductivity, as disclosed in JP-A-5-302176, JP-A-7-302705, and JP-A-5-304705. 10-226890.
However, in any method, the metal powder is attached to the magnet surface using the adhesiveness of the third component such as a resin or a coupling agent. Such a method requires a third component, which increases costs and makes it difficult to form a conductive layer uniformly on the entire magnet surface, resulting in high dimensional accuracy. Surface treatment becomes difficult. Moreover, since a curing process for the uncured resin is required, the manufacturing process becomes complicated. Furthermore, when a medium such as a steel ball, a copper ball, a stainless steel ball, or an alumina ball is used as a means for attaching the metal powder, the bonded magnet may be cracked or chipped.
[0006]
According to the method described in JP-A-9-205013, it is possible to fill the gaps on the magnet surface with metal powder without using a third component such as a resin or a coupling agent. However, this method does not attempt to attach metal powder onto magnetic powder that essentially constitutes the magnet surface. Therefore, even if the metal powder adheres to the magnetic powder, the adhesion force is inevitably weak, so that the metal powder cannot be firmly attached to the magnetic powder. In addition, this method requires a step of removing excess metal powder weakly adhering to the magnetic powder by washing, which complicates the manufacturing process.
Therefore, the present invention provides a technique capable of forming a corrosion-resistant film on a substrate containing a rare earth metal without using a third component such as a resin or a coupling agent and without lowering magnetic properties. Let it be an issue.
[0007]
[Means for Solving the Problems]
  The present inventors paid attention to a mechanochemical (mechanochemical 1) reaction, which is a unique surface chemical reaction caused by an innocent metal surface (fresh surface) that has not been oxidized or the like, and conducted various studies. As a result, the adhesion strength of the coating formed on the surface of the rare earth metal is improved by injecting the metal fine powder as a mixed fluid of high-pressure gas, and the reaction part by injection by injecting the metal fine powder as the mixed fluid of high-pressure gas It was found that the internal temperature did not increase because of being suppressed near the surface. That is, the present inventionA step of using a spherical metal powder having an average particle size of 30 to 150 μm produced by the gas atomization method as a mixed fluid of high-pressure gas, and the mixed fluid from the injection nozzle to the rare earth sintered magnet surface from 3 to 10 kg / cm ² Forming a film having a thickness of 1.5 to 20 μm by injecting the injected metal powder onto the surface of the rare earth sintered magnet by a mechanochemical reaction. A rare earth sintered magnet formed on the surface of the metal member is characterized in that rusting does not occur when salt water spraying of 5 wt% and 35 ° C. is continued for 24 hours.It is.
[0008]
  In the metal member manufacturing method of the present invention, a metal powder composed of one or more of Cu, Fe, Ni, Co, Cr, Sn, Zn, Pb, Cd, In, Au, Ag, and Al is used. It is desirable to use it.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention includes a base material containing a rare earth metal element and having a metal phase exposed on the surface thereof, and a film covering the surface of the base material composed of metal powder adhered to the metal phase by a mechanochemical reaction, A metal member is provided.
The base material of the present invention widely includes materials containing rare earth metal elements. As a most typical example, a metal material containing a rare earth metal element can be used as a base material of the present invention, and as a more specific example, a rare earth sintered magnet obtained by sintering a powder having a predetermined composition. Examples of rare earth sintered magnets include R—Fe—B based sintered magnets typified by Nd—Fe—B based sintered magnets, R—Co based sintered magnets typified by Sm—Co based sintered magnets, and the like. Can be mentioned.
[0011]
Hereinafter, the case where a rare earth sintered magnet is used as a base material will be described.
Magnetic powder used as a raw material for sintered magnets can be obtained by dissolving a rare earth permanent magnet alloy and pulverizing it after casting. Once a sintered magnet is prepared, a sintered body pulverizing method for pulverizing the sintered magnet. Direct reduction diffusion method to obtain direct magnetic powder, ribbon foil of rare earth permanent magnet alloy is obtained by melting jet caster, rapid cooling alloy method to crush and anneal this, melt rare earth permanent magnet alloy, and atomize this into powder and heat treatment It can be obtained by a method such as an atomizing method, a mechanical alloying method in which a raw material metal is made into a powder, then finely powdered by mechanical alloying and heat-treated.
