JPS6318603A - Permanent magnet - Google Patents

Abstract

PURPOSE:To obtain a magnet particularly having good temperature characteristics by sintering an alloy composed mainly of Fe and containing a rare earth element R containing Y, Co, B and Ga, thereby producing a permanent magnet which is composed mainly of a ferromagnetic Fe-rich phase of the tetragonal system and containing a non-magnetic Laves phase. CONSTITUTION:A given amount of Ga is added to a composition of the R-B-Co- Fe system to develop a non-magnetic Laves phase. Its wt.% composition is such that R is 10-40%, B is 0.1-8%, Co is 1-30%, Ga is 0.1-1%, and the remainder is substantially Fe. This alloy is ground to an average particle diameter of 2-10mum, oriented by applying a magnetic field when pressing, subsequently sintered in Ar of about 1100 deg.C, and then aged. If the proportion of the Laves phase is 2-10vol.%, B is 0.8-0.95wt.% and 90wt.% or less of Ga is substituted by Al, then a permanent magnet is obtained which has a higher Curie temperature an paticularly has good temperature characteristics.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to permanent magnets.

(Prior Art) Rare earth Co-based magnets have been known as high-performance magnets. This rare earth Co-based magnet has a maximum energy product of about 30 MGOe at most, and in recent years there has been a strong demand for smaller size and higher performance in various electronic devices, and there has been a desire to develop permanent magnets with higher performance. In response to these demands, permanent magnets mainly made of iron are being developed (Japanese Patent Laid-Open No. 59
-46008 etc.). This iron-based permanent magnet contains rare earth elements such as Nd and boron, and the remainder is substantially iron (B
H) It is possible to obtain a material with a max of over 30 MGOe, and since it is mainly made of Fe, which is cheaper than Co,
It is a very promising material that can produce high-performance magnets at low cost.

The problem with this iron-based permanent magnet is that it has a lower benzyl temperature than rare-earth cobalt-based permanent magnets, and its magnetic properties have inferior temperature characteristics. This is a major problem when used in DC brushless motors, etc., which are used under harsh conditions such as high-temperature environments, and improvements in this respect are desired.

As such an improvement, for example, R-B-Co-AI-Fe
The composition of
. However, there is a strong demand for higher performance rare earth iron permanent magnets, and development efforts are underway in various places.

(Problems to be Solved by the Invention) As described above, rare earth iron-based permanent magnets can be extremely high-performance magnets, but they have the disadvantage of having a low Curie temperature and poor temperature characteristics of magnetic properties.

The present invention has been made in consideration of the above points, and an object of the present invention is to obtain a permanent magnet having a high Curie temperature and good magnetic properties, particularly temperature properties.

[Structure of the Invention (Means and Actions for Solving Problems) The present invention is a sintered body of an alloy whose main component is iron and which contains R (a rare earth element including yttrium), cobalt, boron, and Ga. It is a permanent magnet characterized by being mainly composed of a tetragonal ferromagnetic F, S,...T phase and containing a nonmagnetic Rashis phase.

Rare earth iron-based permanent magnets mainly have a tetragonal ferromagnetic Fe-rich phase of Nd2Fe14B9. These phases are considered constituent phases, and further include oxides and the like. The same holds true when other R components are used.

The present invention also has the disadvantage that the non-magnetic Laves phase as a constituent phase reduces coercive force. This is because a Laves phase, which is a magnetic phase, is generated. This magnetic phase, the Laves phase, is thought to serve as a nucleation site for reversed magnetic domains and reduce the coercive force. In the present invention, this Laves phase is made non-magnetic,
This improves coercive force. Therefore, it is possible to make the best use of the effect of increasing the Curie temperature due to the addition of Co and to improve the magnetic properties. In addition, the characteristics are also improved in this way. This non-magnetic Laves phase is 2 to 10 vol%
It is preferable to contain it to some extent. If it is too large, the ratio of the main phase responsible for magnetism decreases, resulting in a decrease in Br. On the other hand, if the amount is too small, the amount of Co added will be too small and the effect of raising the Curie temperature will not be sufficiently obtained.

Other R-rich phases, B-rich phases, etc. are not essential.

However, the R-rich phase has a lower melting point than the main phase, and during sintering, removes defects, foreign matter, etc. from the interface of the main phase, reduces the number of sites where reversed magnetic domains occur, and contributes to improving coercive force. However, if the amount is too large, the ratio of the main phase will decrease and the magnetic properties will deteriorate.
It is better to contain about vol%.

As mentioned above, in order to make a nonmagnetic Laves phase appear, for example, a specific amount of G is added to a specific R-B-Co-Pe system composition.
This can be achieved by adding and containing a. This - example 1
As shown in the figure. FIG. 1(a) is an X-ray diffraction diagram when no Co is added, FIG. 1(b) is an X-ray diffraction diagram when only CO is added, and FIG. 1(C) is an X-ray diffraction diagram when Ga is further added. In both cases, the main phase is Fe.
It is a rich phase. However, in the case of Co addition, there are peaks indicating the presence of a different phase near the diffraction angle 2θ of 34° and 40°.

