JP2007273850A - Magnet member, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnet member that can have improved magnetic characteristics regardless of miniaturization, and can have improved corrosion resistance and scratch resistance; and to provide a manufacturing method of the magnet member. <P>SOLUTION: The magnet member 2 comprises: a magnet element body 4, and a first coating layer 6. The first coating layer 6 covers the magnet element body 4 and contains Ni and Mo. The first coating layer 6 is preferably non-magnetic. Or the magnet element body 4 is preferably a rare-earth magnet. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnet member having a magnet body such as a rare earth magnet and a coating layer covering the magnet body, and a method for manufacturing the magnet member.

  R-TM-B magnets containing R (R is one or more of rare earth elements including Y), TM (TM is a transition element mainly composed of Fe) and boron, that is, rare earth magnets have excellent magnetic properties. It is known to have. For this reason, such rare earth magnets are widely used as permanent magnet members for motors and actuators of various devices.

  However, since this rare earth magnet contains a rare earth element which is easily oxidized as a main component and iron, the corrosion resistance is relatively low, and degradation of performance, variation, and the like become problems. As a countermeasure, a method has been proposed in which surface treatment such as plating or vapor deposition is performed on a magnet body (rare earth magnet) to improve corrosion resistance. In particular, magnet members plated with nickel that are inexpensive and excellent in corrosion resistance are widely used (see Patent Document 1).

  In recent years, along with miniaturization and high performance of HDD, CD, DVD related devices, etc., miniaturization and improvement of magnetic properties are also required for magnet members used for them. As the magnet member is reduced in size, the proportion of the plating film in the magnet member increases. Therefore, the smaller the magnet member is, the greater the influence of the magnetic properties of the plating film on the magnetic properties of the entire magnet member. Nickel, which is frequently used as a plating film for rare earth magnets, is a magnetic material and has a saturation magnetic flux density of about 0.6T. Therefore, in a magnet member having a nickel plating film, the magnetism of the magnet body is shielded by the nickel plating film as the magnet member is miniaturized. As a result, there is a problem that the magnetic properties of the entire magnet member are deteriorated. That is, in the downsized magnet member, the magnetic properties of the magnet member are reduced by the thickness of the nickel plating film. This is a phenomenon that can be ignored with a large neodymium magnet or the like, but the problem becomes apparent with small, thin-film magnet members.

In addition, when using the above-mentioned magnet members for hard disk drive head drive voice coil motors, hybrid car motors, generators, etc., voice coils that require high reliability due to fine pieces and rust peeled off from the plating film There is a risk of motor malfunction or failure. For this reason, a magnet member excellent not only in corrosion resistance and magnetic properties but also in scratch resistance (hardness) has been demanded.
JP 2002-212775 A

  The present invention has been made in view of such a situation, and the object thereof is a magnet that can have excellent magnetic properties and excellent corrosion resistance and scratch resistance even when downsized. It is to provide a member.

  As a result of intensive studies to achieve the above object, the present inventors have coated the surface of the magnet body with an alloy containing Ni and Mo, so that the magnet has excellent magnetic properties, corrosion resistance, and scratch resistance. The present inventors have found that a member can be obtained and have completed the present invention.

That is, the magnet member according to the present invention is
A magnet body;
A first coating layer,
The first coating layer covers the magnet body;
The first coating layer includes Ni and Mo.

Preferably, the first coating layer is nonmagnetic. Non-magnetic means that the residual magnetic flux density (Br) of the first coating layer is 10 ⁻³ T or less (10 G or less).

  Preferably, the magnet body is a rare earth magnet.

  By coating (plating) the magnet body with a non-magnetic Ni—Mo alloy having a lower residual magnetic flux density (Br) than Ni which is a conventional plating film, the plating film shields the magnetism of the magnet body. Can be prevented. As a result, the magnetic characteristics of the magnet member can be improved. Moreover, the corrosion resistance and scratch resistance of the magnet member can be improved by covering the magnet body with the first covering layer.

  Preferably, the first coating layer contains at least one element of Sn, W, Cu, Ti, Zn, P, and B.

  By containing said element in a 1st coating layer, the 1st coating layer can have the outstanding scratch resistance (high hardness) compared with Ni which is the conventional plating film. Therefore, the scratch resistance of the magnet member covered with the first covering layer can also be improved.

  Preferably, the Mo content in the first coating layer is 20 to 80 atomic% with respect to the entire first coating layer.

  By setting the Mo content in the first coating layer within the above range, the first coating layer can be made nonmagnetic. Therefore, it can prevent that a plating film (1st coating layer) shields the magnetism of a magnet element body. As a result, the magnetic characteristics of the magnet member can be improved.

  It is preferable that the first covering layer is composed of a columnar structure that is long in a direction perpendicular to the magnet body.

