JP2001284111A - High heat-resistant permanent magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sintered permanent magnet, having a high coercive force without having to reduce a saturated magnetic flux density and a residual magnetic flux density and exhibiting superior high temperature characteristics and long-term stability. SOLUTION: A high heat resistant permanent magnet consists of a composition of formula R1XR2YCoZGaUMVBWFe100-X-Y-Z-U-V-W, (where R1 is at least one type of light rare earth element, R2 is at least one type of heavy rare earth element, M is at least one type selected from among Al, Si, Cu and Sn, X, Y, Z, U, V and W are by atomic %, inequalities 7<=X+Y<=20, 1.5<=Y<=10, 6<=Z<=30, 0.4<=U<=2, 0.1<=V<=1/5, 2<=W<=20 are satisfied).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a permanent magnet,
In particular, it relates to a sintered permanent magnet that requires high heat resistance.

[0002]

2. Description of the Related Art In recent years, as high-performance rare earth permanent magnets, R
-Fe-B-based magnets (R is a rare earth element) have been used in place of R-Co-based magnets due to their high magnetic properties. This tendency is remarkable in the field of various small electric appliances which are extremely demanded for miniaturization and are not exposed to such a high temperature.

On the other hand, when considering application to electric vehicles (EV) and various industrial motors, heat resistance has also been required at the same time. However, the R-Fe-B based magnet proposed in the early stage of development had a drawback of low high-temperature characteristics, and it was difficult to replace with an R-Co based magnet having a high Curie temperature at a high temperature.

As means for improving characteristics at high temperatures,
Curie temperature (T_c) And keeping at room temperature
Magnetic force (_iH_c) (Generally permanent magnet
Stone _iH_cDecreases as the temperature rises)
To secure the necessary coercive force at
However, there are the following means.

(1) As the former means, part of Fe is converted to C
It has been proposed to increase _Tc by substituting with o (JP-A-59-64733).

(2) As the latter means, Ti, Ni, B
i, V, Nb, Ta, Cr, Mo, W, Mn, Al, S
It has been proposed to add b, Zr, Hf, Ge, Sn and the like (Japanese Patent Laid-Open No. 59-89401).

(3) As another latter means, Tb, D
Replacing part of Nd with heavy rare earth elements, such as y and Ho, is capable of maintaining high maximum energy product while maintaining _i H
has been proposed to increase _c (Japanese Patent Laid-Open No. 60-323).
No. 06, JP-A-60-34005). These publications, _i H _c when the (BH) max of about 30MGOe those about 9kOe have been described that improve the 12～18KOe.

Further, there is the following proposal. (4) A proposal for finding an effect of improving the coercive force specific to Ga (Japanese Patent No. 2577373). (5) In addition to the specific coercive force improving effect of Ga, Nb,
A proposal aimed at improving the thermal stability by the effect of preventing the crystal grains of W, V, Ta, and Mo from coarsening (Japanese Patent No. 2751109, Japanese Patent Application Laid-Open No. 10-97908).

[0009]

However, the above-mentioned (1)
Each of the related arts (1) to (5) has the following problems.

[0010] (1) with the addition of Co alone, would reduce the _i H _c.

(2) If a large amount of the above-mentioned metal element is added, the saturation magnetic flux density is naturally lowered, and the residual magnetic flux density (Br) is naturally lowered. With a small amount of addition,
The effect of improving the coercive force is very small.

(3) Partial substitution of heavy rare earth elements increases the magnetic anisotropy itself and is very effective in improving the coercive force. However, it also lowers the saturation magnetic flux density and the residual magnetic flux density. Temperature characteristics are not enough.

(4) Although the specific coercive force improving effect of Ga is described, long-term stability is not sufficient.

(5) Regarding the unique coercive force improving effect of Ga
As for Co, T _cWhen there is an improvement effect
However, long-term stability is not enough.

The present invention has been made under the circumstances described above, and has a high coercive force without lowering the residual magnetic flux density, as well as a sintered high heat-resistant permanent magnet exhibiting excellent high-temperature characteristics and long-term stability. The purpose is to provide.

