JPH06295808A - Sintered rare earth magnet - Google Patents

Abstract

PURPOSE:To produce a sintered rare earth magnet principally applicable to the motor of an automobile in which the quantity of Fe can be increased by substituting Pr or Nd for a CeCo based magnet alloy having high corrosion resistance, good magnetic characteristics can be achieved without causing significant drop of coercive force, and the material cost is reduced by decreasing the quantity of Co. CONSTITUTION:The sintered rare earth magnet is represented by a formula Ce1-aRa (Co1-x-y-CFexCuyMC)z (where, R represents one or two kinds of Nd, Pr, M represents at least one kind of Zr, Ti, 0.05<=a<=0.50, 20<=x<=0.35, 0.10<=y<=0.20, 0.005<=c<=0.03, 5.5<=z<=6.5 represent atomic ratios). The ratio of Co in the mixture of Co, Fe, Cu and M is set at 60 atomic % or less. Main phase of the sintered magnet has a CaCu5 structure and the maximum energy product thereof is 15MGOe or above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a rare earth sintered magnet having a particularly high iron ratio, which has Ce as one of the main constituent elements and has excellent magnetic properties and good corrosion resistance, and is mainly applied to electric motors for automobiles. .

[0002]

2. Description of the Related Art Permanent magnets having a magnetic characteristic of about 15 to 20 MGOe are considered to be desirable for motors for automobile electrical equipment in terms of motor efficiency. As a material that meets these requirements, Ce-C, which is mainly composed of Ce, is inexpensive and has excellent temperature stability and corrosion resistance.
o A magnet is one of the most suitable. However, the problem is that the price is higher than that of the Nd-Fe-B system permanent magnet due to the high Co ratio, and the magnetic properties are slightly insufficient. If this point is improved, Ce-Co type magnets will be the optimum material for electric motors. Conventionally, the composition of Ce (Co-Fe-Cu) _z based magnets has a low ratio of rare earth elements to transition metal elements (Z value) of about 5 and iron content is at most about 10% (atomic percentage ratio) of transition metals. there were. The magnetic properties obtained as a sintered magnet were at most about 10 to 14 MGOe. As a rare earth sintered magnet, the magnetic properties are low and the Co content is high. Although it is superior in magnetic characteristics to the isotropic Nd-Fe-B system quenched ribbon bonded magnet, its price is high, so that practical use examples are limited.

Several attempts have been made to improve the magnetic properties of Ce type magnets, and additives (M: Zr, Ti, Mn,
Zn, etc.) and the replacement of Ce with Sm have been reported. Usually, the additive M can increase the Fe content and increase the Z value, and is therefore effective in improving the magnetic properties. Sm (Co-
In the case of the Fe-Cu-M) _z system (z ≧ 7), such additives were very effective. However, in the Ce-based alloy, although various elements have been tried to be added, a sufficient coercive force cannot be ensured, so that a significant improvement in characteristics as compared with the conventional composition has not been realized.

The cause is considered to be as follows. That is, in the composition using the additive, it is necessary to raise the z value to approach the Ce ₂ Co ₁₇ composition. The crystal magnetic anisotropy of the Sm ₂ Co ₁₇ compound is positive, and its value is as high as 10 ⁷ erg / cc order. However, since the crystal magnetic anisotropy of the Ce ₂ Co ₁₇ compound is negative, it is considered that sufficient coercive force cannot be obtained even if an additive is used and the z value is increased. On the other hand, C
Substituting e for Sm is very effective for improving the magnetic properties, especially the coercive force, because the crystal magnetic anisotropy of Sm ₂ Co ₁₇ can be utilized. However, since the raw material cost is increased by using Sm, the practical value is lowered when the magnetic property per cost unit is compared with that of the isotropic Nd-Fe-B system quenched ribbon bonded magnet. In order to improve the magnetic properties without increasing the raw material cost, it is effective to increase the amount of replacement of Co with Fe.

