JP2006077271A - Plating method and plating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plating method that prevents the reprecipitation of a component having eluted into a plating liquid from a rare-earth sintered magnet of an article to be plated, and inhibits the degradation of the adhesiveness and reliability of a plated film, and to provide a plating apparatus. <P>SOLUTION: When plating a R-T-B base sintered magnet, this plating method includes supplying an oxidative gas to the plating liquid L to be used, to oxidize and precipitate the component, for instance Nd and Fe, in the R-T-B base sintered magnet, which has eluted into the plating liquid L during plating. In the above step, it is preferable to supply the oxidative gas in a bubble form into the plating liquid L, so as to enhance the contact efficiency of the gas with the eluted component in the plating liquid L. The plating apparatus preferably has a filter 16 so as to collect a precipitated oxide of the eluted component. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a plating method and a plating apparatus suitable for use in plating on the surface of, for example, a rare earth sintered magnet typified by an Nd—Fe—B system.

For example, rare earth sintered magnets represented by the Nd-Fe-B series are easily oxidized, and thus the surface of the magnet body needs to be protected by metal plating or resin coating (for example, Patent Document 1). 2).
For example, metal plating includes electrolytic plating and electroless plating, and electrolytic plating is often used for rare earth sintered magnets. Such plating types include Ni plating, Cu plating, Sn plating, and the like.
Since such plating is for protecting the magnet body, the plating film is required to have high corrosion resistance and uniformity without greatly degrading the magnetic properties of the magnet.

JP 49-86896 A JP-A-60-63901

By the way, even if the above-described Nd—Fe—B rare earth sintered magnet is plated, unexpectedly in the test for confirming the adhesion of the plating film and the salt spray test for confirming the rust prevention property. In some cases, the results were low. In other words, since this leads to a decrease in the reliability of the plating film, the present inventors have investigated the cause.
As a result, it was discovered that Nd and Fe, which are components contained in the magnet body, are eluted in the plating solution when plating the Nd—Fe—B rare earth sintered magnet and the like as described above. The components eluted in the plating solution (hereinafter referred to as elution components) reprecipitates on the magnet body as the plating progresses, which reduces the adhesion and reliability of the plating film, particularly in the salt spray test. It was causing.
The present invention has been made on the basis of such a technical problem, and prevents reprecipitation of components eluted from a rare earth sintered magnet or the like, which is an object to be plated, into the plating solution, and provides adhesion and reliability of the plating film. An object of the present invention is to provide a plating method and a plating apparatus that can suppress a decrease in the thickness.

For this purpose, the present invention introduces an oxidizing gas into the plating solution, oxidizes the components eluted from the magnet body into the plating solution, and prevents reprecipitation on the surface of the magnet body.
That is, the plating method of the present invention includes a plating step of immersing a plating object in a plating solution in a plating tank and plating the plating object, supplying an oxidizing gas into the plating solution, And an elution component oxidation step of oxidizing the eluted component of the plating object. By oxidizing the components of the plating target eluted in the plating solution in the elution component oxidation step, it is possible to prevent the components from re-depositing on the plating target in the plating step.
In the elution component oxidation step, it is preferable to supply the oxidizing gas in the form of bubbles to the lower part of the plating tank. As a result, the bubbles float up in the plating solution, and in the process, come into contact with the components of the plating object eluted in the plating solution with high contact efficiency.
It is preferable to collect the oxide produced by oxidizing the components of the plating object in the elution component oxidation step from the plating solution. For this, a filter or the like can be used as appropriate.
In addition, a plating process and an elution component oxidation process may be performed in parallel, and may be performed separately. Further, the elution component oxidation step may be performed by introducing the plating solution into a bath different from the plating bath in which the plating step is performed.
Such a plating method is effective for any plating object as long as the plating components eluted in the plating solution adversely affect the plating object, but R-T-B (R Is effective when one or more of rare earth elements are used, and T is at least one or more transition metal elements essential to Fe or Fe and Co). In particular, when plating an Nd—Fe—B based sintered magnet, oxidizable Nd and Fe are eluted in the plating solution. By oxidizing this Nd or Fe in the plating solution, reprecipitation of these elements on the magnet surface can be effectively suppressed.

  By the way, in the elution component oxidation step, it is preferable to use an oxidizing gas having an oxygen concentration of 3 vol% or higher, and it is preferable to use an oxidizing gas having an oxygen concentration of 15 vol% or higher. In terms of cost and ease of management, it is particularly preferable to use air (atmosphere) as the oxidizing gas.

