JPH0742553B2 - Permanent magnet material and manufacturing method thereof - Google Patents

Abstract

PURPOSE:To manufacture small articles of permanent magnet material excellent in magnetic properties, by allowing an alloy thin film layer consisting of Ti, etc., and rare earth elements to adhere to the surface to be ground of a sintered magnet body composed principally of rare earth elements, B, and Fe and then by applying heat treatment to the above. CONSTITUTION:The sintered magnet body which is composed mainly of, by atom, 12-20% R (R is one or more elements among Nd, Pr, Dy, Ho, and Tb or further one or more elements among La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu, and Y), 4-20% B, and 65-81% Fe and whose main phase is composed of a tetragonal phase is subjected to grinding work to a thickness of <=about 1mm. Then, the alloy thin film layer consisting of 1.0-50.0% of one or more elements among Ti, W, Pt, Au, Cr, Ni, Cu, Co, Al, Ta, and Ag and the balance R' (R' is one or more elements among Ce, La, Nd, Pr, Dy, Ho, and Tb) is allowed to adhere to the surface to be ground which is subjected further to heat treatment in vacuum or in an inert atmosphere at 400-900 deg.C for 1min-3hr. In this way, a layer deteriorated by working of the worked surface of the surface to be ground is formed into a modified layer and further an oxidation inhibiting layer is formed on the above.

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. Further, 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-
46008, JP-A-59-64733, JP-A-59-89401, JP-A-59-132104). This permanent magnet uses Nd or Pr as R.
It is an excellent permanent magnet that uses light rare earth, which is rich in resources such as, and has an extremely high energy product of 20 MGOe or more with R, B and Fe as the main components.

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 Nd7.5B77Fe) is ground, for example, from a thickness of 20 mm
When processed to a product thickness of 1 mm or less, there was a problem that each magnetic property was deteriorated as shown by the curve b in FIGS.

In order to prevent the deterioration of the magnetic properties due to such processing, the applicant first applied the R'thin film layer (R 'is Nd, Pr, Dy, Ho, Tb on the surface to be ground of the magnet body to prevent deterioration. At least one kind) was formed by vapor deposition and then heat treated to improve the deterioration of the magnetic properties due to the work-affected layer (Japanese Patent Application No. 60-216047).

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 in detail with an optical microscope using the Kerr effect for the reversal mechanism of the magnetic domain, the magnetization reversal of the magnet body surface 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 R
The phase containing as a main component covers the main phase surface 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 by the usual method, but Ti, W, Pt,
At least one of Au, Cr, Ni, Cu, Co, Al, Ta, Ag and R ′
(R'is at least one of Ce, La, Nd, Pr, Dy, Ho, Tb)
By forming an alloy thin film layer made of, and then subjecting it to a specific heat treatment in a vacuum or an inert atmosphere, a deteriorated layer and lattice defects formed of crystal grains with low coercive force on the ground surface of the sintered body, By forming a modified layer by the diffusion reaction between the thin film layer and the altered layer, and further by forming an antioxidant layer on the surface, the coercive force of the Fe-BR permanent magnet material and the square shape of the demagnetization curve are formed. The inventors have completed the present invention by discovering that the magnetic properties can be improved and the secular change in magnetic characteristics can be improved.

That is, 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). 12% to 20 atomic%, B4 atomic% to 20 atomic%, Fe65 atomic% to 81 atomic% as main components, and the main phase is a tetragonal phase on the surface to be ground of the sintered magnet body, Ti, W, Pt, Au, Cr, N
At least one of i, Cu, Co, Al, Ta, Ag is 1.0 atomic% to 5
An alloy layer containing 0.0 atomic% and the balance R '(R' is at least one of Ce, La, Nd, Pr, Dy, Ho, and Tb) is deposited and modified on the surface to be ground. A permanent magnet material having a layer and an antioxidant layer on the surface.

Further, at least one of Ti, W, Pt, Au, Cr, Ni, Cu, Co, Al, Ta and Ag is applied to the surface to be ground of the sintered magnet body whose main phase is a tetragonal phase. After the deposition of an alloy thin film layer containing 1.0 atomic% to 50.0 atomic% and the balance R '(R' is at least one of Ce, La, Nd, Pr, Dy, Ho and Tb), further vacuum Or 400 ℃ to 900 ℃ in an inert atmosphere
A permanent magnet material, characterized in that the work-affected layer of the surface to be ground is made into a modified layer by heat treatment at 1 ° C. for 1 minute to 3 hours, and an antioxidant layer is formed 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 uses Nd as R or further Pr.
Mainly using light rare earths, which are rich in resources, such as
Fe, which contains B, R, as the main components, has an extremely high energy product of 20 MGOe or more, high residual magnetic flux density, 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, when a Fe-BR permanent magnet material (15.5Nd7.5B77Fe) is ground, for example, by providing an alloy thin film layer on the surface to be ground and making the work-affected layer a modified layer. , Even when processed to a product thickness of 20 mm to 1 mm or less, as shown by the curve a in FIGS. 1 to 3, the magnetic properties are improved as compared to the comparative example (curve b) in which the Nd thin film layer is not provided. Therefore, there is an effect of preventing the deterioration of the magnetic characteristics due to the grinding process.

