JPH0646603B2 - Permanent magnet having excellent corrosion resistance and method of manufacturing the same - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Fe-BR permanent magnet excellent in corrosion resistance and a method for manufacturing the same, and prevents deterioration of magnet characteristics due to grinding of a magnet surface. Further, the present invention relates to a Fe-BR permanent magnet having excellent corrosion resistance in which adhesion of a corrosion resistant coating of a magnetic material and deterioration of corrosion resistance due to fine pores in the coating are improved, and a manufacturing method thereof.

Conventional technology Typical representative permanent magnet materials at present are alnico, hard ferrite, and rare earth cobalt magnets, but they are composed of composition elements that have excellent magnetic properties, are inexpensive, are abundant in resources, and can be stably supplied in the future. Permanent magnet materials have long been desired.

The present applicant has previously proposed a Fe-BR-based (R is at least one of rare earth elements including Y) permanent magnet as a new high-performance permanent magnet that does not contain expensive Sm or Co (JP-A-59-59). Four
6008, JP 59-64733, JP 59-89401, JP Sho
59-132104).

This permanent magnet uses light rare earth, which is rich in resources centered on Nd and Pr as R, and contains 25 MGOe containing B and Fe as main components.
As mentioned above, it is an excellent permanent magnet with an extremely high energy product that reaches 45 MGOe or more at the highest.

Recently, Fe-BR based permanent magnet materials have attracted more and more attention as the performance and size of magnetic circuits have been reduced. To produce a permanent magnet material for such use, for example, in the case of a sintered magnet body that has been molded and sintered, in order to remove irregularities and distortion on the surface of the magnet body, or to remove a surface oxide layer, In order to incorporate into the magnetic circuit, it is necessary to cut or grind the entire surface of the magnet body or the required surface.For processing, outer peripheral blade cutting machine, inner peripheral blade cutting machine, surface grinding machine, centerless grinder, lapping machine, etc. Is used.

However, when the Fe-BR permanent magnet material is cut or ground, the Fe-BR permanent magnet material is
Since it contains rare earth elements and iron that are easily oxidized in air and immediately generate stable oxides, an oxide layer is generated due to heat generation or contact between the atmosphere and the processed surface, which causes deterioration of magnetic properties. was there.

Also, when Fe-BR permanent magnet is incorporated in the magnetic circuit,
The oxide generated on the magnetic surface causes a decrease in output of the magnetic circuit and a variation in characteristics between the magnetic circuits, and there is a problem that peripheral devices are contaminated due to the dropping of the surface oxide.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Therefore, in order to improve the corrosion resistance of the Fe-BR permanent magnet, the applicant previously coated a corrosion-resistant metal plating layer on the surface of the magnet body by electroless plating or electrolytic plating. We have proposed a permanent magnet (Japanese Patent Application No. 58-162350) and a permanent magnet whose surface is coated with a corrosion resistant resin layer by a spray method or an immersion method (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 remains in this hole during the plating pretreatment, causing rusting over time. In addition, since the magnet body is inferior in chemical resistance, the magnet surface is corroded during plating, resulting in poor adhesion and corrosion resistance.

In addition, since the latter method of resin coating has directionality, it takes a lot of steps and labor to apply a uniform resin coating on the entire surface of the object to be processed, especially for a deformed magnet body with a complicated shape. It is difficult to apply a coating having a uniform thickness, and the dipping method causes a non-uniform resin coating thickness, resulting in poor product dimensional accuracy.

Therefore, as a method for improving the corrosion resistance of Fe-BR permanent magnets, the inventors have used a thin film forming technique after grid blasting with a hard powder having a specific particle size and hardness on the surface of the sintered magnet body. , And proposed a permanent magnet material (Japanese Patent Application No. 60-110793, Japanese Patent Application No. 60-200890) in which an Al thin film layer is deposited on the surface of the magnet body.

As a result, the Fe-BR permanent magnet has significantly increased corrosion resistance, but the Al thin film is formed by vapor deposition Al particles being deposited on the surface of the magnet body in a vapor deposition method or the like, resulting in insufficient density, There are micropores in the thin film.For example, it is impossible to completely eliminate the micropores even if a chromate film is formed on this thin film, and the Al thin film peels off locally during long-term use. There is a problem that local thin film layer may be cracked or local rust may occur.