The present inventors have previously proposed that in the Ce-based magnet,
Composition and manufacturing method capable of significantly increasing Fe amount (Patent Document 0
1-225101)) was proposed. However, in that invention, it was necessary to increase the amount of Cu as well as the amount of Fe. This is because the 1-5 phase cannot exist stably only by increasing the Fe amount. Therefore, F
The increase in the saturation magnetization due to the increase in the amount of e and the decrease in the saturation magnetization due to the increase in the amount of Cu were offset, and the improvement of the magnetic characteristics, that is, the increase of the saturation magnetization was not realized.

[0006]

SUMMARY OF THE INVENTION The present invention reduces the amount of Co in a Ce-based magnet and increases the amount of Fe without using Sm to secure a sufficient coercive force, thereby reducing the cost and improving the magnetic characteristics. The purpose is to achieve both.

[0007]

In order to solve such a problem, the present inventor has thoroughly reviewed the composition of Ce (Co Fe Cu) ₅ system magnets, found the constituent element ratios, and completed the present invention. And the summary is Ce _{1-a Ra} (Co _1-xyC Fe _x Cu _y M
_C ) _z (where R is one or two of Nd and Pr. M is Z
At least one of r and Ti. 0.05 ≦ a ≦ 0.50, 0.20 ≦
x ≦ 0.35, 0.10 ≦ у ≦ 0.20, 0.005 ≦ c ≦ 0.03, 5.5 ≦
z ≦ 6.5 represents an atomic ratio), the ratio of Co in Co, Fe, Cu and M is 60 atomic% or less, and the main phase of the sintered magnet is hexagonal Ca. With a Cu ₅ structure, 15MG
A rare earth sintered magnet having a maximum energy product of Oe or more, and a sintered body obtained by sintering the composition alloy powder by a powder sintering method.
A method for producing a rare earth sintered magnet is characterized by performing solution heat treatment at a temperature of ° C.

The present invention will be described in detail below. Ce (Co
A typical composition of the Fe Cu) ₅ magnet is represented by the following formula (1). Ce (Co _0.76 Fe _0.12 Cu _0.12 ) ₅ (1) If the amount of Fe is simply increased with the composition as shown in formula (1),
Rich 1-5 phase and Fe phase are precipitated and become two phase state,
Good magnetic properties cannot be obtained. Increase the solid solution amount of Fe 1
One method is to increase the amount of Cu at the same time, so that Ce (Co _0.60
Fe _0.20 Cu _0.20 ) ₅ is a typical composition, and it has been described above that the present inventors developed and applied for a patent (see Japanese Patent Application Laid-Open No. 01-225101). Since the coexisting phase has moved to the low temperature side, 100% above the sintering temperature.
It is necessary to homogenize the ingot by performing solution treatment at a low temperature of ℃ or more. However, in this composition, the effect due to the increase of the Fe content and Cu content is offset, and the improvement of the magnetic characteristics cannot be expected.

It has already been described that the magnetic characteristics can be improved by substituting a part of Ce with Sm. However, Sm
There was a problem in that the raw material cost was increased by using. On the other hand, it has been considered difficult to replace Ce with a rare earth element other than Sm. Because R
R = Sm has the largest magnetocrystalline anisotropy among Co ₅ compounds
This is because even in the R ₂ Co ₁₇ compound, only R = Sm exhibits a large positive magnetocrystalline anisotropy value. Therefore,
Substitution with a rare earth element other than Sm is expected to lower the coercive force. Therefore, Ce having the composition shown in formula (1) should be replaced by Sm.
Substitution with elements other than was not attempted.

The inventors of the present invention significantly reduced the coercive force by using the composition of the formula (2) in which Ce is partially replaced by Nd or Pr in the composition of the above formula (1) (hereinafter referred to as a substitution system). It was found that the saturation magnetization can be improved without it. Ce _{1-a Ra} (Co _1-xyC Fe _x Cu _y M _C ) _z (2) In the RCo ₅ compound and the R ₂ Co ₁₇ compound, R = Nd, P
The saturation magnetization at r is much higher than that of compounds with R = Ce. In the Ce element, 4f electrons go out of the shell, so 4f = 0, whereas in the Pr and Nd elements, 4f.
There are two and three f electrons. Since the 4f electron contributes to the saturation magnetization of the compound, the saturation magnetization of Pr or Nd system is higher than that of Ce system. Therefore, the saturation magnetization increases in proportion to the substitution amount of Pr and Nd.

