JPH09205013A - Bond magnet having rust-resistant coat layer and its rust-resistant coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase corrosion-resistant performance by a method wherein metal powders are firmly embedded in a clearance part among magnetic particles of a porous surface structure of a bond magnet and flattened to the same degree as a surface of a magnetic body, and the entire surface is coated with a thin resinous coat layer. SOLUTION: Particles 1 of magnetic powders of a bond magnet have a flat stacked structure with respect to each other along the face, and a plurality of clearance parts 2 exist inside a magnet body and on the face among these particles 1. Soft metal powders are projected into the clearance part 2 on the face of this magnet body. Alternatively, a impact is added by rotation, shaking, oscillation or stirring from outwardly, the metal powders are compressed while filling and coating, a compression body part 3 of metal powders for being filled with the clearance part 2 and the face of the magnet body is flattened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rust preventive technique for a porous bonded magnet in which magnet powders are bound with a binder, and a typical rare earth bonded magnet having various shapes such as a cylindrical shape, a disk shape, and a ring shape. The present invention relates to a bond magnet having an extremely thin rust preventive coating layer that secures dimensional accuracy during molding of the formed bond magnet, and a rust preventive treatment method thereof.

[0002]

2. Description of the Related Art As electronic devices, especially computers, communication devices, etc. have become smaller and higher in performance, motors and sensors have become smaller, and plastic bond magnets (hereinafter referred to as bond magnets) used in these motors have also become smaller. -Higher performance is required. Conventional bonded magnets were mainly bonded magnets using ferrite magnetic materials, but today, rare-earth bonded magnets with even higher magnetic properties have been developed, and the size and performance of magnets have greatly advanced. . Especially R-Fe
An R—Fe—B based bonded magnet using a —B based magnetic material has become a representative of rare earth bonded magnets. However, all the raw material components of the R-Fe-B based bonded magnet have a property of being extremely easily oxidized, and in particular, since a large amount of Fe component is present, there is a problem that they are easily corroded only by the base surface of the magnet. there were. Furthermore, because of the manufacturing characteristics of the bonded magnet, in which a binder component is added to the magnetic powder, which is a raw material component that easily oxidizes, and compression-molded into a product shape, the magnet surface is porous so that the inside of Since the outside air communicates with the magnet, the magnet has a problem that it is very easily corroded only in the green state.

To cope with this corrosion problem, various surface treatment methods of coating the surface with a resin coating or the like to prevent rusting have been used and have been put to practical use as product magnets. A typical surface treatment method is to apply various resin coatings to the surface of the bonded magnet, and generally spray coating, electrodeposition coating, dip coating (see JP-A 1-166519 and JP-A 1-245504). ) Is adopted. However, in spray coating, the corrosion resistance is practically satisfactory by selecting an appropriate resin coating and applying multiple coatings. It is difficult to maintain the thickness uniformity, and the dimensional accuracy tends to be low. Moreover, there is a lot of paint loss, and the number of processes increases due to the need to reverse the work to be coated,
The cost tends to be high.

Corrosion resistance in electrodeposition coating is superior to that in spray coating, and film thickness coating having a film thickness of about 15 to 30 μm is more uniform than spray coating. However, in terms of film formation, thin film coating of 10 μm or less is extremely difficult from the principle of electrodeposition coating. Furthermore, work steps to set / reset the magnets to be coated on the electrodes individually and touch-up coating individually on the contact traces of the electrodes after coating are required, especially for small-diameter ring-shaped bond magnets. There is a problem that is not suitable for applying the coating. Further, the dip coating method is inferior to the above-mentioned coating method in corrosion resistance, but it is an advantageous method that is inexpensive and requires a small number of steps. Even if a thin coating is applied, it can be performed from about 5 μm. However, it is difficult to form a uniform coating layer, and the film thickness tends to be non-uniform, and with bonded magnets with many voids such as voids and grooves on the surface, it is not possible to completely seal and fill them. During the curing and drying treatment of, the internal gas expands, expands due to jetting, and pinholes are generated, and the dimensional accuracy of the magnet deteriorates. Further, there is also a problem that problems such as sticking of magnets to be coated to each other due to swelling are likely to occur.