[0016]

In order to obtain the characteristics required for developing a permanent magnet used in a high-temperature environment of about 120 to 180 ° C. such as an electric vehicle, the present inventors I have been working hard. As a result, Co and Ga
And M (M: Al, Si, Cu, Sn) have been studied in detail, and have high residual magnetic flux density, high coercive force, and high heat-resistant permanent magnets with excellent high-temperature characteristics and long-term stability. Was completed.

[0017] The present invention, the composition has the formula _{R1 X R2 Y Co Z Ga U} M V B W Fe
_100-XYZUVW (wherein, R1 is at least one light rare earth element, R2 is at least one heavy rare earth element, and M is Al, S
It represents at least one selected from i, Cu, and Sn, and X, Y, Z, U, V, and W satisfy the following inequality in atomic%. ).

7≤X + Y≤20 1.5≤Y≤10 6≤Z≤30 0.4≤U≤2.0 0.1≤V≤1.5 2≤W≤20.

In the permanent magnet of the present invention, the content (U) of Ga is 0.4 to 2.0% by weight.
0.5-1.5%. As the Co content increases, it is more preferable to increase within the range represented by U ≧ 0.04Z + 0.16.

[0020] Ga is effective in a manner to compensate for the reduction in sudden _i H _c. In Co ≦ 5 atomic%, _i H _c effect of improving Ga added is small, with the residual magnetic flux density is gradually reduced, the temperature coefficient of the residual magnetic flux density is not sufficiently improved.

On the other hand, when Co is 6%, 0.5% of G
Although the same coercive force as that of the low Co region can be obtained by adding a, the addition of 0.5% Ga greatly improves the coercive force when Co is increased, but the addition of 1% or more Ga is preferable.
It is preferable to increase the amount of Ga added according to the Co content.

Specifically, U (% Ga) = 0.04Z
It is preferable that the lower limit be a value represented by (% Co) +0.16. However, if the content of Ga is too large, the effect is saturated and the residual magnetic flux density is reduced. Therefore, the content is preferably 2.0% or less.

Co is effective for improving the temperature characteristics of the residual magnetic flux density, and its amount is 6 to 30 atomic%. If it is less than 6%, the effect is small, while if it exceeds 30%, the residual magnetic flux density decreases. Preferably, it is 6 to 20 atomic%.

R1 and R2 are basic elements of the permanent magnet of the present invention, and contribute to the development of magnetic anisotropy. As the R1 element which is a light rare earth element, Nd and Pr are particularly preferable, and the total of both elements is preferably 50% or more of R1, more preferably 90% or more. Here, the light rare earth elements are Ce, Pr, Nd, Sm, and Eu.
It is.

As the heavy rare earth element R2, D 2
y and Tb are particularly preferred, and the total of both elements is 70% of R2.
It is preferably at least 90%, more preferably at least 90%. Further, it is preferable that the content (Y) of R2 does not exceed 50% of the total amount of rare earth elements (the sum of R1 and R2, X + Y). Here, heavy rare earth elements are Gd, T
b, Dy, Ho, Er, Tm, Yb, Lu. The total amount of light rare earth elements and heavy rare earth elements is 7 to 20%, and a more preferable range is 11 to 18%.

In order to increase the coercive force, it is necessary to add a heavy rare earth element such as Dy. Specifically, in order to obtain a coercive force of about 20 kOe necessary to suppress the irreversible demagnetization rate, a heavy rare earth element of 1.5% or more is required. On the other hand, if the amount of heavy rare earth elements is too large, the magnetization is greatly reduced. The upper limit of the amount of the heavy rare earth element is preferably 50% of the rare earth element.

The element M is Al, Si, Cu, and Sn.
At least one member selected from the group consisting of A
l is most preferred. Even when an element other than Al is contained, it is preferable that 20% or more of the element is Al. More preferably, 80% or more of the M element is Al.
The content of the M element is 0.1 to 1.5%,
%, The squareness is deteriorated. More preferably, it is less than 1%.

The element M has the effect of achieving long-term stability in combination with Ga and Co. Although the cause is not clear, it is presumed that the oxidation of the rare earth-rich phase, which is extremely effective for expressing the coercive force, at a high temperature is suppressed.

B and Fe are elements that form the 2-14-1 phase of the present invention together with rare earth elements. The content of B is 2 to 20%, and preferably 5 to 8%. F
e is the balance of the above elements.