Below, the outline | summary of the sintered compact grinding | pulverization method, the direct reduction diffusion method, the quenching alloy method, the atomizing method, and the mechanical alloy method is shown.
[0012]
(Sintered body grinding method)
In this method, a required R—Fe—B alloy is sintered and ground again to obtain a magnetic powder. For example, as a starting material, a raw material powder containing electrolytic iron, B, the balance being impurities such as Fe and Al, Si, C, and the like, ferroboron alloy, rare earth metal, or further electrolytic Co is added under an inert gas atmosphere. Then, it is alloyed by high frequency melting or the like, coarsely pulverized using a stamp mill or the like, and further finely pulverized by a ball mill or the like. The obtained fine powder is pressure-molded under a magnetic field or without applying a magnetic field, sintered in a vacuum or inert gas which is a non-oxidizing atmosphere, pulverized again, and an average particle size of 0.3 to 100 μm. A fine powder is obtained. Thereafter, heat treatment may be performed at 500 to 1000 ° C. in order to increase the coercive force.
[0013]
(Direct reduction diffusion method)
Select a raw material powder consisting of at least one metal powder and / or oxide powder consisting of ferroboron powder, ferronickel powder, cobalt powder, iron powder, rare earth oxide powder, etc. according to the composition of the desired raw material alloy powder, To the raw material powder, metal Ca or CaH₂Was mixed 1.1 to 4.0 times (by weight) the stoichiometric amount required for the reduction of the rare earth oxide powder, and heated to 900 to 1200 ° C. in an inert gas atmosphere. By introducing the product into water and removing the reaction by-products, a powder having an average particle size of 10 to 200 μm that does not require coarse pulverization is obtained. The obtained powder may be further finely pulverized by dry pulverization such as ball mill and jet mill. Further, a finely pulverized powder having a required composition of 3 μm or less is oriented-molded in a magnetic field, pulverized, further heat treated at 800 to 1100 ° C., and then pulverized to obtain a magnetic powder having a high coercive force. Can do.
[0014]
(Quenched alloy method)
A required R—Fe—B alloy is melted and melt-spun with a jet caster to obtain a ribbon foil having a thickness of about 20 μm, which is pulverized and then annealed to obtain a powder having fine crystal grains of 0.5 μm or less. To do. Alternatively, the powder having fine crystal grains obtained from the ribbon foil may be subjected to hot pressing and warm upsetting to obtain an anisotropy bulk magnet, which may be finely pulverized.
[0015]
(Atomization method)
A method for obtaining a magnetic powder by melting a required R-Fe-B-based alloy, dropping a molten metal from a thin nozzle, atomizing with a high-speed inert gas or liquid, sieving or pulverizing, and drying or annealing heat treatment It is. Alternatively, the powder having the fine crystal grains may be hot pressed and warm upset to obtain an anisotropy bulk magnet, which may be finely pulverized.
[0016]
(Mechanical alloy method)
In this method, necessary raw material powder is mixed and made amorphous at an atomic level in an inert gas by a ball mill, vibration mill, dry attritor, etc., and then annealed to obtain magnetic powder. Alternatively, the powder having the fine crystal grains may be hot-pressed / warm-up processed to obtain an anisotropy bulk magnet, which may be finely pulverized.
[0017]
In addition to such a method, in particular, by using magnetic powder obtained by pulverizing an alloy thin plate having a columnar crystal structure grown in the plate thickness direction by a molten metal quenching method (see Japanese Patent No. 2665590). A sintered magnet having high magnetic properties can be obtained. The magnetic powder constituting the R—Fe—N based sintered magnet is a method such as a gas nitriding method in which a rare earth permanent magnet alloy is pulverized, nitrided in nitrogen gas or ammonia gas, and then pulverized. But you can get it.
