JP2006310823A - Bond magnet and its production process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bond magnet exhibiting excellent rust prevention performance as compared with a conventional one, and to provide its production process. <P>SOLUTION: The process for producing a bond magnet in which a protective layer is formed on the surface of a bond magnet element containing a rare earth element comprises a step for forming a protective layer containing phosphor on the surface of a bond magnet element by touching the bond magnet element to solution containing a phosphate and acid ions. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a bonded magnet, in particular, a bonded magnet having a protective layer on the surface and a method for manufacturing the bonded magnet.

  Conventionally, as a magnet containing a rare earth element, a sintered magnet obtained by sintering magnetic powder and a bonded magnet formed by mixing magnetic powder and a binder resin are known. Since these magnets containing rare earth elements contain a rare earth element that is relatively easily oxidized as a main component, rust is likely to occur, and the corrosion resistance tends to be relatively low. For this reason, deterioration of the performance as a magnet was remarkable at the time of manufacture and use.

  In order to solve such problems, the sintered magnet has corrosion resistance by forming a protective layer having corrosion resistance on the surface thereof by electrodeposition coating, or by applying a sol solution and heat-treating at 200 ° C. or higher. For example, a protective layer is formed to improve the corrosion resistance of the magnet. However, the bond magnet, which is another magnet containing rare earth elements, contains a binder resin, so that it is difficult to perform electrodeposition coating, and the binder resin deteriorates due to the above high-temperature heat treatment. For these reasons, it is difficult to form a protective layer similar to a sintered magnet.

Therefore, as a method for improving the corrosion resistance of the bonded magnet different from the above, a method of forming a chemical conversion film by performing chemical conversion treatment on the surface is known. For example, Patent Document 1 below discloses a resin-bonded magnet (bonded magnet) whose surface is coated with phosphate.
Japanese Patent Application Laid-Open No. 64-13707

  However, even with the above-described method for forming a chemical film, it has still been difficult to sufficiently improve the corrosion resistance, particularly rust prevention performance, of the bonded magnet.

  Then, this invention is made | formed based on such a situation, and it aims at providing the bonded magnet which has the antirust performance outstanding compared with the former, and its manufacturing method.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors can form a protective layer that provides superior corrosion resistance as compared with the prior art by adding a predetermined additive to the chemical conversion solution. As a result, the present invention has been completed.

  That is, the manufacturing method of the bonded magnet of the present invention is a manufacturing method of a bonded magnet in which a protective layer is formed on the surface of a bonded magnet body containing a rare earth element. And a step of forming a protective layer containing phosphorus on the surface of the bonded magnet body by contacting with a solution containing.

  Thus, in the manufacturing method of the bonded magnet of this invention, the acid ion is contained as an additive in the aqueous solution (chemical conversion liquid) containing a phosphate. The protective layer containing phosphorus thus formed can exhibit excellent corrosion resistance as compared with a conventional chemical conversion film.

  Although this factor is not necessarily clear, the present inventors consider as follows. That is, the formation of the chemical conversion film on the surface of the magnet body is such that the metal contained in the magnet body becomes ions and dissolves in the chemical conversion treatment solution, and phosphate ions react in this eluted portion of the magnet body. Thus, it is considered that a protective layer is formed. And when a protective layer is formed by this mechanism, if acid ions are contained in the chemical conversion treatment liquid as in the present invention, the acid ions oxidize metal ions eluted in the chemical conversion treatment liquid. It is considered that the protective layer formation reaction is advantageous due to the action such as removal outside the system and promoting the elution of the metal into the chemical conversion treatment solution, and as a result, a good protective layer is formed. .

  In the method for producing a bonded magnet of the present invention, the concentration of acid ions in the solution is preferably 0.75 mmol / L or more. If it carries out like this, there exists a tendency for formation of a protective layer to become still more advantageous.

  More specifically, the acid ion is preferably at least one ion selected from the group consisting of nitrite ion, sulfite ion and acetate ion. These acid ions are excellent in the above properties and can be easily added to the chemical conversion solution. Therefore, a protective layer having high corrosion resistance can be easily formed by including these acid ions in the chemical conversion treatment liquid.