[0005]

The problem to be solved by the present invention is to solve the problems of the dipping treatment method in the conventional method with respect to voids such as holes and grooves on the surface of the bonded magnet. A conventional bonded magnet with a thin film, excellent in film thickness uniformity and product dimensional accuracy, obtained by directly compressing metal powder, filling / covering and sealing, and then performing resin dipping treatment in a reduced pressure atmosphere. It is to propose a bonded magnet having higher corrosion resistance performance. Further, in addition to obtaining such a bonded magnet, we will propose a surface treatment method for a bond magnet which is simpler in process than various known rustproofing methods for bond magnets, low-cost and labor-saving, and environmentally friendly. It is what

[0006]

In order to solve the above-mentioned problems, the present invention firmly fills the voids between the magnet particles, which is a characteristic of the porous surface texture of the bonded magnet, to the same extent as the surface of the magnet body. By flattening the surfaces, an entire thin surface thereof is covered with an extremely thin resin coating layer to solve the above problems. First, in order to fill the voids on the surface of the bond magnet to the same extent as the surface of the magnet body, blast media such as shots and relatively soft metal powder are simultaneously projected onto the bond magnet, or these shots, Put the metal powder and bond magnet in the container,
The surface of the bonded magnet was made flat by rotating or vibrating the entire container. Next, the bonded magnet is coated under a reduced pressure atmosphere so that the entire surface of the bonded magnet is coated with a uniform and thin resin coating layer, and the resin component also penetrates into the minute gaps remaining on the surface. Was immersed in a resin solution such as epoxy.

The bonded magnet of the present invention made by paying attention to the above two points is a porous magnet main body having a void portion communicating with the surface, and compression of the metal powder filled / covered in at least the void portion. A bonded magnet having a rust preventive coating layer including a body portion and a resin layer such as epoxy coated on the entire surface of the magnet body including the compressed body portion. The rust preventive coating layer has an average thickness of 10 μm or less (at least 3 μm, at most about 12 μm), and the bond magnet is an R—Fe—B type bond magnet. To do. Furthermore, the rust preventive coating treatment method of the present invention for obtaining the bonded magnet comprises compressing a metal powder in the voids of the magnet communicating with at least the surface of the porous magnet body having voids in the inside and the surface. Meanwhile, the method is characterized by including a step of filling and coating to form a compressed body portion, and a step of coating the entire surface of the magnet body including the compressed body portion with a resin layer such as epoxy under a reduced pressure atmosphere.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments will be described below with reference to the drawings in order to facilitate understanding of the present invention. Since the bonded magnet is compression-molded by pressing while binding the magnet powders together with the binder, the particles 1 of the magnet powder have a structure in which they are stacked flatly along the surface (Fig. 1).
(See (A), and so on). Between the particles 1 of the magnet powder, a large number of voids 2 such as holes and grooves exist inside and on the surface of the magnet body. The relatively soft metal powder such as Zn, Cu, Al, and Sn is projected into the voids 2 on the surface of the magnet body among the voids 2 by using blast media such as shots together or externally. From the magnet, a striking force is applied by rotating, rocking, vibrating, or agitating to fill and coat the metal powder while compressing the metal powder, and the metal powder compression body 3 for sealing the void 2 is provided. Flatten the surface of the body
(Figure 1 (B)). The soft metal used here refers to a metal that is softer than both the magnetic powder particles and the media. As a post-treatment for such a metal powder filling coating, the soft metal compressed powder that adheres excessively and weakly to the surface of the magnet body is removed by washing.
(Figure 1 (C)). In this state, the surface of the magnet powder particle 1 is partially exposed. Next, the entire surface of the magnet body flattened by the compression body portion 3 is coated with the resin layer 4 having an anticorrosion function, but a fine gap is formed around the compression body portion 3 on the surface of the magnet body. Since it remains, the resin component also penetrates into these minute gaps, so that the magnet is immersed in an epoxy resin solution under a reduced pressure atmosphere so as to ensure the sealing of the void 2 (Fig. 1 (D)). ). After such dipping treatment, the resin layer 4 is cured by heating in a conventional manner to obtain a thin and uniform rust preventive coating layer 5 having an average thickness of 10 μm or less (FIG. 1 (E)). It should be noted that the resin component can also penetrate into the voids 2 inside the magnet by the reduced pressure atmosphere, and further improve the sealing property of the voids 2 on the magnet surface.