[0018]
In addition, a sintered magnet can be easily obtained by employ | adopting a well-known powder metallurgy method. The application of anisotropy can be realized by orientation-molding magnetic powder having magnetic anisotropy in a magnetic field. As a method of imparting magnetic anisotropy to bulk and magnetic powder, alloy powder obtained by quenching alloy method is sintered at low temperature by hot press etc., and further magnetic anisotropy by warm upsetting Warm processing and pulverization method (see Japanese Patent Publication No. 4-20242) for pulverizing a bulk magnet body to which a metal is applied, and alloy powder obtained by a quenching alloy method is filled and sealed as it is in a metal container, warm rolling, etc. Pack rolling method (see Japanese Patent No. 2596835) that imparts magnetic anisotropy by plastic working of the above, an alloy ingot is plastic processed hot, and then pulverized to produce magnetic powder having magnetic anisotropy Ingot hot working / grinding method (see Japanese Patent Publication No. 7-66892), a rare earth permanent magnet alloy is heated in hydrogen to occlude hydrogen, dehydrogenated, and then cooled to obtain magnetic powder. obtain And the like can be employed DDR method (see Japanese Patent Kokoku 6-82575). The application of magnetic anisotropy is not limited to the combination of the raw material alloy and the anisotropic means, and can be combined as appropriate.
[0019]
The magnet or magnetic powder obtained by the above method is, for example, an R-TM-B system (one or more of R: Y-containing rare earth metal elements, TM: Fe as a transition metal element, B : Boron). This R-TM-B-based magnetic powder has a main phase having a substantially tetragonal crystal structure. The particle size of the main phase is preferably about 1 to 100 μm. Furthermore, it usually contains a nonmagnetic phase of 1 to 50% by volume.
[0020]
The composition of the R-TM-B magnet in the present invention is preferably 5.5 at% ≦ R ≦ 30 at%, 42 at% ≦ TM ≦ 90 at%, 2 at% ≦ B ≦ 28 at%.
Here, the rare earth metal element R is one or more of rare earth metal elements including Y (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu). . Preferably, a light rare earth metal element such as Nd, Pr, Ho, and Tb is mainly used, or a mixture with Nd, Pr, or the like is mainly used. When the amount of the rare earth metal element R is less than 5.5 at%, the cubic structure having the same structure as α-Fe increases, and thus a high coercive force Hcj cannot be obtained. On the other hand, when the amount of the rare earth metal element R exceeds 30 at%, the R-rich nonmagnetic phase increases and the residual magnetic flux density Br decreases. Therefore, the amount of the rare earth metal element R is set to 5.5 to 30 at%. In addition, when using 2 or more types of elements as rare earth metal element R, mixtures, such as a misch metal, can be used as a raw material.
[0021]
The transition metal element TM containing Fe as a main component is basically composed of Fe and inevitable impurities. When the transition metal element TM is less than 42 at%, the residual magnetic flux density Br decreases. On the other hand, when the transition metal element TM exceeds 90 at%, the coercive force Hcj is lowered. Therefore, the content of the transition metal element TM is set to 42 to 90 at%. Further, by replacing part of Fe in the transition metal element TM with Co or Ni, the temperature characteristics can be improved without impairing the magnetic characteristics. However, when the Co substitution amount exceeds 50% of Fe, the magnetic properties are deteriorated. Therefore, when a part of Fe is substituted with Co, the Co substitution amount is set to 50% or less. When a part of Fe is substituted with Ni, the Ni substitution amount is 8% or less of Fe. This is because when the Ni substitution amount exceeds 8%, the magnetic properties are deteriorated.
[0022]
The reason why the boron B is set to 2 to 28 at% is as follows. That is, when boron B is less than 2 at%, a rhombohedral structure is obtained and a high coercive force Hcj cannot be obtained. However, if boron B exceeds 28 at%, the B-rich nonmagnetic phase increases, and the residual magnetic flux density Br tends to decrease. Therefore, the upper limit is set to 28 at%. Further, by replacing a part of boron B with one or more of C, P, S, and Cu, it is possible to improve productivity and reduce costs. In this case, it is preferable that a substituted body is 4 at% or less of the whole.
[0023]
In addition, in the magnet of the present invention, in addition to R, TM, and B, Ni, Si, Al, Cu, Ca, O, C, and the like as inevitable impurities may be contained in 3 at% or less of the whole.
