JPH01184244A - Permanent magnetic material and its manufacture - Google Patents

Abstract

PURPOSE:To improve the coercive force of the title material while retaining its high residual magnetic flux density by sintering the mold body of the alloy powder in which rare earth elements, Cu, Fe, Zr and Co are specified and the alloy powder in which B is added to said alloy. CONSTITUTION:The alloy consisting of, by weight, 23-28% R (where R denotes one or more kinds among rare earth elements), 4-10% Cu, 15-25% Fe and 0.2-5% Zr and the balance constituted of Co is refined and is pulverized. The alloy to which 0.005-0.06% B is added to the above alloy is furthermore refined and is pulverized. Those alloy powders are then mixed. The mixed alloy powder is then subjected to pressure molding and is thereafter sintered. In this way, the permanent magnetic material contg. <0.005% B and essentially consisting of an R2Co17 intermetallic compound can be obtd.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is directed to a permanent magnet material mainly consisting of an R2Co+v intermetallic compound (where R is one or more rare earth elements). Sm-Co-Cu-'Fe-Z with improved magnetic properties by adding B
The present invention relates to an r-B permanent magnet material anti-permanent magnet material method.

This series of magnets is collectively called the R2C0I7 type, and the representative Sm2CO+7 type magnet exhibits high magnetic properties and excellent thermal stability, so it is suitable for use in electromagnetic conversion equipment (motors, etc.) that requires small size and high performance. Centrally and widely used.

[Conventional technology]

SmzCo+=type Sm −Co −Cu −Fe −
Zr-based permanent magnets are magnets whose performance has been improved by adding a small amount of Zr (Japanese Patent Publication No. 55-48094,
(Special Publication No. 55-47097). In order to improve the performance of this system magnet, the content of Fe should be increased and the main phase Smz (C
o, Fe) It is necessary to increase the saturation magnetization value of the +7 phase. As is known from Japanese Patent Publication No. 55-48094, in general, even in a Zr-added system, when the Fe content is increased to 15% or more, the residual magnetic flux density Br increases, but the coercive force 11 (c) decreases.

Due to this decrease in coercive force, the Fe content in conventional permanent magnets used in practical use is not so high.

In order to solve the above problems, the present inventors filed a patent application filed in
As disclosed in No. 2-57529, an anisotropic bonded magnet was prepared from a Sm-Co-Cu-Fe-Zr alloy with a high Fe content, and its magnetic properties and microstructure were investigated. As a result, it was found that SmzCO7 type precipitates (~0.5 μm) appeared in the microstructure after aging. As a result of compositional analysis, the above precipitate contains Z
It was found that r and Cu were enriched. This alloy undergoes aging to form Smz(Co, Fe)+ phase and Sm
(Co + Cu) phase decomposes into a fine cellular phase with the s phase, while a thin plate-like Zr-enriched phase precipitates. Coercive force is generated by the formation of such a precipitation form. Here, if SmzCo7-type coarse precipitates appeared at the same time, it was thought that the above-mentioned precipitation form would change significantly, and as a result, the coercive force would change. In particular, in the sintered magnet of this alloy, the amount of precipitated Sm2Co7 type phase is large, and therefore Zr and Cu are significantly depleted from the matrix mainly composed of cellular structure, which is thought to result in a decrease in coercive force. Based on the above research results, it was determined that the cause of the low coercive force of the high Fe-containing alloy is the precipitation of the SmzCo7 type phase.

The present inventors disclosed in Japanese Patent Application No. 62-57529 that S by adding 0.005 to 0.06 wt% of B.
It is provided to suppress precipitation of mzCo7 type phase. In the above B addition, the amount of B added is 0.005
In the case of wt% ungrooved, the expression of the effect was unstable.

This is because it is difficult to uniformly disperse B when such a low B content is added.

[Problem that the invention seeks to solve]

The present invention is based on RZGO+? Type Sm -Co -Cu -
0.00!5 wt% in Fe-Zr permanent magnet alloy
The purpose of the present invention is to provide a permanent magnet material that has both a high residual magnetic flux density and a high coercive force by adding less than 100% of B, and at the same time, to provide a method for stably manufacturing it.

[Failure to solve the problem]

The permanent magnet material of the present invention has a weight percentage (wt%) of 2
3 to 28% R (R is one or more rare earth elements), 4 to 10% Cq, 15 to 25% Fe, 0.
The alloy is characterized by containing less than 0.005% of B in an alloy consisting of 2 to 5% of Zr and the balance being Co and unavoidable impurities. The manufacturing method of this permanent magnet material consists of 23 to 28% R (however, R is one or more rare earth elements) and 4 to 10% C in terms of weight percentage (wt%).
u, 15-25% Fe, 0.2-5% Zr, and the balance is CO, and 23-2B% R (however, R is one or more rare earth elements), 4 ~10%
Cu, 15-25% Fe, 0.2-5% Zr,
It is characterized by mixing an alloy powder consisting of 0.005 to 0.06% B and the balance being Co, and sintering the mixture after pressure forming.

