JPH0613218A - Surface processing method of fe-b-r base sintered magnet - Google Patents

Abstract

PURPOSE:To provide a film having excellent corrosion resistance with minimum pin holes by a method wherein the film is Ni-plated using a plating solution in specific composition thereby minimizing the elution amount from the magnet surface while enhancing the bond properties onto the magnet. CONSTITUTION:A plating solution in pH6-8 comprizing nickel sulfate 70g/1-200g/l, one or two kinds of ammonium citrate or sodium citrate 25-50g/l, boric acid 10g/l-30g/l, one or two kinds of ammonium chloride or sodium chloride 6g/l-10g/l, stress inhibitor 3g/l-5g/l is prepared. Next, the surface of the Fe-B-R base sintered magnet before Ni-plating step is cleaned up to be Ni-plated using the plating solution. Through these procedures, the elution amount of the sintered magnet during the plating step can be minimized while reinforcing the film brittleness peculier to neutral, alkalic plating solution thereby enabling the Ni-plated film having excellent bond properties as the sintered magnet and the corrosion resistance with minimum pin holes to be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a surface treatment method for forming a Ni plating layer on the surface of a Fe-BR system sintered magnet. The present invention relates to a surface treatment method for a Fe—B—R based sintered magnet in which the elution of Fe is reduced as much as possible, the adhesion to the material is made strong, and the occurrence of pinholes in the plating film is suppressed to improve the corrosion resistance.

[0002]

2. Description of the Related Art Fe- developed as a high-performance permanent magnet
Since the B-R sintered magnet contains a large amount of Fe, which is easily oxidized, it is necessary to form an oxidation resistant coating on the surface of the magnet. As shown in Japanese Patent Publication No. 3-74012, the Ni-Ni sintered magnet is used. An Fe-BR sintered magnet coated with an oxidation resistant plating layer such as plating has been proposed.

Further, as disclosed in JP-A-63-110708, after the surface of the Fe-BR type sintered magnet is plated with Ni, it is further subjected to cationic electrodeposition coating (JP-A-61-110).
It has been proposed to improve the corrosion resistance by carrying out (see JP-A-130453).

[0004]

When a Ni plating layer is formed as the first layer on the surface of an Fe-BR system sintered magnet by a wet surface treatment method, the step of suppressing the elution of the magnet surface by the plating solution is a process. It is important for management. Therefore, the pH of the plating solution is preferably 6 or more neutral or alkaline.

However, commonly used Ni plating baths include a Watt bath and a Ni sulfamate bath, both of which are plating solutions used in an acidity of PH 6 or less. When Ni plating is directly applied to the surface of the B-R magnet, elution of the magnet surface occurs, Fe, B, and R are accumulated in the plating solution, and it is difficult to remove them.

On the other hand, in terms of the quality of the Ni plating film, pinholes are likely to occur due to the elution of the magnet surface,
There was a problem in corrosion resistance. Therefore, a Ni plating solution having a pH of 6 or more is desirable in order to solve the above problem. However, if the pH is 6 or more, the plating film is hard and brittle, so that the adhesion to the surface of the sintered magnet is poor, and the hydroxide caused by elution of the magnet surface However, there is a problem in that the precipitation of is likely to occur.

According to the present invention, when Ni plating is provided on the surface of a Fe-BR sintered magnet, the elution of the magnet surface during plating is minimized, the adhesion to the magnet is made strong, and the plating film It is an object of the present invention to provide a surface treatment method for a Fe-BR sintered magnet capable of suppressing pinhole generation and improving corrosion resistance.

[0008]

[Means for Solving the Problems] The inventors have made various studies on the composition of a Ni plating solution having a high coating adhesion strength and a treatment method thereof, in which elution on the surface of a Fe—BR system sintered magnet during plating is minimized. As a result, PH6 to which nickel sulfate was added as a nickel salt, citrate as a complexing agent, boric acid as a PH buffer, chloride for increasing the electrical conductivity of the liquid, and a stress suppressor for improving the brittleness of the coating was added. By electroplating with the plating solution of No. 8, the elution amount of the sintered magnet during plating can be suppressed as much as possible, and the brittleness of the coating peculiar to the neutral or alkaline plating solution can be improved. N with excellent adhesion and corrosion resistance with few pinholes
The inventors have found that an i-plated film can be obtained and completed the present invention.

That is, according to the present invention, after the surface cleaning treatment of the Fe-BR type sintered magnet, 70 g of nickel sulfate /
1 to 200 g / l, one or two ammonium citrate or sodium citrate 25 to 50 g / l, 10 g / l to 30 g / l boric acid, one or two ammonium chloride or sodium chloride 6 g / l to A surface treatment method for a Fe-BR sintered magnet, characterized in that the surface of the magnet is Ni-plated with a plating solution having a pH of 6 to 8 consisting of 10 g / l and a stress suppressor of 3 g / l to 15 g / l. Is.

In the present invention, Fe-
The surface treatment of the B-R sintered magnet is not particularly limited, but at least known cleaning treatment may be performed, such as sulfuric acid,
It is recommended to perform pickling treatment or activation treatment with nitric acid or the like.

