JPH0831363B2 - 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 permanent magnet whose surface is coated with a corrosion-resistant metal plating layer by electroless plating or electrolytic plating (Japanese Patent Application No. 58-162350). However, since the permanent magnet body is a sintered body and is porous in this plating method, the acidic solution or alkaline solution in the plating pretreatment remains in this hole,
There is a risk of corrosion over time, and since the magnet body has poor chemical resistance, the magnet surface is corroded during plating, resulting in poor adhesion and corrosion resistance.

Problems of Prior Art Although the corrosion resistant plating is provided on the surface of the Fe-BR permanent magnet, there is a problem that adhesion and corrosion resistance are poor because the permanent magnet body is a sintered body and has porosity. 60 ℃, relative humidity 90%
In the corrosion resistance test under the conditions described above, the magnet properties were deteriorated by more than 10% of the initial magnet properties after being left for 100 hours, and were very unstable.

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 whose magnet characteristics are stable even when left for a long time under an atmospheric condition of a temperature of 80 ° C. and a relative humidity of 90%. For the purpose of the method, as a result of various studies on the surface treatment of the permanent magnet body, by depositing a metal coating layer composed of a noble metal and a base metal on the surface of the Fe-BR type sintered magnet body 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 surface composed mainly of tetragonal phase with 10% to 30 atom%, B2 atom% to 28 atom% and Fe65 atom% to 80 atom% as main components. Is provided with a thin film of at least one noble metal selected from Pd, Ag, Pt, and Au by a vapor deposition method, and then further, at least one base metal selected from Ni, Cu, Sn, and Co is added. A method for producing a corrosion-resistant permanent magnet, characterized in that by performing electroless plating, the deterioration from the initial magnet characteristics is 10% or less when left for 500 hours at a temperature of 80 ° C and a relative humidity of 90%. is there.

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, when a metal layer made of at least one base metal selected from Ni, Cu, Sn, and Co is deposited on the surface of the Fe-BR sintered magnet body by a plating method, the temperature of 60
Under severe corrosion resistance test conditions of 100 ° C and 90% relative humidity for 100 hours, the magnet characteristic values deteriorate and become unstable. Pd, A
A metal coating layer according to the present invention, which is provided with at least one noble metal layer selected from g, Pt, and Au, and is further electrolessly plated with at least one base metal selected from Ni, Cu, Sn, and Co. It was revealed that the formation of the above makes the metal coating layer dense and can completely protect the permanent magnet 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 phase film forming method such as a vacuum vapor deposition method or an ion sputtering method, and the thickness of the noble metal layer is 10Å to 100Å.
Is preferred.

Further, in the present invention, at least one base metal layer selected from Ni, Cu, Sn, and Co is preferably deposited to a thickness of 25 μm or less by electroless plating, and more preferably 3 to The thickness is 20 μm, and any known electroless plating method can be used.

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 By containing atomic% or less of the additional element having the maximum value,
It is 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 is 12at% -17at%, B5at% -8at%, Co0.5at
% To 13 at%, Al 0.5 at% to 4 at%, C 1000 ppm or less, and the balance Fe and inevitable impurities are preferable.

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 obtained from the obtained permanent magnet body.

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

Next, a PdPt alloy film with a thickness of 50Å was applied to the obtained sintered magnet body by an ion sputtering method in an atmosphere of a vacuum degree of 0.05 Torr.
Nd-Dy-B-Fe coated on the surface with a PdPt alloy film on the surface
A permanent magnet was obtained.

Furthermore, Ni concentration 0.1 mol /, sodium hypophosphite 0.1
5 mol /, sodium citrate 0.2 mol /, ammonium sulphate 0.5 mol /, a pH 9.0 chemical nickel plating solution was prepared, and this nickel chemical plating solution was coated with the above PdPt alloy film on its surface. B-Fe permanent magnet at 80 ℃
After dipping for 60 minutes, it was washed with water and dried.

The resulting Ni plating thickness was 5.3 μm and had a metallic luster.

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 magnet characteristics and its deterioration state after standing for 500 hours under the condition of relative humidity of 90% were measured. The results are shown in Table 1.

Comparative Example The electroless plating was performed on the sintered magnet body obtained under the same composition and under the same manufacturing conditions as those of the example, under the same conditions as the plating conditions of the example 1. The resulting Ni plating thickness was 12 μm and had a dull metallic luster.

Deterioration of the magnet characteristics of this comparative sintered magnet body before and after the corrosion resistance test was maintained for 1 hour at a temperature of 60 ° C and a relative humidity of 90%, and the magnet characteristics deteriorated by 10.5%. Deterioration progressed, and rust was generated on the entire surface after 500 hours.

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

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 10% or less of the initial magnet characteristics.
It can be provided at low cost as the most demanded high-performance permanent magnet.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H01F 41/02 G (72) Inventor Hiroko Nakamura 2-15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka Prefecture Tomo Special Metal Co., Ltd. Yamazaki Works (72) Inventor Tomoyuki Imai 4-1-2, Funauri Minami, Naka-ku, Hiroshima City, Hiroshima Prefecture Toda Kogyo Co., Ltd. Creation Center (72) Inventor Toshiki Matsui Funairi, Naka-ku, Hiroshima City, Hiroshima Prefecture Minami 4-chome 1-2 Toda Kogyo Co., Ltd. Creation Center (72) Inventor Nansei Horiishi 4-1-2 Funairi Minami 4-chome, Naka-ku, Hiroshima City, Hiroshima Prefecture Toda Kogyo Co., Ltd. Creation Center (56) References 61-150201 (JP, A) JP-A-60-54406 (JP, A) JP-A-53-114738 (JP, A)

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 A thin film of at least one noble metal selected from Pd, Ag, Pt, and Au is formed on the surface of the sintered permanent magnet body by a vapor deposition method, and then selected from Ni, Cu, Sn, and Co. A method for producing a corrosion-resistant permanent magnet, which comprises subjecting at least one base metal to electroless plating.