As an apparatus for carrying out the above plating method, the present invention includes a plating tank that contains a plating solution for plating an object to be plated, and a component in the plating object that has eluted in the plating solution. A plating comprising: an oxidizing gas supply unit that supplies an oxidizing gas to the substrate; and an oxide recovery unit that recovers an oxide generated by oxidizing a component of the plating object with the oxidizing gas. Providing equipment.
In such a plating apparatus, the oxidizing gas supply unit can supply an oxidizing gas into the plating solution in the plating tank, or in the plating solution drawn from the plating tank to another external tank, etc. An oxidizing gas may be supplied.

As another apparatus for carrying out the above plating method, the present invention provides a first tank containing a plating solution for plating an object to be plated, and a first tank that communicates with the first tank. A second tank in which the plating solution can be circulated, a gas supply unit for supplying an oxidizing gas into the plating solution introduced from the first tank into the second tank, and a second tank from the second tank. There is provided a plating apparatus comprising: a filtration unit that filters a plating solution supplied with an oxidizing gas and fed to one tank. In the gas supply unit, the components of the plating object eluted in the plating solution in the first tank are oxidized, so that the oxidizing gas can be supplied into the plating solution introduced into the second tank.
Such a plating apparatus is particularly effective when an R-T-B sintered magnet is used as an object to be plated.

  ADVANTAGE OF THE INVENTION According to this invention, the reprecipitation of the component eluted to the plating solution from the plating target object can be prevented, and the fall of the adhesiveness and reliability of a plating film can be suppressed.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
First, a rare earth sintered magnet to which the present invention is applied will be described.
The present invention is particularly preferably applied to an RTB-based sintered magnet, but the present invention can also be applied to other rare earth sintered magnets. Hereinafter, a case where the present invention is applied to an RTB-based sintered magnet will be described as an example.
The RTB-based sintered magnet contains 25 to 37 wt% of rare earth element (R). Here, R in the present invention has a concept including Y, and therefore 1 of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. It is selected from species or two or more species. If the amount of R is less than 25 wt%, the R ₂ T ₁₄ B phase, which is the main phase of the R-T-B system sintered magnet, is not sufficiently generated, and α-Fe having soft magnetism is precipitated and retained. The magnetic force is significantly reduced. On the other hand, when R exceeds 37 wt%, the volume ratio of the R ₂ T ₁₄ B phase, which is the main phase, decreases, and the residual magnetic flux density decreases. Further, R reacts with oxygen, the amount of oxygen contained increases, and accordingly, the R-rich phase effective for the generation of coercive force decreases, leading to a decrease in coercive force. Therefore, the amount of R is set to 25 to 37 wt%. A desirable amount of R is 28 to 35 wt%, and a more desirable amount of R is 29 to 33 wt%.

Further, the RTB-based sintered magnet to which the present invention is applied contains 0.5 to 4.5 wt% of boron (B). When B is less than 0.5 wt%, a high coercive force cannot be obtained. On the other hand, when B exceeds 4.5 wt%, the residual magnetic flux density tends to decrease. Therefore, the upper limit of B is set to 4.5 wt%. A desirable amount of B is 0.5 to 1.5 wt%, and a more desirable amount of B is 0.8 to 1.2 wt%.
The RTB-based sintered magnet to which the present invention is applied has a Co content of 2.0 wt% or less (not including 0), preferably 0.1 to 1.0 wt%, more preferably 0.3 to 0. .7 wt% can be contained. Co forms the same phase as Fe, but is effective in improving the Curie temperature and improving the corrosion resistance of the grain boundary phase.

  In addition, the RTB-based sintered magnet to which the present invention is applied includes elements such as Al, Cu, Zr, Ti, Bi, Sn, Ga, Nb, Ta, Si, V, Ag, and Ge. It can be contained as appropriate. On the other hand, it is desirable to reduce impurity elements such as oxygen, nitrogen, and carbon as much as possible. In particular, the amount of oxygen that impairs magnetic properties is preferably 5000 ppm or less, more preferably 3000 ppm or less. This is because when the amount of oxygen is large, the rare-earth oxide phase, which is a nonmagnetic component, increases and the magnetic properties are deteriorated.

