JPS63285910A - Permanent magnet and manufacture thereof - Google Patents

Abstract

PURPOSE:To increase weather resistance while improving performance and reducing cost by forming a permanent magnet only from two phase of phase rich in a transition metal as a ferromagnetic intermetallic compound and phase rich in a nonmagnetic rare earth in the permanent magnet using a rare earth element, the transition metal and boron as basic ingredients. CONSTITUTION:In a permanent magnet employing a rare earth element (where including Y), a transition metal and boron as basic ingredients, the magnet is shaped only from two phase of phase rich in the transition metal as a ferromagnetic intermetallic compound and phase rich in a nonmagnetic rare earth. For form such a permanent magnet, the basic ingredients are dissolved, casted, thermally treated at a temperature of 250 deg.C or higher, and cured magnetically. The basic ingredients are dissolved, cast and hot-worked at a temperature of 500 deg.C or higher, thus orienting the crystal axis of a crystal grain in the specified direction, then changing the magnet into anisotropy. The magnet is further hot-worked, and thermally treated at a temperature of 250 deg.C or higher, thus magnetically curing the magnet. A magnet alloy after hot working is crushed, and alloy powder acquired is kneaded with an organic binder, and pressure- molded, thus obtaining the magnet. Accordingly, a low-cost permanent magnet having high performance and excellent weather resistance can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a permanent magnet containing a rare earth element, a transition metal, and boron as generated components, and a method for manufacturing the same.

[Conventional technology]

-Permanent magnets are important electrical and electronic materials used in a wide range of fields, from various household appliances to peripheral terminal equipment for large computers.

With the recent demand for smaller and more efficient electrical products,
Permanent magnets are also required to have increasingly higher performance. Typical permanent magnets currently in use are alnico, hard ferrite, and rare earth-transition metal magnets. In particular, R-Co permanent magnets, which are rare earth-transition metal magnets, and R
Since -Fe-B permanent magnets provide high magnetic performance, much research and development has been carried out on them.

Conventionally, there are methods for manufacturing these R-Fe-B permanent magnets as shown in the following documents.

(1) Sintering method based on powder metallurgy.

(Reference 11 Reference 2) ■ A quenched thin strip with a thickness of about 30 μm is made using a quenched ribbon manufacturing device used to produce an amorphous alloy, and the quenched thin section is made into a magnet using a resin bonding method. Resin bonding method. (Reference 3, Reference 4) (3) The quenched flakes used in method (2) above were
A method of mechanical alignment using a step-by-step hot press method.

(Document 4, Document 5) Here, Document 1: JP-A-59-46008; Document 2: M,
Sagawa, S., Fuji imura, N.
, Togawa, H., Yamamoto, a.
nd Y, Matsuura; J.

App 1. Ph1s, Vo 1. 55
(6) 15Maroh 1984. p20
83° Document 3: Japanese Patent Application Laid-Open No. 59-211549; Document 4: R, W, Lee; APf) 1. Phys.
Lett, Vol, 4B (8)+15
APri 1 1985. p790; Reference 5:
JP-A-100402-1 Next, the above-mentioned conventional method will be explained.

First, in the sintering method (1), an alloy ingot is produced by melting and casting, and then pulverized to obtain magnet powder with an appropriate particle size (several μm). Magnetic powder is kneaded with a binder, which is a molding aid, and press-molded in a magnetic field to complete a molded product. The compact is sintered in argon at a temperature around 11009C for 1 hour and then rapidly cooled to room temperature. After sintering, the coercive force is improved by heat treatment at a temperature of around 600°C.

In the resin bonding method (2) using quenched flakes by the melt spinning method, first, a quenched ribbon of R-Fe-B alloy is made at an optimal rotation speed of a quenched ribbon manufacturing apparatus. The obtained ribbon thin strip with a thickness of 30 μm is an aggregate of crystals with a diameter of 1000λ or less, and is brittle and easy to break.Since the crystal grains are distributed isotropically, it is also magnetically isotropic. be. This ribbon is pulverized to a suitable particle size, kneaded with resin, and press-molded.

(3) In the No.1 method, the ribbon-like quenched ribbon or flake in (1) is processed into dense and anisotropic R-Fe- by a method called a two-step hot pressing method in vacuum or an inert atmosphere. This is to obtain a B magnet.

In this pressing process, uniaxial pressure is applied, the axis of easy magnetization is oriented parallel to the pressing direction, and the alloy becomes anisotropic.

Note that the crystal grains of the ribbon produced by the initial melt spinning method are made smaller than the grain size at which it exhibits its maximum coercive force, to avoid coarsening of the crystal grains during the subsequent hot pressing. Allow the particles to grow to the optimum particle size.

