JPH06349619A - Corrosion-resistant permanent magnet and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve an adhesiveness of a Ti film to a TiN film layer by a method wherein the TiN film layer is provided on the Ti film provided on the surface of an Fe-B-Ra permanent magnet body via a nitrogen diffused layer, in which an N2 concentration is continuously increased. CONSTITUTION:A corrosin-resistant permanent magnet is formed into a structure, wherein a TiN film layer of a film thickness of 0.5 to 10mum is formed on the surface of an Fe-B-Ra permanent magnet body having its main phase consisting of a tetragonal phase via a Ti film of a film thickness of 0.1 to 30mum and an N diffused layer (a composition consisting of TiNx), in which an N2, concentration is continuously increased from the side of the magnet body toward the TiN film layer and which has a film thickness of 0.05 to 2.0mum, is provided in the surface of this Ti film. A method of manufacturing this permanent magnet is performed by a method wherein the surface of the permanent magnet body is cleaned and thereafter, the Ti film is formed on the surface of the magnet body, then, the mixed gas of Ar gas and N2, gas is introduced in a treating container while the amount of the N2, gas is continuously increased and after the N diffused layer, in which the N2 concentration is increased, is formed in the Ti film, the TiN film layer is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Fe-B-Ra type 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 particular, the present invention relates to a corrosion-resistant permanent magnet having extremely 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 for producing 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-Ra type permanent magnet has been proposed (Japanese Patent Laid-Open No. 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.
Ra-based permanent magnet (JP-A-59-64733, JP-A-5-64733)
9-132104), and further has a Curie point equal to or higher than that of the Fe-B-Ra-based rare earth permanent magnet containing Co and a higher (BH) max, and improves its temperature characteristics, particularly iHc. In order to make the rare earth element (R
As a), a part of Ra of Co-containing Fe-B-Ra-based rare earth permanent magnets centering on light rare earths such as Nd and Pr is used as D.
By containing at least one of heavy rare earth elements such as y and Tb, extremely high (BH) m of 25 MGOe or more.
Co that has further improved iHc while holding ax
A Fe-B-Ra-based rare earth permanent magnet containing is proposed (Japanese Patent Laid-Open No. 60-34005).

However, the permanent magnet made of the Fe--B--Ra type magnetic anisotropic sintered body having the above-mentioned excellent magnetic characteristics contains iron as a main component, which is a rare earth element which is easily oxidized in air, and iron. 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-Ra type permanent magnet, a permanent magnet whose surface is coated with a corrosion-resistant metal plating layer by electroless plating or electrolytic plating (Japanese Patent Application No. 58-1623).
No. 50) has been proposed, but in this plating method, since the permanent magnet body is a sintered body and is porous, the acidic solution or alkaline solution in the plating pretreatment remains in this hole, and it corrodes with age. Since the magnet body is inferior in chemical resistance, the surface of the magnet is corroded during plating, resulting in poor adhesion and corrosion resistance. Even if corrosion resistant plating is provided, the magnet characteristics are 10 times the initial magnet characteristics when left for 100 hours in the corrosion resistance test under the conditions of a temperature of 60 ° C. and a relative humidity of 90%.
% Deteriorated and was extremely unstable.

Therefore, in order to improve the corrosion resistance of the Fe-B-Ra based permanent magnet, the surface of the magnet is coated with TiN, by an ion plating method, an ion sputtering method, or the like.
It has been proposed (Japanese Patent Laid-Open No. 61-150201) to improve the corrosion resistance by applying a Ti coating. However, the TiN coating has poor adhesion because it differs from the Fe-B-Ra-based magnet body in its crystal structure, thermal expansion coefficient, ductility, etc., and the Ti coating has good adhesion and corrosion resistance, but 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-B-Ra based 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 an Fe-B-Ra-based permanent magnet substrate, and is intended to improve abrasion resistance and corrosion resistance, and particularly to improve long-term under atmospheric conditions at a temperature of 80 ° C. and a relative humidity of 90%. An object of the present invention is to provide an Fe-B-Ra-based permanent magnet that has stable high magnet characteristics, wear resistance, and corrosion resistance at a low cost by minimizing deterioration from the initial magnet characteristics when left standing for a long time.