Next, the manufacturing method of the RTB system sintered magnet to which this invention is applied is demonstrated.
The RTB-based sintered magnet to which the present invention is applied can be manufactured as follows.
The raw material alloy can be produced by a strip casting method or other known melting methods in a vacuum or an inert gas, preferably in an Ar atmosphere. In the strip casting method, a molten metal obtained by melting a raw metal in a non-oxidizing atmosphere such as an Ar gas atmosphere is ejected onto the surface of a rotating roll. The melt rapidly cooled by the roll is rapidly solidified in the form of a thin plate or flakes (scales). This rapidly solidified alloy has a homogeneous structure with a crystal grain size of 1 to 50 μm. The raw material alloy can be obtained not only by the strip casting method but also by a melting method such as high frequency induction melting. In order to prevent segregation after dissolution, for example, it can be solidified by pouring into a water-cooled copper plate. An alloy obtained by the reduction diffusion method can also be used as a raw material alloy.
When obtaining an RTB-based sintered magnet, a so-called alloy using a R ₂ T ₁₄ B crystal grain (low R alloy) and an alloy containing more R than a low R alloy (high R alloy) is used. A mixing method can also be applied to the present invention.

  The raw material alloy is subjected to a grinding process. In the case of the mixing method, the low R alloy and the high R alloy are pulverized separately or together. The pulverization process includes a coarse pulverization process and a fine pulverization process. First, the raw material alloy is coarsely pulverized until the particle size becomes about several hundred μm. The coarse pulverization is desirably performed in an inert gas atmosphere using a stamp mill, a jaw crusher, a brown mill or the like. Prior to coarse pulverization, it is effective to perform pulverization by allowing hydrogen to be absorbed in the raw material alloy and then released. This hydrogen release treatment is performed for the purpose of reducing hydrogen as an impurity as a rare earth sintered magnet. The heating and holding temperature for storing hydrogen is 200 ° C. or higher, preferably 350 ° C. or higher. The holding time varies depending on the relationship with the holding temperature, the thickness of the raw material alloy, etc., but is at least 30 minutes or longer, preferably 1 hour or longer. The hydrogen release treatment is performed in a vacuum or Ar gas flow. The hydrogen storage process and the hydrogen release process are not essential processes. This hydrogen pulverization can be regarded as coarse pulverization, and mechanical coarse pulverization can be omitted.

  After the coarse pulverization process, the process proceeds to the fine pulverization process. A jet mill is mainly used for fine pulverization, and a coarsely pulverized powder having a particle size of about several hundreds of μm has an average particle size of 2.5 to 6 μm, preferably 3 to 5 μm. The jet mill releases a high-pressure inert gas from a narrow nozzle to generate a high-speed gas flow, accelerates the coarsely pulverized powder with this high-speed gas flow, collides with the coarsely pulverized powder, and collides with the target or container wall. It is a method of generating a collision and crushing.

  In the case of the mixing method, the timing of mixing the two kinds of alloys is not limited. However, when the low R alloy and the high R alloy are separately pulverized in the pulverization step, the pulverized low R alloy powder is used. And high R alloy powder in a nitrogen atmosphere. The mixing ratio of the low R alloy powder and the high R alloy powder may be about 80:20 to 97: 3 by weight. The mixing ratio when the low R alloy and the high R alloy are pulverized together is the same. Fatty acids or fatty acid derivatives and hydrocarbons for the purpose of improving lubrication and orientation during molding, such as zinc stearate, calcium stearate, aluminum stearate, stearamide, olein, which are stearic acid and oleic acid Acid amide, ethylenebisisostearic acid amide, hydrocarbon paraffin, naphthalene and the like can be added in an amount of about 0.01 to 0.3 wt% during pulverization.

The finely pulverized powder obtained above is subjected to, for example, molding in a magnetic field.
The molding pressure in the magnetic field molding may be in the range of 0.3 to 3 ton / cm ² (30 to 300 MPa). The molding pressure may be constant from the beginning to the end of molding, may be gradually increased or gradually decreased, or may vary irregularly. The lower the molding pressure is, the better the orientation is. However, if the molding pressure is too low, the strength of the molded body is insufficient and handling problems occur. Therefore, the molding pressure is selected from the above range in consideration of this point. The final relative density of the molded body obtained by molding in a magnetic field is usually 50 to 60%.
The applied magnetic field may be about 12 to 20 kOe (960 to 1600 kA / m). The applied magnetic field is not limited to a static magnetic field, and may be a pulsed magnetic field. A static magnetic field and a pulsed magnetic field can also be used in combination.

