JP4363480B2 - Rare earth permanent magnet - Google Patents

Description

  The present invention relates to a rare earth permanent magnet having a plating film. In particular, the present invention relates to a rare earth permanent magnet having a plating film with improved adhesion.

Since rare earth permanent magnets such as R—Fe—B permanent magnets (R: rare earth elements including Y) are made of resource-rich and inexpensive materials and have high magnetic properties, It is used in various fields today, and its demand is increasing in recent years.
However, since the R—Fe—B permanent magnet contains a highly reactive rare earth element: R, it is easily oxidized and corroded in the atmosphere. When used without any surface treatment, a slight amount of acid or Corrosion progresses from the surface due to the presence of alkali, moisture, etc., and rust is generated, which causes deterioration and variation in magnet characteristics. Furthermore, when a magnet with rust is incorporated into an apparatus such as a magnetic circuit, the rust may scatter and contaminate peripheral components. In view of the above points, as a surface treatment of a rare earth-based permanent magnet, a rust prevention treatment using a Ni plating film, a Cu plating film or a combination thereof is disclosed in Patent Document 1 and widely used.

  By the way, when a bonded structure in which a rare earth permanent magnet having Ni plating on the outermost surface and another member are bonded with an adhesive is incorporated into various devices, the Ni plating film and the other member are strongly bonded via an adhesive. Is required. However, the Ni plating film may be inferior in adhesiveness to the aluminum film depending on the use situation, and there may be a situation where adhesion failure becomes a problem.

In order to solve this problem, Patent Document 2 proposes a technique of pickling the Ni plating surface with an organic carboxylic acid. This technique is excellent as a method for restoring the adhesion of the Ni plating film.
However, if the bonded structure bonded by the method proposed in Patent Document 2 is left under a moisture resistance test, the bonding strength is lowered. In particular, when a silicone-based adhesive is used as the adhesive, the decrease becomes significant.
JP-A-1-321610 JP 2003-193273 A

  In recent electrical equipment and automotive electrical components, a joined structure in which a magnet and another member are joined with an adhesive is often used. For this reason, in such a joined structure, it is necessary to ensure long-term reliability of adhesive strength. Recently, not only the adhesive strength immediately after bonding of the magnet and other members, but also the bonding strength assuming the case where the bonded structure after bonding is used after being transported in a relatively high temperature and high humidity environment such as shipping. It is also required to guarantee For example, the case where it is calculated | required to determine a specification about the adhesive strength after using for the moisture resistance test (80 degreeC x 90% RH) used with an electrical equipment, an electrical component, etc. is increasing.

  Accordingly, an object of the present invention is to provide a rare earth-based permanent magnet having a film that has excellent corrosion resistance and can be bonded without a decrease in adhesive strength even after an accelerated test such as a moisture resistance test.

  In view of the above points, the present inventor conducted a study on a film that can be bonded without deteriorating the adhesive strength even if an accelerated test such as a moisture resistance test is performed. As a result, an SnCu alloy plated film having a specific composition and film thickness was obtained. Rare earth permanent magnets deposited on the outermost layer of the multilayer plating film are mass-produced because the adhesive strength does not decrease even when the moisture resistance test is performed after bonding to other members with an adhesive, and the plating film hardness is high. The present inventors have found that the above handling is good and have completed the present invention. Specifically, by providing a very thin SnCu alloy film on a plating film including at least one layer of Cu plating film provided on the surface of the rare earth-based permanent magnet body, the adhesive strength after the moisture resistance test is obtained. Adhesion can be performed with little decrease in the thickness.

  The rare earth permanent magnet of the present invention made based on the above knowledge is a rare earth permanent magnet having a multilayer plating film as described in claim 1, wherein the outermost layer of the plating film has a film thickness of 0.1 μm or more and 3 μm. The composition of the SnCu alloy plating film is as follows: Sn is 35 mass% or more and 55 mass% or less, and the balance is substantially Cu, and at least one layer of Cu is formed under the SnCu alloy plating film. It has two or more plating films including a plating film.

  A rare earth permanent magnet according to claim 2 is the rare earth permanent magnet according to claim 1, further comprising a chemical conversion treatment film on the SnCu alloy plating film.

  A bonded structure according to claim 3 is a bonded structure in which another member is bonded to the rare earth permanent magnet according to claim 1 or 2 via a silicone adhesive.

  The bonded structure according to claim 4 is the bonded structure according to claim 3, wherein the rare earth permanent magnet has a ring shape.

  Further, the manufacturing method according to claim 5 includes forming two or more plating films including at least one Cu plating film on the surface of the rare earth based permanent magnet body, and including the at least one Cu plating film. An SnCu alloy plating film having a film thickness of 0.1 μm to 3 μm, a composition of Sn of 35 mass% to 55 mass%, and the balance being substantially Cu is formed on two or more plating films. This is a method for producing a rare earth permanent magnet.

  The manufacturing method according to claim 6 is the method of manufacturing a rare earth permanent magnet according to claim 5, wherein the SnCu plating film is formed on the two or more plating films including the at least one Cu plating film. The SnCu alloy plating film is formed after pretreatment with hydrochloric acid or sulfuric acid in the previous step.

