JP2001250707A - Permanent magnet material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a permanent magnet material of R-Fe-B composition (R denotes a rare earth element) which is enhanced in magnetic characteristics and corrosion resistance by a method wherein a plated film is improved in adhesion and corrosion resistance. SOLUTION: A Zn plating layer or a Zn alloy plating layer is formed on the surface of a sintered magnet material, and then an Ni plating layer or an Ni alloy plating layer is deposited thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth sintered permanent magnet having an R--Fe--B composition (R is a rare earth element), and more particularly to a permanent magnet material having high magnetic properties and excellent corrosion resistance. About.

[0002]

2. Description of the Related Art Rare-earth sintered permanent magnets having an R-Fe-B composition, and among them, rare-earth sintered permanent magnets having an Nd-Fe-B composition have extremely excellent magnetic properties, and particularly have a maximum energy. The product surpasses SmCo-based magnets,
High-performance magnets exceeding 0MGOe have been mass-produced and are playing an active role as functional materials indispensable in the current information electronics society.

[0003] In recent years, electronic devices such as computer-related devices, CD players, mini disk systems, and mobile phones using magnets have been reduced in size, weight, density, capacity, performance, power and energy savings. With, R-
Rare-earth permanent magnets of Fe-B composition, especially Nd-F
There has been a demand for smaller and thinner sintered magnets having an EB composition.

[0004] In order to process the R-Fe-B based sintered magnet into a smaller or thinner practical shape and mount it on a magnetic circuit, it is necessary to cut, grind or polish the molded and sintered block-shaped sintered magnet. It is necessary to machine such as a wire saw, a cutting machine such as a wire saw, a surface grinding machine, a centerless polishing machine, a lapping machine and the like.

However, when the above-described processing is performed, the rare-earth sintered permanent magnet having the R—Fe—B composition has an oxide or hydrate on the surface of the permanent magnet due to the presence of a small amount of water (steam), acid, or alkali. Things are formed and corrosion begins. Thereafter, the electrochemical corrosion progresses to the inside of the magnet with the passage of time, the erosion of the magnet layer causes rust, and further progress results in the loss of constituent particles. As a result, magnetic properties are significantly degraded. This phenomenon occurs irrespective of the presence or absence of processing, although there is a difference in the degradation speed. Generally, it is difficult to avoid the presence of moisture in the environment in which the permanent magnet material is used. Therefore, an appropriate surface treatment must be applied to the surface of the rare earth sintered permanent magnet having the R-Fe-B composition in order to impart corrosion resistance.

As the above-mentioned surface treatment method, a method of coating a Ni plating layer or a Ni-P alloy plating layer on the outermost surface of a rare earth sintered permanent magnet by an electric or electroless plating method, or a method of coating an aluminum vapor-deposited film. Thereafter, a method of forming a thin layer of a chromium composite oxide on the surface (aluminum chromate treatment), electrodeposition coating, or spray coating of epoxy or fluororesin has been put to practical use.

[0007]

However, each of these methods has some disadvantages. In the aluminumate treatment, expensive equipment such as waste liquid treatment equipment and a large amount of electric power and water are required from the viewpoint of environmental problems in the subsequent step of forming a thin film layer of chromium composite oxide, including a vapor deposition apparatus. It leads to cost increase. In addition, there is a disadvantage that it is difficult to coat the inside of the minute hole or the groove. Further, in the step of forming the thin film layer of the chromium composite oxide, there is a risk that human health may be impaired.

[0008] In the electrodeposition coating, the electric field distribution becomes non-uniform depending on the shape of the magnet, and a phenomenon occurs in which the coating film thickness varies depending on the location. In particular, an electric field concentrates at a portion having a sharp corner, and the coating film thickness becomes significantly larger than the set film thickness. This is a problem when dimensional accuracy of the entire magnet is required. In some cases, post-processing may be required. Furthermore, there are many pinholes in the obtained coating film, and there is a problem that as time passes, water reaches the surface of the magnet and causes corrosion. In addition, it is difficult to control the film thickness by spray coating of epoxy or fluororesin, and when the film thickness is small, the probability of occurrence of pinholes increases,
There are problems such as corrosion.

