JPS62133040A - Rare-earth permanent magnet material - Google Patents

Abstract

PURPOSE:To prevent deterioration in magnetic properties of permanent magnets by controlling C and O2 content in powdery raw material in manufacturing a permanent magnet composed mainly of iron, rare earth elements, and boron by powder compacting method. CONSTITUTION:An iron-rare earth element-boron alloy which is composed of an Fe alloy having a composition containing, by weight, 25-40% R (at least one element among Y and rare earth elements) and 0.7-2.5% B and having the balance consisting of Fe or Fe and at least one element among Co, Al, Nb, and Si and in which C and O2 content is regulated to <=0.05% and <=0.3%, respectively. An ingot of this Fe-base alloy is pulverized, and the resulting powder is oriented in the magnetic field and compacted. The green compact is sintered at 1,050 deg.C to be formed into permanent magnet. In the above, C and O2 content is controlled to a minimum, respectively, so that permanent magnets excellent in magnetic properties can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is widely used in various industrial and domestic electrical appliances. Related to rare earth permanent magnet materials.

(Prior art and its problems) Conventionally, when trying to manufacture permanent magnets whose main component is rare earth iron boron by powder molding, the raw materials are very active, so
There was a problem in that the powder deteriorated severely, preventing densification in the sintering process and reducing magnetic properties. The cause of this is generally thought to be oxidation of the fine powder, and methods such as melting, crushing, molding, and sintering are performed in air or in a reducing or non-oxidizing atmosphere to suppress oxidation as much as possible. It's here. Recently, in addition to these methods, a method of suppressing oxidation by adding a highly active element as a fourth component has been proposed (see Japanese Patent Application Laid-Open No. 60-12707), but despite these efforts, It has not yet been possible to completely prevent the deterioration of magnetic properties during the manufacturing process.

- On the other hand, many studies have been conducted on the influence of small amounts of components in the magnet material Neko 1. For example, in JP-A-59-132105 and JP-A-163803, the content of Cu, S, C, and P is If you limit it to below a certain value, it will not affect the magnetic properties! It has been shown that it is sufficient to suppress C to 2 atomic % or less, and that complete removal of C from the organic binder used during molding is not a problem.

(Step-L to solve the problem) Unexploded 1!11 The authors believe that the phenomenon of decrease in magnetic retention during the manufacturing process described above is not due to oxidation of the fine powder, but is due to the presence of other minute components. Suspecting that these components may have a strong effect on magnetic properties, we conducted research on materials in which these components were reduced as much as possible, and as a result, we found that C and 0 minutes were responsible for the decline in magnetic properties. This discovery led to this invention. In other words, when manufacturing rare earth iron boron magnet materials, the purpose is to provide a high-performance permanent magnet material that prevents deterioration of fine powder and does not cause deterioration of magnetic properties, and aims to achieve this goal by specifying the material composition. It is.

(Structure of the Invention) The present invention comprises R of 25 to 40% (wherein R is at least one of Y and a rare earth element) and 0.7 to 2
．． 5% B, 0.05% or less C, less than 0.3% O, and the balance M (M is Fe, Co.

The gist of the present invention is a rare earth permanent magnet material characterized by being made of at least one of Al, Nb, and Si containing Fe. The modification of the permanent magnet of the present invention is to reduce the C and O contents as much as possible. CH,
; is a fine powder degraded product 1 in the manufacturing process; and iHC
In order to prevent a decrease in the content, it is necessary to suppress the content to 0.05% or less. The reason for this is that even if it is 1-1 or more, usable magnetic properties can be obtained, but the more fine powder is left in the atmosphere, the more the powder deteriorates and becomes difficult to handle. If the amount of C is less than 0.05%, the magnet fine powder will not deteriorate (this is because the C content will increase.) Therefore, when manufacturing this permanent magnet, use materials with as little C as possible as raw materials. , grinding is done by dry grinding using a disc mill, jet mill, etc.
When molding, it is desirable to avoid the use of binders as much as possible.

Further, it is necessary to keep the content of Oj city to less than 0.3% by weight in order to lower the sintering temperature and improve magnetic properties, especially saturation magnetization (4πIs). Conventional methods only reduced the amount of 0 to 0, but the present invention found that by simultaneously reducing the amount of C and O, powder deterioration was less likely to occur, and the amount of 0 was reduced to 0. The reason for limiting it to less than 3% is based on the following considerations. That is, C,! :O forms carbides and oxides with rare earth elements, respectively, but rare earth carbides are highly hygroscopic and are finally transformed into rare earth oxides through the following reaction.

R2C5+mH2O→R2C5ΦmH2OR2C3-m
H2O:900"Q-R203+nC2H,.

Such carbides and oxides form a thin film on the surface of the fine powder and hinder grain growth during the sintering process. In particular, in the RFeB magnet material No. 1, a liquid phase coexists in the sintering temperature range, and this liquid phase is present on the surface of the fine powder. It is thought that the sintered body becomes dense because it serves to remove J and concentrate it in the liquid phase. However, since a large amount of liquid phase must be present to remove this surface thin film, as a result, the madris phase (R2Fe, 4B phase) responsible for magnetism decreases, and the magnetic properties deteriorate.

When C and O are present in large amounts, densification is hindered because there is not enough liquid phase to remove the fine powder surface film.

In order to reduce this oxygen content, melting, crushing, molding, sintering,
It is desirable to carry out each step of heat treatment, including the storage of fine powder, in air or in an inert, non-oxidizing or reducing PL atmosphere, and also to cut off contact with air by coating or vapor depositing the powder surface. It is also effective.

