JPH0752684B2 - Corrosion resistant permanent magnet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a Fe—B—R magnet having excellent corrosion resistance, which is provided with a melt-solidified layer formed by laser beam irradiation on the surface thereof to significantly improve the corrosion resistance. R-type magnets.

BACKGROUND ART The applicant has previously used a light rare earth, which is rich in resources, mainly N2d and pr, as a main component of B and Fe, and does not contain expensive Sm or Co. Fe-BR type permanent magnets have been proposed as new high-performance permanent magnets that greatly exceed the characteristics (Japanese Patent Laid-Open Nos. 59-46008 and 59-894).
No. 01 bulletin).

The Curie point of the magnet alloy is generally 300 ° C. to 370 ° C., but by substituting a part of Fe with Co, an Fe—BR system permanent magnet having a higher Curie point is obtained. Kakai 59-64733, JP-A-59-132104), and C
O-containing Fe-BR rare earth permanent magnets have Curie points equal to or higher than those and higher (BH) max. In order to improve their temperature characteristics, especially iHc, Nd and Pr are used as rare earth elements (R). Fe-B- mainly containing light rare earths such as Co
By containing at least one heavy rare earth element such as dy and Tb in part of R of the R type rare earth permanent magnet, iHc was further improved while maintaining an extremely high (BH) max of 25 MGOe or more. A Fe-BR rare earth permanent magnet containing Co has been proposed (JP-A-60-34005).

However, Fe-B having the above-mentioned excellent magnetic properties
A permanent magnet made of an R-type magnetic anisotropic sintered body contains iron as a main component, which is a rare earth element and iron that easily oxidize in air to form a stable oxide. The oxides generated on the surface of the magnet cause a decrease in the output of the magnetic circuit and a variation between the magnetic circuits, and there is a problem that the peripheral devices are contaminated due to the dropping of the surface oxide.

Therefore, in order to improve the corrosion resistance of the above Fe-BR permanent magnet, the applicant has proposed a permanent magnet whose surface is coated with a corrosion-resistant metal plating layer by electroless plating or electrolytic plating (Japanese Patent Application No. 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. Therefore, we proposed a permanent magnet coated with a corrosion resistant resin layer on the surface of the magnet body by spraying or dipping (Japanese Patent Application No. 58-171907), but its corrosion resistance was not sufficient and it could not be used for a long time under severe environmental conditions. was there.

OBJECT OF THE INVENTION The present invention aims at improving the corrosion resistance of an F-B-R permanent magnet material, and aims at an F-B-R permanent magnet exhibiting excellent corrosion resistance by a simple surface treatment. .

Structure and Effect of the Invention The present invention has been conducted as a result of various studies on surface treatments to be applied to the surface of a Fe-BR permanent magnet for the purpose of Fe-BR permanent magnet exhibiting excellent corrosion resistance. By irradiating the surface of the with a laser beam, the irradiated area locally and instantaneously becomes hot, and is rapidly cooled by heat conduction to form an ultrathin amorphous melt-solidified layer on the magnet surface. The inventors have completed the present invention by discovering that the surface of the magnet body can be made non-porous to significantly improve the corrosion resistance without deteriorating the magnetic characteristics.

That is, the present invention provides R (R is at least one of Nd, Pr, Dy, Ho, Tb, or further La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu, Y.
Of at least 11) of 10 to 30 at%, B2 to 28 at%, Fe at 80 to 80 at% as the main component, and the main phase of the sintered permanent magnet body is a tetragonal phase. It is characterized in that it has a non-porous layer made of a melt-solidified layer by laser beam irradiation, or an oxidation resistant coating layer is further provided through a non-porous layer made of a melt-solidified layer by laser beam irradiation on the surface. It is a corrosion resistant permanent magnet.

The oxidation resistant coating layer provided via the melted and solidified layer by laser beam irradiation includes an oxidation resistant resin layer, a plating layer or a vapor phase plating layer.

The Fe-BR permanent magnet according to the present invention has (BH) max25M
It has more than GOe and more than iHc10KOe, and is far superior to the conventional Fe-BR permanent magnet with the oxidation resistant coating layer in the long-term holding test at the temperature of 60 ° C and the relative humidity of 90%. Has corrosion resistance.

Preferred Embodiment of the Invention In the present invention, the thickness of the melt-solidified layer on the surface of the sintered magnet body by laser beam irradiation is preferably 10 μm or less.

In the present invention, the laser beam wavelength is preferably 5 μm or less, which is easily absorbed by deposits on the surface and holes, oil and fat, and water, and more preferably 2 μm or less, which has an absorption effect on the magnet body.