Next, the compact is sintered in a vacuum or an inert gas atmosphere. Although it is necessary to adjust sintering temperature by various conditions, such as a composition, a grinding | pulverization method, the difference of an average particle diameter, and a particle size distribution, what is necessary is just to sinter at 1000-1200 degreeC for about 1 to 10 hours.
After sintering, the obtained sintered body can be subjected to an aging treatment. This step is an important step for controlling the coercive force. In the case where the aging treatment is performed in two stages, it is effective to hold for a predetermined time in the vicinity of 800 ° C. and 600 ° C. When the heat treatment in the vicinity of 800 ° C. is performed after sintering, the coercive force increases, which is particularly effective in the mixing method. In addition, since the coercive force is greatly increased by heat treatment at around 600 ° C., when the aging treatment is performed in one stage, the aging treatment at around 600 ° C. is preferably performed.

The RTB-based sintered magnet thus obtained is processed into a predetermined shape by a NC (Numerical Control) controlled processing machine or the like.
Thereafter, the RTB-based sintered magnet is used as an object to be plated, and the present invention is applied for plating.
Here, the RTB-based sintered magnet that is plated by applying the present invention is not limited to the above-described manufacturing method, and may be manufactured by another manufacturing method.

The RTB-based sintered magnet is subjected to barrel polishing, degreasing treatment, acid treatment, alkaline ultrasonic cleaning, and the like as pretreatment for plating. Here, the types and order of preprocessing are not limited to those described above.
The pretreated R-T-B system sintered magnet is immersed in a plating tank and plated.
Here, Ni plating, Cu plating, Sn plating, or the like can be used for plating, and the plating tank is filled with a plating solution corresponding to the type of plating used. As the plating method, electrolytic plating or electroless plating can be used.

Now, when plating the RTB-based sintered magnet in this way, it is preferable to supply an oxidizing gas into the plating solution to be used. This is for oxidizing and precipitating the components of the RTB-based sintered magnet that are eluted in the plating solution during plating.
For example, when electro Ni plating is applied to a Nd—Fe—B based sintered magnet in a watt bath, Nd and Fe are eluted in the plating solution.
For this purpose, it is preferable to supply an oxidizing gas to the bubbles in the plating solution to increase the contact efficiency with the eluted components in the plating solution. For this reason, it is preferable that a pipe having a large number of holes is provided at the bottom of the plating tank, an oxidizing gas is fed into the pipe, and the oxidizing gas is discharged from the holes into the plating solution. The oxidizing gas released from the hole into the plating solution becomes bubbles and rises in the plating solution, and in the process, comes into contact with the eluted components in the plating solution. The elution component that has come into contact with the oxidizing gas is oxidized to become an oxide of neodymium or iron and is precipitated in the plating solution.
In order to collect the precipitated oxide of the eluted component, the plating tank is preferably provided with oxide collecting means such as a filter.

Thus, the elution component eluted in the plating solution in the process of plating the R-T-B system sintered magnet in the plating tank is oxidized and precipitated by contact with the oxidizing gas. Reprecipitation on the surface of the RTB-based sintered magnet can be prevented. As a result, it is possible to avoid a decrease in the adhesion and reliability of the plating film.
In addition, according to such a method, even in an existing plating apparatus, it can be realized only by additionally installing a pipe, a pump, and the like for releasing an oxidizing gas, which is very effective.

Now, as the oxidizing gas, any gas may be used as long as it contains oxygen. Of course, only oxygen may be supplied, but considering the cost and the like, it is preferable to use air (atmosphere).
Moreover, it is preferable that the oxygen concentration in the oxidizing gas is capable of quickly oxidizing the components eluted into the plating solution, but it is possible to avoid oxidation of the RTB-based sintered magnet itself during the plating process. Is preferable.
For example, the composition 26.5 wt% Nd-5.9 wt% Dy-0.25 wt% Al-0.5 wt% Co-0.07 wt% Cu-1.0 wt% B-Fe. When electric Ni plating is applied to a bal RTB-based sintered magnet in a watt bath, an oxidizing gas having an oxygen concentration of 3 vol% or more, more preferably 15 vol% or more, and even more preferably 20 to 30 vol% is used. is there. This is because when the oxidizing gas is supplied into the plating tank for plating, the RTB-based sintered magnet may be oxidized by the oxidizing gas if the concentration of the oxidizing gas is too high. Further, the flow rate of the oxidizing gas to be supplied varies depending on the type of the plating bath and the size of the plating tank, and thus cannot be defined unconditionally, but it is preferably discharged into the plating solution at 5 to 50 L (liter) / min.