  The manufacturing method according to claim 7 is characterized in that, in the manufacturing method of the rare earth permanent magnet according to claim 5 or 6, chemical conversion treatment with phosphoric acid or phosphate is further performed on the SnCu alloy plating film. And

  According to the present invention, the rare earth permanent magnet and another member are bonded using an adhesive by having the SnCu alloy plating film on the outermost layer of the multilayer plating film formed on the surface of the rare earth permanent magnet body. The bonded structure can maintain high adhesive strength even after the moisture resistance test.

  The rare earth permanent magnet of the present invention is a rare earth permanent magnet having a multilayer plating film of two or more layers, and the outermost layer of the plating film is a SnCu alloy plating film.

Details of the present invention will be described below.
The composition of the plating film is desirably 35 mass% (22.3 atomic%) or more and 55 mass% (39.5 atomic%) or less, and more desirably 40 mass% or more and 50 mass% or less. When Sn is less than 35 mass%, corrosion tends to occur due to an increase in the Cu ratio. On the other hand, if Sn exceeds 55 mass%, the hardness of the plating film itself rapidly decreases as the Sn ratio increases, and the film is easily damaged.

The SnCu alloy having the above composition is highly brittle, and as the film thickness increases, there is a problem that peeling occurs inside the film, or protrusions are generated on the film surface, and the protrusions are peeled off during handling. Peeling and protrusion are likely to occur when the film thickness exceeds 3 μm. For this reason, the film thickness of the SnCu plating is preferably 3 μm or less, and more preferably 2 μm or less. In addition, since the SnCu alloy is non-magnetic, it is preferable that the thickness of the plating film is as thin as possible in order to develop the original magnetic characteristics of the rare earth permanent magnet. The effect of improving the adhesion of the SnCu alloy plating film can be sufficiently obtained if it is 0.1 μm or more, and more preferably 0.2 μm or more and 2 μm or less.
In order to suppress the generation of protrusions, it is desirable that the base of SnCu plating is smooth. As for the smoothness of the base plating, the surface roughness Rmax is desirably 0.5 to 15 μm, more desirably 0.5 to 10 μm, and further desirably 0.5 to 5 μm.

  The SnCu alloy plating film may be subjected to chemical conversion treatment using sodium phosphate phosphate or the like. The chemical conversion treatment may be performed by, for example, immersing in a sodium phosphate solution having a concentration of 10 g / L or more and 30 g / L or less and a liquid temperature of 20 ° C., followed by washing and drying. By performing such a chemical conversion treatment, discoloration of the SnCu alloy plating film can be suppressed without lowering the adhesiveness.

For example, in the case of an R—Fe—B permanent magnet, the rare earth permanent magnet has a very small linear expansion coefficient of 5 × 10 ⁻⁶ in the C // direction and −1.5 × 10 ^{−6 in the} C⊥ direction. Therefore, the bonded structure is bonded to another member such as an iron-based material having a large linear expansion coefficient (for example, iron has a linear expansion coefficient of 12 × 10 ⁻⁶ ) and an adhesive having a high hardness such as an epoxy-based adhesive. May cause cracks in the magnet due to stress generated from the difference in coefficient of linear expansion during heat curing. This phenomenon is remarkable when an iron-based yoke is inserted into the inner diameter of an R-Fe-B ring magnet and an adhesive is applied to form a rotor for a motor. The material expands and causes magnet breakage. As a countermeasure, a silicone adhesive having a low hardness is widely used as an adhesive.
Industrially, an addition reaction type silicone adhesive which is cured in a relatively short time is often used. Silicone-based adhesives absorb such stress and are less likely to crack the magnet. However, the bonding structure produced using a silicone-based adhesive has a sharp decrease in adhesive strength due to a high-temperature and high-humidity environment, particularly in the case of a rare-earth permanent magnet having a Ni plating film on the outermost layer of the magnet body. Is remarkable. The bonded structure in which the rare earth permanent magnet having the SnCu alloy plating film of the present invention as the outermost layer is bonded to another member using a silicone adhesive solves this problem, and the adhesive strength decreases even after the moisture resistance test. Therefore, stable adhesive strength can be ensured over a long period of time.
Moreover, even if it adhere | attaches after providing for a moisture-proof test before bonding as a joining structure body and measures adhesive strength, intensity | strength does not fall compared with the thing which does not use for a moisture-proof test.

Before the SnCu alloy plating is performed, an activation treatment with an acid is performed on the underlying plating film, whereby the adhesion between the underlying plating film and the SnCu plating can be further improved and stable production can be achieved. Alkaline treatment has a degreasing effect, but activation is not sufficient, and alkali treatment is difficult to wash with water, tends to remain as a residual on the surface, and peeling may occur between the underlying plating. As the acid, hydrochloric acid or sulfuric acid is preferable. The concentration of hydrochloric acid is preferably 10 vol% or more and 50 vol% or less. If it is less than 10 vol%, sufficient activation cannot be achieved, and if it exceeds 50 vol%, the adhesion may be lowered due to discoloration of Ni plating.
When sulfuric acid is used, it may be used in the same concentration range as hydrochloric acid.
As acids other than hydrochloric acid and sulfuric acid, organic acids such as oxalic acid and phosphoric acid can also be suitably used. In particular, when using a pyrophosphate-based plating solution for SnCu alloy plating, if phosphoric acid, polyphosphoric acid, or the like is used as the acid used for activation, even if the acid activation is performed without washing with water, Adhesion is improved with little influence on the SnCu plating solution in the subsequent process.