The high heat-resistant permanent magnet having the composition of the present invention has a temperature coefficient α of the residual magnetic flux density at 20 to 150 ° C.
Is preferably α> −0.09% / ° C. In the same range, the temperature coefficient β of the coercive force is β> −0.
Preferably, it is 45% / ° C.

Further, the permanent magnet of the present invention preferably has a room temperature coercive force of 20 kOe or more in order to suppress the irreversible demagnetization rate at a high temperature from the purpose of use. Also,
The permanent magnet of the present invention may use an alloy obtained by ordinary high-frequency melting as a starting material, but preferably has a uniform and fine structure manufactured using a strip cast material or the like as a starting material. The strip cast material is obtained by a so-called strip cast method, that is, a method in which a molten alloy melted in an Ar atmosphere is poured onto a roll rotating at a low speed of about 1 m / s at a peripheral speed and rapidly solidified. It is a strip-shaped alloy having a thickness of about 1 mm.

In this strip cast material, most of the crystal grains are 0.1 to 50 μm in the short axis direction and 0.1 to 50 μm in the long axis direction.
It has a crystal grain size of about 100 μm. However, in order to obtain a uniform and fine structure, a material obtained by a method such as heat treatment in hydrogen may be used instead of the strip casting method.

Since the permanent magnet of the present invention is a sintered type,
Its density is close to true density. Therefore, usually 7.5 to 7.
6. If the density deviates greatly from the true density, excellent magnetic properties cannot be obtained.

The use of the permanent magnet of the present invention relates to a permanent magnet type motor used in a high-temperature environment and to all application parts that may be exposed to high temperatures, such as generators, sensors, and actuators.

Specifically, 1 kW as an industrial motor
It can be used for permanent magnet type motors of class or higher and high temperature permanent magnet type motors of 1 kW class or lower. In addition, motors for power steering, motors for electric vehicles, generators for engines,
It can be used for meter motors, engine control motors, traction control motors, power window motors, and the like.

The present invention can be used for a drive motor, a regenerative brake, and the like also in a vehicle application such as a train. Sensors and actuators are used for automotive throttle actuators, fuel injection actuators, hydraulic control actuators, engine knock sensors, pressure sensors, and the like. Also in the field of home appliances, it can be used for air conditioners, compressor motors and the like. In the electric power field, it can be used for various motors, sensors and actuators in nuclear and thermal power plants.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments and comparative examples will be described below as embodiments of the present invention. (Example 1, Comparative Examples 1 to 5) First, Nd, Pr, Dy,
The raw materials of Fe, Co, Ga, Al, and B were blended at a predetermined ratio shown in Table 1 below and melted in an Ar atmosphere to obtain a molten alloy. Then, the mixture was poured onto a roll rotating at s and rapidly solidified. Thus, a so-called strip cast material was obtained.

After the strip cast material was coarsely pulverized, it was finely pulverized with a jet mill in N ₂ to an average particle diameter of 2 to 3 μm. The obtained powder was pressed and molded in a magnetic field, sintered in a vacuum furnace at 1100 ° C. for 3.6 ks, and
The aging treatment was performed at an aging temperature (for example, 550 ° C.) at which the coercive force was highest in the range of 0 to 650 ° C.

For these samples, the temperature coefficient α of the magnet properties was measured in the range of 20 to 150 ° C. using a BH tracer. Further, these samples were actually incorporated into an IPM-type rotor to produce a permanent magnet motor, and the time-dependent change of Br after operating 1000 hours at an environmental temperature of 50 ° C. was examined. The density of these samples was also measured.

Table 1 below also shows the results of the magnetic characteristics and the like. In Table 1, _i H _c (coercivity) and Br (residual magnetic flux density) is the value at room temperature. The compositions in the table are expressed in atomic%, and Fe _{bal. Means} that the balance is iron when the whole is 100%. The description of the table (Table 2) posted below is the same as above.

[0041]

[Table 1]

As is apparent from Table 1, the amount of Co is 1
The sample containing 6% of Ga, 1% of Ga and 0.5% of Al (Example) has high coercive force and Curie temperature, low temperature coefficient, and excellent long-term stability at high temperature. The aging is the ratio of Br after 1000 hours to the initial Br.

On the other hand, when Co was 1% (Comparative Example 3), a relatively high coercive force of 21.5 kOe was obtained without Ga. However, with such a low Co content (1%), α is low because the Curie temperature is low.

