JPH0821511B2 - Method of manufacturing permanent magnet with excellent corrosion resistance - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a permanent magnet containing R (R is at least one of rare earth elements including Y), B and Fe as main components, and the permanent magnet is formed by vapor phase plating. The present invention relates to a method of manufacturing a rare earth / boron / iron-based permanent magnet having improved corrosion resistance.

[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 ferrites containing iron oxide as the main component have 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 extremely 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 previously proposed a Fe—BR type permanent magnet (R is at least one of rare earth elements including Y) as a new high-performance permanent magnet containing no expensive Sm or Co (special feature). (Kaisho 59-46008). This permanent magnet is an excellent permanent magnet that uses a resource-rich light rare earth centering on Nd and Pr as R and has an extremely high energy product of 25 MGOe or more with Fe as a main component.

However, since the Fe-BR type permanent magnet having the above-mentioned excellent magnetic characteristics contains iron and a rare earth element which are easily oxidized in the air as main components, when incorporated in a magnetic circuit, 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.

[0006]

Therefore, in order to improve the corrosion resistance of the above Fe-BR type permanent magnet, the applicant first applied the corrosion-resistant metal plating to the surface of the magnet body by electroless plating or electrolytic plating. Layer-coated permanent magnet (Japanese Patent Application No. 58-162350)
No.)), and a permanent magnet whose surface is coated with a corrosion resistant resin layer by a spray method or a dipping method (Japanese Patent Application No. 58-171907 (Japanese Patent Application Laid-Open No. 60-63901).
No.))

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

Further, since the resin coating by the latter 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 the shape is particularly complicated. It is difficult to apply a coating having a uniform thickness to the magnet body, and the resin coating thickness becomes non-uniform in the dipping method, resulting in a problem of poor product dimensional accuracy.

An object of the present invention is to provide a method for producing a Fe-BR permanent magnet having improved corrosion resistance of a new permanent magnet material containing a rare earth / boron / iron as a main component and a tetragonal main phase. It is possible to provide a corrosion-resistant thin film having excellent adhesion and corrosion resistance with a uniform thickness on the surface of the magnet material instead of the wet plating treatment in which a corrosive chemical or the like is used and left.
-The purpose of the present invention is to provide a method for manufacturing a BR permanent magnet.

[0010]

The present invention is based on R (provided that R
Is at least one of rare earth elements including Y) 8 atomic%
-30 atom%, B 2 atom-28 atom%, Fe 42
Vacuum deposition method, ion sputtering method, ion plating method, ion vapor deposition thin film formation method (IVD), or plasma vapor deposition thin film on the surface of a permanent magnet whose main phase is a tetragonal phase with atomic% to 90 atomic% as a main component. Forming method (CV
Al, Ni, Cr, C by vapor phase plating treatment such as D)
Metals such as u, Co, or alloys thereof, or Si
A method for producing a permanent magnet having excellent corrosion resistance, characterized in that a corrosion-resistant vapor-phase plated layer of O ₂ , Al ₂ O ₃ , Cr ₂ O ₃ , TiN, AlN, TiC or the like is applied.

The vapor phase plating method for forming the corrosion resistant vapor phase plating layer on the surface of the magnet material in the present invention is a vacuum vapor deposition method, an ion sputtering method, an ion plating method, an ion vapor deposition thin film forming method (IVD), or plasma vapor deposition. A thin film forming method (CVD) or the like can be adopted. In the present invention, the thickness of the corrosion-resistant vapor phase plating layer on the surface of the Fe-BR permanent magnet formed by the various vapor phase plating layer forming treatments described above is 3 in consideration of magnetic characteristics and corrosion resistance.
A thickness of 0 μm or less is preferable.

In the vacuum vapor deposition method, the coating substance is heated in a vacuum by a resistance heating method, an electron beam method, an induction heating method or the like to form an atomic, molecular or fine particle, which is applied to the surface of the permanent magnet body to be coated. It is a method of forming a corrosion resistant thin film made of the metal, alloy or compound described above.

In the ion sputtering method, an argon gas is introduced into a vacuum container, a discharge is generated by a sputtering power source, and the ionized argon gas is accelerated by an electric field to collide with a target material that is a coating material of a cathode, thereby causing a target. It is a method of striking out material atoms and forming the corrosion-resistant thin film on the surface of the adhered permanent magnet that constitutes the anode.

The ion plating method is a resistance heating method,
Atomic state by heating by electron beam method, induction heating method, etc.
Molecular or fine particles are made to collide with thermal electrons to be ionized, and the traveling ionized particles collide with other vaporized particles due to the electric field distribution to further increase the number of ionized particles, and these ionized particles are attracted to the electric field to cause the cathode. Is a method of forming the corrosion-resistant thin film by adhering to the surface of the permanent magnet constituting the.

