JPS6169945A - Permanent magnet alloy - Google Patents

Abstract

PURPOSE:To obtain an inexpensive permanent magnet alloy which has stable and high coercive force, (BH)max, as well as high productivity by providing a specific composition consisting of Y or rare earth elements, B, O and Fe. CONSTITUTION:A permanent magnet alloy consists of, by weight, 10-40% R (where R is at least one of Y and rare earth elements), 0.1-8% B, 0.005-0.03% O and the balance Fe, which has stable and excellent magnetic characteristics with superior reproducibility. In regard to the above R, Nd and Pr especially have the effect of giving a high (BH)max, so the use of at least one of the two is preferred. And further, the above alloy can be obtd. by use of inexpensive Fe instead of expensive Co.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to permanent magnets, and particularly to rare earth iron-based permanent magnet alloys such as Nd-Fe-B.

[Technical background of the invention and its problems]

As a conventionally known rare earth magnet.

RCo s type %R2 (CoCuFeM) 17i (where R is am, rare earth metal such as Ce, M is Ti, Zr
There are rare earth cobalt-based permanent magnets such as transition gold (R) such as , Hf, etc. However, this type of permanent magnet has the problem that the energy product is limited to about 3QM GOe, and a large amount of relatively expensive Co must be used.

In recent years, instead of this Co-based permanent magnet, relatively inexpensive fkFe-based permanent magnets have been studied (Japanese Unexamined Patent Publication No. 59-46008, etc.)Q
It is a very effective material because it can yield more than 30 MGOe.

However, depending on the manufacturing conditions, these rare earth iron-based permanent magnets exhibit large variations in magnetic properties, especially coercive force, ranging from 3000e to over 10KOe, making it difficult to obtain stable magnetic properties. There is a problem. This is a very big problem in industry), and if an iron-based permanent magnet with good reproducibility and stable magnetic properties can be obtained, the practicality of this R-Fe-B-based permanent magnet will be greatly improved. ◇CObjective of the Invention The present invention has been made in consideration of the above points.

Excellent manufacturability, potash stability, high coercive force, (BH) max
The purpose of the present invention is to provide a permanent magnet alloy having the following characteristics.

[Summary of the invention]

As a result of intensive research aimed at solving the above-mentioned problems, the present inventors discovered the fact that in rare earth Fe-based permanent magnets, the oxygen concentration in the permanent magnet alloy has a significant influence on the coercive force characteristics. The present invention was made based on this discovery, and 10 to 4
0% by weight of R (where R is at least one selected from Y and rare earth elements), 0.1 to 8% boron, o,
It is a permanent magnetic alloy characterized by consisting of oos~0.03% by weight of oxygen and the balance iron.

If R is less than 10% by weight, no increase in rH8 will be obtained, and if the cutting current exceeds 1%, B will decrease and (H)max
will decrease. Therefore, R should be 10 to 40% by weight. Also, among the rare earth elements, Nd and Pr are particularly high (
BH)max, and preferably contains at least one of two elements as R.

It is preferable that the proportion of Nd and Pr in R and i is 70 or more (or the entire R amount may be sufficient).

Further, when boron CB) is 0.1% by weight, the IHC decreases, and when it exceeds 8% by weight, the decrease in B is significant.Therefore, it is set as 01 to 8% by weight.

Note that it is also possible to replace a part of B with C, N, 8i, P, Ge, or the like. Improvement of sinterability due to breakage and B
r, (BH)max can be increased.

In this case, the amount of substitution is up to about 80% of B.

The most important point in the present invention is the oxygen content. If the amount of oxygen exceeds 0.03% by weight, the strength of the coercive magnet will deteriorate, and if high (BH) max can be obtained, fine grinding of about 2 to 10 μm is required for smooth grinding, but the amount of oxygen If there is little, it is difficult to pulverize, and the particle size becomes uneven.
The amount of oxygen that causes a decrease in B due to the decrease in orientation during molding in a magnetic field, and thus a decrease in (BH) max, is o, o
os ~ 0.03% by weight.

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

In other words, it is thought that some of the oxygen in the molten alloy combines with the main component elements R and Fe atoms to form oxides, and exists segregated at alloy grain boundaries with the remaining oxygen. Considering that R-Fe-B magnets are fine-grain magnets and their coercive force is determined mainly by the magnetic field that generates reverse magnetic domains, if there are many defects such as oxides and segregation, these may cause reverse magnetic domains. It is thought that coercivity decreases by acting as a generation source. 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 present invention uses R-Fe-B-0 as a basic component, but a part of Fe is replaced by Co, Cr, All, Tj, Zr, Hf.
, Nb, Ta, V, Mn, Mo, W.

