JPS63213317A - Rare earth-iron permanent magnet - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention focuses on rare earth-iron permanent magnets.

[υC/, l this technology]

Conventionally, rare earth-iron magnets have been reported using the following three methods.

(1) H) Magnet by sintering method based on advanced metallurgy method (Reference 1) (2) A quenched thin strip with a thickness of about 30 μm is made using a quenched ribbon production device used for producing an aluminum alloy. A magnet that combines 17 pieces with resin.

(Reference 2) (31) The same thin section used in method 21 was subjected to two steps:
1 Magnet subjected to mechanical orientation treatment using the sotopress method (Reference 2) Reference ls M, Sagawa, S, Fujim
ura, N, To+7awa, Il, yam
amoLo and Y, Matsuura;J,
Apf)! , ■'hys, Vo1.55 (6), 15M
arcb 1984. P2O83 References 2. R,W
,Lce;Apple,Phys,I,c L L,V
o 1.4G (8), 15Δ1) ril 1085
．． P700 In accordance with the literature, all the above-mentioned fiff techniques are explained. first(
In 1), an alloy ingot is produced by n'T solution and casting, and is crushed to a particle size of about 3 μm.
It is turned into magnetic powder. Magnetic powder is kneaded with a binder, which serves as a molding aid, and press-molded in a magnetic field to complete a molded product. The compact was heated at 1100°Ci'+i in argon.
It is sintered at a temperature after f for 1 hour and then rapidly cooled to room temperature. After gelation, the coercive force is further improved by heat treatment at a temperature of around 000°C.

For the magnet (2), first, a quenched ribbon of 12-Fc-n alloy is made by quenching P, B (at the optimal rotation speed of the band manufacturing device).

The obtained elastic band has a ribbon shape with a thickness of 30 μm.

Polycrystals with a diameter of 1000 Å or less are aggregated.

RV4'+Si is brittle and easily cracked, and since the crystal grains are distributed in the same direction, it is also magnetically isotropic. If this ribbon is made into an appropriate particle size and kneaded with (÷1 fat) and press-molded, it will form approximately 85 pieces at a pressure of about 7 tons/am'.
It becomes possible to fill the

In the case of the magnet described in 3), a ribbon-like quenched ribbon or a piece of ribbon is first heated at approximately 700° C. in a vacuum or in an inert atmosphere.
Place in graphite or other heat-resistant press mold preheated at °C. Uniaxial pressure is applied when the ribbon reaches the desired temperature. Temperature and time are not specified, but T = 725 ± 250° as a condition to obtain sufficient toughness.
C1 pressure is 1' to 1,4 L on/c
In' level is suitable. At this stage, although the six stones are slightly oriented in the pressing direction, the overall structure is isotropic. The following; 1; · Doblessing is performed in a type that covers a large area.

Most commonly, it is pressed at 700°C and 0.7 ton for a few seconds. Then, the sample has the initial thickness of 172 mm, the axis of easy magnetization is oriented parallel to the pressing direction, and the alloy becomes anisotropic. These techniques are a two-stage, one-stage method.

t-1) r c c s p r o c c
It is called d u r e ). By this method, a dense and anisotropic 12-Fc-13 magnet can be manufactured. Note that the crystal grains of the ribbon produced by the initial melt spinning method are made smaller than the grain size at which they exhibit the maximum coercive horns, and later, during hot pressing, the grain size of the crystal grains is determined to be smaller. to obtain the maximum particle size of Δ.

[Problem that the invention seeks to solve]

Although it is possible to fabricate rare earth-iron based magnets using the above-mentioned conventional techniques, magnets using these techniques have the following drawbacks. For the sintered magnet (1), it is essential to turn the alloy into powder, but since the R-F c-13 alloy is very active against oxygen, turning it into powder causes severe oxidation.