[For production]

Precipitation in alloys is often influenced by the addition of trace elements. For example, the bainite transformation in low carbon steels is significantly retarded by the addition of only 1 bit% of B (M, Ueno and T, Inoue).

Trans, l5IJ, Vol, 13.1973.
P210 ), the present inventors newly calculated 0.005
wt% ungrooved trace amount of B is Sm-Co-Cu-P
It has been found that even if B is added to an e-Zr alloy, if B can be uniformly dispersed, precipitation of Sm and Co7 type phases, which are harmful to magnetic properties, can be suppressed.

Here, since the amount of B added is very small, there is almost no decrease in saturation magnetization. Therefore, by adding B, the coercive force can be improved while maintaining a high residual magnetic flux density.

Below, the magnet alloy R-Co-Cu-Fe-Zr of the present invention
- The components of the B system will be mentioned.

In the R-Co-Cu-Fe-Zr-B system of the present invention, R is a rare earth element mainly composed of Sm;
If it is less than 28 wt%, sufficient coercive force cannot be obtained, and if it exceeds 28 wt%, the saturation magnetization is low. If Cu is less than 4 ivt%, a sufficient coercive force cannot be obtained, and if it exceeds 10 wt%, the saturation magnetization becomes low. If Re is less than 15 wt%, a sufficiently high saturation magnetization cannot be obtained, and if it is more than 25 wt%, the coercive force is low. Zr has a low C content as known from Japanese Patent Publication No. 55-48094.
In a wood-based magnetic alloy with a high Fe content, it is necessary to add it in a range of 0.2 to 5 %. That is, Zr is 0.2w
If it is less than t%, a sufficient coercive force cannot be obtained, and if it exceeds 5wt%, the saturation magnetization decreases significantly. B, which is the main focus of the present invention, improves the coercive force in an extremely small amount of less than 0.005 ivt% by uniform dispersion. Also, since B is a non-magnetic element,
Addition of too much B is not preferable because it causes a decrease in saturation magnetization.

An example of adding B to Sm2GO+ system magnet alloy is disclosed in Japanese Patent Application Laid-Open No.
5-115304, JP 56-44741, JP 59-10562, JP 60-23
There are those described in Japanese Patent Application Laid-Open No. 8436 and Japanese Patent Application Laid-Open No. 1984-238437, but both of them contain an extremely large amount of B, and these methods cannot produce the desired permanent magnet material with high residual magnetic flux density and high coercive force. You can't get it. As disclosed by the present inventors in Japanese Patent Application No. 62-57529, it is appropriate to add B in an amount of 0.06 wt% or less.

Next, the means for uniformly dispersing a very small amount of B, which is the structure of the present invention, will be described.

When producing an anisotropic sintered magnet using a powder metallurgy method, an alloy magnet having a desired composition can be obtained by mixing two or more types of alloy powders. According to the experience of the present inventors, 0.005
It is extremely difficult to uniformly contain a trace amount of wt% ungrooved B in an alloy.

As an alternative method, the present inventors have proposed a method in which an alloy powder without B additives and an alloy powder with 0.005 to 0.06 iyt% B added are mixed in a predetermined ratio, and the mixture is press-formed and then sintered. found it to be effective. This method made it possible to add a trace amount of B as in the present invention. B is 0.
The alloy containing 005 to 0.06 wt% is R2C0,7
While keeping the phase as the main phase, its melting point is 10 to 30"C lower than the melting point of the B-free alloy. Therefore, the B-added alloy powder is mixed with the B-added alloy powder and sintered. In this case, since the B-added alloy powder acts as a sintering aid, good sintering can be achieved at low temperatures and in a short time.This method significantly reduces deformation of the sintered crystal.

A small amount of B added in the R2Co, type 7 magnet alloy segregates in atomic form at grain boundaries, sub-grain boundaries, etc., and suppresses grain boundary precipitation of the R2CO7 type phase by lowering grain boundary energy. This improves the coercive force as described above.

