JP2007273503A - Magnet and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rare-earth magnet having high magnetic characteristics and improved scratch resistance and corrosion resistance properties. <P>SOLUTION: The magnet comprises: a magnet element body containing a rare earth element, a first layer formed on the surface of the magnet element body, and a second layer laminated on the first layer. In the magnet, the first layer contains metal, and the second layer contains an alloy of Cu and at least one metal selected from Sn and Zn. The first layer is preferably one metal selected from Cu, Sn, and Zn. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnet in which a coating layer is formed on a magnet body containing a rare earth, and a method for manufacturing the same.

  Since rare earth magnets have high performance, they are widely used for motors and actuators of various devices. In particular, R-Fe-B rare earth magnets (where R is a Y element or a rare earth element) have high magnetic properties and a relatively inexpensive raw material is used, so the application range is widened. .

  However, since this rare earth magnet contains rare earth elements that are easily oxidized and iron as main components, the corrosion resistance is relatively low, and degradation of performance, variation, and the like are problems. For this reason, a method has been proposed in which surface treatment such as plating or vapor deposition is performed on the magnet body to improve the corrosion resistance, and Ni plating is widely adopted because it is inexpensive and excellent in corrosion resistance.

  However, since the Ni plating bath is acidic, there is a problem that when the magnet body is immersed in the Ni plating bath, the magnet body itself is eroded. For this reason, the plating bath can be made alkaline, and Cu having good adhesion to the magnet body is directly plated on the magnet body, and Ni, Sn, and alloys thereof are further formed thereon. Corrosion resistance is ensured by plating (for example, Patent Documents 1 to 3).

  For example, in Patent Document 1, a Cu layer and a Ni—P alloy layer are formed on an R—Fe—Co—B type rare earth magnet (where R is at least one kind of rare earth element including Y). In Patent Document 2, a Cu or Cu alloy layer on a RE-TM-B rare earth magnet (where RE is one or more of rare earth elements and TM is one or more of transition metals), and a base metal than Cu ( Ni, Sn) layer. In Patent Document 3, a Cu-layer, a Cu-Ni alloy layer, and an R-T-B rare earth magnet (where R is at least one rare earth element including Y and T is Fe or Fe and Co) Is forming.

  However, although the corrosion resistance of the rare earth magnet subjected to the above plating treatment is relatively improved, since the hardness of the metal or alloy formed on the surface is not sufficient, it is inferior in scratch resistance. A problem has arisen. That is, when the above-mentioned rare earth magnet is brought into contact with another magnet or a conveying member at the time of handling or conveyance after the plating process, there is a case where fine scratches are generated on the plating layer of the rare earth magnet due to the impact. When a fine flaw occurs in the plating layer, a part of the plating layer is peeled off, so that it floats in the air as a fine piece. Furthermore, since the magnet body comes into contact with the outside air through the generated flaws, the magnet body is oxidized and rusted, resulting in deterioration of magnetic properties.

For example, when the above magnet is used in a voice coil motor for head drive of a hard disk drive that requires high reliability, there is a problem that the voice coil motor malfunctions or fails due to fine pieces or rust peeled off from the plating layer. It was. For this reason, a rare earth magnet excellent in not only corrosion resistance but also scratch resistance has been demanded.
JP-A-1-42805 Japanese Patent Laid-Open No. 5-29119 JP 2002-332592 A

  The present invention has been made in view of such a situation, and an object thereof is to provide a magnet having high magnetic properties and excellent scratch resistance and corrosion resistance. Another object of the present invention is to provide a method for manufacturing the magnet.

  As a result of intensive studies to achieve the above object, the present inventors formed a first layer containing a metal on the surface of a magnet containing a rare earth, and further, at least one selected from Cu, Sn and Zn. By forming the second layer containing an alloy of two or more, the adhesion between the magnet body and the coating layer can be maintained, and a magnet having high scratch resistance and corrosion resistance while having high magnetic properties can be obtained. As a result, the present invention has been completed.

That is, the magnet according to the present invention is
A magnet body containing a rare earth element;
A first layer formed on the surface of the magnet body;
A magnet having a second layer laminated on the first layer,
The first layer includes a metal;
The second layer includes an alloy of Cu and at least one selected from Sn and Zn.

  By setting the magnet according to the present invention to the above-described configuration, the adhesion between the magnet body and the coating layer can be maintained, and the magnet can be excellent in scratch resistance and corrosion resistance. In addition, when said alloy which comprises a 2nd layer is formed in the surface of a magnet element | base_body, adhesiveness falls. Therefore, first, the first layer having good adhesion to the magnet body is formed as a base layer on the surface of the magnet body, and further, the second layer is formed on the surface of the first layer or the surface of another layer. By forming, the effects of the present invention can be achieved. The first layer formed on the magnet element body preferably covers the entire magnet element body without a gap, but does not necessarily need to cover the entire magnet element body. The same applies to the second layer.