On the other hand, Ni or Ni alloy plating by an electric or electroless plating method has already been applied to various fields as a method for imparting excellent corrosion resistance at low cost, and this method has a substantially uniform film thickness regardless of the shape. Compared to the above surface treatment methods, such as that the entire surface can be coated with, the film thickness can be easily controlled and a film with few pinholes can be formed, and no large-scale and expensive equipment is required. It has many advantages and is highly evaluated as a method for imparting corrosion resistance to rare earth sintered permanent magnet materials having an R-Fe-B composition, and is widely used.

However, in the case of a Ni or Ni alloy plating layer formed by an electric or electroless plating method,
Sufficient corrosion resistance cannot be obtained. That is, Ni or N
If the i-alloy plating layer is formed directly on the surface of the rare earth sintered permanent magnet having the R-Fe-B composition, the adhesion is insufficient, so that the plating layer may be cracked or peeled off with time. This is particularly noticeable in a high-temperature and high-humidity environment. Further, when the Ni or Ni alloy plating layer is coated with a large thickness in order to obtain sufficient corrosion resistance, the magnet itself may be destroyed by internal stress of the film of the plating layer.

In order to solve the above problems, for example, Japanese Patent Laid-Open No.
As described in JP-A-42805 and JP-A-5-109519, a Cu layer or a Sn layer is formed as an underlayer, and a Ni or Ni alloy plating layer is coated thereon to improve the adhesion of the plating film. For example, these underlayers themselves have poor corrosion resistance. Therefore, when a Ni or Ni alloy plating layer is laminated on an underlayer which is a Cu layer or a Sn layer, the Ni or Ni alloy plating layer usually avoids generation of pinholes due to adhesion of dust (particles). However, since a small number of pinholes are present, water vapor and water gradually penetrate therefrom, and the underlying layer is corroded over time. As a result, pinholes, cracks, and the like are generated in the underlying layer made of the Cu layer or the Sn layer, and the moisture reaches the surface of the magnet material, eventually causing a phenomenon that the magnet material is corroded. Further, the Cu layer and the Sn layer are mainly formed by an electroplating method. In this case, however, generally, both have low current efficiency, so that the deposition rate is low, and there is a problem that productivity and economy are poor.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a rare earth sintered permanent magnet having an R-Fe-B composition, and to improve the adhesion and corrosion resistance of a plating film to improve the durability. Another object of the present invention is to provide a permanent magnet material having the following magnetic properties and excellent corrosion resistance.

[0013]

In order to achieve the above object, a permanent magnet material according to the present invention has the following constitution. That is, the permanent magnet material of the present invention has a R-
A permanent magnet material having a coating layer on the surface of a magnet material made of an Fe-B composition (R is a rare earth element), wherein the coating layer is a Zn plating layer or a Zn alloy plating layer, and a Ni plating layer or a Ni alloy plating. It is characterized by having a layer.

The permanent magnet material according to the present invention is characterized in that a Zn plating layer or a Zn alloy plating layer is provided on the surface of the permanent magnet material.

Further, the permanent magnet material of the present invention is characterized in that the Zn plating layer or the Zn alloy plating layer is provided below the Ni plating layer or the Ni alloy plating layer.

Preferably, the permanent magnet material of the present invention is characterized in that the Zn plating layer or the Zn alloy plating layer has a thickness of 0.1 μm or more.

Preferably, in the permanent magnet material of the present invention, the Ni plating layer or the Ni alloy plating layer has a thickness of 2 nm.
μm or more.

(Function) Regarding the permanent magnet material of the present invention, N
As a result of various studies by the present inventor on the plating film structure that sufficiently satisfies the adhesion and corrosion resistance of the i-plated layer or the Ni alloy plated layer and is excellent in productivity and economy,
It has been found that it is optimal to form a plating layer or a Zn alloy plating layer on the surface of a permanent magnet material and to laminate a Ni plating layer or a Ni alloy plating layer thereon.

