JPS62244104A - Rare earth-iron permanent magnet - Google Patents

Abstract

PURPOSE:To obtain coercive force under a bulky state, and to simplify a manufacturing process by adding a small quantity of Ni to an R-Fe-B magnet. CONSTITUTION:An alloy consisting of 8-25% R (where R represents at least one kind of rare earth elements containing Y), 2-8% B, 0-15% Ni at an atomic percentage and iron as the remainder is melted and casted so that a casting macrostructure thereof is brought to a colum nar crystal, and the casting ingot is thermally treated at a temperature of 500 deg.C or more and cured magnetically. According to the method, the columnar crystal can be acquired under the state of casting, thus reducing cost, then manufacturing a magnet having high performance.

Description

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

[Conventional technology]

Conventionally, the following three methods have been reported for manufacturing R-Fe-B magnets.

(1) Sintering method based on powder metallurgy (Reference 1) (
2) The quenched thin strip manufacturing equipment used to produce amorphous alloy T-chilled thin strips with a thickness of 30 μms? The thin pieces are made into magnets using a resin bonding method (Reference 2).

(3) A method in which the same flakes used in method (2) are mechanically oriented using a two-step hot press method (Reference Document 2).

References IM, Sagawa, S, Fuji
Mura, N-TogawaH, Yamamoto
Oand YoMa t8 uur! L: J, Ap
pl, Ph7B.

Vol, 55 (6 pieces 1 5 Maroh 1
984. P2O83 Reference 2 RoW, Lee
; Appl, Phys, Lett, Tom.

46(8),-, 15April 1985. P79
The above-mentioned prior art will be fully explained with reference to the above literature. First, in the sintering method, an alloy ingot is prepared by melting and gating, and is crushed into magnet powder having a particle size of about 3 μm.The magnet powder is kneaded with a binder that serves as a forming aid. ,
A molded body is completed by press molding in a magnetic field. The compact is sintered in argon at a temperature around 1100° C. for 1 hour and then rapidly cooled to room temperature. After sintering, the coercive force is further improved by heat treatment at a temperature of around 600°C.

(2) First, R-
A quenched ribbon of JPa-B alloy is made. The obtained ribbon is a ribbon with a thickness of 30 μm, and polycrystals with a diameter of 1000 A or less are aggregated. The ribbon is brittle and easily cracked, and since the crystal grains are distributed isotropically, it is also magnetically isotropic.If this ribbon is made to an appropriate particle size, kneaded with resin, and press-molded, it can weigh up to 7 tons. At a pressure of about /cj, filling of about 85% by volume is possible.

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.
Preheat to 0°C and place in graphite or other heat-resistant press molds. When the ribbon reaches the desired temperature, uniaxial pressure is applied. Temperature and time are not particularly important, but T = near 25 ± 250℃ as a condition for sufficient bloodiness to occur.
A suitable pressure is about P~1.4 ton/-. At this stage, although the magnet is slightly oriented in the pressing direction, it is generally isotropic. The next hot press is
It is carried out in a mold with a large area. Most commonly Fi70
Press at 0° C. and 17 tons for several seconds. Then, the sample becomes 1/2 of its original thickness, the axis of easy magnetization becomes oriented parallel to the pressing direction, and the alloy becomes anisotropic.

These steps are performed using a two-step hot press method (two-st hot press method).
This method, called hot-press process, produces dense and anisotropic R.
-Fe-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 magnetic reds can be manufactured using the above-mentioned conventional techniques, methods for producing t using these techniques have the following drawbacks. In the sintering method (1), it is essential to make the entire alloy into powder, but since R-Fe-B alloys are very active against oxygen, oxidation becomes even more intense when powdered. The oxygen concentration in the solids inevitably becomes high.

Powder again? I-When forming, a forming aid, such as zinc stearate, must be used, which is removed beforehand during the sintering process, but some percentage remains in the form of carbon in the magnet body. It will remain.

This carbon significantly reduces the total magnetic performance of R-Fe-B. 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, in order to arrange them neatly in the sintering furnace,
Another major disadvantage is that it requires considerable effort. Because of these drawbacks, generally speaking, manufacturing R-Pe-B sintered magnets not only requires expensive equipment;
Production efficiency is poor and the manufacturing cost of the magnet increases. 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 methods (2) and (3) use the melt spinning apparatus described above. This device 1/L is currently very unproductive and expensive. Method (2) is isotropic in principle, so the energy product is low, and the squareness of the hysteresis loop is not good, so it is disadvantageous both in terms of temperature characteristics and in terms of use.Method (3) is Although this method uses a hot press in two stages, it is a unique method, but if it is actually used for mass production, it will be very inefficient.

