JPH0616445B2 - Permanent magnet material and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to an Fe-BR system in which deterioration of magnetic properties due to grinding of a surface of a sintered permanent magnet or the like is prevented and deterioration of magnetic properties over time is prevented. Permanent magnet, especially 1.0mm thickness
The following relates to a high-performance permanent magnet material and a method for manufacturing the same.

BACKGROUND ART At present, there is a demand for a permanent magnet material that has high magnetic properties and is inexpensive, and there is a strong demand for a permanent magnet material that is rich in resources and that can be stably supplied in the future with a composition element. In addition, as a new high-performance permanent magnet containing no expensive Sm or Co, an Fe-BR type permanent magnet (R is at least one of rare earth elements including Y) is proposed (Japanese Patent Laid-Open No. 59-460).
08, JP 59-64733, JP 59-89401, JP 59
-132104). This permanent magnet is an excellent permanent magnet that uses a resource-rich light rare earth such as Nd or Pr as R and has an extremely high energy product of 20 MGOe or more with Fe as a main component.

Recently, as the performance and size of magnetic circuits have increased, Fe-B-
R-based permanent magnet materials are attracting more and more attention, and the thickness is 1.0 m.
There has been a demand for Fe-BR type permanent magnet materials for small or thin objects having a size of m or less.

In order to manufacture a permanent magnet material for such an application, a molded or sintered small or ultra-thin sintered magnet body is used to remove surface irregularities or distortion, or to remove a surface oxide layer, In order to be incorporated in a circuit, it is necessary to cut the entire surface or required surface of the magnet body.

However, such Fe-BR permanent magnet materials (15.5
When Nd 7.5B77Fe) is ground, for example, when it is processed to have a product thickness of 20 mm to 1 mm or less, there is a problem that each magnetic property is deteriorated as shown by the curve b in FIGS. 1 to 3.

In order to prevent the deterioration of the magnetic characteristics due to such processing, the applicant has previously proposed that the R'thin film layer (R 'is Nd, Pr, Dy, Ho, Tb) on the surface to be ground of the magnet body. After forming at least one) by vapor deposition etc., heat treatment is proposed to improve the deterioration of magnetic properties due to the work-affected layer (Japanese Patent Application No. 60-21).
No. 6047).

However, since the above R'thin film layer is very easily oxidized,
Depending on the operating environment conditions, the R'thin film layer on the surface of the magnet may be oxidized and the magnetic characteristics may be deteriorated again.

An object of the present invention is to prevent deterioration of magnetic properties associated with cutting of a sintered magnet body for a small or ultra-thin material, in a new permanent magnet material mainly containing rare earth, boron and iron, and The present invention is directed to a permanent magnet material having improved magnetic characteristics over time and a manufacturing method thereof.

As a result of various studies on the coercive force of the Fe-BR system permanent magnet material, the inventors found that the magnitude of the coercive force of the magnet body is due to the difference in the grain boundary structure rather than in the crystal grains. When the polished sintered magnet surface is examined with an optical microscope using the Kerr effect to investigate the domain reversal mechanism in detail, the magnetization reversal on the surface of the magnet body is less than 1/2 of the coercive force inside the magnet body. The reason is that the coercive force of the crystal group of the processed surface first layer of the sintered magnet body is low because it occurs in a very low magnetic field of , The grain boundary phase) does not exist. Here, the grain boundary phase is one in which a phase containing Nd as a main component covers the surface of the main phase and has a flat interface on an atomic scale.

Providing the grain boundary phase, which was first discovered by the inventor, for producing a high coercive force on the processed crystal group of the sintered magnet body as a grain boundary phase having an optimum thickness and a special cubic system structure. Is not easy in the usual way, but Ce, La,
By forming a thin film layer containing at least one of Nd, Pr, Dy, Ho, and Tb as a main component, and then performing a specific heat treatment in a vacuum or an inert atmosphere, the surface to be ground of the sintered body is ground. The deteriorated layer and lattice defects composed of crystal grains having a low coercive force are formed as a modified layer by a diffusion reaction between the thin film layer and the deteriorated layer,
In addition, Ti, W, Pt, Au,
By depositing a metal or alloy layer composed of at least one of Cr, Ni, Cu, Co, Al, Ta, Ag, and Pb, Fe-
The inventors have found that the coercive force of the BR permanent magnet material and the squareness of the demagnetization curve can be improved and improved, and the secular change of the magnetic properties can be improved, and the present invention has been completed.

