JPH07249509A - Corrosion-resistant permanent magnet and its manufacture - Google Patents

Abstract

PURPOSE:To improve corrosion resistance of an Fe-B-R permanent magnet by providing a TiN film on the surface of the magnet with an Al film in between. CONSTITUTION:A corrosion-resistant permanent magnet is composed of an Fe-B-R permanent magnet body having a main phase constituted of a tetragonal phase, Al film formed on the surface of the magnet body 0.06-5.0mum thick, and TiN film formed on the Al film 0.5-10mum thick and, in the manufacturing method of the permanent magnet, the Al film is formed by a vapor phase film forming method after cleaning the surface of the magnet body and the TiN film is formed by a vapor-phase film forming method in an N2 gas atmosphere. Therefore, an Fe-B-R permanent magnet having stable high magnetic characteristics, a wear resistance, and a corrosion resistance can be obtained at low cost, because the permanent magnet is coated with an Al and TiN films having excellent adhesibility to the substrate of the magnet with the object of improving the wear resistance and corrosion resistance of the magnet, especially, reducing the initial magnetic characteristics of the magnet when the magnet is left under an atmospheric condition of 80 deg.C in temperature and 90% in relative humidity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Fe-B-R permanent magnet provided with a corrosion resistant coating having high magnetic properties, excellent adhesion, and excellent corrosion resistance, acid resistance, alkali resistance and wear resistance. In this regard, the corrosion resistance of the TiN coating layer having a specific thickness provided through the Al coating, especially the stable magnet characteristics with little deterioration from the initial magnet characteristics when left in an atmosphere of 80 ° C. and 90% relative humidity for a long time. And a method of manufacturing the same.

[0002]

2. Description of the Related Art First, a light rare earth which is rich in resources centering on Nd and Pr is used as a main component of B and Fe, and does not contain expensive Sm or Co. As a new high-performance permanent magnet that greatly exceeds the characteristics, F
An e-B-R permanent magnet has been proposed (JP-A-59-59).
46008, JP-A-59-89401).

The Curie point of the magnet alloy is generally 30.
It is 0 ° C to 370 ° C, but Fe-B- having a higher Curie point by substituting a part of Fe with Co.
R-based permanent magnet (JP-A-59-64733, JP-A-59)
-132104), and further has a Curie point equal to or higher than that of the Fe-BR rare earth permanent magnet containing Co and a higher (BH) max, and improves its temperature characteristics, particularly iHc. Therefore, Co-containing F mainly composed of light rare earth elements such as Nd and Pr as rare earth elements (R)
By containing at least one kind of heavy rare earths such as Dy and Tb in a part of R of the e-B-R rare earth permanent magnet, iHc can be maintained while maintaining extremely high (BH) max of 25 MGOe or more. Further improved Co-containing F
Proposed e-BR rare earth permanent magnet (Japanese Patent Laid-Open No. 60-34)
No. 005).

However, since the permanent magnet made of the Fe-BR type magnetic anisotropic sintered body having the above-mentioned excellent magnetic characteristics contains iron as a main component, a rare earth element and iron which are easily oxidized in air, When incorporated into a magnetic circuit, the oxide generated on the surface of the magnet causes a decrease in the output of the magnetic circuit and variations among the magnetic circuits, and there is a problem of contamination of peripheral equipment due to the loss of the surface oxide. It was

[0005]

Therefore, the above Fe-
In order to improve the corrosion resistance of the B-R permanent magnet, there has been proposed a permanent magnet (Japanese Patent Publication No. 3-74012) in which the surface of the magnet is coated with a corrosion-resistant metal plating layer by electroless plating or electrolytic plating. In this plating method, since the permanent magnet body is a sintered body and has porosity, the acidic solution or alkaline solution in the pretreatment of plating may remain in this hole, and there is a risk of corrosion over time. Since the chemical resistance is poor, the surface of the magnet is corroded during plating, resulting in poor adhesion and corrosion resistance. Moreover, even if corrosion resistant plating is provided,
1 in the corrosion resistance test under the conditions of temperature 60 ℃ and relative humidity 90%
When left standing for 00 hours, the magnet characteristics deteriorated by 10% or more of the initial magnet characteristics and were very unstable.

Therefore, in order to improve the corrosion resistance of the Fe-BR type permanent magnet, TiN and T are formed on the surface of the magnet by an ion plating method, an ion sputtering method or the like.
It has been proposed (Japanese Patent Publication No. 5-15043) to apply an i-coat to improve the corrosion resistance. However, Ti
The N-coating has poor adhesion because it has a different thermal expansion coefficient, ductility, etc. from the Fe-BR magnet, and the Ti coating has good adhesion and corrosion resistance, but low wear resistance. Therefore, it has been proposed (Japanese Patent Laid-Open No. 63-9919) to apply a laminated coating film of Ti and TiN on the surface of the Fe-BR type permanent magnet body. However, since the Ti coating and the TiN coating have different crystal structures, coefficients of thermal expansion, ductility, and the like, there is a problem in that the adhesion is poor, peeling occurs, and the corrosion resistance decreases.

