JPH0831365B2 - Method for manufacturing corrosion-resistant permanent magnet - Google Patents

Description

TECHNICAL FIELD The present invention has high magnetic properties and excellent corrosion resistance.
The present invention relates to a method for manufacturing a Fe-BR permanent magnet, which has a corrosion resistance, particularly
The present invention relates to a method for producing a Fe-BR permanent magnet having extremely stable magnet characteristics with little deterioration from the initial magnet characteristics when left for a long time in an atmosphere of 80 ° C and 90% relative humidity.

BACKGROUND ART First, light rare earths, which are rich in resources centered on Nd and Pr, are used as the main components of B and Fe, and they do not contain expensive Sm or Co. Fe-BR permanent magnets have been proposed as a new high-performance permanent magnet that exceeds the above (Japanese Patent Laid-Open Nos. 59-46008 and 59-89401).
Issue).

The Curie point of the magnet alloy is generally 300 ° C to 370 ° C.
However, by substituting a part of Fe with Co, an Fe-BR type permanent magnet having a higher Curie point (Japanese Patent Application Laid-Open No. S60-18753).
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, In order to improve the temperature characteristics, especially iHc, Co containing mainly rare earth elements such as Nd and Pr as rare earth elements (R) is contained.
By including at least one kind of heavy rare earth such as Dy and Tb in a part of R of the Fe-BR rare earth permanent magnet, 25
IHc with extremely high (BH) max higher than MGOe
A Fe-BR rare earth permanent magnet containing Co, which is further improved, has been proposed (JP-A-60-34005).

However, Fe-
A permanent magnet made of a B-R magnetically anisotropic sintered body contains iron as a main component, which is a rare earth element that easily oxidizes in air to form a stable oxide, and iron. In addition, the oxide generated on the surface of the magnet causes a decrease in the output of the magnetic circuit and a variation between the magnetic circuits, and there is a problem that the peripheral oxide is contaminated due to the dropping of the surface oxide.

Therefore, in order to improve the corrosion resistance of the Fe-BR permanent magnet, a method of forming a metal thin film on the surface of the sintered magnet body by vapor-phase plating is proposed (Japanese Patent Application No. 61-150201, Japanese Patent Application Laid-Open No. Sho 61-150201). 61
-166115, JP-A-61-166116, JP-A-61-166117
However, although the corrosion resistance of the Fe-BR permanent magnet is improved, the adhered metal particles are formed by being deposited on the surface of the magnet body, so that the adhesion strength is weak. ,
In particular, the deposition of metal particles at the corners of the magnet becomes uneven,
When used for a long time in a harsh environment, there was a problem of local peeling and cracking of the adherend and local rusting.

Problems of Prior Art That is, a metal thin film is formed on the surface of the Fe-BR permanent magnet by a vapor phase plating method to improve corrosion resistance, but there is a problem that adhesion and corrosion resistance at corners of the magnet are poor. However, there was a problem of local rust generation when used for a long time in a harsh environment.

OBJECT OF THE INVENTION The present invention aims to improve the corrosion resistance of Fe-BR permanent magnets, and particularly to prevent deterioration from the initial magnet characteristics when left standing for a long time under an atmospheric condition of temperature 80 ° C and relative humidity 90%. An object of the present invention is to provide a manufacturing method that can provide an Fe-B-R-based permanent magnet that has stable and high magnet characteristics with a minimum amount at a low cost.

Structure of the Invention The present invention has excellent corrosion resistance, and in particular, manufacture of a Fe-B-R permanent magnet having stable magnet characteristics even when left standing for a long time under an atmospheric condition of a temperature of 80 ° C. and a relative humidity of 90%. As a result of various studies on the surface treatment of the permanent magnet for the purpose of the method, by applying a metal coating layer made of a noble metal and a specific metal on the surface of the Fe-BR type sintered magnet having a specific component. The inventors have completed the present invention by finding that excellent corrosion resistance and extremely stable magnet characteristics can be obtained.