Further, the laser beam irradiation may be performed by any method as long as the extreme surface layer can be melted and solidified, for example, by converging the beam in a spot shape and moving the magnet body and the laser beam in the same direction or opposite directions. Furthermore, the laser beam is moved while oscillating in the width direction of the magnet, or the beam is expanded by using a lens or mirror to irradiate it in the width direction all at once, and the entire surface of the surface to be deposited is uniformly irradiated. Alternatively, the irradiation can be performed in various irradiation forms such as a zigzag shape and a meandering shape.

Further, a method in which a laser beam is oscillated from a laser oscillator, condensed by a collimator and a lens, and guided to a required position by an optical fiber for irradiation is also employable.

In this invention, the irradiation condition of the laser beam, the power density of the beam is preferably in the range of ^{100kW / mm 2 ~1500kW / mm 2} , more preferably ^{300kW / mm 2 ~900kW / mm 2} .

The oxidation resistant resin layer in the present invention may be a synthetic resin for coating such as a fluorine resin, an epoxy resin, a thermosetting acrylic resin, an alkyd resin, a melamine resin, a silicone resin or a composite resin of these resins, Further, for the purpose of rust prevention and improvement of coating film reinforcement, the above resin may contain a rust preventive pigment such as zinc oxide, zinc chromate, or red lead, or may contain benzotriazole. .

In the present invention, the above pigment contained in the resin is
The content may be 80% or less with respect to the resin amount, and the content of benzotriazole may be 1% or less with respect to the resin amount.

The oxidation resistant resin layer may be coated by spraying, dipping, electrostatic powder coating, electrodeposition coating, etc., and then baking.
If the thickness is 25 μm or more, it is difficult to obtain the dimensional accuracy of the product if the thickness exceeds 25 μm. Therefore, the thickness is preferably 25 μm or less.

In addition, the surface of the permanent magnet body may be subjected to a surface treatment before applying the resin layer, and the surface treatment film is preferably a phosphate film of zinc phosphate, manganese phosphate or the like, or a chromate film. The coating thickness is preferably 5 μm or less from the viewpoint of corrosion resistance, strength, and cost.

In the present invention, to deposit the plating layer, electroless plating method or electrolytic plating method can be used, Ni, Cu, Zn or other metal or its alloy plating or composite plating layer is preferable, as the plating layer thickness A thickness of 25 μm or less is preferable.

In the present invention, in order to deposit the vapor phase plating thin film,
A thin film forming method such as vacuum deposition, sputtering, or ion plating can be appropriately selected and used. The vapor plating material is preferably a metal such as Al, Ni, Cr, Cu, Co or Zn, or an alloy thereof. Further, the thickness of the thin film layer is preferably 25 μm or less, more preferably 5 μm to 20 μm, in consideration of peeling of the thin film layer, deterioration of mechanical strength, and ensuring of corrosion resistance.

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

Also, one type of R is usually sufficient, but it is practically 2
Mixtures of more than one species (Misch metal, didymium, etc.) can be used for reasons of 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 is an essential element in the above-mentioned permanent magnet,
If it is less than 30% by atom, the crystal structure has the same cubic structure as α-iron and a cubic structure, so that high magnetic properties, particularly high coercive force, cannot be obtained. However, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent properties cannot be obtained. Therefore, the rare earth element is 10 atomic% ~
The range is 30 atom%.

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

Fe is an essential element in the above-mentioned permanent magnet, and the residual magnetic flux density (Br) decreases if it is less than 65 atom%, and a high coercive force cannot be obtained if it exceeds 80 atom%.
The content is up to 80 atom%.

Further, in the permanent magnet of the present invention, substituting a part of Fe with Co can improve the temperature characteristics without impairing the magnetic characteristics of the obtained magnet.
If it exceeds 20%, on the contrary, the magnetic properties deteriorate, which is not preferable. The substitution amount of Co is 5 atom% to 15 in the total amount of Fe and Co.
In the case of atomic%, (Br) increases as compared with the case of not substituting, so that it is preferable to obtain a high magnetic flux density.

Further, the permanent magnet material of the present invention can tolerate the presence of impurities that are unavoidable in terms of industrial productivity in addition to R, B and Fe, but a part of B is 4.0 atomic% or less C, and 3.5 atomic% or less. At least 1 of P, 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 Fe-based permanent magnets because it improves the coercive force and squareness of the demagnetization curve, improves manufacturability, and hardens to reduce costs.

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 at most atomic% of the additive 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.