In addition, Cu, S, Ti, Si, V, Nb, Ta, Cr, Mo, W, Mn, Al, Sb, Ge for improving coercive force Hcj, improving corrosion resistance, improving productivity, and reducing costs. , Sn, Zr, Hf, Ca, Mg, Sr, Ba, Be, Ga, Bi, and Ni can be added to and contained in the raw material powder to obtain a magnetic powder. Specifically, Cu: 3.5 at% or less, S: 2.5 at% or less, Ti: 4.5 at% or less, Si: 15 at% or less, V: 9.5 at% or less, Nb: 12.5 at% or less Ta: 10.5 at% or less, Cr: 8.5 at% or less, Mo: 9.5 at% or less, W: 9.5 at% or less, Mn: 3.5 at% or less, A1: 9.5 at% or less, Sb : 2.5 at% or less, Ge: 7 at% or less, Sn: 3.5 at% or less, Zr: 5.5 at% or less, Hf: 5.5 at% or less, Ca: 8.5 at% or less, Mg: 8.5 at %, Sr: 7 at% or less, Ba: 7 at% or less, Be: 7 at% or less, Ga: 10 at% or less, Bi: 5 at% or less, Ni: 8 at% or less, or one or more of raw material powders Can be added and contained. In this case, however, the total amount added is preferably 10 at% or less.
[0024]
The effect of the present invention does not vary depending on the composition of the magnet, the crystal structure, the presence or absence of anisotropy, and the like. Therefore, the intended effect can be obtained not only in the R-TM-B sintered magnet but also in any of the above-described sintered magnets.
[0025]
Although the sintered magnet has been described above, the present invention can also be applied to a bonded magnet. That is, a magnetic powder exposed on the surface of the bonded magnet and a metal powder described later cause a mechanochemical reaction, thereby enabling film formation on the bonded magnet when viewed macroscopically. As rare earth-based bond magnets, those having various compositions and crystal structures are known, and all of these are objects of the present invention. For example, anisotropic R-Fe-B based bonded magnets as described in JP-A-9-92515, soft magnetic phases (for example, α- Fe and Fe₃B) and hard magnetic phase (Nd₂Fe₁₄B) Nd-Fe-B-based nanocomposite magnets, isotropic Nd-Fe-B-based magnet powders prepared by a liquid quenching method widely used in the past (for example, trade name: MQP-B And a bonded magnet using MQI). Also, an R—Fe—N system represented by (Fe1-xRx) 1-yNy (0.07 ≦ x ≦ 0.3, 0.001 ≦ y ≦ 0.2) described in Japanese Patent Publication No. 5-82041. Bond magnet etc. are mentioned.
[0026]
Next, the conditions for forming a film on the substrate, that is, the conditions required for the metal powder for film formation and the injection conditions for the metal powder for film formation will be described.
[0027]
(Concerning conditions required for metal powder for film formation)
The powder size is preferably about 10 to 500 μm as an average particle size. When the average particle diameter of the powder is 10 μm or less, the energy of the particles is low, so that it is difficult to obtain sufficient adhesion to the sample surface. On the other hand, when the average particle diameter of the powder exceeds 500 μm, the existing coarse particles do not react sufficiently even when they collide with the sample surface. That is, it becomes difficult to obtain a dense film, and the rust prevention ability is reduced. In addition, large particles having an average particle size exceeding 500 μm are not preferred because they are not only difficult to adhere to the sample surface but also can give distortion (damage) to the object to be processed. Therefore, the powder size is about 10 to 500 μm as an average particle size. The powder size is more preferably an average particle size of 20 to 350 μm, and still more preferably an average particle size of 30 to 150 μm.
The powder shape is not particularly limited, but spherical particles are preferable. Remarkably flat particles are not preferable because they become unstable flight even by spraying and the film formation efficiency (deposition efficiency) is lowered.
Examples of the method for producing the metal powder include, but are not limited to, a gas atomization method, a water atomization method, and a pulverization method. Preferably, a metal powder obtained by a gas atomization method or a water atomization method is used. In addition, when using the metal powder obtained by the grinding | pulverization method, since film-forming efficiency falls, it is preferable to reduce the internal distortion of a metal powder by heat processing etc. before use.
