JPH01318218A - Manufacture of magnetic alloy - Google Patents

Abstract

PURPOSE:To achieve high performance by melting an alloy which basically consists of a rare-earth element, a transition metal and boron, performing cooling in a specific temperature range at a specific cooling rate, and performing a hot processing and heat treatment. CONSTITUTION:An alloy consisting of a rare-earth element, a transition metal and boron is melted and cast and then gradually cooling ingot within a temperature range of 800 to 200 deg.C to avoid a casting effect. If the cooling rate is faster than 5 deg.C/sec, a great thermal distortion results in the ingot. On the other hand, if it is slower than 0.1 deg.C/sec, it takes one hour or more for the ingot to be cooled. Thus, a magnet with anisotropy of high magnetic performance can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic alloy whose basic components are rare earth elements, transition metals, and boron, and in particular to a permanent magnet having mechanical orientation and a method for manufacturing the same. .

[Prior Art] Magnetic alloys are important electrical and electronic materials that are used in a wide range of fields, from permanent magnets and other household appliances to peripheral end devices for large computers. With the recent demand for smaller size and higher efficiency of electrical products, permanent magnets are also required to have increasingly higher performance.

Typical permanent magnets currently in use are alnico, hard ferrite, and rare earth-transition metal magnets. In particular, rare earths (hereinafter abbreviated as R)-transition metals (
Hereinafter, it will be abbreviated as TM. ) type single-stone R-Co-based permanent magnets and R-Fe-B-based permanent magnets have been extensively researched and developed since they provide high magnetic performance.

Conventionally, there are methods for manufacturing these RT M-B permanent magnets as shown in the following literature.

(1) A sintering method based on powder metallurgy.

(Reference 1, Reference 2) (2) Using the melt spinning method, a quenched flake with a thickness of about 30 μm is made using a quenched thin body device used to produce amorphous alloys, and the flake is made into a magnet using a resin bonding method. Resin bonding method using quenched flakes.

(References 3 and 4) (3) A method in which the rapidly cooled flakes used in the method (2) above are mechanically oriented in a two-stage hot press.
(Reference 4, Reference 5) (4) By hot working the cast ingot at a temperature of 500°C or higher, the crystal grains are made finer and the crystal axes are oriented in a specific direction to make the cast alloy magnetically How to make it anisotropic. (Document 6) Here, Document 1; JP-A-59-46008 Document 2; M,
Sagawa, S., Fujimura, N.
Togawa.

H, Yamamoto and Y, Matsuura
;J, Appl, Phys.

Vol, 55 (605March 1984 p20
83 Document 3; JP-A-59-211549 Document 4;
R, W, Lee; Appl, Phys, Le
tt, Vol, 46(8)15 April 19
85 p790 document 5; JP-A-60-100402 document 6; JP-A-62-276803 [Problem to be solved by the invention] By using the above-mentioned conventional technology, R-TM-B
Although permanent magnets can be manufactured, these manufacturing methods have the following drawbacks.

In the sintering method (1), it is essential to turn the alloy into powder, but R-T M-B alloys are very active against oxygen, so if you go through the process of turning them into powder, The surface area increases, oxidation becomes more intense, and the oxygen concentration in the sintered body inevitably increases. Also, when molding the powder, molding aids such as stearin and zinc must be used. Although this is removed beforehand during the sintering process, it remains in the form of carbon within the magnet for several moments.

This carbon degrades the magnetic performance of the R-TM-B magnet, and is therefore not preferred.

The molded body after press molding with the addition of a molding aid is called a green body. It is very fragile and difficult to handle. Therefore, another major drawback is that it takes a considerable amount of effort to arrange them neatly in a sintering furnace.

Furthermore, in order to obtain an anisotropic magnet, press molding must be performed in a magnetic field, which requires large equipment such as a magnetic field power source and a coil.

Because of the above drawbacks, generally speaking, R-TM-B
Manufacturing sintered magnets of this type not only requires expensive equipment, but also reduces production efficiency and increases the manufacturing cost of the magnets. Therefore, R-T M-, which uses relatively cheap raw materials,
It is hard to believe that you can take advantage of the advantages of B-series magnets.

Next, methods (2) and (3) use vacuum melt spinning equipment, which currently has very low productivity and is expensive.

Since method (2) is isotropic in principle, the energy product is low, and the squareness of the hysteresis loop is also poor, so it is disadvantageous in terms of temperature characteristics and usage.

Although method (3) yields an anisotropic magnet, since hot pressing is used in two stages, it cannot be denied that it will be extremely inefficient when considering mass production.

Furthermore, in this method, at high temperatures, for example, 800° C. or higher, the crystal grains become significantly coarsened, resulting in an extremely low coercive force, making it impossible to produce a practical permanent magnet.

Method (4) does not involve a powder process and only requires one step of hot pressing, so it is possible to simplify the manufacturing process the most, but there is a problem that the performance is somewhat inferior.

The present invention solves the above-mentioned drawbacks of the prior art, especially (4) in terms of performance of permanent magnets, and its purpose is to provide a high-performance and low-cost R-TM-B system. It provides a method for manufacturing permanent magnets.