Ion Deposition Thin Film Forming Method (IVD: Ion
Vapor Deposition) is a method in which an evaporated material evaporated by an electron gun, an arc discharge, etc. and ions extracted from an ion source are accelerated at a high accelerating voltage at the same time, and attached and irradiated at a certain ratio. It is a method of forming the corrosion resistant thin film on the surface of a permanent magnet body.

In the plasma deposition thin film forming method (CVD), a raw material gas for a thin film is introduced into a vacuum container, a constant pressure is maintained by using a vacuum pump, high frequency power is applied to an electrode to discharge, and plasma chemical It is a method of forming the corrosion resistant thin film on the surface of the permanent magnet body by a reaction.

Reasons for limiting the permanent magnet The rare earth element R used in the permanent magnet of the present invention is 8 atom%
-30 atom% of at least one of Nd, Pr, Dy, Ho, Tb, or further La, Sm, Ce, G
Those containing at least one of d, Er, Eu, Pm, Tm, Yb, Lu and Y are preferable. Usually, only one of R is sufficient, but in practice, a mixture of two or more (Misch metal, didymium, etc.) can be used for reasons such as 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 (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%, it has a cubic crystal structure having the same crystal structure as α-iron. Therefore, high magnetic characteristics, especially high coercive force cannot be obtained. When it exceeds 30 atomic%, the R-rich nonmagnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics is obtained. I can't. Therefore, R is 8 atom% to 3
The range is 0 atomic%.

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. Increased magnetic phase, 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 new permanent magnets of the above system, and if it is less than 42 atomic%, the residual magnetic flux density (B
r) decreases, and if it exceeds 90 atomic%, a high coercive force cannot be obtained. Therefore, Fe is contained at 42 at% to 90 at%. Further, in the permanent magnet alloy according to the present invention, substituting a part of Fe with Co can improve the temperature characteristics without deteriorating the magnetic characteristics of the obtained magnet. If it exceeds 50%, on the contrary, 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%
Improving the manufacturability of the permanent magnet by substituting at least one of the following Cu with a total amount of 4.0 atomic% or less,
The price can be reduced.

At least one of the following additive elements is added to the RB-Fe based permanent magnet because it is effective in improving the coercive force and the like, 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 preferable to add the residual 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%
Cr below, Mn below 8.0 at%, Bi below 5 at%, Nb below 12.5 at%, Ta below 10.5 at%, Mo below 9.5 at%, 9.5 below. W of atomic% or less, Sb of 2.5 atomic% or less, Ge of 7 atomic% or less,
3.5 atomic% or less Sn, 5.5 atomic% or less Zr,
At least one of Hf of 5.5 atomic% or less is additionally contained. However, when two or more kinds of Hf are contained, the maximum content thereof is at most atomic% of the additive element having the maximum value.

In the Fe-BR type permanent magnet of the present invention, it is essential that the main phase is tetragonal, and the volume ratio is 1% to.
It is characterized by containing 50% of non-magnetic phase (excluding oxide phase), and in the case of a sintered magnet, the crystal grain size is 1 to 100 μm.
A sintered permanent magnet having excellent magnetic properties can be obtained by using a compound having a tetragonal crystal structure of as a main phase and fine and uniform alloy powder. Further, the permanent magnet of 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. Therefore, the Fe-B-R permanent magnet of the present invention mainly uses a light rare earth element rich in resources centering on Nd and Pr as R, Fe,
An excellent permanent magnet having an extremely high energy product of 25 MGOe or more, a high residual magnetic flux density, a high coercive force, and high corrosion resistance due to B and R as main components and a tetragonal phase as a main phase. It can be obtained at low cost.

The permanent magnet according to the present invention has a coercive force iHc.
≧ 1 kOe, residual magnetic flux density Br> 4 kG, and the maximum energy product (BH) max is equal to or higher than that of hard ferrite. In the most preferable composition range, (BH) ma
x ≧ 10 MGOe, and the maximum value reaches 25 MGOe or more. Further, when the main component of R of the permanent magnet of the present invention occupies 50% or more of the light rare earth metal, R 12 atom% to 20 atom%, 4 atom% to 24 atom%, Fe 65 atom% to 82 atom%, When the main component is, the magnetically anisotropic sintered magnet exhibits the best magnetic characteristics, and particularly when the light rare earth metal is Nd, the maximum value of (BH) max reaches 35 MGOe or more.