That is, the present invention relates to R (R is at least one of Nd, Pr, Dy, Ho, and Tb, or La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu,
Sintered permanent magnet body containing 10 to 30 atomic% of B, 2 to 28 atomic% of B and 65 atomic% to 80 atomic% of Fe as a main component and a tetragonal phase as a main phase. After a thin film of at least one noble metal selected from Pd, Ag, Pt and Au or an alloy thereof is provided on the surface, Ni,
By providing a thin film of at least one metal selected from Cu, Sn, Al, Cr, Zn and Co or a thin film of these alloys by a vapor deposition method, the temperature is 80 ° C and the relative humidity is 90%. The method for producing a corrosion-resistant permanent magnet is characterized in that the deterioration from the initial magnet characteristics when left for 500 hours is 5% or less.

The reason why the Fe-BR type permanent magnet having the metal coating layer according to the present invention has little deterioration from the initial magnet characteristics under extremely harsh atmospheric conditions and the magnet characteristic values are extremely stable is not yet clear.

However, at least one metal selected from Ni, Cu, Sn, Al, Cr, Zn and Co or an alloy thin film thereof is formed on the surface of the Fe-BR sintered magnet body by a vapor deposition method. If adhered, the magnet characteristic values will become unstable due to rust generation due to defects in the local coating under the severe corrosion resistance test conditions that were left at a temperature of 80 ° C and a relative humidity of 90% for 500 hours. At least one noble metal layer selected from Pd, Ag, Pt and Au or an alloy layer thereof is provided on the surface of the sintered magnet body, and Ni, C
By forming a thin film layer of at least one metal or alloy selected from u, Sn, Al, Cr, Zn and Co by a vapor deposition method to form a metal coating layer according to the present invention, the metal coating layer is formed. Became dense and it became clear that the permanent magnet could be completely protected against changes in the external environment such as moisture and gas.

Preferred Embodiments of the Invention In the present invention, Pd, Ag, provided on the surface of the sintered magnet body,
The noble metal layer made of at least one selected from Pt and Au is provided by a known vapor deposition method such as vacuum deposition method, ion sputtering method, ion plating method, or Pd in a non-aqueous liquid medium. It can be obtained by adsorbing at least one precious metal colloid selected from Ag, Pt, Au, or by adsorbing the precious metal colloid in a neutral liquid medium having a specific pH value. . The thickness of the noble metal layer in the present invention is preferably 10Å to 100Å.

In the present invention, as the non-aqueous liquid medium for adsorbing the noble metal colloid, benzene, toluene, hydrocarbons such as xylene, trichlorotrifluoroethane, chloroform, halogenated hydrocarbons such as trichloroethane,
Ethyl acetate or the like is preferable, and as an adsorption method, a method of immersing the sintered magnet body in a non-aqueous liquid medium in which the precious metal colloid is dispersed or a non-aqueous liquid medium in which the metal colloid is dispersed is sintered. A method of coating on the surface of the magnet body is preferable.

In the present invention, the neutral liquid medium is tin chloride in the presence of a water-soluble dispersant, such as a noble metal salt of palladium chloride, a noble metal having a particle size of 20 to 50 Å obtained by reduction with a water-soluble reducing agent such as hydrazine. Is a neutral liquid medium having a pH of 6.0 to 9.0 uniformly dispersed.

The reason for limiting the pH value of the neutral liquid medium to pH 6.0 to pH 9.0 is that the Fe-BR sintered body may be eroded if the pH value is less than 6.0, and if it exceeds pH 9.0. It is not preferable because a stable dispersion medium cannot be obtained. As the adsorption method, a method of immersing the sintered magnet body in a neutral liquid medium in which the noble metal colloid is dispersed or a method of applying the neutral liquid medium to the surface of the sintered magnet body is preferable.

In the present invention, at least one metal layer selected from Ni, Cu, Su, Al, Cr, Zn and Co or an alloy layer thereof is a gas phase such as a vacuum vapor deposition method, an ion sputtering method, an ion plating method. 25 μm, which is formed by the film forming method
The thickness is preferably the following, and more preferably 3 to 20 μm.

Reasons for Limiting Components of Permanent Magnet Although the rare earth element R used in the permanent magnet according to the present invention occupies 10 atom% to 30 atom% of the composition, Nd, Pr, Dy, Ho,
At least one of Tb, or further, La, Ce, S
Those containing at least one of m, Gd, Er, Eu, Tm, Yb, Lu, and Y are preferable.