  Since the first coating layer is composed of a columnar structure of Ni—Mo alloy, the space between the columnar structures becomes dense. That is, the first coating layer becomes dense. As a result, the corrosion resistance of the magnet member can be improved.

  Preferably, the first coating layer has a Vickers hardness of 400 or more.

Preferably, the magnet member is
The magnet body;
The first coating layer;
A second coating layer,
The second coating layer covers the magnet body;
The first coating layer covers the magnet body coated on the second coating layer;
The second coating layer contains Cu and is nonmagnetic.

  When the magnet body is covered with the second coating layer containing Cu and being nonmagnetic, the magnetism of the magnet body is not shielded by the second coating layer. In addition, by forming the second non-dressing so as to contact the rare earth magnet as the magnet body, the rare earth magnet main phase is completely composed of the rare earth rich phase and the nonmagnetic second coating layer. Covered with. As a result, the magnet member can function as a permanent magnet. In this way, the magnetic properties of the magnet member can be improved.

  Furthermore, since the 2nd coating layer containing Cu is soft, it functions as a cushion (impact buffer material) which can endure the impact when the magnet member is dropped. As a result, the scratch resistance of the magnet member can be improved.

  Furthermore, by forming the first coating layer via the second coating layer, the adhesion between the magnet body, the second coating layer, and the first coating layer can be improved.

The method of manufacturing the magnet member having the magnet body and the first coating layer includes:
Forming the magnet body; and
A step of coating the magnet body with the first coating layer to form a magnet member;
Heat-treating the magnet member.

The method of manufacturing the magnet member having the magnet body, the first coating layer, and the second coating layer,
Forming the magnet body; and
Coating the magnet body with the second coating layer;
A step of covering the magnet body covered with the second covering layer with the first covering layer to form a magnet member;
Heat-treating the magnet member.

  By heat-treating the magnet member, the hardness (scratch resistance) of the Ni—Mo alloy (first coating layer) can be improved. As a result, the scratch resistance of the magnet member can also be improved.

  Preferably, the magnet member is heat-treated at an ambient temperature of 100 to 450 ° C.

  By heat-treating the magnet member at the above atmospheric temperature, the hardness (scratch resistance) of the Ni—Mo alloy (first coating layer) is improved without deteriorating the coercive force of the magnet body (rare earth magnet). Can do. As a result, the scratch resistance of the magnet member can be improved.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is a schematic sectional view of a magnet member according to a first embodiment of the present invention,
FIG. 2 is a schematic cross-sectional view of a magnet member according to the second embodiment of the present invention.

First Embodiment As shown in FIG. 1, in the first embodiment, the magnet member 2 is composed of a magnet element body 4 and a first covering layer 6. The first coating layer 6 covers the surface of the magnet body 4. Note that the first covering layer 6 does not necessarily need to cover the entire surface of the magnet element body 4, and may cover a part of the surface of the magnet element body 4. Preferably, the first coating layer 6 covers the entire surface of the magnet body 4.

Magnet element 4
First, the magnet body 4 will be described.
The magnet body 4 is not particularly limited, but a rare earth magnet is preferably used. Although it does not specifically limit as a rare earth magnet, R (However, R is 1 or more types of rare earth elements containing Y), R-Fe-B type rare earth magnet containing Fe and B is preferable. In this R—Fe—B rare earth magnet, the contents of R, Fe and B are preferably 5.5 atomic% ≦ R ≦ 30 atomic%, 42 atomic% ≦ Fe ≦ 90 atomic%, 2 atomic% ≦ B ≦ 28 atomic%.

  When a rare earth magnet is produced by a sintering method, the following composition is preferred.

  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 low, the crystal structure of the magnet becomes a cubic structure having the same structure as that of α-Fe, so that a high coercive force (iHc) cannot be obtained. The residual magnetic flux density (Br) is decreased.

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

The content of B is preferably 2 to 28 atomic%.
If the B content is too small, the magnet's crystal structure becomes a rhombohedral structure, so the coercive force (iHc) is insufficient, and if it is too large, the B-rich nonmagnetic phase increases, so the residual magnetic flux density ( Br) 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.

  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.

  Furthermore, 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.

  The rare earth magnet 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 thickness of the magnet body 4 (rare earth magnet) in the magnetization direction is not particularly limited, but is preferably 1.5 mm or less. In the small magnet body 4, the thickness in the magnetization direction is about 1.5 mm or less, and the magnet surface having the magnetization direction as a normal line is about 2 cm ² or less. When the Ni plating film is formed on the magnet body 4 having such a size, the magnetic flux of the magnet body 4 is reduced by about 0.5% or more. Therefore, by forming the nonmagnetic first coating layer 6 instead of the Ni plating film, it is possible to prevent magnetic shielding against the magnet element body as compared with the case of the Ni plating film. As a result, the magnetic flux of the entire magnet member 6 can be increased.