The degree of 1M striations in the 111 concretions inevitably becomes high. Furthermore, when molding the powder, it is necessary to use a molding aid such as zinc stearate, which is removed in advance during the 27A binding process, but about 50% of this is contained in the magnet. It remains in the form of carbon. This carbon significantly reduces the magnetic performance of R-F c-13.

The molded body after press molding with the addition of a molding aid is called a green body. This is very fragile and difficult to handle. Therefore, another major drawback is that it takes a considerable amount of effort to neatly arrange them in the sintering furnace. Because of these drawbacks, generally speaking, the production of R-Fe-Il sintered magnets not only requires expensive equipment, but also has poor production efficiency and increases magnet manufacturing costs. It gets expensive. Therefore, it is difficult to say that it is a magnet that fully takes advantage of the low cost of R-Pc-B magnets.

Magnets (2) and (3) use a vacuum melt spinning device. This equipment is currently very unproductive and expensive. In (2), since it is isotropic in principle, the energy product is low, and the squareness of the hysteresis loop is not good, so it is disadvantageous in terms of temperature properties and usage. Method (3) is: 1; It is a unique method in which a foot press is used in two stages, but it cannot be denied that it is very inefficient when actually considering mm.

The rare earth-iron permanent magnet according to the present invention solves these drawbacks, and its purpose is to obtain a high-performance, low-cost rare earth-iron permanent magnet.

[Means for solving problems]

The permanent magnet of the present invention is similar to rare earth-iron permanent magnets, and specifically, R is 8 to 30 atomic % and ■ is 2 to 2 atomic %.
8 atomic %% CO50 atomic % or less, A 1151i: i atomic % or less, additive element M (Mg1C1, Srs loa10
1 out of C! Ah! After melting and casting an alloy consisting of 8 atomic % or less, and the balance being iron and other unavoidable impurities, the cast ingot is
The crystal grains are refined by hot working at a temperature of 00°C or higher.

Another feature is that the cast alloy is made magnetically anisotropic by orienting its crystal axis in a specific direction. Furthermore, in order to improve magnetic properties, especially coercive force, 1< is 8 to 25 atomic %, B is 2 to 8 atomic %, and Co 40 is
[1I-r-% or less, A115 atomic% or less. Additive element M (Mg%Cyus S r%B1, l c tv 'l
Chikara 1 a Z I Lt 2 i1i1i) Cast magnet alloy consisting of 8 atomic % or less, with the balance consisting of iron and other impurities unavoidable in manufacturing, and which is magnetically hardened by heat treatment at a temperature of 250°C or higher. It is characterized by full use. In addition, for resin bonding, we take advantage of the property that particles become finer due to hot processing, and even after pulverization for resin bonding, a magnetic phase R*Fc+a is present in each powder.
The present invention is characterized in that a powder containing a plurality of powder particles is prepared, and is kneaded and hardened together with an if machine conveyance inder to form a resin-bonded magnet.

As mentioned above, the current methods of manufacturing rare earth-iron permanent magnets, the sintering method and the rapid cooling method, each have major drawbacks such as difficulty in powder control through pulverization and poor productivity. In order to improve these drawbacks, Iwate et al. conducted research on magnetization in the bulk state, and first disclosed the claims m.
In the composition range of item 1, grain refinement and anisotropy can be achieved through hot working.If the composition range is narrowed to claim 2, sufficient coercive force can be obtained by simply heat-treating the cast state. is obtained.

He also invented the ability to produce resin-bonded magnets by crushing ingots after hot processing. In this method, the anisotropy caused by hot working is not a two-step process like the quenching method shown in Reference 2 (only one step is required, and the coercive force after processing increases significantly due to grain refinement). A completely different
Exhibits IA symptoms.

Also there is no need to crush the casting ingot.

The sintering method does not require any strict atmosphere control, and equipment costs are greatly reduced. Furthermore, resin-bonded magnets do not have the problem of being isotropic in principle like magnets produced by the rapid cooling method, and anisotropic tree 1lfi antagonistic magnetic coupling can be obtained, making it possible to obtain R-Fe-n magnets. It is possible to take advantage of the features of high performance and low cost.

