JPH0644523B2 - Permanent magnet having excellent corrosion resistance and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet containing R (R is at least one of rare earth elements including Y), B and Fe as main components, and has a corrosion resistant chemical conversion coating and electrodeposition coating on the surface. The present invention relates to a rare earth / boron / iron-based permanent magnet in which corrosion-resistant resin layers are sequentially laminated to improve the corrosion resistance of a permanent magnet, and a method for manufacturing the same.

[0002]

2. Description of the Related Art The typical current permanent magnet materials are alnico, hard ferrite and rare earth cobalt magnets. With the recent destabilization of the raw material situation for cobalt, the demand for alnico magnets containing 20 to 30 wt% of cobalt has decreased, and inexpensive hard ferrites containing iron oxide as the main component have become the mainstream of magnet materials. became.

On the other hand, rare earth cobalt magnets contain 5% cobalt.
It is very expensive because it contains Sm, which is not contained in rare earth ores, in addition to 0 to 60 wt%, but its magnetic properties are significantly higher than other magnets. It has become widely used in circuits.

Therefore, the present inventor first found that expensive Sm and C
Fe-B-as a new high-performance permanent magnet containing no o
R type (R is at least one of rare earth elements including Y)
A permanent magnet was proposed (Japanese Patent Application No. 57-145072).
In this permanent magnet, R is a light rare earth resource rich in Nd and Pr, and Fe is 25M
It is an excellent permanent magnet that exhibits an extremely high energy product over GOe.

[0005]

However, the Fe-BR permanent magnet having the above-mentioned excellent magnetic properties contains, as the main components, the rare earth element and iron which are easily oxidized in the air, and therefore the Fe- When a B-R permanent magnet is incorporated in a magnetic circuit, the oxide generated on the surface of the magnet causes a decrease in the output of the magnetic circuit and a variation among the magnetic circuits. There was a problem of pollution to.

Therefore, in order to improve the corrosion resistance of the above Fe-BR type permanent magnet, there is proposed a permanent magnet whose surface is coated with a corrosion resistant resin layer by a spray method or a dipping method (Japanese Patent Application No. 58-171907). No.) However, since the resin coating by the spray method has directionality, it takes a lot of steps and labor to apply a uniform resin coating on the entire surface of the object to be processed, especially for a deformed magnet with a complicated shape. It is difficult to apply the above coating, and the dipping method causes the resin coating to have an uneven thickness, resulting in poor product dimensional accuracy.

An object of the present invention is to provide a permanent magnet mainly composed of rare earth, boron and iron, which has improved corrosion resistance of a new permanent magnet mainly composed of rare earth, boron and iron. It is an object of the present invention to provide a manufacturing method capable of providing a corrosion-resistant resin layer having a uniform thickness.

[0008]

The present invention is based on R (provided that R
Is at least one of rare earth elements including Y) 8 atomic%
.About.30 atomic%, B2 atomic% to 28 atomic%, Fe42 atomic% to 90 atomic% as the main components, and the main phase is a tetragonal phase on the surface of the permanent magnet body, the corrosion resistant chemical conversion coating and the corrosion resistant resin layer formed by electrodeposition coating. It is a permanent magnet characterized by being sequentially laminated and coated.

Further, according to the present invention, after the above-mentioned permanent magnet body having a tetragonal phase as a main phase is subjected to a chemical conversion treatment, the permanent magnet body is immersed in an aqueous coating material to make the permanent magnet body an anode or a cathode. As a result, a permanent magnet excellent in corrosion resistance is characterized in that a direct current is supplied between it and the counter electrode, the entire permanent magnet body is electrically coated, and a corrosion-resistant chemical conversion coating and a corrosion-resistant resin layer are sequentially laminated on the surface. Is a manufacturing method.

The present invention is characterized in that a corrosion-resistant chemical conversion coating and a corrosion-resistant resin layer are sequentially laminated on the surface of the Fe-BR type permanent magnet body, and the permanent coating is applied before the resin layer is deposited by the electrodeposition coating method. The surface of the magnet body is subjected to chemical conversion treatment as a base treatment.

The underlying chemical conversion coating is preferably a phosphate coating such as zinc phosphate or manganese phosphate and / or a chromate coating, and the thickness of the chemical conversion coating is preferably from the viewpoint of corrosion resistance, strength and cost in the case of a phosphate coating. 3 μm to 10 μ
The thickness is preferably 5 μm or less in the case of chromate.