Method for Forming Magnet Element Body Magnet element body 4 (rare earth magnet) as described above is manufactured by a powder metallurgy method as described below.

  First, a metal or alloy as a raw material is blended so as to have a desired composition. And the compounded raw material is melt | dissolved in a vacuum or inert gas atmosphere, and it casts after that, and obtains the alloy which has a desired composition. Although it does not specifically limit as a casting method, For example, the strip casting method etc. are mentioned. The strip casting method is a method of continuously casting a thin alloy plate by supplying a molten alloy in a liquid state onto a rotating roll. The alloy obtained by casting does not necessarily have to be a single alloy having the final composition. For example, it may be a mixture of a plurality of types of alloys having different compositions. Further, the shape of the alloy is not particularly limited, and is not necessarily a thin plate shape, and may be an ingot, for example.

  Then, the obtained alloy is pulverized using a jaw crusher or the like to form an alloy lump having a size of about 5 to 100 mm square, and hydrogen is occluded in the obtained alloy lump. Next, the alloy lump subjected to the hydrogen storage treatment is roughly pulverized to obtain an alloy powder. Note that when coarse pulverization is performed, hydrogen is occluded in advance in the alloy lump so that pulverization can proceed from the surface in a self-destructive manner. Thereafter, the obtained alloy powder is subjected to a dehydrogenation treatment by heat treatment.

  Next, about 0.03 to 0.4% by weight of a grinding aid is added to the dehydrogenated alloy powder. By adding a grinding aid, the amount of residual carbon after sintering can be reduced, and the magnetic properties can be improved. In addition, although it does not specifically limit as a grinding | pulverization adjuvant, For example, a fatty acid type compound can be used.

  Next, the alloy powder to which the grinding aid is added is finely ground using a jet mill or the like. The pulverization is preferably performed until, for example, the particle size of the alloy powder is about 1 to 10 μm, particularly about 3 to 6 μm.

  Next, the powder obtained by fine pulverization is preferably molded in a magnetic field to obtain a molded body. In this case, the magnetic field strength is preferably about 400 to 1600 kA / m, and the molding pressure is preferably about 50 to 500 MPa.

  The obtained molded body is sintered at 1000 to 1200 ° C. for 0.5 to 5 hours and rapidly cooled. Thereafter, heat treatment (aging treatment) is preferably performed in an inert gas atmosphere at 500 to 900 ° C. for 1 to 5 hours. In addition, it is preferable to set each process to heat processing (aging treatment) in a non-oxidizing gas atmosphere, such as a vacuum or Ar gas, in order to prevent oxidation.

  The magnet body 4 (rare earth magnet) manufactured in this way is excellent in magnetic characteristics particularly when it is a neodymium magnet in which R is Nd, but has a negative thermal expansion coefficient in the direction perpendicular to the C axis. It is known to have.

First covering layer 6
Next, the first coating layer 6 will be described.

The first coating layer 6 is an alloy layer containing Ni and Mo. Preferably, the first coating layer is nonmagnetic. The residual magnetic flux density (Br) of the first coating layer 6 (Ni—Mo alloy) is preferably 10 ⁻³ T or less (10 G or less), more preferably 10 ⁻⁴ T or less.

  Conventionally, the saturation magnetic flux density of Ni that is frequently used as the plating film of the magnet body 4 is about 0.6T. Thus, conventionally, since the magnet body 4 is plated with Ni having magnetism, the plating film shields the magnetism of the magnet body 4. As a result, the magnetic flux of the entire magnet member 2 is reduced. Further, as the magnet member 2 is downsized and the volume ratio of the Ni plating film in the entire magnet member 2 increases, the degree to which the Ni plating film shields the magnetism of the magnet body 4 increases, and the magnetic flux in the magnet member 2 decreases. Becomes prominent.

  Therefore, by covering the magnet element body 4 with the first covering layer 6 made of a nonmagnetic Ni—Mo alloy, the first covering layer can be prevented from shielding the magnetism of the magnet element body 4. As a result, the magnetic characteristics (magnetic flux) of the magnet member 2 can be improved compared to the case of the Ni plating film.

  Further, by covering the magnet element body 4 with the first covering layer 6 described above, the magnet member 2 can have corrosion resistance. The 1st coating layer 6 which has a Ni-Mo alloy as a main component generates a little molybdate ion in aqueous solution. This molybdate ion is adsorbed on the active sites on the surface of the Ni—Mo alloy layer and acts as an inhibitor. As a result, the Ni—Mo alloy layer (first coating layer 6) can have extremely high corrosion resistance.