For research on magnetization in the bulk state, see Reference 3,
Hiroaki Miho et al. (Japan Institute of Metals, 1985 Autumn Lecture, Lecture number (544)), but the same research was conducted on Nd10.2.
Fe, 50.7 Co22゜OVl, 3 B9
．． This is due to a small sample taken up by blowing argon gas and dissolving in the atmosphere with a composition of 2. Because of the small amount collected, the crystal grains are sharp. It is thought that this is due to the thinning effect.With this composition, N, which is the main phase in the casting of 1B'
We experimentally confirmed that d*Pe5a port 4 (1 becomes 111 large, and although it is possible to make it anisotropic by hot working, it is difficult to obtain sufficient coercive force as a permanent magnet. In order to obtain sufficient coercive force, claim 2 of the present invention
It is essential to have a low B composition as shown in .

The optimal composition of the conventional R-F c -13 series stone was R+ s Fct t Dm as typified by Reference 1. This composition is the main phase Rt I°C,a
Composition R11,7Fc82.n compound expressed as atomic percentage.
Compared to 4135.0, it has shifted to the side rich in R-[3. This means that in order to obtain coercive force, not only the main phase but also R
This is explained from the point that a non-magnetic phase called a rich phase is required. However, in the composition according to the present invention, on the contrary, 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,
Until now, this has not been much of a problem because the coercive force is drastically reduced. However, in the ordinary casting method, a high coercive force can be obtained only in the composition range specified in claim 2 of the present invention, and on the contrary, a sufficient coercive force cannot be obtained in the B-rich side, which is the mainstream composition of the sintering method. I can't.

These points can be considered as follows. 1 First, whether using the sintering method or the casting method, the coercive force Ui IX? It follows the nucleation and model.

This is because both initial magnetization curves are SmC.

, because it shows a steep rise. The coercive force of this type of magnet is), Since the magnetic domain walls come into contact with each other, reversal of magnetization easily occurs due to the movement of the magnetic domain walls, and the coercive force is small.On the other hand, when the particles become smaller and become smaller than a certain size,
Since the particles no longer have domain walls and the reversal of magnetization proceeds only by rotation, the coercive force increases. In other words, in order to obtain an appropriate coercive force, it is necessary for the Rt Fct a D phase to have an appropriate particle size. This particle size is 1
The average value is around 0tt m, and in the case of a sintered type, the particle size can be adjusted by adjusting the powder particle size before sintering. However, in the case of the casting method, s R* F c141
Since the size of a compound is determined at the stage of melting and solidifying, it is necessary to pay attention to the composition and solidification of the raw material. In particular, the meaning of the composition is thick (if B is included at 8 atomic percent or more, the size of the 11FO+a phase after casting will easily increase to 100%).
μm, and it is difficult to obtain a coercive force in a cast state without using a quenching device as described in Reference 2.

On the other hand, in the low boron region as described in claim 2, the grain size can be easily refined by adjusting the mold, casting temperature, etc. However, in any case, if hot working is performed, the main phases Re Fe, a and B will become finer, so the coercive force will increase compared to before working. From a different perspective, the region where coercive force can be obtained in the cast state can be said to have a composition rich in Fc compared to RmFc+aI3, and in the solidification stage, Fe first appears as an initial product, and then RtFct is produced by a peritectic reaction.
a B phase appears. At this time, the cooling speed is much faster than the equilibrium reaction, so R*
It solidifies in such a way that it is surrounded by the Fe1413 phase. Since this composition range is unbalanced, it goes without saying that the representative composition of the sintered type is Rs * Fe7? The low r ic h phase seen in the 8m magnet can be almost ignored. The surface treatment described in claim 2 is intended to diffuse the initial product Pc and reach an equilibrium state, and the coercive force largely depends on the diffusion of the Fc phase.

