JPS62188745A - Permanent magnet material and its production - Google Patents

Abstract

PURPOSE:To prevent deterioration in the magnetic characteristics of an Fe-B-R type sintered magnet body by grinding by forming a thin film of a specified metal as a modifying layer on the surface of the magnet body to be ground and an oxidation inhibiting layer of a specified metal or an alloy thereof on the thin film. CONSTITUTION:A sintered magnet body is composed of, by atom, 12-20% R (R is one or more among Nd, Pr, Dy, Ho and Tb combined optionally with one or more among La, Ce, Sm, Gd, Er, Tm, Yb, Lu and Y), 4-20% B and 65-81% Fe and the principal phase is made tetragonal phase. A thin film of one or more among Ce, La, Nd, Pr, Dy, Ho and Tb as a modifying layer is formed on the surface of the magnet body to be ground. An oxidation inhibiting layer of one or more among Ti, W, Pt, Au, Cr, Ni, Cu, Co, Al, Ta, Ag and Pb or an alloy of such metals is further formed on the thin film.

Description

[Detailed description of the invention] Industrial field of application This invention is a Fe-B-R system that prevents deterioration of magnetic properties due to grinding of the surface of a sintered permanent magnet and prevents changes in magnetic properties over time. The present invention relates to permanent magnets, and particularly to a high-performance permanent magnet material having a thickness of 1.0ITIIT1 or less and a method for manufacturing the same.

BACKGROUND ART Currently, there is a demand for permanent magnet materials that have high magnetic properties and are inexpensive, and there is also a strong desire for permanent magnet materials that are rich in resources and have compositional elements that can be supplied in an unprecedentedly stable manner. previously proposed an Fa-BR-based permanent magnet (R is at least one rare earth element including Y) as a new high-performance permanent magnet that does not contain expensive Sm (Japanese Patent Application Laid-Open No.
9-46008, JP-A-59-64733, JP-A-59-89401, JP-A-59-132104).

This permanent magnet uses light rare earths, which are rich in resources, mainly ceramics and metals, as R, and has Fe as its main component.
It is an excellent permanent magnet that exhibits an extremely high energy product exceeding e.

Recently, with the improvement in performance and miniaturization of magnetic circuits, Fe −
B-R permanent magnet materials are attracting more and more attention, and Fe-B-R for small or thin items with a thickness of 1.0 mm or less is attracting more and more attention.
There has been a demand for permanent magnet materials.

In order to manufacture permanent magnet materials for such uses, small or ultra-thin sintered magnets are processed to remove surface irregularities and distortions, or to remove surface oxidation layers. In order to incorporate it into a magnetic circuit, it is necessary to cut the entire surface or the required surface of the magnet body.

However, when such Fe-B-R permanent magnet material (15,5F!117.5B77FG> As shown in the curve, there was a problem that various magnetic properties deteriorated.

The applicant first applied an R-1 film layer (
R' is Fe, Pr, u, Ho, T.

proposed a method (Japanese Patent Application No. 60-216047) in which at least one of these is formed by vapor deposition or the like, and then heat treated to improve the deterioration of magnetic properties caused by the process-affected layer.

However, the above R' thin film layer is very easily oxidized, so
Depending on the usage environmental conditions, the R' thin film layer on the magnet surface may be oxidized and the magnetic properties may deteriorate again.

Purpose of the Invention The present invention is aimed at preventing deterioration of magnetic properties caused by cutting of sintered magnet bodies, especially for small or ultra-thin objects, in a new permanent magnet material mainly composed of rare earth elements, boron, and iron. The purpose of the present invention is to provide a permanent magnet material with improved magnetic properties over time, and a method for manufacturing the same.

Structure and effect of the invention As a result of various studies on the coercive force of Fa-B-R permanent magnet materials, the inventors found that the magnitude of the coercive force of the magnet body is as follows:
This is due to differences in grain boundary structure rather than within crystal grains, and when the polished sintered magnet surface is examined in detail with an optical microscope using the Kerr effect, magnetization reversal on the magnet surface is found. This occurs in a very low magnetic field below the coercive force of 172 inside the magnet, and the reason why the coercive force of the crystals in the first layer on the processed surface of the sintered magnet is low is that it is necessary for a high coercive force to appear. It was found that this is due to the absence of a metal phase having an optimal body-centered cubic structure (hereinafter referred to as a body-centered cubic phase).