  Preferably, the Mo content in the first coating layer 6 is 20 to 80 atomic% with respect to the entire first coating layer. By setting the Mo content in the first coating layer 6 within this range, the first coating layer 6 can be made nonmagnetic.

  Preferably, the first coating layer 6 contains at least one element of Sn, W, Cu, Ti, Zn, P, and B. By containing these elements in the first coating layer 6, the first coating layer 6 can have superior scratch resistance (high hardness) compared to Ni which is a conventional plating film. Therefore, the scratch resistance of the magnet member 2 covered with the first covering layer 6 can also be improved.

  The total content (atomic%) of the above elements in the first coating layer 6 is preferably smaller than the total content of Ni and Mo (atomic%) in the first coating layer 6. As a result, the first coating layer 6 that is non-magnetic and has excellent scratch resistance can be obtained.

  In addition, content of W contained in the 1st coating layer 6 is although it does not specifically limit, Preferably, it is 15 atomic% or more with respect to the whole 1st coating layer, More preferably, it is 22 atomic% or more. By setting the W content to 15 atomic% or more, the first coating layer 6 can be made nonmagnetic. Further, by setting the W content to 22 atomic% or more, the first coating layer 6 becomes amorphous, and the magnetism of the first coating layer 6 can be further reduced.

  Further, the content of P contained in the first coating layer 6 is not particularly limited, but is preferably greater than 8 atomic% with respect to the entire first coating layer. Further, the content of B contained in the first coating layer 6 is not particularly limited, but is preferably greater than 3 atomic% with respect to the entire first coating layer. The 1st coating layer 6 can be made nonmagnetic by making each content rate of P and B into said value.

  Preferably, the first coating layer 6 is composed of a columnar structure that is long in the direction perpendicular to the magnet body 4. When the 1st coating layer 6 is comprised from the columnar structure | tissue of Ni-Mo alloy, between columnar structures | tissues will become dense. That is, the first coating layer 6 becomes dense. As a result, the corrosion resistance of the magnet member 2 can be improved.

  The Vickers hardness of the first coating layer 6 is preferably 400 or more, more preferably 450 or more and 900 or less, and still more preferably 450 or more and 600 or less. The magnet member 2 is mechanically fixed or bonded to a yoke or the like. In many cases, a silicon steel plate is subjected to electroless NiP plating on the yoke. The hardness of the electroless NiP plating is 450 or more and 600 or less. The heat-treated electroless NiP plating has a hardness of 500 or more and 900 or less. It is preferable that the 1st coating layer 6 which coat | covers the magnet member 2 has hardness equivalent to these electroless NiP plating.

  Although the thickness T1 of the 1st coating layer 6 is not specifically limited, Preferably, it is 3-30 micrometers, More preferably, it is 5-10 micrometers. When the thickness T1 is too thin, there is a possibility that a pinhole resulting from the unevenness of the surface of the magnet body 4 (the surface of the rare earth magnet) is formed. When thickness T1 is too thick, the dimension of the magnet member 2 will become large. That is, in the magnet member 2, the volume ratio of the non-magnetic first coating layer 6 is increased. As a result, the magnetic properties per volume of the magnet member 6 are deteriorated. Therefore, by setting the thickness T1 of the first covering layer 6 within the above range, these problems can be prevented.

Method for Forming First Covering Layer 6 Next, the first covering layer 6 will be described. First, the surface of the 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, the surface of the magnet body 4 can be removed, and the first coating layer 6 can be reliably formed. 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.

  Next, the first coating layer 6 is formed on the surface of the magnet body 4 that has been subjected to the pretreatment described above. The method for forming the first coating layer 6 is not particularly limited, but is preferably formed by wet plating because of excellent productivity. In the present embodiment, it is preferable to appropriately select electrolytic plating, electroless plating, or the like according to the composition of the alloy constituting the first coating layer 6. Specifically, the magnet body 4 is immersed in a plating bath in which the plating solution is adjusted to a predetermined condition, and the first coating layer 6 is formed on the surface of the magnet body 4.

  The plating solution used for forming the first coating layer 6 is not particularly limited, and a plating solution containing a metal constituting the first coating layer 6 may be appropriately selected. In the present embodiment, the first coating layer 6 contains Ni and Mo. Therefore, a plating solution containing a metal salt compound of these elements may be used.

  The nickel salt compound contained in the plating solution is not particularly limited, and examples thereof include nickel sulfate, nickel chloride, nickel nitrate, nickel sulfamate, nickel hydroxide, nickel carbonate, and nickel pyrophosphate.

  The molybdenum salt compound contained in the plating solution is not particularly limited, and examples thereof include molybdenum sulfate, sodium molybdate, potassium molybdate, ammonium molybdate, and molybdenum trioxide.