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 12 to 20 atom%, 4 to 20 atom% of B, 65 to 81 atom% of Fe as a main component, and the main phase of which is a tetragonal phase. A modified layer consisting of an R'thin film layer (R 'is at least one of Ce, La, Nd, Pr, Dy, Ho and Tb) deposited on the ground surface, and further on the R'thin film layer. Metal layer or alloy layer (Ti, W, Pt, Au, Cr, N
A permanent magnet material having an antioxidation layer made of at least one of i, Cu, Co, Al, Ta, Ag, and Pb, but excluding Al alone).

Further, on the surface to be ground of the sintered magnet body whose main phase is a tetragonal phase, R ′ thin film layer (R ′ is Ce, La, Nd, Pr, D
at least one of y, Ho, and Tb), and after applying the R ′ thin film layer, or on the R ′ thin film layer,
After depositing an antioxidant layer made of a metal layer or an alloy layer made of at least one of Ti, W, Pt, Au, Cr, Ni, Cu, Co, Al, Ta, Ag, and Pb, further vacuum or 400 ℃ ~ 900 in an inert atmosphere
A permanent magnet material, characterized in that it is subjected to heat treatment at 1 ° C. for 1 minute to 3 hours to form a work-affected layer on the surface to be ground as a modified layer, and an antioxidant layer is provided on the modified layer. It is a manufacturing method.

The permanent magnet material of 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.

Therefore, the present invention mainly uses light rare earths rich in resources centered on Nd or Pr as R, Fe, B,
Fe containing R as the main component has an extremely high energy product of 20 MGOe or more, a high residual magnetic flux density and a high coercive force, and prevents deterioration of magnetic characteristics due to grinding.
The -BR permanent magnet material can be obtained at low cost.

That is, according to the present invention, in the grinding of the Fe-BR permanent magnet material (15.5Nd 7.5B77Fe), for example, by providing the Nd thin film layer on the surface to be ground and making the altered layer a modified layer, Even if the product is processed to have a thickness of 20 mm to 1 mm or less, the magnetic properties are improved as compared with the comparative example (curve b) in which the Nd thin film layer is not provided as shown by the curve a in FIGS. In addition, it has an effect of preventing the deterioration of the magnetic characteristics due to the grinding process.

Further, since the metal or alloy layer deposited on the R'thin film layer is electrochemically noble or forms a passive oxide layer on the surface thereof, it has excellent oxidation resistance and R'thin film layer. The bond strength with is also excellent.

In the present invention, the surface to be ground of the sintered magnet body,
R '(R' is at least one of Ce, La, Nd, Pr, Dy, Ho and Tb) and Ti, W, Pt, Au, Cr, N
Vacuum deposition, ion sputtering, ion plating, ion deposition thin film can be used for depositing an antioxidant layer made of a metal layer or an alloy layer made of at least one of i, Cu, Co, Al, Ta, Ag and Pb. A thin film forming method such as a forming method (IVD) or a plasma deposition thin film forming method (EVD) can be appropriately selected and used.

The thickness of the thin film layer is preferably 0.1 μm to 30 μm,
When the thickness of the thin film layer is less than 0.1 μm, it is not preferable because a uniform film is not formed and the rare earth metal of the thin film layer is oxidized and lost during the heat treatment, and when the thickness exceeds 30 μm,
This is disadvantageous in that it requires a long time during vapor deposition, resulting in high cost, and that an unnecessary gap is formed in the magnetic circuit as the film thickness increases, and the effect of modifying the surface layer is saturated. Not preferable.

The thickness of the metal or alloy layer formed on the thin film layer is 0.
If it is less than 1 μm, it is difficult to form a uniform film, and there is no effect of improving the secular change of magnetic properties. If it exceeds 30 μm, it takes a long time for vapor deposition and the magnetic property increases as the film thickness increases. It is not preferable because it forms an unnecessary gap in the circuit.