The present invention has excellent adhesion to a Fe-BR system permanent magnet substrate, and has the purpose of improving abrasion resistance and corrosion resistance, and especially for a long time under an atmospheric condition of a temperature of 80 ° C. and a relative humidity of 90%. It is an object of the present invention to provide a Fe-BR permanent magnet having stable high magnet characteristics, abrasion resistance, and corrosion resistance at a low cost by minimizing deterioration from the initial magnet characteristics when left standing for a long time.

[0008]

Means for Solving the Problems The inventors of the present invention have excellent corrosion resistance, and in particular, even when left for a long time under an atmospheric condition of a temperature of 80 ° C. and a relative humidity of 90%, the adhesiveness to a substrate is excellent and the adhesion is excellent. Due to the corrosion resistance and wear resistance of the corrosion-resistant metal coating, various examinations were conducted on the method of forming a TiN coating on the surface of the permanent magnet body for the purpose of producing a Fe-BR permanent magnet having stable magnet characteristics. After cleaning by a sputter method or the like, an Al coating film having a specific film thickness is formed on the surface of the magnet body by a vapor phase film forming method such as an ion plating method or an ion sputtering method, and then N ₂ gas under a specific condition is introduced. By forming a TiN film with a specific layer thickness by a vapor phase film forming method such as ion plating, ion sputtering, etc., the oxide adhered to the magnet surface is deoxidized by the Al film. Ri, oxides of the magnet surface part or majority is reduced, adhesion between the magnet and the Al coating is significantly improved, Although mechanisms, or the like is unknown, Al coating and T
It was found that the adhesion with the iN coating can be significantly improved and
Completed this invention.

That is, according to the present invention, a film thickness of 0.06 μm is formed on the surface of the Fe-BR permanent magnet body whose main phase is a tetragonal phase.
with a thickness of 0.5 μm to 1 through an Al coating of m to 5.0 μm
A corrosion resistant permanent magnet having a TiN coating layer of 0 μm.

Further, according to the present invention, after cleaning the surface of the Fe-BR type permanent magnet body whose main phase is a tetragonal phase, an Al coating having a film thickness of 0.06 μm to 5.0 μm is formed on the surface of the magnet body. A method for producing a corrosion-resistant permanent magnet, characterized in that a TiN coating layer having a film thickness of 0.5 μm to 10 μm is formed by a vapor phase film forming method in an N ₂ gas atmosphere after forming by a phase film forming method.

In the present invention, as a method for forming the Al coating film and the TiN coating film to be deposited on the surface of the Fe-BR type permanent magnet body, there are so-called vapor phase film forming methods such as ion plating method, ion sputtering method and vapor deposition method. Ion plating and reactive ion plating are preferably used because of their compactness, uniformity, and film formation rate. In addition, the temperature of the permanent magnet serving as the substrate when the reaction film is formed is preferably set to 200 ° C to 500 ° C.
If the temperature is less than ℃, the reaction adhesion with the substrate magnet is insufficient, and
If the temperature exceeds 00 ° C, the temperature difference from room temperature (25 ° C) becomes large, cracks occur in the coating film during the cooling process after the treatment, and peeling occurs partly from the substrate. Therefore, the temperature of the substrate magnet is 200 ° C to 5 ° C.
It is recommended to set it to 00 ° C.

An example of the method for producing the corrosion-resistant permanent magnet of the present invention, which is characterized in that the TiN coating layer is provided on the surface of the Fe-BR permanent magnet body via the Al coating layer, will be described in detail below. 1) Using an arc ion plating device, the vacuum container was evacuated to a vacuum degree of 1 × 10 ⁻³ pa or less, and then Fe—B— by surface sputtering with Ar ions at an Ar gas pressure of 10 pa and −500 V. Clean the surface of the R-type magnet body. 2) Next, Ar gas pressure 0.1 pa, bias voltage -50
V is used to evaporate the Al of the target, and 0.06 μm to the surface of the magnet body by the arc ion plating method.
An Al coating layer having a thickness of 5.0 μm is formed. 3) Subsequently, Ti was used as a target, the magnet temperature of the substrate was kept at 250 ° C., and under conditions of N ₂ gas pressure of 1 pa, bias voltage of −100 V, and arc current of 100 A, Al was used.
A TiN coating layer having a specific thickness is formed on the coating layer.

