JPH0562814A - Method of manufacturing rare-earth element-fe-b magnet - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing with excellent producibility a rare-earth-Fe-B magnet with excellent magnetic characteristics and with no drawback unlike the prior art. CONSTITUTION:Molten alloy 1 containing at least rare-earth element, Fe and B as essential components is dropped in a non-oxidation atmosphere. To the dropping molten alloy 1 high-pressurized inert gas is jetted and the alloy is atomized, and atomized rare-earth-Fe-B alloy powder in a half-fusion condition is uniformly accumulated on a collector 4 provided in the lower part of an atomizer to form a preform body 5, which is sealed within a metallic cupsule and performed hot working, so that a main axis of crystal magnetic anisotropy is arranged in the process direction and magnetically made anisotropic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rare earth element-Fe-B magnet having an alloy structure with excellent orientation, and more specifically, a preform body is formed from a rare earth element-containing alloy powder. The present invention relates to a method for producing a rare earth element-Fe-B based magnet having excellent magnetic properties by encapsulating a reform body in a metal capsule and hot working. Note that the hot working in the present invention includes any of hot working, hot forging, and hot isostatic pressing, but the description will be made mainly on hot rolling below.

[0002]

2. Description of the Related Art Rare earth magnets have been attracting attention as a third permanent magnet after ferrite magnets and alnico magnets. Among these, the rare earth element-
It is a permanent magnet of Fe-B system (hereinafter sometimes abbreviated as RE-Fe-B system), for example, Nd-Fe-B, Pr-Fe-B, etc., and Cu and Ag are the fourth permanent magnets recently. It is also being studied to use it as a constituent element and to add other trace elements in addition to it.

There are three known methods for manufacturing RE-Fe-B magnets. The first method is a powder metallurgical method (sintering method). In this method, first, rare earth elements, electrolytic iron, ferroboron, etc. are melted, and the obtained rare earth element-Fe-B system molten alloy is forged with a water-cooled copper mold to obtain an alloy ingot. Next, the alloy ingot is pulverized into a fine powder of 3 to 10 μm, the obtained alloy powder is molded in a magnetic field, and sintered in an Ar gas atmosphere.

In the second method, a rare earth element-Fe-B system molten alloy is rapidly cooled and solidified to form a thin piece, which is hot-pressed and further pressed by a die-up set to magnetize the crystal in the pressing direction. This is a method of manufacturing an anisotropic magnet by aligning the principal axes of anisotropy.

The third method is a method in which a rare earth element-Fe-B alloy is hot-rolled and the principal axis of crystal magnetic anisotropy is aligned in the rolling direction to produce an anisotropic magnet. In this method, it is also known that the alloy ingot is enclosed in a metal capsule and hot-rolled.

[0006]

However, in the powder metallurgical method, since the rare earth element-Fe-B alloy is active, the powder may be easily oxidized and impurities may be mixed. As a result, there is a problem that the oxygen concentration and the impurity concentration in the sintered body increase and the magnetic characteristics deteriorate. Further, powdering treatment of the alloy is required prior to the sintering step, which is difficult in terms of productivity.

On the other hand, the method of hot-pressing and die-upsetting the rapidly-quenched flakes requires not only expensive equipment such as a magnetic field press and a rapid solidification apparatus, but also has poor productivity, and is not suitable as an industrial means. There is a drawback. The method of hot working the alloy ingot can be said to be suitable for mass production, but it has a drawback that an alloy ingot having fine columnar crystals must be prepared.

The present invention has been made in view of such circumstances, and its purpose is to provide RE-Fe-B excellent in magnetic characteristics without causing the inconvenience of the prior art.
An object of the present invention is to provide a method for manufacturing a system magnet with high productivity.

[0009]

Means for Solving the Problems According to the present invention capable of achieving the above object, a molten alloy containing at least a rare earth element, an Fe system and B as essential components is dropped into a non-oxidizing atmosphere, and during the dropping. Atomized by spraying a high-pressure inert gas onto the molten metal, and the atomized semi-molten rare earth element-Fe-B alloy powder is uniformly deposited on the collector provided at the bottom of the atomizer to form a preform body. A rare earth element having the gist of forming a preform, encapsulating the preform in a metal capsule, and performing hot working to orient the principal axis of the magnetic anisotropy of the crystal in the working direction to make it magnetically anisotropic. It is a manufacturing method of a -Fe-B system magnet.

It is also effective that the temperature during hot working is 700 to 1050 ° C., it is also effective to perform heat treatment at 800 to 1050 ° C. after completion of hot working, and then heat treatment at 400 to 600 ° C. The magnetic characteristics can be further improved by adding these requirements.