The method of forming the corrosion-resistant resin layer on the surface of the magnet body according to the present invention is such that the permanent magnet body is immersed in a water-based paint to use the permanent magnet body as an anode or a cathode, and between the permanent magnet body and the counter electrode. This is an electrodeposition coating method in which a direct current is supplied and the entire permanent magnet body is electrically coated to form a corrosion-resistant resin layer on the surface. A cation electrodeposition coating method using a magnet as a cathode can be adopted.

The resin used for the above-mentioned anionic electrodeposition coating is a polycarboxylic acid resin having a core of a drying oil, polyester, polybutadiene, epoxy ester, polyacrylic acid ester, etc., and is usually an organic amine or caustic potash. It is neutralized with the base and is made into an aqueous solution or dispersed in water to become negatively charged.

The resin used for the cationic electrodeposition coating is a polyamino resin having an epoxy resin, an acrylic resin or the like as the nucleus, which is usually neutralized with an organic acid and made into an aqueous solution or water dispersion. It is positively charged.

In the present invention, the thickness of the corrosion resistant resin layer obtained by electrodeposition coating on the surface of the permanent magnet is 5 μm.
A thickness of -30 μm is preferred. It should be noted that the total thickness of the coating and the ratio of the thicknesses of the respective layers in combination with the thickness of the underlying chemical conversion coating may be appropriately selected depending on the required corrosion resistance and the intended use of the permanent magnet so as not to create an unnecessary magnetic gap.

Further, for the purpose of preventing rust and improving coating film reinforcement, the above resin may contain a rust preventive pigment such as zinc oxide, zinc chromate, strontium chromate and red lead, or benzo. It may contain triazole.

In the present invention, the above pigment contained in the resin may be 80% or less with respect to the resin amount, and the benzotriazole amount may be 5% or less with respect to the resin amount.

The permanent magnet alloy of the present invention is characterized by containing a nonmagnetic phase (excluding oxide phase) of 1% to 50% by volume, and in the case of a sintered magnet, the crystal grain size is Is 1 to 1
The main phase is a compound having a tetragonal crystal structure in the range of 00 μm.

Therefore, the permanent magnet of the present invention uses mainly Rd, which is a resource rich abundant light rare earth as R, and Fe, B and R as main components,
An excellent permanent magnet having an extremely high energy product equal to or higher than MGOe, a high residual magnetic flux density, a high coercive force, and high corrosion resistance can be obtained at low cost.

Reasons for limiting the permanent magnet The rare earth element R used in the permanent magnet of the present invention contains 8 atom% to 30 atom% of Nd,
At least one of Pr, Dy, Ho, Tb, or further La, Ce, Gd, Er, Eu, Pm, T
Those containing at least one of m, Sm, Lu, Yb and Y are preferable. Usually, one of R is sufficient, but in practice, a mixture of two or more kinds (Misch metal, didymium, etc.) can be used for reasons such as availability. It should be noted that this R does not have to be a pure rare earth element, and may contain an impurity that is unavoidable in manufacturing within the industrially available range.

R (at least one of rare earth elements including Y) is an essential element in the novel permanent magnet, and if it is less than 8 atom%, it has a cubic crystal structure having the same crystal structure as α-iron. Therefore, high magnetic characteristics, especially high coercive force cannot be obtained. When it exceeds 30 atomic%, the R-rich nonmagnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics is obtained. I can't. Therefore, R is 8 atom% to 3
The range is 0 atomic%.

B is an essential element in the novel permanent magnet, and if it is less than 2 atomic%, a rhombohedral structure is formed and a high coercive force (iHc) cannot be obtained. Increased magnetic phase, residual magnetic flux density (Br)
, The excellent permanent magnet cannot be obtained. Therefore, B is in the range of 2 at% to 28 at%.

Fe is an essential element in the new permanent magnets of the above-mentioned series, and if it is less than 42 atomic%, the residual magnetic flux density (B
Since r) decreases and a high coercive force cannot be obtained if it exceeds 90 atom%, Fe is contained in the range of 42 atom% to 90 atom%.

In the permanent magnet alloy according to the present invention, substituting a part of Fe with Co can improve the temperature characteristics without deteriorating the magnetic characteristics of the obtained magnet. If the amount exceeds 50% of Fe, the magnetic properties are deteriorated, which is not preferable.

