JPS62203302A - Cast rare earth element-iron system permanent magnet - Google Patents

Abstract

PURPOSE:To obtain a uniform and high performance permanent magnet with high productivity by a method wherein R-Fe-B system alloy with specific composition is melted and cast by unidirectional solidification and then subjected to a heat treatment at a temperature above a specific value. CONSTITUTION:Alloy composed of 8-25atom% of R (at least one of rare earth elements including Y), 2-8atom% of B and the balance of iron and other impurities which are unavoidable from the manufacturing point of view is melted and cast by unidirectional solidification. Then this cast ingot is subjected to a heat treatment at the temperature higher than 500 deg.C to harden magnetically. Moreover, by employing continuous casting, the productivity can be improved significantly. With this constitution, a coercive force can be obtained under the bulk state and, as the anisotropy of solidified structure can be utilized, a uniform and high performance permanent magnet can be obtained. Moreover, with this method, the cast ingot need not be ground. Therefore, strict environmental control is not necessary.

Description

[Detailed description of the invention] [, Industrial application field] The present invention relates to rare earth chicken-iron permanent magnets.

[Summary of the invention]

In the present invention, the V4-soaked ingot is not subjected to pulverization, sintering, etc., but after being harvested using a solidification method so that the size macrostructure becomes only columnar crystals, it is magnetically hardened by only heat treatment. Furthermore, the present invention aims to obtain rare earth:a-iron permanent magnets by magnetically anisotropically forming them through hot working.

[Conventional technology]

Conventionally, R-1! The following five methods have been reported for producing 'e-B magnets.

(1) Sintering method based on powder metallurgy (Reference 1).

(2) Cold ribbon used to produce amorphous alloys! ! ! ! A quenched thin piece with a thickness of 60 μm and 8 degrees is made using a molding device, and the thin piece is made into a magnet using a bonding method using all resin (Reference 2).
.

(Method of mechanically orienting the same flakes used in method 31+21 using a two-step hot press method (Reference 2)
).

References I M, SagaWa, S, Fujimur
a, N, TOgaWaH,'yamamoto and
Y, Matsuura; J, Appl, Phys.
.

VOl, 55(6), 15 March 198! , P
2O85 reference text #2. R, W, Lee; Appl;
Ph7B, Lett, vol.

46(13), 15 Apri11985. The above-mentioned prior art will be explained with reference to the P790 document. First, in the fil sintering method, an aggregate ingot is produced by melting and casting.
It is crushed into magnetic powder with a particle size of about 5 μm. 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 sintered in argon at a temperature of around 1100°C for 1 hour.
After that, it is rapidly cooled down to the inn TML. After sintering, the coercive force is further improved by heat treatment at a temperature of around 60 G'C.

+21 d, R at the optimum rotation speed of 1zu quenched and made by Tei Seisaku.
-Make a rapidly solidified ribbon of Fe-B alloy. The obtained specimen 94f is a ribbon-shaped gold with a thickness of 60 μm, and polycrystals with a diameter of 10,001 or less are aggregated. The ribbon is brittle and easily cracked, and since the crystal grains are distributed equivocally, it is also magnetically isotropic.If this ribbon is made into an appropriate particle size, kneaded with resin, and press-molded, it will become 7. ton/- under pressure of Cheng Hui, about 85
It becomes possible to fill the volume.

In the manufacturing method (3), first, a ribbon-like quenched ribbon or piece of ribbon is heated in a vacuum or in an inert atmosphere for about 70 minutes.
Place in a graphite or other heat-resistant press mold preheated to 0°C. Uniaxial pressure is applied when the ribbon reaches the desired temperature. Although the temperature and time are not specified, the conditions for sufficient plasticity are T = 725 ± 250°C,
A suitable pressure is P~1, aton/cd8 degrees. Although at this stage the magnet is slightly oriented in the pressing direction.

Overall, it is isotropic. Next hot press.

It is carried out in a mold with a large area. most commonly 700
Press at 0.7 ton for a few seconds at °C. Then, the axis of easy magnetization of the sample becomes oriented parallel to the shibres direction through the initial thickness, and the association becomes anisotropic.

These steps are performed using a two-step hot press method (tWO-8t
This method, called a7ehot-press procedure), produces dense and anisotropic R.
-Pa-B magnets can be manufactured. It should be noted 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 their maximum coercive force, so that coarsening of the crystal grains occurs later during hot pressing. Make sure the particle size is optimal.

[Problem that the invention seeks to solve]

Although R-Fe-B magnets can be manufactured using the above-mentioned conventional techniques, manufacturing methods using these techniques have the following drawbacks. In the sintering method of fil, it is essential to turn the alloy into powder, but since the R-Fe-B alloy is active against oxygen, when it is pulverized, Sokei's acid is violently released. However, the oxygen concentration in the sintered body inevitably becomes high. Furthermore, when molding the powder, a molding aid such as zinc stearate must be used, and this is removed in advance during the sintering process, but several percent of the carbon is added to the back of the magnet. It remains in the form of

This carbon significantly reduces the magnetic performance of R-Fe-B.The molded product after press molding with the addition of a molding aid is called a green product. This fd is very fragile and has poor handling. 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, manufacturing R-Fe-B sintered magnets requires expensive equipment9, production efficiency is low, and magnet manufacturing costs are high. I end up. Therefore, it cannot be said that this is a manufacturing method that can fully take advantage of the low raw material costs of R-Fe-B magnets.