[0011]

The present inventors basically include a step of hot working using a metal capsule, and do not cause the problems described in the section of the prior art, and have excellent magnetic properties.
-We examined the requirements for manufacturing B-based magnets from various angles. As a result, a preform body is formed from powder in a semi-molten state obtained by atomizing the molten R-Fe-B alloy, and the preform body is encapsulated in a metal capsule and subjected to hot working. The present invention has been completed by finding that the object can be achieved successfully. That is, according to the present invention, atomized powder in a semi-molten state is deposited on a collector to prepare a preform body, which is encapsulated in a metal capsule and subjected to hot working. It is possible to omit the crushing step, and it is possible to form a clean preform by preventing adhesion of oxides and mixing of impurities, and it is possible to prevent deterioration of magnetic properties from the raw material side. Further, there is no need for expensive equipment such as a magnetic field press and a rapid solidification device. Further, since the atomized powder has a particle size of 250 μm or less, the crystal grain size of the preform can be made as fine as 10 μm or less, which results in a good coercive force (iHc). Can be secured.

The alloy composition of the RE-Fe-B magnet of the present invention will be described. First of all, as rare earth elements,
La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, T
Lanthanum series rare earth elements such as b, Dy, Ho, Er, Tm, Yb and Lu are generally used, but if necessary, actinium series elements can be used, and one or two kinds selected from these can be used. The above is used in combination. Of these, particularly preferable are Pr, Ce, Nd and the like.

The composition ratio of each element in the RE-Fe-B system magnet according to the present invention is not particularly limited,
Generally, it is recommended to select according to the following criteria.

The rare earth element is suitably 8 to 25 atomic%,
If it is less than 8 atomic%, the main phase RE in the above ternary permanent magnet
_2- Fe ₁₄ -B (atomic ratio, for example, Pr ₂ -Fe ₁₄ -B) cannot be formed, resulting in a cubic crystal structure having the same structure as α iron, leading to a decrease in iHc, and good magnetic properties. Characteristics cannot be obtained. Further, the hot workability is deteriorated, and cracks are likely to occur during hot working. On the other hand, with respect to the upper limit, if it exceeds 25 atom%, the amount of the non-magnetic phase becomes too large and good magnetic properties cannot be exhibited.

B is preferably in the range of about 2 to 10 atomic%, and if it is less than 2%, the volume ratio of the main phase becomes indefinite and the magnetic flux density (Br) is lowered. On the other hand, regarding the upper limit, R that does not bear magnetic characteristics
From the viewpoint of preventing a decrease in iHc due to the appearance of the E ₁ —Fe ₁₄ —B ₄ phase, 10 atomic% may be set as a standard.

In addition to the above essential components, the balance is basically Fe.
Fe is an essential element for forming a magnetic phase, and a part of Co, Al, Cu,
You may substitute by Ga, Ag, Nb, V, etc. Co has an effect of improving magnetic temperature characteristics, Al has an effect of suppressing a decrease in iHc, Cu and Ga have an effect of increasing iHc, and Ag, Nb, V and the like have an effect of refining the structure. ..

In the present invention, RE-Fe having the above composition is used.
-The B-type alloy melt is atomized and the atomized semi-molten RE-Fe-B-type alloy powder is deposited on the collector to form a preform body, but the shape of the preform body is limited. For example, a flat plate shape or a cylindrical shape can be prepared. The procedure for creating preforms of various shapes will be described with reference to the drawings.

FIG. 1 is a schematic explanatory view showing an apparatus structure for producing a flat plate-like preform. In the figure, 1 is a molten alloy, 2 is a molten alloy tank, 3 is a chamber for forming an inert atmosphere, 4 Is a plate-shaped collector, and 5 is a preform body.

The molten alloy 1 is dropped from the molten alloy tank 2,
During the fall, an inert gas such as Ar gas is blown at a high pressure (not shown), and the molten metal is atomized into semi-molten fine droplets, which is provided in the lower part of the atomizer and moves horizontally. The flat preform body 5 is formed by uniformly depositing the preform body 5 on top.

FIG. 2 is a schematic explanatory view showing the construction of an apparatus for producing a cylindrical preform body. The basic construction of this apparatus is the same as that shown in FIG. The same reference numerals are attached. In the apparatus shown in FIG. 2, a cylindrical collector 4a is provided in the lower part of the molten alloy bath with its axial direction oriented in the horizontal direction. The collector 4a rotates about the axial center while it is in the axial direction. Be moved to. R is placed on the collector 4a by using such a device.
By depositing the E-Fe-B based alloy powder uniformly, a cylindrical preform body 5a is obtained.

The preform as described above is housed in a metal capsule, but in view of the fact that the hot working in the present invention is performed at a relatively high temperature, the metal capsule has a higher melting point than the preform, For example, mild steel with a melting point of 1500 ° C or higher,
Structural steel and even stainless steel are used.

FIG. 3 is an explanatory view showing a form of a hot working billet 7 formed by enclosing the flat plate-shaped preform body 5 in a metal capsule 6. When the billet 7 having such a form is used for hot rolling or hot forging, the principal axis of the magnetic anisotropy of the crystal can be oriented in the processing direction to make it magnetically anisotropic.

FIG. 4 is a sectional explanatory view showing a form of a hot working billet 7a formed by degassing and enclosing a cylindrical preform body 5a in a metal capsule 6. In the figure, 8 indicates a deaeration hole. If hot extrusion is performed using the billet 7a having such a form, the magnetic anisotropy of the crystal can be oriented in the radial direction of the cylinder to be magnetically anisotropic.

