JPH0931606A - Corrosion resistant magnetic alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the corrosion resistance of a magnetic R-TM-B alloy by softening a coating film by the formation of an acicular structure and forming a microporous surface. SOLUTION: This corrosion resistant magnetic alloy has an Ni plating layer having an acicular structure of >=2μm length on the surface of a magnetic R-TM-B alloy consisting of 5-40wt.% R (R is one or more kinds of rare earth elements including Y), 50-90wt.% TM (TM is one or more kinds of transition metals selected from among Fe, Co, Ni, Ga, Al, Ti, V, Cr, Mn, Zr, Hf, Nb, Ta, Mo, Ge, Sn, Sb and Bi) and 0.2-8wt.% B (boron). The adhesion of the magnetic body to the Ni plating layer is improved.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a corrosion resistant magnetic alloy,
The present invention relates to a magnet body having a significantly improved corrosion resistance by coating the surface of the magnet body with a Ni plating layer having a needle-like structure having a length of 2 μm or more.

[0002]

2. Description of the Related Art With the high performance and miniaturization of electric and electronic devices, the same demands have been placed on the magnetic alloy, which is one of the components. That is, the strongest magnetic alloy before was the rare earth / cobalt (R-Co) system, but in recent years, the more powerful RT
The emergence of MB magnetic alloys (JP-A-59-460)
08 publication). Here, R is one kind or a combination of two or more kinds of rare earth elements including Y, TM is a transition metal centered on Fe and Co, and a part thereof is replaced with another metal element or non-metal element. Also includes things. B is boron. However, the R-TM-B type magnetic alloy has a problem that it is extremely rusty. Therefore, in order to improve the corrosion resistance, a measure has been taken to provide an oxidation resistant protective layer on the surface of the permanent magnet body. As the type of protective layer, electrolytic Ni plating, oxidation resistant resin, Al ion plating, etc. have been proposed. In particular, electrolytic Ni plating is a simple treatment for R-TM-
Attention has been paid to improve the corrosion resistance of B-based magnetic alloys (Japanese Patent Laid-Open No. 60-54406). Electrolytic Ni plating has the advantage that the surface protection layer has better mechanical strength than the oxidation resistant resin, and that the protection layer itself has almost no hygroscopicity. Furthermore, as the type of Ni plating, a Ni plating layer having a fine layered structure as shown in FIG. 2 has been generally recommended.

[0003]

However, the Ni plating layer having a fine layered structure has a drawback that the residual internal stress is large. Therefore, the adhesion between the Ni plating layer and the medium to be plated, which was not a problem in the medium to be plated such as a steel material having high physical strength or a copper alloy, has a low physical strength of R-TM because of the sintered metal. There is a problem that it is low with respect to the -B type magnetic alloy. Also, since the residual internal stress is large, double plating is likely to occur even in the coating. Furthermore, since the Ni plating layer composed of a fine layered structure has a smooth surface, if a pinhole is locally generated, a corrosion current concentrates on that part, and local corrosion proceeds to cause corrosion deterioration. It has drawbacks. SUMMARY OF THE INVENTION The present invention provides a magnetic alloy having a highly reliable corrosion resistant coating, which greatly improves the conventional problems.

[0004]

The present invention is based on the weight ratio of R
(Where R is a combination of one or more rare earth elements including Y) 5 to 40%, TM (where TM is Fe, C
o, Ni, Ga, Al, Ti, V, Cr, Mn, Zr,
Transition metal of one kind or a combination of two or more kinds selected from Hf, Nb, Ta, Mo, Ge, Sn, Sb and Bi) 50
~ 90%, B (boron) 0.2 ~ 8% R-TM-
A corrosion-resistant magnetic alloy having a Ni-plated layer having a needle-like structure having a length of 2 μm or more on the surface of a B-based magnetic alloy.

The present invention softens the coating by changing the Ni plating layer from a conventional fine layered structure to a needle-shaped structure to reduce residual stress and to form a microporous surface to form an R-TM-B system. It improves the corrosion resistance of the magnetic alloy.

When the Ni plating layer is constituted by the needle-like structure as shown in FIG. 1, the film hardness is formed as a softened film as compared with that of the fine layered structure. This tendency becomes more remarkable as the size of the needle-like structure increases, and the softening of the coating reduces the residual internal stress and improves the adhesion. Further, unlike the smooth surface of the Ni-plated layer having a fine layered structure, the surface of the Ni-plated layer having a needle-shaped structure is formed as a microporous surface. Therefore, since the corrosion current is evenly distributed over the entire surface due to the innumerable minute holes on the surface, the local corrosion is prevented from progressing in the pinhole and the corrosion from the Ni plating layer to the substrate is prevented. Very slow speed and improved moisture resistance. In the present invention, in order to realize the softening of the coating and the formation of the microporous surface, it is desirable to set the length of the needle-shaped structure to be 2 μm or more. As the means for forming the above-mentioned Ni plating layer, there are factors such as the surface roughness of the magnetic body before plating, the Ni plating solution composition, the concentration, the type and the amount of the additive, and the specific range of these factors. It is possible to obtain needle-like tissue within. Conceptually, it is preferable to increase the surface roughness of the magnet body before plating. In particular, it is desirable to make unevenness of 5 μm or more. As a method, it is possible to set irregularities by adjusting the treatment time of the pre-plating etching step to be longer. Further, it is desirable to reduce the concentration of the components in the plating solution. By combining these means, it becomes possible to set the Ni needle-like structure on the surface of the magnet body. Furthermore, for the purpose of improving the corrosion resistance, Cu, Ni, Al, Zn, Sn, Cr, N is formed on the surface of the Ni plating layer.
A metal coating such as i-P or an organic coating such as a furan-based resin, an acrylic-based resin, an epoxy-based resin, a melanin-based resin, and a parylene-based resin may be sequentially laminated and coated with one or more coatings. .