The body-centered cubic phase that exhibits high coercive force, which was first discovered by the inventor, is provided as a grain boundary phase with an optimal thickness and a special body-centered cubic phase structure on the crystal group on the surface of the processed sintered magnet. Although this is not easy with normal methods, Ce,
La, Nc+, Pr, Doll, HO.

By forming a thin film layer containing at least one type of Tb as a main component and then performing a specific heat treatment in a vacuum or an inert atmosphere, the crystal grains with low coercive force on the surface to be ground of the sintered body are removed. The modified layer and lattice defects are formed into a modified layer by a diffusion reaction between the thin film layer and the modified layer, and further, on the easily oxidized thin film layer, T%, W, Pt, Au,
Cr, NL, QL, Co, /V, Ta.

By depositing a metal or alloy layer consisting of at least one of Al and Pb, the coercive force and squareness of the demagnetization curve of the Fe-B-R permanent magnet material can be improved, and the magnetic properties can be improved. We discovered that aging can be improved,
This invention has been completed.

That is, this invention provides R (R is at least one of Nd, Pr, Dy, Ho, and Tb, or in addition, La, Ce, and Sm).
, (A, Er, Etl, 1m.

consisting of at least one of Yb, Lu, and Y)1
R adhered to the surface to be ground of a sintered magnet body whose main components are 2 at% to 20 at%, B44 at% to 20 at%, and Fe65 at% to 81 at%, and the main phase is a tetragonal phase.
'Thin film IW (R- is Ce, L, I, Nd, Pr,
Dy.

a modified layer consisting of at least one of Ho and Tb);
Additionally, metal or alloy layers (Ti, W, Pt, Au, Cr, N5 Cu) deposited on the R′ thin film layer.
, Co, Ml.

The permanent magnet material is characterized by having an oxidation-preventing layer made of at least one of Ta, Al, and Pb.

Furthermore, 1m of R''1 films (R' is Ca) are applied to the ground surface of the sintered magnet whose main phase is a tetragonal phase.

At least one of La, Nd, Pr, Dy, Ho, and Tb) is deposited, and after adhering the R' thin film layer or on the R- thin film layer,
TL, W, Pt, Au, Cr, N5 CL,
Co, JV, Ta.

After depositing an oxidation-preventing layer consisting of a metal layer or an alloy layer consisting of at least one of Al and Pb, it is further heated at 400'C to 900'C in a vacuum or an inert atmosphere.
, a permanent magnet material 'f31 which is characterized in that it is subjected to heat treatment for 1 minute to 3 hours to make the process-affected layer of the surface to be ground into a modified layer, and that an oxidation prevention layer is provided on the modified layer. The manufacturing method is as follows.

Further, the permanent magnet material of the present invention has an average particle size of 1 to 1.
80. The main phase is a compound with a tetragonal crystal structure in the range of i7m, and the non-magnetic phase (1% to 50% by volume) (
(excluding oxide phase).

Therefore, this invention mainly uses Nd or even yen-based light rare earths, which are abundant in resources, as R, and F
By using il, B, and R as the main components, 20MGO
A Fe-BR permanent magnet material that has an extremely high energy product of 8 or more, a high residual magnetic flux density, and a high coercive force, and prevents deterioration of magnetic properties due to grinding can be produced at a low cost.

That is, according to the present invention, in the grinding process of Fe-B-R permanent magnet material (15,5Nd 7.5877Fe), for example, a Nd vapor deposition layer is provided on the surface to be ground to turn the altered layer into a modified layer. By this, the thickness is 1m from 20mm.
Even when processed to a product thickness of less than m, as shown in curves a in Figs. This has the effect of preventing deterioration of magnetic properties caused by.

Furthermore, the metal or alloy layer deposited on the R-thin film layer has excellent oxidation resistance and R- −
The bond strength with the thin film layer is also excellent.