By the way, in the above, the oxidizing gas is released into the plating tank for plating the R-T-B system sintered magnet, but the oxide of the eluted component precipitated in the plating solution is released. It is also conceivable that the inside of the plating tank is floated by the bubbles of the property gas, which may be an impediment to good plating treatment.
In this case, like the plating apparatus 10 shown in FIG. 1, a plating tank (first tank) 11 that performs plating of the RTB-based sintered magnet and a processing tank that performs the removal process of the eluted components (separately) The tank and the second tank) 12 are preferably provided separately. For this, the plating tank 11 and the processing tank 12 are connected via the delivery side pipe 13 and the return side pipe 14 so that the plating solution L can be circulated between the plating tank 11 and the processing tank 12. . The processing tank 12 is provided with a pipe (oxidizing gas supply unit, gas supply unit) 15 having a plurality of holes 15a formed at the bottom, and the oxidizing gas is supplied to the pipe 15 via a pump (not shown). Is supposed to be sent. As a result, the oxidizing gas is released in the form of bubbles into the plating solution L of the treatment tank 12 from the hole 15 a of the pipe 15. When the oxidizing gas released from the hole 15a into the plating solution L comes into contact with the elution component in the plating solution L, the elution component becomes an oxide and precipitates in the plating solution L. Is recovered at an appropriate place in the circulation process of the plating solution L between the plating tank 11 and the processing tank 12, for example, a filter (oxide recovery section, filtration section) 16 provided in the return side pipe 14. It has become so.

  In the plating apparatus 10, the elution component eluted in the plating solution L in the process of plating the RTB-based sintered magnet in the plating tank 11 is sent to the processing tank 12 together with the plating solution L in this way. Oxidized by contact with an oxidizing gas and recovered by the filter 16. Thereby, the elution component in the plating solution L in the plating tank 11 can be reduced, and the effect of preventing reprecipitation of the elution component on the surface of the RTB-based sintered magnet can be further ensured. it can.

The present invention can be applied to the case where the RTB-based sintered magnet is subjected to the same type of plating a plurality of times or when a plurality of types of plating are sequentially performed. When performing multiple types of plating, the above-described configuration may be applied to the plating tank for performing each type of plating, and only for the plating tank from which particularly harmful components are eluted, The configuration as described above may be applied.
In addition to this, as long as it does not depart from the gist of the present invention, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

Here, since the effect by oxidizing the elution component to a plating solution using oxidizing gas was confirmed, the result is shown.
First, the RTB system sintered magnet used as plating object was manufactured as follows.
26.5 wt% Nd-5.9 wt% Dy-0.25 wt% Al-0.5 wt% Co-0.07 wt% Cu-1.0 wt% B-Fe. A raw material alloy having a composition of bal was prepared.
Next, after hydrogen was occluded in the raw material alloy at room temperature, hydrogen pulverization treatment was performed in which dehydrogenation was performed at 600 ° C. for 1 hour in an Ar atmosphere.
The alloy that has been subjected to the hydrogen pulverization treatment was mixed with 0.05 to 0.1% of a lubricant that contributes to improvement of pulverization and orientation during molding. The lubricant may be mixed for about 5 to 30 minutes using, for example, a Nauter mixer. Thereafter, a finely pulverized powder having an average particle size of 5.0 μm was obtained using a jet mill.

  The finely pulverized powder was molded in a magnetic field, and the molded body thus obtained was heated to 1080 ° C. in vacuum and in an Ar atmosphere, and held for 4 hours for sintering. Next, the obtained sintered body was subjected to a two-stage aging treatment of 800 ° C. × 1 hour and 560 ° C. × 1 hour (both in an Ar atmosphere).

  After processing the RTB-based sintered magnet thus obtained into a flat plate shape having a length of 40 mm, a width of 30 mm, and a thickness of 5 mm, as a pretreatment for plating, barrel polishing, degreasing treatment, acid treatment, Alkaline ultrasonic cleaning was performed.