[0009]

Next, specific examples of the present invention will be described. Example 1 A magnetic powder of Fe-Nd-B amorphous alloy having an average particle size of 100 μm, which was produced by melt quenching a melt of 85 at% Fe-10 at% Nd-5 at% B alloy, was coated with an epoxy resin as a binder component. 2.5% by weight was added and kneaded, then charged into a mold and compression-molded at a pressure of 7.5 t / cm ² , and a cylindrical bonded magnet with an outer diameter of 6.0 mm × an inner diameter of 5.0 mm × a length of 10.0 mm. Was obtained (Fig. 2,
Step 1; S1, the same hereafter). This magnet was heat-treated at about 150 ° C for about 60 minutes to cure the epoxy resin component (Fig. 2, S
2). In order to remove the burr at each end, 500 pieces of the obtained cylindrical bonded magnet were placed in a rotating container having a volume of 5 liters together with spherical alumina media having a diameter of 3 mm and a diameter of 3 mm and 1 liter of pure water. Then, the surface was polished at 20 rpm for about 20 minutes (FIG. 2, S3). The polished cylindrical bonded magnet was subjected to ultrasonic cleaning in pure water (FIG. 2, S4), then heated to about 80 ° C. and dried (FIG. 2, S5). 500 pieces of these bond magnets 8 were placed in a blast coating container 10 of 3 liters shown in FIG.
While rotating 10 at 10 revolutions per minute, from the nozzle 12 on the container opening side, a stainless ball 14 with a diameter of 1.5 mm and a scale-like aluminum at a rate of 5 g per 1 liter of apparent volume of the stainless ball 14 Powder 16 (Thickness 0.1 to 1 μm, average particle size 50
Spray coating was carried out for 10 minutes at a shot spray pressure of 0.5 kg / cm ² combined with air pressure, using the blast coating medium 18 mixed with (μm) (FIG. 2, S6). In addition, 20 in FIG. 3 indicates a recovery portion of the coating medium 18 which has overflowed.

Next, the metal-coated bond magnet 8 is separated from the stainless balls 14, and then MEK (methyl ethyl ketone) is used.
Swing cleaning was performed for 2 minutes using a basket in the above solution to remove incompletely adhered aluminum powder by cleaning (Fig. 2, S
7). The MEK used here has a surface activating effect that promotes the removal of excess aluminum powder and the like. Then, it was heated to about 80 ° C. and dried (FIG. 2, S8). Then two-component epoxy resin; 1
This bond magnet was immersed in a MEK solution containing 10 parts by weight of an epoxy component and mixed with 3 parts of a catalyst type curing agent to 00 parts, and impregnated under a reduced pressure atmosphere of 0.15 Torr (Fig. 2, S
9). The reason why MEK is used here is to increase the wettability of the magnet powder particles and the adhesion to the resin. The pressure of the reduced pressure atmosphere is 0.1 Torr or more at which the above solution does not boil,
Moreover, the range below atmospheric pressure is desirable. After that, curing treatment was performed in an oven at about 140 ° C. for 60 minutes (FIG. 2, S10).