[0025]

The present invention is based on Fe-B in which the main phase is a tetragonal phase.
In order to suppress oxides formed on the surface of the R-based permanent magnet material, a corrosion-resistant vapor-phase plated layer having a uniform thickness, strong and stable is formed on the surface of the magnet material by vapor-phase plating treatment. By applying the vapor phase plating layer, oxidation of the surface of the magnet body is suppressed, the magnetic properties do not deteriorate, and since corrosive chemicals such as wet plating are not used or left, the magnetic properties Has the advantage of being stable over the long term.

[0026]

Example 1 As a starting material, electrolytic iron having a purity of 99.9%, B19.4
%, And the balance is Fe and Al, Si, C and other ferroboron alloys, Nd with a purity of 99.7% or more is used, and these are high-frequency melted, and then cast in a water-cooled copper mold to obtain 15Nd8B77Fe (atoms). %) Was obtained. After that, 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. The fine powder was inserted into a mold, 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 . The obtained molded body is sintered at 1100 ° C. for 1 hour in Ar, then allowed to cool, and further Ar
A permanent magnet was produced by aging treatment at 600 ° C. for 2 hours. 20 mm outer diameter x 1 inner diameter from the obtained permanent magnet
A test piece was cut into a size of 0 mm × thickness of 1.5 mm.

Next, the above-mentioned test piece was put in a vacuum container having a degree of vacuum of 1 × 10 ^-5 Torr, and pretreatment was carried out at 350 ° C. for 3 hours.
After heating for 0 minutes and lowering the temperature to 300 ° C., a Ni piece having a purity of 99.99% or more with a size of 10 mmφ × 10 mm of the coating material is irradiated with an electron beam of 0.6 A, 8 kV for 30 minutes to heat and evaporate. A Ni thin film was vacuum-deposited on the test piece. The thickness of the Ni thin film formed on the surface of the permanent magnet of the test piece was 5 μm. The test piece was subjected to a corrosion resistance test and a Ni thin film adhesion strength test after the corrosion resistance test. Also,
The magnetic properties before and after the corrosion resistance test were measured. The test results and measurement results are shown in Table 1.

Comparative Example 1 For comparison, the test pieces were solvent degreased with trichlene for 3 minutes, alkali degreased with 5% NaOH at 60 ° C. for 3 minutes, and then with 2% HCl at room temperature for 10 seconds. Acid-washed with a Watt bath, current density 4 A / dm ² , bath temperature 60
A comparative test piece (Comparative Example 1) having a nickel plating layer with a thickness of 10 μm on the surface was obtained by performing electric nickel plating under the conditions of ° C and 20 minutes. This comparative test piece was subjected to the same tests and measurements as in Example 1 above, and the results are shown in Table 1 as in Example 1.

The corrosion resistance test was evaluated based on the appearance of the test piece when the test piece was left in an atmosphere of a temperature of 60 ° C. and a humidity of 90% for 500 hours. For the adhesion strength test, the above-mentioned test piece after the corrosion resistance test is 1 m with an adhesive tape.
The mesh portion at intervals of m was pulled, and it was evaluated whether or not the thin film layer was peeled off (number of unpeeled cells / total number of cells).

Example 2 Using the same test piece as in Example 1, the degree of vacuum was 1 × 10 ⁻⁵ To.
The above test piece was placed in a vacuum chamber of rr, and Ar gas was further introduced until it reached 1.2 × 10 ^-2 Torr, and then 1
A discharge is generated in Ar gas at 50 W, and C is applied to the target material.
Using an o-18.5 Cr alloy piece, sputtering was performed for 5 hours to form a thin film having the same composition as the target material on the surface of the test piece. The thickness of the thin film formed on the surface of the test piece is 5μ
It was m. The test piece was subjected to the corrosion resistance test of the same method as in Example 1 and the adhesion strength test of the vapor phase thin film after the corrosion resistance test. In addition, the magnetic properties before and after the corrosion resistance test were measured. The test results and measurement results are shown in Table 1.

Example 3 Using the same test piece as in Example 1, the degree of vacuum was 1 × 10 ⁻⁵ To.
Put the above test piece in a vacuum chamber of rr, and 0.8 Torr
After performing reverse sputtering in Ar gas at a voltage of 400 V for 1 minute, as pretreatment, heating is performed at 350 ° C. for 30 minutes and the temperature is lowered to 300 ° C., and then a target material made of 3-5 mmφ granular fused quartz is used. When heated, the fused quartz becomes molecular, and thermionic electrons collide with it to be ionized. Due to the electric field distribution, the SiO ₂ ionized particles collide with other vaporized particles to further increase the SiO ₂ ionized particles,
These ionized particles were attracted to the electric field and adhered to the test piece constituting the cathode, and a SiO ₂ thin film was formed on the surface of the test piece. The thickness of the thin film formed on the surface of this test piece was 5 μm. The conditions of the above-mentioned ion plating are as follows: a test piece having a voltage of 1 kV, an ionization voltage of 100 V, 80 to 90 mA,
It was a condition of processing for 40 minutes. Example 1
The corrosion resistance test of the same method and the adhesion strength test of the vapor phase thin film after the corrosion resistance test were performed. In addition, the magnetic properties before and after the corrosion resistance test were measured. The test results and measurement results are shown in Table 1.

