JPH02164007A - Manufacture of rare earth magnet material - Google Patents

Abstract

PURPOSE:To economically and easily obtain a rare earth element-transition metal-semimetal magnet with improved characteristics by causing main material to be alpha-iron or solid solution of cobalt in alpha-iron and rare earth hydride, and heat treating an alloy consisting of mixed texture whose grain size is not larger than 1mu. CONSTITUTION:When a rare earth element R and an alloy, whose main material is alpha-iron or alpha-iron and cobalt, are caused to occlude hydrogen, a material consisting of mixed texture whose main material is alpha-iron or solid solution of cobalt in alpha-iron and rare earth hydride, and whose grain size is not larger than 1mu, is formed. When the mixed texture in this form is caused to be starting raw material and dehydrogenation is effected while heat treatment is carried out, fine grains of R-Fe crystal not larger than 1mu are deposited. Thus an R-Fe magnet with high coercive force and stable characteristics can be obtain without requiring sintering and quenching.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing a rare earth-transition metal-boron based magnet material.

(Prior art and its problems) Rare earth magnets, especially rare earth-iron (especially R-Fe)
- B-based, where R is a rare earth element that may contain yttrium; B may contain other transition metals in addition to iron; B is boron, which may be partially substituted with other semimetals); the magnet material is magnetic; Due to its good properties, it is being actively researched. Among these, industrial methods include the sintering method and the rapid cooling method. R-Fe magnets produced by the sintering method are obtained by melting and cooling a mixture of a predetermined composition, pulverizing, molding, and sintering an ingot. However, since this material is very easily oxidized, the oxidation of the powder progresses during or after crushing and before sintering. As a result, the volume of the metal portion that functions as an effective magnet material decreases, and even if it is molded and sintered, sufficiently high characteristics cannot be obtained. Therefore, strict control of the atmosphere during and after crushing is required. Also, the sintering method requires complicated steps. On the other hand, in the quenching method, a raw material alloy of a predetermined composition melted at a high temperature is rapidly cooled by spraying it onto a cold surface such as a cooling roll to form a scaly or thin layer. However, this method requires large-scale equipment and is difficult to control during rapid cooling.

As a countermeasure against this, the present inventor first developed R-Fe-B
By absorbing a predetermined amount of hydrogen into the alloy obtained by melting the raw material composition of the system magnet, the crystal structure of the RzFezB phase crystal grains, which is the main phase, is loosened to approach an amorphous phase open state, and this is heat-treated to form the main phase again. discovered a phenomenon in which crystals finer than the initial grain size appeared by returning the grain size to
2-199999). Although it is superior in that it allows the production of magnets with good characteristics directly from ingots without using sintering or quenching methods, it is difficult to form a uniform amorphous phase, and a crystalline phase remains, resulting in poor BH left curve squareness. Something happened.

(Objective of the Invention) The present invention utilizes a novel method that is neither a sintering method nor a quenching method, thereby avoiding the complicated process of the sintering method, and also avoiding the quenching method, thereby economically and easily producing rare earth materials with good characteristics. The object of the present invention is to provide an element-transition metal-based semimetal magnet.

(Summary of the Structure of the Invention) The present invention is characterized in that an alloy consisting of α iron or a solid solution of cobalt therein and a rare earth hydride and a mixed structure with a grain size of 1μ or less is heat treated. Fe-based magnet (here R is at least one rare earth element including yttrium, in addition to iron and cobalt, Ni, Mn, Zr,
This method may contain transition metals such as Nb and Ti, and metalloids such as B, Si, P, and Al; however, unavoidable impurities are permitted.

The present invention is also characterized in that an orienting magnetic field is applied in the heat treatment step.

(Summary of Functions and Effects) According to the method of the present invention, an R-Fe-based magnet with high coercive force and stable characteristics can be obtained without requiring sintering or rapid cooling unlike conventional methods. Furthermore, by applying magnetic field orientation, an anisotropic material with high magnetic properties can be obtained.

(Specific Structure of the Invention) As an example of the hydrogen storage conditions proposed in Japanese Patent Application No. 62-199999 cited above, the present inventor has proposed a slow crystalline phase or a soft crystalline phase formed by the process of storing hydrogen at high temperatures. The inventors have found that αFe or a solid solution of cobalt therein and a rare earth hydride can stably exist in the magnetic phase, and have conceived the method of the present invention.

That is, in the present invention, when a rare earth element and an alloy mainly composed of alpha iron or alpha iron and cobalt are allowed to absorb hydrogen, a solid solution of cobalt in alpha iron or alpha iron, and a rare earth hydride are the main ingredients, and the particle size is 1μ. It has been discovered that a substance having the following mixed structure can be produced, and this type of mixed structure is used as a starting material. Then, by dehydrogenating this material while heat treating it, fine R-Fe crystals of 1 μm or less are precipitated. The heat treatment temperature at this time is 500 to 1000
C is preferable, and 700 to 900 C is more preferable. In addition, heat treatment must be performed in a state with a low hydrogen partial pressure, and I
Preferably, the vacuum is below Torr. In crystallization from this mixed structure, an R-Fe system crystal is formed mainly of αFe crystal phase, so that uniaxial anisotropy does not occur. but,
An anisotropic magnet material can be obtained by applying a magnetic field during heat treatment at a temperature lower than the Curie temperature of the α-iron phase (769°C for α-iron, and this temperature increases when cobalt is added). .

Note that the substance consisting of a mixed structure of alpha iron or a cobalt solid solution therein, rare earth hydride, and a particle size of 1μ or less does not need to be formed by hydrogen absorption in the ingot of the raw material mixture; Any method that the tissue can produce can be used. For example, a vapor phase growth method, a mechanical alloy method, etc. can be used.

