JPH01128404A - Manufacture of permanent magnet - Google Patents

Abstract

PURPOSE:To form a permanent magnet having small after-effect constant and large anisotrophy by giving heat treatment to an ally containing a rare earth element (including Y), boron and iron in a magnetic field having magnetic intensity of above 30kOe. CONSTITUTION:Heat treatment to be given to an alloy containing a rare earth element (including Y), boron and iron is performed in a magnetic field having magnetic field intensity of above 30kOe. When magnetic field intensity is less than 30kOe, a decrease of after-effect constant is not sufficient so that a change with time of a magnetic characteristic is intense and anisotrophy becomes also insufficient. Further, when magnetic field intensity is above 50kOe, it contributes to a decrease of after-effect constant and an increase of anisotrophy. Since in this way heat treatment in the magnetic field is given to the alloy containing an amorphous substance at the prescribed magnetic field intensity, an axis of easy magnetization of a crystal to be deposited by heat treatment is oriented in the direction of the magnetic field so as to obtain a permanent magnet having large anisotrophy and large coersive force. Further, after-effect constant is small and the change with time of the magnetic characteristic is small.

Description

[Detailed description of the invention] ■ Background of the invention Technical field The present invention relates to a method of manufacturing a permanent magnet.

Prior Art and its Problems Sm--Co magnets are mass-produced by powder metallurgy as rare earth magnets with high performance. Although this product has a high energy product of 32 MGOe, it has the disadvantage of high raw material cost.

Therefore, among the rare earth elements, Ce has a small atomic weight, is more abundant than Sm, and is cheaper.

Focusing on Pr and Nd, Nd-Fe-B is made from Nd, one of these rare earth elements, and Fe, which is abundant and inexpensive.
R-Fe-B (R is a rare earth element containing Y, the same applies hereinafter) magnets have been developed in recent years.

As such magnets, a sintered magnet is disclosed in JP-A-59-46008, and a sintered magnet using a high-speed quenching method is disclosed in JP-A-60-9852.

Although the conventional Sm-Co powder metallurgy process can be applied to magnets made using the sintering method, Nd-Fe, which does not easily oxidize,
Because it involves the process of pulverizing the alloy ingot to about 2 to 10 μm, it is difficult to handle, or the powder metallurgy process has a large number of steps (melting -> casting - coarse ingot grinding - thorough grinding - pressing -> sintering - magnet). ), so the advantage of using cheap raw materials cannot be taken advantage of.

On the other hand, magnets produced by the high-speed quenching method have the advantage of simplifying the process (melting - high-speed quenching - coarse pulverization - cold press (warm press) -> magnet) and do not require a pulverization process. However, in order to make magnets produced by the high-speed quenching method into industrial materials, it is necessary to further increase coercive force, increase energy accumulation,
It is desired to reduce costs and improve magnetization characteristics.

As a method for improving the characteristics of a magnet using such a high-speed quenching method, it is known to control the cooling rate during high-speed quenching to suppress the appearance of amorphous material and thereby improve the magnetic properties. However, in this case, although a product with high characteristics may be obtained, a product with good reproducibility and high characteristic values cannot be obtained, and the characteristic values tend to vary widely and the average value tends to be low.

On the other hand, as another improvement method, there is a method of heating an amorphous material to a crystalline state through heat treatment to improve the magnetic properties.

However, the magnets obtained by any of these methods are
Because the aftereffect constant is large, the magnetic properties change drastically over time, and because the axis of easy magnetization faces in an arbitrary direction, there is a problem that only isotropic magnets can be obtained.

II. OBJECTS OF THE INVENTION It is an object of the present invention to solve these problems and provide a method for manufacturing a permanent magnet with a small aftereffect constant and a large anisotropy.

III Disclosure of the invention Such objects are achieved by the invention described below.

That is, the present invention is a method for manufacturing a permanent magnet by heat-treating an alloy containing a rare earth element (including Y), boron, and iron, wherein the heat treatment is performed at a magnetic field strength of 30 kOe.
This is a method for manufacturing a permanent magnet, characterized in that it is carried out in the above magnetic field.