In the present invention, T of Fe, Co, Ni or the like is used.
The element substituting a part of M is G depending on the purpose of addition.
a, Al, Ti, V, Cr, Mn, Zr, Hf, Nb,
Ta, Mo, Ge, Sb, Sn, Bi can be added, and the present invention can be applied to any R-TM-B type magnet. Further, the manufacturing method thereof may be either a sintering method, a molten metal quenching method, or a modification thereof. As a manufacturing method, plating is performed after degreasing with an organic solvent. The thickness of the plating layer is preferably 2 to 40 μm. The pre-plating treatment is intended to remove the work-affected layer on the surface of the magnet and to activate the pre-plating, and etching using an acidic solution is preferable. The type of Ni plating may be a Watt bath, a sulfamic acid bath, or an ammonium bath. The types of organic additives are:
Saccharin, 1-4 butynediol and coumarin are preferable.

[0008]

EXAMPLES Examples are shown below. Note that the present invention is not limited to the following embodiments. 30wt% Nd, 2w
An alloy having a composition of t% Dy, 3wt% Co, 1wt% B, and balFe was prepared by arc melting, and the obtained ingot was roughly crushed by a stamp mill and a disc mill. Then N ₂
Fine pulverization was performed with a jet mill using gas as a pulverizing medium to obtain fine pulverized powder having a pulverized particle size of 4.0 μm. The obtained raw material powder was molded in a magnetic field of 15 kOe at a molding pressure of ² ton / cm ² . The obtained molded body was sintered in vacuum at 1100 ° C. for 2 hours, cut into a size of 18 × 10 × 6 mm, and then held in an atmosphere of argon at 550 ° C. for 1 hour. The R-TM-B based magnetic alloy thus obtained was etched with an acid of 25 vol% acetic acid. On this occasion,
The etching time was adjusted so that the surface roughness of the magnet had the values shown in Table 1. Then, a 10 μm Ni plating layer was coated under the conditions shown in Table 1, and this was used as a test piece. Table 2 shows common conditions for the Ni plating treatment. For each of these test pieces, observation of the needle crystal size of the coating cross section by a scanning electron microscope, 80 ° C., 90% R
Moisture resistance test for 1000 hours at H, 120 ° C, 100% R
A 100-hour steam pressurization test at 2 atms for H was performed, and a peeling test was performed by taping to check whether double plating occurred. The results are shown in Table 1.

[0009]

[Table 1]

[0010]

[Table 2]

In Table 1, the humidity resistance test result and the vapor pressure test result show changes in the appearance of the sample. It can be seen that the Ni-plated layer having the acicular structure shows a marked improvement over the Ni-plated layer having the fine layered structure. That is, it can be seen that the corrosion-resistant magnetic alloy according to the present invention has remarkably improved corrosion resistance as compared with the conventional magnetic alloy. In addition, FIG. 1 shows a scanning electron micrograph of a cross section of the Ni plating layer composed of the needle-shaped structure of Example 1 according to the present invention. It can be seen that the pattern of the needle-like structure clearly appears at a magnification of 3000. In addition, FIG. 2 shows a magnification of 50 of Comparative Example 2.
2 shows a scanning electron micrograph of a cross section of a Ni plating layer composed of a fine layered structure of No. 00. No needle-like structure is observed even at a magnification of 5000.

[0012]

The effect of the present invention is that the Ni plating film of the R-TM-B type magnetic alloy has a needle-like crystal structure of the Ni plating, which is different from the conventional concept. It is possible to eliminate the occurrence of peeling of the plating film due to the residual internal stress of the film, to greatly improve the adhesion between the magnetic body and the Ni plating film, and to obtain a Ni plating film having remarkable corrosion resistance. The effect is of great industrial utility value.

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph of a cross section of a Ni plating layer composed of a needle-shaped structure of Example 1 according to the present invention.

FIG. 2 is a scanning electron micrograph of a cross section of a Ni plating layer composed of a fine layered structure of Comparative Example 2.

[Explanation of symbols]

 None

Claims (2)

[Claims] 1. R by weight (here, one or a combination of two or more rare earth elements including Y) 5 to 40%, TM
(Where TM is Fe, Co, Ni, Ga, Al, T
i, V, Cr, Mn, Zr, Hf, Nb, Ta, Mo,
50 to 90% of one or a combination of transition metals selected from Ge, Sn, Sb and Bi), B (boron) 0.
A corrosion-resistant magnetic alloy having a Ni-plated layer composed of a needle-like structure having a length of 2 μm or more on the surface of an R-TM-B based magnetic alloy composed of 2 to 8%. 2. The surface of the Ni plating layer according to claim 1,
One or two of metal coatings such as Cu, Ni, Al, Zn, Sn, Cr and Ni-P or organic coatings such as furan resin, acrylic resin, epoxy resin, melanin resin and parylene resin. A corrosion-resistant magnetic alloy having at least one kind of coating film sequentially laminated.