[Problem that the invention seeks to solve]

Although it is possible to manufacture permanent magnets whose main components are rare earth elements, iron, and poron using the conventional techniques described above, these manufacturing methods have the following drawbacks.

In the sintering method (1), it is essential to turn the alloy into powder, but since R-Fe-B alloys are very active against oxygen, oxidation becomes even more intense when they are turned into powder. The oxygen concentration in the body inevitably increases. For this reason, it is prone to oxidation and has poor weather resistance. Also, when compacting the powder, a compacting aid, such as zinc stearate, must be used, which is removed beforehand during the sintering process; This carbon remains in the form of carbon in the R-Fe-
This is undesirable because it lowers the magnetic performance of the B alloy, especially the coercive force.

The molded product after press molding with the addition of a molding aid is called a green product, which is extremely brittle and difficult to handle.

Therefore, a major drawback is that it takes a considerable amount of effort to arrange them neatly in the sintering furnace. Because of these drawbacks, generally speaking, manufacturing R-Fe-B permanent magnets not only requires expensive equipment, but also has low production efficiency, resulting in high magnet manufacturing costs. It ends up.

Therefore, it cannot be said that this is a method that can take advantage of the advantages of R-Fe-B magnets, which have relatively low raw material costs.

Next, methods (2) and (3) use a vacuum melt spinning device, which currently has very poor productivity and is expensive.

The method (2) using resin bonding is isotropic in principle, resulting in a low energy product, and the squareness of the hysteresis loop is also poor, which is disadvantageous in terms of temperature characteristics and usage.

Method (3) is a unique method that uses a hot press in two stages, but it cannot be denied that it is extremely inefficient when considering actual mass production.

Furthermore, in this method, at high temperatures, for example, 800° C. or higher, the crystal grains tend to coarsen, resulting in an extremely low coercive force iHc, making it impossible to produce a practical permanent magnet.

The present invention is intended to solve the above-mentioned drawbacks of the prior art, and its purpose is to provide a rare earth-iron permanent magnet with excellent weather resistance, high performance, and low cost, and a method for manufacturing the same.

[Means for resolving conflicts]

The permanent magnet of the present invention is a permanent magnet whose basic components are a rare earth element (including Y), a transition metal, and boron, in which the magnet is a transition gold r14r i which is a ferromagnetic intermetallic compound.
It is characterized by consisting of only two phases: a ch phase and a non-magnetic rare earth rich phase.

Therefore, the manufacturing method of TIL has rare earth elements (including Y), transition metals, and boron as basic components, and has two phases: a transition metal rich phase, which is a ferromagnetic intermetallic compound, and a nonmagnetic rare earth rich phase. The second method of manufacturing a permanent magnet is to magnetically harden it by heat treatment at a temperature of 250°C or higher after melting and casting. , after casting,
A method for producing a permanent magnet, characterized by orienting the crystal axes of crystal grains in a specific direction and making the magnet anisotropic by hot working at a temperature of 500@C or higher, and further comprising: A third manufacturing method is a method for manufacturing a permanent magnet, which is characterized in that after hot working in the second manufacturing method, the permanent magnet is magnetically hardened by heat treatment at a temperature of 250° C. or higher, and Furthermore, a fourth manufacturing method is a permanent one, characterized by pulverizing the magnetic alloy after hot working in the second manufacturing method, mixing the obtained alloy powder with a slave binder, and press-molding. This is a method for manufacturing magnets.

[Effect]

As mentioned above, the sintering method and the quenching method, which are methods for producing rare earth-iron permanent magnets, each have drawbacks such as difficulty in powder control through pulverization, poor productivity, and poor weather resistance.

In order to improve these drawbacks, the present inventor started research on magnetization in the bulk state, and first hot-worked the magnet after casting in the composition range of the magnet whose basic components are rare earth elements, transition metals, and boron. It has been found that sufficient coercive force and good weather resistance can be obtained by making the material anisotropic and then subjecting it to heat treatment.

With this method, high-performance magnets can be manufactured without going through the difficult-to-control powder state, so heat treatment and strict atmosphere control are no longer required, magnet productivity is increased, and equipment costs can be greatly reduced.

The optimal composition of conventional R-Fe-B magnets is R, Fe, "ins, as typified by Document 2.

This composition is R,
It is shifting to the side rich in B. This is explained from the point that in order to obtain a coercive force, not only the main phase but also non-magnetic phases such as an R-rich phase and a B-rich phase are required.

However, in the case of the appropriate composition according to the present invention, the peak value of the coercive force exists where the B content shifts to the side where there is less B. In this composition range, in the case of the sintering method, the coercive force is drastically reduced, so it has not been much of a problem so far.

However, when a casting method is used, it is easier to obtain a coercive force on the low B side than the stoichiometric composition, and it is difficult to obtain it on the high B side.