In addition, 1985 Digests of Int.
ermag(:ont, AA-7 has Nd-(
It is disclosed that a rapidly solidified Fe, Co)-B alloy is heat-treated in a magnetic field of 14 kOe, and that the crystallization temperature is accelerated by applying the magnetic field.

Also, JP-A-57-141901, JP-A No. 60-19
No. 4502 and No. 61-129802 also propose heat treating permanent magnets in a magnetic field of 15 kOe or less.

However, these methods do not aim at reducing the aftereffect constant or making the material anisotropic, and in fact do not show any effect in these respects.

IV Specific structure of the invention Hereinafter, a specific configuration of the present invention will be explained in detail.

As described above, the present invention produces a permanent magnet by subjecting an alloy containing a rare earth element containing Y, boron, and iron to heat treatment in a magnetic field.

In this case, the magnetic field strength is 30 kOe or more.

If this is less than 30 kOe, the aftereffect constant will not be sufficiently reduced, so the magnetic properties will change drastically over time, and the anisotropy will also be insufficient.

When the magnetic field strength is 50 kOe or more, more favorable results are obtained in terms of a decrease in the aftereffect constant and an increase in anisotropy.

Note that the magnetic field strength is usually 100 kOe or less.
This is because the magnetic field generated by a superconducting magnet can be generated at a relatively low cost, and the effects of the present invention can be fully realized at 100 kOe or less.

Such a magnetic field may be applied to the alloy from any direction, but when applying the present invention to a ribbon-shaped alloy produced by the liquid quenching method described later, it is necessary to apply the magnetic field to the alloy to avoid the influence of the demagnetizing field. In order to effectively utilize the energy, it is preferable to apply the energy in the longitudinal direction of the ribbon.

In the present invention, the heat treatment temperature is preferably below the Curie temperature of the alloy to be heat treated and from 300 to 750°C.

If the heat treatment temperature exceeds the Curie temperature, the alloy cannot be made anisotropic.

If the temperature is 300℃, it will take a long time to crystallize, and if the temperature is 750℃.
This is because if the temperature exceeds 100%, the optimum heat treatment time becomes short and control becomes difficult.

In addition, more preferable results are obtained when the heat treatment temperature is 400 to 700°C.

A permanent magnet obtained by such heat treatment in a magnetic field has a high degree of orientation and large anisotropy.

The magnitude of this anisotropy is, for example, when the residual magnetization in the orientation direction is Br and the residual magnetization in the perpendicular direction is Br'.
It can be expressed as Br/(Br±Br′).

In order to obtain Br/(Br+Br') for powder, for example, the powder is dispersed in melted paraffin in a unidirectional magnetic field, oriented and fixed, and then Br and B
All you need to do is measure r', Br/(Br+Br'
) and Br/(Br+B
r') are almost equivalent.

The residual magnetization may be measured using a vibrating magnetometer or the like.

The alloy subjected to such heat treatment in a magnetic field contains rare earth elements (including Y), boron, and iron.

Such alloys are typically made by rapid quenching of melts containing these elements.

In this case, a crystal chamber may be included, but it is preferable that the magnet be supercooled, that is, be amorphous, or that an amorphous and a crystal chamber coexist.

The object to be heat-treated may be a ribbon after high-speed quenching, a powder obtained by pulverizing the ribbon, or a powder obtained by compacting the ribbon.

Further, the powder may be plastically worked by warm working which also serves as heat treatment in the present invention. Specifically, hot pressing may be used to plastically work the powder by warm working.

Hot press pressure conditions are 200-5000Kg/ct
It is about a”.

Such alloys include rare earth elements R containing Y (eg, Nd, Pr, Ce, La, Dy.

Tb, Ho, etc.) of about 5.5 to 20 at%,
It is more preferable that the content is 7 to 13 at%, B is about 2 to 15 at%, more preferably 3 to 10 at%, and the balance is Fe.