〔Example〕

Example 1 Alloy composition is Co 24.8wt%Sm 6.0wt
%Cu-19,0wt%Fe-2,5wt%Zr alloy and Co 24.9Hj%Sm 6.0wt%Cu
18.9wt%Fe 2.6wt%Zr -0,
An alloy containing 0.023 wt% B was produced by high frequency induction melting. These two types of alloy slabs were crushed to a particle size of 500 μm or less and mixed in various proportions. As a result, several types of mixed alloy powders having different B contents were obtained, and subsequently, the mixed alloy powders were finely pulverized using a ball mill. The finely pulverized powder was compression molded under a pressure of 2 tons/cTN in a magnetic field of 16 kOe. Next, the molded body was heated to 1180°C to 1210°C.
Sinter for 1 hour at an optimal temperature in the range of 1130
Solution treatment was carried out for 16 hours at an optimal temperature ranging from °C to 1160 °C. As an aging treatment after solution treatment, it was held at 850°C for 1 hour, and then cooled to 400°C at a rate of 1°C/min. The aged sample was subjected to pulse magnetization of 60 kOe, and its magnetic properties were measured using a self-recording magnetometer.

Figure 1 shows the cases in which no B is added, the cases in which 0.005 wt% of ungrooved trace amount of B is added, and the cases in which 0.038 wt% of B is added.
This shows the magnetic properties when adding . As is clear from the figure, the addition of a very small amount of B significantly improves the coercive force iHc. Due to this increase in coercive force, the maximum energy product (BH) □8 is 24 in the case without B addition, and 6 M GO
28. in the case of B addition of less than 0.005 wt% from e.
Improved to 1-2 B, '6 MGOe. Addition of a large amount of B tends to reduce coercive force.

Figure 2 (a) is an alloy without B additive, and (b) is 0.0038
It is a microstructure photograph taken by an optical microscope after aging treatment of an alloy to which wt% f71B is added. In the B-free alloy, a large amount of SmzCo7 type precipitates of around 0.5 μm are precipitated, which causes a decrease in coercive force, but the amount is 0.0038 wt%.
This is hardly seen in alloys containing B.

This suppression of precipitation of the Sm2Co7 phase by the addition of B is the cause of the above-mentioned improvement in coercive force.

Example 2 Composition is Co-15.0 ivt% Sm-10.2 wt%
Nd-8, 1-t%Cu-15, 5wt%Fe-1,
9wt%Zr (alloy S) and Co-15,0wt%Sm
-10.2wt%Nd 8.1wt%Cu -15
,5wt%Fe-1,9iyt%Zr-0,0019
An alloy magnet having wt% B (alloy T) was produced in the same manner as in Example 1. Table 1 shows their magnetic properties. As is clear from the table, even when the rare earth element R was a mixture of Sm and Nd, the coercive force was significantly improved by adding a very small amount of B, and a practically usable magnet was obtained.

Table 1 [Effects of the invention] By uniformly adding a very small amount of B according to the present invention, RzCo
The coercive force of the +q type magnet has been significantly improved. As a result, a high coercive force was obtained even in an alloy with a high Fe content, and a high maximum energy product was obtained due to the synergistic effect with the large saturation magnetization of the alloy.

In recent years, magnet-applied devices have tended to be smaller and thinner, so the magnets used there have also been increasingly thin-walled. When a small-thick magnet is magnetized in the thickness direction and incorporated into a device, a high coercive force is required to prevent self-demagnetization. By providing a magnet with a high coercive force and a high residual magnetic flux density according to the present invention, more efficient small-sized and thin-walled magnet-applied devices can be manufactured.

Furthermore, by applying a method of mixing and sintering the powder of the B-free alloy and the powder of the B-added alloy, the deformation of the sintered crystals was significantly reduced, and the product yield was significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the magnetic properties as a function of the B content, and FIGS. 2(a) and 2(b) are photographs of the metallographic structure taken by an optical microscope showing that the precipitation of the Sm2Co7 phase is suppressed by the addition of B.

Claims (2)

[Claims] (1) Weight percentage (wt%): 23-28% R (R is one or more rare earth elements), 4-10%
of Cu, 15 to 25% of Fe, 0.2 to 5% of Zr, and the balance being Co and unavoidable impurities, which is characterized by containing less than 0.005% of B. . (2) Weight percentage (wt%): 23-28% R (R is one or more rare earth elements), 4-10%
of Cu, 15 to 25% of Fe, 0.2 to 5% of Zr, and the balance of Co, and 23 to 28% of R(
However, R is one or more rare earth elements), 4 to 10
% Cu, 15-25% Fe, 0.2-5% Zr,
The permanent material according to claim 1, characterized in that an alloy powder consisting of 0.005 to 0.06% B and the balance Co is mixed, and the mixed alloy powder is sintered after pressure molding. Method of manufacturing magnetic materials.