JP2639609B2 - Alloy ingot for permanent magnet and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth metal-iron-boron-based permanent magnet alloy ingot having a crystal structure excellent in magnet properties and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, alloy ingots for permanent magnets are generally manufactured by a mold casting method of casting a molten alloy into a mold. However, when the alloy melt is solidified by the die casting method, during the heat removal process of the alloy melt,
Heat transfer is limited in the early stage of heat removal, but as solidification progresses, heat transfer between the mold and solidification phase and in the solidification phase becomes heat removal rate. Ingots have different cooling conditions, and such a phenomenon occurs particularly as the thickness of the ingot increases. As described above, when the difference in cooling conditions between the inside and the surface of the ingot is large, the primary crystal γ-F
e is present in a large amount, so that a grain size of 10 to 1
The α-Fe of 00 μm remains, and at the same time, the size of the rare earth metal-rich phase surrounding the main phase also increases.

On the other hand, in the pulverization process in the magnet manufacturing process, the ingot is usually finely pulverized to several microns, but in the case of the ingot obtained by the die casting method, the particle size is large, which is difficult to pulverize. Since it contains a large phase rich in α-Fe and rare earth metals, the powder particle size distribution after pulverization becomes non-uniform, adversely affects the magnetic orientation and sinterability, and the magnetic properties of the finally obtained permanent magnet Is reduced.

[0004] Further, in the ingot structure obtained by the die casting method, 0.1 to 50 μm in the short axis direction and 0.1 to 50 μm in the long axis direction.
It is known that there is a crystal having a crystal grain size of 100 μm, but the content of the crystal is so small that it does not sufficiently affect the magnet properties.

[0005] Furthermore, after adding a rare earth metal element, cobalt and, if necessary, iron, copper and zirconium, and dissolving them in a crucible, a strip casting method combining a twin roll, a single roll, a twin belt, etc. At 0.01
There has been proposed a method for producing an alloy for a rare earth metal magnet which is solidified so as to have a thickness of about 5 mm.

According to this method, an ingot having a uniform composition can be obtained as compared with the die casting method, but the raw material components are rare earth metal elements,
Since the component is a combination of cobalt and, if necessary, iron, copper and zirconium, there is a problem that the magnet performance cannot be sufficiently improved by the strip casting method.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an alloy ingot for permanent magnets having a crystal structure that has the best influence on the properties of the permanent magnet alloy, and a method for producing the same.

[0008]

According to the present invention, a rare earth element is provided.
Strip cast metal-iron-boron alloy melt
Alloy castings directly obtained by cooling and solidifying by the casting method
Lump, short axis direction 0.1-50 μm, long axis direction 10
A rare earth metal-iron-boron-based permanent magnet alloy ingot containing 90% by volume or more of a crystal having a crystal grain size of 100 to 100 µm or a main phase crystal grain of the alloy has a grain size of 10 µm as a peritectic nucleus.
The present invention provides a permanent magnet alloy ingot in which less than α-Fe and / or γ-Fe is finely dispersed.

Further, according to the present invention, when manufacturing the alloy ingot for a permanent magnet directly obtained by cooling and solidifying a rare earth metal-iron-boron alloy melt by a strip casting method , Through the tundish
Cooling rate 10 by continuously supplying the roll Te
The present invention provides a method for producing an alloy ingot for permanent magnets, which is uniformly solidified under cooling conditions of from about 500 ° C./sec to a degree of supercooling of from 10 to 500 ° C.

Hereinafter, the present invention will be described in more detail.

The alloy ingot for permanent magnet of the present invention is made of rare earth metal.
Strip-castin alloy-iron-boron alloy melt
Alloy casting obtained directly by cooling and solidification by the solidification method
Lump, ie, cooling and solidification by simply strip casting
It is obtained by heat treatment such as hot plastic working.
Alloy ingot, not in the short axis direction 0.1-50μ
m, a rare earth metal-iron-boron based alloy ingot containing at least 90% by volume, preferably at least 98% by volume of crystals having a crystal grain size of 10 to 100 μm in the major axis direction,
It is preferable that α-Fe and / or γ-Fe usually contained as peritectic nuclei are not contained in the main phase crystal grains at all, and when the α-Fe and / or γ-Fe is contained, The particle size of the α-Fe and / or γ-Fe is 10 μm
It is preferable that the ratio is less than and the particles are finely dispersed. At this time, the content ratio of the crystal having the specific crystal grain size is 9
If it is less than 0% by volume, excellent magnet properties cannot be imparted to the obtained alloy ingot. When the lengths in the short axis direction and the long axis direction are out of the above range, or when the α-Fe and / or
If the particle size of γ-Fe is 10 μm or more and the particles are not finely dispersed, the particle size distribution is not uniform during the pulverization in the permanent magnet manufacturing process, which is not preferable.
The thickness of the alloy ingot for permanent magnet is 0.05 to 15 mm.
Is preferably within the range. If the thickness exceeds 15 mm, it is not preferable because a later-described manufacturing method for obtaining a desired crystal structure becomes difficult.

The raw material component forming the alloy ingot for permanent magnet of the present invention is not particularly limited as long as it is a rare earth metal-iron-boron system, and other impurities which are unavoidably contained in normal production. Components may be included. The rare earth metal may be a simple substance or a mixture. Said rare earth metal;
The compounding ratio of boron and iron may be the same as the compounding ratio of the alloy ingot for permanent magnets, and is preferably 25 to 25 by weight.
40: 0.5 to 2.0: preferably the remaining amount.