  Preferably, the first layer includes one metal selected from Cu, Sn, and Zn. When the first layer is made of the above metal, the pH of the plating bath can be made alkaline while maintaining good adhesion to the magnet body, so that the magnet body is immersed in the plating bath In addition, erosion of the magnet body can be prevented.

  Preferably, the magnet body includes R (wherein R is one or more selected from rare earth elements including Y element), TM (where TM is a transition element mainly composed of Fe), and B. R-TM-B rare earth magnet.

  By making the magnet body an R-TM-B rare earth magnet, a rare earth magnet having excellent magnetic properties such as coercive force and residual magnetic flux density, and excellent corrosion resistance and scratch resistance can be obtained. .

A method for producing a magnet according to the present invention includes:
Providing a first plating bath used to form the first layer and a second plating bath used to form the second layer;
Performing wet plating using the first plating bath to form the first layer on the surface of the magnet body; and
Performing wet plating using the second plating bath, and forming the second layer stacked on the first layer.

  Preferably, the second plating bath contains at least one selected from pyrophosphate, cyanide compound and organic phosphonic acid compound.

  Since the magnet can be easily manufactured by forming the first layer and the second layer by wet plating, the productivity of the magnet can be improved. Further, the second plating bath used for forming the second layer contains at least one selected from pyrophosphate, cyanide compound and organic phosphonic acid compound, so that the second layer can be uniformly and efficiently formed. Can be formed.

Hereinafter, the present invention will be described based on embodiments shown in the drawings. put it here,
FIG. 1 is a schematic cross-sectional view of a rare earth magnet according to an embodiment of the present invention.
Magnet 2

As shown in FIG. 1, in this embodiment, the magnet 2 has a first layer 6 having a thickness T <b> 1 on the surface of the magnet body 4, and a second layer on the surface of the first layer 6. 8 is formed with a thickness T2.
Magnet element 4

  The magnet body 4 is not particularly limited as long as it is a magnet containing rare earth, but preferably R (where R is one or more of rare earth elements including Y), TM (where TM is mainly composed of Fe). And an R-TM-B rare earth magnet containing B.

  R includes at least one of Nd, Pr, Dy, Ho, and Tb, or one or more of La, Sm, Ce, Gd, Er, Eu, Pm, Tm, Yb, Lu, and Y. Those are preferred.

  In addition, when using 2 or more types of elements as R, mixtures, such as a misch metal, can also be used as a raw material.

  The content of R is preferably 5.5 to 30 atomic%. If the content of R is too small, the crystal structure of the magnet becomes a cubic structure having the same structure as α-Fe, so that a high coercive force (iHc) cannot be obtained. The residual magnetic flux density (Br) is decreased.

  When R is Nd, the corrosion resistance can be improved by substituting part of Nd with Pr. At the same time, the hydrogen occlusion property is also lowered, so that even when hydrogen gas is generated during the plating process, embrittlement of the magnet body due to hydrogen occlusion can be suppressed. In this case, the Pr substitution amount is preferably 1 to 50 atomic% of Nd.

  The TM content is preferably 42 to 90 atomic%. If the TM content is too low, Br decreases, and if it is too high, iHc decreases.

  Note that by replacing part of Fe with Co, the temperature characteristics can be improved without deteriorating the magnetic characteristics. In this case, if the Co substitution amount exceeds 50 atomic% of Fe, the magnetic properties deteriorate, so the Co substitution amount is preferably 50 atomic% or less.

  The content of B is preferably 2 to 28 atomic%. If the B content is too small, the coercive force (iHc) is insufficient because the crystal structure of the magnet has a rhombohedral structure. If the B content is too large, the B-rich nonmagnetic phase increases, resulting in a residual magnetic flux density ( Br) decreases.

  In addition, by replacing a part of B with one or more of C, P, S, and Cu, productivity can be improved and cost can be reduced. In this case, the amount of substitution is preferably 4 atomic% or less. In addition, Al, Ti, V, Cr, Mn, Bi, Nb, Ta, Mo, W, Sb, Ge, Sn, Zr, Ni, Si are used to improve coercive force, improve productivity, and reduce costs. , Hf or the like may be added. In this case, the total amount added is preferably 10 atomic% or less.

  In addition to R, Fe and B, as an inevitable impurity, Ni, Si, Al, Cu, Ca and the like may be contained in 3 atomic% or less of the whole.