  In addition, when the first coating layer 6 contains at least one element of Sn, W, Cu, Ti, Zn, P, and B, these metal salt compounds may be contained in the plating solution.

  The pH and bath temperature of the plating bath are not particularly limited, and may be determined as appropriate according to the composition of the plating solution. The pH of the plating bath can be adjusted using, for example, a hydroxide salt. Although it does not specifically limit as a hydroxide salt, For example, potassium hydroxide, sodium hydroxide, calcium hydroxide etc. are mentioned. In addition to the hydroxide salt, boric acid may be contained as a pH buffer material.

  The treatment time in the plating bath is not particularly limited, and may be determined as appropriate according to the desired layer thickness T1. If the treatment time is too short, the treatment liquid does not sufficiently contact the surface of the magnet body 4 and the reaction becomes insufficient, and there is a tendency that the uniform first coating layer 6 cannot be formed. On the other hand, if the treatment time is too long, the first coating layer 6 tends to be too thick.

  Next, the magnet body 4 coated with the first coating layer 6 is washed with pure water, and the moisture on the surface of the first coating layer is dried at a temperature of about 80 to 150 ° C. For simplification of the process, it may be immersed in alcohol and air dried.

  Next, preferably, the magnet member 2 is heat-treated. Preferably, the magnet member 2 is heat-treated at an ambient temperature of 100 to 450 ° C.

  By heat-treating the magnet member 2, the hardness (scratch resistance) of the Ni-Mo alloy (first coating layer 6) can be improved. As a result, the scratch resistance of the magnet member 2 can also be improved. In addition, by heat-treating the magnet member 2 at the above atmospheric temperature, the hardness (scratch resistance) of the Ni—Mo alloy (first covering layer 6) without deteriorating the coercive force of the magnet body 4 (rare earth magnet). ) Can be improved.

  For example, when the Mo content in the first coating layer 6 is 20 atomic% with respect to the entire first coating layer, the Vickers hardness (hereinafter referred to as Hv) of the first coating layer 6 before the heat treatment is 450. It is. However, when the magnet member 2 is heat-treated at an ambient temperature of 100 ° C. for 1 hour, the hardness can be improved to Hv = 550. Further, in the heat treatment at 200 ° C., Hv = 650, in the heat treatment at 300 ° C., Hv = 750, and in the heat treatment at 400 ° C., the hardness (scratch resistance) of the first coating layer 6 is improved up to Hv = 800. be able to. When the magnetic member 2 is heat-treated at 450 ° C. or higher, the coercive force of the magnet body 4 (rare earth magnet) decreases. In order to avoid this decrease in coercive force, heat treatment is preferably performed at 450 ° C. or lower.

    Through the above steps, the magnet member 2 shown in FIG. 1 is obtained.

  In the present embodiment, as described above, by covering the magnet element body 4 with the nonmagnetic first covering layer 6, it is possible to prevent the first covering layer 6 from shielding the magnetism of the magnet element body 4. Therefore, the magnetic characteristics (magnetic flux) of the magnet member 2 can be improved. Further, by covering the magnet element body 4 with the first covering layer 6, the magnet member 6 can be provided with corrosion resistance and scratch resistance. In particular, when the magnet member 2 is downsized (for example, the thickness in the magnetization direction is 1.5 mm or less), the operational effects according to the present invention become significant.

Second Embodiment In the second embodiment, as shown in FIG. 2, the magnet member 2 includes a magnet element body 4, a first covering layer 6, and a second covering layer 8. The second covering layer 8 covers the surface of the magnet body 4. The first coating layer 6 covers the surface of the second coating layer 8. In addition, the 2nd coating layer 8 may be comprised from several layers. Since the magnet body 4 and the first covering layer 6 in the second embodiment are the same as those in the first embodiment, their descriptions are omitted. Below, the 2nd coating layer 8 is mainly demonstrated.

  The second coating layer 8 contains Cu and is nonmagnetic. The second coating layer 8 may be composed of Cu alone. Since the magnet body 4 is covered with the non-magnetic second coating layer 8, the magnetism of the magnet body 4 is not shielded by the second coating layer 8. Moreover, the magnet member 6 can be made to function as a permanent magnet by covering the magnet element body 4 with the second covering layer 6. As a result, the magnetic characteristics can be improved.

A neodymium magnet, which is a kind of magnet body 4 (rare earth magnet), is composed of a main phase mainly composed of Nd ₂ Fe ₁₄ B, a rare earth rich phase rich in Nd, and a boron rich phase rich in B. Is done. The rare earth-rich phase containing a large amount of Nd exists at the grain boundary of the main phase. When the second coating layer 8 is formed so as to be in contact with the rare earth magnet, the main phase is completely covered with the rare earth rich phase and the second coating layer 8. As a result, the magnet member 6 and the magnet member 2 can function as permanent magnets. In this way, the magnetic flux of the magnet member 6 can be improved.