In the present invention, the reason why the Al film thickness on the surface of the Fe-BR permanent magnet body is limited to 0.06 μm to 5.0 μm is that the Al film thickness on the surface of the magnet body is less than 0.06 μm.
Is difficult to be deposited uniformly, the effect as a base film is not sufficient, and if it exceeds 5.0 μm, there is no problem effectively, but as a base film, it causes a cost increase and is not preferable because it is not practical. , Al film thickness is 0.06 μm to 5.0 μm. In particular, the Al film thickness is selected according to the surface roughness of the magnet body. When the surface roughness is 0.1 μm or less, the Al film thickness is preferably 0.06 μm to 5.0 μm, and the surface roughness is 0.1 μm to In the case of 1.2 μm, the desired film thickness is 0.1
It is 1 μm to 5.0 μm.

The TiN film thickness is 0.5 μm to 10 μm.
The reason for limiting to m is less than 0.5 μm, the corrosion resistance and wear resistance as TiN are not sufficient, and if it exceeds 10 μm, there is no problem effectively, but it is not preferable because it causes an increase in manufacturing cost.

In the present invention, the rare earth element R used in the permanent magnet occupies 10 atom% to 30 atom% of the composition, and at least one of Nd, Pr, Dy, Ho and Tb is used.
Seed, or even La, Ce, Sm, Gd, Er,
Those containing at least one of Eu, Tm, Yb, Lu and Y are preferable. Usually, one kind of R is sufficient, but in practice, a mixture of two or more kinds (Misch metal,
Zijim, etc.) can be used for reasons of availability. Incidentally, this R does not have to be a pure rare earth element,
It does not matter even if it contains impurities that are unavoidable in manufacturing within the industrially available range. R is an essential element in the above-mentioned permanent magnet, and if less than 10 atomic%, the crystal structure is α-.
Since it has a cubic structure with the same structure as iron, high magnetic properties, especially high coercive force, cannot be obtained. If it exceeds 30 atomic%, the R-rich nonmagnetic phase increases and the residual magnetic flux density (Br) decreases. A permanent magnet with excellent characteristics cannot be obtained. Therefore, R1
The range of 0 atom% to 30 atom% is desirable.

B is an essential element in the above-mentioned permanent magnet. When it is less than 2 atomic%, the rhombohedral structure becomes the main phase and a high coercive force (iHc) cannot be obtained. When it exceeds 28 atomic%, B is rich. Non-magnetic phase increases and residual magnetic flux density (Br)
, The excellent permanent magnet cannot be obtained. Therefore, B is preferably in the range of 2 atom% to 28 atom%.

Fe is an essential element in the above-mentioned permanent magnets. If it is less than 65 atom%, the residual magnetic flux density (Br) is lowered, and if it exceeds 80 atom%, a high coercive force cannot be obtained. % To 80 atomic% is desirable.
Further, substituting a part of Fe with Co can improve the temperature characteristics without deteriorating the magnetic characteristics of the obtained magnet. However, when the Co substitution amount exceeds 20% of Fe, it is contrary. It is not preferable because the magnetic properties deteriorate. When the substitution amount of Co is 5 at% to 15 at% in terms of the total amount of Fe and Co, Br is increased as compared with the case where no substitution is made, which is preferable for obtaining a high magnetic flux density.

In addition to R, B and Fe, the presence of impurities inevitable in industrial production can be tolerated. For example, a part of B is 4.0 wt% or less of C, 2.0 wt% or less of P, 2 .0
By substituting at least one of S of 2.0 wt% or less and Cu of 2.0 wt% or less with a total amount of 2.0 wt% or less, it is possible to improve the manufacturability of the permanent magnet and reduce the cost.
Furthermore, Al, Ti, V, Cr, Mn, Bi, Nb, T
a, Mo, W, Sb, Ge, Sn, Zr, Ni, Si,
At least one of Zn and Hf is effective for improving the coercive force and squareness of the demagnetization curve, improving the manufacturability, and lowering the price of the Fe—BR permanent magnet material. It can be added. Note that the upper limit of the addition amount is B in order to make the (BH) max of the magnet material 20 MGOe or more.
Since r is required to be at least 9 kG or more, a range satisfying the condition is desirable.

Further, the Fe-BR type permanent magnet has a compound having a tetragonal crystal structure having an average crystal grain size in the range of 1 to 80 μm as a main phase and a volume ratio of 1% to 50% of a non-crystal. It is characterized by containing a magnetic phase (excluding an oxide phase). Fe
The −BR permanent magnet exhibits a coercive force iHc ≧ 1 kOe, a residual magnetic flux density Br> 4 kG, and a maximum energy product (B
H) max indicates (BH) max ≧ 10 MGOe,
The maximum value reaches 25 MGOe or more.