Furthermore, the alloy thin film layer deposited on the surface to be ground is composed of Ti, W, P
By including at least one of t, Au, Cr, Ni, Cu, Co, Al, Ta and Ag, the corrosion resistance is improved as compared with the R'thin film layer alone.

In this invention, the composition of the alloy thin film layer adhered to the specific grinding surface of the sintered magnet body, Ti, W, Pt, Au, Cr, Ni, Cu, Co, Al, T
The content of at least one of a and Ag is 1.0 atom% to 50.0 atom% and the balance is R ′ (R ′ is at least one of Ce, La, Nd, Pr, Dy, Ho and Tb). Ti, W, Pt, Au, Cr, Ni, Cu, Co, A
If at least one of l, Ta and Ag is less than 1.0 atomic%,
If the alloy thin film layer does not have an antioxidant effect, and if it exceeds 50.0 atomic%, the amount of R'in the alloy thin film layer is small, and the effect of the work-affected layer as a modified layer is lost. This is because the metal or alloy reacts with the base sintered magnet body to form a reaction layer that adversely affects the magnetic properties, which is not preferable.

In this invention, vacuum deposition, ion sputtering, ion plating, ion deposition thin film forming method (IVD), plasma deposition thin film is used to deposit the alloy thin film layer having the above composition on the surface to be ground of the sintered magnet body. A thin film forming method such as a forming method (EVD) can be appropriately selected and used.

Further, the thickness of the alloy thin film layer is preferably 0.1 μm to 30 μm, and if the thin film layer thickness is less than 0.1 μm, a uniform coating film is not formed, and the rare earth metal of the thin film layer is oxidized and disappears during heat treatment, which is not preferable. On the other hand, if the thickness exceeds 30 μm, it takes a long time for vapor deposition and the like, resulting in high cost, and it is disadvantageous that an unnecessary gap is formed in the magnetic circuit as the film thickness increases. The modification effect of the surface layer is also saturated, which is not preferable.

In addition, in the present invention, Ti, W having a thickness of 0.1 μm to 30 μm,
At least one of Pt, Au, Cr, Ni, Cu, Co, Al, Ta, Ag, and Pb is contained in an amount of 1.0 atomic% to 50.0 atomic%, and the balance R ′ (R ′ is Ce,
After forming an alloy thin film layer consisting of at least one of La, Nd, Pr, Dy, Ho, and Tb), heat treatment is performed in a vacuum or an inert atmosphere. It is necessary to perform heat treatment at 400 ° C. to 900 ° C. for 1 minute to 3 hours at least once, and the heat treatment forms a modified layer by a diffusion reaction between the thin film layer and the altered layer. However, if the temperature is lower than 400 ° C, the above-mentioned effect cannot be obtained because the diffusion reaction at the interface is insufficient, and if the temperature exceeds 900 ° C, the thin film layer is easily oxidized by the vacuum degree obtained by an ordinary industrial method, and If the heating time is less than 1 minute, the diffusion reaction at the interface is insufficient to improve the magnetic properties, and the effect of improving the magnetic properties is small. It is not preferable because the improvement effect of 1 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 at least one of Nd, Pr, Dy, Ho and Tb, or Furthermore, La, Ce, Sm, Gd, E
Those containing at least one of r, 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 described above, 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, can be obtained. If it exceeds 20 atom%, the R-rich non-magnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet having 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. The rich non-magnetic phase increases and the residual magnetic flux density (B
Since r) is lowered, excellent permanent magnets cannot be obtained.
Therefore, B is in the range of 4 atom% to 20 atom%.

Fe is an essential element in the above new system permanent magnet. If the content is less than 65 atomic%, the residual magnetic flux density Br decreases, and if it exceeds 81 atomic%, a high coercive force cannot be obtained. The content is up 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%, (Br) increases as compared with the case where no substitution is carried out, which is preferable for obtaining 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 (BH) max ≧ 20 MGOe in the preferable composition range, and the maximum value reaches 25 MGOe or more.