The cause of this effect is that the Zn plating layer or the Zn alloy plating layer has excellent adhesion to the magnet material of the R—Fe—B composition, the Ni plating layer, or the Ni alloy plating layer. In addition, a Zn plating layer or a Zn alloy plating layer is generally a metal which is easily corroded. However, if it is formed on the surface of a magnet material having an R-Fe-B composition, it passes through a pinhole of the Ni plating layer or the Ni alloy plating layer. And the moisture is changed to the Zn plating layer or Zn
Even when reaching the alloy plating layer, the Zn plating layer or Zn
The alloy plating layer is different from the Cu layer and the Sn layer in that the R-Fe-
It acts anodicly with the B-based magnet material, corrodes only the Zn plating layer or Zn alloy plating layer, and has no effect on the underlying R-Fe-B-based magnet material. This is because the self-corrosion phenomenon has an action of stopping corrosion of the magnet material.

This effect can be obtained even if some pinholes or cracks exist in the Zn plating layer or the Zn alloy plating layer.
It has been confirmed by the present inventors that there is no problem. In addition, the Zn plating layer or the Zn alloy plating layer is usually formed by an electroplating method, but it is a known fact that the plating deposition rate is high and the current efficiency is excellent as compared with the Cu or Sn electroplating method. is there.

Therefore, a Zn plating layer or a Zn alloy plating layer and a Ni plating layer or Ni
By combining and laminating alloy plating layers, an R-Fe-B-based composition coated with a plating layer having good adhesion, having superior corrosion resistance, and having excellent productivity and economic efficiency due to a synergistic effect thereof. Of the permanent magnet material can be provided. Also, if a Ni plating layer or a Ni alloy plating layer is formed on the outermost layer, there is also an effect that the magnet can have a decorative appearance.

Here, the Zn alloy plating layer is an alloy plating layer with another metal such as Cu or Sn in addition to Zn, but the metal other than Zn is not limited to Cu or Sn. Also, the content of Zn in the Zn alloy plating layer is not particularly limited, but is preferably 10% or more in atomic%. In order to achieve the effect of the Zn plating layer or the Zn alloy plating layer, the plating film thickness is 0.1 μm.
The present inventors have confirmed that the above is preferable.

The Ni alloy plating layer is Ni-P, N
The plating layer has a composition such as iB, Ni-PW or Ni-BW, but is not particularly limited thereto. The plating thickness of the Ni plating layer or the Ni alloy plating layer is 2 μm in order to impart sufficient corrosion resistance.
It has been confirmed by the present inventors that m or more is preferable.

The Ni plating or Ni alloy plating layer can be formed by either an electroplating method or an electroless plating method. For coating, an electroless plating method is preferable.

The cleaning method and pretreatment method for forming the Zn plating layer or the Zn alloy plating layer and the Ni plating layer or the Ni alloy plating layer, the composition of the plating bath,
The temperature and plating conditions are not particularly limited, but the pH of various solutions and plating baths used for washing and pretreatment is preferably 6 or more. This is because, if the pH is less than 6, the corrosion of the sintered magnet material progresses electrochemically, the magnet layer is eroded, and the magnetic properties deteriorate. After plating, heat treatment may be performed to further increase the adhesion and hardness of each plating layer. The temperature at this time is 200
To 800 ° C is suitable, preferably 300 ° C to 400 ° C.
° C is optimal. The atmosphere at this time is not particularly limited, but a nitrogen or inert gas atmosphere is preferable.

The present invention also relates to a Zn plating layer or a Zn plating layer.
The present invention is not limited to a two-layer structure of an alloy plating layer and a Ni plating layer or a Ni alloy plating layer, but may include a Zn plating layer or a Zn alloy plating layer and another metal layer between the Ni plating layer and the Ni alloy plating layer. May be laminated, or a metal layer or a resin layer may be further coated on the Ni plating layer or the Ni alloy plating layer. Further, the present invention is not limited to the sintered magnet material, and the R-F
The present invention is also applicable to a bonded magnet in which a magnet powder having an EB composition is bonded with a resin.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to examples. Embodiment 1 Hereinafter, a permanent magnet material according to an embodiment of the present invention will be described. In this embodiment, a sintered magnet material composed of an R—Fe—B based composition (R is a rare earth element) is Nd—
A sintered magnet material having an Fe-B composition was employed. The method for producing a sintered magnet material having the Nd-Fe-B composition used in the present invention is as follows.
-B alloy is melted to produce an ingot. This ingot is pulverized to a mean particle size of 3 μm by a combination of a coarse pulverizer and a fine pulverizer to obtain a fine powder. This fine powder is pressed in a magnetic field to produce a compact having a uniform c-axis direction.
This molded body is sintered at a temperature of about 1100 ° C. in an argon atmosphere, and then heat-treated at about 600 ° C. in an argon atmosphere to have a length of 40 mm, a width of 30 mm and a thickness of 2 mm.
A block-shaped sintered magnet material having a high magnetic energy product ((BH) max) of 0 mm was obtained.