In the production method of the present invention, the rare earth metal-iron-boron alloy melt is cooled at a cooling rate of 10 to 500 ° C./sec, preferably 10
It is characterized by being uniformly solidified under cooling conditions of 0 to 500 ° C / sec and a degree of supercooling of 10 to 500 ° C, preferably 200 to 500 ° C.

At this time, the degree of supercooling is a value of (melting point of alloy)-(actual temperature of alloy melt) . If the cooling rate and the degree of subcooling are out of the essential ranges, an alloy ingot having a desired structure cannot be obtained.

The production method of the present invention will be described in more detail. For example, a rare earth metal-iron-boron alloy is formed under an inert gas atmosphere by a vacuum melting method, a high frequency melting method or the like, preferably using a crucible or the like. After the melt, the melt is
For example, on a single roll, twin rolls, a disk, or the like, under the above conditions, preferably by a method using a strip casting method such as continuous solidification, etc., an alloy ingot for permanent magnet having a desired crystal structure is produced. Obtainable.
That is, when solidifying by a strip casting method or the like, the thickness of the alloy ingot is preferably 0.05 to 15 m.
It is the easiest method to appropriately select the casting temperature and the pouring rate so as to be within the range of m, and carry out the treatment under the above conditions.

[0016] The alloy ingot for permanent magnet of the present invention is subjected to ordinary pulverization, mixing, fine pulverization, magnetic field pressing and sintering steps, etc.
It can be a permanent magnet.

[0017]

The alloy ingot for permanent magnets of the present invention contains a specific amount of crystals having a crystal grain size of 0.1 to 50 μm in the short axis direction and 10 to 100 μm in the long axis direction. Since it is a boron-based composition, it has excellent pulverizability, sinterability, and the like. Therefore, it is useful as a raw material for permanent magnets having extremely excellent magnet properties. Further, according to the production method of the present invention, a permanent magnet alloy ingot having a composition and a structure excellent in uniformity can be easily obtained at a specific cooling rate and a specific degree of supercooling.

[0018]

The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0019]

EXAMPLE 1 An alloy containing 14 atomic% of neodymium, 6 atomic% of boron and 80 atomic% of iron was made into a molten material by a high frequency melting method using an alumina crucible in an argon gas atmosphere. . Next, after maintaining the temperature of the obtained melt at 1350 ° C., an alloy ingot for permanent magnet was obtained according to the following method using the apparatus shown in FIG. Table 1 shows the results of chemical analysis of the obtained alloy ingot.

FIG. 1 is a schematic view for producing an alloy ingot for a permanent magnet by a strip casting method using a single roll, and 1 is a crucible containing a melt melted by the high frequency melting method. . The melt 2 kept at 1350 ° C. is continuously poured onto a tundish 3 and then cooled on a roll 4 rotating at about 1 m / s at a cooling rate of 500 ° C./sec and a supercooling degree of 200 ° C. Quenched and solidified so that the melt 2 is continuously formed in the rotation direction of the roll 4.
Was dropped to produce an alloy ingot 5 having a thickness of 0.2 to 0.4 mm.

Next, the obtained alloy ingot for permanent magnet was
It was pulverized to 0 to 24 mesh and further pulverized in alcohol to about 3 μm. Next, the obtained fine powder was magnetically pressed under the conditions of 150 MPa and 2400 KAm ~ ¹ , and then sintered at 1040 ° C. for 2 hours to obtain a 10 × 10
A permanent magnet of × 15 mm was obtained. Table 2 shows the magnet properties of the obtained permanent magnet.

[0022]

Comparative Example 1 The alloy melt produced in Example 1 was melted by a high-frequency melting method to obtain a 25-mm-thick alloy ingot for permanent magnets by a die casting method. The obtained alloy ingot was analyzed in the same manner as in Example 1, and a permanent magnet was manufactured. Table 1 shows the analysis results of the alloy ingot and Table 2 shows the magnet characteristics.

[0023]

Example 2 Permanent material was prepared in the same manner as in Example 1 except that an alloy containing 11.6 atomic% of neodymium, 3.4 atomic% of praseodymium, 6 atomic% of boron, and 79 atomic% of iron was used. An alloy ingot for a magnet was manufactured, and the obtained alloy ingot was analyzed in the same manner as in Example 1, and a permanent magnet was further manufactured.
Table 1 shows the analysis results of the alloy ingot and Table 2 shows the magnet characteristics.

[0024]

[Table 1]

[0025]

[Table 2]

[Brief description of the drawings]

FIG. 1 is a schematic view when producing an alloy ingot for a permanent magnet by a strip casting method used in Example 1.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-263404 (JP, A) JP-A-4-28458 (JP, A) JP-B-60-32712 (JP, B2)

Claims (3)

(57) [Claims] 1. A method for producing a rare earth metal-iron-boron alloy melt.
Cooling and solidification by strip casting method
Alloy ingot obtained directly in the short axis direction of 0.1 to 5
A rare earth metal-iron-boron-based permanent magnet alloy ingot containing 90% by volume or more of a crystal having a crystal grain size of 0 μm and a major axis direction of 10 to 100 μm. 2. α-Fe and / or γ-Fe having a grain size of less than 10 μm, which are peritectic nuclei, in the main phase crystal grains of the alloy ingot.
The alloy ingot for permanent magnets according to claim 1, wherein is dispersed finely. 3. A method of directly obtaining a rare earth metal-iron-boron alloy melt by cooling and solidifying it by a strip casting method .
In producing the alloy ingot for permanent magnet according to claim 1, the alloy melt is continuously passed through a tundish.
The cooling rate is 10 to 500
A method for producing an alloy ingot for permanent magnets, wherein the alloy is solidified uniformly under cooling conditions of 10 ° C / sec and a degree of supercooling of 10 to 500 ° C.