The magnet body 4 in the present embodiment has a main phase with a substantially tetragonal crystal structure. The particle size of the main phase is preferably about 1 to 100 μm. And it usually contains 1-50% nonmagnetic phase by volume ratio. The magnet body 4 may be a sintered magnet or a bonded magnet (resin-bonded magnet).
1st layer

  The first layer 6 is not particularly limited as long as it is a metal (including an alloy), and may have any adhesiveness with the magnet body 4. Preferably, it is one metal selected from Cu, Sn and Zn. Since these metals have good adhesion to the magnet body 4 and can make the pH of the first plating bath used for forming the first layer 6 alkaline, it is possible during the plating process. The erosion of the magnet body 4 can be prevented. When the first layer 6 is made of an alloy constituting the second layer 8 described later, the adhesion with the magnet body 4 tends to be lowered. Therefore, it is preferable to form the first layer 6 on the surface of the magnet element body 4 as a base layer and further form the second layer 8 on the surface of the first layer 6. In particular, when the first layer 6 is made of metal (Cu, Sn, Zn) contained in the alloy constituting the second layer 8, the adhesion between the first layer 6 and the second layer 8 is also improved. Can be made. The first layer 6 formed on the magnet element body 4 preferably covers the entire magnet element body 4 without a gap, but does not necessarily need to cover the entire magnet element body 4.

The thickness T1 of the first layer 6 is preferably 1 to 30 μm, more preferably 3 to 20 μm. If T1 is too thin, pinholes are generated and sufficient adhesion to the magnet body 4 tends to be difficult to obtain. On the other hand, if T1 is too thick, the manufacturing cost in the step of forming the first layer 6 tends to increase.
Second layer

  The second layer 8 includes an alloy of Cu and at least one selected from Sn and Zn. The second layer 8 serves to protect the magnet body 4 and is formed on the surface of the first layer 6 in the present embodiment. Since simple Cu is soft, its performance to protect the magnet body 4 is low, but by forming an alloy with Cu and at least one selected from Sn and Zn, the hardness increases, and as a result, Scratch resistance is remarkably improved. However, in the case of an alloy of Cu and a metal other than Sn or Zn, the above effect is small. For example, the scratch resistance of a Cu—Ni alloy is lower than that of the above alloy.

  Each composition of the alloy of Cu constituting the second layer 8 and at least one selected from Sn and Zn is not particularly limited, but in order to ensure sufficient scratch resistance and corrosion resistance, for example, It is preferable that the Cu content in the alloy shown in FIG. In the Cu—Sn alloy, the Cu content is preferably 10 to 90 atomic%, and more preferably 10 to 80 atomic%. In the Cu—Zn alloy, the Cu content is preferably 10 to 90 atomic%, more preferably 15 to 85 atomic%. In the Cu—Sn—Zn alloy, the Cu content is preferably 10 to 90 atomic%, more preferably 35 to 75 atomic%.

The thickness T2 of the second layer 8 is preferably 1 to 30 μm, more preferably 3 to 20 μm. When T2 is too thin, the effect of the present invention tends to be difficult to obtain. On the other hand, if T2 is too thick, the manufacturing cost in the step of forming the first layer 6 tends to increase. As will be described later, the first layer 6 and the second layer 8 are formed on the surface of the magnet body 4 by wet plating.
Magnet manufacturing method

  Next, a method for manufacturing the magnet 2 according to this embodiment will be described.

  (1) First, the magnet body 4 is manufactured. It is preferable to use a powder metallurgy method for manufacturing the magnet body 4. Manufacture of the magnet body 4 by powder metallurgy is performed as follows.

  First, an alloy having a desired composition is produced using various alloy manufacturing processes such as a casting method and a strip casting method. Next, the obtained alloy is coarsely pulverized to a particle size of about 10 to 100 μm using a coarse pulverizer such as a jaw crusher, brown mill, stamp mill, etc., and then finely pulverized by a jet mill, attritor, ball mill or the like. Finely pulverize to a particle size of about 0.5-5 μm. The obtained powder is then preferably shaped in a magnetic field. The obtained molded body is sintered and rapidly cooled. The atmosphere during sintering is preferably an inert gas such as Ar gas. Thereafter, heat treatment (aging treatment) is preferably performed in an inert gas atmosphere.

  (2) Next, the surface of the obtained magnet body 4 is subjected to alkaline degreasing treatment, and then subjected to chemical etching with an acid to clean the surface of the magnet body 4. By performing this treatment, there is an advantage that the surface of the magnet body 4 can be removed and the first layer 6 can be formed reliably. Nitric acid is preferably used as the acid used in the chemical etching. In addition, in order to remove the burr | flash etc. on the surface of the magnet body 4 before alkali degreasing, barrel polishing may be performed.

  After the above acid cleaning treatment is performed, black foreign matter (smut) remains on the surface of the magnet body 4, and it is preferable to remove them by ultrasonic cleaning. Moreover, it is preferable to use a gluconic acid solution for ultrasonic cleaning. Moreover, you may perform the same water washing before and behind the ultrasonic cleaning, and in each process of the said pre-processing as needed.