  As the plating bath for SnCu alloy plating, a known bath can be used as long as a film having the above composition is formed. For example, a pyrophosphate bath, a cyan bath, an acid bath, and the like. Incidentally, a Cu—Sn alloy plating technique that does not use extremely toxic cyan is introduced in Japanese Patent Application Laid-Open No. 2004-10907, and it is preferable to use such a bath.

Moreover, also about the conditions of plating, the arbitrary conditions which can be controlled to the composition range of Claim 5 can be used.
For the plating method, barrel plating or rack plating can be used as appropriate.However, when the rare earth permanent magnet to be plated has a ring shape, the current is less likely to concentrate on the outer diameter of the ring, and the film thicknesses of the outer diameter portion and inner diameter portion are reduced. Rack plating is desirable because it is easy to make uniform. Current density type plating solution SnCu alloy plating, barrel plating, can be appropriately selected by methods of the rack plating plating, 0.1 A / dm is preferably ² or more 10A / dm ² or less, 0.5A / dm ² or more 5A / Dm ² or less is more preferable.

  Evaluation of wettability is used as one of the indexes for knowing good adhesiveness. This evaluation method is a method for examining the wettability of the surface of the specimen using a wet tension test solution, and it is said that the higher the index is, the better the adhesion is generally. The rare earth-based permanent magnet of the present invention is not only reduced in adhesive strength even if it is subjected to the moisture resistance test after being bonded to another member with an adhesive, but also heated even if the surface is oxidized before bonding to the other member. The adhesiveness can be easily recovered by the treatment. When the rare earth permanent magnet of the present invention is stored for a long time without adhering other members and the wettability of the plating film surface is lowered, a heat treatment test at 150 ° C. × 90 minutes is performed. When the evaluation was performed using the wet tension test solution, it was confirmed that the index for evaluating the wettability recovered to 73 mN / m after the test with respect to 40 mN / m before the test. In mass production, in order to suppress surface oxidation after plating, oxidation resistance treatment such as chemical conversion treatment or vacuum storage (vacuum pack etc.) is often performed at the time of shipment. However, in the rare earth permanent magnet of the present invention, it is not always necessary to perform the oxidation resistance treatment or the like if the adhesive recovery treatment by the heat treatment is performed from the viewpoint of ensuring the adhesion.

  The base of the SnCu alloy plating film is a two or more layers plating film including at least one layer of a Cu plating film. In order to improve corrosion resistance, a plating film having two or more layers in combination with a Ni plating film is desirable.

Below, the desirable form of the base plating of SnCu plating is shown.
For the Cu plating, a plating bath such as a pyrophosphate bath, a sulfuric acid bath, a cyan bath, and an electroless bath can be selected. Above all, electric field Cu plating using a pyrophosphoric acid bath is excellent in electrical conductivity, flexibility, and spreadability, and has good film throwing power. For this reason, electroplating with a pyrophosphoric acid bath can be used suitably for plating of a ring-shaped object. The film throwing power here refers to the ability of the plating to cover the material, for example, the ability of the plating to adhere to a portion where the current density becomes low, such as the concave portion of the object to be plated and the inner diameter portion of the ring magnet. .
Electroplating using a pyrophosphoric acid bath has no cell structure and is excellent in smoothness, and the smoothness of SnCu plating plated thereon can be maintained.

  In the case of performing electroplating using a Cu pyrophosphate bath, it is preferable to further include a conductive protective layer as an underlayer. Since the pyrophosphoric acid Cu bath contains a large amount of free Cu ions in the bath, when an R—Fe—B magnet is directly immersed in the pyrophosphoric acid bath, it is electrically connected to an electrically base metal such as Fe constituting the surface of the magnet. In addition, there is a possibility that a Cu film having poor adhesion is formed on the surface of the magnet due to a substitution plating reaction with noble Cu. For this reason, as the base of the plating film using the Cu pyrophosphate bath, an electric field Ni plating film and an electric field Cu plating film using a cyan bath that can form a plating film having excellent adhesion directly on the surface of the R-Fe-B magnet body are desirable. In particular, a Ni plating film that is easy to handle and excellent in stability is desirable.

Since the Cu plating film is easily oxidized in the atmosphere, it is more preferable in terms of corrosion resistance to perform Ni plating on the Cu plating film and further to perform SnCu plating.
In the case of Ni plating, a plating bath such as a watt bath, a sulfamic acid bath, or a neutral bath is used for electroplating. Also, electroless plating with high film thickness uniformity can be performed.
In addition, Ni plating coated on Cu pyrophosphate plating has excellent surface smoothness and can maintain the smoothness of SnCu plating coated on it, thus preventing the plating film from falling off during handling. it can.
The plating method for Ni plating and Cu plating may be selected depending on the shape, weight, and size of the object to be plated, such as barrel plating or rack plating.
However, when the rare earth permanent magnet has a ring shape, rack plating is desirable because current hardly concentrates on the outer diameter of the ring and the film thickness of the outer diameter portion and the inner diameter portion can be made uniform.
The type of current density plating solution when selecting the electroplating, may be determined by the plating method, 0.1 A / dm ² or more 10A / dm ² or less is preferable, 0.5A / dm ² or more 5A / dm ² or less is more preferable.

