JPH03247737A - Alloy for rare earth magnet - Google Patents

Abstract

PURPOSE:To obtain a rare earth magnet easily executable of homogenizing and having high capacity by forming the half or above of the cast structure of a rare earth contg. Co alloy of chill crystals. CONSTITUTION:The fundamental compsn. of an alloy for a magnet is formed of a compsn. constituted of rare earth metals including Y and Co, if required, mixed with Fe, Cu, Zr, etc., and the balance inevitable impurities. In the cast structure of this alloy, >=50% is formed of chill crystals (small equi-axed crystals). In this way, its crystalline structure is refined, so that its homogenizing is made easy and its homogenizing heat treatment in a short time is realizable. Furthermore, high coercive force can be obtd. by soln. treatment in a short time. Because the dispersion of the coercive force in a magnet is small, a demagnetization curve having good rectangular hysteresis properties can be obtd. As the rare earth metals, Sm, Y, La, Ce, Pr, Nd, a misch metal or the like are used.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an alloy for rare earth magnets.

[Prior art] Conventionally, the casting structure of alloys for rare earth magnets is usually chill crystals (small equiaxed crystals) made of crystals with a disordered growth method that are nucleated on the interfacial wall. It consisted of columnar crystals grown parallel to the direction of , and equicrystals surrounded by columnar crystals.

Problems to be Solved by the Invention] The heat treatment for this composition system includes a solution treatment to homogenize the structure into a single phase structure, and a subsequent aging treatment to cause decomposition and precipitation.

In this composition system, a high coercive force can be obtained by forming a cellular microstructure that is effective for domain wall pinning after heat treatment, and as a result, high magnetic properties can be achieved. This cellular microstructure can be obtained by aging treatment, but for this purpose, it is important to homogenize the structure sufficiently by solution treatment.

Here, the equicrystals in the cast structure have a problem in that good magnetic properties, particularly high coercive force, cannot be obtained.

Further, although columnar crystals can provide good magnetic properties, they have the problem that homogenization, that is, solution treatment, takes time.

The present invention is intended to solve these problems, and its purpose is to provide an alloy that can easily realize a high-performance rare earth magnet.

[Means for Solving the Problems] The method for producing an alloy for rare earth magnets of the present invention has a basic composition of
It is characterized in that 50% or more of the cast structure of the alloy, which contains rare earth metals, cobalt, and, if necessary, iron, copper, zirconium, etc., and contains impurities that are unavoidable in manufacturing, is chill crystal.

[Function] In the present invention, 50% or more of the cast structure of the alloy is made into chill crystals, which makes the crystal structure finer and makes homogenization, which is important in this composition system, extremely easy. , homogenization heat treatment can be achieved in a short time.

Here, if the chill crystal content is less than 50%, the effect is not much different from the conventional one and is not effective, so the above range is preferable.

Note that Sm-〇〇 permanent magnet is known as a rare earth permanent magnet whose basic composition is composed of rare earth metals, cobalt, etc., but rare earth metals include Sm, Y,
It may be a rare earth metal group such as La, Ce, Pr, Nd, or Mitsushi metal. That is, rare earth metals include Y, La, Ce, and Pr.

Nd, Pm, Sm, Eu, Gcl,
Tb, Dy.

It may be one or more of the rare earth elements Ho, Er, Tm, Yb, and Lu. Furthermore, SmCO5 in which Sm and CO have an atomic ratio of 1:5, and a part of Co replaced with a transition metal group other than Co such as Fe or Cu, such as rare earth metal group such as Sm and Co, Fe, Cu. Sm2(Co) has an atomic ratio of 2:17 with the transition metal group consisting of Zr and Zr.

Fe, Cu, Zr)+7, etc. are known, but the present invention is not limited to a specific composition, as the same effect can be obtained using any composition.

[Examples] Hereinafter, the present invention will be described in detail based on Examples.

3- (Example-1) In both weight ratios, S m 24.7%, Fe
22.9%.

After melting in an argon gas atmosphere using a high frequency melting furnace to have a composition of 5.3% Cu, 1.9% Zr, and the balance CO, it was cast into an iron mold.

It was becoming.