[0028]
As the metal powder for film formation, metal powder such as Cu, Fe, Ni, Co, Cr, Sn, Zn, Pb, Cd, In, Au, Ag, Al, or an alloy powder thereof can be used. Among these, Sn, Zn, Pb, Cd, In, Au, Ag, and Al have a Vickers hardness value of 60 or less and are excellent in spreadability, and therefore are suitable as metal powders for film formation. The Vickers hardness is one of the indices indicating the hardness of the material, and the measurement test can be performed based on, for example, a Vickers hardness test method (JISZ2244) using a Vickers hardness tester (JISB7725). .
Moreover, as a metal powder for film formation, the thing containing the metal component whose melting | fusing point is 450 degrees C or less, for example, the metal powder of Sn, Zn, Pb, Cd, In, or these alloy powders can be used. By using a metal powder containing a metal component having a melting point of 450 ° C. or lower, that is, a low melting point, the temperature rise of the base material containing the rare earth metal element can be suppressed, and oxidation can be effectively suppressed.
[0029]
The metal powder may be composed of each single metal component described above, or may be composed of an alloy containing two or more metal components. Moreover, it may be made of an alloy containing these metal components as a main component and other metal components. When such an alloy is used, it is desirable to select an appropriate combination of metal components according to the required spreadability. The metal powder may contain impurities unavoidable for industrial production.
[0030]
(About injection conditions of metal powder for film formation)
The injection conditions are selected for the target film thickness depending on the injection pressure, the distance between the nozzle and the element body, the injection time, the amount of the object to be processed, and the like. Specifically, the injection pressure is 3 to 10 kg / cm.²The distance between the nozzle and the element body can be 5 to 30 cm, and the injection time can be about 1 to 20 minutes. When the spraying time is short (specifically, when the spraying time is less than 1 minute), film formation on the entire object to be processed is not sufficient, and unevenness tends to occur. Although it is possible to increase the film thickness by increasing the injection time, a long-time injection (specifically, when the injection time exceeds 20 minutes) is not effective because it causes a decrease in productivity. .
Next, a film thickness control method will be described. The thickness of the coating is controlled by the type of raw material powder (element type, particle size, manufacturing method, etc.), the distance between the nozzle and the element body, the injection pressure, and the injection time. For example, it is possible to arbitrarily control the film thickness, that is, the film thickness, by selecting the injection pressure according to the type of raw material powder to be used and controlling the injection time in a state where this injection pressure is constant. .
In the case where a large number of samples are processed, a method such as an amplitude of an injection nozzle or a rotation of a sample container can be appropriately used.
[0031]
As described above, the present invention uses a mechanochemical reaction, which is a unique surface chemical reaction caused by a fresh metal surface, to form a film made of metal powder on the metal constituting the substrate surface containing the rare earth metal element. Form efficiently. Since the film formed by the mechanochemical reaction is formed firmly and densely on the metal constituting the surface of the rare earth metal material, it cannot be removed by rubbing the surface by hand. Therefore, the film does not fall off during various handling until the completion of the secondary process such as the electroplating process such as the cleaning process after the film is formed.
[0032]
Thus, it is possible to perform a well-known electroplating process etc. with respect to the rare earth metal material in which the film | membrane was formed in the whole base-material surface. In addition, the plating film can be formed on the surface with high film thickness dimensional accuracy, and the dimensional accuracy of the rare earth metal material can be improved.
For example, when a ring-shaped magnet having a plating film is used for a motor, the magnetic characteristics of the magnet itself can be utilized to the maximum, and energy efficiency can be improved. Further, it is possible to reduce the size of the motor. In addition, even if it is a film | membrane which consists of any metal powder, it is possible to form a plating film on the surface.
[0033]
In addition, the coating made of metal powder formed by mechanochemical reaction is formed on the metal constituting the surface of the rare earth metal material firmly and with high density, so the coating itself prevents the rare earth metal material from rusting. Have
In order to provide high corrosion resistance, it is necessary to perform electroplating, etc., but for materials (such as magnets for resin-embedded motors) that only require corrosion resistance until the completion of component manufacture. The film itself made of metal powder functions effectively as a rust preventive layer for the material. For example, a film made of Al fine powder forms an oxide film on its surface and also exhibits a rust prevention effect.