The bonded magnet according to the present invention includes a bonded magnet element containing a rare earth element and a protective layer containing Zn and P formed on the surface of the magnet element, and the weight M of Zn contained in the protective layer. the ratio _M Zn / _{M P} of the weight _{M P} of _Zn and P is characterized satisfying the condition represented by the following formula (1).
2.4 ≦ M _Zn / M _P ≦ 7.8 (1)

  The protective layer satisfying such a condition is satisfactorily formed by the method for manufacturing a bonded magnet of the present invention. And the bonded magnet provided with such a protective layer has the corrosion resistance excellent compared with the past.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the bonded magnet which has the antirust performance outstanding compared with the past, and its manufacturing method.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same element through all figures, and the overlapping description is abbreviate | omitted.

  First, the structure of the bonded magnet of this embodiment will be described with reference to FIGS.

  FIG. 1 is a perspective view showing a bonded magnet according to the present embodiment. 2 is a diagram schematically showing a cross-sectional structure along the II-II direction of the bonded magnet shown in FIG. As shown in the figure, the bonded magnet 1 has a configuration including a magnet element body 3 (bonded magnet element body) and a protective layer 5 formed so as to cover the surface thereof.

  The magnet body 3 includes a magnetic powder containing a rare earth element and a binder resin, and the magnetic powder is bound by the binder resin. The magnetic powder containing the rare earth element is not particularly limited as long as it is normally used as a raw material for the rare earth magnet, and examples include those containing rare earth elements such as Sm and Nd. More specifically, Sm—Co based magnetic powder, Nd—Fe—B based magnetic powder, Sm—Fe—N based magnetic powder and the like can be mentioned.

Among the magnetic powders described above, as the magnetic powder, Sm—Co based magnetic powder represented by SmCo ₅ or Sm ₂ Co ₁₇ or Nd—Fe—B based magnetic powder represented by Nd ₂ Fe ₁₄ B is used. preferable. These magnetic powders can exhibit excellent magnetic properties when the bonded magnet 1 is formed. Moreover, it is especially preferable that the magnetic powder has an average particle size (major axis) of 100 to 200 μm and a maximum particle size of 500 μm or less because good magnetic properties can be obtained.

  As the binder resin, a thermosetting resin or a thermoplastic resin capable of binding magnetic powders can be used. Examples of such binder resins include thermosetting resins such as epoxy resins and phenol resins, styrene-based, olefin-based, urethane-based, polyester-based, and polyamide-based elastomers, ionomers, ethylene-propylene copolymers (EPM), and ethylene. -Thermoplastic resins such as ethyl acrylate copolymer. Especially, a thermosetting resin is preferable and an epoxy resin or a phenol resin is more preferable.

  In the magnet body 3, the magnetic powder and the binder resin are preferably blended in a mixing ratio as shown below. That is, the magnet body 3 preferably contains 95 parts by mass or more of magnetic powder with respect to 100 parts by mass in total of the magnetic powder and the binder resin. When the blending amount of the magnetic powder is less than 95 parts by mass, the magnetic properties of the bond magnet 1 tend to be deteriorated. However, from the viewpoint of sufficiently binding the magnetic powder, it is preferable that at least 1.5 parts by mass of a binder resin is included.

  The magnet body 3 may contain various metal soaps such as zinc stearate, titanate-based, silane-based coupling agents, and the like in addition to the magnetic powder and binder resin described above.

  The protective layer 5 is a layer containing phosphorus formed on the surface of the magnet body 3 containing rare earth elements, and has a function of reducing the influence of outside air (oxygen, moisture, etc.) on the magnet body 3. Yes. Such a protective layer 5 is a chemical conversion film formed by subjecting the magnet body 3 to chemical conversion treatment as will be described later. The protective layer 5 is preferably a layer containing a metal phosphate, and more preferably a layer containing a metal phosphate as a main component. Examples of such a metal phosphate include zinc phosphate, manganese phosphate, iron phosphate, zinc calcium phosphate, and the like.

Of these, the protective layer 5 is preferably a layer containing phosphorus (P) and zinc (Zn), and more specifically, a layer containing zinc phosphate. Such a protective layer 5 can impart excellent corrosion resistance to the bonded magnet 1. Examples of zinc phosphate include compounds represented by Zn ₃ (PO ₄ ) ₂ .4H ₂ O, but the protective layer 5 contains a composition containing phosphorus and zinc different from this chemical composition. It may be.