The manufacturing method for 12+ To+31 uses X nitrogen melt spinning metal. This equipment is currently very unproductive and expensive. In (2), since it is 4C,q-tropic in principle, the energy product is low, 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 in which the hot press is applied 1 to 2 times per beak in two stages.
If we actually consider mass production, it cannot be denied that it will be extremely inefficient.

The method of manufacturing an R-Fe-B magnet according to the present invention solves these drawbacks, and its purpose is to:
We offer all kinds of low-cost, high-performance magnets.

[Means to solve all problems]

The permanent magnet of the present invention relates to a rare earth iron-based permanent magnet, and specifically has an R of 8 to 25 atoms and a B force of 12 to 25 atoms.
By melting and melting an alloy consisting of more than 8 atoms, the remainder of which is iron and other impurities unavoidable in manufacturing, and after agreeing using a solidification method, the cast ingot is heat-treated at a temperature of 500 degrees Celsius or higher, It is characterized by being hardened magnetically, and in order to increase the ionizability, it is characterized by using a continuous casting method to obtain a magnet of any shape. ``The cast 11 ingot is characterized by being hot-rolled at a temperature of 1500 C or more to orient the crystal axes of the crystal grains in a specific direction, thereby making the cast 11 ingot magnetically anisotropic.

As mentioned above, the existing methods for producing rare earth-iron permanent magnets, sintering, single head, and cold, each have major drawbacks such as difficulty in powder control through pulverization and poor productivity. In order to improve all of these drawbacks, the present inventors began research on an alloy that can obtain coercive force in the bulk state, and found that it is possible to obtain coercive force in the bulk state with the above composition. At this time, it is easier to obtain coercive force by making the casting structure a unidirectional solidification structure with no disturbance, and since it is possible to fully utilize the anisotropy of the solidification structure, it is possible to achieve more uniform high performance than using a normal solidification structure. He discovered that permanent magnets can be obtained, and that productivity can be greatly increased by applying continuous casting to them, and that it is also possible to make them anisotropic by hot cutting. In this method, there is no need to crush the cast ingot, so the sintering method does not require any strict atmosphere control, and equipment costs are greatly reduced.

Furthermore, the anisotropic molding by hot rolling can only be done in one step, rather than in two stages as in the case of rapid cooling, and the bulk can be molded in one step, so it is possible not only to press, but also to roll, stamp, extrude, draw, etc., and shape it. Arbitrarity and productivity are increased by JL (JL).References 6 Miho Hiroaki et al.
1985 Autumn Lecture, Lecture number% (5A 4)
), but this research not only differs from the present invention in the composition range, but also in terms of performance changes due to macrostructure.
This is not mentioned and the present invention is greatly inferior in terms of performance.

In addition, the secondary processing to obtain the desired shape is also done in the case of heathered yarn.
It has greater bending strength and compressive strength than conventional samarium cobalt rare earth magnets, so it is very easy to work with in cold conditions.

The composition of the conventional R-Fe-B magnet is R0Fθ1. B8 was considered to be the optimal composition. The main phase R, Fθ1 of this composition 1 R-Fe-B magnet
Composition R11, ?4B compound expressed in atomic percentage? Fθ
Compared to 814 BIl and 11, it has shifted to the side rich in both R and B elements. This is explained from the point that in order to obtain coercive force, not only the main phase but also non-magnetic phases called R-rich phase and B-rich phase are required.

However, in the composition according to the present invention, on the contrary, beak saliva exists where B is shifted to the side where there is less B. In this composition range, the coercive force is drastically reduced by the sintering method, so it has not received much attention so far. However, according to the casting method, a high coercive force can be obtained only in this composition range, and a sufficient coercive force cannot be obtained in the normal B-rich side. This is considered to be due to some change in the coercive force mechanism.

On the other hand, solidification method for permanent magnet materials? In addition to alnico magnets, rare earth magnets such as cerium-cobalt-copper-iron cast magnets are used (Reference 4. G, Y).

OR Engineering N 119, Engineering EKK Uranaction
s or Maghevics.