In this invention, R
'(R- is Ce, La, Nd, Pr, Dy,
at least one of Ho, Tb) and T.

W, Pt, Au, Cr, N5 Cu, Co
, AI, Ta, Al, and at least one of Pb
In order to deposit the antioxidant layer consisting of a metal layer or an alloy layer consisting of seeds, vacuum evaporation, ion sputtering, ion blating, ion evaporation thin film formation method ()VD),
A thin film forming method such as a plasma vapor deposition thin film forming method (EV[)] can be appropriately selected and used.

Moreover, the thickness of the thin film layer is 0.11 Jm to 301 Jrrl
is preferable, and if the thickness of the thin film layer is less than 0.1 m, a uniform film will not be formed, and the rare earth metal in the thin film layer will be oxidized and lost during heat treatment, so it is not preferable.
If it exceeds 1 m, it will take a long time for vapor deposition, etc., resulting in high costs, and as the film thickness increases, unnecessary gaps will be formed in the magnetic circuit, which is disadvantageous, and it is difficult to improve the surface layer. This is not desirable because the quality effect is also saturated.

The thickness of the metal or alloy layer formed on the thin film layer is 0.
．． If it is less than 1 Jim, it is difficult to form a uniform film, and there is no effect of improving the aging of magnetic properties. un
Exceeding this is not preferable because it requires a long time for vapor deposition, etc., and an unnecessary gap is formed in the magnetic circuit as the film thickness increases.

In addition, in this invention, Ce, La, Nd, Pr, Dy, Ho, T with a thickness of 0.1 to 30 Alm
After forming a thin film layer containing at least one of b as a main component or depositing an antioxidation layer made of the above metal or alloy layer, heat treatment is performed in a vacuum or an inert atmosphere, but the heat treatment conditions are It is necessary to perform heat treatment at least once at 400'C to 900'C for 1 minute to 3 hours in a vacuum or inert atmosphere, and the heat treatment causes a diffusion reaction between the thin film layer and the modified layer to form a modified layer. Become.

However, if the temperature is less than 400'C, the diffusion reaction at the interface is insufficient and the above effects cannot be obtained, and if it exceeds 900'C, the thin film layer is likely to oxidize and the effect of improving magnetic properties is lost, which is not preferable. If the heating time is less than 1 minute, the diffusion reaction at the interface will be insufficient and the effect of improving magnetic properties will be small; if it exceeds 3 hours, the effect of improving magnetic properties will not be affected due to oxidation of the thin film layer, so it is not preferable. do not have.

Further, the heat treatment is performed at least once, so that
Although the desired effect can be obtained, multi-stage heat treatment may also be used if necessary.

Reasons for limiting the components of the permanent magnet material The rare earth element R used in the permanent magnet material of the present invention accounts for 12 to 20 at% of the composition.

At least one of the following phylum, Dy, Ho, Tb, or furthermore, La, Ce, Sm, cd, Er
, Eu, rm, Yb, Lu.

Those containing at least one type of Y are preferred.

Also, normally one type of R is sufficient, but in practice two types are sufficient.
A mixture of more than one species (Mitushmetal, Didim, etc.) can be used for reasons such as availability.

Note that this R does not have to be a pure rare earth element, and may contain impurities that are unavoidable in production within an industrially available range.

R is an essential element in the above-mentioned new permanent Ia stone materials, and if it is less than 12 at%, a cubic structure with the same structure as α-iron will precipitate, resulting in high magnetic properties, especially high stability. If no magnetic force is obtained and the content exceeds 20 atomic %, the R-rich nonmagnetic phase increases, the residual magnetic flux density (Br) decreases, and permanent '/AUi with excellent characteristics cannot be obtained. Therefore, the rare earth element is in the range of 12 atomic % to 20 atomic %.

B is an essential element in the permanent magnet material according to the present invention, and when it is less than 4 atom%, the rhombohedral structure becomes the main phase, and a high coercive force (it-('c) cannot be obtained, and B is less than 20 atom%.
If the value exceeds 100%, the amount of B-rich nonmagnetic phase increases and the residual magnetic flux density (Br) decreases, making it impossible to obtain an excellent permanent magnet. Therefore, B is in the range of 4 at.% to 20 at.%.

