JPH0663086B2 - Permanent magnet material and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a Fe—B—R system permanent magnet that prevents deterioration of magnet characteristics due to grinding of the surface of a sintered permanent magnet, etc.
In particular, it relates to a high-performance permanent magnet material having a thickness of 1.0 mm or less and a method for manufacturing the same.

BACKGROUND ART Currently, typical permanent magnet materials are alnico, hard ferrite and rare earth cobalt magnets. Rare earth cobalt magnets are used for various purposes because of their outstanding magnetic properties.However, Sm and Co, which are the main components, are both resource-deficient and expensive, and are stable over the long term. It is difficult to supply a large amount.

Therefore, there has been a strong demand for a permanent magnet material that has excellent magnetic properties, is inexpensive, is abundant in resources, and can be stably supplied in the future, and is composed of a composition element.

The present applicant has 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 that does not contain expensive SmCo (Japanese Patent Laid-Open No. 59-59).
-46008, JP-A-59-64733, JP-A-59-89401,
JP-A-59-132104). This permanent magnet has Nd as R and
Using resource-rich light rare earth materials such as Pr, it shows an extremely high energy product of 2MGOe or more as the main component of Fe.
It is an excellent permanent magnet.

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 grind the entire surface of the magnet body or a required surface, and an outer peripheral blade cutting machine, an inner peripheral blade cutting machine, a surface grinding machine, a centerless grinder, a lapping machine, etc. are used for the processing.

However, when the Fe-BR permanent magnet material (15.5Nd7.5B77Fe) is ground by the above apparatus, for example, the thickness of 20
When the product thickness is processed to be 1 mm or less than 1 mm, there is a problem that each magnetic characteristic is deteriorated as shown by the curve b in FIG.

An object of the present invention is to provide a new permanent magnet material mainly composed of rare earth, boron and iron, which can prevent permanent deterioration of magnetic properties due to grinding of a sintered magnet body especially for small or ultra-thin materials. The object is a magnet material 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 by a Kerr effect optical microscope using the Kerr effect, the reversal mechanism of the magnetic domain shows that the magnetization reversal on the surface of the magnet body is 1/2 or less 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 by the usual method, but a thin film layer containing at least one of Nd, Pr, Dy, Ho, and Tb with a thickness of 15 μm or less is formed on the processed surface, and then vacuum or inert By subjecting the sintered body to a surface to be ground, which has been subjected to a specific heat treatment, in a specific heat treatment, the work-affected layer and lattice defects of the surface layer produced by the work made of crystal grains having a low coercive force, Formed as a modified layer by diffusion reaction with
The inventors have found that the coercive force and the squareness of the demagnetization curve of the Fe-BR permanent magnet material can be improved and 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, 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 on the surface to be ground of the sintered magnet body, It was formed by the diffusion reaction between the surface-altered layer formed by processing and the R'thin film layer (R 'is at least one of Nd, Pr, Dy, Ho and Tb) deposited on the surface layer. A permanent magnet material having a modified layer.

Furthermore, after grinding the sintered magnet body whose main phase is a tetragonal phase, R'thin film layer (R 'is Nd, At least one of Pr, Dy, Ho, and Tb) is deposited, and further heat-treated at 400 ° C. to 900 ° C. for 5 minutes to 3 hours in a vacuum or an inert atmosphere to form the work-affected layer and R ′ It is a method for producing a permanent magnet material, characterized in that the surface layer is formed into a modified layer by a diffusion reaction with a thin film layer.

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 has an extremely high energy product of 2MGOe or less, a high residual magnetic flux density, and a high coercive force, and prevents deterioration of magnetic properties due to grinding, by using B and R as the main components.
The BR permanent magnet material can be obtained at low cost.

That is, according to the present invention, in the grinding process of the Fe-BR system permanent magnet material (15.5Nd7.5B77Fe), 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 machined to a thickness of 1 mm or more from 20 mm, as shown by the curve a in Fig. 1, the magnetic properties are improved and the grinding process is improved compared to the comparative example (curve b) without the Nd thin film layer. It has the effect of preventing the accompanying deterioration of the magnet characteristics.

In the present invention, the surface to be ground of the sintered magnet body,
To deposit a thin film layer containing R '(R' is at least one of Nd, Pr, Dy, Ho, and Tb) as a main component, PVD (physical va
known as por deposition), vacuum deposition, ion plating, ion deposition thin film forming method (IVD, ion irradiation or method of simultaneously performing ion implantation and vacuum deposition), sputtering, plasma CVD (chemical vapor deposition)
ition) and the like, a thin film forming method by dry plating can be appropriately selected and used. The thickness of the thin film layer is 15 μm
If it exceeds the range, peeling of the thin film layer or reduction in mechanical strength is not preferable, and the thickness is not more than 15 μm.