In a Co region where Co is high and Co is high (16%) without addition of Ga (Comparative Example 2), although the Curie temperature is high, the coercive force is reduced by half to 11.0 kOe. % (Comparative Example 1), 20.5 kO
e and a high coercive force are obtained.

Further, when Al is added by 0.5% (Example 1), a higher coercive force of 22.0 kOe can be obtained, and when Al is not added (Comparative Examples 1 and 2), it cannot be obtained. It can be seen that long-term stability at high temperatures can be obtained.

When Al is further increased and Al is added by 1.6% (Comparative Example 4), the coercive force is certainly increased as compared with Comparative Example 2, but as shown in FIG. The squareness deteriorates and high coercive force cannot be utilized at high temperatures. Further, as shown in FIG. 3, in Comparative Example 5 not containing Ga,
Although the squareness is maintained to some extent, the high coercive force is not sufficient. In both cases, the decrease in the residual magnetic flux density cannot be ignored.

Examples 2 to 24 Samples were prepared in the same manner as in Example 1 using raw materials having the compositions shown in Table 2 below, and the characteristics were measured in the same manner.

[0048]

[Table 2]

[0049]

[Table 3]

As can be seen from Table 2 above, Examples 2 to 2
In the case of No. 4, good characteristics were obtained in the coercive force at room temperature, the temperature coefficient of the residual magnetic flux density, and the long-term stability. On the other hand, in the comparative example, the room temperature coercive force is less than 20 kOe, the temperature coefficient of the residual magnetic flux density is lower than -0.09, or the deterioration with time exceeds 10% (lower than 0.9 in the table). Further, in Comparative Example 9, since the magnetic flux density is small in spite of the low coercive force, there is a problem in use at a high temperature.

From the results of the above examples, it was found that the addition of a predetermined amount of heavy rare earth elements, metals such as Co and M, and Ga to the R—Fe—B system (R: rare earth elements) was excellent. It can be seen that a permanent magnet having excellent properties, especially excellent high-temperature properties, can be obtained. All properties cannot be satisfied even if any of the added elements are missing.

[0052]

As described above in detail, according to the present invention, a sintered permanent magnet having a high Curie temperature, a high room temperature coercive force, excellent high-temperature characteristics and excellent long-term stability is provided. It is possible to get.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing demagnetization curves of Example 1 and Comparative Example 4.

FIG. 2 is a characteristic diagram showing demagnetization curves of Example 1 and Comparative Example 5.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takao Sawa 1st Toshiba R & D Center, Komukai-shi, Kawasaki City, Kanagawa Prefecture (72) Inventor Masaji Sabashi Toshiba Komukai, Saiwai-ku, Kawasaki City, Kanagawa Prefecture 1-cho, Toshiba R & D Center, F-term (reference) 4K018 AA27 BA18 BB04 DA11 KA45 5E040 AA04 AA06 AA19 BD01 CA01 NN01 NN06 NN12 NN13 NN17 NN18

Claims (5)

[Claims] 1. A composition wherein _{R1 X R2 Y Co Z Ga U} M V B W Fe
_100-XYZUVW (wherein, R1 is at least one light rare earth element, R2 is at least one heavy rare earth element, and M is Al, S
It represents at least one selected from i, Cu, and Sn, and X, Y, Z, U, V, and W satisfy the following inequality in atomic%. A sintered high heat-resistant permanent magnet characterized by being represented by: 7 ≦ X + Y ≦ 20 1.5 ≦ Y ≦ 10 6 ≦ Z ≦ 30 0.4 ≦ U ≦ 2.0 0.1 ≦ V ≦ 1.5 2 ≦ W ≦ 20 2. The sintered high heat resistant permanent magnet according to claim 1, wherein the temperature coefficient of the residual magnetic flux density at 20 to 150 ° C. is α> −0.09% / ° C. 3. The sintered high heat-resistant permanent magnet according to claim 1, wherein the room temperature coercive force is 20 kOe or more. 4. The sintered high heat-resistant permanent magnet according to claim 1, which is produced using an alloy having an average crystal grain size of 0.1 to 100 μm as a starting material. 5. The sintered high heat-resistant permanent magnet according to claim 1, which is manufactured using a quenched alloy having a thickness of 100 μm to 1 mm as a starting material.