Fe is an essential element in the new above-mentioned permanent magnet, and if it is less than 65 at%, the residual magnetic flux density Br decreases, and the
If it exceeds 1 atomic %, high coercive force cannot be obtained, so F
The content of e is 65 atomic % to 81 atomic %.

In addition, in the permanent magnet material according to the present invention, replacing a part of FB with Co can improve the temperature characteristics without impairing the magnetic properties of the resulting magnet.
If the am conversion exceeds 20% of Fe, the magnetic properties will deteriorate, which is not preferable. C.

When the atomic ratio of (Br) is 5% to 15% of the total amount of Fe and Co, it is preferable to obtain a high magnetic flux density because (Br) increases compared to the case where no substitution is made.

In addition, at least one of the following additional elements is R-BF
It can be added to A-type permanent 115 because it is effective in improving the coercive force and the squareness of the demagnetization curve, improving manufacturability, and reducing cost.

A1.4 of 9.5 atom% or less, Ti of 5 atom% or less, 9
．． V at 5 atomic % or less, Cr at 8.5 atomic % or less.

8.0 atomic % or less) In, 5.0 atomic % or less B
i.

Nb of 9.5 atomic % or less, Ta of 9.5 atomic % or less.

No less than 9.5 atom%, No less than 9.5 atom%, 2.
5 at % or less sb, 7 at % or less Ge, 3.5 at % or less Sn, 5゜5 at % or less Zr19.0
At least one of Ni at % or less, Si at 9.0 atomic % or less, Zn at 1.1 atomic % or less, and Hf at 5.5 atomic % or less is added, however, when two or more types are contained. By containing the maximum content of atomic percent or less of the element having the maximum value among the additive elements, it is possible to increase the coercive force of the permanent magnet.

It is indispensable that the main phase of the crystalline phase be a square one in order to produce a sintered permanent magnet having superior magnetic properties than a fine and uniform alloy powder.

Further, the permanent magnet of the present invention can be press-molded in a magnetic field to obtain a magnetically anisotropic magnet, and can be press-molded in a non-magnetic field to obtain a magnetically isotropic magnet.

The permanent magnet according to the present invention has a coercive force of 111c≧4kOs
, the afterglow magnetic flux density Br > 4 k(3), and the maximum energy product (BH) max is (
Bt+)max≧20HGOe, the maximum value is 25H
Reach GOa or higher.

Further, the main component of R in the permanent magnet material of this invention is 50
% or more is occupied by light rare earth metals mainly composed of metals, R12 atomic % to 15 atomic %, B66 atomic % to 9 atomic %
, 78 atomic % to 80 atomic % Fe, exhibits excellent magnetic properties of (BH) ma

Examples Example 1 As starting materials, electrolytic iron with a purity of 99.9%, ferroboron alloy, Nd with a purity of 99.7% or more, and gold were used. After mixing these, they were high-frequency melted, and then cast in a water-cooled copper mold. , 13.5Nd 7B 1.5Dy78Fe was obtained.

Thereafter, this ingot was embrittled by H2 sludge absorption, coarsely ground using a stamp mill, and then finely ground using a ball mill, with an average particle size of 3.0. A fine powder of am was obtained.

This fine powder was inserted into a mold, oriented in a magnetic field of 20 koe, and molded at a pressure of 1.5 t4 in a direction perpendicular to the magnetic field.

The obtained molded body was sintered at 1100'C for 1 hour in an Ar atmosphere to obtain a sintered body having dimensions of 20 mm in length, 10 mm in width, and 10 mm in thickness.

Then, from the sintered body, the length is 3 mm, the width is 4 mm, and the thickness is 0.1 mm, so that the direction perpendicular to the orientation direction of the magnet is included in the plane.
10. Cut out a test piece with the same dimensions and polish it in the same direction to reduce the thickness and give it a mirror surface. A thin plate test piece with a thickness of 1 oz was obtained.