These points can be considered as follows. First of all, whether a sintering method or a casting method is used, the coercive force mechanism itself is nuc.
It follows the leation model. This can be seen from the fact that the cutting curves of both exhibit a steep rise like SmCo5.

The coercive force of this type of magnet is basically based on a single domain model. That is, in this case, if the R*Fe, a B compound that develops a large crystal magnetic anisotropy is too large, it will have domain walls within the grains, so the reversal of magnetization will easily occur due to the movement of the domain walls, and the retention will be reduced. Magnetic force is small.

On the other hand, when the particles become smaller to a certain size or less, domain walls no longer grow within the particles, and the reversal of magnetization proceeds only by rotation, so the coercive force increases.

In other words, in order to obtain an appropriate holding force, it is necessary that the RzFe+ and B phases have an appropriate particle size.

The appropriate particle size is around 10 μm, and in the case of a sintered type, the particle size can be adjusted by adjusting the powder particle size before sintering.

On the other hand, in the casting method, crystals can be easily refined in the low boron region by adjusting the mold, casting temperature, etc. Viewed from a different perspective, this region can be said to be a phase rich in F'e compared to RtFe+ a B. At the solidification stage, Fe first appears as an initial product, and then, through a peritectic reaction, R3pe
l J B phase appears.

At this time, since the cooling speed is much faster than the equilibrium reaction, the primary crystal Fe is solidified in such a manner that the R* Feta B phase surrounds it. Since this composition range contains less B, it goes without saying that a rich phase such as the typical composition R1*FettBa of the sintered type does not exist. The heat treatment is for diffusing primary Fe to reach an equilibrium state, and the coercive force is largely dependent on the diffusion of the Fe phase.

Further, as the macrostructure during casting, a columnar crystal structure is preferable. By using this columnar crystal structure, it is possible to achieve in-plane anisotropy during casting and further improve performance during hot working.

The permanent magnet of the present invention is a transition metal rich phase, which is a ferromagnetic intermetallic compound, that is, Nd.

Phases typified by Fet a B and non-magnetic rare earth ric
Consisting of only two phases, the h phase, means that the non-magnetic Br1ch phase disappears from the three-phase coexistence state when using a sintering method, etc., and the magnetic R, 'rM;, and B phases increase. Since the saturation magnetization becomes larger, the magnetic properties are improved, and the particle size during casting can be more easily refined. Furthermore, since there is no oxide phase called R80 phase, the amount of oxygen in the magnet is reduced, making it difficult to oxidize.

The preferred composition range of the permanent magnet according to the present invention will be explained below.

Rare earths include Y', 'La, Ce, Pr
, Nd, Sm, Eu, Gd, T
b.

Dy, Ho, Er, Tm, Yb,
Lu is listed as a candidate, and one or a combination of two or more of these may be used. The highest magnetic performance is obtained with Pr.

Therefore, Pr, Pr-Nd alloy, Ce-P
An r-Nd alloy or the like is used. Further, a small amount of additive elements such as heavy rare earth elements such as Dy5Tb, A1, MOlSi, etc. can be used to improve the coercive force.

The main phase of the R-Fe-B magnet is RtFe'+;B.

Therefore, when R is 8 atomic % ungrooved, the above compound is no longer formed and a cubic crystal structure having the same structure as α-iron is formed, so that high magnetic properties cannot be obtained.

On the other hand, when R exceeds 30 atomic %, the nonmagnetic R-rich phase increases and the magnetic properties deteriorate significantly. Therefore, the range of R is 8
~30 atomic % is suitable. However, in order to form a cast magnet, preferably R8 to 258 to 25 atoms.

B is an essential element for forming the R*Fe+aB phase, and if it is not grooved by 2 at%, it becomes a rhombohedral R-Fe system, so high coercive force cannot be expected, and if it exceeds 6 at%, it becomes non-magnetic B.
Since the r ich phase increases, the residual magnetic flux density decreases, and it becomes difficult to obtain a fine R;Fe;-''B phase, it is appropriate that the B content ranges from 2 to 6 at.%.

Co is an effective element for increasing the Curie point of water-based magnets, and basically replaces Fe sites to create R2Co'+
7B, but this compound has a small crystal anisotropy magnetic field, and as the amount of this compound increases, the coercive force of the magnet as a whole decreases. Therefore, IK can be considered as a permanent magnet.
In order to provide a coercive force of Oe or more, the content is preferably within 50 atomic %.

A1 has the effect of increasing coercive force. (Reference 7: Z
Hang Maocai et al., Proceedings
of the 8th International
Workshop on Rare-Fart
h Magnets, 1985, p. 541) This document 7 shows the effect on sintered magnets, but the same effect also exists on cast magnets. However, since A1 is a non-magnetic element, increasing the amount added will reduce the residual magnetic flux density, and if it exceeds 15 atomic percent, the residual magnetic flux density will be lower than birdwellite, so it cannot fulfill its purpose as a rare earth magnet. I don't get it. Therefore, the amount of A1 added is preferably 15 atomic % or less.