Next, resin bonding according to claim 2 will be explained. It is true that resin-bonded magnets can also be produced using the rapid cooling method described in Reference 2. However, the powder created by the rapid cooling method is magnetically isotropic because it is a collection of polycrystals with a diameter of 1000λ or less in the same direction, and an anisotropic magnet cannot be created. The characteristics of low cost and high performance of the B series cannot be utilized.

Moreover, until now, sintered R-Fe-Il&! There are two main reasons why resin bonded magnets could not be manufactured by crushing stones.
There is one. First, the single domain critical radius of the Rt Fct a U phase is one order of magnitude smaller than that of S m Co s, etc.
It is necessary to pay attention to the fact that it is J/order. Grinding to this particle size is extremely difficult with ordinary mechanical grinding, and the powder becomes too activated, resulting in severe oxidation and ignition, resulting in a lack of coercive force relative to the particle size.

We investigated the relationship between particle size and coercive force, but found that the coercive force was no more than a few K Oc at most, and the coercive force hardly increased even with surface treatment. The next problem is distortion caused by machining. For example, if a magnet that has a coercive force of 1 OKOc on a sintered surface is mechanically pulverized, a powder with a grain size of 20 to 30 μm will have a coercive force of less than IKOc. A similar coercive force mechanism (nucleation model)
), such a drastic decrease in coercive force does not occur in SmCO5 magnets that comply with the above criteria, and powder having coercive force can be easily produced. As for the cause of this phenomenon, it can be expected that the influence of processing strain during pulverization is considerably large in the case of R-Fe-13 series. This becomes a big problem when cutting out small magnets such as rotor magnets for watch step motors from sintered blocks.

Due to the above two reasons, namely, the small critical radius and the large influence of processing strain 1N, in normal crushing, the tree I
This means that it was not possible to create an ItI-coupled magnet. In order to obtain a powder with a coercive force of 1, it is sufficient to make a powder with a large number of l<*Fa, aB particles within the grains, as in Reference 2. However, the rapid cooling method of Reference 2 Also, it is virtually impossible to create such a powder by crushing after sintering.This is because the grains grow to some extent and become larger during sintering, so The particle size must be made even smaller by taking into account that amount.However, with such F synthetic leather, the oxygen content of the powder becomes extremely high and the expected performance cannot be obtained. The limit is to set the particle size of the R*Fc+aB phase to 10 μm F'a degree.With this particle size, there is almost no coercive force after pulverization.Therefore, we tried to refine the particles by hot working. After casting, the grain size of the RsFQ+a13 phase was sintered to R-F e −
It is relatively easy to make it comparable to 8 magnets. Then, the cast block having the R1Pc, alj phase with such a grain size is hot worked to refine and orient the grains, and then pulverized. According to this method, resin bonded magnet! 5) Since the particle size of the powder is 20 to 30 μm, there are many R in the powder.
, Pa, and a n particles, and a powder having a coercive force can be produced. Furthermore, this powder is not isotropic as in the quenching method of Reference 2 (but since it is a powder that can be oriented in a magnetic field, it can be made into an anisotropic magnet. Of course, if hydrogen pulverization is applied to the pulverization at this time, , the coercive force is better maintained.

The reasons for limiting the composition of the permanent magnet according to the present invention will be explained below. Rare earths include Y and La%Ce.

! ' rX Nd%Sm, Eu1Gdt Tbs DF
% Mo −, Eu,, T m % Y b X
Lu was mentioned as a candidate, and one of them! II or a combination of one or more types. The highest magnetic performance is obtained with I'r. Therefore, practically P rXNd
, Pr-Nd alloy, Cc-Pr-Nd alloy, etc. are used. Further, a small amount of heavy rare earth element Dy1Tb etc. is effective in improving the coercive force. The main phase of R-F6-B magnet is R1Fe1
All. Therefore, if R is less than 8 atomic percent, the above compound is no longer formed and a cubic crystal structure having the same structure as a-iron is formed, so that high magnetic properties cannot be obtained. on the other hand! SE is 30 atomic%
If it exceeds the Rr ich phase, there will be a large amount of non-magnetic Rr ich phase (and the magnetic properties will deteriorate significantly. Therefore, the appropriate range for 1 C is 8 to 30 at%. However, since it is a cast magnet, it is preferably R8 to 25 Atomic % is appropriate.

