JPH04163902A - Permanent magnet - Google Patents

Abstract

PURPOSE:To improve magnetic properties including residual magnetic density as a representative one by sintering and forming a green compact with specific proportions of rare earth metal and the other metals and a specific composition of the rare earth metal and the other metals. CONSTITUTION:By sintering a green compact composed of a certain type of alloy, a permanent magnet with enhanced residual magnetization features can be obtained. This green compact contains rare earth metal (R) and other metals at an atomic ratio of 1:7-9. Further, the rare earth metal (R) consists of Pr or a lanthanoid element that contains Pr at an atomic percentage of 70% or higher. The other metals include Co, Fe, Cu and other transition metals (T) with an atomic percentage of 15-40% Fe, 5-20% Cu, 1-6% T, and the remainder Co. The other transition metals (T) consist of either one or tow of Zr. Ti, and V.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvements in rare earth/cobalt based permanent magnets formed by sintering.

(Prior Art) A typical example of this type of rare earth/cobalt based permanent magnet is a samarium/cobalt magnet.

This samarium-cobalt magnet contains samarium (Sm) and cobalt (CO) as basic components, as well as small amounts of iron (Fe), copper (Cu), and zirconium (
Zr) etc., and Sm2Cot? It consists mainly of a compound phase. The magnetic properties of this samarium-cobalt magnet are usually the maximum energy product B Hmax 2
4MGOe, residual magnetic flux density Br 1O-11KG, coercive force iHc 7-15KOe, and its excellent magnetic properties make it suitable for voice coil motors (VCM) and various motors.
Widely used in speakers.

By the way, in recent years, permanent magnets based on rare earth elements, iron, and boron have been developed, and their use is attracting attention. This rare earth/iron/boron based permanent magnet is a typical neodymium/iron/boron magnet with B Hmax30-40 MGOe, B r
At 12-13 kg, it has higher magnetic properties than the samarium-cobalt magnets mentioned above.

However, these rare earth, iron, and boron based permanent magnets contain a large amount of iron (60 to 75% by weight), which easily rusts in the air, so they not only have poor corrosion resistance, but also require surface coating treatment.
Because the temperature characteristics are inferior to samarium-cobalt magnets (temperature coefficient of samarium-cobalt magnets is -0.03%)
1012%/'C), which limits its use in high temperature ranges.

(Problem to be solved by the invention) Therefore, we take advantage of the excellent corrosion resistance and temperature characteristics of rare earth/cobalt permanent magnets, and further improve the magnetic properties to a level close to that of rare earth/iron/boron permanent magnets. If possible, it would be extremely useful, and studies have been progressing from the manufacturing and composition aspects. However, improvements in the magnet manufacturing process, such as prevention of oxidation during the powdering or sintering process, and alignment and orientation of powder particles during compaction in a magnetic field to impart anisotropy, have already reached a certain level of technology. It is difficult to expect any further improvement, and even if we consider the composition as an extension of today's samarium-cobalt magnets, which have been obtained through long-term technological improvements, improvements in magnetic properties will still take a certain amount. Due to limitations, it has been extremely difficult to obtain magnets with desired performance.

Therefore, an object of the present invention is to achieve further improvement in the magnetic properties of rare earth/cobalt based permanent magnets, thereby expanding the range of application.

(Means for Solving the Problems) In the present invention, a permanent magnet having excellent magnetic properties was realized by the following technical means.

That is, as a result of various investigations into the magnetic properties of R2C017, a compound of rare earth metal (R) and cobalt (Co),
Compound of neodymium (Nd) and praseodymium (Pr) N dzC01? , the saturation magnetization of P r2C017 is 14KG, and S mzC01? It was confirmed that the weight was significantly higher than that of 12KG. Furthermore, as a result of a detailed study on the possibility of permanent magnets, we found that among these compounds, N
Even if part of Co in d2Co+t was replaced with Fe, uniaxial magnetocrystalline anisotropy could not be observed, whereas in P
It has been revealed that when a part of Co in r2C017 is replaced with Fe, it exhibits -axis magnetocrystalline anisotropy and is useful as a magnet material.