Substitution with Ru, Rh, Pd, Re, Os, Ir, etc. is also possible.

This amount is about 20 yen of Fe, and if it is too much (BH)
This becomes a factor in deterioration of characteristics such as a decrease in max. Especially Co, R
u, Rh.

Pd, Re, Os, and Ir are effective in increasing the core temperature and contribute to improving the temperature stability of magnetic properties, and Cr, A
I greatly improves corrosion resistance.

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

A permanent magnet having good magnetic properties can be obtained using the permanent magnet alloy according to the present invention. The method is shown below.

First, a permanent magnet alloy having the composition as described above is manufactured. Next, the permanent magnet alloy is crushed using a crushing means such as a ball mill (first step).

At this time, in order to facilitate post-processing and sintering and to improve magnetic properties, the average particle size of the powder obtained is 2 to 10
It is preferable to set it to about μm. If the particle size exceeds 10 μm, the magnetic flux density will be reduced, and it is difficult to grind the particles to 2 μm or less, and this will lead to a decrease in magnetic properties such as coercive force.

Next, the powder obtained in the first step is molded into a desired shape. During molding, 1.
For example, about 15 KOe is applied to perform the alignment process. Then 1000'C! ~1200'(:!, 0.5~5
The molded body is sintered under conditions of approximately 100 ms (second step 8).

This sintering is performed so as not to increase the oxygen content in the alloy.
It is preferable to carry out in an inert gas atmosphere such as r gas.

Furthermore, to improve magnetic properties, sintered body K400~110
0° C. 11 ~] Aging treatment at a temperature of 0 hours may be performed.

The permanent magnet manufactured in this way has excellent properties of permanent magnet alloy, so Br, Hc, (BH)max
It is possible to obtain a permanent magnet with excellent magnetic properties such as.

〔Effect of the invention〕

As explained above, according to one aspect of the present invention, THo.

(BH) Permanent magnets with excellent magnetic properties such as rrlax,
It can be manufactured with good reproducibility and has excellent manufacturability. Therefore, since it is possible to obtain an inexpensive Fe-based magnet with good characteristics, it is of great industrial value.

[Embodiments of the invention]

The present invention will be explained in detail below.

(Example 1) Each metal element was mixed so that the composition was neodymium by weight, boro by weight by 71.3, and iron by weight, and the balance was iron, and 2 kg was arc melted in a water-cooled copper boat in an argon atmosphere. that time,
By strictly controlling the oxygen layer in the furnace, the amount of oxygen in the furnace was increased or decreased.

The obtained permanent magnet alloy was coarsely ground in an Arg atmosphere, and finely ground to a particle size of 3 to 5 μm using a stainless steel ball mill.The fine powder was then filled into a predetermined press mold, and a 2 ton press was applied while applying a magnetic field of 20,000 Oersted. Compression molding was performed at a pressure of /cnt. The obtained molded body was heated in an argon atmosphere for 1
080' was sintered for 0.1 hour and rapidly cooled to room temperature.

Thereafter, aging was performed at 550'0XIH in vacuum, and the product was rapidly cooled to room temperature.

The residual magnetic flux density (B'), coercive force, and bulk energy product ((BH)max)' of the obtained permanent magnet were measured, and the results are shown in Figure 1.At the same time, coarse powder with each oxygen content was measured. 3~
The time required to mill to a particle size of 5 μm is also shown.

From Figure 1, the crushability and coercive force of the alloy, and (BH)m
It can be seen that ax greatly depends on the oxygen concentration, and when it is less than 0.005%, the crushability is extremely deteriorated, and when it exceeds 0.03%, the coercive force is extremely reduced.

(Example 2) Permanent magnets were produced in the same manner as in Example 1 using alloys having the respective compositions shown in Table 1, except for the sintering temperature. The magnetic properties are also listed in Table 1.

As is clear from the above results, the rare earth iron-based permanent magnet alloy according to the present invention has the remarkable advantages of excellent crushability and therefore manufacturability, as well as very large coercive force and energy product.

Below margin

[Brief explanation of drawings]

Figure 1 is a characteristic curve diagram showing magnetic properties and grinding time. Agent Patent attorney Noriyuki Chika (and 1 other person) Figure 1 0 111) f D, lj2
1”ρ? 6.54 θ−ρS
Tochiko (tt%) -

Claims (2)

[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
A permanent magnetic alloy comprising: boron, 0.005 to 0.03% by weight of oxygen, and the balance iron. (2) The permanent magnet alloy according to claim 1, wherein the R contains at least one selected from Nd and Pr.