Mo1. MAG-8, 41, Marcn 1972 P
29), and one of the present authors also said that 19)
In 1981, he published the effect of columnar crystal structure as an application to resin-bonded samarium cobalt magnets (References 5. T, 8himodailp,
Proceedings of the fifth 1
ntsrnational Workshop onR
are Earth-Cobalt Permanent
t Magnets, 1981P595). In the present invention as well, obtaining a 10,000-solidified structure in a cast state is an important point for producing a high-performance magnet. That is, nonmagnets acquire coercive force through heat treatment or diffusion, and as with samarium cobalt in Reference 5, it is easier to obtain coercive force when the uniaxial crystal structure is unidirectional and the quasi-solid structure is used. Furthermore, this magnet is easily magnetized in the plane perpendicular to the unidirectionally solidified structure.
! Since ll has the property of being oriented, if you use this, 1
It becomes a plane anisotropic magnet. Generally speaking, the biggest problem with cast magnets is 4.
The fourth point is how to perform anisotropy. For alnico magnets, methods such as controlled cooling in a magnetic field are used, but for heathered yarn, mechanical orientation through hot processing is possible. In other words, magnetization is easy l1IIy during deformation! It has the property of fi orientation. In the case of columnar crystal m weave cast in a normal mold instead of unidirectional solidification, the magnetic properties are not only deteriorated due to the disturbance of one structure (there is a difference in the direction of development of the columnar crystal structure between the periphery of the d-wall and the center). Therefore, it is difficult to achieve uniform orientation even by hot working. However, in the case of unidirectional solidification,
Orientation becomes possible easily even though orientation variation occurs.

The orientation direction is not limited to the vertical and horizontal orientations; radial orientation is also possible when used in rotary swaging, where deformation pressure is applied from multiple directions.

Hereinafter, the rare earths to explain the compositional characteristics of the permanent magnet according to the present invention include Y, La, Ce, Pr, and Nd.

Sm, F'u, Gd, T'b, Dy, Ha, Eu, Tm
, Y'b, and Lu are listed as candidates, and one or more of these may be used in combination. The highest magnetic properties are obtained with Pr. Therefore, practically Pr
.

Pr-N(L alloy, Oe-Pr-Nd@-gold, etc.) are used.

Additionally, a small amount of additive elements 1, such as heavy rare earth elements D7. Tb, Affi, MO, Si, etc. are effective in improving coercive force.

The main phase of the R-IF e -B magnet is RtF'e, 4B. Therefore, if R is less than 8 atoms wide. Since the above compound can no longer be released and forms a cubic crystal structure of -h4ffi, which is the same as α-iron, high magnetic properties cannot be obtained. - If R exceeds 25 atoms, the nonmagnetic Rrich phase increases and the magnetic properties deteriorate significantly. Therefore, a suitable range is 8 to 25 atom %.

B is an essential element for the complete formation of the B phase, and if the ratio is less than 2 atoms, it becomes a rhombohedral R-Fe system, so a high coercive force cannot be expected. However, if the magnet is cooled by a width of 8 atoms or more, as in the case of the conventional magnet made by the I-shaso method, the coercive force in the @-formed state cannot be obtained.

Therefore, a suitable range for the welfare of B is a 2 to 8 atom pot.

[Embodiment 1] An example of a manufacturing process diagram according to the present invention is shown in FIG. First, an alloy of the desired composition is melted in an induction furnace, continuously solidified in one direction using a heated caster, and then hot worked? 500
' to impart anisotropy, then annealing is performed at a temperature range of 500° C. to 1050° C. to perform magnetic fL hardening, and then cutting and grinding are performed to finish the final shape. In this example, the composition shown in Table 41 was melted, and the composition of Table 41 was melted.
The size of 20 mw .

Table 1 The results obtained are shown in Table 2.

Table 2 [Example 2] Example 1 and the group that achieved the highest performance hY Pr 15 F
Using egl B4, the outer diameter is 5 by continuous - ten thousand solidification process.
A tubular sample with an inner diameter of 10 mm and 0 mm was prepared and heated to approximately 900°C using the rotary swaging machine shown in (n) 2.
with an outer diameter of 201. The inner diameter of the sample was 101 mm (fco performance measurement was performed using a belt furnace at 1000℃
After cutting out and performing all the demagnetizing field corrections, I showed the results of vsM to the third person.

Table 46 The performance of this example is the average of 8 samples. As shown in the table, rotary swaging resulted in approximately 80% better performance than normal anisotropic magnets.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain a coercive force in the bulk state in a composition range where a coercive force of 1Hc could not be obtained using conventional sintering methods, and the manufacturing process can also be significantly simplified. can.

4. Brief explanation of tI21 side Issue 1 (S1 is a manufacturing process diagram of the R-Fθ-B magnet of the present invention.

Figure 2, diagram of a rotary swaging machine.

that's all Applicant: Seiko Epson Closed Company Figure 2

Claims (3)

[Claims] (1) R8 to 25% in atomic percentage (where R is at least one kind of rare earth element including Y, B2 to 8%, and the balance is iron and other impurities unavoidable in manufacturing, melting the alloy and unidirectional A cast rare earth-iron permanent magnet characterized by being magnetically hardened by heat-treating the cast ingot at a temperature of 500° C. or higher after casting using a solidification method. (2) The cast rare earth-iron permanent magnet according to claim 1, wherein a magnet of any shape is manufactured using a continuous casting method. (3) A patent claim characterized in that by hot working a cast ingot at a temperature of 500°C or higher, the crystal axes of crystal grains are oriented in a specific direction, thereby making the cast ingot magnetically anisotropic. A cast rare earth-iron permanent magnet according to item 1 or 2.