Further, although one of R is usually sufficient, in practice, a mixture of two or more kinds (Misch metal, didymium, etc.) can be used for reasons of availability and the like.

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 is an essential element in the above-mentioned permanent magnet,
If it is less than 10 atom%, the crystal structure will be a cubic crystal structure having the same structure as α-iron, so that high magnetic properties, especially high coercive force cannot be obtained, and if it exceeds 30 atom%, there are many R-rich nonmagnetic phases. As a result, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics cannot be obtained. Therefore, the rare earth element is 10 atomic%
The range is up to 30 atom%.

B is an essential element in the permanent magnet according to the present invention, and if it is less than 2 atomic%, the rhombohedral structure becomes the main phase,
A high coercive force (iHc) cannot be obtained, and if it exceeds 28 atom%,
An excellent permanent magnet cannot be obtained because the B-rich nonmagnetic phase increases and the residual magnetic flux density (Br) decreases. Therefore, B is in the range of 2 at% to 28 at%.

Fe is an essential element in the above-mentioned permanent magnet, and is 65
If it is less than atomic%, the residual magnetic flux density (Br) will decrease,
If it exceeds, a high coercive force cannot be obtained, so Fe is contained at 65 to 80 atomic%.

Further, in the permanent magnet according to the present invention, part of Fe is
By substituting with Co, the temperature characteristics can be improved without deteriorating the magnetic characteristics of the obtained magnet, but when the Co substitution amount exceeds 20% of Fe, the magnetic characteristics are deteriorated.
Not preferred. The substitution amount of Co is 5 atomic% in the total amount of Fe and Co.
In the case of up to 15 atom%, (Br) increases as compared with the case where no substitution is carried out, which is preferable for obtaining a high magnetic flux density.

Further, the permanent magnet according to the present invention can tolerate the presence of impurities unavoidable in industrial production in addition to R, B and Fe, but a part of B is 4.0 atom% or less of C, 3.5 atom% or less of P, At least one of 2.5 atomic% or less S and 3.5 atomic% or less Cu
It is possible to improve the manufacturability of permanent magnets and reduce the cost by substituting the total amount of seeds by 4.0 at% or less.

Further, at least one of the following additional elements is RB
It can be added to the Fe-based permanent magnet because it is effective in improving the coercive force and squareness of the demagnetization curve, improving the manufacturability, and lowering the cost.

9.5 atomic% or less Al, 4.5 atomic% or less Ti, 9.5 atomic% or less V, 8.5 atomic% or less Cr, 8.0 atomic% or less Mn, 5.0 atomic% or less Bi, 9.5 atomic% or less Nb, 9.5 Ta less than atomic%, Mo less than 9.5 atomic%, W less than 9.5 atomic%, Sb less than 2.5 atomic%, Ge less than 7 atomic%, Sn less than 3.5 atomic%, Zr less than 5.5 atomic%, 9.0 atomic % Or less Ni, 9.0 atom% or less Si, 1.1 atom% or less Zn, and 5.5 atom% or less Hf, at least one kind is added, but when two or more kinds are contained, the maximum content is Inclusion of atomic% or less of the additive element having the maximum value makes it possible to increase the coercive force of the permanent magnet.

The fact that the main phase of the crystal phase is a tetragonal crystal is indispensable for producing a sintered permanent magnet having excellent magnetic properties from a fine and uniform alloy powder.

Further, the permanent magnet according to the present invention has an average crystal grain size of 1 to
A compound having a tetragonal crystal structure in the range of 80 μm as a main phase and a nonmagnetic phase (excluding an oxide phase) of 1% to 50% by volume is characterized.

The permanent magnet according to the present invention exhibits a coercive force iHc ≧ 1 kOe and a residual magnetic flux density Br> 4 kG, and has a maximum energy product (BH) max.
Indicates (BH) max ≧ 10MGOe, and the maximum value reaches 25MGOe or more.