In this case the protective layer 5 is a layer containing zinc phosphate and the mass M _P of the mass M _Zn and P of Zn contained in the layer 5 have the relationship represented by the following formula (1) preferable. In addition, fixed_quantity | quantitative_assay of phosphorus and zinc in the protective layer 5 can be performed using a laser ablation-ICP mass spectrometer (LA-ICP-MS).
2.4 ≦ M _Zn / M _P ≦ 7.8 (1)

When the value of M _{Zn /} M _P in the protective layer 5 is outside the above range, the effect of improving corrosion resistance by the protective layer 5 as compared with the case in the above range tends to decrease. From the viewpoint of obtaining such a corrosion resistance improving effect _better, the value of M Zn / _{M P} is more preferably a 4.5 to 6.0.

  Next, a method for manufacturing the bonded magnet 1 having the above-described configuration will be described.

  First, an alloy having a desired composition for forming a magnetic material containing a rare earth element is manufactured by a process such as a casting method or a strip casting method. The obtained alloy is coarsely pulverized using a coarse pulverizer such as a jaw crusher, brown mill, stamp mill, etc., and then the magnetic powder has a suitable particle size described above by a fine pulverizer such as a jet mill or an attritor. Thus, the powder is pulverized to obtain a magnetic powder.

The obtained magnetic powder is mixed with a binder resin, a curing agent and the like, and then charged into a kneader such as a pressure kneader and kneaded. Next, the kneaded product is compression-molded by a compression molding machine or the like. At this time, magnetization may be performed simultaneously by performing compression molding in a magnetic field. Magnetization may be performed separately after compression molding. From the viewpoint of obtaining the magnet body 3 having excellent magnetic properties, it is preferable to perform compression molding at a high pressure of about 784 to 980 MPa and about 8 to 10 t / cm ² .

  Then, when a thermosetting resin is used as the binder resin, the magnet body 3 is obtained by curing the binder resin by heating the obtained molded body at about 100 to 250 ° C. after compression molding. When a thermoplastic resin is used as the binder resin, such thermosetting does not have to be performed.

  Subsequently, the magnet body 3 is washed by spraying a solvent such as ethanol onto the magnet body 3 to remove excess magnetic powder and oil adhering to the surface of the magnet body 3. The solvent is not particularly limited as long as it has a sufficient cleaning function and does not affect the binder resin or the like in the magnet body 3, and a solvent other than ethanol may be used. Moreover, it may replace with washing | cleaning by solvent spraying, and may perform ultrasonic cleaning, and may use these together. After washing, the solvent and the like attached to the surface of the magnet body 3 is removed by natural drying or heat drying.

  And the surface adjustment process for performing the below-mentioned chemical conversion treatment favorably with respect to the magnet body 3 after washing | cleaning is performed. Specifically, for example, the magnet body 3 is immersed in a solution containing colloidal particles of titanium salt such as titanium phosphate, so that the colloid particles are attached to the surface of the magnet body 3. Thereby, the part to which this colloidal particle adhered becomes an active point, and subsequent chemical conversion treatment comes to be performed favorably. For the purpose of attaching the colloidal particles to the inside of the magnet body 3, the above-described immersion may be performed under reduced pressure.

  Next, chemical conversion treatment is performed by immersing the magnet body 3 in a solution (chemical conversion solution) containing phosphoric acid and acid ions, and a protective layer 5 made of a chemical conversion film containing phosphorus is formed on the surface of the magnet body 3. Thus, the bonded magnet 1 is obtained. Thereafter, the obtained bonded magnet 1 is washed with ion-exchanged water to remove the chemical conversion treatment liquid adhering to the surface, followed by drying at 85 ° C. for about 30 minutes, and the treatment is completed. Thus, the bonded magnet 1 having the structure shown in FIGS. 1 and 2 can be obtained.

The chemical conversion treatment solution used for the chemical conversion treatment can be prepared, for example, by adding a metal salt of an acid ion to a solution containing a metal phosphate and dissolving them. The chemical conversion treatment solution thus obtained contains ions such as PO ₄ ³⁻ , Zn ²⁺ , and acid ions. In the magnet element body 3 immersed in the chemical conversion solution, the metal (for example, Fe) in the constituent material of the element body 3 is dissolved in the chemical conversion solution by reacting with phosphoric acid. And on the surface where this dissolution has occurred, zinc ions and phosphate ions react to produce zinc phosphate. Such a reaction occurs on the surface of the magnet body 3 in a region where the magnetic powder is not covered with the binder resin.