This P M g Cu 2 types of N d (F e,
Co), (22
0) and (311) peaks. Fe, C in this Laves phase.

Considering that the ratio of is about 1=1, the Curie temperature is around 100°C, and it has magnetism at room temperature.

Considering that the coercive force of rare earth iron permanent magnets is determined by the magnitude of the magnetic field that generates reverse magnetic domains, it is clear that this magnetic Laves phase acts as a site where reverse magnetic domains occur.

On the other hand, in the present invention, as is clear from FIG. 1(C), there is a peak at 2θ of 34° and 40';
It can be seen that the angle is slightly tilted to the lower angle side compared to the case of . This is Nd(Fe.

Co) This shows that the lattice constant of the two phases is elongated. The atomic radius of Ga atom is 1.41 A and Fe(1,
28A) is larger than Co (1,25A), indicating that Ga atoms are present in the Laves phase.

Since Ga atoms are non-magnetic, Nd(Fe.

Cor Ga ) 2 becomes a non-magnetic phase, and this non-magnetic Laves phase does not become a nucleation site for reverse magnetic domains, resulting in an improvement in coercive force.

The composition of the permanent magnet of the present invention is: R ÷ 70. It goes without saying that even within this composition range, if it does not contain a non-magnetic Laves phase, it is not within the scope of the present invention.

When the R component is less than 10% by weight, the coercive force is small, and when it exceeds 40%, Br decreases and (BH)wax decreases. More preferably 25 to 35% by weight. Furthermore, among the rare earth elements, Nd and Pr are effective in obtaining high (BH) wax, and it is preferable to contain at least one of these two elements, particularly Nd, as the R component. These two elements R
The proportion in the components is preferably 70% by weight or more.

If B is less than 0.1 weight 96, iHc will decrease,
When it exceeds 8 m2%, Br decreases. It's 20B. Bf
As fl increases, the non-magnetic B-rich phase increases.It is also possible to improve sinterability, etc., but the substitution amount is 80% by weight of the B amount.
To some extent.

Co contributes to raising the Curie temperature and is effective in improving the temperature characteristics of magnetic properties, and addition of 1 to 30% by weight is effective. A certain amount of addition is necessary to sufficiently obtain the effect of raising the Curie temperature, but when magnetic properties are taken into account, if the amount exceeds 30% by weight, the coercive force and (BH)IIlax will decrease. It is preferable to add a large amount so as not to deteriorate the magnetic properties, and preferably 5% by weight or more, more preferably 13% by weight or more,
13-23 weight 96 is preferred.

Further, in order to obtain a nonmagnetic Laves phase, for example, Ga is added as described above. Ga lowers the Curie temperature of the Laves phase, becomes nonmagnetic at room temperature, and has a coercive force. Part of Ga is L
It may be substituted with 2, but the total amount of 2 is 10% by weight or less.

Further, the amount of substitution must be less than 90 times Ga.

When this Ga is contained in the Fe-rich phase, the coercive force is specifically increased, and the magnetic properties such as (BH)max and temperature properties are improved. Although the detailed mechanism is not clear, Ga
This is considered to be because the grain boundaries of the Fe-rich phase are purified by the mixing of the Fe-rich phase. Further, even if the permanent magnet as a whole contains the same amount of Ga, it is not very effective if a large amount of Ga is contained in phases other than the Fe-rich phase, that is, the B-rich phase, the R-rich phase, etc. At least 70% of Ga, and even 8
It is preferable that 0% or more of Fe is contained in the Fe-rich phase.

The oxygen concentration in this permanent magnet alloy is important. If the amount of oxygen is large, the coercive force will decrease, resulting in high (BH)Il
cannot obtain lax. In addition, if the amount is too small, it becomes difficult to crush the raw material alloy, resulting in a significant increase in manufacturing costs. Although pulverization is required to be finely pulverized to about 2 to 10 μm, if the amount of oxygen is small, pulverization is difficult and the particle size becomes non-uniform, resulting in a decrease in (BH)IIlax. Therefore, the amount of oxygen is preferably 0.005 to 0.603% by weight.

Although the function of oxygen in the alloy is not clear, it is thought that a high-performance permanent magnet can be obtained by the following behavior. That is, some of the oxygen in the melted alloy combines with R and Fe atoms, which are the main constituent elements, to form an oxide,
It is thought that it exists segregated at the grain boundaries together with the remaining oxygen, and is particularly absorbed by the R-rich phase, impeding magnetic properties. Considering that rare earth iron permanent magnets are fine particle magnets and their coercive force is determined by the magnetic field that generates reversed magnetic domains, if there are many defects such as oxides and segregation, these will act as sources of reversed magnetic domains. It is thought that the coercive force decreases. It is also believed that defects reduce the quality. The oxygen port 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 etc. during melting of the raw material alloy.