  If the main phase is in contact with a magnetic layer such as Ni, magnetic shielding is not performed even if the portion other than the contact portion is covered with the rare earth-rich phase, so that there is a possibility that the magnetic characteristics will not be sufficiently exhibited. Therefore, with the above-described configuration, the main phase can effectively exhibit the magnetic characteristics even at the interface between the main phase and the second coating layer 8.

  Moreover, since the 2nd coating layer 8 containing Cu is soft, when the magnet member 2 falls, it functions as a cushion (impact buffer material) which can endure the impact. As a result, the scratch resistance of the magnet member 6 can be improved.

  Furthermore, by forming the first coating layer 6 via the second coating layer 8, the adhesion between the magnet body 4 and the second coating layer 8 and the first coating layer 6 can be improved.

  Although the thickness T2 of the 2nd coating layer 8 is not specifically limited, Although it does not specifically limit, Preferably, it is 3-30 micrometers, More preferably, it is 5-10 micrometers. If the thickness T2 is too thin, there is a risk that pinholes resulting from irregularities on the surface of the magnet body 4 (rare earth magnet) are formed. When thickness T2 is too thick, the dimension of the magnet member 2 will become large. That is, in the magnet member 2, the volume ratio of the non-magnetic second coating layer 8 is increased. As a result, the magnetic properties per volume of the magnet member 6 may be deteriorated. Therefore, these problems can be prevented by setting the thickness T2 of the second coating layer 8 within the above range.

Formation method of the 2nd coating layer 8 The formation method of the 2nd coating layer 8 is the same as that of the case of the 1st coating layer 6 demonstrated in 1st Embodiment. Therefore, the description overlapping with the first embodiment will be omitted below.

  First, the magnetic element body 4 is formed by the same method as in the first embodiment. Next, the second coating layer 8 is formed on the surface of the magnet body 4 by wet plating or the like.

  In the present embodiment, the second coating layer 8 includes Cu. In order to contain Cu in the second coating layer 8, a metal salt compound of Cu may be contained in the plating bath. The metal salt compound of copper is not particularly limited, and examples thereof include copper sulfate, copper nitrate, basic copper sulfate, copper carbonate, copper pyrophosphate, cuprous oxide, cupric oxide, copper chloride, copper bromide and the like. It is done.

  Next, the first coating layer 6 is formed on the surface of the second coating layer 8 by wet plating or the like.

  Next, preferably, the magnet member 2 is heat-treated. Preferably, the magnet member 2 is heat-treated at an ambient temperature of 100 to 450 ° C. By heat-treating the magnet member 2, the hardness (scratch resistance) of the Ni-Mo alloy (first coating layer 6) can be improved. As a result, the scratch resistance of the magnet member 2 can also be improved. In addition, by heat-treating the magnet member 2 at the above atmospheric temperature, the hardness (scratch resistance) of the Ni—Mo alloy (first covering layer 6) without deteriorating the coercive force of the magnet body 4 (rare earth magnet). ) Can be improved.

  The magnet member 2 shown in FIG. 2 is obtained through the above steps.

  In the present embodiment, the magnet body 4 is covered with the nonmagnetic second coating layer 8 as described above. As a result, the magnetism of the magnet body 4 is not shielded by the second coating layer 8, and the function of the magnet member 6 as a permanent magnet can be improved. Therefore, the magnetic characteristics of the magnet member 2 can be improved.

  Moreover, since the 2nd coating layer 8 containing Cu is soft, when the magnet member 2 falls, it functions as a cushion (impact buffer material) which can endure the impact. As a result, the scratch resistance of the magnet member 6 can be improved.

  Furthermore, by forming the first coating layer 6 via the second coating layer 8, the adhesion between the magnet body 4 and the second coating layer 8 and the first coating layer 6 can be improved.

  Moreover, the corrosion resistance of the magnet member 6 can be improved by covering the magnet element body 4 with the first covering layer 6 and the second covering layer 8.

  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, the first coating layer 6 and / or the second coating layer 8 may be formed by a method using a gas phase reaction such as vacuum deposition, ion sputtering, or ion plating. Also in this case, the same effect as the above-described embodiment can be obtained.

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

Examples 1, 5, 6
In Examples 1, 5, and 6, the first coating layer was formed on the surface of the magnet body by electrolytic plating or electroless plating.

  First, a sintered body having a composition of 14Nd-1Dy-7B-78Fe (numbers are atomic ratio) prepared by powder metallurgy is heat-treated at 600 ° C. for 2 hours in an Ar atmosphere to be processed into a predetermined size. Thus, a magnet body was obtained. In each of the following examples and comparative examples, a magnet body was produced using magnet bodies having the same composition and the same dimensions.