Thereafter, the RTB-based sintered magnet was immersed in a 60 L (liter) watt bath, and electro Ni plating was performed. At this time, the film formation rate was 3 (μm / hr), and when 5 hours passed after immersion, the RTB-based sintered magnet was pulled up from the plating solution, and Comparative Sample 1 was produced.
When a part of the plating solution after plating was collected and analyzed by ICP, elution of Nd and Fe was observed.

Moreover, air as an oxidizing gas is introduced into the plating solution at a flow rate of 20 (L / min) and released as bubbles, while the RTB-based sintered magnet is plated under the same plating conditions as in Comparative Sample 1. The sample 1 was produced.
At this time, fine precipitates were observed in the plating solution from which air bubbles were released. When this was recovered with a filter, it was found to be a particulate and gel-like substance having an ocher color. When this substance was analyzed by EPMA, it was confirmed that Nd, Fe, and O (oxygen) were contained.

After the plating treatment, the plating film formed on the surface of the RTB-based sintered magnet was evaluated for both Sample 1 and Comparative Sample 1. Evaluation items were plating film thickness, adhesion, and reliability. The plating film thickness was measured by fluorescent X-ray analysis.
The adhesion was evaluated by the following method. First, two cuts having a width of 10 mm, a depth of 30 to 40 μm, and a length of 20 to 30 mm are made in parallel on the surface of the magnet after plating. Further, a cut having the same depth was formed at one end of the two cuts so as to be substantially perpendicular to the two cuts, thereby forming a substantially U-shaped cut. Only the plating film was peeled off perpendicularly to the magnet plane from the tip portion of the cut (the cut portion formed almost perpendicular to the two cuts), and the peeling force at that time was measured.
The reliability was evaluated by spraying a salt water spray test by spraying a NaCl aqueous solution with a concentration of 5% at 35 ° C. for 24 hours, and visually observing peeling, spot rust, and swelling of the plated film.
The results are shown in Table 1.

  As shown in Table 1, the average plating film thickness was equal to 15 μm for both Sample 1 and Comparative Sample 1. Regarding the adhesion and reliability, the sample 1 from which the oxidizing gas was released was not found to be peeled off or spotted rust, whereas the comparative sample 1 from which the oxidizing gas was not released was satisfactory. It was. Thus, it can be seen that the adhesion and reliability are improved by releasing the oxidizing gas.

Next, in the case of performing two types of plating, the effect of oxidizing the eluted component into the plating solution using an oxidizing gas was confirmed, and the result is shown.
The RTB-based sintered magnet to be plated was manufactured and pretreated in the same manner as in Example 1.
Here, the shape of the RTB-based sintered magnet was a flat plate having a length of 40 mm, a width of 30 mm, and a thickness of 5 mm.

Thereafter, an RTB-based sintered magnet was immersed in 60 L (liter) of a bronze copper plating solution, and electro Cu plating was performed. At this time, the film formation rate was 4 (μm / hr), and the R-T-B system sintered magnet was pulled up from the plating solution when 2.5 hours had elapsed after immersion.
At this time, the plating solution is introduced into a treatment tank different from the plating tank for plating the R-T-B system sintered magnet, and air as an oxidizing gas is supplied to the treatment tank at a flow rate of 20 (L / min). The air bubbles were released into the plating solution.

Subsequently, an RTB-based sintered magnet was immersed in a 60 L (liter) watt bath, and electro Ni plating was performed. At this time, the film formation rate was 3 (μm / hr), and the RTB-based sintered magnet was pulled up from the plating solution when 1.7 hours passed after immersion.
At this time, the plating solution is introduced into a treatment tank different from the plating tank for plating the R-T-B system sintered magnet, and air as an oxidizing gas is supplied to the treatment tank at a flow rate of 20 (L / min). The air bubbles were released into the plating solution.

After the plating treatment, the plating film formed on the surface of the RTB-based sintered magnet was evaluated in the same manner as in Example 1.
The results are shown in Table 1.
As shown in Table 1, in Sample 2, the Cu plating film thickness was 10 μm, and the Ni plating film thickness was 5 μm. Regarding adhesion and reliability, neither peeling nor spot rust was observed as in Sample 1, and good results were obtained. Thereby, even in the case of two-layer plating, it can be seen that the adhesion and reliability are improved by releasing the oxidizing gas.

Next, since the effect when changing the oxidation concentration of oxidizing gas was confirmed, the result is shown.
The RTB-based sintered magnet to be plated was manufactured and pretreated in the same manner as in Example 1.