Thereafter, the block-shaped sintered body is cut using a wire saw, and then ground by a surface grinder, a lapping machine, or the like. Each side has a length of 10 mm and a width of 1 mm.
A rectangular parallelepiped having a size of 0 mm and a thickness of 5 mm was prepared and used as a test sample.

Thereafter, the test sample was subjected to ultrasonic cleaning in acetone, and then sodium hydroxide 20 g / L, sodium orthosilicate 70 g / L, sodium carbonate 20 g / L.
After degreased in an alkaline aqueous solution containing g / L, it was washed with pure water and dried with hot air. At this time, the organic solvent used is not limited to acetone, and may be another organic solvent, such as isopropyl alcohol or toluene. Similarly, the alkaline aqueous solution is not limited to the above components.

Thereafter, the test sample was placed on a plating jig having appropriate conductivity, and then immersed in a Zn plating solution having the following composition and conditions to form a plating layer.

Zn (CN) ₂ : 70 g / L NaCN: 40 g / L NaOH: 100 g / L pH: 12.2 Liquid temperature: 30 ° C. Current density: 2 A / dm ² Immersion time: 3 minutes

By the above operation, a Zn plating layer of 2 μm was coated on the entire surface of the test sample.

Thereafter, the substrate was washed with pure water, immersed in an electroless Ni-P plating solution having the following composition and conditions, and a 8 μm Ni-P alloy plating layer was coated on the Zn plating layer.

[0034] _{NaH 2 PO 2 · H 2 0} : 25g / L (NH 4) 2 SO 4: 10g / L C 3 H 4 (OH) (COONa) 3 · 2H 2 0: 40g /
_{L NiSO 4 · 6H 2 0:} 20g / L pH: 7.5 solution Temperature: 90 ° C. immersion time: 30 minutes

After plating is completed, the plate is washed with water, dried, and then
Heat treatment was performed at 0 ° C. in a nitrogen atmosphere for 1 hour. The obtained plating film was analyzed by EPMA (Electron Probe Micro-Analysis) to obtain a Zn plating layer having a uniform composition and a Ni plating layer.
It was confirmed that it had a two-layer structure composed of a -P alloy plating layer.

(Example 2) After preparing a test sample in the same manner as in Example 1, pre-plating treatment was performed. Thereafter, the test sample was placed on a plating jig having appropriate conductivity, and the following composition and It was immersed in a Zn-Cu plating solution under the conditions to form an alloy plating layer having a Zn-Cu composition.

CuCN: 20 g / L Zn (CN) ₂ : 20 g / L NaCN: 50 g / L NaCO ₃ : 30 g / L Aqueous ammonia: 2 cc / L pH: 10.5 Liquid temperature: 30 ° C. Current density: 0.5 A / Dm ² immersion time: 4 minutes

By the above operation, a Zn-Cu alloy plating layer of 2 μm was coated on the entire surface of the test sample.

Then, after washing with pure water, it was immersed in an electroless Ni-P plating solution having the same liquid composition and conditions as in Example 1, and the Ni-P alloy plating layer was formed on the Zn-Cu alloy plating layer. 8 μm was coated.

After plating is completed, the plate is washed with water, dried, and then dried for 30 minutes.
Heat treatment was performed at 0 ° C. in a nitrogen atmosphere for 1 hour. Analysis by EPMA (Electron Probe Micro-Analysis) confirmed that the obtained plating film had a two-layer structure composed of a Zn-Cu alloy plating layer and a Ni-P alloy plating layer having a uniform composition. At this time, the Zn content in the Zn—Cu alloy plating layer was about 50 atomic%.