The present invention is a novel permanent magnet material mainly composed of rare earth, boron and iron, which improves the deterioration of magnetic properties associated with the grinding process of the magnet body, and further uses or contacts corrosive chemicals. Without improving adhesion and corrosion resistance,
Further, it is an object of the present invention to provide a permanent magnet having a corrosion-resistant thin film layer surface in which fine pores in the thin film are eliminated and having excellent corrosion resistance that can be used for a long time even under extremely harsh environmental conditions, and a method for producing the same.

Means for Solving the Problems The present invention provides R (R is at least one of Nd, Pr, Dy, Ho, and Tb).
(Or at least one of La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu, Y) 10% to 30 atom%, B2 atom% to 28 atom%, Fe65 atom% to Corrosion resistant vapor phase Al or Zn plating layer and chromate coating layer on it are formed on the surface of a permanent magnet body whose main phase is tetragonal phase with 80 atomic% as the main component. A permanent magnet having excellent corrosion resistance, characterized in that it has a resin filled in the micropores of the layer and the chromate coating layer.

Further, the present invention provides R (R is at least one of Nd, Pr, Dy, Ho and Tb, or at least one of La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu and Y. (Comprising seeds) 10% to 30 atom%, B2 atom% to 28 atom%, Fe65 atom% to 80 atom% as main components, and the main phase is a tetragonal phase. A method for producing a permanent magnet having excellent corrosion resistance, which is characterized by performing a chromate treatment after the Al or Zn plating treatment, further impregnating the surface of the magnet with a thermosetting resin, and then performing a thermosetting treatment. Is.

Preferred Embodiments of the Invention In the present invention, a thin film forming method such as vacuum deposition, sputtering, or ion plating is used to deposit a vapor-phase plated thin film layer on the clean surface of the sintered magnet body from which the oxidized surface layer has been removed. Can be selected and used as appropriate. The vapor plating material is preferably Al or a metal or alloy thereof.

Furthermore, the thickness of the thin film layer is preferably 30 μm or less, more preferably 5 μm to 25 μm, in consideration of peeling of the thin film layer, deterioration of mechanical strength, and ensuring of corrosion resistance.
Is the layer thickness.

The thickness of the chromate film deposited on the vapor-phase plated thin film layer is preferably 1 μm to 5 μm, and its appearance is preferably finished from a bright iridescent color to a golden brownish yellowish brown.

In the present invention, as the resin to be impregnated into the micropores of the chromate film and the vapor-phase plated thin film layer, alcohol-soluble and small molecular weight thermosetting phenolic resin is preferable, and the thermosetting conditions include thermosetting impregnation. It can be appropriately selected depending on the type of the resin.

The thermosetting treatment is preferably performed after the surface of the magnet body impregnated with the thermosetting resin is washed with a solvent or water and dried.

Further, as a method of impregnating the thin film micropores with the thermosetting resin, an immersion impregnation method, a vacuum impregnation method, or a vacuum pressure impregnation method can be adopted, and the method is performed in a vacuum or the like so as not to impregnate the micropores with impurities or the like. If so, the means and conditions can be appropriately selected.

In the present invention, grit blasting in which a hard powder having a required shape is jetted together with a pressurized gas onto the surface of the magnet body before the deposition of the vapor phase plating phase is performed by the black skin of the sintered magnet body, the oxide layer or the processing strain. This is an effective treatment because the surface layer such as a layer can be removed to clean the surface and improve the corrosion resistance of the vapor phase plating layer deposited in a later step.

As the amorphous hard powder having a Mohs hardness of 5 or more used for shot blasting, Al ₂ O ₃ system, silicon carbide system, ZrO ₂ system,
High hardness due to powders of boron carbide and garnet
Al ₂ O ₃ based powder is preferable.

If the Mohs hardness of the above-mentioned amorphous hard powder is less than 5, the grinding force is too small and the grinding process takes a long time, which is not preferable.