On the other hand, the magnetocrystalline anisotropy was considered to decrease in proportion to the substitution ratio of Nd and Pr.
However, as a result of various studies, it was found that the reduction of the magnetocrystalline anisotropy was not proportional to the substitution amount, and the reduction rate was small with respect to the substitution up to half of Ce. For more substitutions the value drops sharply. Ce to Pr
Alternatively, since the coercive force of the system in which Nd is substituted qualitatively shows the same tendency as the change in magnetocrystalline anisotropy, it is possible to substitute Ce in half. Substitution of a rare earth element other than R = Pr, Nd, and Sm is not preferable because the coercive force and the saturation magnetization are greatly reduced.

Another advantage of the substitution system is that the Fe amount and Z value can be increased by substituting Pr and Nd. The Fe amount and Z value can be further increased by adding the additive M. As the M element, Mn, V, Nb, Hf, Ta and the like are also effective, but the effects of Zr and Ti are particularly high. In addition to the increase in saturation magnetization due to the substitution of Pr or Nd, the ratio of transition metal can be increased, so that higher saturation magnetization can be obtained. If the content of each element exceeds the range, the saturation magnetization and coercive force will be significantly reduced, so the content must be within this range. Although adding a trace amount of B element to the composition of the present invention is also effective in increasing the Fe amount, the maximum substitutable Fe amount does not change.

The composition range will be described below based on the equation (2). When the amount of R (one or two types of Nd and Pr) is less than 0.05, the effect of increasing the saturation magnetization is small, and when it exceeds 0.50, the coercive force is greatly decreased, so the amount of R is preferably 0.05 or more and 0.50 or less. The effect of increasing the Fe amount is great when M elements (at least one of Zr and Ti) are used in combination.
As the M element, Mn, V, Nb, Hf, Ta and the like are also effective, but Zr and Ti are particularly good. The amount of M element added is
If it is less than 0.005, the effect of increasing the Fe amount is small and the increase of the saturation magnetization is small, but if it exceeds 0.03, the decrease of the saturation magnetization is large, so that it is preferably within this range.

Fe (0.20≤x≤0.35) and Cu (0.10≤у≤)
If the amount of (0.20) exceeds this range, the magnetic properties are significantly deteriorated and a two-phase state is formed, and sufficient magnetic properties cannot be obtained, so it is preferable to be in this range. It is possible for the z value to take a value of 5 or more as the Fe amount increases. However, it is impossible to have a value of 7 or more as in the Sm system, and it is up to 6. If it is 6 or more, even if the alloy is heat-treated, it is not homogeneous, and good magnetic properties cannot be obtained.

The Fe-rich Ce-based sintered magnet can be manufactured by the powder sintering method which is generally used for rare earth magnets. However, as the Fe content increases, the solid-liquid coexistence region moves to the lower temperature side (the same phenomenon as when the Cu content increases), so a chill-casting of the molten metal by melting can produce a homogeneous alloy ingot. I can't. Therefore, than the cast ingot was directly crushed without good magnetic characteristics are obtained, it is necessary to homogenize by solution heat treating the ingot, if Netsusho sense 5 hours or more at approximately 900 ° C. ~ 1,000 ° C. good. Sintering 1,000 ℃ ~ 1,100
Since it is performed in a vacuum or in an inert gas (for example, Ar gas) at 0 ° C., it is necessary to perform the solution heat treatment on the sintered body in the same temperature range as the solution heat treatment of the alloy after the sintering. By substituting Ce with the R (Nd, Pr) element in this way, it becomes possible to increase the Fe content without increasing the Cu content.
It has become possible to improve the magnetic characteristics of Ce-based magnets.