Composition of Plating Solution Nickel sulfate is a main component of the Ni plating solution of the present invention, but it is not preferable since the uniform electrodeposition property is deteriorated even if it is less than 70 g / l or more than 200 g / l. The citrate may be sodium citrate, but in the case of ammonium citrate, if it is less than 25 g / l, the complexing force of Fe, which is slightly dissolved from the magnet surface, is insufficient, and if it exceeds 50 g / l, the magnet surface is dissolved. Not preferred to promote. Boric acid is 10
When it is less than g / l, the buffering effect is poor, and boric acid exceeding 30 g / l is unnecessary. The chloride may be sodium chloride, but in the case of ammonium chloride, if it is less than 6 g / l, the electric conductivity is poor, and if it exceeds 10 g / l, the dissolution of the magnet surface is promoted, which is not preferable. As a stress suppressor, saccharin, 1.5 naphthalene sodium disulfonate, 1
-There are 3/6 sodium naphthalene trisulfonate, p-toluene sulfonamide, etc. If the amount is less than 3 g / l, the effect is small, and the addition in excess of 15 g / l is unnecessary.

When the pH of the plating solution is less than 6, the elution of the magnet surface is likely to occur, and when the pH exceeds 8, the plating film becomes hard and brittle, so the pH is 6 or less.
~ 8. The pH is adjusted with ammonia or sodium hydroxide, and the liquid temperature is preferably 40 to 60 ° C. When the liquid temperature is lower than 40 ° C., the electric conductivity is lowered, a high current density cannot be applied, and the plating rate is lowered. On the other hand, 60 ° C
If it exceeds, it is not preferable because a heat-resistant material is required for the plating tank and the jig. Further, the anode may be electrolytic nickel, but since it has poor solubility and relatively large amount of anode sludge is generated, sulfur-containing nickel (S 0.01 to 0.0
5%) is desirable.

The plating thickness is preferably 10 to 20 μm when only the Ni plating film of the present invention is used, and at least 0.2 μm or more is necessary when the Ni plating of the present invention is used as the first layer plating. When using a strongly acidic plating solution for layer plating, the thickness is preferably 5 μm or more. Also, for the plating of the second layer or more, semi-bright Ni, bright N
It is possible to laminate any one of a plating film of i, Sn, Cr, Zn, Au, Ag, and Cu or to laminate a plurality of plating films. Further, any known oxidation resistant and corrosion resistant coating can be formed on the Ni plating according to the present invention.

[0014]

The present invention provides nickel sulfate as nickel salt,
Citrate as a complexing agent, boric acid as a PH buffer,
Characterized by a plating solution of PH6 to 8 in which a chloride for increasing the conductivity of the solution and a stress suppressor for improving the brittleness of the coating are added and compounded, and the elution amount of the sintered magnet during the electroplating process is suppressed as much as possible. It is possible to improve the brittleness of the coating peculiar to the neutral and alkaline plating solutions, to obtain a Ni plating coating having excellent adhesion to a sintered magnet and high corrosion resistance with few pinholes. By applying the Ni plating of the present invention to the surface of the sintered magnet as the first layer plating film, the plating of the second layer or more can be any of strong acid and strong alkali,
The applicable range of plating species is widened, and a coating film formed by any known film forming method can be laminated.

[0015]

[Example] Electrolytic iron, ferroboron, R as starting materials
As Nd as a required magnet composition, after melt casting, coarse pulverization and fine pulverization by a mechanical pulverization method to obtain a particle size of 3 to 10 μm.
Of fine powder was obtained. The obtained fine powder was compacted in a magnetic field of 10 kOe, sintered in an Ar atmosphere at 1100 ° C. for 1 hour, and then aged at 600 ° C. for 2 hours. The composition of the obtained magnet was 15 Nd. It was -7B-78Fe. After a test piece was cut out from the obtained magnet, concentrated sulfuric acid was diluted 10 times with water, and a pickling treatment was performed for 10 minutes, and then a plating treatment was performed under various Ni plating conditions shown in Table 1. Adhesion test and corrosion resistance evaluation were performed. The test results are shown in Table 2. The adhesion test is measured by a tensile tester and conforms to JIS H8630, C6481. The salt spray test is 5% NaCl, 35 ° C. × 24 Hr, and the pressure cooker test is 125 ° C. × 2 atm ×
The condition is 85% humidity × 120 Hr.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

The present invention uses a Ni plating solution having a specific composition to suppress the elution amount of a sintered magnet during plating as much as possible, and improves the brittleness of a coating peculiar to a neutral or alkaline plating solution. A Ni-plated coating having excellent adhesion to the sintered magnet and high corrosion resistance with few pinholes can be provided on the surface of the Fe-BR sintered magnet. By applying the Ni plating of the present invention to the surface of the sintered magnet as the first-layer plating film, the plating of the second layer or more enables any plating of strong acid and strong alkali, and the applicable range of plating species is widened.
A coating film formed by any known film forming method can be laminated.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication C25D 5/26 A 7/00 K (72) Inventor Tsunekazu Saigo 2 Minami Suita, Suita City, Osaka Prefecture 19-1 Sumitomo Special Metals Co., Ltd. Suita Works (72) Inventor Michio Yamashita 2-15-17 Egawa, Shimamoto Town, Mishima-gun, Osaka Prefecture Sumitomo Special Metals Co., Ltd. Yamazaki Works

Claims (1)

[Claims] 1. An Fe-BR sintered magnet is surface-cleaned, and then nickel sulfate 70 g / l to 200 g / l, ammonium citrate or sodium citrate one or two kinds 25 to 50 g / l. , Boric acid 10g / l-30g
/ L, one or two of ammonium chloride or sodium chloride 6 g / l to 10 g / l, stress suppressor 3 g / l to
A surface treatment method for a Fe-BR sintered magnet, characterized in that the magnet surface is plated with Ni with a plating solution of PH 6 to 8 containing 15 g / l.