Further, in the present invention, Ce, L having a thickness of 0.1 μm to 30 μm
After forming a thin film layer containing at least one of a, Nd, Pr, Dy, Ho, and Tb as a main component, or after depositing an antioxidant layer made of the above metal or alloy layer, a vacuum or an inert atmosphere is provided. The heat treatment is carried out in a vacuum or in an inert atmosphere, and it is necessary to perform heat treatment at 400 ° C. to 900 ° C. for 1 minute to 3 hours at least once. The diffusion reaction results in a modified layer. However, below 400 ° C, the diffusion reaction at the interface is insufficient,
The above effect cannot be obtained, and when the temperature exceeds 900 ° C., the thin film layer is easily oxidized by the vacuum degree obtained by a usual industrial method,
If the heating time is less than 1 minute, the diffusion reaction at the interface is insufficient and the effect of improving the magnetic characteristics is small, and if it exceeds 3 hours, the thin film layer is oxidized due to oxidation. It is not preferable because the effect of improving the characteristics cannot be obtained.

In addition, by performing the heat treatment at least once,
Although the desired effect can be obtained, a multi-step heat treatment may be performed if necessary.

Reasons for Limiting Components of Permanent Magnet Material The rare earth element R used in the permanent magnet material of the present invention occupies 12 atom% to 20 atom% of the composition, but Nd, Pr, Dy, Ho, Tb
At least one of these, or even 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 novel permanent magnet material, and if it is less than 12 atomic%, a cubic crystal structure having the same crystal structure as α-iron precipitates, so that high magnetic properties, particularly high coercive force are obtained. If it exceeds 20 atom%, the R-rich non-magnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics cannot be obtained. Therefore, the rare earth element content is in the range of 12 atom% to 20 atom%.

B is an essential element in the permanent magnet material according to the present invention. If it is less than 4 atomic%, the rhombohedral structure becomes the main phase and a high coercive force (iHc) cannot be obtained. Rich non-magnetic phase increases and residual magnetic flux density (Br)
, The excellent permanent magnet cannot be obtained. Therefore, B is in the range of 4 atom% to 20 atom%.

Fe is an essential element in the above new permanent magnets, 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 81 atom%.
The content is 65 atom% to 81 atom%.

Further, in the permanent magnet material 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 20%, on the contrary, the magnetic properties deteriorate, which is not preferable. The atomic ratio of Co is 5 of the total amount of Fe and Co.
% To 15%, the amount of (Br) increases as compared with the case without substitution, so that it is preferable to obtain a high magnetic flux density.

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 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.

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.

The permanent magnet according to the present invention exhibits a coercive force iHc ≧ 4 kOe and a residual magnetic flux density Br> 4 kG, and has a maximum energy product (BH) max.
Shows a (BH) max ≧ 20MGOe in a preferable composition range,
The maximum value reaches 25MGOe or more.

Further, the main component of R in the permanent magnet material of the present invention is 50%
When the above is a case where a light rare earth metal mainly composed of Nd and Pr is occupied, R12 atom% to 15 atom%, B6 atom% to 9 atom%, Fe
In the composition range of 78 atom% to 80 atom%, (BH) max 35
It shows excellent magnetic properties above MGOe, and its maximum value reaches 42 MGOe or above, especially when the light rare earth metal is Nd.

Examples Example 1 As starting materials, electrolytic iron having a purity of 99.9%, ferroboron alloy, and Nd and Dy having a purity of 99.7% or more were used, and these were mixed and then high-frequency melted.
An ingot having a composition of B 1.5 Dy78Fe was obtained.

Thereafter, this ingot was embrittled by occluding H ₂ gas, coarsely pulverized by a stamp mill, and then finely pulverized by a ball mill to obtain fine powder having an average particle size of 3.0 μm.

Insert this fine powder into the mold, orient in a magnetic field of 20 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 the conditions of 1100 ° C. for 1 hour in an Ar atmosphere to obtain a sintered body having a size of length 20 mm × width 10 mm × thickness 10 mm.

Then, cut out from the sintered body into a test piece measuring 3 mm in length × 4 mm in width × 0.1 mm in thickness so that the direction perpendicular to the magnet orientation direction is included in the plane, and further polish in the same direction to reduce the thickness. Then, a thin plate test piece having a mirror surface and a thickness of 100 μm was obtained.

Next, using Nd metal as a cathode target material, sputtering was performed under the following conditions to deposit an Nd thin film layer having a thickness of about 3 μm on both surfaces of the test piece.

Then, heat treatment was performed at 630 ° C. for 1 hour in a vacuum of 3 × 10 ^-6 Torr.