If the average particle size of the irregular hard powder is 20 μm to 350 μm, the grinding force is too small and it takes a long time to grind if it is less than 20 μm, and if it exceeds 350 μm, the surface of the sintered magnet surface is This is because the roughness becomes too rough and the grinding amount becomes uneven, which is not preferable.

In addition, as the injection condition of irregular hard powder, pressure 1.0kg / cm
^If it is less than ² , the grinding process takes a long time and the pressure is 6.0 kg.
If it exceeds / cm ² , the amount of grinding on the surface of the magnet body becomes non-uniform, and there is concern that the surface roughness will deteriorate.

Further, if the injection time is less than 0.5 minutes, the grinding amount is small and non-uniform, and if it exceeds 60 minutes, the grinding amount on the surface of the magnet body is large and the surface roughness deteriorates, which is not preferable.

Further, as the pressurized fluid for jetting the hard powder, air or an inert gas such as Ar or N ₂ gas can be used, but an inert gas is preferable for preventing the oxidation of the magnet body, and air is also preferable. When used, dehumidified air is desirable.

Further, in the present invention, the permanent magnet body coated with the vapor phase plated thin film layer is subjected to shot peening by injecting a specific powder having a required shape together with a pressurized gas,
This is effective because the air-layer plated thin film layer can be densified to improve the adhesion between the material and the surface thin film layer.

As the shot peening powder, spherical hard powder having a Mohs hardness of 3 or more can be used, and steel balls, glass beads, etc. can be used, as long as they have hardness equal to or higher than the hardness of the deposited vapor phase plating thin film layer. Is preferred.

When the Mohs hardness of the spherical powder for peening is less than 3, it is less than the hardness of the vapor phase plating thin film layer, and the peening effect cannot be obtained, which is not preferable.

Also, the average particle size of the spherical powder for peening is 30 μm to 3000
If the thickness is less than 30 μm, the pressing force against the vapor-phase plated thin film layer is small and the treatment requires a long time.
If it exceeds m, the surface roughness of the sintered magnet body becomes too rough,
This is because the finished surface is not uniform, which is not preferable. A more preferable average particle size is 40 μm to 2000 μm.

Further, as the injection conditions of the spherical powder, if the pressure is less than 1.0 kg / cm ² , the pressing force against the vapor-phase plated thin film layer is small and it takes a long time to process, and if the pressure exceeds 5.0 kg / cm ² , the vapor phase The pressing force to the plating thin film layer becomes non-uniform, resulting in deterioration of surface roughness. Furthermore, if the injection time is less than 1 minute, the entire surface cannot be uniformly processed, and the upper limit of the injection time is the peening process. It depends on the amount and processing conditions, but if it exceeds 60 minutes,
The surface roughness deteriorates, which is not preferable.

Reasons for Limiting Components of Permanent Magnet The rare earth element R used in the permanent magnet of the present invention has a composition of 10
Occupies at least 30 at%, but at least one of Nd, Pr, Dy, Ho, Tb, or even La, Ce, Sm, Gd, Er, Eu, T
Those containing at least one of m, 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 novel permanent magnet, and if it is less than 10 atom%, it has a cubic crystal structure having the same crystal structure as α-iron, so that high magnetic properties, particularly high coercive force cannot be obtained. If it exceeds 30 atomic%, the amount of R-rich nonmagnetic 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 10 atom% to 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, and if it exceeds 28 atomic%, it is a B-rich non-magnetic material. An excellent permanent magnet cannot be obtained because the number of phases increases and the residual magnetic flux density (Br) decreases. Therefore, B is 2
The range is from atomic% to 28 atomic%.

Fe is an essential element in the novel permanent magnet,
If it is less than 65 atom%, the residual magnetic flux density (Br) is reduced, and if it exceeds 80 atom%, a high coercive force cannot be obtained, so Fe is contained in the range of 65 atom% to 80 atom%.

In the permanent magnet according to the present invention, a part of Fe is Co
By replacing with, the temperature characteristics can be improved without impairing the magnetic characteristics of the obtained magnet, but the Co substitution amount is
If it exceeds 20% of Fe, 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 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, 2.5 atom%
At least one of the following S and Cu of 3.5 atomic% or less,
By substituting the total amount by 4.0 atom% or less, it is possible to improve the manufacturability of the permanent magnet and reduce the cost.