Example 2 500 bonded magnets 2 obtained in the same manner as in Example 1
Regarding No. 2, after deburring and polishing, ultrasonic cleaning was performed and heating and drying were performed. As shown in FIG. 4, these bonded magnets 22 have a apparent volume of 2 liters, steel balls 24 having a diameter of 3 mm and hard Ni plating of 30 μm or more on the surface, and 3 g of scale-like aluminum powder 26 (thickness 0.3 to 1 μm, The average particle diameter is 50 μm) and the mixture is placed in a vibration vessel 28 having a volume of 3 liters, and the vibration vessel 28 is attached to the vibration device 30 having the structure shown in FIG.
Under the vibration condition of Hz, the bond magnet 22 was subjected to the metal powder coating treatment by the collision pressure between the steel ball 24 and the aluminum powder 26 for 20 minutes. Next, this metal coated bond magnet 22
After being separated from the steel balls 24, rocking washing by tapping was performed in tap water for 2 minutes to wash and remove the aluminum powder 26 imperfectly attached to the surface. Thereafter, warm air drying at about 80 ° C. was performed for 10 minutes, and thereafter, this bond magnet 22 was immersed in a 10% by weight MEK solution of the epoxy component similar to that of Example 1 and impregnated under a reduced pressure atmosphere of 0.15 Torr. . After that, curing treatment was performed for 60 minutes in an oven at about 140 ° C. In FIG. 4, 32 is a motor provided below the vibration container 28, 34 is an eccentric weight fixed to the lower end of the rotation shaft of the motor 32 for vibrating both the container 28 and the motor 32, and 36. Is a coil spring that stands upright from the base 40 to keep vibration within a predetermined range, and 38 is a guide pin vertically inserted into the spring 36.

Example 3 500 bond magnets obtained in the same manner as in Example 1 were deburred and polished, and then ultrasonically cleaned to further improve the wettability of the magnet surface. It was dipped in an aqueous solution containing 2% of a coupling agent for 2 minutes. Next about 80 ℃
After being dried by heating in, the bonded magnet was subjected to the metal powder coating treatment under the same conditions as in Example 2 in the vibration vessel 28 used in Example 2. Further, after separating the metal-coated bonded magnet from the metal spheres, rocking washing with a colander in tap water is carried out for 2 minutes to wash and remove the metal powder that is incompletely attached to the surface, and then the above coupling agent is again used. It was immersed for 2 minutes in an aqueous solution containing. Thereafter, warm air drying at about 80 ° C. was performed for 10 minutes, and the same MEK containing 10% by weight of the epoxy component as in Example 1 was used.
The bonded magnet was immersed in the solution and impregnated under a reduced pressure atmosphere of 0.15 Torr. Finally, it was cured in an oven at about 140 ° C. for 60 minutes.

Comparative Example 1 500 bond magnets obtained in the same manner as in Example 1 were deburred and polished, and then ultrasonically cleaned to obtain about 80
It was heated to ° C and dried. Next, 80% by weight of a dedicated diluting solution (thinner) was added to 20% by weight of a commercially available thermosetting epoxy coating stock solution to prepare an epoxy coating solution, and the bond magnet was immersed in this for 5 minutes under normal pressure. Further, the bonded magnet was placed in a basket and the immersion liquid was sufficiently drained off, and then cured in an oven at about 140 ° C. for 60 minutes. The surface texture of the bonded magnet of Comparative Example 1 will be described with reference to FIG.
Shows a structure in which particles 1 of the magnet powder are flatly stacked on each other along the surface of the magnet and immediately after the above deburring, washing and drying. FIG. 5 (B) shows a state in which the surface of the magnet is coated with the epoxy resin layer 4 by the above dipping, and the film thickness is about 20 to 40 μm. When the above curing treatment is further applied, the resin layer 4 has a thickness of 5 to 1 as shown in FIG. 5 (C).
Although it becomes 5 μm, the gas in the holes inside the magnet expands and is released to the surface side of the magnet, so that the resin layer 4 passes through the void portion 2 on the surface and tries to be ejected to the outside. At this time, a bulge 6 and a pinhole 7 are formed in the vicinity of the void portion 2 on the surface, and the inside and outside of the magnet are in communication with each other through the pinhole 7.