B is an essential element for forming the RtFe+ a B phase, and if it is unfilled by 2%, it becomes a rhombohedral R-Fc system, so a high coercive force cannot be expected. Also, if it exceeds 28%
The amount of non-magnetic phase rich in ions increases, and the residual magnetic flux density decreases significantly. However, as a vI magnet, It 8 F;
If the magnetic field is lower than or equal to 'j' or higher, it is not possible to obtain a fine RtFet41 phase unless special ablation is performed, and the coercive force is small.

Co is an effective element for increasing the Curie point of water-based magnets, and basically replaces the Fc site to create R*Co+a
However, this compound has a small crystal anisotropy magnetic field, and as the amount increases, the coercive force as a total magnet becomes smaller. Therefore, I can be considered as a permanent magnet.
In order to provide a coercive force of KOe or more, it is preferable that the single element ratio is within 50%.

A1 is reference 4 Z b a n g M a o
C ai et al. P r o c c e d i n B
so r t it e 8 t hI n
t e n a t i o n a l W o
r k S It OI) on Rare-Ear
111 Magne Ls, 1085. As shown in P541, the effect of increasing coercive force is achieved. This document shows the effect on sintered magnets, but the same effect also exists on cast magnets. However, since AI is a non-magnetic element, increasing the amount added will reduce the residual magnetic flux density, and if it exceeds 15%, the residual magnetic flux density will be lower than hard ferrite, so it will not fulfill its purpose as a rare earth magnet. I don't get it. Therefore, the amount of AI added is preferably 15% or less.

The additive element M (one or more of Mg1Ca1S r and Ba 18 Q) has the effect of increasing coercive force. In addition, these additional elements have the effect of refining grains on the cast structure, thereby improving workability and dispersion in hot working. And these additional elements are
Rare earth metals are sometimes contained as impurities, but because of the effects described above, it is possible to use low-grade rare earth metals that have a high fit for additive M as an impurity, which can help reduce nynost. It also produces effects. However, since the additive element M greatly reduces the residual magnetic flux density, if the additive element M exceeds 8 atomic %, the residual magnetic flux density becomes lower than that of hard ferrite.

In GL, the addition amount kM is preferably 8 atomic % or less.

〔Example! ]

The manufacturing process of the magnet according to the present invention will be explained below.

First, an alloy of the desired composition is melted in an induction furnace, and υI is placed in a mold.
Build. Next, various types of hot working are performed to impart anisotropy to the magnet. In this example, instead of using the general I base method, we used L i q u i (1(I y namic
compaction method (Reference 5, T, S, C1x
in et al., J. App 1. Pbys, 50 (4),
15 Fcbruary 1086.1)1297
) was used. In this example, any one of (1) extrusion, (2) rolling, (2) stamping, and (2) press working was performed at 1000°C as hot working. Regarding the extrusion process, we devised a way to apply force from the goo side so that parts were added in the same direction. Regarding rolling and stamping, the speed of the roll and stamp was adjusted so that the strain rate was as low as possible. In either method, the axis of easy magnetization of the crystal is oriented parallel to the direction in which the alloy is pushed.

An alloy having the composition shown in Table 1 was melted and a magnet was produced by the method described above. However, the hot working method used is also listed in the table.

In addition, the annealing treatment after hot working was performed at 1000° (:
I went for x24 hours.

The results are shown in Table 1.Residual magnetic flux densities of samples not subjected to hot working are shown as reference data.