The present invention was made by conducting various technical experiments based on the above knowledge, and contains a rare earth metal (R) and other metals in an atomic ratio of 1:7 to 9. metal(
R) consists of Pr or a lanthanide element containing 70 atomic % or more of Pr, and the other metals include Co, Fe, C
u and other transition metals (T) in atomic %, 15 to 4
0% Fe - 5-20% Cu - 1-6% T - balance C.

The other transition metals (T) include Zr, T
It is characterized in that it is made of one or both of i and V, and is made by sintering a green compact.

In the present invention, praseodymium Pr is selected as the rare earth metal (R.) because it is extremely effective in obtaining a residual magnetic flux density based on high saturation magnetization as described above. This is also because Pr has five times the supply as a resource compared to samarium (Sm), and its raw material price is about half that of Sm, which is relatively cheap. In the present invention, in order to improve magnetic properties and reduce costs, in addition to Pr, Ce, La Dy, etc. are used as rare earth metals.
, Gd, Tb, Ho, Sm, and other rare earth metals. However, Pr needs to be 70 atomic % or more in order to obtain good magnetic properties.

Further, the ratio of other metals mainly consisting of Co to the rare earth metal (R) is required to be 1:7 to 9 in order to obtain desired magnetic properties.

That is, when based on the R2C01□ phase, the calculated ratio is 1:8.5, but this compound has a certain solid solubility limit, and therefore, the present invention solves this solid solubility limit. The ratio has a range within the range. Furthermore, like conventional samarium-cobalt magnets, this magnet is internally structured by the coexistence of a small amount of RCo5 compound phase, so the composition is richer in rare earth metals than the calculated ratio.

As mentioned above, Fe is necessary to impart uniaxial magnetocrystalline anisotropy to PrzCo+□, but its effect is small if its proportion in metals other than rare earth metals is less than 15 at%. On the other hand, if the proportion exceeds 40 atom %, the anisotropy of the compound becomes easy and it becomes unsuitable for use as a permanent magnet, so this is set in the range of 15 to 40 atom %.

In addition, in order to obtain coercive force as a magnet, the internal structure is Pr.
It is important to create a two-phase state of zCol□ and PrCo5, and since Cu works extremely effectively to create this two-phase state, Cu is contained in metals other than rare earth metals at 5 to 20 atomic%. I let it happen. However, if the Cu content is less than 5%, the effect is small;
If it exceeds %, the residual magnetic flux density will decrease, so this is set as the above range.

Furthermore, other transition metals (T) include Zr, Ti
It has become clear that the addition of an appropriate amount of V is effective in improving coercive force.
The content was 6 at%.

The permanent magnet of the present invention can be manufactured by a conventionally known method. For example, an alloy ingot of a predetermined composition that has been cast by high-frequency melting is pulverized into a few microns, compression-molded in a magnetic field to form a green compact, and this green compact is sintered and heat-treated to obtain a sintered body. , it can be made into a product by performing final grinding.

(Function) In the permanent magnet configured as above, PrzCO
Due to the presence of +7 compound phase and Fe substitution for CO,
In particular, the residual magnetic flux density Br is significantly improved compared to conventional samarium-cobalt permanent magnets.

(Example) An embodiment of the present invention will be described below.

Example 1 A cast ingot was obtained by high-frequency melting of an alloy having a predetermined composition as shown in Table 1. Each melted raw material is 95% pure Pr
and other rare earth metals with a purity of 99% or more, purity 99
% or more of electrolytic cobalt, electrolytic copper, electrolytic iron, sponge titanium, and ferrozirconium (Fe-Zr).