  In addition, if the base plating of SnCu plating includes at least one layer of Cu plating and has two or more layers, the configuration thereof is arbitrary and is not limited to the configuration of the example.

  Arbitrary methods can be used as pre-plating treatment of the magnet, and mixed acid of nitric acid and other acids, sulfuric acid, hydrochloric acid, organic acid, etc., and electrolytic etching can also be selected.

  The present invention can be applied to all known rare earth permanent magnets as long as they can be plated. For example, it can be applied to both sintered magnets and bonded magnets. Moreover, the composition is applicable not only to R—Fe—B permanent magnets but also to R—Co permanent magnets and R—Fe—N permanent magnets.

A method for producing an R—Fe—B permanent magnet by powder metallurgy will be described. The composition is, for example, R: 24 mass% or more and 34 mass% or less (R is at least one kind of rare earth elements including Y, and the total of R, Fe, and B as the main components is Nd, Dy, and Pr. At least one kind is necessarily included), B: 0.6 mass% to 1.8 mass%, Fe: the balance. Fe may be partially substituted with Co, and may contain additive elements such as Al, Si, Cu, Ga, Nb, Mo, and W of about 3 mass% or less.
When R is less than 24 mass%, the residual magnetic flux density B _r and the coercive force H _cJ are reduced among the magnetic characteristics. On the other hand, if it exceeds 34 mass%, the amount of rare earth-rich phase inside the sintered body increases, and the form becomes coarse and the corrosion resistance decreases. B: When less than 0.6 mass%, the amount of B necessary for forming the main phase R ₂ Fe ₁₄ B phase is insufficient, and the R ₂ Fe ₁₄ phase having soft magnetic properties is generated and the holding power is reduced. To do. On the other hand, when the amount of B exceeds 1.8 mass%, the phase rich in B which is a nonmagnetic phase increases and the residual magnetic flux density Br decreases.

  The pulverization is divided into coarse pulverization and fine pulverization, and the coarse pulverization is preferably performed by a stamp mill, a jaw crusher, a brown mill, a disk mill or the like or a hydrogen storage method. The fine pulverization is preferably performed by a jet mill, a vibration mill, a ball mill or the like. In order to prevent oxidation, it is preferable to carry out in a non-oxidizing atmosphere using an organic solvent or an inert gas. The pulverized particle size is preferably 2 to 8 μm (FSSS). If it is less than 2 μm, the activity of the magnetic powder is high, so that it is easily oxidized. Deformation during sintering is large and magnetic properties are also deteriorated. If it exceeds 8 μm, the crystal grain size obtained after sintering becomes large and magnetization reversal occurs easily, leading to a decrease in coercive force.

Molding is performed in a magnetic field.
The magnetic field strength is preferably 159 kA / m or more, more preferably 239 kA / m or more. If it is less than 159 kA / m, the orientation of the magnetic powder is insufficient, and the necessary magnetic properties cannot be obtained. The molding pressure is preferably 0.5 to ² ton / cm ² . If it is less than 0.5 ton / cm ² , the strength of the compact is weak and easily broken. On the other hand, if it is more than ² ton / cm ² , the orientation of the magnetic powder is disturbed and the magnetic properties are deteriorated. Sintering is preferably performed at 1000 to 1150 ° C. in a vacuum or argon atmosphere. If it is less than 1000 ° C., the required density cannot be obtained due to insufficient sintering, and the magnetic properties are deteriorated. Above 1150 ° C, oversintering causes deformation and deterioration of magnetic properties.
After sintering, heat treatment and processing are performed. The processing can also be performed before the heat treatment.

Hereinafter, the present invention will be described in more detail by way of examples. The present invention is not construed as being limited to this.
<Production of magnet>
(Example 1)
By a known method, an Nd-Dy-Fe-Al-B based sintered magnet body having (Nd, Dy) ₂ (Fe) ₁₄ B type intermetallic compound as a main phase was produced. The magnetic properties of this sintered magnet body at room temperature were B _r = 1.2 T (12 kG), H _cJ = 1989 kA / m (25 kOe), (BH) _max = 280 kJ / m ³ (35 MGOe). Next, the sintered magnet body was processed into a rectangular parallelepiped shape of 30 mm × 15 mm × 3 mm and then subjected to barrel polishing.
The polished sintered magnet body was dipped in a water-soluble rust preventive, heated to about 60 ° C. and dried. The sample thus obtained was subjected to a first pretreatment with 5 vol% nitric acid as a pretreatment for plating, followed by a second pretreatment with a mixed acid of 10 vol% hydrogen peroxide and 25 vol% acetic acid, and then Ni—Cu—Ni3 in the following order. A layer plating film was formed.
[1st layer Ni plating film]
Plating bath: Watt bath (Ni sulfate 300g / L, Ni chloride 50g / L, Boric acid 50g / L)
Bath temperature: 50 ° C
Current density: 1 A / dm ²
Film thickness: 3 μm Washed with water after film formation.
[Second layer Cu plating film]
Plating bath: Cu pyrophosphate (Cu pyrophosphate Cu 80 g / L, metal Cu 30 g / L, potassium pyrophosphate 300 g / L, ammonia 2 ml / L, brightener (Okuno Pharmaceutical Pyrotop PC) 1 ml / L)
Bath temperature: 55 ° C
Current density: 1 A / dm ²
Film thickness: 7 μm Washed with water after film formation.
[3rd layer Ni plating film]
Plating bath: Watt bath (Ni sulfate 300g / L, Ni chloride 50g / L, Boric acid 50g / L, Brightener (saccharin) 10ml / L)
Bath temperature: 50 ° C
Current density: 1A / dm ²
Thickness 5 μm Washed with water after film formation.
An SnCu alloy plating film was formed on the surface of the sintered magnet body having the Ni—Cu—Ni three-layer plating film formed as described above under the following conditions to obtain the rare earth permanent magnet of the present invention.
SnCu plating bath: stannous pyrophosphate 20 g / L, Cu pyrophosphate 10 g / L, potassium pyrophosphate 180 g / L, brightener, cationic surfactant, surface tension modifier, bath stabilizer, etc. Bath temperature: 20 ° C.
Current density: 1 A / dm ²
Thickness 1 μm Washed and dried after film formation.
The composition of SnCu was Cu: Sn = 55: 45 mass%.