Thereafter, the RTB-based sintered magnet was immersed in a 60 L (liter) watt bath, and Ni plating was performed. At this time, the film formation rate was 3 (μm / hr), and the RTB-based sintered magnet was pulled up from the plating solution when 5 hours passed after immersion.
At this time, the plating solution is introduced into a treatment tank different from the plating tank for plating the RTB-based sintered magnet, and the oxidizing gas is introduced into the treatment tank at a flow rate of 20 (L / min). Then, bubbles were released into the plating solution. Here, in Sample 3, oxygen gas having an oxygen concentration of 99 vol% or more was used as the oxidizing gas. Further, as the sample 4, an oxidizing gas having an oxygen concentration of 3 vol% (the balance is nitrogen) was used.

After the plating treatment, the plating film formed on the surface of the RTB-based sintered magnet was evaluated in the same manner as in Example 1.
The results are shown in Table 1.
As shown in Table 1, the thickness of the plating film for both Samples 3 and 4 was 15 μm. With regard to adhesion and reliability, sample 3 using pure oxygen showed neither peeling nor spot rust, and good results were obtained, but the oxygen concentration was low (lower than air (atmosphere)). In the sample 4 using the oxidizing gas, light peeling and spot rust were observed, although not as much as the comparative sample 1 shown in Example 1.
As a result, if the oxygen concentration of the oxidizing gas is high, the adhesion and reliability are improved. However, when the oxygen concentration of the oxidizing gas is 3 vol% or less, the degree of suppressing the deterioration of the adhesion and reliability is slightly weakened. It was confirmed.

It is a figure which shows an example of the plating apparatus in this Embodiment, (a) is a sectional elevation, (b) is a top view.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Plating apparatus, 11 ... Plating tank (1st tank), 12 ... Processing tank (Another tank, 2nd tank), 15 ... Piping (oxidizing gas supply part, gas supply part), 15a ... Hole, 16 ... filter (oxide recovery part, filtration part), L ... plating solution

Claims (11)

A plating step of immersing a plating object in a plating solution in a plating tank and plating the plating object; and
An elution component oxidation step of supplying an oxidizing gas into the plating solution and oxidizing the components of the plating object eluted in the plating solution;
A plating method comprising:   The plating method according to claim 1, wherein in the elution component oxidation step, the oxidizing gas is supplied in a bubble state to a lower portion of the plating tank.   The plating method according to claim 1 or 2, wherein an oxide generated by oxidizing the component of the plating object in the elution component oxidation step is recovered from the plating solution.   The plating method according to any one of claims 1 to 3, wherein the elution component oxidation step is performed by introducing the plating solution into a bath different from the plating bath in which the plating step is performed.   The object to be plated is an R-T-B (R is one or more rare earth elements, T is at least one transition metal element in which Fe or Fe and Co are essential) based sintered magnets. The plating method according to any one of claims 1 to 4, wherein:   The elution component oxidation step is to prevent re-precipitation of the component on the plating object in the plating step by oxidizing the component of the plating object eluted in the plating solution. The plating method according to claim 1, wherein:   The plating method according to claim 1, wherein the oxidizing gas having an oxygen concentration of 3 vol% or more is used in the elution component oxidation step. A plating tank containing a plating solution for plating an object to be plated;
In order to oxidize the components of the plating object eluted in the plating solution, an oxidizing gas supply unit that supplies an oxidizing gas into the plating solution;
An oxide recovery part for recovering an oxide generated by oxidizing the component of the plating object with the oxidizing gas;
A plating apparatus comprising: A first tank containing a plating solution for plating a plating object;
A second tank that communicates with the first tank and allows the plating solution to circulate with the first tank;
A gas supply unit for supplying an oxidizing gas into the plating solution introduced from the first tank into the second tank;
A filtration section for filtering the plating solution supplied with the oxidizing gas, fed from the second tank to the first tank;
A plating apparatus comprising:   The gas supply unit supplies the oxidizing gas into the plating solution introduced into the second tank in order to oxidize the components of the plating object eluted in the plating solution in the first tank. The plating apparatus according to claim 9, wherein:   The object to be plated is an R-T-B (R is one or more rare earth elements, T is at least one transition metal element in which Fe or Fe and Co are essential) based sintered magnets. The plating apparatus according to any one of claims 8 to 10, wherein:

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