(Example 3) After preparing a test sample in the same manner as in Example 1, pre-plating treatment was performed. Thereafter, the test sample was placed on a plating jig having appropriate conductivity, and the following composition and It was immersed in a Zn-Sn plating solution having the above conditions to form an alloy plating layer having a Zn-Sn composition.

Na ₂ SnO ₃ .3H ₂ O: 20 g / L Zn (CN) ₂ : 20 g / L NaCN: 50 g / L NaOH: 30 g / L pH: 10.5 Liquid temperature: 50 ° C. Current density: 1.5 A / Dm ² immersion time: 5 minutes

Through the above operation, a Zn-Sn alloy plating layer of 2 μm was coated on the entire surface of the test sample.

Then, after rinsing with pure water, it was immersed in an electroless Ni-P plating solution having the same liquid composition and conditions as in Example 1 to form a Ni-P alloy plating layer on the Zn-Cu alloy plating layer. 8 μm was coated.

After plating is completed, the plate is washed with water, dried, and then
Heat treatment was performed at 0 ° C. in a nitrogen atmosphere for 1 hour. Analysis of the obtained plating film by EPMA (Electron Probe Micro-Analysis) confirmed that it had a two-layer structure composed of a Zn-Sn alloy plating layer and a Ni-P alloy plating layer having a uniform composition. At this time, the Zn content in the Zn—Sn alloy plating layer was about 40 atomic%.

(Example 4) After preparing a test sample in the same manner as in Example 1, pre-plating treatment was performed. Thereafter, the test sample was placed on a plating jig having an appropriate conductivity. It was immersed in a Zn plating solution having the same composition and conditions to form a Zn plating layer.

By the above operation, a Zn plating layer of 2 μm was coated on the entire surface of the test sample.

Thereafter, the substrate was washed with pure water, immersed in an electroless Ni-B plating solution having the following composition and conditions, and coated with a Ni-B alloy plating layer of 8 μm on the Zn plating layer.

[0049] _{(CH 3) 2 NHBH 3:} 10g / L C 3 H 4 (OH) (COONa) 3 · 2H 2 0: 30g /
L CH ₂ (COOH) ₂ : 10 g / L NiSO ₄ .6H ₂ 0: 10 g / L NiCl ₂ .6H ₂ 0: 20 g / L Other additives: 2 g / L pH: 7.0 Liquid temperature: 70 ° C.

After the plating is completed, the plate is washed with water, dried, and then
Heat treatment was performed at 0 ° C. in a nitrogen atmosphere for 1 hour. The obtained plating film was analyzed by EPMA (Electron Probe Micro-Analysis) to obtain a Zn plating layer having a uniform composition and a Ni plating layer.
It was confirmed that it had a two-layer structure composed of a -B alloy plating layer.

(Comparative Example) As Comparative Example 1 with respect to the present embodiment, a block-shaped sintered body was cut and ground to obtain a test sample in the same manner as in Example 1, and no permanent surface treatment was performed. After preparing a magnet sample and a test sample as Comparative Example 2 in the same manner as in Example 1, pre-plating treatment was performed.
Then, after placing the test sample on a plating jig having appropriate conductivity, it is immersed in a copper cyanide plating solution having the following composition and conditions, and after forming a Cu plating layer of 2 μm, it is washed with pure water. Then, it was immersed in an electroless Ni-P plating solution having the same liquid composition and conditions as in Example 1 to cover the Cu plating layer with a Ni-P alloy plating layer of 8 μm.

CuCN: 20 g / L NaCN: 30 g / L Na ₂ CO ₃ : 50 g / L NaOH: 30 g / L pH: 11.5 Liquid temperature: 40 ° C. Current density: 0.5 A / dm ² Immersion time: 5 minutes

After plating is completed, the plate is washed with water, dried, and then dried for 30 minutes.
Heat treatment was performed at 0 ° C. in a nitrogen atmosphere for 1 hour. The obtained plating film was analyzed by EPMA (Electron Probe Micro Analysis) to obtain a Cu plating layer of uniform composition and Ni
It was confirmed that it had a two-layer structure composed of a -P alloy plating layer. Further, as Comparative Example 3, after preparing a test sample in the same manner as in Example 1, pre-plating treatment was performed, and thereafter, the test sample was placed on a plating jig having appropriate conductivity, and the following composition and conditions were used. Immersed in an alkaline Sn plating solution consisting of
After forming μm, it was washed with pure water and immersed in an electroless Ni-P plating solution having the same solution composition and conditions as in Example 1,
A Ni-P alloy plating layer was coated on the Sn plating layer to a thickness of 8 µm.