Each of the above billets is hot-worked, and the hot-working temperature is about 700 to 1050 ° C. regardless of which hot rolling, hot forging or hot extrusion method is adopted. Preferably. If the temperature is less than 700 ° C, cracking of the magnet material is likely to occur during hot working, and the crystal orientation will be poor.
On the other hand, the higher the hot working temperature, the better the crystal orientation, but if the temperature exceeds 1050 ° C, the crystal grains become coarse and the magnetic properties deteriorate.

In order to achieve high orientation, it is necessary to increase the working ratio during hot working as much as possible. For example, the reduction ratio should be 30% or more in hot rolling and the extrusion ratio 5.0 or more in hot extrusion. is there. The cooling conditions after hot working may be appropriately set according to each working method. For example, after hot rolling, it is preferable to set the cooling rate to 50 ° C / min or less. The characteristics may not be obtained, and cracks may occur due to the difference in thermal expansion between the metal capsule and the magnet material. Cooling after hot extrusion should be carried out at a cooling rate of 50 ° C / min or higher between 1000 and 500 ° C.
If it is less than / min, good magnetic properties cannot be obtained.

In the present invention, as described above, after the hot working is completed, heat treatment at 800 to 1050 ° C. and further heat treatment at 400 to 600 ° C. are preferable embodiments.
This is because the microstructure is achieved by the two-step heat treatment and the characteristics of the magnet are further improved.

[0027]

Example 1 A Pr—Fe—B alloy having the composition shown in Table 1 was melted, the molten alloy was dropped, and a high-purity and high-pressure Ar gas was blown during the fall to obtain a semi-molten powder. The powder was deposited on a flat plate-shaped collector provided under the atomizer to obtain a preform for hot rolling.

[0028]

[Table 1]

The preform was encapsulated in a steel capsule to prepare a billet for hot rolling (see FIG. 3).
This billet was hot-rolled at a rolling reduction of 76% and a rolling temperature of 1000 ° C., and then heat-treated in two stages of 1050 ° C. (first stage) and 475 ° C. (second stage) to obtain a magnet material. .. When the magnetic properties of the magnet thus obtained were investigated, the results shown in Table 2 were obtained. In Table 2, (BH) max is the maximum energy product shown by the product of the residual magnetic flux density and the coercive force. As is clear from Table 2, the magnet material obtained according to the present invention exhibits excellent magnetic characteristics.

[0030]

[Table 2]

Example 2 A hot-extrusion preform body was prepared in the same manner as in Example 1 except that a Pr-Fe-B alloy having the composition shown in Table 1 was melted and a cylindrical collector was used. did.

A steel capsule was filled with the above-mentioned preform and degassed and sealed to prepare an extrusion billet (see FIG. 4). This billet has an extrusion ratio of 10 and an extrusion temperature of 1000.
After hot extrusion at ℃, cooling rate 300 ℃ / min
The sample obtained by cooling at 1050 ℃ (1st step) and 480 ℃
A two-step heat treatment at ° C (second step) was performed to obtain a magnet material.
When the magnetic properties of the magnet thus obtained were investigated, the results shown in Table 3 were obtained. As is clear from Table 3, the magnet material obtained according to the present invention exhibits excellent magnetic properties.

[0033]

[Table 3]

[0034]

As described above, according to the present invention, it becomes possible to easily manufacture a magnet having good magnetic characteristics without requiring expensive equipment such as a magnetic field press and a rapid solidification machine. The present invention is suitable as an industrial production method. Further, the step of crushing the ingot is not required, and there is no adherence of oxides or mixing of impurities, and it is possible to effectively prevent the deterioration of magnetic characteristics due to these.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an apparatus configuration for producing a flat plate-shaped preform body.

FIG. 2 is a schematic explanatory view showing an apparatus configuration for producing a cylindrical preform body.

FIG. 3 is an explanatory view showing a form of a hot working billet 7 formed by enclosing a flat plate-shaped preform body 5 in a metal capsule 6.

FIG. 4 shows a cylindrical preform body 5a with a metal capsule 6
It is a section explanatory view showing the form of the billet 7a for hot workings formed by degassing and enclosing it inside.

[Explanation of symbols] 1 molten alloy 2 molten alloy tank 3 chamber 4,4a collector 5,5a preform body 6 metal capsule 7 hot working billet

Claims (2)

[Claims] 1. A molten alloy containing at least rare earth elements, Fe and B as essential components is dropped into a non-oxidizing atmosphere, and a high-pressure inert gas is blown to the molten metal to atomize the molten alloy. A semi-molten rare earth element-Fe-B alloy powder is uniformly deposited on a collector provided at the bottom of the atomizer to form a preform body, and the preform body is enclosed in a metal capsule and hot-worked. A method for producing a rare earth element-Fe-B magnet, which is characterized by performing processing and orienting a principal axis of magnetic anisotropy of a crystal in a processing direction to magnetically make it anisotropic. 2. The production according to claim 1, wherein the hot working is performed at 700 to 1050 ° C., and after the hot working is completed, the heat treatment is performed at 800 to 1050 ° C., and then the heat treatment is further performed at 400 to 600 ° C. Method.