Further, the main component of R of the permanent magnet according to the present invention is
When the light rare earth metal mainly composed of Nd and Pr occupies 50% or more, R12 atom% to 20 atom%, B4 atom% to 24 atom%, Fe7
When the main component is 4 atom% to 80 atom%, (BH) max35
It exhibits excellent magnetic properties above MGOe, and its maximum reaches 45 MGOe or above, especially when the light rare earth metal is Nd.

In addition, as a permanent magnet according to the present invention showing extremely high corrosion resistance in a corrosion resistance test of leaving it in an environment of 80 ° C. and 90% relative humidity for a long time, Nd11at% to 15at%, Dy0.2at% to 3.0at%, and Nd Dy
The total amount of 12at% to 17at%, B5at% to 8at%, Co0.5
It is preferable that it contains at% to 13 at%, Al0.5 at% to 4 at%, C 1000 ppm or less, and the balance F and unavoidable impurities.

Examples The present invention will be described below with reference to Examples and Comparative Examples.

Example As starting materials, electrolytic iron having a purity of 99.9%, ferroboron alloy containing B19.4%, Nd having a purity of 99.7% or more, and Dy are used, and after blending these, high-frequency melting and casting, 14Nd
An ingot having a composition (at%) of −0.5Dy-7B-78.5Fe was obtained.

Then, this ingot was finely pulverized to obtain finely pulverized powder having an average particle size of 3 μm.

This finely pulverized powder was put into a die of a press machine, oriented in a magnetic field of 12 kOe, and molded at a pressure of 1.5 ton / cm ^{2 in} a direction parallel to the magnetic field, and the obtained molded body was heated at 1100 ° C for 2 After sintering in Ar atmosphere for 800 hours in Ar atmosphere for 1 hour,
Then, aging treatment was performed at 630 ° C. for 1.5 hours to obtain a sintered magnet body.

A test piece having a diameter of 12 mm and a thickness of 2 mm was prepared from the obtained permanent magnet body.

 The magnet characteristics of this sintered magnet body test piece are shown in Table 1.

Next, the obtained sintered magnet test piece was subjected to a vacuum degree of 0.05 Torr.
The PdPt alloy film was deposited by the ion sputtering method in the atmosphere.

Furthermore, on the above-mentioned test piece coated with a PdPt alloy film on the surface,
A Ni film was deposited on the surface by a vacuum deposition method in an atmosphere having a vacuum degree of 10 ^-6 Torr.

The obtained sintered magnet body test piece had a metallic luster on the surface.

Next, the results of the emission plasma spectroscopic analysis of the permanent magnet, measured using an ICAP575 type emission plasma spectrophotometer, show that Pd was 0.01 wt% and Ni was 1.2 wt% and the Pd layer thickness was 50Å, Ni layer thickness was 5.0 μm.

Table 1 shows the magnetic characteristics of the permanent magnet according to the present invention after the surface treatment.

Then, the obtained permanent magnet of the present invention,
The appearance, the magnet characteristics, and the deterioration state after standing for 500 hours under the condition of relative humidity of 90% were measured. The result is first
Shown in the table.

Example 2 Using the same sintered magnet body test piece as in Example 1, the test piece was immersed in toluene in which a palladium colloid having a particle size of about 20Å was dispersed for 10 minutes, and then the toluene dispersion medium was used. Nd adsorbed palladium colloid on the surface
A -Dy-B-Fe based permanent magnet was obtained.

Furthermore, on the above-mentioned test piece coated with a PdPt alloy film on the surface,
A Ni film was deposited on the surface by a vacuum deposition method in an atmosphere having a vacuum degree of 10 ^-6 Torr.

The obtained sintered magnet body test piece had a metallic luster on the surface.

Next, the results of the emission plasma spectroscopic analysis of the permanent magnet, measured using an ICAP575 type emission plasma spectrophotometer, show that Pd is 0.01 wt% and Ni is 1.5 wt% and the Pd layer thickness is 60Å, Ni layer thickness was 5.0 μm.

Table 1 shows the magnetic characteristics of the permanent magnet according to the present invention after the surface treatment.

Then, the obtained permanent magnet of the present invention,
The appearance, the magnet characteristics, and the deterioration state after standing for 500 hours under the condition of relative humidity of 90% were measured. The result is first
Shown in the table.