As acid ions contained in the chemical conversion treatment liquid, nitrite ions, sulfite ions, acetate ions, adipate ions and the like are preferable. Of these, nitrite ions are preferred because they can simplify the treatment of the chemical conversion treatment solution after use. Also, when adding these acid ions as the metal salt, the cation component of such metal ^{salts, Ni 2+, Mn 2+, Na} +, Ca 2+, Fe 2+ or ^{Ce 2+} are preferred. More specifically, sodium nitrite, ammonium adipate, sodium acetate, nickel acetate, manganese sulfate, cerium sulfate, and the like are suitable as the metal salt of the acid ion added to the chemical conversion solution.

  In the chemical conversion treatment solution, the acid ion concentration is preferably 0.75 mmol / L or more, more preferably 1.5 mmol / L or more, and further preferably 2.25 mmol / L or more. If the concentration of acid ions in the chemical conversion solution is less than 0.75 mmol / L, the effect of improving corrosion resistance by adding such acid ions may not be sufficiently obtained. If the acid ion concentration is too high, the amount of sludge generated increases and the burden of wastewater treatment after treatment may increase, so the acid ion concentration in the chemical conversion liquid is 4.5 mmol / L or less. More preferably.

  The temperature of the chemical conversion treatment solution during the chemical conversion treatment is preferably 40 to 90 ° C, and more preferably 50 to 80 ° C. When the temperature condition of the chemical conversion treatment is less than 50 ° C., the solubility of each component in the chemical conversion treatment liquid is lowered, and the protective layer 5 having sufficient characteristics tends to be hardly obtained.

  Moreover, it is preferable that the processing time of a chemical conversion treatment shall be about 5 to 30 minutes. When the chemical conversion treatment time is less than 5 minutes, the protective layer 5 having a sufficient thickness tends not to be formed. On the other hand, if it exceeds 30 minutes, the time required for the chemical conversion treatment process becomes long and the cost for production increases, and the chemical conversion solution tends to evaporate and the concentration change of the solution may become undesirably large. is there.

  In addition, the acid ion concentration and temperature of the chemical conversion treatment liquid and the conditions of the chemical conversion treatment time tend to be influenced by each other. That is, for example, when the acid ion concentration is high, the chemical conversion solution temperature tends to be low and the chemical conversion treatment time may be short, and when the chemical conversion solution temperature is high, the acid ion concentration is low and the chemical conversion treatment is performed. Time tends to be short. Therefore, it is preferable to appropriately adjust the above three conditions in the chemical conversion treatment while considering each other's conditions so that the desired protective layer 5 is formed.

  For example, the treatment temperature and the acid ion concentration in the chemical conversion treatment are preferably set to 0.75 to 3.75 mmol / L at a temperature of 50 to 80 ° C, and at a temperature of 50 to 70 ° C, The acid ion concentration is more preferably 1.5-2.25 mmol / L.

  In such a manufacturing method of the bonded magnet 1, since the acid ion is contained in the chemical conversion treatment liquid as described above, the protective layer 5 can be satisfactorily formed on the surface of the magnet body 3. Therefore, the bonded magnet 1 in which the protective layer 5 is formed in this manner has excellent corrosion resistance as compared with that obtained using a chemical conversion treatment solution that does not contain acid ions.

  In addition, the bonded magnet of this invention and its manufacturing method are not necessarily limited to said embodiment. For example, in the above embodiment, the chemical conversion treatment liquid is brought into contact with the magnet element body 3 so as to be immersed in the chemical conversion treatment liquid. However, the present invention is not necessarily limited thereto. The liquid can be applied or sprayed to be brought into contact with the magnet body 3.

  Further, the chemical conversion treatment does not necessarily have to be performed so as to be immersed in the magnet body 3 in a chemical conversion treatment liquid containing both phosphate and acid ions in advance. After immersing the magnet element body 3 in the treatment liquid, it may be performed by adding acid ions to the chemical conversion treatment liquid in which the magnet element body 3 is immersed.

EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.
[Manufacture of bonded magnets]

(Examples 1-14, Comparative Examples 1-4)
An alloy containing 72% by mass of Fe, 19% by mass of Nd and 7% by mass of B was prepared and pulverized to obtain a magnetic powder. Next, the obtained magnetic powder was mixed with an epoxy resin as a binder resin, and then compression molded at a pressure of 980 MPa, and further heat-treated at 150 ° C. to cure the binder resin to obtain a magnet body. Next, the obtained magnet body was washed with ethanol and dried, and then immersed in a colloidal solution of titanium phosphate under reduced pressure to perform surface conditioning treatment.

