JPH083783A - Method for treating surface of magnetic alloy - Google Patents

Abstract

PURPOSE:To remarkably improve the adhesion of a plated film by treating the surface of an R-TM-B magnetic allay with an alkaline surface treating agent and a desmutting agent. CONSTITUTION:The surface of a magnetic alloy constituted of, by weight, 5 to 40% R (the combination of one or >=two kinds among rare earth elements including Y), 50 to 90% TM (denoting transition metals essentially consisting of Fe, and in which a part thereof may be substituted by the other metals or nonmetals) and 0.2 to 8% B (boron) is subjected to surface regulation by an alkaline soln. of pH>8 constituted of organic complex compounds, inorganic complex compounds and a buffer. After that, it is subjected to desmutting by an alkaline soln. of pH>9 constituted of organic carboxylate (including hydrooxycarboxylic acid), inorganic complex compounds and peroxide, and after that, an oxidation resistant plated film is formed.

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 treatment method for forming a plating layer on the surface of a magnetic alloy, and in particular, in the pretreatment for forming the plating layer, an alkaline surface conditioner and a desmutting agent are used. The present invention relates to a product in which the adhesion of a plating film is remarkably improved by performing surface conditioning and desmutting.

[0002]

2. Description of the Related Art As electric and electronic equipments have become higher in performance and smaller in size, permanent magnets used in these equipments are also required to have similar requirements. R-TM-B based magnetic alloy developed as a high-performance permanent magnet capable of meeting these requirements (here, R
Is one or a combination of two or more rare earth elements including Y, and TM is a metal having a transition metal such as Fe or Co as a center and a part thereof replaced with another metal or a nonmetal. B is boron. Since (a) contains a large amount of Fe, which is easily oxidized, means for providing an oxidation resistant coating layer on the surface of the magnetic alloy has been taken. As the type of the coating layer, metal plating, resin, metal vapor deposition and the like have been proposed, and in particular, plating attracts attention as improving the corrosion resistance of the R-TM-B based magnetic alloy by a simple treatment (for example, JP-A-60
-54406).

[0003]

Generally, in the plating process of R-TM-B type magnetic alloy, the work strain layer and oxide film layer on the alloy surface are removed and cleaned by acid etching before plating. , Then add plating. However, due to the accompanying hydrogen absorption phenomenon in the magnet material during acid etching, or the acid remaining on the sintered magnet surface that could not be completely removed by washing after acid etching, the elution of magnet components on the magnet surface immediately before plating. By happening
There is a problem that the adhesion between the surface of the sintered magnet and the plating is hindered, and as a result, the function of the plating layer as an oxidation resistant protective film cannot be fully exerted. Further, there are many irregularities on the surface of the sintered magnet, it is difficult to remove the smut generated during etching, and plating is performed with the smut attached to the surface of the magnet, resulting in poor adhesion of the plating. An object of the present invention is to provide a highly reliable surface treatment method for an R-TMB based magnetic alloy with improved adhesion between a magnet and a plating layer.

[0004]

In order to solve the above-mentioned problems existing in the prior art, the present invention provides a weight ratio of R (where R is one or more of rare earth elements including Y). 5 to 40%, TM (here, TM is a transition metal mainly composed of Fe and may be partially replaced with other metal or nonmetal) 50 to 90%, B (boron) 0.
The surface of the magnetic alloy composed of 2 to 8% is an organic complex compound,
Alternatively, the surface is adjusted with an alkaline solution having a pH of 8 or more, which comprises an inorganic complex compound and a buffer, and then desmutted with an alkaline solution having a pH of 8 or more, which comprises an organic carboxylate (including oxycarboxylate), an inorganic complex compound and a peroxide. Then, the technical means of forming an oxidation resistant plating film after that was adopted. The adhesion can be further improved by setting the pH of the plating solution forming the oxidation resistant plating film to 7 or more.

[0005]

In the present invention, the magnetic alloy is first subjected to surface conditioning treatment. As the surface modifier used for this treatment, ethylenediaminetetraacetate, trinitroacetic acid, an organic chelating agent typified by glycine and the like, or an inorganic complex compound typified by sodium pyrophosphate, potassium pyrophosphate, and triethanol. It is composed of an alkaline solution having a pH of 8 or more containing a buffer agent such as amine and hexamine. When a magnetic alloy was dipped using this solution, the work-affected layer or oxide layer forming the inactive surface of the alloy surface was selectively attacked by the action of various complex ions in the solution, resulting in the result. The alteration product is aggregated on the surface as a smut layer. Next, a desmutting treatment is applied to remove this smut layer. The desmutting agent used in this case is an organic carboxylic acid salt (including oxycarboxylic acid salt) typified by sodium tartrate, sodium citrate, etc., and an inorganic complex compound typified by sodium pyrophosphate, potassium pyrophosphate. , And an alkaline solution having a pH of 8 or more, which contains peroxides such as hydrogen peroxide and sodium peroxide. When the magnetic alloy after surface conditioning is immersed in this solution, the smut layer is selectively dissolved and removed from the magnet surface by the combined action of carboxylate and peroxide in the solution, and the ideal activity Since the surface is obtained, the adhesion in the plating process in the next step can be improved.