Furthermore, under the same sputtering conditions, the metals shown in Table 1
It was sputtered to a thickness of μm.

Further, a comparative permanent magnet (Comparative Example 15) was prepared by providing the thin plate test piece with an Nd thin film layer and immediately performing heat treatment under the same conditions without providing a metal layer.

Br, iHc, BHc, Hc of each obtained permanent magnet material
The (BH) max value was measured in an open circuit using a vibrating sample magnetometer (VSM), and the demagnetization rate evaluated by the irreversible demagnetization rate of standing for 10,000 hours in air at room temperature was measured. The results of these measurements are shown in Table 1.

In addition, Comparative Example 13 in Table 1 is a test piece as-polished, and Comparative Example 14 is a bulk property of a large material.

<Sputtering Conditions> Ultimate vacuum; 2 × at 10 ^-6 Torr RF sputtering Ar ^{pressure; 0.2 × 10 -3 Torr~1 × 10} -3 Torr input power; 150 W
(At the time of initial sputtering and at the time of main sputtering) 70W (at the time of reverse sputtering) Sputtering time: 30 minutes for the first sputtering 30 minutes for the reverse sputtering 3 hours for the main sputtering Example 2 13.5Nd 7B 1.5Dy7 manufactured and processed under the same conditions as in Example 1
A magnet sintered body test piece having a composition of 8Fe was coated with an Nd layer having a thickness of 3 μm under the sputtering conditions of Example 1, and the heat-treated thin magnet of Example 1 was used. Sputtered the alloy layer under the same conditions and measured the Br, iHc, BHc, Hc and (BH) max values of the obtained permanent magnet materials in an open circuit using a vibrating sample magnetometer (VSM), Furthermore, the demagnetization rate evaluated by the irreversible demagnetization rate, which was left for 10,000 hours in air at room temperature, was measured. The results of these measurements are shown in Table 2.

The target material for forming the alloy layer is a composite type, and the composition is shown by the area ratio.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the thickness of a permanent magnet test piece and Br. FIG. 2 is a graph showing the relationship between the thickness of a permanent magnet material test piece and iHc. FIG. 3 is a graph showing the relationship between the thickness of a permanent magnet material test piece and (BH) max.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Yamamoto 2-15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka Prefecture Sumitomo Special Metals Co., Ltd. Yamazaki Works (72) Yutaka Matsuura 2 Egawa, Shimamoto-cho, Mishima-gun, Osaka Prefecture -15-17 Sumitomo Special Metals Co., Ltd. Yamazaki Works (56) References JP-A-60-54406 (JP, A) JP-A-61-281850 (JP, A)

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
(At least one of m, Yb, Lu, and Y) 12 atom% to 20 atom%, B4 atom% to 20 atom%, Fe65 atom% to 81 atom% as main components, and the main phase from the tetragonal phase On the surface to be ground of the sintered magnet body consisting of R ', a modified layer composed of an R'thin film layer (R' is at least one of Ce, La, Nd, Pr, Dy, Ho and Tb), and , R ', a metal layer or an alloy layer (Ti, W, Pt, Au, Cr, N) deposited on the thin film layer.
i, Cu, Co, Al, Ta, Ag, Pb, at least one kind, except for Al alone). 2. R (R is at least one of Nd, Pr, Dy, Ho and Tb, or further La, Ce, Sm, Gd, Er, Eu, T
(At least one of m, Yb, Lu, and Y) 12 atom% to 20 atom%, B4 atom% to 20 atom%, Fe65 atom% to 81 atom% as main components, and the main phase from the tetragonal phase After grinding the sintered magnet body, the R'thin film layer (R 'is Ce, La, Nd, Pr,
At least one of Dy, Ho, and Tb), and after applying the R ′ thin film layer, or on the R ′ thin film layer,
After depositing a metal layer made of at least one of Ti, W, Pt, Au, Cr, Ni, Cu, Co, Al, Ta, Ag, and Pb or an antioxidant layer made of a compound metal, further vacuum or Heat treatment was performed in an inert atmosphere at 400 ° C. to 900 ° C. for 1 minute to 3 hours to form a work-affected layer on the surface to be ground as a modified layer and to form an antioxidant layer on the modified layer. A method for producing a permanent magnet material, comprising: