JPH024942A - Permanent magnetic alloy - Google Patents

Abstract

PURPOSE:To obtain the title alloy having high coercive force and energy product value by incorporating specific amounts of Ga and O2 into a permanent magnetic alloy constituted of an Fe-rare earth-B alloy. CONSTITUTION:At the time of manufacturing an Fe-rare earth-B magnetic alloy, by weight, <13% Ga (where <=90% Ga can be substituted by Al) and 0.005 to 0.03% O2 are incorporated into an alloy having the compsn. contg. Y and at least one kind among rare earth elements, particularly 10 to 40% Nd, 1 to 8% B and the balance Fe and contg., at need, <=30% Co. After that, the molten metal of the alloy is cooled in an Ar gas atmosphere, is soldified and is thereafter finely pulverized. The fine powder is subjected to press forming in a magnetic field, is thereafter sintered in an oxidizing atmosphere, is rapidly cooled, is furthermore subjected to aging treatment in vacuum and is thereafter rapidly cooled to the room temp. The permanent magnetic alloy having improved coercive force by the addition of Ga, in which the fine pulverization of the material alloy can be facilitated by the addition of O2, and having excellent energy product value by the equalization of the grain size can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention (Industrial Field of Application) The present invention relates to a permanent magnet alloy, and is particularly used for producing rare earth iron permanent magnets.

(Prior art) As a conventionally known rare earth magnet, RCo
Type, R (Co, Cu, Fe, M) 17
type (where R is a rare earth element such as Sm or Ce, M is Ti
, transition elements such as Zr, Hf, etc.) are known. However, this type of permanent magnet has the problem that the maximum energy product is about 30 M G Oe and that a large amount of relatively expensive Co must be used.

In recent years, instead of the above-mentioned rare earth cobalt-based permanent magnets, relatively inexpensive rare-earth iron-based permanent magnets have been studied (Japanese Unexamined Patent Publication No. 1983-1999).
No. 46008, JP-A-59-647333, etc.).

This is made of constituent elements such as Nd-Fe-B, and is a very effective material because it not only reduces cost by using Fe, but also provides a maximum energy product exceeding 30 MGOe.

However, this rare earth iron-based permanent magnet exhibits large variations in magnetic properties, particularly coercive force, ranging from 3000e to over 10 kOe depending on manufacturing conditions, and has the problem that stable magnetic properties cannot be obtained. This is a very important problem industrially, and if rare earth iron permanent magnets with stable magnetic properties with good reproducibility can be obtained, their practicality will be greatly improved.

In addition, the requirements for high coercive force and high (BH) are strong Research is progressing toward higher performance.

(Problems to be Solved by the Invention) The present invention has been made in consideration of the above points, and provides a permanent magnet having good l1aX magnetic properties such as high coercive force and high (BH) with good reproducibility. The purpose is to provide a permanent magnet alloy that can

[Structure of the Invention (Means and Effects for Solving the Problems) The inventors of the present invention have conducted extensive research to solve the above problems, and have found that rare earth iron permanent magnets do not require the addition of Ga or the weight of oxygen. found that magnetic properties, especially coercive force, have a significant effect.

The present invention was made based on this, and 10-
40% by weight of R (R is at least one selected from Y and rare earth elements), 0.1 to 8% by weight of boron, 1
Gallium up to 3% by weight, 0.005-0.03% by weight
It is a permanent magnetic alloy characterized by containing oxygen and unavoidable impurities, with the remainder mainly consisting of iron.

In the present invention, the content of each element is limited to the above range for the following reasons.

If R is less than 10% by weight, no increase in iHc can be obtained;
If the weight percentage is exceeded, Br decreases, and therefore (BH) decreases in either case.

max Therefore, the content of R is set to 10 to 40% by weight. Preferably it is 25 to 35% by weight. Note that among the rare earth elements, Nd and Pr are particularly effective elements for obtaining a high (BH)max, and it is preferable that R contains at least one of these two elements as an essential element. The proportion of Nd and Pr in Rffi is 70% or more (R
ffi) is desirable. Especially Nd
It is preferable that R accounts for 90% by weight or more of the entire R.

When boron (B) is less than 0.1%, iHc decreases and 8
When the weight percentage is exceeded, the Br decreases significantly.

Therefore, the boron content is set to 0.1 to 8% by weight.

In order to obtain a high coercive force, the content is preferably 1.2% by weight or more. In addition, a part of B is C, N, Si, P.

It may be replaced with Ge or the like. This makes it possible to improve the sinterability and, in turn, to increase Br and (BH). In this case, it is desirable that the amount of substitution is up to about 80% of B.

Gallium (Ga) is an element effective in improving coercive force (iHc). Although it is effective when added in small amounts, the iHc increases significantly when it is 0.1% by weight or more, preferably 0.2% by weight or more. If it exceeds 13% by weight, the Br decreases significantly. Therefore, the content of gallium is set to 13% by weight or less.

It is possible to replace up to 90 layers of Ga with AA.

The amount of oxygen is important when manufacturing a permanent magnet using a permanent magnet alloy with a predetermined composition. If the oxygen content is less than 0.005% by weight, it will be difficult to produce pulverized powder of about 2 to 10 μm, which is required in the production of permanent magnets. As a result, the grain size becomes non-uniform, resulting in poor orientation during molding in a magnetic field, resulting in a decrease in Br and, in turn, a decrease in (BH) ax . Furthermore, manufacturing costs also increase significantly.

On the other hand, if it exceeds 0.03% by weight, the coercive force decreases and high (
BH) cannot be obtained. Therefore, the oxygen content in the permanent magnet alloy is preferably 0.005 to 0.03% by weight. The amount may increase slightly in the permanent magnet after sintering.

Although the function of oxygen in a permanent magnet alloy is not clear, it is presumed that a high-performance permanent magnet can be obtained by the following behavior.

That is, it is considered that a part of the oxygen in the molten alloy combines with R and Fe atoms, which are the main component elements, to form an oxide, and exists segregated at alloy grain boundaries and the like along with the remaining oxygen. Considering that R-Fe-B magnets are fine particle magnets and their coercive force is mainly determined by the magnetic field that generates reversed magnetic domains, if there are many defects such as oxides and segregation, these may act as sources of reversed magnetic domains. It is thought that this causes the coercive force to decrease. Furthermore, if there are few defects, grain boundary fracture etc. will be less likely to occur, so it is expected that the crushability will deteriorate.

The amount of oxygen in the permanent magnet alloy can be controlled by using high-purity raw materials and by strictly adjusting the amount of oxygen in the furnace during melting of the raw material alloy.

The balance other than the above-mentioned elements constituting the alloy of the present invention is mainly iron, and some of the Fe is Co.

AJ7. Cr, Ti, Zr, Hf, Nb, Ta, V.

Mn-, MoXWsRu-, Rh%
It can also be replaced with Re −, P d % OS % 1r, etc. The amount is up to about 30% by weight, and if it is too large, it will cause deterioration of properties such as a decrease in ax of (BH). In particular, Co is effective in raising the Curie temperature, and in a permanent magnet, it is preferably set at 1 to 30 times 2%, or preferably 10 to 20 times 2%. It goes without saying that other inevitable impurities are also included.

Permanent magnets can be manufactured by various methods using the alloy of the present invention. For example, a method in which a permanent magnet having the composition of the present invention is obtained by casting and then heat treated, and a method in which pulverized powder is bonded with a binder to form a bonded magnet.

Examples include a method of sintering pulverized powder into a sintered magnet.

Particularly good results are obtained when a permanent magnet alloy with an oxygen content of 0.005 to 0.03% by weight is used. The case where the sintering method is used will be explained below.

First, a permanent magnet alloy containing predetermined amounts of Fe, R5Ga, and B is manufactured. Next, the permanent magnet alloy is crushed using a crushing means such as a ball mill. At this time, in order to facilitate molding and sintering in the subsequent steps and to improve magnetic properties, it is desirable to pulverize the powder so that the average particle size is 2 to 10 μm.

If the particle size exceeds 10 μm, the iHc decreases, and on the other hand, it is difficult to grind the particles to less than 2 μm.
This causes deterioration of magnetic properties such as Br.

Next, the finely pulverized permanent magnet alloy powder is press-molded into a desired shape. At the time of molding, a magnetic field of, for example, about 15 k Oe is applied to perform orientation treatment in the same way as when manufacturing a normal sintered magnet. Next, for example, 1000 to 1
The molded body is sintered at 140° C. for about 0.5 to 5 hours. This sintering is desirably carried out in an inert gas atmosphere such as Ar gas or in a vacuum so as not to increase the oxygen concentration in the alloy.

The sintered body thus obtained is heated to 550 to 750°C as necessary.
Aging treatment is performed at a temperature range of 0.1 to 10 hours.

When the aging treatment temperature is less than 550°C or more than 750°C,
This leads to a decrease in iHc or deterioration of squareness, and the magnetic properties are
1]. Therefore, the aging treatment temperature is 550 to 75
A range of 0°C is preferred.

According to the above method, B r, i He.

Permanent magnets such as (BH) with excellent magnetic properties can be manufactured with good reproducibility without causing variations in the ax properties.

(Example) The present invention will be explained in detail below.

Example 1 Raw materials were mixed with a predetermined composition and arc melted using a water-cooled copper boat in an Ar atmosphere. The obtained magnetic alloy (oxygen concentration: 0.02 wt%) was coarsely ground in an Ar atmosphere, and further finely ground to a particle size of about 3.0 μm using a jet mill.

This fine powder was filled into a predetermined mold and compression molded at a pressure of 2 ton/c- while applying a magnetic field of 201 c Oe. This molded body was heated to 1 at 1020 to 1120 in an Ar atmosphere.
h After sintering and quenching to room temperature, the temperature is 550-75 in vacuum.
Aging treatment was performed at 0° C. for 3 to 10 hours, and then rapidly cooled to room temperature.

The results are shown in Table 1.

Table 1 Example 2 Each element was mixed so that the composition was 30.8% by weight of neodymium, 0.86% by weight of boron, 1.0% by weight of gallium, and the balance was iron, and 2 kg was placed in an argon atmosphere. , arc melted in a water-cooled copper boat. At that time, the amount of oxygen in the prepared alloy was increased or decreased by strictly controlling the amount of oxygen in the furnace.

The obtained permanent magnet alloy was coarsely ground in an Ar atmosphere, and further finely ground to a particle size of 3 to 5 μm using a stainless steel ball mill.

This finely pulverized material was filled into a predetermined pressing die and compression molded at a pressure of 2 tons/c♂ while applying a grain boundary of 200,000 e.The obtained molded body was sintered at 1,080°C for 1 hour in an argon atmosphere. , and quenched to room temperature. Then in vacuum, 6
Aging treatment was performed at 00°C for 1 hour, and then rapidly cooled to room temperature.

Regarding the obtained permanent magnet, the oxygen concentration in the permanent magnet alloy, the time required to pulverize coarse powder to a particle size of 3 to 5 μm, residual magnetic flux density (Br), coercive force (iHc), and maximum energy product ( The relationship with (BH) )ax is shown in FIG.

As is clear from FIG. 1, the grindability of the alloy and the magnetic properties of the permanent magnet are largely dependent on the oxygen concentration in the alloy.

That is, if the oxygen concentration is less than 0.005% by weight, the crushability becomes extremely poor, and as a result, the orientation during molding in a magnetic field also becomes poor, resulting in a decrease in Br. On the other hand, the oxygen concentration is 0.
If it exceeds 0.3% by weight, the coercive force is extremely reduced.

Example 3 By the same method as in Example 2, a composition of neodymium 31.
A permanent magnet alloy having a composition of 0% by weight, 0.84% by weight of boron, 14.6% by weight of cobalt, 1.1% by weight of gallium, 0.03% by weight of oxygen, and the balance iron was obtained.

The obtained permanent magnet alloy was pulverized, compression molded, and sintered in the same manner as in Example 1.

After the sintered samples were aged for 1 hour at each temperature of 300 to 900°C, they were bathed in a quick bath and the coercive force was examined.

The results are shown in FIG.

As is clear from FIG. 3, the aging temperature greatly affects the coercive force, and it can be seen that the best characteristics are obtained at 550 to 750°C.

Rare earth iron permanent magnets have a tetragonal ferromagnetic Fe-rich phase of NdFe14B as the main phase, and other NdF
It is known to contain a cubic non-magnetic R-rich phase containing 80% by weight or more of an R component such as e1Nd95Fe5, a tetragonal non-magnetic B-rich phase such as Nd2Fe7B6, and further oxides. The gallium of the present invention appears to be present in a concentrated manner in the R-rich phase.

[Effects of the Invention] As detailed above, according to the present invention, high coercive force (BH)
It is possible to stably obtain a rare earth iron-based permanent magnet having aX, which is of extremely great industrial value.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram showing the relationship between oxygen concentration, grinding time, residual magnetic flux density, coercive force, and maximum energy product in the permanent magnet of Example 1 of the present invention, and Figure 2 is Example 2 of the present invention.
FIG. 2 is a characteristic diagram showing the relationship between aging temperature and coercive force in a permanent magnet.

Claims (4)

[Claims] (1) 10-40% by weight of R (R is at least one selected from Y and rare earth elements), 0.1-8% by weight boron, 13% by weight or less gallium, 0.005-0
．． 1. A permanent magnetic alloy characterized in that it contains 0.3% by weight of oxygen and unavoidable impurities, with the remainder mainly consisting of iron. (2) The permanent magnet alloy according to claim 1, which contains 30% by weight or less of Co. (3) The permanent magnet alloy according to claim 1, wherein 90% by weight or less of Ga is replaced with Al. (4) The permanent magnet alloy according to claim 1, wherein 90% by weight or more of R is Nd.