It is obvious that it will be distorted.

Next, examples of the present invention will be described.

〔Example〕

(Example 1) An alloy having a composition as shown in Table m1 was melted in an induction furnace and cast into an iron mold to form columnar crystals.

Next, in order to harden the ingot magnetically, it was heated to 1000°C.
Annealing treatment was performed for 24 hours.

In the case of a cast type, if cutting and grinding are performed at this stage,
This is an in-plane anisotropic magnet that utilizes the anisotropy of columnar crystals.

In the case of an anisotropic type, hot working is first performed before annealing treatment, and then annealing is performed.

In this example, hot pressing was performed at 1000''C as hot working. The results are shown in Table 2.

Table 1 Table 2 (Example 2) Composition of N002 in Example 1, Prs ff Fes *
B, and Nd, which is the optimum composition of the sintering method of Document 2.

Regarding Few Bs, three methods were used: one in which columnar crystals were formed using an iron mold, one in which equiaxed crystals were formed using a vibration mold, and one in which coarse grains were formed using a ceramic mold. compared. The results are shown in Table 3.

Table 3 (Example 3) First, an alloy having a composition as shown in Table 4 was melted in an N induction furnace, cast in an iron mold, and after hot working, the ingot was magnetically hardened to 1000″C× Annealing treatment was performed for 24 hours.

At this time, the average grain size after annealing was about 15 μm.

If it is cut and ground at this stage, it will become an anisotropic magnet.

In the case of a 11 tree sushi filling type magnet, 18
-8 In a stainless steel container, hydrogen is absorbed in a hydrogen gas atmosphere of approximately 10 atm and dehydrogenation is repeated at 10-'torr. After pulverization, 4% by weight of epoxy resin is
After kneading, transverse magnetic field molding was performed in a magnetic field of 10 KOe.

The above results are shown in Table 5.

fJ4 Table 5 (Example 4) Hot-processed samples No. 2 and No. 8 prepared in Example 1 and Nd+'s as a comparative example.
A sintered Few Ba magnet was placed in a constant temperature and humidity chamber at 60° C. and 95%, and the state of corrosion on its surface was examined. At this time N
PryO',' phase was not contained in the magnet of o, 2.8. The results are shown in Table 6.

Table 6 [Effects of the Invention] As mentioned above (according to the permanent magnet of the present invention and its manufacturing method, coercive force can be obtained in the bulk state without pulverizing the cast ingot, so the manufacturing process can be significantly simplified. , it becomes possible to manufacture permanent magnets with low cost, high performance, and good weather resistance.

that's all

Claims (5)

[Claims] (1) In a permanent magnet whose basic components are rare earth elements (including Y), transition metals, and boron, the magnet has two phases: a transition metal rich phase, which is a ferromagnetic intermetallic compound, and a nonmagnetic rare earth rich phase. A permanent magnet characterized by consisting of only (2) In the manufacturing method of permanent magnets whose basic components are rare earth elements (including Y), transition metals, and boron, melting and
After casting, it is magnetically hardened by heat treatment at a temperature of 250°C or higher to form only two phases: a transition metal rich phase, which is a ferromagnetic intermetallic compound, and a nonmagnetic rare earth rich phase. How to manufacture magnets. (3) In the method of manufacturing permanent magnets whose basic components are rare earth elements (including Y), transition metals, and boron,
After casting, transition metal r is a ferromagnetic intermetallic compound that is magnetically anisotropic by orienting the crystal axes of the crystal grains in a specific direction by hot working at a temperature of 500°C or higher.
A method for manufacturing a permanent magnet, characterized in that only two phases are formed: an ich phase and a non-magnetic rare earth rich phase. (4) In the method of manufacturing permanent magnets whose basic components are rare earth elements (including Y), transition metals, and boron, melting and
After casting, hot working at a temperature of 500℃ or higher, then 250℃
A method for producing a permanent magnet characterized by forming only two phases: a transition metal rich phase, which is a ferromagnetic intermetallic compound, and a nonmagnetic rare earth rich phase, which are magnetically hardened by heat treatment at a temperature of ℃ or higher. . (5) In the method for manufacturing permanent magnets whose basic components are rare earth elements (including Y), transition metals, and boron, after melting and casting, hot working at a temperature of 500°C or higher and then pulverizing;
The resulting ferromagnetic intermetallic compound, transition metal rich
1. A method for producing a permanent magnet, which comprises kneading an alloy powder consisting of only two phases, a rich phase and a non-magnetic rare earth rich phase, with an organic binder and press-forming the mixture.