  Next, this magnet body was washed with an alkaline degreasing solution, then the surface was activated with a 3% nitric acid solution, and washed thoroughly with pure water. Then, the surface of the magnet body is subjected to an electrolytic plating process using a parallel rotating barrel or an electroless plating process using a plating bath having the composition shown in Table 1, and a plating film (first film) is formed on the surface of the magnet body. (Coating layer) was formed to obtain a magnet member. Each plating bath was appropriately adjusted using potassium hydroxide (KOH) so that the pH became the value shown in Table 1. The plating conditions (current density and plating bath temperature) during the plating treatment were as shown in Table 1. The thickness T1 of the obtained plating film (first coating layer) was 7 μm in all examples.

  Next, for each of the obtained magnet members, measurement of magnetic flux (unit: mWb · T, milliweber turn) and evaluation of corrosion resistance (constant temperature and humidity test) were performed.

  The magnetic flux was measured using a flux meter after the obtained magnet member was magnetized to a saturated state and then left at room temperature (25 ° C.) for 30 minutes or longer. The larger the magnetic flux of the magnet member, the better the magnetic properties.

  In addition, the evaluation of the corrosion resistance (constant temperature and humidity test) is based on the conditions of 121 ° C., 2 atm, 100% RH, 48 hours. C. T. T. et al. The test (pressure cooker test) was performed. In this embodiment, P.I. C. T. T. et al. As a result of the test, a sample in which rust was not generated was determined as “pass”, while a sample in which even rust was generated was determined as “fail”.

  Table 2 shows the composition, residual magnetic flux density (Br), and Vickers hardness Hv of the obtained plating film (first coating layer) obtained in Examples 1, 5, and 6. Table 2 shows the magnetic flux of the obtained magnet member and the results of the constant temperature and humidity test. In addition, the unit of the composition ratio of the plating film shown in the following tables is atomic%.

Example 2
In Example 2, the magnet element was coated with the first coating layer according to the plating bath and plating conditions having the composition shown in Table 1 to form a magnet member. Next, this magnet member was heat-treated at 200 ° C. for 1 hour. Thus, the magnet member of Example 2 was formed.

Example 3
In Example 3, the first coating layer was formed on the surface of the magnet body by sputtering.

First, in the high frequency magnetron sputtering apparatus, the inside of the container was adjusted under the following conditions.
Argon pressure: 1 Pa,
High frequency power: 300W,
The temperature of the base material (magnet body) is 550 ° C.,
The distance between the substrate and the target, 200 mm.

  Next, a pure nickel target and a pure molybdenum target were placed on a holding table. Next, the magnet body was fixed to the turntable. Next, the turntable was rotated 180 ° (film formation time 30 minutes) under a passing condition in which the magnet body was stopped on the pure nickel target for 4 seconds and on the pure molybdenum target for 6 seconds. In this way, a sputtered film (first coating layer) was obtained. The composition of the obtained sputtered film was examined by ICP analysis. Thus, the magnet member of Example 3 was formed.

Example 4
In Example 4, as shown below, the first coating layer was formed on the surface of the magnet body by vacuum deposition.

First, a rare earth magnet was placed on a holder in a vacuum chamber having a vapor deposition function. Next, the inside of this chamber was evacuated to 6.7 × 10 ⁻⁴ Pa (5 × 10 ⁻⁶ Torr). Next, Ar ions were irradiated from the ion source to the mirror surface of the pure iron plate for 5 minutes under the condition of an acceleration voltage of 5 kV to perform pretreatment for surface cleaning. Next, the first covering layer was formed on the surface of the magnet body by evaporating Ni and Mo metal on the magnet body by a triple hearth electron beam evaporation method. Thus, the magnet member of Example 4 was formed.

Comparative Examples 1 and 2
In Comparative Examples 1 and 2, a plating film (first coating layer) composed of Ni alone was formed on the surface of the magnet body by electrolytic plating. Table 1 shows the compositions and plating conditions of the plating baths used in Comparative Examples 1 and 2. Otherwise, the magnet member of Comparative Example 1 was formed under the same conditions as in Example 1.

  Table 2 shows the composition, residual magnetic flux density (Br), and Vickers hardness Hv of the first coating layers obtained in Examples 2, 3, and 4 and Comparative Examples 1 and 2. Table 2 shows the magnetic flux of the obtained magnet member and the results of the constant temperature and humidity test.

Evaluation 1
As shown in Table 2, in each of the magnet members of Examples 1 to 4, the magnet body was coated with the first coating layer made of a nonmagnetic Ni—Mo alloy (amorphous). In the magnet member of Example 5, the magnet body was covered with a first coating layer made of a nonmagnetic Ni—Mo—P alloy (amorphous). In each magnet member of Example 6, the magnet body was coated with a first coating layer made of nonmagnetic Ni—Mo—W (amorphous). On the other hand, in each of the magnet members of Comparative Examples 1 and 2, the magnet body was covered with the first coating layer made of Ni having magnetism alone.