Example 4 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, and Nd and Dy metals with a purity of 99.7% or more are used, and these are high-frequency melted and then cast in a water-cooled copper mold to produce 15Nd1. .5Dy8B75.5Fe
An ingot having a composition of (atomic%) was obtained. After that, 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. This fine powder was inserted into a mold, oriented in a magnetic field of 12 kOe, and molded in a direction perpendicular to the magnetic field at a pressure of 1.5 t / cm ² . The obtained compact was sintered under the conditions of 1100 ° C. for 1 hour in Ar, then allowed to cool, and further subjected to an aging treatment in Ar at 600 ° C. for 2 hours to produce a permanent magnet. From the obtained permanent magnet, outer diameter 20 mm × inner diameter 10 mm × thickness 1.5 m
A test piece was cut into m size.

The degree of vacuum in the vacuum vessel in which the above test piece was inserted was 1 × 10 ^-2 Torr or less, Ti thin pieces of the coating material were evaporated by arc discharge, and N ₂ gas was drawn out at a voltage of 40 kV and an ionization current was 100 mA. With a beam size of 4 × 10 cm ^2, it is accelerated as N ₂ gas ions, and Ti
A TiN thin film was formed on the surface of the test piece by the ion vapor deposition thin film forming method in which evaporation and N ₂ gas ion irradiation were performed for 3 hours. At this time, the thickness of the TiN thin film on the surface of the test piece was 5 μm.
The test piece was subjected to the same corrosion resistance test as in Example 1 and the adhesion strength test of the thin film after the corrosion resistance test. In addition, the magnetic properties before and after the corrosion resistance test were measured. The test results and measurement results are shown in Table 1.

Comparative Example 2 As a comparative example, the above test piece was solvent degreased with trichlene for 3 minutes, alkali degreased with 5% NaOH at 60 ° C. for 3 minutes, and then with 2% HCl at room temperature for 10 seconds. Acid-washed with a watt bath, current density 4 A / dm ² , bath temperature 6
A comparative test piece (Comparative Example 2) having a nickel plating layer with a thickness of 10 μm on the surface was obtained by performing electric nickel plating under the conditions of 0 ° C. and 20 minutes. Example 4 was applied to this comparative test piece.
The same tests and measurements as in Example 1 were performed, and the results are also shown in Table 1.

Example 5 The same test piece as in Example 4 was used, and a flow rate of SiH ₄ gas and N ₂ O gas was 10 at the same time in a vacuum container in which the test piece was inserted.
The plasma vapor deposition thin film forming method of depositing a SiO ₂ thin film on the surface of a test piece preheated to 200 ° C. was carried out for 3 hours by discharging at 200 W with high frequency plasma of 13.56 MHz and feeding at 0 ml / min. 5μ thickness on the surface of the test piece
m SiO ₂ thin film was formed. The test piece was subjected to the same corrosion resistance test as in Example 1 and the adhesion strength test of the thin film after the corrosion resistance test. In addition, the magnetic properties before and after the corrosion resistance test were measured. The test results and measurement results are shown in Table 1.

[0036]

[Table 1]

[0037]

According to the present invention, the surface of a permanent magnet having a required composition of R, B, and Fe as main components and a main phase of a tetragonal phase,
The corrosion resistance vapor phase plating layer is provided by vapor phase plating treatment such as vacuum deposition method, ion sputtering method, ion plating method, etc. The vapor plating layer is
Compared with each comparative example by the wet plating treatment, the film thickness is the required thickness and the outstanding uniformity is obtained, and further excellent corrosion resistance and high coating adhesion strength are obtained.
It can be seen that the permanent magnet body is reliably prevented from being oxidized, the magnetic characteristics are not deteriorated after the corrosion resistance test, and the magnetic characteristics are remarkably improved as compared with each comparative example.

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Claims (1)

[Claims] 1. R (where R is at least one of rare earth elements including Y) 8 atom% to 30 atom%, B 2 atom%
.About.28 at%, Fe 42 at.% To 90 at.% As a main component, and a main phase is a tetragonal phase. The surface of the permanent magnet is characterized in that a corrosion resistant vapor phase plating layer is deposited by vapor phase plating treatment. A method for manufacturing a permanent magnet having excellent corrosion resistance.