On the other hand, R, which is the main component of the permanent magnet of the present invention, is Y or at least one type of rare element, and its composition is 2.
It is 5 to 40% by weight. When R is less than 25%, the coercive force (i
Hc) suddenly decreased to less than 1 KOe, and 40%
Above this, the activity of the fine powder becomes too strong, making it easy to ignite, and the saturation magnetization (4πIs) also decreases. B is present in an amount of 0.7 to 2.5% by weight, and if it is less than 0.7%, the iHc is low and it is not suitable for practical use as a magnet, and it prevents densification. Moreover, above 2.5%, the saturation magnetization decreases significantly, and the maximum energy product [(
BH) wax]. Fe in the remainder M
, An, Nb, and Si, excluding Co, have the effect of increasing iHc.

(Example) Next, the present invention will be explained in detail.

Example 1 Nd: 95%, Pr: 2.
5%, Fe: 2.0%, C: 0.05% metal, electrolytic iron with a purity of 89.5%, B: 19.8%, F
Nd, Pr: 34.13% using ferroporon of e-nia 5.0%, C: 0.08%, Al: 4.0% as raw materials
, Fe: 63.8%, B: 8.0%, A-cross 0.3
% and melted in a high frequency melting furnace to create an ingot.The carbon content of this ingot was analyzed and was found to be 0.02%.After coarsely crushing it with a disk mill, N2 The average particle size is 3 with a jet mill using gas.
．． It was pulverized to 5 lm. This was oriented in a magnetic field of 1 OKOe, press-molded at a pressure of it/crn', and then the molded product was sintered at 1050° C. for 1 hour.

The sintered product was heat treated at 550° C. for 1 hour and then rapidly cooled using an inert gas.

For comparison, N d : 9.5% instead of the above metal.
, P r : 3.0%, Fe: 1.5%, C: O,
A sintered magnet was produced in the same manner as described above, except that 7% metal was used. The carbon content analysis result of this ingot was 0.28%. Figure 1 shows the rate of weight increase over time when finely pulverized powder of each magnet material is left in the air, and Table 1 shows the rate of weight increase over time when the finely ground powder of each magnet material is left in the air for a certain period of time and is sintered and heat treated. It shows the change in magnetic density and magnetic properties obtained using a magnet.

Table 1 The Qi of the sintered body prepared using the 24H fine powder after standing in Table 1 was 0.2%.

From the results shown in Figure 1, the weight of the fine powder with a low carbon content hardly increases after a certain period of time, whereas the weight of the fine powder with a high carbon content in the comparative example increases rapidly at the beginning.
Even after that, no tendency to saturation was observed, which indicates that the oxidation behavior changes significantly depending on the carbon content.

Furthermore, from the results in Table 1, it can be seen that the composition with a lower carbon content causes less deterioration of the fine powder and less influence on the magnetic properties.

Example 2 Nd: 94-97%, Pr: 1-3.5%, F
e: 1-4%, C: 0.02-0.9% (7) N d
Metal, electrolytic iron and cobalt with purity of 99.9%, B metal with Bi: 99.5%, C: 0.2% as raw materials, Nd-Pr: 37.3%, Fe: 4
B, 7%, Co: 12.95%, B: 1.1%
Weighed five types of materials with different compositions only in carbon content, prepared fine powders for each in the same manner as in Example 1, left them in the atmosphere for 24 hours, and then produced anisotropic sintered magnets under the same conditions as in Example 1. were created and their magnetic properties were measured.

Figure 2 shows the relationship between carbon content and iHc.It shows that when the carbon content exceeds 0.05%, the coercive force decreases rapidly. This indicates that it is easily susceptible to oxidation and moisture absorption deterioration.

Example 3 Nd: 99.9%, c: o, ot% metal, and D
Y: 99.9%, C: 0.01% metal, purity 8
9.9% electrolytic iron and B: 99.5%, C: 0.2%
Using metal as raw material, N d : 29.4%, D
Y: 3.7%, Fe: 65.8%, B:
It was weighed so that the composition was 1.1%, and an ingot was prepared in the same manner as in Example 1. The analysis result of the carbon content was 0.01% or less. This ingot was coarsely crushed with a disk mill while flowing with N2 gas, and further finely crushed with a jet mill to a uniform particle size of 3 pm. After orienting this fine powder in a magnetic field of 10 KOe, it was crushed under a pressure of 1 t/crn. After press forming, sintering and heat treatment were carried out under the same conditions as in Example 1. During each period from pulverization to sintering, the powder or compact was stored in a chamber filled with inert gas and oxidized by oxygen in the air. was suppressed as much as possible.

When the magnetic properties and oxygen content of this sintered body were measured, the following results were obtained.

B r = 12.4 K G, i Hc = 20.8 KOe (BH)wax = 36 MG * 0e O = 0.15% C = 0.008% In addition, those manufactured by a normal method have B r = 12. 0K G, i Hc = 17.4KOe (BH)wax = 32MGsOe O = 0°75% c = o, o7% (Effects of the invention) As described above, the permanent magnet material according to the present invention reduces the amount of powder during the manufacturing process. Since there is little deterioration, a dense sintered body can be obtained and high magnetic properties can be maintained.

[Brief explanation of drawings]

FIG. 1 is a graph showing the weight increase rate over time when fine powders with different carbon contents are left in the atmosphere, and FIG. 2 is a graph showing the relationship between carbon content in a magnet and coercive force. Patent Applicant: Shin-Etsu Chemical Co., Ltd. Agent/Patent Attorney Ryo Yamamoto - Figure 1 Chichi 1 o'clock south (h') Figure 2 A) Ding - C Lid (w?%)

Claims (1)

[Claims] 25 to 40% R by weight percentage (R is at least one of Y and a rare earth element), 0.7 to 2.5% B, 0.05% or less C, and less than 0.3% O and the remainder M (where M is Fe in Fe, Co, AlNb, and Si)
A rare earth permanent magnet material comprising: