JPH05205923A - Manufacture of permanent magnet having excellent corrosion-proof property - Google Patents

Abstract

PURPOSE:To form a corrosion-proof thin film, having excellent adhesive property and corrosion-proof property, on the surface of a permanent magnet material in uniform thickness by a method wherein a corrosion-proof thin film layer is formed on the surface of a permanent magnet body, having the main phase consisting of tetragonal crystal, by an ion vapor-deposition thin film forming method. CONSTITUTION:The fine powder, in the composition of Nd 15, Dy 1.5, B 8 and Fe 75.5atom%, is placed in a metal mold, the fine powder is oriented in a magnetic field, and a molded body is formed by molding. The molded body is heat-treated, and a permanent magnet is manufactured. A test piece is cut out from the permanent magnet obtained, the Ti thin piece of coating material is evaporated by arc discharge under vacuum in a vacuum container containing the test piece, N2 gas is formed into accelarated N2 gas ions, Ti vapor and N2 gas ions are made to irradiate, and a Ti thin film is formed on the surface of the test piece. As a result, a corrosion-proof thin film layer, having the prescribed thickness and excellent uniformity, can be obtained, and the oxidization of the permanent magnet can completely be prevented.

Description

Detailed Description of the Invention

[0001]

This invention relates to R (R
Is at least one of rare earth elements including Y), B, F
The present invention relates to a method for producing a permanent magnet containing e as a main component, and relates to a method for producing a rare earth / boron / iron-based permanent magnet in which a corrosion-resistant thin film is formed by an ion deposition thin film forming method (IVD) to improve the corrosion resistance of the permanent magnet.

[0002]

2. Description of the Related Art The typical current permanent magnet materials are alnico, hard ferrite and rare earth cobalt magnets. With the destabilization of the situation of cobalt raw materials in recent years, the demand for alnico magnets containing 20 to 30 wt% of cobalt has decreased, and inexpensive hard ferrite containing iron oxide as a main component has become the mainstream of magnet materials. became.

On the other hand, rare earth cobalt magnets contain 5% cobalt.
It is very expensive because it contains 0 to 60 wt% and Sm, which is rarely contained in rare earth ores, but is very expensive compared to other magnets, so it is mainly small and has high added value. It has become widely used in magnetic circuits.

The applicant has previously proposed Fe-BR as a new high-performance permanent magnet which does not necessarily contain expensive Sm and Co.
A system (R is at least one of rare earth elements including Y) permanent magnet has been proposed (Japanese Patent Application No. 57-145072). This permanent magnet uses Rd, which is a resource-rich light rare earth element centered on Nd and Pr, and has 25 MG with Fe as a main component.
It is an excellent permanent magnet that exhibits an extremely high energy product over Oe.

[0005]

The Fe-BR type permanent magnet having the above-mentioned excellent magnetic characteristics has, as a main component,
Since it contains iron and rare earth elements that are easily oxidized in air,
When incorporated into a magnetic circuit, the oxide generated on the surface of the magnet causes the output of the magnetic circuit to decrease and the magnetic circuit to fluctuate, and there is a problem of contamination of peripheral equipment due to the dropping of the surface oxide. ..

[0006] Therefore, the applicant has previously proposed the above Fe-B-
In order to improve the target system of the R type permanent magnet, a permanent magnet having a corrosion resistant metal plating layer coated on the surface of the magnet body by electroless plating or electrolytic plating (Japanese Patent Application No. 58-162350).
No.) and a permanent magnet whose surface is coated with a corrosion-resistant resin layer by spraying or dipping (Japanese Patent Application No. 58-171907).

However, in the former plating method, when the permanent magnet body is a sintered body, since the sintered body is porous, an acidic solution or an alkaline solution in the plating pretreatment remains in the holes. However, there is a problem that it may corrode with age, and the chemical resistance of the magnet body is poor, so the surface of the magnet is corroded during plating, resulting in poor adhesion and corrosion resistance.

Further, since the latter method of coating a resin by a spray method has directionality, it takes a lot of steps and labor to form a uniform resin film on the entire surface of the object to be treated, and it is particularly difficult to form the irregular shape. It is difficult to apply a coating having a uniform thickness to the magnet body, and the dipping method causes a non-uniform resin coating thickness, resulting in poor product dimensional accuracy.

The present invention aims to improve the corrosion resistance of a novel permanent magnet material containing rare earths, boron and iron as main components.
It is an object of the present invention to provide a manufacturing method capable of forming a corrosion-resistant thin film having excellent adhesion and anticorrosion properties on a surface of a permanent magnet material with a uniform thickness without using or leaving a corrosive chemical or the like.

[0010]

According to the present invention, a vaporized material of a thin film material is injected and ionized in a vacuum container and accelerated by an accelerating voltage, and R (where R is at least one of rare earth elements including Y). ) 8 atomic% to 30 atomic%, B2 atomic% to 28 atomic%, Fe42 atomic% to 90 atomic% as main components, and the main phase is tetragonal. A method for producing a permanent magnet having excellent corrosion resistance, which is characterized by forming and coating.

That is, according to the present invention, R (where R is at least one of rare earth elements including Y) is 8 atom% to 30.
Atomic%, B2 atomic% to 28 atomic%, Fe 42 atomic% to 9
Ion vapor deposition thin film formation method (IVD: Ion Va
Por Deposition), Al, Ni,
Metals such as Cr, Cu, Co or alloys thereof, or Si
A method for producing a permanent magnet having excellent corrosion resistance, characterized by forming and coating a corrosion resistant thin film layer of O ₂ , Al ₂ O ₃ , Cr ₂ O ₃ , TiN, AlN, TiC or the like.

The ion vapor deposition thin film forming method (I
VD) injects ionization by injecting an evaporated material obtained by evaporating a raw material for a thin film of a required metal, alloy, or ceramic by an electron gun or arc discharge in a vacuum container, or together with ions extracted from another ion source. It accelerates with a high accelerating voltage, something that is not accelerated adheres to the surface of the permanent magnet body,
The surface of the permanent magnet body is coated with the corrosion-resistant thin film by collision and adhesion of the material irradiated with the ion beam. For example, a known device such as a cluster ion beam device can be used. In the present invention, the thickness of the corrosion resistant thin film formed on the surface of the permanent magnet by the above-mentioned ion vapor deposition thin film forming method (IVD) is preferably 30 μm or less in consideration of magnetic properties and corrosion resistance.

The permanent magnet according to the present invention is characterized by containing a non-magnetic phase (excluding oxides) in a volume ratio of 1% to 50%. In the case of a sintered magnet, the crystal grain size is 1%. ~ 1
The main phase is a compound having a tetragonal crystal structure in the range of 00 μm.

Reason for limiting permanent magnet In the present invention, the rare earth element R used in the permanent magnet is 8 atom% to 30 atom%.
At least 1 of Nd, Pr, Dy, Ho, Tb of
Seed, or even La, Sm, Ce, Gd, Er,
At least one of Eu, Pm, Tm, Yb, Lu, Y
Those containing seeds are preferred. Further, although one of R is usually sufficient, a mixture of two or more kinds (Misch metal, didymium, etc.) can be practically used for the convenience of availability. It should be noted that this R does not have to be a pure rare earth element, and may contain impurities that are unavoidable in manufacturing within the industrially available range. R (at least one of rare earth elements including Y) is an essential element in the novel permanent magnet, and if it is less than 8 atomic%, the crystal structure becomes a cubic crystal structure having the same structure as α-iron. If high magnetic properties, especially high coercive force cannot be obtained and it exceeds 30 atom%, R
The rich non-magnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet having excellent characteristics cannot be obtained. Therefore, R is in the range of 8 atom% to 30 atom%.

B is an essential element in the novel permanent magnet, and if it is less than 2 atomic%, a rhombohedral structure is formed and a high coercive force (iHc) cannot be obtained. The magnetic phase increases and the residual magnetic flux density (Br)
, The excellent permanent magnet cannot be obtained. Therefore, B is in the range of 2 at% to 28 at%.

Fe is an essential element in the novel permanent magnets, and if the content is less than 42 atomic%, the residual magnetic flux density (B
Since r) decreases and a high coercive force cannot be obtained if it exceeds 90 atom%, Fe is contained in the range of 42 atom% to 90 atom%. Further, in the permanent magnet according to the present invention, substituting a part of Fe with Co can improve temperature characteristics without impairing the magnetic characteristics of the obtained magnet.
When the substitution amount of Co exceeds 50% of Fe, the magnetic characteristics are deteriorated, which is not preferable.

The permanent magnet according to the present invention has R,
In addition to B and Fe, the presence of impurities that are unavoidable in industrial production can be tolerated, but a part of B is 4.0 atomic% or less of C and 3.5.
P of atomic% or less, S of 2.5 atomic% or less, 3.5 atomic%
By substituting at least one of the following Cu with a total amount of 4.0 atomic% or less, it is possible to improve the productivity of the permanent magnet and reduce the cost. At least one of the following additional elements is added to the RB-Fe based permanent magnet because it is effective in improving the coercive force, improving the manufacturability, and reducing the cost. However, since the residual magnetic flux density (Br) is lowered with the addition for improving the coercive force, it is desirable to add the magnetic flux density in the range equal to or more than the residual magnetic flux density of the conventional hard ferrite magnet. 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
Bi of atomic% or less, Nb of 12.5 atomic% or less, 10.
5 atomic% or less Ta, 9.5 atomic% or less Mo, 9.5
W of atomic% or less, Sb of 2.5 atomic% or less, Ge of 7.0 atomic% or less, Sn of 3.5 atomic% or less, 5.5 atomic%
At least one of the following Zr and 5.5 at% or less of Hf is added and contained. However, in the case of containing two or more of them, the maximum content is the atomic% or less of that of the additional elements having the maximum value. By including it, it becomes possible to increase the coercive force of the permanent magnet.

The main phase of the crystal phase is a tetragonal system, which is essential for producing a sintered permanent magnet having excellent magnetic properties. Further, the permanent magnet according to the present invention can be magnetically anisotropic magnet obtained by press molding in a magnetic field, and can be magnetically isotropic magnet by press molding in a non-magnetic field.

The permanent magnet according to the present invention has a coercive force iHc.
≧ 1 kOe, residual magnetic flux density Br> 4 kG, the maximum energy product (BH) max is equal to or greater than that of hard ferrite, and in the most preferable composition range, (BH) max
≧ 10 MGOe, and the maximum value reaches 25 MGOe or more. Further, when the main component of R of the permanent magnet according to the present invention occupies 50% or more of the light rare earth metal, R 12 atom% to 20 atom%, B 4 atom% to 24 atom%, Fe65
When the main component is atomic% to 82 atomic%, the magnetically anisotropic sintered magnet exhibits the best magnetic properties, and particularly when the light rare earth metal is Nd, (BH) max is the maximum value. Reaches over 35 MGOe.

[0020]

The present invention is a manufacturing method for forming a strong and stable corrosion-resistant thin film layer having a uniform film thickness on the surface of the present permanent magnet material in order to suppress oxides formed on the surface. The formed corrosion-resistant thin film layer suppresses oxidation of the surface of the magnet body, does not deteriorate magnetic properties, and does not use or leave corrosive chemicals, etc., and has the advantage of being stable for a long period of time. .. further,
The permanent magnet in the present invention mainly uses light rare earths rich in resources centered on Nd and Pr as R, Fe,
By using B and R as the main components, it is possible to inexpensively obtain an excellent permanent magnet having an extremely high energy system of 25 MGOe or more, a high residual magnetic flux density, a high coercive force, and a high corrosion resistance.

[0021]

【Example】

Example As a starting material, electrolytic iron having a purity of 99.9%, B19.4
%, With the balance being Fe and Al, Si, C and other ferroboron alloys made of Nd and Dy metals with a purity of 99.7% or more, and high-frequency melting them, then casting in a water-cooled copper mold, 15Nd1.5Dy8B75.5F
An ingot having a composition of e (atomic%) was obtained.

Then, the ingot was roughly crushed by a stamp mill and then crushed by a ball mill to obtain a fine powder having a particle size of 3 μm. Insert this fine powder into the mold and press at 12 kOe
Oriented in a magnetic field of 1.5 t / cm in the direction perpendicular to the magnetic field
Molded at a pressure of ² . The obtained molded body is 1100 °
Sintered under the conditions of C for 1 hour in Ar, then allowed to cool, and then subjected to aging treatment in Ar at 600 ° C. for 2 hours,
A permanent magnet was produced.

From the obtained permanent magnet, a test piece was cut into a size of 20 mm outer diameter × 10 mm inner diameter × 1.5 mm thickness.
Degree of vacuum in the vacuum vessel in which the above test piece is inserted 1 × 10 ^-2 T
At or or less, Ti flakes of the coating material are vaporized by arc discharge, and N ₂ gas is pulled out at a voltage of 40 k.
V, ionization current 100mA, beam size 4x10c
The TiN thin film was formed on the surface of the test piece by accelerating as N ₂ gas ions at m ² and performing Ti evaporation and N ₂ gas ion irradiation for 3 hours. The thickness of the TiN thin film at this time was 5 μm.

The test piece was subjected to a corrosion resistance test and a TiN thin film adhesion strength test after the corrosion resistance test. In addition, the magnetic characteristics before and after the corrosion resistance test were measured. The test results and measurement results are shown in Table 1.

Comparative Example Further, as a comparative example, the above test piece was treated with trichlene 3
After solvent degreasing for 5 minutes, 5% NaOH at 60 ° C for 3 minutes, and alkaline degreasing for 3 minutes, pickling with 2% Hcl at room temperature for 10 seconds, current density 4A / dm ² in Watt bath, bath Electrolytic nickel plating was performed at a temperature of 60 ° C. for 20 minutes to obtain a comparative test piece (Comparative Example 1) having a nickel plating layer with a thickness of 10 μm on the surface. This comparative test piece was subjected to the same tests and measurements as in the example, and the results are shown in Table 1.
Shown in.

[0026]

[Table 1]

[0027]

As is apparent from the test and measurement results of Table 1, the corrosion-resistant thin film layer according to the ion deposition thin film forming method (IVD) of the present invention has a remarkably excellent film thickness as compared with the comparative example. Because of the high uniformity, the oxidation of the permanent magnet body is reliably prevented, and the magnetic characteristics do not deteriorate.
It can be seen that the magnetic properties are remarkably improved as compared with the comparative example.

Claims (1)

[Claims] 1. An atomized material vapor for a thin film is jetted and ionized in a vacuum vessel and accelerated by an accelerating voltage, and R (where R is at least one of rare earth elements including Y) is 8 atomic% to 30.
Atomic%, B2 atomic% to 28 atomic%, Fe 42 atomic% to 9
A method for producing a permanent magnet having excellent corrosion resistance, which comprises depositing and ion-irradiating a surface of a permanent magnet having a main phase of tetragonal with 0 atomic% as a main component to form and coat a corrosion-resistant thin film.