(Example 2)
A rare earth-based permanent magnet having a multilayer plating film was prepared in the same manner as in Example 1 except that the thickness of SnCu was 0.1 μm.

(Example 3)
A rare earth-based permanent magnet having a multilayer plating film was prepared in the same manner as in Example 1 except that the thickness of SnCu was 0.2 μm.

Example 4
A rare earth-based permanent magnet having a multilayer plating film was prepared in the same manner as in Example 1 except that the thickness of SnCu was 2 μm.

(Example 5)
A rare earth permanent magnet having a multilayer plating film was produced in the same manner as in Example 1 except that the thickness of SnCu was 3 μm.

(Example 6)
The same sintered magnet body as used in Example 1 is pretreated by the same method as in Example 1, and the first Ni plating film is formed by the same method as in Example 1, and then the film thickness is increased. A rare earth-based permanent magnet having a Ni—Cu two-layer plating film was produced by forming a second-layer Cu plating film by the same method as in Example 1 except that the thickness was set to 12 μm.
An SnCu alloy plating film was formed on the surface of the sintered magnet body having the Ni—Cu bilayer plating film formed as described above under the same conditions as in Example 1 to obtain the rare earth permanent magnet of the present invention.

(Example 7)
A rare earth permanent magnet having a multilayer plating film was prepared in the same manner as in Example 1, and then immersed in a solution of 10 g / L of sodium tertiary phosphate for 3 minutes, washed with water and dried.

(Example 8)
In the same manner as in Example 1, a Ni—Cu—Ni three-layer plating film was formed, and then
It was immersed in 10 vol% hydrochloric acid and washed with water.
On the surface of the sintered magnet body having the Ni—Cu—Ni three-layer plating film formed as described above, a SnCu alloy plating film was formed under the same conditions as in Example 1 to obtain the rare earth permanent magnet of the present invention. It was.

Example 9
A rare earth-based permanent magnet having a multilayer plating film was prepared in the same manner as in Example 1 except that the liquid composition of SnCu plating was adjusted to be film composition Cu: Sn = 65: 35 mass%.

(Example 10)
A rare earth-based permanent magnet having a multilayer plating film was produced in the same manner as in Example 1 except that the liquid composition of SnCu plating was adjusted so that the film composition was Cu: Sn = 45: 55 mass%.

Example 11
In the same manner as in Example 1, a Ni—Cu—Ni three-layer plating film was formed, and then
It was immersed in 10 vol% sulfuric acid and washed with water.
On the surface of the sintered magnet body having the Ni—Cu—Ni three-layer plating film formed as described above, a SnCu alloy plating film was formed under the same conditions as in Example 1 to obtain the rare earth permanent magnet of the present invention. The

Example 12
In the same manner as in Example 1, a Ni—Cu—Ni three-layer plating film was formed, then diluted with water and immersed in polyphosphoric acid adjusted to pH 1.3. Thereafter, an SnCu alloy plating film was formed under the same conditions as in Example 1 except that the SnCu plating was performed without washing with water to obtain the rare earth permanent magnet of the present invention.

(Comparative Example 1)
A rare earth permanent magnet having a multilayer plating film was produced in the same manner as in Example 1 except that the thickness of SnCu was 5 μm.

(Comparative Example 2)
A rare earth permanent magnet having a Ni—Cu—Ni three-layer plating film was prepared in the same manner as in Example 1, washed with 10 vol% sulfuric acid, washed with water, further washed with 10 mass% caustic soda, washed with water, and then dried.

(Comparative Example 3)
A rare earth permanent magnet having a multilayer plating film was produced in the same manner as in Example 1 except that the liquid composition of SnCu plating was adjusted to make the film composition Cu: Sn = 80: 20 mass%. Since the ratio of Cu is high, rust prevention treatment was performed with benzotriazole in order to prevent discoloration.

(Comparative Example 4)
A rare earth-based permanent magnet having a multilayer plating film was produced in the same manner as in Example 1 except that the liquid composition of SnCu plating was adjusted so that the film composition was Cu: Sn = 30: 70 mass%.