The present invention is an improvement based on the general concept of the method proposed in Japanese Patent Application No. 199999/1982, but they have the same feature in that a magnet is obtained by dehydrogenation and heat treatment of a hydrogen storage alloy, but in the earlier application, the crystal structure is loosened. However, in the present invention, an extremely uniform final structure can be formed by introducing an intermediate state that is a mixed structure with a clear crystal structure. It is differentiated into Further, as mentioned above, the present invention is disclosed in Japanese Patent Application No. 62-1999.
The mixed structure may be formed by a manufacturing method completely different from that of 99.

A typical rare earth element that can be used in the present invention is Nd, and any rare earth elements such as Mitshu metal and Dy containing various kinds of rare earths can be used. The amount of rare earth element R is 5 to 20 at%, preferably 5.5 to 12'a
t%, and good characteristics can be obtained within this range. Furthermore, the magnetic properties can be improved by adding a metalloid such as B to about 4 to 10 at%. Specifically, by dispersing ferroboron or the like in a mixed structure as an initial material, a magnet with high characteristics can be finally obtained. However, impurities that may be included are allowed. Further, in some cases, when the rare earth element R is small as in the earlier application, additional components such as Zr and Nb described in the earlier application may be added to adjust the coercive force.

The raw material mixture is melted at high temperature, then cooled and solidified to form an ingot. The resulting ingot is then subjected to hydrogen storage, with or without being mechanically crushed. The maximum temperature at this time is 6
The temperature is preferably 00°C or higher, and more preferably 700°C to 1000°C.

Preferred embodiments of the present invention will be described below. However, the alloy composition values are in weight percent.

The raw material is left for a second, then high-frequency melted, and cast to obtain an alloy composition of (1
) Nd-23.0wt%, Zr-2.2wt%, Co-
7,0wt%, B-1,3wt%, Fe-66,5
wt%, (2) Nd-30.5wt%, Dy-2.5
wt%, Al-0.5wt%, B-1.1wt%
, Fe-65,4wt% and (3) MM-20,0wt
%, Nd-10.0wt%, Al-0.3wt%, Nb
-0.8wt%, B-1.0wt%, Fe-67.9w
An alloy ingot of t% (where MM is Mitsushi Metal) was obtained. The container was evacuated at 100"C for 30 minutes, then hydrogen was stored at 1 atm and 100°C for 30 minutes, then evacuated at 200"C for 30 minutes, and then evacuated at 1 atm and 200°C for 30 minutes. Absorb hydrogen for 3 minutes and further heat at 400'C for 3
After evacuating for 0 minutes, hydrogen was stored at 1 atm and 400°C for 30 minutes, and finally, after evacuating at 600''C for 30 minutes, hydrogen was stored at 640°C for 30 minutes, and then the mixture was replaced with argon and allowed to cool to room temperature.

The obtained alloy had a mixed structure of a rare earth hydride compound phase, an αFe phase, and crystal grains (R2Fe14) having a particle size of 1 μm or less by X-ray diffraction and scanning electron microscopy. Moreover, the average particle diameter was about 15μ.

The obtained hydrogen storage alloy was heat treated in vacuum at 800'C (also treated at 400°C as Comparative Example 1 and 1050°C as Comparative Example 2) for 60 minutes, and then heated at 700'C in an argon atmosphere.
, hot pressed for 30 minutes at 3 ton/cm2,
710℃ in argon atmosphere, 0.5-2.0 to
Plastic deformation treatment was carried out at a processing rate of 6o to 80% by unidirectional pressure pressing under the condition of "n/cm".

The results are shown in the following table, and (1), (2), and (3) correspond to the above raw material ingots.

On the other hand, in the case of Comparative Example 1.2 (400°C, 1050'C(7) treatment), iHc was 3 kOe or less.

X standing 1 Nd62. Og, Fe-B (B is 28% by weight)9.5
In a SUS container, 800 g of SUS balls and 5 g of hydrogen gas were added.
The container was sealed with 0 atm and rotated for 96 hours to obtain a powder.

NdHz 48.5g, 82.2g, Co15. Og,
134 g of each powder of Fe was charged into an attritor and stirred at room temperature in an Ar atmosphere for 24 hours. It was confirmed that the powders of Examples 2 and 3 had a mixed crystal structure similar to that of Example 1.

The powder of Example 2.3 was divided and heat treated in vacuum at 700°C for 1 hour (the powder of Example 2 was divided into sample (4), Example 3
sample (5)).

The remaining samples were treated in the same manner while applying a 2T magnetic field (the sample of Example 2 was referred to as sample (6), and the sample of Example 3 was referred to as sample (7)). It was mixed with the obtained powdered epoxy resin, molded at 8 tons/cm'', and heated at 150°C.
It was cured for 2 hours. The powder magnetic properties were measured using a VSM, and the bonded magnet properties were measured using a BHI-laser. The results shown in Table 2 were obtained.

(Specific effects) As is clear from Example 1 and Comparative Example 1.2, the magnetic powder obtained by the method of the present invention has a large coercive force, exhibits excellent magnetic properties, and is Significant improvements in characteristics were seen. Further, as is clear from Example 2.3, it was found that heat treatment in an orienting magnetic field instead of plastic deformation also significantly improved the properties.

Claims (1)

[Scope of Claims] 1) An R-Fe-based magnet ( Here, R is at least one rare earth element including yttrium, in addition to iron and cobalt, Ni, Mn, Zr, Nb,
It may also contain transition metals such as Ti and metalloids such as B, Si, P, and Al. However, unavoidable impurities are allowed). 2) The manufacturing method according to item 1, wherein the heat treatment is performed at a temperature range of 500°C to 1000°C. 3) The manufacturing method according to item 1 or 2, wherein the heat treatment is performed while applying an orienting magnetic field.