[0008]

The present invention has excellent corrosion resistance, and in particular, even when it is left for a long time under an atmospheric condition of a temperature of 80 ° C. and a relative humidity of 90%, it has excellent adhesion to a substrate and is adhered. Corrosion resistance Due to the corrosion resistance and wear resistance of the metal coating, various studies were conducted on the method of forming a TiN coating on the surface of the permanent magnet for the purpose of making a Fe-B-Ra-based permanent magnet with stable magnet characteristics. After cleaning by a method such as a method, a Ti film having a specific film thickness is formed on the surface of the magnet by a thin film forming method such as an ion plating method, and then a mixed gas of Ar gas and N ₂ gas under specific conditions is introduced. A thin film forming method such as ion plating is performed to form an N diffusion layer in which the N concentration increases as the specific thickness of the Ti coating surface approaches the surface, and then the ion reaction plating is performed in N ₂ gas. Thin film forming method such as coating,
It was found that the adhesion between the Ti coating and the TiN coating can be remarkably improved by forming the TiN coating having a specific layer thickness, and the present invention has been completed.

That is, according to the present invention, the film thickness of 0.1 μm is formed on the surface of the Fe—B—Ra type permanent magnet body whose main phase is a tetragonal phase.
m-3.0 μm Ti film thickness 0.5 μm-1
A TiN coating layer is formed in a thickness of 0 μm, and an N diffusion layer (composition TiNx) having a thickness of 0.05 μm to 2.0 μm in which the N ₂ concentration continuously increases from the magnet side toward the TiN coating layer is formed on the Ti coating surface. It is a corrosion-resistant permanent magnet characterized by having. Further, in the present invention, Fe whose main phase is a tetragonal phase
-After cleaning the surface of the B-Ra based permanent magnet body, a film thickness of 0.1 μm to 3.0 μm is formed on the surface of the magnet body by a thin film forming method.
After the Ti film formation, the thickness of Ar and N ₂ mixed gas into the processing vessel by introducing while continuously increasing the N ₂ volume, N ₂ concentration increases in the Ti film 0.05-2. 0 μm N
After the diffusion layer (composition TiNx) is formed, a TiN film phase having a film thickness of 0.5 μm to 10 μm is formed by a thin film forming method, which is a method for producing a corrosion-resistant permanent magnet.

A TiN coating layer is provided on the Ti coating provided on the surface of the Fe-B-Ra type permanent magnet body through a nitrogen diffusion layer (composition TiNx) in which the N ₂ concentration continuously increases. An example of the method for producing the corrosion-resistant permanent magnet will be described in detail below. For example, using an arc ion plating device, the vacuum container is evacuated to an ultimate vacuum of 1 × 10 ⁻³ pa or less, and then Ar gas pressure is 10 pa and Ar is −500 V.
The surface of the Fe-B-Ra based magnet body is cleaned by surface sputtering with ions. Next, Ti of the target is evaporated by Ar gas pressure of 0.1 pa and bias voltage of −80 V, and a Ti coating layer having a thickness of 0.1 μm to 3.0 μm is formed on the surface of the magnet body by the arc ion plating method. To do.
Then, the nitrogen diffusion layer (composition T
In order to form iNx), the temperature of the magnet of the substrate is kept at 400 ° C. while evaporating Ti, the gas pressure is 1 pa, the bias voltage is −100 V, and the arc current is 100 A.
After introducing the mixed gas of r gas and nitrogen, the amount of N ₂ in the mixed gas is increased to form a nitrogen diffusion layer having a specific thickness and an increasing N ₂ concentration toward the TiN coating layer. After that, arc ion plating is further performed with a nitrogen amount gas pressure of 1 pa to form a TiN coating film of a specific thickness on the N ₂ diffusion layer in the Ti coating layer.

In the present invention, a known thin film forming method such as an ion plating method or a vapor deposition method is appropriately selected as a method for forming the Ti coating layer and the nitrogen diffusion layer adhered to the surface of the Fe-B-Ra type permanent magnet body. However, the ion plating method and the ion reaction plating method are preferable for reasons such as the denseness of the film, the uniformity, and the film formation rate. The temperature of the substrate magnet at the time of forming the reaction film is preferably set to 200 ° C to 500 ° C. If the temperature is less than 200 ° C, the reaction adhesion with the substrate magnet is insufficient, and if it exceeds 500 ° C, the temperature is at room temperature (-25
The temperature difference between the substrate magnet and the substrate magnet is set to 200 ° C to 500 ° C.