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

[Means to solve all problems]

The permanent magnet of the present invention relates to a rare earth-iron permanent magnet, and specifically, R is 8 to 25 atomic % and B is 2 to 8 atomic %.
After the alloy is completely melted and the cast macrostructure becomes columnar crystals, the Ni-15 light residue is taken from iron and other impurities that are unavoidable in manufacturing. It is characterized by being magnetically hardened by heat treatment at high temperatures.

As mentioned above, the current methods of manufacturing rare earth-iron permanent magnets, such as the sintering method and the quenching method, each have major drawbacks such as difficulty in powder control through pulverization and poor productivity. In order to improve these drawbacks, the present inventors began research on alloys 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, if the casting structure is columnar crystals, it is easier to obtain coercive force, and by utilizing the anisotropy of columnar crystals, an anisotropic magnet can be obtained, so it is better than using equiaxed crystals. He also invented seven things that made it possible to obtain permanent magnets with higher performance. Since this method does not require pulverization of the casting ingot, the sintering method does not require any strict atmosphere control, and equipment costs are greatly reduced. Furthermore, the anisotropy caused by hot processing is different from the original one developed by the quenching method, and only one step is required instead of two, and since the bulk can be processed, not only pressing but also stamping and extrusion are possible, allowing for arbitrary shapes. and productivity increases significantly. Similar research has been carried out by Hiroaki Miho et al. (Japan Institute of Metals, 1985 Autumn Lecture, lecture number (544)), which not only developed the present invention and composition range metal fittings, but also developed macrostructures. There is no mention of any changes in performance, and the performance is also significantly inferior to the present invention. Furthermore, after magnetically hardening, it is very easy to carry out detailed secondary processing to obtain the desired shape, as it has greater bending strength and compressive strength than conventional samarium cobalt rare earth magnets.

The optimal composition of conventional R-Fe-B magnets is sFttsFe, Bl, as typified by Reference 1. This composition is the main phase R of the R-Fe-B magnet.
, re, , B compound vlJt Composition R expressed in atomic percentage
t r, v F ea! , 4"14, it has shifted to the side rich in both R@B elements.

This means that in order to obtain coercive force 7, not only the main phase but also Ru1h
This is explained from the point that a non-magnetic phase called Br1ch phase is required. However, in the composition according to the present invention, on the contrary, a peak value exists where the B content shifts to the side where there is less B. In this composition range, the coercive force decreases dramatically when using the sintering method, so this has not been much of a problem until now. 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.

Is using columnar crystals as a permanent magnet material an alnico magnet? Initially, this was done with rare ±118rrB samarium-cobalt magnets, and one of the present inventors has already reported that 198rrB.
In 2011, the application to resin-bonded samarium-cobalt magnets was announced. (τ, Shimoda et al., Proce
edings of the fifth jncer
HationalWorkshap on Rare
marth-Cobalt PermanentMag
nets, , 1981. P595) In the present invention as well, obtaining columnar crystals in a cast state is an important point for producing a high-performance magnet. That is, the process of obtaining coercive force through heat treatment is due to diffusion, and like Samarius cobalt, it is easier to obtain coercive force with columnar crystals. Furthermore, since magnets originally have a property in which the axis of easy magnetization is oriented in a plane perpendicular to the columnar crystals, it is possible to create in-plane anisotropic magnets by using columnar crystal gold.

The addition of nickel (N1) in the present invention has a close relationship with the formation of columnar crystals described above. Generally R-Fe-B
Although the addition of N1 to the system magnet has the effect of slightly raising the Curie by one point, it was believed that it had a negative impact on the magnetic properties themselves. (Zhang Maocai et al.
ngs of the 8th construction
aIWorkshop on Rare-ICarth
Magnets, 1985. P541) However, in the case of a magnet, on the contrary, addition of up to about 3 atomic % of V increases the coercive force. This is because nickel originally has an effect as a columnar crystallizing agent for magnetic alloys.

The columnar crystallization effect of nickel is well known in the case of steel. In general, elements that promote columnar crystallization are elements in which the interval between the 1g phase line and the solidus line is narrow when considered in a binary phase diagram. The solute distribution coefficient Ko = C8/cz, which is determined by the ratio of the solute concentration at of the liquid phase in equilibrium to the solid phase concentration C8, is less than 1 when left standing, and 1 - Ko, and 0 is greater than 1. In the case of solutes, the smaller the number shown in 1-17, the more advantageous it is to forming columnar crystals. In the case of nickel compared to steel, the value of 1-Ko is small, about cL2,
It is an element that is advantageous for forming columnar crystals. Since aqueous systems contain about 80 at% iron in the composition range where they have the highest performance, it is thought that this concept can be applied to some extent. Originally, the coercive force mechanism of a magnet is due to the diffusion of the segregated F8 element during casting.
Columnar crystals have a faster diffusion rate. From this, it is considered that the effect of forming columnar crystals due to the addition, which was not observed in ordinary sintered R-Fe-BQ stones, also had a favorable effect on the magnetic properties.

The reasons for limiting the composition of the permanent magnet according to the present invention will be explained below. As a rare earth, Y*LaaOe@Pr*Nd55
m*Fu*Ga5Tb*Dy@Ho@ZueTm*Yb
5Lu was mentioned as a candidate, and of these, IT'!
! ,! Alternatively, one or more types may be used in combination. The highest magnetic properties are obtained with Pr. Therefore, practically P
r.Pr-Nd alloy, Ce-Pr-Nd alloy, etc. are used.

Additive elements such as heavy rare earth elements such as D7·τb and AtaMosSi are effective in improving the coercive force. R
The main phase of the -Fe-B magnet is R2Fel4B.

Therefore, if R is less than 8 at %, the above-mentioned compound is no longer formed and a cubic m weave having the same structure as α-iron is formed, so that high air output characteristics cannot be obtained. - If R exceeds 25 atomic %, the nonmagnetic Rrich phase will increase and the magnetic properties will be significantly degraded. Therefore, a suitable range is 8 to 25 atom %.

B is an essential element for forming all the R, Fe, and 4B phases, and if 2 atomic % is not grooved, it becomes a rhombohedral R-Fe system, so high coercive force cannot be expected. If 8 at % or more is added as in the case of 8 atomic % or more, on the contrary, the coercive force in the cast state cannot be obtained.

Therefore, a suitable range for the amount of B is 2 to 8 at%.

As mentioned above, when N1 is added in a small amount of about 3at56, the coercive force becomes 1Hc due to the effect of forming columnar crystals compared to the one without addition.
increases, but if more is added, iHc decreases. If more than 15 atX is added, the magnet will have magnetic properties inferior to those of a ferrite magnet, and the purpose of the magnet's existence will be lost.

Therefore, a suitable range for the amount of N1 is ~15at96.

[Example 1] A complete diagram of the fabrication process according to the present invention is shown in FIG. First, an alloy with a desired composition is melted in an induction furnace and cast into a steel mold to completely form columnar crystals. Next, in order to create an in-plane anisotropic magnet, a sample is prepared by performing secondary processing so that the plane perpendicular to the columnar crystals is in the measurement direction. Furthermore, it is completely heat treated and hardened magnetically. In this example, PrI, Pe4M are representative compositions.
Taking up the composition of N i14 B, the changes in coercive force 1Hc depending on the heat treatment time when heat treated at 1000° C. were compared with the composition Prl 5 Peg 1 E4.

As shown in the second factor, the Ni-containing composition achieves i in a shorter time.
Hc increases and the maximum value is also large. Note that hot working was not performed in this example.

[Example 2] A magnet was prepared by melting the composition shown in Table 1 and using the method shown in FIG. However, in this example, continuous casting by solidification (using a heated mold) is performed on the one hand.Swaging process in an argon atmosphere hot press is then performed as hot processing.
After this was carried out at -800°C, it was annealed at 11,000°C for 24 hours, and was finished by cutting and grinding to a size of 10m% and 0mm, and all magnetic properties were measured. At this time, 20 m is required for hot casting.
%, use a large one with 0 ■.

Table - Table The results obtained are shown in Table 2.

Table 2 [Effects of the Invention] As mentioned above, according to the present invention, it is difficult to obtain a coercive force of 1Hc using conventional sintering methods, and it is possible to obtain coercive force gold in the following composition range, and in a bulk state. The manufacturing process can also be significantly simplified.

[Brief explanation of drawings]

FIG. 1 is a manufacturing process diagram of the rare earth-iron magnet of the present invention. W, Figure 2 is FroffFθyg, 5 Nit, s B
4 alloy and Prl5 Fe111 B. Diagram of coercive force change due to alloy heat treatment. that's all

Claims (2)

[Claims] (1) In terms of atomic percentage, R8 to 25% (R is at least one rare earth element including Y), B2 to 8%, N1
After melting an alloy consisting of 0 to 15% and the balance consisting of iron and other impurities unavoidable in manufacturing and casting the cast so that the cast macrostructure becomes a columnar crystal, the cast ingot is
A rare earth-iron permanent magnet characterized by being magnetically hardened by heat treatment at a temperature of ℃ or higher. (2) 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 rare earth-iron permanent magnet according to item 1.