(Comparative Example 5)
A rare earth-based permanent magnet having a multilayer plating film was produced in the same manner as in Example 1 except that the liquid composition of SnCu plating was adjusted so that the film composition was Cu: Sn = 10: 90 mass%.

(Comparative Example 6)
The same sintered magnet body as used in Example 1 was pretreated by the same method as in Example 1, and the first Ni plating film was formed in the same manner as in Example 1, and the film thickness was increased. A second-layer Cu plating film was formed in the same manner as in Example 1 except that the thickness was 12 μm, and a rare earth permanent magnet having a Ni—Cu two-layer plating film was produced.
Thereafter, it was washed with 10 vol% sulfuric acid, washed with water, and then subjected to rust prevention treatment with benzotriazole.

(Comparative Example 7)
A Ni—Cu—Ni three-layer plating film was formed in the same manner as in Example 1, and then immersed in a 3 g / L oxalic acid solution (20 ° C.) for 3 minutes, washed with water and dried.

(Comparative Example 8)
A rare earth-based permanent magnet having a multilayer plating film was produced in the same manner as in Example 1 except that the liquid composition of SnCu plating was adjusted so that the film composition was Cu: Sn = 67: 33 mass%. Since the completed film had many copper components and the color tone was brass, it was washed with 10 vol% sulfuric acid, washed with water, and then subjected to rust prevention treatment with benzotriazole.

(Comparative Example 9)
A rare earth-based permanent magnet having a multilayer plating film was produced in the same manner as in Example 1 except that the liquid composition of SnCu plating was adjusted to be film composition Cu: Sn = 40: 60 mass%.

(Comparative Example 10)
A rare earth permanent magnet having a multilayer plating film was produced in the same manner as in Example 1 except that the thickness of SnCu was 3.5 μm.

(Comparative Example 11)
A rare earth-based permanent magnet having a multilayer plating film was produced in the same manner as in Example 1 except that the thickness of SnCu was 4 μm.

(Comparative Example 12)
A rare earth-based permanent magnet having a multilayer plating film was produced in the same manner as in Example 1 except that the thickness of SnCu was 0.05 μm.

(Comparative Example 13)
In the same manner as in Example 1, a Ni—Cu—Ni three-layer plating film was formed, and then
It was immersed in 100 g / L caustic soda and washed with water.
On the surface of the sintered magnet body having the Ni—Cu—Ni three-layer plating film formed as described above, a SnCu alloy plating film was formed under the same conditions as in Example 1 to obtain the rare earth permanent magnet of the present invention. The

<Adhesion test>
Magnets produced in Examples 1 to 12 and Comparative Examples 1 to 13 were applied to a yoke made of SUS304 using a silicone adhesive (SE1750 manufactured by Toray Dow Corning: an addition reaction type silicone adhesive). A bonded structure was produced by bonding. Curing conditions were 150 ° C. × 90 minutes (the temperature was measured with a contact-type thermometer), and 10 bonded structures were produced for each condition. Of these, 5 were measured for compressive shear strength immediately after bonding, and the remaining 5 were measured for compressive shear strength after a high temperature and high humidity 80 ° C. × 90% × 24 hour humidity resistance test (both bonded structures at room temperature). The compression shear strength was measured in the returned state). The compressive shear strength was measured using TOYO BALDWIN (TENSILON UTM-I-5000C). The compression speed was 1.5 mm / min. Further, the state of the adhesive on the peeled surface after the test and the presence / absence of handling scratches accompanying the test were visually observed. The test results are shown in Table 1. In the table, the adhesive strength (compressive shear strength) is an average value of the measured values of 5 pieces each.
About Examples 1-11, since the adhesive strength showed favorable adhesive strength immediately after adhesion | attachment and after a moisture resistance test, and peeling of an adhesive agent also became the whole surface cohesive failure, the rare earth-type permanent magnet of this invention uses an adhesive agent. Thus, it was found that even when a moisture resistance test was performed after bonding with another member, the decrease in the bonding strength was small.
In addition, after the test, no scratch was generated in other parts (excluding the adhesive surface) subjected to the test.
In Comparative Example 1, the film was highly brittle, and the SnCu film was broken after the adhesion and the moisture resistance test, and partial peeling of the SnCu film was observed.
In Comparative Examples 2 and 3, the adhesive strength immediately after bonding was high, and the peeling mode was also cohesive failure, but after the moisture resistance test, the strength decreased sharply, resulting in interfacial peeling with no adhesive remaining on the magnet surface. . In Comparative Examples 4, 5, and 9, there was no problem with adhesiveness, but scratches due to handling such as adhesion occurred. Such a flaw reduces the product value of the rare earth permanent magnet, for example, causes damage to the film or lowers the dimensional accuracy, and causes a complicated handling in mass production. In Comparative Examples 6, 7, and 8, the adhesive strength immediately after bonding was high, and the peeling mode was also cohesive failure, but the adhesive strength decreased after the moisture resistance test, and no adhesive remained on the magnet side, resulting in interfacial peeling. It was.
In Comparative Examples 10 and 11, the adhesive strength was low immediately after bonding and after the moisture resistance test, and partial peeling of the film was observed.
As for Comparative Example 12, the adhesive strength immediately after bonding was high, and peeling also resulted in cohesive failure. However, after the moisture resistance test, the peeling was due to interface peeling on the magnet side, and the adhesive strength was lowered. When the film thickness of SnCu was 0.05 μm, the effect of improving the adhesiveness was not recognized.
About Comparative Example 13, 1/5 pieces and partial peeling of SnCu plating were observed in the adhesion strength test immediately after bonding. In the moisture resistance test, partial peeling of SnCu plating was observed in 2/5 pieces.
It is thought that a film with poor adhesion was formed because the plating was performed while the residual of the treatment with caustic soda before SnCu plating remained.