  In Examples 1 to 6, the magnetic flux was 0.30 mWb · T, which was larger than Comparative Examples 1 and 2. On the other hand, in the magnet members of Comparative Examples 1 and 2, the respective magnetic fluxes were 0.25 mWb · T and 0.26 mWb · T. That is, in Examples 1-6, it was confirmed that the magnetic characteristics of the magnet member are superior to those of Comparative Examples 1 and 2.

  Moreover, in Examples 1-6, it was confirmed that the Vickers hardness of a 1st coating layer is high compared with the comparative examples 1 and 2, ie, the flaw resistance of a magnet member is excellent. In particular, in Example 2 in which the heat treatment was performed on the magnet member, it was confirmed that the Vickers hardness of the first coating layer was higher than that in Example 1 having the first coating layer having the same composition. That is, it was confirmed that the hardness of the first coating layer was improved by the heat treatment on the magnet member.

  Furthermore, in Examples 1-6, it was confirmed that a magnet member has the outstanding corrosion resistance. On the other hand, in Comparative Example 1, a magnet member having corrosion resistance was not obtained.

Example 7
In Example 7, first, the second coating layer was formed on the surface of the magnet body by electrolytic plating. Next, the first coating layer was formed on the surface of the second coating layer by electrolytic plating. Moreover, the thickness T1 of the obtained 1st coating layer and the thickness T2 of the 2nd coating layer were 7 micrometers, respectively. Table 3 shows the composition and plating conditions of the plating bath used in Example 7.

  Table 3 shows each composition, each residual magnetic flux density (Br), and Vickers hardness Hv of the first coating layer and the second coating layer obtained in Example 7. Table 3 shows the magnetic flux of the obtained magnet member and the results of the constant temperature and humidity test.

Evaluation 2
The magnet member of Example 7 has a first coating layer made of a nonmagnetic Ni—Mo alloy (amorphous) and a second coating layer made of nonmagnetic Cu. In the magnet member of Example 7, the magnetic flux was larger than those of Comparative Examples 1 and 2 (Table 2). From these results, it was confirmed in Examples 1-7 that the magnetic properties of the magnet member were superior to those of Comparative Examples 1 and 2. In Example 7, the total thickness of the first and second coating layers (total plating thickness) was 14 μm, although the total plating thickness was the largest in all Examples and all comparisons. It was confirmed that the magnetic flux was the largest (excellent in magnetic properties).

  In Example 7, it was confirmed that the Vickers hardness of the first coating layer was higher than that of Comparative Examples 1 and 2, that is, excellent scratch resistance.

  Furthermore, in Example 7, compared with the comparative example 1, it was confirmed that the corrosion resistance of a magnet member is excellent.

FIG. 1 is a schematic cross-sectional view of a magnet member according to the first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a magnet member according to the second embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Magnet member 4 ... Magnet base body 6 ... 1st coating layer 8 ... 2nd coating layer

Claims (11)

A magnet body;
A first coating layer,
The first coating layer covers the magnet body;
The magnet member, wherein the first coating layer contains Ni and Mo. The magnet member according to claim 1, wherein the first coating layer is nonmagnetic. The magnet member according to claim 1, wherein the magnet body is a rare earth magnet. The magnet member according to any one of claims 1 to 3, wherein the first coating layer contains at least one element of Sn, W, Cu, Ti, Zn, P, and B. 5. The magnet member according to claim 1, wherein the Mo content in the first coating layer is 20 to 80 atomic% with respect to the entire first coating layer. The magnet member according to any one of claims 1 to 5, wherein the first covering layer is composed of a columnar structure that is long in a direction perpendicular to the magnet body. The magnet member according to claim 1, wherein the first covering layer has a Vickers hardness of 400 or more. The magnet body;
The first coating layer;
A second coating layer,
The second coating layer covers the magnet body;
The first coating layer covers the magnet body coated on the second coating layer;
The magnet member according to claim 1, wherein the second covering layer contains Cu and is nonmagnetic. A method for producing the magnet member according to claim 1,
Forming the magnet body; and
A step of coating the magnet body with the first coating layer to form a magnet member;
And a step of heat-treating the magnet member. A method for manufacturing the magnet member according to claim 8,
Forming the magnet body; and
Coating the magnet body with the second coating layer;
Forming the magnet member by covering the magnet body covered with the second covering layer with the first covering layer;
And a step of heat-treating the magnet member. The method for producing a magnet member according to claim 9 or 10, wherein the magnet member is heat-treated at an ambient temperature of 100 to 450 ° C.

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