The permanent magnet according to the present invention is made of Fe,
In addition to B and R, the presence of impurities that are unavoidable in industrial production can be tolerated, but a part of B is 4.0 atomic% or less C, 3.5 atomic% or less P, 2.5 atomic% or less. S, at least one of 3.5 at% or less of Cu, and a total amount of 4.0 at%
By substituting the following, it is possible to improve the manufacturability of the permanent magnet and reduce the cost.

At least one of the following additive elements is added to the Fe-BR permanent magnet because it is effective in improving the coercive force and the like, improving the manufacturability, and lowering the cost. However, since the residual magnetic flux density (Br) is lowered with the addition for improving the coercive force, it is preferable to add the residual magnetic flux density in the range equal to or more than the residual magnetic flux density of the conventional hard ferrite magnet.

9.5 atom% or less of Al, 4.5 atom% or less of Ti, 9.5 atom% or less of V, 8.5 atom% or less of Cr, 8.0 atom% or less of Mn, 5 atom % Or less Bi,
12.5 atomic% or less Nb, 10.5 atomic% or less T
a, Mo at 9.5 atomic% or less, W at 9.5 atomic% or less,
2.5 atomic% or less Sb, 7 atomic% or less Ge, 3.5
At least one of Sn at 5 atomic% or less, Zr at 5.5 atomic% or less, and Hf at 5.5 atomic% or less is added. However, when two or more are contained, the maximum content is the addition element concerned. Among them, the content of the maximum value is contained in an atomic% or less, so that the permanent magnet can have a high coercive force.

It is essential that the main phase of the crystal phase is a tetragonal crystal, and it is effective for producing a sintered permanent magnet having excellent magnetic properties.

The permanent magnet of the present invention can be magnetically anisotropic magnetized by press molding in a magnetic field, or magnetically isotropic magnet by press molding in a non-magnetic field. You can

The permanent magnet according to the present invention has a coercive force iHc.
≧ 1 kOe, residual magnetic flux density Br> 4 kG, and the maximum energy product (BH) max is equal to or higher than that of hard ferrite. In the most preferable composition range, (BH) ma
x ≧ 10 MGOe, and the maximum value reaches 25 MGOe or more.

When the main component of R in the permanent magnet alloy of the present invention is 50% or more of the light rare earth metal, R
12 atom% to 20 atom%, B4 atom% to 24 atom%, F
When the main component is 65 atomic% to 82 atomic%, it exhibits the best magnetic characteristics in the case of a sintered magnet. Especially, when the light rare earth metal is Nd, the maximum value of (BH) max is 35 MGOe. Reach above

[0032]

According to the present invention, in order to suppress oxides formed on the surface of the Fe-BR permanent magnet body, a corrosion-resistant chemical conversion coating and a corrosion-resistant resin layer formed by electrodeposition coating are sequentially laminated to form a film on the surface. A strong and stable corrosion-resistant resin layer having a uniform thickness can be formed, oxidation of the surface of the magnet system of the present system is suppressed, magnetic properties are not deteriorated, and there is an advantage of being stable for a long period of time.

[0033]

Example 1 As a starting material, electrolytic iron having a purity of 99.9%, B19.4
%, And the balance is Fe and Al, Si, C and other ferroboron alloys, Nd with a purity of 99.7% or more is used, and these are high-frequency melted, and then cast in a water-cooled copper mold to obtain 15Nd8B77Fe (atoms). %) Was obtained.

Thereafter, the ingot was roughly crushed by a stamp mill and then crushed by a ball mill to obtain a fine powder having a particle size of 3 μm. Insert this fine powder into the mold and press at 12 kOe
Was oriented in a magnetic field of, and molded at a pressure of 1.5 t / cm ² . The obtained molded body is sintered at 1100 ° C. for 1 hour in Ar, then allowed to cool, and then 600 ° C. in Ar.
An aging treatment was performed at 2 ° C. for 2 hours to produce a permanent magnet.

From the obtained permanent magnet, a test piece was cut into a size of 20 mm outer diameter × 10 mm inner diameter × 1.5 mm thickness.
Next, after degreasing the test piece with trichlene, zinc 4.6
g / l, phosphate solution of 17.8 g / l of phosphate radical, 75
Immersion treatment was carried out at 3 ° C. for 3 minutes to form an underlying conversion coating.