  Then, the magnet body is immersed in a chemical conversion treatment solution consisting of zinc phosphate and a solution containing the types of additives shown in Table 1, and subjected to chemical conversion treatment according to the chemical treatment solution temperature and treatment time shown in Table 1. A protective layer made of a chemical conversion film was formed on the surface of the element body to obtain a bonded magnet. In addition, the addition amount of the additive to the chemical conversion treatment liquid was adjusted so that the acid ion concentration in the chemical conversion treatment liquid became the value shown in Table 1.

Then, after wash | cleaning the obtained bonded magnet with ion-exchange water, it dried at 85 degreeC for 30 minutes, and completed the bonded magnet of Examples 1-14 and Comparative Examples 1-4.
[Evaluation of rust prevention performance]

  Ten bonded magnets of Examples 1 to 14 and Comparative Examples 1 to 4 were produced, and these were left in a high temperature and high humidity environment of 60 ° C. and 95% RH for 500 hours. Then, the surface of all the bonded magnets was observed with a microscope (20 times) to confirm whether or not rust was generated. Then, the number of samples (hereinafter referred to as “non-defective products”) in which generation of rust was not observed among the ten samples of each example or comparative example was counted. Based on this result, the ratio (non-defective product rate (%)) at which good products were obtained with the bonded magnets of the examples and comparative examples was calculated. The obtained results are shown in Table 1.

  From Table 1, if the chemical conversion treatment temperature is the same, the bonded magnet of the example obtained by adding the additive to the chemical conversion liquid is compared with the bonded magnet of the comparative example obtained without adding the additive. It was confirmed that a high yield rate was obtained. Moreover, in the implemented range, it was confirmed that a higher non-defective rate is obtained when the processing temperature is higher.

Furthermore, when the chemical conversion liquid temperature is high (70 ° C. or higher), a certain percentage of non-defective products was obtained even when no additive was added. However, when the chemical conversion liquid temperature was low (50 ° C.), the addition of no additive was sufficient. The yield rate was not obtained. From this, it has been found that by adding an additive, a bonded magnet can be produced at an excellent yield rate even when the chemical conversion solution temperature is low.
[Protective layer analysis]

As a result of observing the surfaces of the bonded magnets of Examples 1 to 3 and 5 to 8 and Comparative Examples 1 to 4 with a microscope, the surface of the protective layer has a region where silver magnetic powder is present and a yellow magnetic powder. It was confirmed that the area was mixed. Then, the area | region of the silver magnetic powder in each bond magnet, the area | region of a yellow magnetic powder, and the corner | angular part of a bond magnet are laser ablation-ICP mass spectrometer (LA-ICP-MS; laser part: New Wave Research). LUV266X manufactured by ICP, MSP-MS part: Agilent 7500S manufactured by Yokogawa Analytical Systems, laser condition: wavelength 20 μm, frequency 10 Hz), the mass of Zn contained in each region (M _Zn ) and the mass of _P (M _P ) Was quantified. Then, from the results obtained it was calculated the value of _M Zn / _{M P} in each region. The obtained results are shown in Table 2.

From Table 2, the bonded magnets of Examples obtained by adding the additives in the chemical treatment solution, it is confirmed that the value of M _{Zn /} M _P is in the range of 2.4 to 7.8 both It was. Therefore, according to the protective layer having a value of such M _{Zn /} M _P, it was found to be as excellent corrosion resistance is obtained.

It is a perspective view which shows the bonded magnet of this embodiment. It is a figure which shows typically the cross-sectional structure which follows the II-II direction of the bonded magnet shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Bond magnet, 3 ... Magnet base body, 5 ... Protective layer.

Claims (4)

A method of manufacturing a bonded magnet that forms a protective layer on the surface of a bonded magnet body containing a rare earth element,
A process for producing a bonded magnet, comprising the step of bringing the bonded magnet body into contact with a solution containing phosphate and acid ions to form a protective layer containing phosphorus on the surface of the bonded magnet body. Method.   The method for producing a bonded magnet, wherein the solution has a concentration of the acid ions of 0.75 mmol / L or more.   The method for producing a bonded magnet according to claim 1, wherein the acid ion is at least one ion selected from the group consisting of nitrite ion, sulfite ion and acetate ion. A bonded magnet body containing a rare earth element, and a protective layer containing Zn and P formed on the surface of the magnet body,
The ratio _M Zn / _{M P} of the mass _{M P} of the mass _{M Zn} and P of Zn contained in the protective layer, bonded magnets, wherein the condition is satisfied of the following formula (1).
2.4 ≦ M _Zn / M _P ≦ 7.8 (1)

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