[0016]

EXAMPLES The embodiments of the present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. Example 1 Compositional formula Ce _1-a Nd _a (Co _res Fe _x Cu _y Zr _c ) _z
In accordance with 99% purity Ce, Nd metal, 99.9% purity C
Weigh o, Fe, Cu, Zr metal to a specified ratio,
Four types of alloys were produced by melting in a high-frequency vacuum melting furnace in a vacuum or in an inert gas and tilt casting in a copper mold. The alloy was subjected to solution heat treatment at 950 ° C. for 8 hours in an Ar gas atmosphere. When the alloy was analyzed, the composition was as shown in Table 1. 20 the alloy with a jaw crusher and a brown mill
After forming coarse powder of mesh or less, it was finely pulverized by a jet mill using a high-pressure nitrogen gas stream to an average particle size of 4 μm. While keeping the fine powder oriented in the magnetic field direction in a static magnetic field of 15 kOe, 1.
Press molding was performed at a pressure of 5 Ton / cm ² to prepare a molded body. 1050 ℃ ~ 1100 ℃ in 250 Torr Ar gas
After sintering for 1 hour at the temperature of 970 ℃ ～ 1000
Solution heat treatment was performed for 2 hours at a temperature of ° C. 5 of the sintered body
After holding at a temperature of 00 ° C to 600 ° C for 3 hours, the sintered magnet was continuously cooled to 200 ° C or lower. The results of measuring the magnetic characteristics of the sintered magnet with a BH tracer are also shown in Table 1. It can be seen that by replacing the Nd element, good magnetic characteristics can be obtained even with a high Fe content composition.

(Comparative Example 1) A magnetic alloy was prepared by treating in the same manner as in Example 1 except that Nd was not added, and the magnetic characteristics were measured and are shown in Table 1.

[0018]

[Table 1]

Example 2 Compositional formula Ce _1-ab Nd _a Pr _b (C
o _1-xyc Fe _x Cu _y Ti _c ) _z according to
d and Pr metal, and Co, Fe, Cu, and Ti metal having a purity of 99.9% were weighed according to a predetermined ratio, and melted and solution-treated in the same manner as in Example 1 to prepare an alloy. When the alloy was analyzed, the composition was as shown in Table 2. The alloy was crushed, oriented in a magnetic field, sintered and heat-treated in the same manner as in Example 1 to prepare a sintered body. When the magnetic properties of the sintered body were measured, the results shown in Table 2 were obtained. It can be seen that good magnetic properties can be obtained in the high Fe region even if the combination of additives and rare earth elements is different.

[0020]

[Table 2]

[0021]

By replacing Ce in the Ce Co system with Pr or Nd, it becomes possible to increase the Fe content and the like.
It became possible to obtain good magnetic properties without causing a large decrease in coercive force. Moreover, since the amount of Co can be reduced, the cost of raw materials can be reduced at the same time, and its utility value is extremely high in industry.

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Claims (3)

[Claims] 1. Ce _{1-a Ra} (Co _1-xyC Fe _x Cu _y M _C ) _z (wherein R is one or two of Nd and Pr. M is at least one of Zr and Ti). 0.05 ≦ a ≦ 0.50, 0.20 ≦ x ≦ 0.3
5, 0.10 ≤ у ≤ 0.20, 0.005 ≤ c ≤ 0.03, 5.5 ≤ z ≤ 6.
5 is a rare earth sintered magnet represented by the atomic ratio). 2. The C in Co, Fe, Cu and M according to claim 1.
The ratio of o is 60 atomic% or less, and the main phase of the sintered magnet is hexagonal C
a rare earth sintered magnet having a Cu ₅ structure and having a maximum energy product of 15 MGOe or more. 3. The composition alloy powder according to claim 1 or 2 is sintered by a powder sintering method to obtain a sintered body, and then the sintered body is obtained.
A method for producing a rare earth sintered magnet, characterized by performing a solution heat treatment at a temperature of 900 to 1,000 ℃.