  (3) Next, the first layer 6 and the second layer 8 are formed by wet plating on the surface of the magnet body 4 that has been subjected to the pretreatment described above. Specifically, the magnet body 4 is immersed in a first plating bath prepared under predetermined conditions, and the first layer 6 is formed on the surface of the magnet body 4. Among the wet platings, it is preferable to form the first layer 6 and the second layer 8 by electroplating. By using the electroplating method, the first layer 6 and the second layer 8 can be formed at low cost.

  The first plating bath used to form the first layer 6 is not particularly limited, and may be appropriately selected according to the metal constituting the first layer 6. For example, when Cu is formed as the first layer 6, a plating bath containing cuprous cyanide may be used as the first plating bath. Moreover, when forming Sn as the 1st layer 6, you may use the plating bath containing a sodium stannate for a 1st plating bath. Further, the first plating bath may contain a brightener and the like.

  The pH and bath temperature of the first plating bath are not particularly limited, and may be appropriately determined according to the composition of the first plating bath. However, if the pH is too low, rare earth elements such as Nd tend to be dissolved from the magnet body 4 and a desired shape cannot be obtained or the magnetic properties tend to be reduced. If the pH is too high, Fe Is melted from the magnet body 4 and a desired shape cannot be obtained or the magnetic properties tend to be deteriorated. Moreover, when process temperature is too low, there exists a tendency for reaction in a process liquid to be scarce and processability to fall. On the other hand, if the treatment temperature is too high, spots or the like may occur and the aesthetic appearance may be impaired.

  The treatment time in the first plating bath is not particularly limited, and may be appropriately determined according to the desired layer thickness. However, if the treatment time is too short, the treatment liquid does not sufficiently contact the surface of the magnet body 4 and the reaction is insufficient, so that there is a tendency that the uniform first layer 6 cannot be formed. On the other hand, if the treatment time is too long, the thickness of the first layer 6 exceeds 30 μm, and the manufacturing cost tends to increase.

  (4) Next, the surface of the first layer 6 is subjected to an alkaline degreasing treatment, and then the surface is sufficiently washed with pure water. By performing this treatment, there is an advantage that dirt (organic matter such as a brightener) attached to the surface of the first layer 6 can be removed, and the second layer 8 can be formed reliably.

  (5) Next, electroplating is performed on the surface of the first layer 6 using a second plating bath to form the second layer 8. Specifically, the magnet body 4 on which the first layer 6 is formed is immersed in a second plating bath prepared under predetermined conditions, and the second layer 8 is formed on the surface of the first layer 6.

  The second plating bath is not particularly limited, and may be appropriately determined according to the composition of the alloy that constitutes the second layer 8, but at least selected from pyrophosphate, cyanide, and organic phosphonic acid compound. One or more are preferably included.

  The pyrophosphate is preferably stannous pyrophosphate, stannic pyrophosphate, copper pyrophosphate, zinc pyrophosphate, potassium pyrophosphate, ammonium pyrophosphate, calcium pyrophosphate, sodium pyrophosphate, more preferably pyrolin. Stannous acid, copper pyrophosphate, zinc pyrophosphate, potassium pyrophosphate. The concentration of pyrophosphate is preferably 2 to 400 g / l, more preferably 20 to 300 g / l.

  The cyan compound is preferably cuprous cyanide, cupric cyanide, zinc cyanide, potassium cyanide, sodium cyanide, ammonium cyanide, calcium cyanide, more preferably cuprous cyanide, cyanide. Zinc halide, potassium cyanide and sodium cyanide. The concentration of the cyan compound is preferably 1 to 200 g / l, more preferably 10 to 150 g / l.

  The organic phosphonic acid compound is not particularly limited. For example, DL-1-aminoethylphosphonic acid, 2-aminoethylphosphonic acid, aminomethylphosphonic acid, tert-butylphosphonic acid, diethyl cyanophosphonate, dimethylphosphonic acid, Diethylenetriaminepentamethylenephosphonic acid, hydroxyliminobismethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonic acid, phenylphosphonic acid, diethyl cyanomethylphosphonate, nitrilotris (methylene) triphosphonic acid, diethyl phenylphosphonate, diethyl vinylphosphonate, ethylenedi Tetraethyl phosphonate, ethylenediaminetetramethylenephosphonic acid, dimethyl (2-oxoheptyl) phosphonate, dimethyl (2-oxopropyl) phosphonate Dimethyl allylphosphonate, 1,4-butanediphosphonic acid, dimethyl 2-acetoxyethylphosphonate, diethyl 3,3-dimethylcyclohex-1-enylphosphonate, methylenediphosphonic acid, 1-hydroxyethane-1,1- Diphosphonic acid, diethyl 3,3-dimethylcyclopent-1-enylphosphonate, diethyl 3-methylcyclohex-1-enylphosphonate, diethyl 3-methylcyclopent-1-enylphosphonate, aminotrimethylenephosphonic acid, (1-aminopropyl) phosphonic acid, (1-aminobutyl) phosphonic acid, (1-aminopentyl) phosphonic acid, (1-aminohexyl) phosphonic acid, (1-amino-2-methylpropyl) phosphonic acid, 1-amino-3-methylbutyl) phosphonic acid, (1-amino-2-methyl) Butyl) phosphonic acid, (1-aminooctyl) phosphonic acid, (1-amino-2,2-dimethylpropyl) phosphonic acid, (1-amino-1-methylethyl) phosphonic acid, (1-amino-1-methyl) Propyl) phosphonic acid, (1-amino-1-methylbutyl) phosphonic acid, (1-amino-1,2-dimethylpropyl) phosphonic acid, (1-amino-1,3-dimethylbutyl) phosphonic acid, (1- Amino-1-phenylmethyl) phosphonic acid, (1-amino-1-cyclopentyl) phosphonic acid, (1-amino-1-cyclohexyl) phosphonic acid, 3-aminopropylphosphonic acid, (2-oxo-4-phenylbutyl) ) Dimethyl phosphonate, diethyl 3,3-diethoxypropyl phosphonate and the like. The concentration of the organic phosphonic acid compound is preferably 10 to 300 g / l, more preferably 30 to 200 g / l.