Then, with respect to each of 50 bonded magnets obtained by each of the treatments of Examples 1, 2, and 3 and Comparative Example 1, the cylindrical inner diameter and outer diameter were measured, and untreated. In addition to determining the film thickness from the dimensional difference with the magnet in the state, roundness and coaxiality are also measured using a roundness measuring machine and a surface roughness meter,
Compared to untreated magnet. The results are shown in Tables 1 and 2.

[0015]

[Table 1]

[0016]

[Table 2]

From these results, Examples 1, 2 and 3 are as follows for the inner and outer diameters of the film thickness, the roundness and the concentricity.
Compared with the conventional dip coating treated product of Comparative Example 1, all have excellent dimensional and shape stability, and have a thin film with excellent uniformity that ensures the dimensional accuracy of the original magnet molding. It was a thing. In particular, since the coupling agent was used in Example 3, the adhesion and affinity between the particles of the magnet powder and the metal powder or the epoxy resin were good, and the dimensional accuracy was the best.

Next, 20 pieces of each of the bonded magnets obtained by the treatments of Examples 1, 2, 3 and Comparative Example 1 and untreated products (bases) were respectively dissolved in an epoxy resin adhesive solution. It was immersed for 60 minutes in a state of being kept warm at 80 ° C. After that, the adhesive component on the surface of the magnet was wiped off, the difference in weight before and after immersion was determined, and this was measured as the amount of absorbed adhesive. Further, with respect to each of the bonded magnets obtained by the processing of Examples 1, 2, 3 and Comparative Example 1, and 20 pieces of each untreated product (base material), a load cell was applied from a direction perpendicular to the axial direction of the cylindrical shape. A stress load (~ 10 kg / cm ² ) was applied and the fracture strength was measured. Table 3 shows the results. In this experiment, since the bonded magnet is generally fixed to the casing or the like with an adhesive, its effect on the adhesive force is confirmed.

[0019]

[Table 3]

From the above results, in the adhesive absorption amount,
In Examples 1, 2, and 3, the amount was 10% compared with the untreated product (base material), and compared with Comparative Example 1, the absorption amount was 50% or less. Regarding the breaking strength, Examples 1, 2 and 3 were about twice as much as the untreated product, and it was found that the breaking strength was about 1.5 times as much as Comparative Example 1. did. From these, in the bonded magnet according to the present invention, the adhesive is not easily absorbed inside the tissue due to the sealing function of the compressed body portion in the void portion, and the adhesive adheres firmly to the magnet surface, so that the original adhesive force of the adhesive is obtained. It is understood that he was able to obtain strong resistance to external forces as well.

Furthermore, for each of 50 bonded magnets obtained by the treatments of Examples 1, 2, 3 and Comparative Example 1, and 50 untreated products (bases), 5 pieces were added to a petri dish having a volume of 100 ml.
% Saline was added and each was immersed in saline kept at 25 ° C., and the time required for the saline to turn pale brown red was measured. This is because the chlorine ions contained in the saline solution react with the iron of the magnet component to produce iron chloride, which causes a brown-red discoloration, and it is said that the magnet surface begins to microscopically corrode. It was judged. The results are shown in Table 4 (◯ in the table means that there was no discoloration).

[0022]

[Table 4]

From Table 4, Examples 1 and 2 are more than twice as much as the epoxy resin paint of Comparative Example 1 by immersion coating, and Example 3
In, the corrosion resistance of 3 times or more was shown. The untreated state (base material) showed a brown-red discoloration within 1 hour.
From this result, it is easy for the bonded magnet according to the present invention to be remarkably excellent in terms of corrosion resistance due to the strong anticorrosive coating layer accompanied with the sealing function of the compression body portion and the penetration into the inside of the resin layer. I can understand.