[0020]

According to the present invention, after the surface of the Fe-BR type permanent magnet body is cleaned by the ion sputtering method or the like, the surface of the magnet body is formed by the vapor deposition method such as the ion plating method.
After forming the l coating, the TiN coating is formed by a vapor phase film forming method such as ion plating while introducing N ₂ gas under a specific condition. The magnet is formed by forming the Al coating on the surface of the magnet body. Part or most of the oxide on the body surface is reduced, the adhesion between the magnet body surface and the Al coating is improved, and the adhesion of the TiN coating is further improved by laminating a TiN coating on the Al coating. Excellent corrosion resistance, especially when left for a long time under an atmospheric condition of a temperature of 80 ° C. and a relative humidity of 90%, the adhesiveness with the base is excellent, and the corrosion resistance and abrasion resistance of the adhered corrosion resistant metal coating An Fe-BR type permanent magnet having stable magnet characteristics can be obtained.

[0021]

【Example】

Example 1 A known casting ingot was crushed, finely crushed, and then molded, sintered, heat-treated, and surface-treated, and then 16Nd-77Fe-7B.
A magnet test piece having a composition of a diameter of 12 mm and a thickness of 2 mm was obtained. Table 2 shows the surface roughness of the obtained test piece, and Table 1 shows the magnet characteristics. The inside of the vacuum vessel was evacuated to 1 × 10 ⁻³ pa or less, and surface sputtering was performed at Ar gas pressure of 10 pa and −500 V for 20 minutes to clean the surface of the magnet body, and then Table 2
Set the substrate magnet temperature to 2 under the ion plating conditions shown in
The temperature is set to 50 ° C. and 0.1 μ is applied to the surface of the magnet body by arc ion plating method using metallic Al as a target.
An Al coating layer having a thickness of m and a thickness of 1.8 μm was formed. Next, a substrate magnet temperature of 350 ° C., a bias voltage of −100 V, an arc current of 100 A, N ₂ gas of 1 pa, and metal Ti as a target by an arc ion plating method for 3 hours on the Al film surface in a thickness of 3 μm TiN film. Layers were formed. Then, after allowing to cool, the permanent magnet having the obtained TiN coating on the surface was placed under the conditions of a temperature of 80 ° C. and a relative humidity of 90%.
The magnet characteristics and its deterioration state after standing for 000 hours were measured, and the results are shown in Table 3.

Comparative Example 1 A magnet body test piece having the same composition as in Example 1 was surface-cleaned under the same conditions as in Example 1, and then a TiN film was formed on the magnet body to a thickness of 3 μm under the same conditions as in Example 1. Formed. Then, under the same temperature of 80 ° C. and relative humidity of 90% as in Example 1, 1
The magnet characteristics and its deterioration state after standing for 000 hours were measured, and the results are shown in Table 3.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

As shown in Table 3, the comparative magnet having the TiN coating layer on the surface of the Fe-BR permanent magnet having the same magnet characteristics was 1000 at a temperature of 80 ° C and a relative humidity of 90%. While the deterioration of the magnet characteristics before and after the corrosion resistance test after being left for a long time is large and rusting occurs, the Fe-BR type permanent magnet of the present invention in which the TiN coating layer is provided through the Al coating layer does not rust. It is clear that the magnet characteristics do not occur and the magnet characteristics hardly change.

[0027]

The Fe-BR type permanent magnet body according to the present invention, in which the TiN coating layer is formed on the surface of the magnet through the Al coating, is subjected to severe corrosion resistance test conditions, especially at a temperature of 8
After being left for 1000 hours under conditions of 0 ° C. and 90% relative humidity, there is almost no deterioration in the magnet characteristics, and it is extremely suitable as a high-performance and inexpensive permanent magnet most demanded at present.

Claims (2)

[Claims] 1. A film having a thickness of 0.06 .mu.m to 5.0 .mu.m is formed on the surface of a Fe-BR permanent magnet whose main phase is a tetragonal phase.
A corrosion-resistant permanent magnet having a TiN coating layer having a film thickness of 0.5 μm to 10 μm through a coating film. 2. After cleaning the surface of the Fe—B—R permanent magnet body whose main phase is a tetragonal phase, an Al film having a film thickness of 0.06 μm to 5.0 μm is formed on the surface of the magnet body in a vapor phase. A method for producing a corrosion-resistant permanent magnet, comprising forming a TiN coating layer having a film thickness of 0.5 μm to 10 μm by a vapor deposition method in an N ₂ gas atmosphere after the formation by the method.