Next, using ceramic metal as the cathode target material, sputtering was performed under the following conditions, and a thickness of about 3βm of Nd was applied to both sides of the specimen.
A thin film layer was applied.

Thereafter, at 630°C in a 3X10-6 orr vacuum,
Heat treatment was performed for 1 hour.

Furthermore, under the same sputtering conditions, the metals shown in Table 1 were
Sputtered to a thickness of 〃m.

In addition, a comparative permanent magnet (Comparative Example 15) was prepared by providing an Ndwj film layer on the above thin plate test piece and immediately heat-treating it under the same conditions without providing a metal layer.

[3r, 1l-1c of each obtained permanent magnet material.

Test the B1-1c, Hc and (BH) max values using a type 1 magnetometer (VS)! ) is used to measure open circuit,
Furthermore, the demagnetization rate evaluated by the irreversible demagnetization rate after being left in air at room temperature for 10,000 hours 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 level: 2x10-6 Torr Ar pressure during high-frequency sputtering: 0.2x10-3 Torr ~ lX1O-3Torr
rr input voltage: 150 W (during initial sputtering and main sputtering) 70 W (during reverse sputtering) Sputtering time: Initial sputtering 30 minutes reverse sputtering 30 minutes main sputtering 3 hours or less Margin Table 1 Example 2 Same conditions as Example 1 13.5Nd manufactured and processed by 7
A sintered magnet specimen having a composition of E31.5D Schiff 8Fe was coated with an Nd layer for 3.5 hours under the sputtering conditions of Example 1. Br of each permanent magnet material obtained by sputtering an alloy layer having the composition shown in Table 2 on the thin magnet coated with a thickness of m and further subjected to the heat treatment of Example 1 under the same conditions. .

Bl-(c, )-1c and (BH)max values were measured in open circuit using a moving sample magnetometer (VSM),
Furthermore, the demagnetization rate evaluated by the irreversible demagnetization rate after being left in air at room temperature for 10,000 hours 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 expressed in terms of its area ratio.

Margin below Table 2

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the thickness of a permanent magnet material test piece and 3r. FIG. 2 is a graph showing the relationship between the thickness of a permanent magnet material $31 test piece and 1l-1c. FIG. 3 is a graph showing the relationship between the thickness of a permanent magnet material test piece and (BH)max.

Claims (1)

[Claims] 1 R (R is at least one of Nd, Pr, Dy, Ho, Tb, or furthermore, La, Ce, Sm, Gd,
At least one of Er, Eu, Tm, Yb, Lu, Y
(consisting of seeds) 12 atom% to 20 atom%, B4 atom% to 2
The main component is 0 at%, Fe65 at% to 81 at%,
On the surface to be ground of a sintered magnet whose main phase is a tetragonal phase,
Deposited R' thin film layer (R' is Ce, La, Nd, Pr,
A modified layer consisting of at least one of Dy, Ho, Tb) and a metal layer or alloy layer (Ti, W, Pt, Au, Cr, Ni, Cu, C
1. A permanent magnet material characterized by having an oxidation-preventing layer made of at least one of the following: 1, Al, Ta, Ag, and Pb. 2 R (R is at least one of Nd, Pr, Dy, Ho, Tb, or furthermore, La, Ce, Sm, Gd,
At least one of Er, Eu, Tm, Yb, Lu, Y
(consisting of seeds) 12 atom% to 20 atom%, B4 atom% to 2
The main component is 0 at%, Fe65 at% to 81 at%,
After grinding a sintered magnet whose main phase is a tetragonal phase, an R' thin film layer (R' is Ce, La, N
d, Pr, Dy, Ho, and Tb), either after the R' thin film layer is deposited or on the R' thin film layer,
Ti, W, Pt, Au, Cr, Ni, Cu, Co, Al
, Ta, Ag, and Pb, and then further heated at 400°C to 900°C in vacuum or an inert atmosphere.
℃, for 1 minute to 3 hours to transform the process-affected layer of the surface to be ground into a modified layer, and to form an oxidation-preventing layer on the modified layer. Production method.