JPS5927086B2 - Temperature coefficient adjustment method for magnetic induction in rare earth-cobalt permanent magnets - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to rare earth cobalt permanent magnets, and in particular, it is an object of the present invention to provide a method for adjusting the temperature coefficient of magnetic induction thereof.

The temperature coefficient of magnetic induction Bd of typical permanent magnets is approximately -0.18%/℃ for Ba ferrite type and approximately -0 for alnico type.
．． 025%/℃, about -O in SmCo5 system, 05cf6/
It is ℃.

Although SmCo5-based magnets have superior magnetic properties compared to Alnico-based magnets, they cannot be applied to electrical measuring instruments because of their inferior temperature coefficients as described above.

The temperature coefficient of the magnetic induction Bd of the above-mentioned representative permanent magnet is a negative temperature coefficient, but if it is possible to manufacture a permanent magnet that exhibits a temperature coefficient of a desired positive value, it is possible to produce a negative temperature coefficient as described above. By combining it with a permanent magnet that has a temperature coefficient, an excellent magnetic circuit can be realized.

The present invention aims to eliminate the above-mentioned drawbacks of SmCo5-based magnets and to provide a permanent magnet that can satisfy the above-mentioned requirements.

The present invention is based on SmCo5 alloy, GdCo5 alloy or Er
The temperature coefficient of the permanent magnet obtained by mixing with Co5 alloy is the mixing ratio (weight ratio) of the GdCo5 alloy or ErCo5 alloy.

The same applies hereinafter unless otherwise specified. ), and by clarifying the relationship between these mixing ratios and temperature coefficients, it has become possible to realize permanent magnets exhibiting desired temperature coefficients. The present invention will be explained below with reference to the drawings.

Figure 1a shows the temperature change of the demagnetization curve of a magnet made of SmCo5 alloy powder containing 34.1wt% Sm with a particle size of around 3μ and molded in a magnetic field at a pressure of 5 to d.
．． 5 tons of GdCo5 alloy powder containing 8 wt% Gd
//c Temperature change in the demagnetization curve of a magnet molded in a magnetic field at a pressure of Tl, c is 35.5 wt% Er with a particle size of around 3.5 μ
It shows the temperature change of the demagnetization curve of a magnet made by molding ErCo5 alloy powder containing ErCo5 in a magnetic field at a pressure of 5 tons/cll, and all measurements were taken in the atmosphere.

A magnet with a permeance coefficient of about 1.0 was prepared by variously mixing SmC05, GdC05 and ErCo5. At this time, the temperature coefficient Tk of magnetic induction of the magnet and the mixed G
The relationship between the total weight of dCO5 and ErCO5 and the mixing ratio with respect to the total weight of the magnet was as shown in FIG. In Figure 2, there is a wide range in the mixing ratio and temperature coefficient due to magnetic induction Bd.
This is the range of variation in the temperature coefficient Tk that occurs due to the accuracy of the flux meter used for measurement. As shown in Figure 2, the temperature coefficient of magnetic induction of a mixture of alloy powders changes from negative to positive as the mixing ratio increases, but linearly until the temperature coefficient reaches zero, and the temperature coefficient changes from positive to positive. The range changes in a curved manner. Figure 3a shows SmCO5 alloy powder and GdCO5
The demagnetization curves at room temperature of magnets made by mixing SmCO5 alloy powder and ErCO5 alloy powder are shown for various mixing ratios of GdCO5 alloy powder to the total amount of the magnet. The demagnetization curve for the magnet made by the above method is shown in the same way as in FIG. 3a.

From FIG. 3, it can be inferred that the relationship shown in FIG. 2 holds for the magnets at all operating points.

Examples of the present invention will be described below. Example 1 SmCO5 alloy containing 34.1 wt% Sm, 33.8
GdCO5 alloy containing wt% Gd and 35.5wt
% of Er is ground to 3.0 to 4.0μ, and the temperature coefficient Tk [×10-2%/℃ is shown in Fig. 2].
) to satisfy the mixing ratio of 0.5 near O.
and O5 alloy powder at a ratio of 1:1 (however, this is a weight ratio).

The same applies hereinafter unless otherwise specified. ) and mix with
In addition, SmCO5 alloy powder, ErCO5 alloy powder and ErC
O5 alloy powder was mixed at a ratio of 1:1, each mixture was oriented in a magnetic field and compression molded, and the resulting green compact was impregnated with an organic medium to form an organic medium bonded magnet. Each of the obtained magnets has a dimension ratio L/D'-0.4 (permeance coefficient B
/H'-. 1.0) and the temperature coefficient was measured.
The temperature coefficients from room temperature to 80°C were as shown in Table 1. It is confirmed that the temperature coefficient shown in Table 1 is within the range of the temperature coefficient in the case of the mixing ratio in FIG. 2. Example 2 The alloy powder used in Example 1 was mixed with SmCO so as to satisfy the mixing ratio such that the temperature coefficient was positive in Fig. 2.
5 alloy powder and GdCO5 alloy powder were mixed at a ratio of 3:7 (mixing ratio 0.7), while SmCO5 alloy powder and GdCO5 alloy powder were mixed at a ratio of 3:7 (mixing ratio 0.7).
:8 (mixing ratio: 0.8), and both mixtures were made into organic medium bonded magnets through the same steps as in Example 1.