The permanent magnet of the present invention has an average crystal grain size of 1 to 80 μm.
The compound having a tetragonal crystal structure in the range of 1) as the main phase and containing 1% to 50% by volume of the nonmagnetic phase (excluding the oxide phase) 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 50
% Of light rare earth metal mainly composed of Nd and Pr, R12 atom% to 20 atom%, B4 atom% to 24 atom%, Fe74
(BH) max35M when the main component is from atomic% to 80 atomic%
It shows excellent magnetic properties over GOe, and its maximum value reaches over 45MGOe especially when the light rare earth metal is Nd.

Further, in this invention, as a permanent magnet showing extremely high corrosion resistance in a corrosion resistance test of leaving it in an environment of 60 ° C and a relative temperature of 90% for a long time, Nd11at% ~ 10at%, Dy0.2at% ~ 3.0at%, and Nd And the total amount of Dy 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 Example 1 As starting materials, electrolytic iron having a purity of 99.9%, ferroboron alloy containing B19.4%, ND, Dy, Co, Al having a purity of 99.7% or more,
Were mixed with each other by high-frequency melting and then cast in a water-cooled copper mold to obtain an ingot having a composition (at%) of 14Nd-0.5Dy-7B-6Co-2Al-the balance Fe.

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

This finely pulverized powder was loaded into a die of a press machine, oriented in a magnetic field of 12 kOe, and molded in a direction parallel to the magnetic field at a pressure of 1.5 t / cm ² , to obtain a molded body at 1100 ° C. After being sintered for 2 hours in an Ar atmosphere, the mixture was allowed to cool and then aged at 600 ° C. for 2 hours in an Ar atmosphere to obtain a permanent magnet.

A test piece was cut out from the obtained permanent magnet in a size of length 20 mm × width 10 mm × thickness 8 mm.

As an atmosphere gas in the irradiation box for the laser irradiation device
Using Ar gas, 100W output Q-switch type YAG laser,
Under the conditions of a lens focal length of 100 mm, a wavelength of 1.00 μm and a laser power density of 500 kW / mm ² , only a half of the 20 mm × 10 mm rectangular portion of the surface of the test piece is irradiated with the laser beam, and the irradiated surface and non-irradiated area. A test piece for evaluation of corrosion resistance having a surface was obtained.

When the test piece was observed with an electron microscope (1500 times), there were many holes penetrating several tens of μm or less inside the laser beam non-irradiated surface. Is sealed and there is no through hole, and the surface is 1-3
An amorphous non-porous layer having a thickness of μm was formed.

Test the test piece at a temperature of 60 ° C and a relative humidity of 90% in an atmosphere of 200
When subjected to the time holding test, red rust was generated on the entire surface not irradiated with the laser beam, but no rust was observed on the surface irradiated with the laser beam.

Example 2 The test piece of Example 1 was prepared by adding a frequency of 16 KHz, a defocus of 2 mm,
Using the YAG laser beam irradiation apparatus of Example 1 under the condition of an amplitude of 20 mm, the entire surface of the test piece was irradiated with a laser beam, and a sintered magnet having a melt-solidified layer with a thickness of 3 to 8 μm on the entire surface of the test piece. Got the body

Furthermore, the epoxy resin is applied on the melted and solidified layer of the test piece by a spray method and baked at 90 ° C. for 5 hours, and the surface is
Test pieces according to the invention having a resin layer with a thickness of 12-18 μm were obtained.

For comparison, the test piece of Example 1 was coated with an epoxy resin by a spray method without irradiation with a laser beam,
Baking was performed at 90 ° C. for 5 hours to obtain a comparative test piece having a resin layer having a thickness of 12 to 18 μm on the surface.

The two test pieces were subjected to a 1000-hour holding test in an atmosphere at a temperature of 60 ° C. and a relative humidity of 90% to observe the rusting condition and measure the magnetic properties. The results are shown in Table 1.

As is clear from Table 1, the permanent magnet according to the present invention, which is irradiated with a laser beam and has an epoxy resin layer deposited on the surface thereof, is significantly superior in corrosion resistance to conventional permanent magnets.

Claims (2)

[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, Y consisting of at least 11 kinds) 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 corrosion-resistant permanent magnet having a non-porous layer made of a melt-solidified layer formed by laser beam irradiation on the surface of the sintered permanent magnet body. 2. 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, Y consisting of at least 11 kinds) 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 corrosion-resistant permanent magnet, characterized in that it has an oxidation-resistant coating layer on the surface of the sintered permanent magnet body formed by a non-porous layer made of a melt-solidified layer by laser beam irradiation.