Further, as a cationic electrodeposition paint, epoxy-based Svia CED, S-20 (manufactured by Shinto Paint Co., Ltd.)
Was used as a cathode, and the SUS316 material plate was used as an anode, and electrodeposition coating was performed under the conditions of a temperature of 28 ° C., a voltage of 150 V, and 3 minutes. Then, after being washed with water and air-dried, it was kept at 180 ° C. for 30 minutes to prepare a permanent magnet sample piece according to the present invention having a surface coated with a chemical conversion film and a resin layer.

The test piece was subjected to a corrosion resistance test and a resin layer adhesion strength test after the corrosion resistance test. In addition, the coating layer thickness and the magnetic characteristics before and after the corrosion resistance test were measured. The test results and measurement results are shown in Table 1.

The corrosion resistance test was evaluated by the appearance of the test piece when the test piece was left in an atmosphere at a temperature of 80 ° C. and a humidity of 90% for 200 hours. For the adhesion strength test, the above-mentioned test piece after the corrosion resistance test is 1 m with an adhesive tape.
The mesh portion at intervals of m was pulled, and whether or not the resin layer was peeled off was evaluated (number of unpeeled cells / total number of cells).

COMPARATIVE EXAMPLE 1 For comparison, a test piece of Example 1 having no chemical conversion coating was sprayed with an epoxy-based paint by a spray method, and 2
The coating was divided into several times and further dried at 80 ° C. for 1 hour to obtain a comparative test piece having a coating film by the spray method on the surface. This comparative test piece was subjected to the same tests and measurements as in Example 1 above, and the results are also shown in Table 1.
Table 1 shows the case of 60 ° C. because rust generation is large when the temperature in the corrosion resistance test is 80 ° C.

Comparative Example 2 For comparison, a permanent magnet sample piece having an electrodeposition coating resin layer on the surface was prepared in exactly the same manner as the test piece of Example 1 except that the underlying conversion coating was not provided. . This comparative test piece was subjected to the same tests and measurements as in Example 1 above, and the results are also shown in Table 1. When the temperature in the corrosion resistance test was 60 ° C., both the test pieces of Example 1 and Comparative Example 2 showed excellent corrosion resistance and there was no difference.

Example 2 As a starting material, electrolytic iron having a purity of 99.9%, electrolytic cobalt, B19.4% were contained, and the balance was Fe and Al, Si,
Ferroboron alloy consisting of impurities such as C, purity 99.7
% Nd is used, these are high-frequency melted, then cast in a water-cooled copper mold, and 16Nd7B10Co67Fe
An ingot having a composition of (atomic%) was obtained.

Thereafter, the ingot was roughly crushed by a stamp mill and then crushed by a ball mill to obtain a fine powder having a particle size of 3 μm. Insert this fine powder into the mold and press at 12 kOe
Was oriented in a magnetic field of, and molded at a pressure of 1.5 t / cm ² . The obtained molded body is sintered at 1100 ° C. for 1 hour in Ar, then allowed to cool, and then 600 ° C. in Ar.
An aging treatment was performed at 2 ° C. for 2 hours to produce a permanent magnet.

From the obtained permanent magnet, a test piece was cut into a size of 20 mm outer diameter × 10 mm inner diameter × 1.5 mm thickness.
Next, after degreasing the test piece with trichlene, zinc 4.6
g / l, phosphate solution of 17.8 g / l of phosphate radical, 75
Immersion treatment was carried out at 3 ° C. for 3 minutes to form an underlying conversion coating.

As the anion electrodeposition paint, acrylic Svia ED, 108-U (manufactured by Shinto Paint Co., Ltd.) was used, the above test piece degreased with trichlene was used as the anode, and the SUS316 material plate was used as the cathode. Temperature 28 ℃, voltage 2
Electrodeposition was applied under the conditions of 30 V and 2 minutes. Then, after being washed with water and air-dried, it was kept at 180 ° C. for 30 minutes to prepare a permanent magnet sample piece according to the present invention having a surface coated with a chemical conversion film and a resin layer.

The test piece was subjected to the corrosion resistance test of the same method as in Example 1 and the adhesion strength test of the resin layer after the corrosion resistance test.
In addition, the coating layer thickness and the magnetic characteristics before and after the corrosion resistance test were measured. The test results and measurement results are shown in Table 1.