Each of the obtained magnets has a dimensional ratio L/D'-. It was processed to a temperature of 0.4 and the temperature coefficient was measured. The temperature coefficients from room temperature to 80°C were as shown in Table 2. It was confirmed that the temperature coefficient in Table 2 was within the range of the temperature coefficient at the mixing ratio shown in FIG. 2, as in Example 1. Example 3 Using the alloy powder used in Example 1, SmCO5 alloy powder 8
0wt%, GdCO5 alloy powder 15wt%, ErCO5
The alloy powders were mixed at a ratio of 5 wt % (mixing ratio 0.2), and an organic medium bonded magnet was produced by the same manufacturing method as in Example 1.

The obtained magnet was processed to have a dimension ratio of L/D'-0.4, and its temperature coefficient was measured. The temperature coefficient from room temperature to 80℃ is -2
．． It was confirmed that the temperature coefficient was 8×10 −2%/° C., which was within the range of the temperature coefficient shown in FIG. 2 at the mixing ratio. Example 4 37.0 wt% SmCO5 alloy and 338 wt% GdC
The O5 alloy was ground to 3.0 to 4.0μ, and the SmCO5 alloy powder and GdCO5 alloy powder were mixed at a ratio of 4:1 (mixing ratio 0).
．． 2), mixed in a magnetic field orientation and compression molded,
The obtained green compact was sintered at 1100 to 1150°C for 1 hour to obtain a sintered body.

Thereafter, the sintered body was heat-treated at 800 to 900°C for 1 hour to obtain a sintered magnet. The dimension ratio of the obtained magnet is L/D! -0.
4 and the temperature coefficient was measured. The temperature coefficient from room temperature to 150°C is -3.1 x 10-201)/°C,
It was confirmed that the temperature coefficient was within the range of the temperature coefficient at the mixing ratio shown in FIG. From the above examples, whether GdCO5 alloy powder or ErCO5 alloy powder, which is a mixed alloy powder with respect to SmcO5 alloy powder, is used alone or in combination, it is within the range of the curve shown in Figure 2, and the final temperature It is understood that the factors that change the coefficient are directly related to the mixing ratio of the mixed alloy powder, and that the same relationship is shown whether the magnet shape is a bonded type or a sintered type.

Therefore, by using the relationship between the mixing ratio of the mixed alloy powder to the total amount of the magnet and the temperature coefficient shown in FIG. 2, it is possible to manufacture a rare earth cobalt permanent magnet exhibiting a desired temperature coefficient.

If the curve shown in FIG. 2 is expressed in a mathematical formula, it will be as follows.

In other words, the mixing ratio of the mixed alloy powder to the total amount of the magnet is x
The desired temperature coefficient is Tk.

However, if a large amount of GdCO5 alloy powder or ErCO5 alloy powder is contained, the magnetic properties deteriorate as shown in FIG. 3, so it is preferable that the temperature coefficient be within a range where the temperature coefficient can be improved to the maximum extent possible.

From this, it is a practical guideline that the mixing ratio is less than 0.77. More actively, it is desired that the mixing ratio be 0.5 or less. In addition, in the above example, G is added to the SmCO5 alloy powder.
Although dCO5 or ErcO5 alloy powder was added, Sm-Gd-CO or Sm-Er-CO ternary alloy powder containing Gd or Er was prepared in advance, and then Sm
-Gd contained in the whole by adding CO binary alloy powder
It is also possible to give a desired temperature coefficient by adjusting the proportions of and Er. An example in this case will be described below.

First, an alloy ingot represented by (GdO.27smO.73)CO4.67 was prepared, and the following samples were obtained from it to obtain sintered magnets having the characteristics shown in Table 3.

The sintering time is 1 hour, and the magnetization is 800 to 90%. This not only makes it possible to create smaller and better measuring instruments, but also allows magnets with a positive temperature coefficient to be combined with existing magnets to create an unprecedented magnetic circuit design. Therefore, the role played by the present invention in industry is extremely large.

[Brief explanation of drawings]

FIG. 1a is a diagram showing temperature changes in the demagnetization curve of SmCO5 alloy powder, b is a diagram showing temperature changes in the demagnetization curve of GdCO5 alloy powder, and FIG. 1c is a diagram showing changes in the demagnetization curve of ErCO5 alloy powder.

Claims (1)

[Scope of Claims] 1 SmCo_5 and at least one of GdCo_5 and ErCo_5 are expressed by the following formula (1) when the total weight of the magnet is 1.
), weight ratio x given by (2) (however, X<0.7
7) A method for adjusting the temperature coefficient of magnetic induction of a rare earth-cobalt permanent magnet, which is characterized by adjusting the temperature coefficient of magnetic induction to a desired value T_k (×10^-^2%/°C) by mixing. If T_k≦0, 0.1×T_k+0.43≦x≦0.1×T_k+0.
50...(1) If T_k>0, 022√(T_k+2.
34) +0.083≦x≦0.22√(T_k+2.1
4) +0.172………………………………(2)