Further, in the present invention, Nd, Pr, Dy, H having a thickness of 15 μm or less
A thin film layer containing at least one of o and Tb as a main component is formed, and then heat treatment is performed in a vacuum or an inert atmosphere.
It is necessary to perform the heat treatment at 5 ° C. to 900 ° C. for 5 minutes to 3 hours at least once, and the heat treatment forms a modified layer by the diffusion reaction between the thin film layer and the altered layer. However, if the temperature is lower than 400 ° C., the diffusion reaction at the interface is insufficient and the above effect cannot be obtained.
If the temperature exceeds 900 ° C, the thin film layer is easily oxidized under the vacuum degree obtained by an ordinary industrial method and the effect of improving the magnetic properties is lost, which is not preferable. If the heating time is less than 5 minutes, the diffusion reaction at the interface is insufficient. However, the effect of improving the magnetic properties is small, and if it exceeds 3 hours, the effect of improving the magnetic properties cannot be obtained due to the oxidation of the thin film layer, which is not preferable.

Further, the heat treatment can obtain a desired effect by performing the heat treatment at least once after the thin film is formed, but it may be a multi-step heat treatment if necessary.

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 12
It occupies 20% by atom to at least one of Nd, Pr, Dy, Ho, Tb, or further La, Ce, Sm, Gd, Er, Eu, Tm, Y.
Those containing at least one of b, Lu and Y are preferable.

Usually, one of R is sufficient, but a mixture of two or more kinds (Missille metal, didymium, etc.) can be practically used for the convenience of availability.

It should be noted that this R does not have to be a rare earth element, and may contain impurities that are unavoidable in production within a range that is industrially available.

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, especially high coercive force can be obtained. If it exceeds 20 atomic%, 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. 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 new permanent magnet,
If it is less than 65 atom%, the residual magnetic flux density (Br) is reduced, and if it exceeds 81 atom%, a high coercive force cannot be obtained.
The content is from atomic% to 81 atomic%.

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 in 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, 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.

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 When the content of the additive element having the maximum value is not more than atomic%, the coercive force of the permanent magnet can be increased.

The main phase of the crystal phase is tetragonal, which is indispensable for producing a sintered permanent magnet having excellent magnetic properties than 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 ≧ 1 kOe and a residual magnetic flux density Br> 4 kG, and the maximum energy product (BH) max is
H) max ≧ 20MGOe, the maximum value reaches 25MGOe or more.

Further, the main component of R of the gold powder for permanent magnet of the present invention is 50
% Or more when the light rare earth metal mainly composed of Nd and Rr 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 Nd
In the case of, the maximum value reaches 42 MGOe or more.

Examples Example 1 As starting materials, electrolytic iron having a purity of 99.9%, ferroboron alloy, and Nd 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 to cast a composition of 15Nd11B74Fe. Got a lump.

After that, this ingot was roughly crushed with a stamp mill and then finely crushed with a ball mill to obtain an average particle size of 3.0 μm.
Of fine powder was obtained.

Insert this fine powder into the mold, orient in a magnetic field of 20 kOe,
It was molded in a direction parallel to the magnetic field at a pressure of 1.5 / 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 dimensions of length 20 mm × width 10 mm × thickness 10 mm.

Then, from the sintered body, cut out into a test piece of length 20 mm × width 5 mm × thickness 0.15 mm 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.

Vacuum 5 × 10 ^- the vacuum vessel ⁶ Torr, first, the cathode of the thin plate specimen, the shutter plate as an anode, after cleaning the test single side presputtering, charging place the thin plate specimen as an anode Then, using Tb metal as a cathode target material, sputtering was performed for 3 hours to deposit a Tb thin film layer having a thickness of about 3 μm on both surfaces of the test piece.

Further, heat treatment was performed in vacuum at 630 ° C. for 1 hour to produce a permanent magnet (Invention 1) according to the present invention in which a Tb thin film layer was formed on the surface to be ground.

Further, a comparative permanent magnet (Comparative Example 2) was produced by subjecting the above thin plate test piece to heat treatment immediately under the same conditions without providing a Tb thin film layer.

Further, a comparative permanent magnet (Comparative Example 3) which was not subjected to heat treatment was prepared after the thin plate test piece was provided with a Tb thin film layer.