  Since at least one or more selected from the above-described pyrophosphate, cyanide compound and organic phosphonic acid compound is contained in the second plating bath, the throwing power of the plating is improved, so that the second layer 8 is more efficient. Can be obtained. Further, the second plating bath may contain a brightener and the like.

  The pH of the second plating bath is preferably alkaline, but is not particularly limited as long as it is alkaline, and may be appropriately determined according to the composition of the second plating bath. If the pH of the second plating bath is too high, the hydroxide tends to eutect and there is a tendency that sufficient hardness cannot be obtained. On the other hand, if the pH of the second plating bath is too low, the plating bath tends to become unstable.

  The bath temperature of the second plating bath is not particularly limited, and may be appropriately determined according to the composition of the compound contained in the bath. However, when the treatment temperature is too low, the reaction in the treatment liquid is poor and the processability tends to decrease. On the other hand, if the treatment temperature is too high, spots or the like may occur and the aesthetic appearance may be impaired.

  The treatment time in the second plating bath is not particularly limited, and may be appropriately determined according to the desired layer thickness. However, if the treatment time is too short, the treatment liquid does not sufficiently contact the surface of the first layer 6, and the reaction is insufficient and the uniform second layer 8 tends not to be formed. On the other hand, if the treatment time is too long, the thickness T2 of the second layer 8 exceeds 30 μm, and the manufacturing cost tends to increase.

  (6) The magnet body 4 on which the second layer 8 is formed by being immersed in the second plating bath is washed with pure water and dried. At this time, drying is usually carried out at 80 to 150 ° C. to remove moisture on the surface, but it is also preferable to immerse in alcohol and air dry for simplification of the process.

  (7) By passing through the above process, the magnet 2 which concerns on this embodiment shown in FIG. 1 is manufactured.

  The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.

  For example, in the above-described embodiment, the second layer 8 is formed on the surface of the first layer 6, but another coating layer is formed between the first layer 6 and the second layer 8. Also good. Alternatively, another coating layer may be formed on the surface of the second layer 8.

Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.
Example 1

  An ingot having a composition of 27.4Nd-3Dy-1B-68.6Fe (numbers are weight ratios) prepared by powder metallurgy was pulverized by a stamp mill and a ball mill to obtain an alloy fine powder having the above composition. The obtained alloy fine powder was press-molded in a magnetic field to obtain a compact. This molded body was sintered under the conditions of holding temperature: 1100 ° C. and holding time: 1 hour, and subjected to aging treatment under the conditions of Ar gas atmosphere, holding temperature: 600 ° C., holding time: 2 hours, and sintered body Got. The obtained sintered body was processed into a size of 20 × 20 × 2 (mm), and further chamfered by barrel polishing to obtain a magnet body. In addition, the composition by the atomic ratio of this magnet body was 12.4Nd-1.2Dy-6.1B-80.3Fe.

  Next, the magnet body sample is subjected to an alkaline degreasing treatment, an acid washing treatment with a nitric acid solution, and an ultrasonic washing treatment with a gluconic acid solution, and a first layer and a second layer are formed by a barrel plating method described below. did.

First, the composition of the first plating bath for forming the first layer is as follows: cuprous cyanide: 25 g / l, sodium cyanide: 35 g / l, sodium carbonate: 30 g / l, sodium hydroxide: 10 g / l It was. The first plating bath was adjusted to pH: 12.5 and bath temperature: 45 ° C. The magnet body obtained above was immersed in this first plating bath and plated under a current density of 0.2 A / dm ² until the thickness T1 of the first layer reached 4 μm.