Comparative Example 3 For comparison, a permanent magnet sample piece having an electrodeposition coating resin layer on the surface was prepared in exactly the same manner as the test piece of Example 2 except that the underlying conversion coating was not provided. . This comparative test piece was subjected to the same tests and measurements as in Example 1 above, and the results are also shown in Table 1.

Example 3 As a starting material, electrolytic iron having a purity of 99.9%, B19.4
% And the balance is Fe and Al, Si, a ferroboron alloy consisting of impurities such as C, Nd and Dy metals with a purity of 99.7% or more are used, and these are high-frequency melted, then cast in a water-cooled copper mold, 15Nd1.5Dy8B75.5F
An ingot having a composition of e (atomic%) was obtained.

Thereafter, the ingot was roughly crushed by a stamp mill and then crushed by a ball mill to obtain a fine powder having a particle size of 3 μm. Insert this fine powder into the mold and press at 12 kOe
Was oriented in a magnetic field of, and molded at a pressure of 1.5 t / cm ² . The obtained molded body is sintered at 1100 ° C. for 1 hour in Ar, then allowed to cool, and then 600 ° C. in Ar.
An aging treatment was performed at 2 ° C. for 2 hours to produce a permanent magnet.

From the obtained permanent magnet, a test piece was cut into a size of 20 mm outer diameter × 10 mm inner diameter × 1.5 mm thickness.
Next, after degreasing the test piece with trichlene, zinc 4.6
g / l, phosphate solution of 17.8 g / l of phosphate radical, 75
Immersion treatment was performed at ℃ for 3 minutes.

Epoxy Svia CED, S-20 (manufactured by Shinto Paint Co., Ltd.) was used as the cationic electrodeposition paint, the above test piece was used as the cathode, the SUS316 material plate was used as the anode, and the temperature was 28 ° C. and the voltage was 150 V. Electrodeposition was applied under the condition of 3 minutes. Then, after washing with water and air-drying, it was kept at 180 ° C. for 30 minutes to prepare a permanent magnet sample piece according to the present invention having a surface coated with a resin layer.

The test piece was subjected to a corrosion resistance test and a resin layer adhesion strength test after the corrosion resistance test. In addition, the coating layer thickness and the magnetic characteristics before and after the corrosion resistance test were measured. The test results and measurement results are shown in Table 1.

Comparative Example 4 For comparison, a permanent magnet sample piece having an electrodeposition coating resin layer on the surface was prepared in exactly the same manner as the test piece of Example 3 except that the underlying conversion coating was not provided. . This comparative test piece was subjected to the same tests and measurements as in Example 1 above, and the results are also shown in Table 1.

[0053]

[Table 1]

[0054]

As is apparent from the test and measurement results in Table 1, the permanent magnet of the present invention in which a chemical conversion coating and a resin layer formed by electrodeposition coating are sequentially laminated and coated is a resin layer formed by spray coating or a resin formed by electrodeposition coating. Compared to the comparative example consisting of only layers, the required film thickness and excellent uniformity were obtained, and the corrosion resistance was markedly improved, so oxidation of the permanent magnet surface was reliably prevented, It has excellent properties and is stable for a long period without deterioration of magnetic properties.

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Claims (2)

[Claims] 1. R (where R is at least one of rare earth elements including Y) 8 atom% to 30 atom%, B2 atom% to
It is characterized in that a corrosion-resistant chemical conversion coating and a corrosion-resistant resin layer formed by electrodeposition coating are sequentially laminated on the surface of a permanent magnet body containing 28 atom% and 42 atom% to 90 atom% of Fe as main components and a tetragonal phase as a main phase. Permanent magnet with excellent corrosion resistance. 2. R (where R is at least one of rare earth elements including Y) 8 atom% to 30 atom%, B2 atom% to
After a chemical conversion treatment is applied to a permanent magnet body containing 28 atom% and 42 atom% to 90 atom% of Fe as a main component and a tetragonal phase as a main phase, the permanent magnet body is dipped in an aqueous paint to form the permanent magnet. A body is used as an anode or a cathode, and a direct current is supplied between it and the counter electrode, the entire permanent magnet body is electrically coated, and a corrosion-resistant chemical conversion coating and a corrosion-resistant resin layer are sequentially laminated and coated on the surface. Excellent permanent magnet manufacturing method.