JPS6390104A - Manufacture of rare earth-iron-boron permanent magnet - Google Patents

Abstract

PURPOSE:To mass-produce a permanent magnet of high magnetism by means of a simple device by a method wherein, after a hydrogen gas has been occluded into and released from a rare earth-iron-boron ingot more than twice in such a way that this occlusion is processed at 30-300 deg.C, the ingot is pulverized and the obtained powders are molded directly. CONSTITUTION:Before a rare earth-iron-boron permanent magnet is produced, an ingot composed of rare earth, iron and boron is prepared. The molten ingot is put in a hermetically sealed container, and this container is evacuated to produce a vacuum so that a gas adsorbed on the surface of the ingot can be released. The inside of the container is transformed into an atmosphere of hydrogen and the hydrogen is occluded into the ingot. After this hydrogen gas has been discharged and the hydrogen has been released from the ingot, the gas adsorbed on the surface is released again in the same manner in a safe state. The hydrogen gas is occluded and released more than twice in such a way that the occlusion is processed at 30-300 deg.C. After the desired powders have been obtained simply without using a mechanical grinder, the powders are molded directly and are then sintered. A permanent magnet of high magnet ism can be mass-produced by means of a simple device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] This book, 2 Ijl, relates to a method for manufacturing rare earth iron-boron permanent magnets.

[Prior art and its problems]

The currently well-known rare earth iron-boron permanent magnets are: Raw metal elements are high-frequency melted in a predetermined proportion to create an ingot, which is coarsely crushed using a Joe crusher or a brown mill, then finely crushed using a jet mill, ball mill, etc.
It is manufactured by oriented press forming in a magnetic field, sintering, and aging treatment.

However, such an ingot has a higher viscosity than an S m -Co type ingot, and therefore it is difficult to coarsely crush it.

In the fine pulverization process, Mt shift easily occurs in dry pulverizers (jet mills, etc.) (difficult to control particle size). In addition, in a wet grinder such as an attritor, components such as oxygen and carbon that adversely affect the properties are likely to be mixed in.

Furthermore, in the conventional method, a 1-liter crusher and a pulverizer are used separately, which not only complicates the manufacturing process but also requires a large amount of power for crushing, making it difficult to improve the mechanical ability.

[Objective of Part 11] An object of the present invention is to provide a method for economically producing rare earth-iron-boron permanent magnets with good characteristics without using such coarse pulverization and fine pulverization steps.

[Summary of the invention]

The method for producing a rare earth-iron monoboron permanent magnet of the present invention includes:
The following pulverization method can be applied to tjJill made of rare earth elements, iron, and boron.

(1) Place the dissolved MPI spirit in a sealed container and draw a vacuum to remove surface adsorbed gas.

(2) Hydrogen is stored in the ingot by creating a hydrogen atmosphere inside the container.

(3) For safety, after removing hydrogen gas by replacing hydrogen with hr't4, the inside of the container is evacuated. With this operation, the ingot releases hydrogen.

The obtained powder can be molded and sintered as it is to make a permanent magnet.

The rare earth-iron-boron permanent magnet obtained by the method of the present invention has less compositional deviation and less carbon contamination, and in terms of process, it can be produced in one step without mechanical coarse grinding or fine grinding. It can be pulverized, the throughput can be easily increased, and there are advantages such as less loss of expensive rare earth metals during pulverization.

[Detailed description of the invention]

In the present invention, a rare class 2-iron-boron ingot is pulverized using H2 gas. By the way, it is well known that certain metals and alloys absorb and release large amounts of H2.
It is also known that embrittlement of metals and alloys occurs when occlusion occurs. Examples of using a pulverization process using H2 absorption in rare earth-iron-boron based sintered magnets are known (Japanese Patent Application Laid-Open No. 1989-1999).
No. 81304, [No. 10-119701), which is only used for coarse pulverization and requires further mechanical pulverization to obtain raw magnetic powder for sintered magnets. It is.