Next, the magnet body on which the first layer was formed was subjected to the alkali degreasing process and the ultrasonic cleaning process, and then a second layer was further formed. The composition of the second plating bath for forming the second layer is as follows: sodium stannate: 100 g / l, sodium cyanide: 25 g / l, cuprous cyanide: 13 g / l, sodium hydroxide: 10 g / l did. This second plating bath was prepared at a pH of 12.0 and a bath temperature of 65 ° C. The magnet body obtained above was immersed in this second plating bath and plated under the condition of a current density of 0.2 A / dm ² until the thickness T2 of the second layer was 6 μm.

  The magnet on which the first layer and the second layer were formed was washed with pure water and further dried to obtain a rare earth magnet sample. As a result of EPMA (electron probe microanalysis) observation of the obtained rare earth magnet sample, it was confirmed that the first layer was made of a uniform Cu and the second layer was made of a Cu—Sn alloy having a uniform composition. Moreover, Cu content in a Cu-Sn alloy was 60 atomic%.

The above rare earth magnet samples were evaluated for the properties of adhesion, scratch resistance, and corrosion resistance between the magnet body and the first layer by the method described below. Further, a combined test combining the evaluation of scratch resistance and the evaluation of corrosion resistance was performed as follows.
Adhesion test

About the magnet in which the 1st layer and the 2nd layer were formed, the adhesiveness of a magnet element body and the 1st layer was evaluated by the cross-cut tape method (JIS K5400). That is, a grid pattern (100 locations) with a 1 mm interval is made in a 1 cm square region of the magnet surface on which the first layer and the second layer are formed. On top of that, one tape was applied, and when the tape was peeled off, the adhesion was evaluated based on the number of places where the first layer did not peel from the magnet body. (Adhesiveness between magnet body and first layer) = (location where the first layer was not peeled) / 100. For example, in the case where there is only one place where the first layer is peeled out of 100 places, the above adhesiveness is 99/100. Adhesiveness made 100/100 favorable. The results are shown in Table 1.
Scratch resistance test

In order to evaluate the scratch resistance, sandpaper (# 320) was laid on a flat plate inclined at 45 °, and the sample was slid on the sandpaper. About the sample after making it slide, the presence or absence of the wear trace was observed visually. A sample in which no wear mark was observed was indicated by “◯”, and a sample in which the wear mark was observed was indicated by “x”. The results are shown in Table 1.
Corrosion resistance test

The corrosion resistance was evaluated by holding the sample for 400 hours in an environment of a temperature of 60 ° C. and a relative humidity of 95%. The surface state of the sample after the test was visually observed to observe rust and swelling due to peeling of the first layer. A sample in which no rust or blister was observed was designated as “◯”, and a sample in which rust or blister was observed was designated as “x”. Further, the magnetic properties (residual magnetic flux density Br and coercive force iHc) before and after the test were measured with a vibrating sample magnetometer (VSM), and the maximum energy product (BH) max was calculated. The decrease rate of (BH) max before and after the test was calculated from (BH) max of the sample before the test and (BH) max of the sample after the test. The decrease rate was 3% or less. The results are shown in Table 1.
Combined test (scratch and corrosion resistance)

As a combined test, a test combining the above scratch resistance test and corrosion resistance test was performed. That is, first, a scratch resistance test was performed, and a corrosion resistance test was further performed on the sample after the scratch resistance test. The surface condition and the reduction rate of (BH) max were evaluated for the samples after the scratch resistance test and the corrosion resistance test. The results are shown in Table 1.
Example 2

A magnet body was manufactured in the same manner as in Example 1 except that the second plating bath for forming the second layer had the following composition and conditions, and the first layer and the second layer were formed.
Stannous pyrophosphate: 12 g / l,
Potassium cyanide: 50 g / l,
Cuprous cyanide: 20 g / l,
Potassium pyrophosphate: 100 g / l,
pH: 9.5
Bath temperature: 60 ° C.
It was confirmed by observation of EPMA that the obtained sample was made of Cu having a uniform first layer and a Cu-Sn alloy having a uniform composition in the second layer. Moreover, Cu content in a Cu-Sn alloy was 55 atomic%. Furthermore, the same evaluation as Example 1 was performed about the obtained sample. The results are shown in Table 1.
Example 3

A magnet body is manufactured in the same manner as in Example 1 except that the first plating bath for forming the first layer and the second plating bath for forming the second layer have the following composition and conditions. Then, the first layer and the second layer were formed.
First plating bath sodium stannate: 105 g / l,
Sodium hydroxide: 10 g / l,
pH: 12.5
Bath temperature: 60 ° C.
Second plating bath sodium stannate: 100 g / l,
Copper sulfate: 20 g / l,
Aminotrimethylenephosphonic acid: 180 g / l,
Sodium hydroxide: 40 g / l,
pH: 8.5,
Bath temperature: 60 ° C.
The obtained sample was confirmed by EPMA observation that the first layer was made of a uniform Sn and the second layer was made of a Cu—Sn alloy having a uniform composition. Moreover, Cu content in a Cu-Sn alloy was 60 atomic%. Furthermore, the same evaluation as Example 1 was performed about the obtained sample. The results are shown in Table 1.
Example 4