Table 2 It can be seen from Table 2 that the residual magnetic flux density increased and magnetic anisotropy was achieved by all hot working methods such as extrusion, rolling, stamping, and pressing.

[Example 2] Here, an example using a normal casting method will be introduced. First, the composition shown in Table 3 is melted in an induction furnace and cast into an iron mold to form columnar crystals. After hot working (pressing in this example) at a processing rate of about 50% or more, the ingot was subjected to an annealing treatment at 161000' CX for 24 hours to magnetically harden it. At this time, the average grain size after annealing was about 15 μm. In the case of the casting type, if it is processed into the desired shape without hot working, it will become an in-plane anisotropic magnet that utilizes the anisotropy of columnar crystals.

Table 3 and Table 4 show the magnetic properties of each composition after annealing without hot working and after hot working and then annealing.

Table 4 Here, by hot working (B11) + nax, 1llC
Both showed a significant increase. This is because the titanium was oriented during processing and the squareness of the 1311 curve was significantly distorted. In the quenching method of Reference 2, i II c tends to decrease due to processing, and the significant increase in tllc is a major feature of the present invention.

[Example 3] Here, we will introduce an example in which the material was pulverized after hot processing and bonded with resin. No. in Table 3 of Example 2.

Samples No. 1.2.3.4.7 and 10112.14.10.17 were each ground to a particle size of 30 μm (measured using a Fischer subseep sizer) using a stamp mill/disc mill. At this time, Rs Fct + inside the grain
13 or Rs (Fcce) + 4°B grain size is 2
It was ~3 μfn. Of the 10 types of powder thus made, No. 1, 3, 7, 12, 19 f5) powder was kneaded with 2% by weight of epoxy resin as it was, &! On-site molding and firing. In addition, the powders of N, O, 2.4.10.14 and 17 were treated with Silanno J bubbling agent and then kneaded with Li-Iron 12 at a ratio of 6:4 at about 250"C. After that, injection molding was performed.The results are shown in Table 5 below.

Table 5 [Effects of the Invention] As described above, according to the present invention, coercive force can be obtained only by heat treatment without pulverizing the ingot as in the conventional sintering method. Further, the hot working can be done in one step rather than in two steps as in the quenching method, and the effect is not only an anisotropy effect but also an increase in coercive force. Due to these characteristics, the manufacturing process can be greatly simplified compared to conventional sintering methods and rapid cooling methods. Furthermore, an anisotropic resin bonded magnet can also be produced by crushing the sample after hot working.

that's all

Claims (3)

[Claims] (1) R (R is at least one rare earth element including Y) 8 atomic% to 30%, boron (B) 2 atomic% to
28 atomic% or less, Co 50 atomic% or less, Al 15 atomic% or less, additive element M (one or more of Mg, Ca, Sr, Bu, Be) 8 atomic% or less, and the balance is iron and other manufactured materials. After melting and casting the alloy consisting of unavoidable impurities, the cast ingot is hot worked at a temperature of 500°C or higher to refine the crystal grains and orient the crystal axes in a specific direction. A rare earth-iron permanent magnet characterized by magnetically anisotropic alloy. (2) R (where R is at least one rare earth element including Y) 8 at% to 25 at%, boron (B) 2 at% to 8 at%, Co 50 at% or less, Al 15 at% or less, addition Element M (one or more of Mg, Ca, Sr, Ba, Be) 8 atomic% or less, and the balance consists of iron and other impurities unavoidable in manufacturing, 250
The rare earth-iron permanent magnet according to claim 1, characterized in that a cast magnet alloy is used which is magnetically hardened by heat treatment at a temperature of .degree. C. or higher. (3) Utilizing the property that particles become finer through hot processing,
The method is characterized in that even after pulverization for resin bonding, each powder contains a plurality of particles of magnetic phase R_2Fe_1_4B, and is kneaded and hardened with an organic binder to form a resin bonded magnet. A rare earth-iron permanent magnet according to claim 1.