[0034]
In addition to the plating film, various corrosion-resistant films such as a metal oxide film and a chemical conversion film can be formed on the film made of the metal powder. Since the film is uniformly and firmly formed on the entire material surface, the film can be formed with high film thickness dimensional accuracy. Hereinafter, a method for forming a metal oxide film on a film made of a metal powder and a method for forming a chemical conversion film on a film made of a metal powder will be sequentially described.
[0035]
(About a method of forming a metal oxide film on a film made of metal powder)
As a method for forming the metal oxide film, a known method such as a CVD method, a sputtering method, a coating pyrolysis method, or a sol-gel film forming method can be used, but the metal oxide film is formed by the sol-gel film forming method. Is desirable. Here, the sol-gel film forming method is to form a film by applying a sol solution obtained by hydrolysis reaction or polymerization reaction of a metal compound constituting a metal oxide film on the surface of the material and then heat-treating it. This refers to a film formation method. The sol solution used in the sol-gel film formation method is relatively stable and can form a film at a relatively low temperature, so that the influence on the magnetic properties of the base material (for example, rare earth permanent magnet) itself at a high temperature can be avoided. There are advantages. The metal oxide film may be a film composed of a single metal oxide component or a composite film composed of a plurality of metal oxide components. The metal oxide film exhibits excellent corrosion resistance when the film thickness is 0.01 μm or more. Although the upper limit of the film thickness is not particularly limited, 10 μm or less, preferably 5 μm or less is a film thickness suitable for practical use from the request based on the miniaturization of the material itself.
When a metal oxide film containing the same metal component as the metal component forming the film is formed on the film (for example, formation of a metal oxide film containing Al on a film made of Al fine powder) at the interface between the two This is convenient in that the adhesion of the resin becomes stronger.
[0036]
When using the sol-gel film forming method, the sol solution is composed of a metal compound such as a metal alkoxide (a part of the alkoxyl group may be substituted with an alkyl group or the like), a catalyst such as nitric acid or hydrochloric acid, and if desired. A solution in which a colloid obtained by adjusting a stabilizer such as β-diketone, water or the like in an organic solvent and dispersing a metal compound by a hydrolysis reaction or a polymerization reaction is used. In addition, inorganic fine particles or the like may be dispersed in the sol liquid. Examples of the sol solution coating method include a dip coating method, a spray method, and a spin coating method. The heat treatment after application of the sol solution is preferably performed at 80 to 200 ° C. in consideration of the boiling point of the organic solvent in the sol solution and the heat resistance of the magnet, particularly when applied to a bonded magnet. In general, the heat treatment time is 1 minute to 1 hour. Needless to say, coating and heat treatment may be repeated in order to obtain a film having a desired film thickness.
[0037]
(About a method of forming a chemical conversion coating on a coating made of metal powder)
As a method of forming a chemical conversion treatment film, chromate treatment, phosphoric acid treatment, zinc phosphate treatment, manganese phosphate treatment, calcium phosphate treatment, zinc phosphate calcium treatment, titanium-phosphate chemical conversion treatment, zirconium-phosphate chemical conversion treatment Known methods such as treatment can be used. In order to improve the corrosion resistance of the coating made of Al fine powder, chromate treatment, titanium-phosphate conversion treatment, zirconium-phosphate conversion treatment, etc. are desirable, and in particular, the environmental load of the treatment liquid and coating is small. Titanium-phosphate conversion treatment and zirconium-phosphate conversion treatment are desirable.
[0038]
The treatment liquid for the titanium-phosphoric acid chemical conversion treatment dissolves titanium compounds such as fluorotitanic acid, phosphoric acid and condensed phosphoric acid, and fluorine compounds such as fluorotitanic acid and hydrofluoric acid described above in water. Adjust. Examples of the method for applying the treatment liquid onto the magnet surface include a dip coating method, a spray method, and a spin coating method. The treatment liquid temperature when applying the treatment liquid is preferably 20 to 80 ° C., and the treatment time is preferably 10 seconds to 20 minutes. The drying temperature after application of the treatment liquid is 50 to 200 ° C. and the drying time is 5 seconds to 1 hour, particularly when applied to a bonded magnet. When performing a zirconium-phosphoric acid type chemical conversion treatment, what is necessary is just to follow the method of a titanium-phosphoric acid type chemical conversion treatment. In the film to be formed, titanium or zirconium has a magnet surface of 1 m.²It is desirable to contain 0.1-100 mg per film formed above.