A magnet body was manufactured in the same manner as in Example 1 except that the second plating bath for forming the second layer had the following composition and conditions, and the first layer and the second layer were formed.
Cuprous cyanide: 17 g / l,
Zinc cyanide: 60 g / l,
Sodium cyanide: 60 g / l,
Sodium hydroxide: 60 g / l,
pH: 13.0,
Bath temperature: 35 ° C.
It was confirmed by observation of EPMA that the obtained sample was made of Cu having a uniform first layer and a Cu—Zn alloy having a uniform composition in the second layer. Moreover, Cu content in a Cu-Zn alloy was 25 atomic%. Furthermore, the same evaluation as Example 1 was performed about the obtained sample. The results are shown in Table 1.
Example 5

The first plating bath for forming the first layer has the following composition and conditions, and the second plating bath for forming the second layer is the same as the second plating bath of Example 4, except that A magnet body was manufactured in the same manner as in Example 1, and the first layer and the second layer were formed.
Zinc cyanide: 60 g / l,
Sodium cyanide: 40 g / l,
Sodium hydroxide: 80 g / l,
Thiourea: 0.5 g / l,
pH: 13.0,
Bath temperature: 30 ° C.
It was confirmed by EPMA observation that the obtained sample was made of a uniform Zn in the first layer and a Cu—Zn alloy having a uniform composition in the second layer. Moreover, Cu content in a Cu-Zn alloy was 25 atomic%. Furthermore, the same evaluation as Example 1 was performed about the obtained sample. The results are shown in Table 1.
Example 6

A magnet body was manufactured in the same manner as in Example 1 except that the second plating bath for forming the second layer had the following composition and conditions, and the first layer and the second layer were formed.
Cuprous cyanide: 3 g / l,
Zinc cyanide: 5 g / l,
Sodium stannate: 2 g / l,
Sodium cyanide: 20 g / l,
Sodium carbonate: 30 g / l,
pH: 12.5
Bath temperature: 65 ° C.
The obtained sample was confirmed by EPMA observation that the first layer was made of Cu having a uniform composition and the second layer was made of a Cu—Sn—Zn alloy having a uniform composition. Further, the Cu content in the Cu—Sn—Zn alloy was 55 atomic%. Furthermore, the same evaluation as Example 1 was performed about the obtained sample. The results are shown in Table 1.
Example 7

The first plating bath for forming the first layer has the following composition and conditions, and the second plating bath for forming the second layer is the same as the second plating bath of Example 6, except that A magnet body was manufactured in the same manner as in Example 1, and the first layer and the second layer were formed.
Nickel sulfate: 300 g / l,
Nickel chloride: 45 g / l,
Boric acid: 35 g / l,
pH: 4.0,
Bath temperature: 45 ° C.
It was confirmed by EPMA observation that the obtained sample was made of Ni with a uniform first layer and a Cu—Sn—Zn alloy with a uniform composition in the second layer. The Cu content in the Cu—Sn—Zn alloy was 55 atomic%. Furthermore, the same evaluation as Example 1 was performed about the obtained sample. The results are shown in Table 1.
Comparative Example 1

The first plating bath for forming the first layer is the same as the first plating bath of Example 7, the thickness T1 of the first layer is 10 μm, and the second layer is not formed. Similarly, a magnet body was manufactured and a first layer was formed. In the obtained sample, it was confirmed by EPMA observation that the first layer was made of uniform Ni. Furthermore, the same evaluation as Example 1 was performed about the obtained sample. The results are shown in Table 1.
Comparative Example 2

The first plating bath for forming the first layer was subjected to electroless plating with the following composition and conditions, the thickness T1 of the first layer was 10 μm, and the second layer was not formed. Similarly, a magnet body was manufactured and a first layer was formed.
Nickel sulfate: 20 g / l,
Sodium hypophosphite: 15 g / l,
Sodium citrate: 30 g / l,
Ammon chloride: 30 g / l,
pH: 9.5
Bath temperature: 45 ° C.
In the obtained sample, it was confirmed by EPMA observation that the first layer was made of a Ni—P alloy having a uniform composition. Furthermore, the same evaluation as Example 1 was performed about the obtained sample. The results are shown in Table 1.
Comparative Example 3