At least one of the following additional elements is added to the Fe-BR permanent magnet because it is effective in improving the coercive force and squareness of the demagnetization curve, improving the manufacturability, and lowering the cost. be able to.

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 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.

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

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

Further, the main component of R of the permanent magnet according to the present invention is 50
% Or more when the light rare earth metal mainly composed of Nb and Pr occupies R12 atom% to 20 atom%, B4 atom% to 24 atom%, Fe74
(BH) max35MGO when the main component is atomic% -80 atomic%
It has excellent magnetic characteristics over e, and especially light rare earth metals are N
In case of d, the maximum value reaches 45 MGOe or more.

This invention uses light rare earths rich in resources centered on Nd and Pr as R, has an extremely high energy product of 25 MGOe or more, and a maximum of 45 MGOe or more with B and Fe as main components, and a high residual magnetic flux density. , A high-coercive permanent magnet, a vapor-phase plated thin film and a chromate film which are excellent in permanent corrosion resistance, prevent deterioration of magnetic properties due to grinding processing and an oxide layer, and eliminate micropores to exhibit extremely high corrosion resistance. The Fe-BR permanent magnet with the surface of which is stably deposited can be obtained at low cost.

Action The present invention is to form a chromate coating layer on the thin film layer by applying a chromate treatment after depositing a corrosion-resistant vapor phase plating thin film layer of Al or Zn on the surface of the magnet body by a thin film forming technique. Further, in the atmosphere or in a vacuum or after being evacuated, pressure is applied to impregnate the adhered layer with a thermosetting resin,
After that, a heat curing treatment is performed to eliminate the fine pores of the vapor phase plating layer and the chromate coating, thereby further improving the corrosion resistance of the permanent magnet.

Example As a starting material, electrolytic iron having a purity of 99.9%, ferroboron alloy, using Nd having a purity of 99.7% or more, high-frequency melting after mixing these, then cast in a water-cooled copper mold, 15.0Nd-8.0B-7
An ingot having a composition of 7.0 Fe was obtained.

After that, this ingot was roughly crushed with a stamp mill,
Next, it was finely pulverized by a ball mill to obtain fine powder having an average particle size of 3 μm.

Insert this fine powder into the mold, orient in a magnetic field of 12 kOe,
It was molded in a direction perpendicular to the magnetic field at a pressure of 1.5 t / cm ² .

The obtained molded body was sintered under conditions of 1100 ° C. for 1 hour in an Ar atmosphere to obtain a sintered body having dimensions of length 25 mm × width 40 mm × thickness 30 mm.

Further, two-step aging treatment was performed in Ar at 800 ° C for 1 hour and 630 ° C for 1.5 hours.

In the atmosphere, the above permanent magnet body is diamond # 200 as a grindstone, the rotation speed is 2400 rpm, the feed speed is 5 mm / min, and the length is 5 m.
It was cut into a size of m x width 10 mm x thickness 3 mm.

Furthermore, using an amorphous Al ₂ O ₃ hard powder having an average particle size of 50 μm and a Mohs hardness of 9 to this cut sample, pressure 2.5 kg / cm ² , N
Grit blasting was performed under the condition of spraying for 20 minutes together with the pressurized gas of ² gases to remove the surface layer of the magnet body.

Next, the above sample was put into a vacuum vessel having a vacuum degree of 5 × 10 ⁻⁵ Torr, Ar gas was fed, and 500 V in 1 × 10 ⁻² Torr Ar gas was introduced.
After discharging for 15 minutes at a voltage of, the coating material was an Al plate with a purity of 99.99%, which was heated to ionize the evaporated Al, and these ionized particles were attracted to the electric field to form a cathode. It adhered to the said test piece which comprises, and formed the Al thin film. The thickness of the thin film formed on the surface of the test piece was 15 μm.

The ion plating conditions were a voltage of 1.5 kV and a treatment for 10 minutes.