In the present invention, the reason why the Ti film thickness on the surface of the magnet body is limited to 0.1 μm to 3.0 μm is 0.1.
If it is less than μm, the adhesion to the magnet surface is insufficient, and 3.0
If the thickness exceeds .mu.m, there is no problem in terms of effectiveness, but this causes an increase in the cost of the base film and is not practical and not preferable. Therefore, the Ti film thickness is set to 0.1 .mu.m to 3.0 .mu.m. The thickness of the nitrogen diffusion layer formed in the Ti coating layer is 0.05 μm.
The reason for limiting the thickness to 2.0 μm is that if the thickness is less than 0.05 μm, the diffusion layer is insufficient and good adhesion cannot be obtained.
If the thickness exceeds μm, there is no problem in terms of effect, but this is not preferable because it causes an increase in manufacturing cost and is not practical. In the present invention, it is preferable that the N ₂ diffusion layer in the Ti coating layer has a continuously increasing N ₂ concentration toward the TiN coating layer. Further, the reason why the TiN coating film thickness is limited to 0.5 μm to 10 μm is that the corrosion resistance and wear resistance as TiN are not sufficient when the thickness is less than 0.5 μm, and there is no problem effectively when the thickness exceeds 10 μm, but the manufacturing cost increases. Is not preferable because it invites

Rare earth element R used in the permanent magnet of the present invention
a occupies 10 atomic% to 30 atomic% of the composition, but N
At least one of d, Pr, Dy, Ho, Tb, or further La, Ce, Sm, Gd, Er, Eu,
Those containing at least one of Tm, Yb, Lu and Y are preferable. Further, although one of Ra is usually sufficient, a mixture of two or more kinds (Misch metal, didymium, etc.) can be practically used for reasons of availability. It should be noted that this Ra does not have to be a pure rare earth element, and may contain impurities that are unavoidable in manufacturing within a range that is industrially available. Ra 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 Ra-rich nonmagnetic phase increases and the residual magnetic flux density (Br) decreases. A permanent magnet with excellent characteristics cannot be obtained. Therefore, R
The range of 10 at% to 30 at% is desirable.

B is an essential element in the above-mentioned permanent magnet, and if it is less than 2 atomic%, the rhombohedral structure becomes the main phase and a high coercive force (iHc) cannot be obtained. If 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 amount of substitution 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 Ra, B, and Fe, the presence of impurities that are inevitable in industrial production can be tolerated. For example, 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 Fe-B-Ra.
It can be added to a permanent magnet material because it is effective in improving the coercive force, squareness of demagnetization curve, improving manufacturability, and reducing cost. In addition, the upper limit of the addition amount is to set (BH) max of the magnetic material to 20 MGOe or more,
Since (Br) is required to be at least 9 kG or more, a range satisfying the condition is desirable.

The permanent magnet of the present invention comprises 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 nonmagnetic phase of 1% to 50% by volume ( (Excluding an oxide phase). The permanent magnet according to the present invention exhibits a coercive force iHc ≧ 1 kOe, a residual magnetic flux density Br> 4 kG, and a maximum energy product (BH).
max indicates (BH) max ≧ 10 MGOe, and the maximum value reaches 25 MGOe or more.

[0018]

According to the present invention, after the surface of the Fe-B-Ra-based permanent magnet body is cleaned by the ion sputtering method or the like, a Ti coating film is formed on the surface of the magnet body by a thin film forming method such as the ion plating method, and then specified. performing a thin film formation method such as ion plating while introducing a mixed gas of Ar gas and N ₂ gas conditions, after the formation of the N diffusion layer sequentially N concentration on the Ti coating film surface increases, N ₂ gas A thin film forming method such as ion reaction plating was performed to form a TiN coating film. Since the TiN coating film is laminated on the Ti coating film with an N diffusion layer interposed, the adhesion between both coating films is remarkable. Improved and excellent corrosion resistance, especially even when left for a long time under an atmospheric condition of temperature 80 ° C and relative humidity 90%, it has excellent adhesion to the underlayer and has excellent corrosion resistance and wear resistance of the adhered corrosion resistant metal coating. The stable magnetic characteristics of F
An e-B-Ra system permanent magnet is obtained.