[0039]
【Example】
Hereinafter, the present invention will be described based on specific examples.
11.7 at% Nd-2.4 at% Dy-6.1 at% B-bal. After obtaining a cast ingot having the composition of Fe, a sintered magnet was obtained by the steps of coarse pulverization, fine pulverization, sintering and heat treatment. This sintered magnet has dimensions of 12 mm in diameter and 2 mm in thickness. When the magnetic properties of the sintered magnet were measured, the residual magnetic flux density Br was 1.27 T, and the coercive force Hcj was 1695 kA / m.
On the other hand, four types (Sn, Zn, Al, Cu) of metal powders shown in Table 1 were prepared as metal powders for film formation on the sintered magnet. These metal powders are manufactured by a gas atomizing method and have a spherical shape. As shown in Table 1, the average particle size of the metal powder is Sn: 40 μm, Zn: 60 μm, Al: 30 μm, Cu: 50 μm. The average particle size of the metal powder was determined by SEM observation of the raw material powder.
[0040]
The above metal powder was jetted onto the sintered magnet as a fluid mixture with high-pressure gas. The conditions for injection are as follows.

Table 1 shows the thickness (film thickness) of the film formed under the above injection conditions. About Example 1-6 and the comparative example, when the magnetic characteristic before a salt spray test was measured, it came to be as described in Table 1. In addition, about Examples 1-6, the magnetic characteristic after film formation was measured (a comparative example does not have a film).
Next, Examples 1 to 6 and Comparative Example were tested up to 100 hours under 5 wt% 35 ° C. salt water spray according to the JIS C 0023 salt spray test method, and the presence or absence of rusting was observed. The results are also shown in Table 1. In addition, about the magnetic characteristic, the magnetic characteristic before and behind a test was compared with the sample which sprayed 5 wt% 35 degreeC salt water for 24 hours.
[0041]
[Table 1]

[0042]
As shown in Table 1, it can be seen that rusting is suppressed as the film thickness increases. In particular, Example 2 in which a film made of Sn powder was formed at 10.2 μm and Example 4 in which a film made of Zn powder was formed at 9.6 μm were dense because no rusting was observed even after 100 hours. It can also be seen that a film with strong adhesion is formed. In this test, no difference in the degree of rusting due to the material of the film was observed.
[0043]
As described above, the magnetic properties before film formation were a residual magnetic flux density Br of 1.27 T and a coercive force Hcj of 1695 kA / m. On the other hand, the magnetic properties after film formation are as shown in Table 1, and it can be said that there is almost no deterioration in magnetic properties due to film formation. Therefore, the film forming method according to this embodiment is desirable for the magnet.
When the magnetic properties before and after the salt spray test are compared, the degree of rusting and the tendency described above agree. That is, Example 2 and Example 4 in which rusting is not observed after 100 hours of the salt spray test have no or slight deterioration in magnetic properties. In Examples 1, 3, 5 and 6 in which rusting was observed in the salt spray test for 24 to 100 hours, a slight deterioration in magnetic properties was observed, but compared with the comparative example in which no film was formed, The degree of deterioration is small.
[0044]
【The invention's effect】
According to the present invention, it is possible to form a corrosion-resistant film on a substrate containing a rare earth metal without using a third component such as a resin or a coupling agent and without reducing the magnetic properties.

Claims (2)

A step of using a spherical metal powder having an average particle size of 30 to 150 μm, produced by a gas atomization method, as a mixed fluid of high-pressure gas;
By injecting the mixed fluid onto the surface of the rare earth sintered magnet from the injection nozzle at an injection pressure of ³ to 10 kg / cm ² , the injected metal powder is brought into close contact with the surface of the rare earth sintered magnet by a mechanochemical reaction. thickness Te is provided with a step that form a film of 1.5～20Myuemu, a,
The rare earth sintered magnet having the film formed on the surface thereof, the rusting does not occur when the salt spray of 5 wt% and 35 ° C. is continued for 24 hours .   The metal powder is composed of one or more of Cu, Fe, Ni, Co, Cr, Sn, Zn, Pb, Cd, In, Au, Ag, and Al. The manufacturing method of the metal member of description.