Further, the main component of R in the permanent magnet material of the present invention is 50%
The above is the case where the light rare earth metal mainly composed of Nd and Pr occupies R12 atom% to 15 atom%, B6 atom% to 9 atom%, Fe78
(BH) max35MGO when the composition range is from atomic% to 80 atomic%.
It has excellent magnetic characteristics over e, and especially light rare earth metals are N
In the case of d, the maximum value reaches 42 MGOe or more.

Example 1 As a starting material, electrolytic iron having a purity of 99.9%, ferroboron alloy, and Nd, Dy having a purity of 99.7% or more were used, and after mixing these, high-frequency melting was performed, and then cast in a water-cooled copper mold, and 13.5Nd7B
An ingot having a composition of 1.5Dy78Fe 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, from the sintered body, cut out into a test piece measuring 3 mm in length × 4 mm in width × 0.15 mm in thickness so that the direction perpendicular to the orientation direction of the magnet is included in the plane, and further polish in the same direction to reduce the thickness. Then, a 0.1 mm-thick thin plate test piece having a mirror surface was obtained.

Next, using the alloy shown in Table 1 as a cathode target material, sputtering was performed under the following conditions, and about 3 μm was applied to both sides of the test piece.
A thick alloy thin film layer was deposited. Then 3 × 10 ^-6 Torr
Heat treatment was performed at 630 ° C. for 1 hour in vacuum.

Further, a comparative permanent magnet (Comparative Example 6) was prepared by providing a Nd thin film layer on the above thin plate test piece and immediately performing heat treatment under the same conditions.

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

In addition, Comparative Example 5 in Table 1 shows the characteristics of the test piece as it was subjected to the polishing process.

<Sputtering conditions> Ultimate vacuum; 2 × 10 ^-6 Torr Ar pressure during high frequency sputtering; 0.2 × 10 ^-3 Torr to 1 ×
10 ^-3 Torr Input voltage: 150W (during initial sputtering and main sputtering) 70W (during reverse sputtering) Sputtering time: initial sputtering 30 minutes reverse sputtering 30 minutes main sputtering 3 hours Example 2 Manufactured under the same conditions as Example 1, Processed 13.5Nd7B1.5Dy78F
An alloy thin film layer containing Nd as a main component shown in Table 2 was deposited to a thickness of 3 μm on a magnet sintered body test piece having a composition of e under the sputtering conditions of Example 1.

Furthermore, the same heat treatment as in Example 1 was performed, and Br, iHc, BHc, Hc and (BH) max values of the obtained permanent magnet materials were measured 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 thin film layer is a composite type in which the required metal plate is attached to Nd metal, and the composition is shown by the area ratio.

[Brief description of drawings]

1 to 3 are graphs showing the relationship between the thickness of a permanent magnet material test piece and Br, iHc and (BH) max.

Front page continuation (72) Inventor Hitoshi Yamamoto 2-15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka Prefecture Sumitomo Special Metals Co., Ltd. Yamazaki Works (72) Inventor Hiroshi Matsuura 2-15 Egawa, Shimamoto-cho, Mishima-gun, Osaka Prefecture 17 Sumitomo Special Metals Co., Ltd. Yamazaki Manufacturing Co., Ltd. (56) Reference JP-A-62-188745 (JP, A)

Claims (2)

[Claims] 1. R (R is at least one of Nd, Pr, Dy, Ho, Tb or at least one of La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu, Y. 12% to 20 atom%, B4 atom% to 20 atom%, Fe65 atom% to 81 atom% as main components, and the main phase consists of a tetragonal phase. , W, Pt, Au, Cr, N
At least one of i, Cu, Co, Al, Ta, Ag is 1.0 atomic% to 5
An alloy thin film layer containing 0.0 atomic% and the balance R '(R' is at least one of Ce, La, Nd, Pr, Dy, Ho, and Tb) is deposited, and is modified on the surface to be ground. A permanent magnet material characterized by having a quality layer and an anti-oxidation layer on the surface. 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 and Y. 12% to 20 atom%, B4 atom% to 20 atom%, Fe65 atom% to 81 atom% as main components, and the main phase is a tetragonal phase. Ti, W, Pt, Au, Cr, Ni, Cu, Co, Al, Ta, Ag on the machined surface
An alloy thin film layer containing at least one of 1.0 to 50.0 at% and the balance R '(R' is at least one of Ce, La, Nd, Pr, Dy, Ho and Tb) Then, in a vacuum or an inert atmosphere, 400 ℃ ~ 900
A permanent magnet material, characterized in that a work-affected layer on the surface to be ground is formed into a modified layer by heat treatment at 1 ° C. for 1 minute to 3 hours, and an antioxidant layer is formed on the modified layer. Production method.