Spread this ingot fully in the thickness direction and cut each ingot into 11
After solution treatment at 50°C for 24 hours and rapid cooling, the sample was held at 800°C for 4 hours and then subjected to continuous cooling aging to 400'C at a cooling rate of 30°C/hour. Furthermore, 10 to 30
The powder was crushed into micrometers, mixed and kneaded with an epoxy resin, oriented in a magnetic field, pressure molded, and then cured to create a bonded magnet of 8x8x12 mm.

FIG. 2 shows changes in ingot position and coercive force (iHc) corresponding to the casting structure. That is, the horizontal axis of FIG. 2 approximately corresponds to that of FIG.

As can be seen from FIG. 2, the outer chill crystal and columnar crystal parts have high coercivity, whereas the central equicrystalline part has a considerably low coercive force.

(Example-2) Using the ingot of Example-1, it was cut into chill crystal, columnar crystal, and equiaxed crystal parts, each of which was heat-treated at various solution treatment times, and treated in the same manner as Example-1. It was made into a bonded magnet.

Figure 3 shows the relationship between solution treatment time and coercive force for chilled crystals, columnar crystals, and equicrystals; however, it is difficult to obtain high coercive force with equicrystals, and it takes time to obtain high coercive force with columnar crystals. On the other hand, it can be seen that a high coercive force can be obtained with the chilled crystal even after a short solution treatment.

(Example 3) Table 1 shows typical magnetic properties of bonded magnets prepared under optimal conditions for the chill crystal, columnar crystal, and equicrystal of Example 2.

Table 1 As can be seen from Table 1, equicrystals cannot obtain sufficient coercive force and the squareness of the demagnetization curve is also poor, making it impossible to obtain high magnetic properties. Higher magnetic properties can be obtained compared to crystals. In contrast, chill crystals not only require a shorter solution treatment time, but also have higher magnetic properties.

This means that in the present invention, not only can a high coercive force be obtained through short-time solution treatment, but also that a demagnetization curve with good squareness can be obtained because the variation in coercive force within the magnet is small. It shows.

(Example 3) In both cases, S m 11.7%, P r
11.0%.

Fe 16.0%, Cu6.6%, Zr3.
The composition was adjusted to 3% Co and the balance was Co, and an ingot having a cast structure consisting of chilled crystals and columnar crystals was produced. Here, in order to change the quantity ratio of chill crystals, we changed the thickness of the mold and used twin-roll strip casting in some cases.

The alloy obtained here was solution treated at 1150°C for 1 hour using the same method as in Example-1.

A bonded magnet was produced by aging at 800°C for 8 hours.

FIG. 4 shows the change in iHc depending on the amount ratio of chill crystals.

If long-term solution treatment is performed, a high coercive force can be obtained even with a small amount of chill crystals, but in such short-term solution treatment, it is desirable that at least 50% of chill crystals exist. .

It is also clear that the present invention is not dependent on the means or composition used to obtain the alloy.

[Effects of the Invention] As described above, according to the present invention, an alloy whose basic composition consists of a rare earth metal, cobalt, and, if necessary, iron, copper, zirconium, etc., and impurities unavoidable in manufacturing. Because more than 50% of the cast structure is chill crystal, not only can the solution treatment be completed in a short time, but also the heat treatment time can be shortened, and homogenization can be completely achieved. A rare earth magnet with high magnetic properties is obtained,
Furthermore, by using this, for example, a high-torque motor can be realized, and it has a great effect in terms of application.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the casting structure. FIG. 2 is a diagram showing the relationship between ingot position and coercive force. FIG. 3 is a diagram showing the relationship between solution treatment time and coercive force for chill crystals, columnar crystals, and equicrystals. FIG. 4 is a diagram showing the relationship between the amount ratio of chill crystals and coercive force. Above Figure 1

Claims (1)

[Claims] (1) The basic composition is rare earth metal (at least one rare earth element including Y: hereinafter abbreviated as R), cobalt, and if necessary, iron, copper, zirconium, etc. are added, and it is unavoidable in manufacturing. An alloy for rare earth magnets, characterized in that 50% or more of the cast structure of the alloy consisting of impurities is chill crystals (small equiaxed crystals).