[Means for Solving the Problems] In the method for producing a magnetic alloy whose basic components are a rare earth element (including yttrium), a transition metal, and boron according to the present invention, at least an alloy consisting of the basic components is melted. Cooling rate 0.1-5℃/200℃~800℃
1. A method for producing a magnetic alloy, comprising the steps of cooling for 10 seconds and casting without any casting defects, and hot working and heat treating the hindlimb alloy.

[Function] The present inventors evaluated a large number of R-Fe-B based cast alloys and found that a high coercive force can be obtained by applying appropriate heat treatment to the Pr-Fe-B based alloy, and further, Based on this alloy, we studied mechanical orientation treatment using hot pressing and the effect of additive elements on improving magnetic properties, and found a method for manufacturing high-performance permanent magnets.

That is, the basic ingredients are rare earth elements (including yttrium), transition metals, and boron, and an alloy consisting of these basic ingredients is melted and left, and then a cast ingot is heated to 500°C.
By hot working at the above temperature and excluding the liquid phase of the non-magnetic R-rich phase from the basic components, the magnetic phase is formed. II #, Iδ, is a method for producing a permanent magnet characterized by imparting magnetic anisotropy and mechanical orientation, and is a method that does not include the powder process of flailing, hot working, and heat treatment, and is a method that does not involve the conventional method. It is possible to obtain a magnet with high performance comparable to that of the above.

In this method, casting defects such as cracks, chips, and cavities in the cast ingot greatly affect the subsequent hot working process and product shape. Therefore, it is very important to prevent casting defects such as cracks and chips in the method of manufacturing permanent magnets according to the present method.

In order to prevent defects in cast ingots, the present inventors discovered the following.

In other words, defects in cast ingots mainly occur during solidification shrinkage,
It has been found that casting defects can be avoided by slowly cooling the ingot in a temperature range of 800°C to 200°C.

The reason for the temperature range for slow cooling is that if slow cooling is performed from a temperature exceeding 800° C., the crystal grain size will increase, making hot working difficult and making it impossible to obtain coercive force. Also, 200
If the slow cooling is stopped before the temperature reaches the Curie temperature, SJJ structure defects such as cracks will occur due to distortion as the main phase passes through the Curie temperature. Therefore, the temperature range for slow cooling is preferably 800 to 200°C.

Regarding the cooling speed, if the cooling speed is faster than 5℃/sec, large thermal distortion will occur in the ingot, which will cause casting defects such as cracks in the ingot. desirable. Furthermore, if the cooling rate is slower than 0.1° C./sec, it will take more than one hour to cool the ingot, resulting in poor productivity. Therefore, a speed higher than this is desirable.

Furthermore, casting defects in ingots largely depend on the structure of the ingot. That is, the larger the crystal grains, the more likely casting defects will occur.

It is known that the size of these crystal grains is greatly influenced by the amount of boron, which is a basic component, and that the larger the amount of boron, the larger the grain size. That is, when the atomic percentage is about 4%, relatively fine crystal grains can be obtained, and when the atomic percentage is about 4%, relatively fine crystal grains can be obtained.
℃ temperature range can be cooled at a relatively fast cooling speed to avoid casting defects. However, if the cooling rate is too fast when it exceeds about 6%, the crystal grains will not be able to withstand thermal strain and casting defects will occur in the ingot. In this case, the cooling rate must be slow enough to prevent large thermal strain from occurring.

Examples will be described below.

[Example] Rare earth elements, transition metals, and boron are weighed so as to have the compositions shown in Table 1, and the raw materials are melted and cast in a ceramic crucible in an argon gas atmosphere using an induction heating furnace.

Table 1 The mold is equipped with a heater, and the temperature of the entire SR'ML can be controlled arbitrarily. By preheating the mold to a desired temperature, the cooling rate for each temperature range can be controlled. When the molten metal in the crucible reaches about 1500'C, pour it into the mold.

Tables 2 to 5 show the presence or absence of casting defects such as cracks and chips in the ingots, and the quality of hot workability (good; ○, medium; △, poor; ×) when each ingot was cast under various conditions. Step 3) shows the results of the coercive force of the ingot after casting. The magnet created by this method has nuclihLio from its initial magnetization curve.
It is known to be of the n-type, and the coercive force is a measure of the size of the crystal grains of the ingot. Processing method rating is 10
Judgment was made from the appearance when hot pressing was performed at 00'C.

As shown in the above table, it can be seen that an ingot without casting defects can be obtained according to the present invention.

[Effects of the Invention] As described above, according to the method for producing a magnetic cast ingot of the present invention, it is possible to obtain a good cast ingot without casting defects, and it is possible to obtain a good cast ingot without casting defects, and to crush the ingot by performing casting, hot working, and heat treatment.・Anisotropic magnets with high magnetic performance can be obtained without going through the sintering process.

As a result, the production process for conventional RT M-B permanent magnets can be significantly reduced, which has the effect of increasing the productivity of permanent magnets.

that's all Applicant: Seiko Epson Corporation

Claims (1)

[Claims] In the method for producing a magnetic alloy whose basic components are rare earth elements (including yttrium), transition metals, and boron, at least an alloy consisting of the above basic components is melted,
A magnetic alloy comprising the steps of cooling at a cooling rate of 0.1 to 5°C/sec or less in the range of ℃ to 800°C, casting without casting defects, and then hot working and heat treating the alloy. manufacturing method.