The permanent magnet of the present invention is manufactured as follows.

First, a raw material alloy having a predetermined composition is pulverized using a pulverizing 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 preferable to pulverize the powder so that the average particle size is 2 to 10 t1m. If it is too large, the coercive force will be lowered, and if it is too small, it will be difficult to crush, leading to a reduction in the magnetic properties of Br, etc.

Next, the finely pulverized permanent magnet alloy powder is press-molded into a desired shape. During molding, a magnetic field of about 10 kOe is applied, for example, in the same way as in manufacturing normal sintered magnets.
Perform orientation processing. Then 1000-1200°C, 0
, 5 to 5 hours.

This sintering is performed so as not to increase the oxygen concentration in the alloy.
It is preferable to carry out the reaction in an inert gas such as r gas or in a vacuum. Subsequently, aging treatment is performed under conditions of 500 to 1000°C and approximately 0.5 to 10 hours.

In this way, the permanent magnet of the present invention is obtained.

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

・Example-1 Around 0.7 1-1, 4 vt%B, 2.1wt%Ga
, 14.4wt%Co.

Each element was blended to have a composition of 32.4 vt% Nd and balance Fe, and arc melted in a water-cooled copper boat in an Ar atmosphere. The obtained magnetic alloy (oxygen concentration 0.02 wt%) was coarsely pulverized in an Ar atmosphere, and further finely pulverized to a particle size of about \=yμm using a jet mill 3 and a Gl 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 20 kOe. This molded body was heated at 1020 to 1120°C in an Ar atmosphere for 1
After sintering and rapidly cooling to room temperature, 900°C in vacuum for 1 h.
This was followed by an aging treatment at 600° C. for 6 hours, followed by rapid cooling to room temperature. Non-magnetic Laves phase was confirmed in all magnets by X-ray diffraction. Also, 90 of Ga
% or more was contained in the Fe-rich phase by microstructural observation using XMA.

For the obtained permanent magnet, i Hc , (B H)
The relationship between max and the amount of B is shown in FIG. For comparison, B
(b) -1.4wt%, Co 14.4vt%, N
d The composition of 32.4 wt % balance Fe (Comparative Example-1) is also shown in FIG. In this comparative example, a non-magnetic Laves phase was not confirmed, but a magnetic Laves phase was confirmed.

As is clear from Fig. 2, i Hc , (B H)
It can be seen that the max is higher. In addition, in this example, the Curie temperature is 500°C-, the temperature coefficient of Br is -0,
It was excellent at 0.071%/'C.

Table 1 shows the characteristics of magnets of various compositions manufactured in the same manner.

As is clear from Table 1 below, the permanent magnet according to the present invention exhibits excellent characteristics.

・Example-2 Table 2 shows the constituent phases and magnetic properties of magnets with various compositions.

As is clear from Table 2, excellent magnetic properties were obtained in the examples of the present invention containing a non-magnetic Laves phase.

Margin below/Example-3 B 0.9vt%, Ga 1.34wj%, Co
Each element was blended to have a composition of 14.3 wt %, Nd 30.8 vt 96 balance Fe, and arc melted in 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 μm using a jet mill. FIG. 3 shows the relationship between the coercive force value and the number of days from the day of crushing to sintering (stored in Ar) when this powder was manufactured in the same manner as in Example-1. For comparison.

B 0.98wt%, N d 32.7vt% remainder F
e (Comparative Example-2) is also shown in FIG.

As is clear from Figure 3, in the case of Comparative Example-2, the
Although the coercive force significantly decreases after 20 days, no deterioration of the coercive force was observed in the examples of the present invention even after 20 days.

[Effects of the Invention] As explained above, according to the present invention, it is possible to obtain a rare earth iron-based permanent magnet that has a high Curie temperature, excellent magnetic properties, and good temperature characteristics.

[Brief explanation of the drawing]

Figure 1 is an X-ray diffraction diagram of a permanent magnet, Figure 2 is a characteristic diagram showing the relationship between B2 and magnetic properties, and Figure 3 is a characteristic diagram showing the relationship between the number of days until sintering of crushed particles and coercive force. be.

Claims (4)

[Claims] (1) R (rare earth elements including yttrium) 10-40
Weight%, B0.1-8% by weight, Co1-30% by weight, G
It is a sintered body of an alloy consisting of a composition system in which the balance is substantially Fe at 0.1 to 10% by weight, and is mainly composed of a tetragonal ferromagnetic Fe-rich phase and contains a non-magnetic Laves phase. Features a permanent magnet. (2) The permanent magnet according to claim 1, wherein the proportion of the Laves phase is 2 to 10 vol%. (3) The permanent magnet according to claim 1, wherein B is 0.8 to 0.95% by weight. (4) The permanent magnet according to claim 1, wherein 90% by weight or less of Ga is replaced with Al.