The present invention is not limited to the above embodiments, but can be implemented in various modes. The washing and drying steps as the pretreatment of the metal powder coating treatment are not essential and may be omitted depending on the properties of the magnet used. Also,
Also in the metal powder coating treatment step, in addition to the above-described respective examples, for example, the bonded magnet group is moved on the belt conveyor, and the metal powder is projected at a high pressure together with a blasting medium such as shot from above, on the way. It is also possible to reverse each bond magnet and project further.
Moreover, the metal powder used is not limited to Zn, Cu, Al, and Sn as long as it is relatively soft with respect to the blast media, etc., and various metal powders such as brass, lead, solder or scale stainless, Ni, bronze are adopted. be able to. In addition to the steel balls and stainless spheres with a diameter of 1 to 4 mm, blast media also have Ni spheres, copper spheres, hard Ni plating or Cr plating on their surfaces, alumina, mullite (SiO ₂ ), Ceramic spheres containing these as the main components can also be used.

Further, the resin coated on the surface of the bond magnet is not limited to the epoxy type, but may be phenol type, acrylic type, polyamide type, nylon type, polyvinyl chloride type, phthalate type, polyester type, polypropylene type, polyolefin type. A diluting liquid can be used in combination depending on the magnet to which the resin such as the above is applied and the metal powder used for the coating.
Further, the coupling agent is not limited to the silane type, but a titanate type, an aluminum type or the like can be used. The R-Fe-B based bonded magnet to be applied is also in the range of 8 to 18 at% R-73 to 88% Fe-4 to 9% B including the above-mentioned embodiment, and the rare earth element is Nd other than Nd. , Y, La, Ce, Pr, Sm, Eu, Gd, T
It also includes those in which one or more of b and Dy are used in combination, and further, a part of Fe is substituted with a transition metal such as Al, Co and Nb.

[0026]

As described above, the bonded magnet of the present invention has an extremely thin and uniform film on its surface, more specifically, an anticorrosion coating layer having an average thickness of 10 μm or less. The dimensional accuracy at the time of molding can be ensured with high accuracy, the original magnetic characteristics of the magnet are not deteriorated, the strength of the magnet main body can be improved, and the corrosion resistance can be significantly improved. Further, according to the rust preventive treatment method of the present invention, it is possible to treat the bonded magnet having excellent performance as described above with a small number of simple steps at a stable quality at a low cost, and further, a general treatment agent Since it is necessary to use only the processing liquid,
From the environmental point of view, a very preferable treatment method can be provided.

[Brief description of drawings]

FIG. 1 is an enlarged schematic view of a surface texture of a porous bonded magnet of the present invention.

FIG. 2 is a flow chart showing steps of an embodiment of the rustproofing method of the present invention.

FIG. 3 is a side sectional view of a peening coating apparatus used for the metal coating treatment of the present invention.

FIG. 4 is a side sectional view of a vibration container and a vibration device used for the metal coating treatment of the present invention.

FIG. 5 is an enlarged schematic view of a surface texture of a bonded magnet of a comparative example.

[Explanation of symbols]

 1 Magnet Powder Particles 2 Voids 3 Compressed Body 4 Resin Layer 5 Anticorrosion Coating Layer

Claims (4)

[Claims] 1. A porous magnet body having a void portion communicating with the surface, a compressed body portion of metal powder filled and coated in at least the void portion, and a magnet body including the compressed body portion on the entire surface of the magnet body. A bonded magnet having a rust preventive coating layer comprising a coated resin layer such as epoxy. 2. The bonded magnet according to claim 1, wherein the thickness of the anticorrosion coating layer is 10 μm or less on average. 3. The bonded magnet according to claim 1, wherein the bonded magnet is an R—Fe—B based bonded magnet. 4. A step of forming a compressed body part by compressing and filling a metal powder into a void part communicating with at least the surface of a porous magnet body having a void part inside and on the surface thereof, and the above-mentioned compressed body. And a step of coating a resin layer of epoxy or the like on the entire surface of the magnet body including the portion under a reduced pressure atmosphere.