[0019]

【Example】

Example 1 A known casting ingot was crushed, finely crushed, molded, sintered, and heat-treated, and then a diameter of 1 of 16Nd-77Fe-7B composition was obtained.
A magnet test piece having a size of 2 mm and a thickness of 2 mm was obtained. The magnet characteristics are shown in Table 1. The inside of the vacuum vessel was evacuated to 1 × 10 ⁻³ pa or less, and the Ar gas pressure was 10 pa, and the pressure was −500 V for 20 seconds.
After the surface is sputtered for a minute to clean the surface of the magnet body, Ar gas pressure is 0.1 pa, bias voltage is −80 V,
A Ti coating layer having a thickness of 0.1 μm is formed on the surface of the magnet body by an arc ion plating method using metal Ti as a target with an arc current of 100 A and a substrate magnet temperature of 400 ° C. Next, the substrate magnet 400 ° C., bias voltage -100
V, arc current 100A, mixed gas 1pa of Ar: N ₂ = 9: 1 was introduced, and mixed gas ratio was Ar: N ₂ ratio 9: 1 → 7: 3 → 5: 5 → 3: 7 → 0. The composition of the mixed gas was continuously changed to 10 minutes to form a nitrogen diffusion layer (composition TiNx) having a film thickness of 0.3 μm on the surface of the Ti coating film in 30 minutes.
Further, arc ion plating was performed with N2 gas of 1 pa, bias voltage of -100 V, and arc current of 100 A to form a TiN coating film of 3 μm on the nitrogen diffusion layer in 3 hours. Then, after allowing to cool, the permanent magnet having the obtained TiN coating on the surface was allowed to stand for 1000 hours under the conditions of a temperature of 80 ° C. and a relative humidity of 90%, and the magnet characteristics and its deterioration state were measured. The results are shown in Table 2.

Comparative Example 1 A magnet test piece having the same composition as in Example 1 was surface-cleaned under the same conditions as in Example 1, and then 1.
After forming a Ti film having a thickness of 0 μm, a TiN film having a thickness of 3 μm was formed on the Ti film under the same conditions as in Example 1. Then, the magnet characteristics and its deterioration state after standing for 1000 hours under the same temperature of 80 ° C. and relative humidity of 90% as in Example 1 were measured, and the results are shown in Table 2.

[0021]

[Table 1]

[0022]

[Table 2]

As shown in Table 2, the comparative example magnet having the Ti coating and the TiN coating layer on the surface of the Fe-B-Ra type permanent magnet having the same magnet characteristics has a temperature of 80 ° C. and a relative humidity of 90.
%, The magnet characteristics were largely deteriorated before and after the corrosion resistance test after being left for 1000 hours under the conditions of 100%
The Fe-B-Ra-based permanent magnet of the present invention in which the TiN coating layer is provided on the coating through the nitrogen diffusion layer (composition TiNx) in which the N ₂ concentration continuously increases does not generate rust, and the magnet characteristics Is almost unchanged.

[0024]

According to the present invention, the Fe-B-R having the TiN coating layer provided on the surface of the magnet according to the present invention is provided with the TiN coating layer via the nitrogen diffusion layer (composition TiNx) in which the N ₂ concentration continuously increases.
The a-type permanent magnet body was subjected to severe corrosion resistance test conditions as in the example, particularly, under the conditions of a temperature of 80 ° C. and a relative humidity of 90%.
After being left for 000 hours, there is almost no deterioration in the magnet characteristics, and it is extremely suitable as the most demanded high-performance and inexpensive permanent magnet at present.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01F 1/053 7/02 Z

Claims (2)

[Claims] 1. Fe-B-Ra whose main phase is a tetragonal phase
Of a film thickness of 0.1 μm to 3.0 μm on the surface of the system permanent magnet body
A TiN coating layer having a film thickness of 0.5 μm to 10 μm is formed through the i coating, and the N ₂ concentration is continuously increased from the magnet side toward the TiN coating layer on the Ti coating surface to a film thickness of 0.0
A corrosion resistant permanent magnet having an N diffusion layer (composition TiNx) of 5 μm to 2.0 μm. 2. Fe-B-Ra whose main phase is a tetragonal phase
After cleaning the surface of the permanent magnet system, a thin film forming method
After forming a Ti coating having a film thickness of 0.1 μm to 3.0 μm on the surface of the magnet body, a mixed gas of Ar and N _{2 is} introduced into the processing container while continuously increasing the amount of N ₂ , and the N coating is applied to the Ti coating. ₂ After forming an N diffusion layer (composition TiNx) having a film thickness of 0.05 to 2.0 μm with increasing concentration, a film thickness of 0.5 μm to
A method for producing a corrosion resistant permanent magnet, which comprises forming a TiN coating layer having a thickness of 10 μm.