Example 3 Using the same sintered magnet body test piece as in Example 1, the particle size was
After dipping the above test piece for 10 minutes in acetone containing 0.4 g of 200 Å to 300 Å aluminum oxide colloid ("aluminium Oxide C" manufactured by Nippon Aerosil Co., Ltd.), the dispersion medium acetone was evaporated to form an aluminum oxide colloid. A test piece adsorbed on the surface was obtained.

Then, in pure water in which a palladium colloid with a particle size of about 30Å is dispersed, soak the above test piece with the aluminum oxide colloid adsorbed on the surface for 15 minutes, then wash with water and dry it, and then put the palladium colloid on the surface. Adsorbed Nd-Dy-
A B-Fe based permanent magnet test piece was obtained.

Furthermore, the above-mentioned test piece coated with palladium colloid on the surface was vacuum-deposited in an atmosphere with a vacuum degree of 10 ^-6 Torr.
A Ni film was deposited on the surface.

The obtained sintered magnet body test piece had a metallic luster on the surface.

Next, the results of the emission plasma spectroscopic analysis of the permanent magnet, measured using an ICAP575 type emission plasma spectrophotometer, show that Pd is 0.01 wt% and Ni is 1.5 wt% and the Pd layer thickness is 60Å, Ni layer thickness was 5.0 μm.

Table 1 shows the magnetic characteristics of the permanent magnet according to the present invention after the surface treatment.

Then, the obtained permanent magnet of the present invention,
The appearance, the magnet characteristics, and the deterioration state after standing for 500 hours under the condition of relative humidity of 90% were measured. The result is first
Shown in the table.

Comparative Example A sintered magnet body obtained under the same composition and under the same manufacturing conditions as in Example was vacuum-deposited under the same conditions as in Example 1 to deposit a Ni film. The Ni film thickness was 5.1 μm and had a dull metallic luster.

The obtained comparative permanent magnet was tested at a temperature of 80 ° C and a relative humidity of 90%.
The appearance, the magnet characteristics, and the deterioration state thereof after standing for 500 hours under the above conditions were measured. The results are shown in Table 1.

The permanent magnet according to the present invention, as shown in Table 1, shows the appearance before and after the corrosion resistance test, the magnet characteristics, and the deterioration rate of the characteristics,
It is clear that there is little deterioration from the excellent initial magnet characteristics, and that it has excellent corrosion resistance and stability of the magnet characteristics.

EFFECTS OF THE INVENTION The Fe-BR type permanent magnet body according to the present invention is subjected to severe corrosion resistance test conditions, in particular, a temperature of 80 ° C. and a relative humidity, as in Examples.
After being left for 500 hours under the condition of 90%, the deterioration of the magnet characteristics is only 5% or less of the initial magnet characteristics.
It can be provided at low cost as the most demanded high-performance permanent magnet.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hiroko Nakamura Inventor Hiroko Nakamura 2-15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka Prefecture Yamazaki Works Sumitomo Special Metals Co., Ltd. (72) Tomoyuki Imai Funairi Minami, Naka-ku, Hiroshima-shi, Hiroshima 4-1-2 Toda Kogyo Co., Ltd. Creation Center (72) Inventor Toshiki Matsui 4-1-2 Funaruinami Naka-ku, Hiroshima City, Hiroshima Prefecture Toda Kogyo Co., Ltd. Creation Center (72) Inventor Horiishi Nanao Hiroshima 1-2, Funairi Minami, Naka-ku, Hiroshima-shi, Toda

Claims (1)

[Claims] 1. R (R is at least one of Nd, Pr, Dy, Ho and Tb, or further La, Ce, Sm, Gd, Er, Eu, T
m, Yb, Lu, and Y) consisting of at least 1) 10 atom% to 30 atom%, B2 atom% to 28 atom%, Fe65 atom% to 80 atom% as main components, and main phase from tetragonal phase After providing a thin film of at least one noble metal selected from Pd, Ag, Pt and Au on the surface of the sintered permanent magnet body, the Ni, Cu, Sn, Al, Cr, Zn and A method for producing a corrosion-resistant permanent magnet, characterized in that a thin film of at least one metal selected from Co or an alloy thereof is provided by a vapor deposition method.