(Example 13)
A ring-type sintered magnet body having a radial orientation of Nd—Dy—Fe—Al—B system having (Nd, Dy) ₂ (Fe) ₁₄ B type intermetallic compound as a main phase was prepared by a known method. The magnetic properties of this permanent magnet body at room temperature were Br = 1.2T (12 kG), Hcj = 1989 kA / m (25 kOe), (BH) max = 280 kJ / m ³ (35 MGOe).
The ring-type sintered magnet body was processed to obtain a magnet material having an outer diameter of 40 mm, an inner diameter of 33 mm, and a height of 13.5 mm. After dipping in an antirust agent and drying, plating was performed under the same conditions as in Example 1 to obtain a ring-type sintered magnet body having a SnCu alloy plating film on the Ni-Cu-Ni three-layer plating film. About the film thickness of the SnCu alloy plating film, the inner diameter part of the magnet was measured.

SUS304 adhesive strength measuring yokes made of SUS304 each having a diameter of 32.9 mm were bonded to the inner diameter portion of the ring-shaped sintered magnet body, thereby producing 10 bonded structures of the present invention. This bonded structure was heat-cured at 150 ° C. for 90 minutes using a silicone-based adhesive (SE1750 manufactured by Toray Dow Corning).
The same bonded structure as in Example 13 was produced except that a heat-curable epoxy adhesive was used as the adhesive and heat-cured at 150 ° C. for 90 minutes to obtain Comparative Example 14.
When each bonded structure was visually confirmed after curing, no cracks occurred in the ring-type sintered magnet body in Example 13, but cracks occurred in Comparative Example 14 due to the difference in linear expansion coefficient. It was. The visual results are shown in Table 2.
Of the bonded structures of Example 13, five were measured for compressive shear strength immediately after bonding. The remaining five samples were measured for compressive shear strength after a high temperature and high humidity 80 ° C. × 90% × 24 hour humidity resistance test. In addition, the compressive shear strength was measured using TOYO BALDWIN (TENSILON UTM-I-5000C). The compression speed was 1.5 mm / min. Moreover, it observed about the state of the adhesive agent of the peeling surface after a test.
The compressive shear strength is measured by mounting a bonded structure comprising the ring-type sintered magnet body 2 and the adhesive strength measuring yoke 1 on an adhesive strength measuring jig 3 shown in FIG. 1 for fixing only the ring-type sintered magnet body. As shown in FIG. 2, a predetermined pressure was applied in the direction of the white arrow. As a result, even after the moisture resistance test, the decrease in the adhesive strength was small, and the peeled surface was a cohesive failure surface of the adhesive. In the table, the adhesive strength (compressive shear strength) is an average value of the measured values of 5 pieces each.

(Example 14)
Five additional bonded structures identical to Example 13 were prepared and subjected to a moisture resistance test of 80 ° C. × 90% × 1000 hours, and then the same compressive shear strength as above was measured.
The joint structure subjected to the moisture resistance test had an adhesive strength (average value of 5 measured values of compression shear strength) of 4.3 MPa, and the moisture resistance test (80 ° C. × 90% ×) measured in Example 12. Compared with the adhesive strength of 4.8 MPa after 24 hours), the decrease in the adhesive strength was slight. Moreover, although the peeling mode of the adhesive on the peeled surface was confirmed, it was cohesive failure of the adhesive for all samples.
In addition, the rare earth permanent magnet after the moisture resistance test showed good corrosion resistance without observing peeling of the plating film or swelling of the plating film.

(Example 15)
A ring-type sintered magnet body having a radial orientation of Nd—Dy—Fe—Al—B system having (Nd, Dy) ₂ (Fe) ₁₄ B type intermetallic compound as a main phase was prepared by a known method. The magnetic properties of this permanent magnet body at room temperature were Br = 1.2T (12 kG), Hcj = 1989 kA / m (25 kOe), (BH) max = 280 kJ / m ³ (35 MGOe).
The ring-type sintered magnet body was processed to obtain a magnet material having an outer diameter of 40 mm, an inner diameter of 33 mm, and a height of 13.5 mm. After dipping in a rust inhibitor and drying, plating is performed under the same conditions as in Example 1, and a 1 μm thick SnCu alloy plating layer is formed on the Ni—Cu—Ni three-layer plating film (the thickness of each layer is the same as in Example 1). A ring-type sintered magnet body having a film was obtained. About the film thickness of the SnCu alloy plating film, the inner diameter part of the magnet was measured.
The ring-type sintered magnet body was subjected to a moisture resistance test at 30 ° C. × 70% × 500 hours, and then the inner diameter portion of the ring-type sintered magnet body was made of SUS304 having a diameter of 32.9 mm. Were bonded to produce 10 bonded structures of the present invention. This bonded structure was heat-cured at 150 ° C. for 90 minutes using a silicone-based adhesive (SE1750 manufactured by Toray Dow Corning).
30 ° C. × 70% was determined from the average temperature and average humidity of 25.4 ° C. and 70.6% from June to August in Kumagaya City from 2004 to 2006.
The change in the surface oxidation of the SnCu plating from 0 hour to 500 hours is shown in FIG.
After the adhesion, the compression shear strength was measured after 5 pieces and after the moisture resistance test at 80 ° C. × 90% × 24 hours.
The measurement result of the shear strength was an average of 5 pieces.
As a result, the shear strength after bonding was 4.9 Mpa. The shear strength after the moisture resistance test was 4.8 Mpa, and there was almost no decrease in the shear strength. As a result of visual confirmation, the peeled surface was a cohesive failure of the entire surface of the adhesive both after adhesion and after the moisture resistance test.
The ring-type sintered magnet body was analyzed by ESCA (Shimadzu-850) for surface analysis after 30 ° C. × 70% × 0 hour, 24 hours, 250 hours, and 500 hours.
The analysis results are shown in Table 3.
Surface oxidation did not proceed from 0 to 500 hours. Even when exposed to a corrosive environment due to the stable oxidation resistance of SnCu plating, it is considered that there is little decrease in adhesive strength.