The above Fe is partially (up to about 80%, more preferably 3
0 to 70%) is preferably substituted with Co.

Further, 50% or less of B is St, C, or Ga.

It may be substituted with AI, P, N, Se, S, etc.

In addition, Zr is used as another transition metal component.

1 of Nb, Mo, Hf, Ta, W, Ti, V and Cr
It is preferable that one or more of Cu, Ni, Mn, and Ag be contained in an amount of about 10 at%, more preferably up to 8 at% of the total content.

In such an alloy used in the present invention, the Curie temperature of the main phase as a crystalline phase described below is higher than the crystallization temperature.

The Curie temperature of the crystalline phase of such an alloy is 400-6
The temperature is about 50°C, and the crystallization temperature is about 400°C to 500°C.

Note that the above-described heat treatment is preferably performed at a temperature not lower than the crystallization temperature and not higher than the Curie temperature.

In the present invention, the melt containing R, boron, and iron can be rapidly quenched to form an alloy by a liquid quenching method, an atomization method, a thermal spraying method, a sputtering method, etc., although there are no particular limitations. Apply the law.

This liquid quenching method is a method in which a ribbon-shaped material is obtained by injecting molten metal from a nozzle onto the surface of a rotating metal body that has been cooled by water cooling, etc., and rapidly solidifying it at high speed. (single roll method), double roll method, etc.
In the present invention, the one-roll method, that is, the method in which the molten metal is injected onto the circumferential surface of one rotating roll, is most suitable.
The circumferential speed of the water-cooled rotary roll in the single roll method is 5 to 7.
The speed should be approximately 0 m/sec. At such a circumferential speed, an alloy containing amorphous material is obtained, although this varies depending on the composition of the alloy.

At less than 5 m/sec, all of the ribbon becomes crystalline, and the effect of heat treatment decreases, and at a circumferential speed of 50 to 70 m/sec, all of the ribbon becomes amorphous, and at a circumferential velocity of over 70 m/sec. There will be no need.

The alloy of the permanent magnet R-T-B system (T is one or more transmuted metal elements containing Fe as an essential element) to which the manufacturing method of the present invention is applied is substantially composed of R-T-B, etc. The main phase of the tetragonal crystal structure (mainly R2T
14B tetragonal compound), but has this crystalline main phase, and in addition to this, either crystalline or amorphous except R2T14B may exist as a subphase.

The subphase exists as a grain boundary phase and has the function of strengthening the alloy structure. The subphase may be crystalline or amorphous.

The permanent magnet in the present invention may be in any form, such as a ribbon-shaped magnet, a bulk magnet warm-processed from powder, or a bonded magnet in which powder is bonded with a binder such as resin.

The thickness of the ribbon after high-speed quenching is approximately 10 to 80 μm.
The powder obtained by pulverizing this powder has a particle size of about 1 to 1000 μm.

When using powder, it is preferable to grind it to a particle size of 30 to 500 μm, and cold press or warm press it to obtain a high-density bulk magnet.

In addition, by making the powder denser and more anisotropic using plastic working or the like, the magnetic properties can be improved by about 2 to 3 times.

Plastic working methods include hot pressing, extrusion, rolling, swaging, and forging.

Hot press conditions are 550-1100℃, 200-2
500 K g/cm2 is preferred.

In terms of properties, hot pressing and extrusion processing are preferred. Although hot pressing may be performed only by primary pressing, good magnetic properties can be obtained by further performing secondary pressing.

For extrusion molding: 550-1100℃, 400-120℃
00 K g/cm' is preferable, and in this case, the above-mentioned heat treatment in a magnetic field can be used in combination. A magnet further anisotropic in this way is also used as a bonded magnet.

■Specific effects of the invention According to the present invention, since an alloy containing an amorphous substance is heat-treated in a magnetic field at a predetermined magnetic field strength, the axis of easy magnetization of the crystals precipitated by the heat treatment is oriented in the direction of the magnetic field, resulting in an abnormality. A permanent magnet with high orientation and high coercive force can be obtained.