The present invention is essentially different from the conventional method in that the pulverization is carried out using only hydrogen without using mechanical pulverization.

It is not possible to produce sufficient fine powder as magnetic powder for sintered magnets by just one hydrogen-absorbing pulverization process, so the inventor repeats steps (2) and (3) above at least twice. It has been found that a predetermined fine powder can be obtained by this method.

The hydrogen storage process in (2) above is carried out at temperatures of 30 to 300'C! .

It is preferably carried out at a temperature of 5°C to 2°C. 3
If it is lower than 0°C, the reaction speed will be slow and the efficiency will be low;
At temperatures above 0°C, the amount of absorption is insufficient and the efficiency decreases.

Next, for safety, the surrounding hydrogen gaff is removed using Ar gas or the like, and then the step (3) above is performed for one row to exhaust the inside of the container. This operation releases the occluded hydrogen and progresses the grinding.

By repeating these two steps two or more times, the degree of pulverization progresses, and the properties when magnetized can be further improved.

To describe the hydrogen pulverization process of the present invention more specifically, the airtight container is evacuated to about 10''2 to 10''4 Torr, the container is shut off from the exhaust source, and H2 gas is introduced to several Torr.
rr to several atmospheres, 30 to 300'C Te5 to 160
Hold for 1 minute, scavenge the surrounding H2 gas with Ar gas, and dehydrogenate by exhausting with a rotary pump for 1 hour.

This absorption and release operation is repeated 2 to 910 times.

The rare earth element that can be used in the present invention may be of any type as long as the rare earth-iron-boron magnet has hydrogen storage properties.
One or more of Nd, Dy, Y, 4a, Ce, Gd, Pr, etc. can be used.

In addition to iron, other transition metals 1 such as (o, Ni.

M, n kJ, semimetals such as St and AI along with boron,
Small amounts of other different elements can also be used.

A first embodiment of the present invention will be described below.

: LI Nd30.3wt96i-Dy1.3wt%-B1,
1 wt%-Fe remaining ingot was placed in a sealed container, and 10
Surface gas was removed in vacuum while heating to 0°C.

After that, H2 was absorbed into the alloy in a H22ff atmosphere of 100"02 atm, and then vacuum was drawn again to release H2 gas from the alloy. This absorption and release operation was repeated 20 times to obtain a fine powder. This powder The composition of the ingot was the same as that of the ingot.

The fine powder was pressed in a magnetic field; sintered in vacuum at 1100°C, and then aged in Ar at 590°C for 1 hour to obtain a sintered magnet. This magnet is Br-11,6kG, 5Hc
-12,1kOe, (BH)saw -31,
Tsuta in 9MGOe.

As a comparative example, the same ingot was mechanically pulverized in three stages using a show crusher, a brown mill, and a jet mill to obtain fine powder. This fine powder was pressed and sintered under the same conditions as in the example. The obtained molded body was insufficiently sintered and had a coercive force of less than 1 kOe due to compositional deviation. Further, the Nd content of the fine powder obtained by this mechanical pulverization was as low as 28.2 wt%. This is thought to be the reason why sintering is insufficient.

(Effects) From the above results, it can be seen that the sample pulverized by hydrogen absorption pulverization has no compositional deviation and has high magnetic 9c characteristics.

In addition, since only one crushing device is used, productivity is also good.

Procedural amendment September 14, 1988 Kunio Ogawa, Commissioner of the Patent Office Indication of the case 1988 Patent application No. 2!4568 Title of the invention Person making amendments to the manufacturing method of rare earth-iron monoboron permanent magnets

Claims (2)

[Claims] (1) A permanent magnet characterized by pulverizing a rare earth-iron-boron ingot by occluding and releasing hydrogen gas two or more times, and directly molding and sintering the resulting powder. Production method. (2) The manufacturing method according to claim 1, wherein the occlusion is carried out at a temperature of 30 to 300°C.