In addition, the average particle size of 12
Using spherical glass bead powder having a hardness of 0 μm and a Mohs hardness of 6, shot peening was performed under the conditions of a pressure of 1.5 kg / cm ² and a pressurized gas of N ₂ gas for 5 minutes to obtain a test piece.

Furthermore, after shot peening, the magnet sample was
Immersed in a 2% Alodine # 1200 (trade name; manufactured by Nippon Paint Co., Ltd.) solution held for 1 minute, and apply a chromate film in golden color to the surface of the Al thin film layer after peening to obtain a test piece. It was

The test piece was immersed in a thermosetting resin (trade name; Hitanol, manufactured by Hitachi Chemical Co., Ltd.) in a vacuum container of 10 ^-2 Torr, and impregnation time was 3 minutes (present invention example 1) and 5 minutes (present). Invention Example 2)
After the resin is immersed under the conditions of, the surface of the test piece is washed with a solvent and dried at 25 ° C, and further, in air, at 140 ° C.
Heat treatment was performed for 30 minutes.

These test pieces were subjected to a corrosion resistance test and a thin film adhesion strength test 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.

For comparison, a test piece (Comparative Example 3) manufactured under the same conditions as those of the example of the present invention, except that the thermosetting resin was not impregnated,
The as-cut test piece (Comparative Example 4) and the test piece were subjected to solvent degreasing with trichlene for 3 minutes and then with 5% NaOH at 60 ° C.
After alkaline degreasing for 3 minutes at room temperature, pickling with 2% HCl for 10 seconds at room temperature, Watt bath, current density 4A / dm ² , bath temperature 60 ° C
Under the conditions of 20 minutes in the above, the electroless nickel plating was performed to obtain a comparative test piece (Comparative Example 5) having a nickel plating layer with a thickness of 20 μm on the surface.

These comparative test pieces were subjected to the above-mentioned corrosion resistance test, the adhesion strength test of the thin film after the corrosion resistance test, and the magnetic properties before and after the corrosion resistance test, and the results are also shown in Table 1.

The corrosion resistance test was evaluated based on the appearance of the test piece, the adhesion strength, and the magnetic properties before and after the corrosion resistance test when the test piece was left in an atmosphere of 70 ° C. and a humidity of 90% for 1000 hours.

Further, the adhesion strength test was evaluated by breaking each test piece of the present inventions 1 and 2 and Comparative Examples 3 and 5 after the corrosion resistance test and observing a fracture cross-sectional view.

EFFECTS OF THE INVENTION As is clear from Table 1 of the examples, a corrosion-resistant vapor phase plating thin film layer of Al or Zn is deposited on the surface of the Fe-BR magnet body by a thin film forming technique, and then chromate treatment is applied. To form a chromate film layer on the thin film layer, and further pressurize in the air or in a vacuum or after vacuuming to impregnate the adhered layer with a thermosetting resin, and then perform a thermosetting treatment. In this way, the microscopic holes in the vapor phase plating layer and the chromate coating layer are eliminated, and the corrosion resistance of the permanent magnet is further improved. In addition, Fe-BR based permanent magnets exhibiting excellent corrosion resistance and adhesion are obtained, and it is clear that the effect is remarkable.

Claims (2)

[Claims] 1. R (R is at least 1 of Nd, Pr, Dy, Ho, Tb
Or at least one of La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu, Y) 10% to 30 atom%, B2 atom% to 28 atom%, Fe65 atom% to Corrosion resistant vapor phase Al or Zn plating layer and chromate coating layer on it are formed on the surface of a permanent magnet body whose main phase is tetragonal phase with 80 atomic% as the main component. A permanent magnet having excellent corrosion resistance, characterized in that it has a resin filled in the micropores of the layer and the chromate coating layer. 2. R (R is at least one of Nd, Pr, Dy, Ho and Tb.
Or at least one of La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu, Y) 10% to 30 atom%, B2 atom% to 28 atom%, Fe65 atom% to The surface of a permanent magnet body containing 80 atomic% as a main component and a tetragonal phase as the main phase is vapor-phase Al or Zn plated, then chromate treated, and then the surface of the magnet is thermoset. A method for producing a permanent magnet having excellent corrosion resistance, which comprises impregnating a resin with heat and then performing a heat curing treatment.