The Br, iHc and (BH) max values of the obtained permanent magnet material were measured in an open circuit using a vibrating sample magnetometer (VSM). The measurement results are shown in Table 1 and the measured I- The H loop is shown in FIG.

Example 2 A test piece having a length of 20 mm, a width of 5 mm, and a thickness of 0.15 mm was cut out from the sintered body of Example 1 so that the magnet orientation direction was included in the surface, and further polished in the same direction to obtain a thickness. Was reduced to obtain a thin plate test piece having a mirror surface and a thickness of 100 μm.

Vacuum 5 × 10 ^- the vacuum vessel ⁶ Torr, first, the cathode of the thin plate specimen, the shutter plate as an anode, after cleaning the test single side presputtering, charging place the thin plate specimen as an anode Then, using Tb metal as a cathode target material, sputtering was performed for 3 hours to deposit a Tb thin film layer having a thickness of about 3 μm on both surfaces of the test piece.

Further, heat treatment was carried out in vacuum at 630 ° C. for 1 hour to prepare a permanent magnet (Invention 4) according to the present invention in which a Tb thin film layer was formed on the surface to be ground.

Further, a comparative permanent magnet (Comparative Example 5) was produced by subjecting the above thin plate test piece to a heat treatment immediately under the same conditions without providing a Tb thin film layer.

Furthermore, after providing the thin plate test piece with a Tb thin film layer, a comparative permanent magnet (Comparative Example 6) not subjected to heat treatment was produced.

The Br, iHc and (BH) max values of the obtained permanent magnet material were measured in an open circuit using a vibrating sample magnetometer (VSM). The measurement results are shown in Table 2 and the measured I- The H loop is shown in FIG.

Example 3 A test piece having a length of 20 mm, a width of 5 mm and a thickness of 0.15 mm was cut out from the sintered body of Example 1 so that the orientation direction of the magnet was perpendicular to the plane, and further polished in the same direction. The thickness was reduced to obtain a thin plate test piece having a mirror surface and a thickness of 100 μm.

Vacuum 5 × 10 ^- the vacuum vessel ⁶ Torr, first, the cathode of the thin plate specimen, the shutter plate as an anode, after cleaning the test single side presputtering, charging place the thin plate specimen as an anode Then, using Dy metal as a cathode target material, sputtering was performed for 3 hours to deposit a Dy thin film layer having a thickness of about 3 μm on both surfaces of the test piece. Further, heat treatment was carried out in vacuum at 630 ° C. for 1 hour to produce a permanent magnet according to the present invention in which a Dy thin film layer was formed on the surface to be ground (Invention 7).

Similarly, after the pre-sputtering, vacuum 5 × 10 ^{- 6}
The thin plate test piece was placed as an anode in a Torr vacuum container, Ho metal was used as a cathode target material, and spattering was performed for 3 hours to deposit a Ho thin film layer having a thickness of about 3 μm on both surfaces of the test piece. Further, heat treatment was carried out in vacuum at 630 ° C. for 1 hour to prepare a permanent magnet according to the present invention in which a Ho thin film layer was formed on the surface to be ground (invention 8).

Further, a comparative permanent magnet (Comparative Example 9) was produced by subjecting the above thin plate test piece to a heat treatment immediately under the same conditions without providing a thin film layer.

The Br, iHc and (BH) max values of the obtained permanent magnet material were measured in an open circuit using a vibrating sample magnetometer (VSM), and the measurement results are shown in Table 3.

[Brief description of drawings]

Fig. 1 shows the thickness of permanent magnet material test pieces and Br, iHc and (BH) ma.
It is a graph which shows the relationship with x. 2 and 3 are I-H loop diagrams of the permanent magnet material.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Yamamoto 2-15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka Pref. 2-15-17 Sumitomo Special Metals Co., Ltd. Yamazaki Works

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 is a tetragonal phase. Surface-altered layer produced in step 1 and an R'thin film layer (R 'is N
A permanent magnet material having a modified layer formed by a diffusion reaction with at least one of d, Pr, Dy, Ho, and Tb). 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. R ′ thin film layer (R ′ is Nd, P
At least one of r, Dy, Ho, Tb) is deposited, and further in a vacuum or an inert atmosphere, 400 ° C to 900 ° C, 5 minutes to 3
A method for producing a permanent magnet material, characterized in that a surface layer is formed as a modified layer by a diffusion reaction between the work-affected layer and the R'thin film layer after heat treatment for a time.