Further, in order to suppress the elution of the magnetic alloy by the plating solution itself, if a plating solution having a pH of 7 or more, for example, electroless copper, alkaline electroless nickel or the like is used, the adhesion is further improved. Since electroless copper and alkaline electroless nickel have a relatively low deposition rate, the lower layer is electroless copper or electroless nickel, and the upper layer is electroplated with one or more layers having a fast deposition rate, such as electroplating. When nickel plating or electrolytic copper plating is used, a practical and highly reliable plated film can be obtained. In the present invention, elements such as Fe, Co, and Ni that partially substitute for TM, and Ga, Al, Ti, Cr, and
Mn, Zr, Hf, Nb, Ta, Mo, Ge, Sb, B
i and others can be added, and the present invention can be applied to any R-TM-B based magnetic alloy. N as an oxidation resistant plating film
A metal film of i, Cu, Co or the like may be plated by either electroplating or electroless plating. The plating film preferably has a thickness of 5 to 25 μm.

[0007]

EXAMPLES The effects of the present invention will be specifically described with reference to examples. An alloy having a composition of Nd (Fe _0.7 Co _0.2 B _0.07 Ga _0.03 ) _{6.5 was} produced in an arc melting furnace, and the obtained ingot was roughly crushed by a stamp mill and a disc mill. Then, fine pulverization was carried out by a jet mill using N ₂ gas as a pulverizing medium to obtain fine pulverized powder having a pulverized particle size of 3.5 μm. The raw material powder obtained was subjected to transverse magnetic field molding in a magnetic field of 15 KOe at a molding pressure of ² ton / cm ² . Molded product in vacuum at 1090 ° C for 2
Sintering was carried out for an hour, and then cut into a size of 8 × 10 × 6 mm, followed by heat treatment in argon at 900 ° C. for 2 hours and 600 ° C. for 1 hour. The obtained sample was degreased with ethyl alcohol for 5 minutes and pretreated under the conditions shown in Table 1.

[0008]

[Table 1] Then, barrel plating was performed in the plating bath shown in Table 2.

[0009]

[Table 2] After plating, the adhesion test is measured by a tensile tester (Sebastian 1), the constant temperature and humidity test is performed at 85 ° C and 85% humidity for 500 hours, and the pressure cooker test is 120 ° C.
It was carried out at × 2 atm × 100% humidity for 100 hours. Table 3 shows the test results. In the comparative example, as a pretreatment, the plate was washed with 5% nitric acid for 1 minute, washed with water, and then plated as in the example.

[0010]

[Table 3] As is clear from Table 3, the pretreatment with the alkaline solution significantly improves the adhesion strength between the magnetic alloy and the plating film, and also dramatically improves the corrosion resistance.

[0011]

Since the present invention has the above-described structure and operation, it is possible to dramatically improve the RT without causing a cost increase by the relatively easy pretreatment with an alkaline solution.
It is intended to provide an R-TM-B based magnetic alloy having improved adhesion between the M-B based magnetic alloy and plating and having excellent corrosion resistance and high reliability.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Ushijima 5200 Sankejiri, Kumagaya City, Saitama Hitachi Kumagai Plant (72) Inventor Yu Ushimaru 929 Nakakozaka, Sakado, Saitama Japan New Chrome Co. (72) Inventor Asao Hatta 929 Nakazasaka, Sakado, Saitama Prefecture, Japan Nippon Chrome Co., Ltd.

Claims (3)

[Claims] 1. A weight ratio of R (where R is one or a combination of two or more rare earth elements including Y) 5 to 40%,
TM (here, TM is a transition metal mainly composed of Fe and may be partially replaced with another metal or non-metal element)
The surface of a magnetic alloy composed of 50 to 90% and B (boron) of 0.2 to 8% is subjected to surface conditioning with an alkaline solution having a pH of 8 or more composed of an organic complex compound and / or an inorganic complex compound and a buffer, and then an organic carboxylic acid. PH8 consisting of salts (including oxycarboxylic acid salts), inorganic complex compounds and peroxides
A method for surface treatment of a magnetic alloy, comprising desmutting with the above alkaline solution, and then forming an oxidation resistant plating film. 2. The oxidation resistant film according to claim 1,
A surface treatment method for a magnetic alloy, which is formed using a plating solution of 7 or more. 3. The electroless copper or electroless nickel formed by using a plating solution having a pH of 7 or more as the lower layer of the oxidation resistant plating film according to claim 1, and the upper layer having one or two or more layers of electricity. Surface treatment method of magnetic alloy used as plating layer.