(Example 16)
A ring-type sintered magnet body having a radial orientation of Nd—Dy—Fe—Al—B system having (Nd, Dy) ₂ (Fe) ₁₄ B type intermetallic compound as a main phase was prepared by a known method. The magnetic properties of this permanent magnet body at room temperature were Br = 1.2T (12 kG), Hcj = 1989 kA / m (25 kOe), (BH) max = 280 kJ / m ³ (35 MGOe).
The ring-type sintered magnet body was processed to obtain a magnet material having an outer diameter of 40 mm, an inner diameter of 33 mm, and a height of 13.5 mm. After dipping in a rust inhibitor and drying, plating is performed under the same conditions as in Example 1, and a 1 μm thick SnCu alloy plating layer is formed on the Ni—Cu—Ni three-layer plating film (the thickness of each layer is the same as in Example 1). A ring-type sintered magnet body having a film was obtained. About the film thickness of the SnCu alloy plating film, the inner diameter part of the magnet was measured.
After subjecting the ring-type sintered magnet body to a moisture resistance test at 80 ° C. × 90% × 24 hours, the ring-type sintered magnet body has a 32.9 mm diameter SUS304 adhesive strength measuring yoke. Were bonded to produce 10 bonded structures of the present invention. This bonded structure was heat-cured at 150 ° C. for 90 minutes using a silicone-based adhesive (SE1750 manufactured by Toray Dow Corning).
After the adhesion, the compression shear strength was measured after 5 pieces and after the moisture resistance test at 80 ° C. × 90% × 24 hours.
The measurement result of the shear strength was an average of 5 pieces.
As a result, the shear strength after bonding was 5.0 Mpa. The shear strength after the moisture resistance test was 4.9 Mpa, and there was almost no decrease in the shear strength. As a result of visual confirmation, the peeled surface was a cohesive failure of the entire surface of the adhesive both after adhesion and after the moisture resistance test.

The present invention provides a rare earth-based permanent magnet having a plating film with little decrease in adhesive strength even when a moisture resistance test is performed after bonding to another member using an adhesive. Even in the case of bonding using a system adhesive, industrial applicability is great in that it can provide a bonded structure having a long-term reliable adhesion improving effect without cracking during bonding.

Top view and side view showing adhesive strength measurement jig Perspective explanatory view showing the state during compression shear strength measurement

Explanation of symbols

1 Yoke for measuring adhesive strength
2 Ring-type sintered magnet body
3 Adhesive strength measurement jig

Claims (7)

A rare earth-based permanent magnet having a multilayer plating film, wherein the outermost layer of the plating film is a SnCu alloy plating film having a film thickness of 0.1 μm or more and 3 μm or less, and the composition of the SnCu alloy plating film is Sn 35 mass% or more and 55 mass %, And the balance is substantially Cu, and has two or more plated films including at least one Cu plated film under the SnCu alloy plated film. The rare earth-based permanent magnet according to claim 1, further comprising a chemical conversion treatment film on an upper layer of the SnCu alloy plating film. A joined structure in which another member is joined to the rare earth permanent magnet according to claim 1 or 2 via a silicone adhesive. The bonded structure according to claim 3, wherein the rare earth-based permanent magnet has a ring shape. Two or more plating films including at least one Cu plating film are formed on the surface of the rare earth based permanent magnet body, and a film thickness of 0. 2 is formed on the two or more plating films including the one or more Cu plating film. A method for producing a rare earth-based permanent magnet, comprising forming a SnCu alloy plating film having a composition of 1 to 3 μm, Sn of 35 to 55 mass%, and the balance being substantially Cu. The SnCu alloy plating film is formed after a pretreatment with hydrochloric acid or sulfuric acid is performed on the plating film including two or more layers including the Cu plating film of one layer or more in a step before the SnCu plating film formation. The method for producing a rare earth based permanent magnet according to claim 5, wherein the method is characterized in that: 7. The method for producing a rare earth based permanent magnet according to claim 5, wherein a chemical conversion treatment with phosphoric acid or a phosphate is further performed on the SnCu alloy plating film.

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