Na ₂ SnO ₃ .3H ₂ O: 50 g / L NaOH: 10 g / L pH: 10.5 Liquid temperature: 60 ° C. Current density: 1.5 A / dm ² Immersion time: 5 minutes

After plating is completed, the plate is washed with water, dried, and then
Heat treatment was performed at 0 ° C. in a nitrogen atmosphere for 1 hour. The resulting plating film was analyzed by EPMA (Electron Probe Micro Analysis) to obtain a Sn plating layer having a uniform composition and Ni plating.
It was confirmed that it had a two-layer structure composed of a -P alloy plating layer.

As an evaluation method, the magnetic properties of each test sample of Examples 1 to 4 and Comparative Examples 1 to 3 were evaluated by a vibrating sample magnetometer (VSM). A corrosion resistance test was performed by exposing to an atmosphere of 95% relative humidity for 4 days, and after the test, the magnetic properties were evaluated and the magnet surface was again observed with a metallographic microscope. The results are shown in the table below.

[0057]

[Table 1]

From Table 1, it can be seen that all of the permanent magnet materials obtained in Examples 1 to 4 were compared with the permanent magnet materials obtained in Comparative Examples 1 to 3, so that the magnetic properties after the corrosion test were clear. No deterioration of the surface occurs, no discoloration or rust is observed,
It was confirmed that it was possible to maintain excellent magnetic properties and corrosion resistance.

[0059]

As described above, in the permanent magnet material according to the present invention, after the Zn plating layer or the Zn alloy plating layer is formed on the surface of the magnet material having the R-Fe-B composition, the Ni plating layer or the Ni plating layer is formed. By coating the alloy plating layer, the adhesion of the plating film is improved, and it is possible to provide a permanent magnet material having excellent corrosion resistance and high magnetic properties, as well as improved economy and productivity. That is, it is possible to provide a highly reliable permanent magnet material having excellent magnetic properties applicable to various electronic products.

Continuing from the front page (72) Inventor Shinji Ikeda 2-25 Kita Industrial Park, Kitakami City, Iwate Prefecture Inside Seiki Minami Co., Ltd. (72) Inventor Takeshi Takahashi 2-25 Kita Industrial Park Kitagami City, Iwate Prefecture Seiki Uegami Share Company F term (reference) 4K022 AA02 AA44 BA04 BA14 BA16 BA24 BA32 CA28 DA01 DB02 EA01 4K024 AA03 AA05 AA14 AA17 AB02 BA01 BB14 CA03 CA04 CA06 DB01 GA04 5E040 AA04 BC01 BC08 BD01 CA01 NN05

Claims (6)

[Claims] 1. An R—Fe—B composition (R is a rare earth element)
A permanent magnet material having a coating layer on the surface of a magnet material comprising: a zinc plating layer or a Zn alloy plating layer; and a Ni plating layer or a Ni alloy plating layer. material. 2. The method according to claim 1, wherein a Zn plating layer or a Zn alloy plating layer is provided on a surface of the magnet material.
2. The permanent magnet material according to 1. 3. The permanent magnet material according to claim 1, wherein the Zn plating layer or the Zn alloy plating layer is provided below the Ni plating layer or the Ni alloy plating layer. 4. The permanent magnet material according to claim 1, wherein the Ni plating layer or the Ni alloy plating layer is on the outermost layer of the permanent magnet material. 5. The permanent magnet material according to claim 1, wherein a thickness of the Zn plating layer or the Zn alloy plating layer is 0.1 μm or more. 6. The permanent magnet material according to claim 1, wherein a thickness of the Ni plating layer or the Ni alloy plating layer is 2 μm or more.