After coarsely pulverizing the above ingot, a jet mill into which nitrogen gas was introduced was used to obtain fine powder with an average particle size of 5 μm. Next, this powder was filled into a mold and compression molded under a magnetic field of 10 KOe and a pressure of 2 tons/cm2, and then a rectangular parallelepiped sample of 1060~600~b x 8 mm was obtained in an argon gas atmosphere. As a comparative example, a sintered sample made of samarium-cobalt alloy was also produced at the same time.

The magnetic properties are measured using a DC magnetometer (commonly known as BHI-laser) by drawing a hysteresis loop in a 25 KOe magnetic field after pulse magnetization of 60 KOe. The test was carried out in a thickness direction of 8 mm.These results are collectively shown in Table 1.

In addition, in the table below, among the component compositions, metals in parentheses mainly consisting of Co refer to metals other than rare earth metals.
The numbers in parentheses indicate the atomic ratio of the metals in parentheses to rare earth metals, and the numbers in parentheses indicate the atomic ratio of each element in rare earth metals or metals other than rare earth metals. each represents. Also Br
(KGI represents the residual magnetic flux density, iHc (KGe) represents the coercive force, and BHmax represents the maximum magnetic energy product.

As is clear from Table 1, the rare earth/cobalt based magnet according to the present invention contains a rare earth metal and C.

Although it is slightly inferior in coercive force compared to samarium-cobalt based magnets due to the specified composition with other metals mainly composed of .

Table 1 (#Comparative Example) Example 2 In the same manner as in Example 1, sintered magnets were manufactured with predetermined alloy compositions and their magnetic properties were measured. The results are shown in Table 2.

As is clear from Table 2, a residual magnetic flux density Br of 12 KG or more could be obtained by appropriately replacing Co with Fe. In addition, comparative sample N.

, No. 11 loses uniaxial magnetocrystalline anisotropy due to insufficient substitution of Fe, resulting in a significant decrease in overall magnetic property values.

Table 2 (#Comparative Examples) Example 3 First alloys with several specified compositions and 60% by weight Sm-1
A second alloy of 0 wt % Cu-balance CO was melted to obtain a cast ingot, which was then ground in the same manner as in Example 1 and mixed in a ball mill filled with a fluorinated hydrocarbon solution. Then, the alloy composition was adjusted to a predetermined value. Next, molding, sintering, and heat treatment were carried out in the same manner as in Example 1 to produce sintered body samples as shown in Table 3. Note that sintering was carried out at a temperature range of 1040 to 1080°C. The second alloy used in this example serves to facilitate liquid phase sintering and improve the density and magnetic properties of the sintered body. The results of the magnetic properties obtained are shown in Table 3.

As is clear from Table 3, a residual magnetic flux density Br of 12 KG or more was obtained with an appropriate amount of Cu added.

Example 4 A sintered magnet with a predetermined alloy composition was manufactured in the same manner as in Example 1, and its magnetic properties were measured. The results are shown in Table 4.

(#Comparative Example) As is clear from Table 4, it was found that the addition of a small amount of Zi, Ti, or V greatly contributed to the improvement of the coercive force.

(Effects of the Invention) As explained in detail above, according to the permanent magnet of the present invention, the magnetic properties represented by the residual magnetic flux density are significantly improved compared to the conventional samarium-cobalt permanent magnet. This has had the effect of significantly expanding the scope of its use.

Furthermore, the use of rare earth metals mainly consisting of praseodymium, which is cheaper than samarium, has the effect of reducing magnet manufacturing costs.

(2 idiots)

Claims (1)

[Claims] (1) Rare earth metal (R) and other metals in atomic ratio of 1
:7 to 9, and the rare earth metal (R) is Pr.
or a lanthanide element containing Pr at 70 atomic % or more, and the other metals include Co, Fe, Cu and other transition metals (T) at atomic %, and 15 to 40 atomic % Fe-
Contains a proportion of 5 to 20% Cu, 1 to 6% T, and the balance Co,
A permanent magnet characterized in that the other transition metal (T) is made of one or two of Zr, Ti, and V, and is made by sintering a green compact.