A magnet body was manufactured in the same manner as in Example 1 except that the second plating bath for forming the second layer had the following composition and conditions, and the first layer and the second layer were formed.
Nickel sulfate: 65 g / l,
Copper sulfate: 2 g / l,
Glycine: 60 g / l,
Sodium hydroxide: 1 g / l,
pH: 7.0,
Bath temperature: 60 ° C.
The obtained sample was confirmed by EPMA observation that the first layer was made of Cu having a uniform composition and the second layer was made of a Cu—Ni alloy having a uniform composition. Moreover, Cu content in a Cu-Ni alloy was 70 atomic%. Furthermore, the same evaluation as Example 1 was performed about the obtained sample. The results are shown in Table 1.
Comparative Example 4

The first plating bath for forming the first layer is the same as the second plating bath of Example 1, except that the thickness T1 of the first layer is 10 μm and the second layer is not formed. In the same manner as described above, a magnet body was manufactured and a first layer was formed. In the obtained sample, it was confirmed by EPMA observation that the first layer was made of a Cu—Sn alloy having a uniform composition. Moreover, Cu content in a Cu-Sn alloy was 60 atomic%. Furthermore, the same evaluation as Example 1 was performed about the obtained sample. The results are shown in Table 1.
Comparative Example 5

The first plating bath for forming the first layer is the same as the second plating bath of Example 4, except that the thickness T1 of the first layer is 10 μm and the second layer is not formed. In the same manner as described above, a magnet body was manufactured and a first layer was formed. In the obtained sample, it was confirmed by EPMA observation that the first layer was made of a Cu—Zn alloy having a uniform composition. Moreover, Cu content in a Cu-Zn alloy was 25 atomic%. Furthermore, the same evaluation as Example 1 was performed about the obtained sample. The results are shown in Table 1.
Comparative Example 6

  Example 1 except that the first plating bath for forming the first layer was the same as the second plating bath of Example 6, the thickness T1 of the first layer was 10 μm, and the second layer was not formed. In the same manner as described above, a magnet body was manufactured and a first layer was formed. In the obtained sample, it was confirmed by EPMA observation that the first layer was made of a Cu—Sn—Zn alloy having a uniform composition. Further, the Cu content in the Cu—Sn—Zn alloy was 55 atomic%. Furthermore, the same evaluation as Example 1 was performed about the obtained sample. The results are shown in Table 1.

  From Table 1, it can confirm that the sample of Examples 1-7 has obtained the favorable result about all of adhesiveness, scratch resistance, corrosion resistance, and a combined test (scratch resistance + corrosion resistance).

  On the other hand, since the samples of Comparative Examples 1 and 2 are only the first layer of Ni (Comparative Example 1) and Ni-P (Comparative Example 2), the adhesion with the magnet body is good. . However, abrasion marks were observed in the scratch resistance test. As a result, when only the corrosion resistance test is performed, a decrease in (BH) max is not observed, but when a combined test of the scratch resistance test and the corrosion resistance test is performed, wear marks are generated in the scratch resistance test. Therefore, it can be confirmed that rust is generated in the magnet body, and (BH) max before and after the combined test is greatly reduced.

  Further, when the first layer is made of Cu and the second layer is made of Cu—Ni (Comparative Example 3), the first layer is made of Cu, so that the adhesion with the magnet body is good. However, since the hardness of Cu—Ni as the second layer is not sufficient, wear marks are generated in the scratch resistance test. As a result, as in Comparative Examples 1 and 2, (BH) max is large in the composite test. It can confirm that it has fallen.

  The alloys of the second layer of the samples of Examples 1, 4, and 6 were used as the first layer, and the samples of Comparative Examples 4 to 6 in which the second layer was not formed were the adhesion between the first layer and the magnet body. It can be confirmed that it is inferior. As a result, in both the corrosion resistance test and the combined test, it can be confirmed that the surface of the sample after the test is swollen and the rate of decrease in (BH) max before and after the test is increased.

FIG. 1 is a schematic cross-sectional view of a rare earth magnet according to an embodiment of the present invention.

Explanation of symbols

2 ... Rare earth magnet 4 ... Magnet element body 6 ... First layer 8 ... Second layer

Claims (5)

A magnet body containing a rare earth element;
A first layer formed on the surface of the magnet body;
A magnet having a second layer laminated on the first layer,
The first layer includes a metal;
The magnet, wherein the second layer includes an alloy of Cu and at least one selected from Sn and Zn.   The magnet according to claim 1, wherein the first layer includes one metal selected from Cu, Sn, and Zn.   The magnet body is R-TM containing R (wherein R is one or more selected from rare earth elements including Y element), TM (where TM is a transition element mainly composed of Fe) and B. The magnet according to claim 1, which is a −B-based rare earth magnet. A method for producing the magnet according to claim 1,
Providing a first plating bath used to form the first layer and a second plating bath used to form the second layer;
Performing wet plating using the first plating bath to form the first layer on the surface of the magnet body; and
Performing wet plating using the second plating bath, and forming the second layer laminated on the first layer.   The method for producing a magnet according to claim 4, wherein the second plating bath contains at least one selected from pyrophosphate, a cyanide compound, and an organic phosphonic acid compound.

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