Furthermore, the permanent magnet manufactured according to the present invention has a small aftereffect constant and little change in magnetic properties over time.

(2) Specific Examples of the Invention Hereinafter, the present invention will be explained in more detail by giving specific examples of the invention.

[Example 1] An alloy having a composition of 14Nd-8B-25Co-53Fe (values represent at%) was produced by arc melting. The obtained molten alloy was injected onto the surface of a roll at a circumferential speed of 50 m/sec through a quartz nozzle and rapidly cooled to obtain a ribbon with a thickness of 50 μm.

The crystallization temperature of this product was 520°C.

This ribbon was subjected to X-ray diffraction and confirmed to be amorphous.

This ribbon was subjected to heat treatment in a magnetic field under the conditions shown in Table 1 below to obtain a permanent magnet sample.

The Curie temperature of the crystalline phase of these samples is 600°C
Met.

Note that the direction in which the magnetic field was applied was the longitudinal direction of the ribbon.

The following tests were conducted on the obtained samples.

(1) Storage test Samples were stored at 25° C. and 65% RH for 1000 hours, and changes in surface magnetic flux (Δφ/φ) at the initial stage and after storage were compared.

(2) Measure the residual magnetization (Br) in the orientation direction of the anisotropy measurement sample and the residual magnetization (Br') in the direction perpendicular to this, and from these, Br
/(Br+Br') was calculated.

Note that the residual magnetization was measured using a vibrating magnetometer.

[Comparative Example 1] Permanent magnet samples obtained by heat treatment in the absence of a magnetic field and permanent magnet samples obtained by heat treatment under conditions where the magnetic field strength is outside the range of the present invention were subjected to durability tests and differences in the same manner as above. Orientation measurements were performed.

The results of Example 1 and Comparative Example 1 are shown in Table 1.

Table 1 Sample Magnetic field strength Heat treatment temperature Treatment time Br/(
Br◆Br ) (BH) wax ΔΦ/φNo,
(koe) ('C) (minute)
(MGOe) (%) 1 35
550 45 0.8 26
-0.82 50 550 45
0.9 35 -0.63 Zoo
550 45 0.9 35
-0.54 (comparison) 15 550 45
0.5 15 -1.85 (comparison) O
5504'5 0.5 10 -2.0
6 35 550 45 0.8
26 -0.137 35 5
80 45 0.75 25 -0.8
8 35 520 45 0.7
5 25 -0.89 35 80
0 45 0.5 10 -1.51
0 35 300 45 0.5
10 -1.5 Note that when a ribbon having the composition shown below, prepared according to Example 1, was subjected to the heat treatment in a magnetic field according to the present invention, the same effect as in Example 1 was obtained.

14Nd-8B-25Co-52Fe-I Zr14N
d-8B-25Co-52Fe-INbl 4N'd-
8B-25Co-52Fe-ITil 4Nd-8B
-31Co-46Fe-I Zr14Nd-8B-38
Co-39Fe-f Zr10Nd-6B-25Co-
58Fe-I Zr3Nd-5B-25Co-61Fe
-IZr [Example 2] Sample N002 of Example 1 and Sample N0 of Comparative Example 1
04 to 50 to 200 μm, mixed with thermosetting resin, and molded in a 40 kOe magnetic field to give a density of 6.0 g/c.
A bonded magnet of m3 was obtained.

This was subjected to pulse magnetization of 40 kOe and its magnetic properties were measured.

The results are shown below.

(Sample No. 2) Br/ (Br+Br')=0.85iHc=f2k
oe (B H) max = 20 M G Oe (Sample No., 4) Br/ (Br+Br') = 0.5 iHc = 10 koe (B H) max = 8 M G Oe From the above results, the effect of the present invention is confirmed. It is clear.

Claims (1)

[Claims] (1) A method of manufacturing a permanent magnet by heat-treating an alloy containing rare earth elements (including Y), boron, and iron, characterized in that the heat treatment is carried out in a magnetic field with a magnetic field strength of 30 kOe or more. A method of manufacturing a permanent magnet.