JPH05267026A - Permanent magnet having excellent thermal stability and corrosion resistance and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve thermal stability by a low-cost element in place of Ga, and to enhance adhesive properties with Cu substrate plating. CONSTITUTION:A permanent magnet is composed of the composition of RaFebCocBdZneCufMgAlh (where R represents at least one kind of rare earth elements containing Nd, Pr and Ce and M at least one kind of V, Mo, Nb and W and the composition satisfies 5<=a<=18at.%, 65<=b<=85at.%, 0<=c<=20at.%, 4<=d<=15at.%, e<=7at.%, 0<=f<=7at.%, 0<=g<=5at.% and 0<=h<=2at.%).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-performance rare earth permanent magnet used for VCM (voice coil motor), rotating equipment and the like.

[0002]

2. Description of the Related Art Nd-Fe-B magnets (Patent Publication Sho 6)
3-65742) has a large saturation magnetization and can obtain a high energy product, and thus has come to be used in a wide range of applications. Problems such as heat resistance and corrosion resistance, which have been problems so far, have been solved to some extent, and practically, some problems have been solved. A maximum energy product of 30-40 MGOe has been produced.

[0003]

In order to improve the thermal stability of the Nd-Fe-B magnet, the method of adding Dy to improve the coercive force is generally used. But,
Since Dy is expensive, it is necessary to minimize the amount used. Therefore, Al and Nb are added together with Dy. In addition to this, in order to further improve thermal stability, G
In some cases, a may be added. However, since Ga is expensive, it has been desired to improve the thermal stability with an inexpensive element. Further, conventionally, in order to improve the corrosion resistance, after the processed sample is subjected to acid etching, Cu underlayer plating and Ni plating are generally performed. However, it is desirable to omit the acid etching step in order to shorten the manufacturing process, but there is a problem that the adhesion between the Nd-rich phase and the Cu undercoat is poor.

Therefore, an object of the present invention is to provide a permanent magnet whose thermal stability is improved by using an inexpensive element instead of Ga. A further object of the present invention is to provide a permanent magnet having improved adhesion with the Cu undercoat.

[0005]

Means for Solving the Problems The present inventor has searched for an element which improves thermal stability in place of Ga, and has obtained the following findings. That is, although adding Zn to the Nd-Fe-B ternary system has a certain degree of improvement in coercive force,
It was found that when n and Co were added at the same time, the coercive force was greatly improved and the thermal stability was also improved. Also,
The simultaneous addition of Zn and Co was also effective in improving the corrosion resistance. This is an element that has strong oxidation resistance as Zn is used for galvanizing. Furthermore, since this Zn often enters the Nd-rich phase of this system magnet, it protects the easily corroded phase and is effective in improving the corrosion resistance. there were. Further, the addition of Zn also had the effect of improving the adhesion with the Cu undercoat.
Further, they have found that when Cu is used in this composition system in a range where magnetic properties and thermal stability are not deteriorated, adhesion with Cu undercoating is improved and corrosion resistance is improved. The present invention has been made on the basis of the above findings, and R _a Fe _b C
In _{o c B d Zn e Cu f} M g Al h ( wherein, R represents Nd, Pr, at least one of rare earth elements including Ce, M is V, Mo, Nb, at least one of W, 5 ≦ a ≦ 18 at%, 65 ≦ b ≦ 85
at%, 0 ≦ c ≦ 20 at%, 4 ≦ d ≦ 15 at%,
e ≦ 7 at%, 0 ≦ f ≦ 7 at%, 0 ≦ g ≦ 5 at%,
It is a permanent magnet having a composition of 0 ≦ h ≦ 2 at%).

In the present invention, the rare earth element R is 5 at% or more and 18 at% or less, preferably 10 at% or more, 1
It is contained in a range of 6 at% or less. When R is Pr or Nd, high magnetic characteristics are obtained, and when Tb or Dy is contained, a large coercive force is obtained. In particular, the use of Dy is preferable in terms of cost, and the ratio of Nd and Dy is 99.95:
The range of 0.05 to 80:20 is desirable because a high coercive force can be obtained without increasing the saturation magnetization.

Fe is contained in the range of 65 ≦ b ≦ 85 at%. If it is less than 65 at%, the saturation magnetization is low, and
This is because the coercive force is remarkably reduced when it exceeds t%.

As described above, Co is an element that contributes to the improvement of thermal stability together with Zn, and is contained in the range of 20 at% or less. This is because when it exceeds 20 at%, the saturation magnetization and the coercive force decrease. The ratio of Fe and Co is preferably in the range of 99.95: 0.05 to 77:23 in order to maintain appropriate squareness and coercive force.

The amount of B is preferably 4 ≦ d ≦ 15 at%,
Outside of this range, the residual magnetic flux density and coercive force become small.

Zn is an element that contributes to the improvement of thermal stability together with Co, but if it exceeds 7 at%, the residual magnetic flux density is lowered, so it is made 7 at% or less. 0.01 ≦ e ≦ 4a
It is preferably in the range of t%.

The M element is an element highly effective in suppressing crystal grain growth and improving thermal stability. However, if it is contained excessively, the saturation magnetization is lowered. Therefore, when it is added, its content is preferably 7 at% or less.

Al has a high improvement in coercive force, and is mixed from Ferro-B and at the time of melting. However, if it is added excessively, the Curie temperature is lowered.
t% or less.

Cu is an element that contributes to the improvement of the adhesion to the Cu undercoat and the improvement of the corrosion resistance. However, if it is contained excessively, the residual magnetic flux density and the coercive force are lowered, so 0 ≦ f ≦ 2a
The range is t%.

Next, a method for manufacturing the magnet of the present invention will be described. The magnet of the present invention can be produced by a sintering method. As one of the methods, from a molten alloy having the same composition as the final target composition, an alloy powder is obtained by a well-known ultra-quenching method, or an ingot is prepared and subjected to hydrogen storage / dehydrogenation treatment and then crushed. There is a method in which an alloy powder is obtained, and thereafter, the powder is molded and sintered in a magnetic field. However, Zn
Has a very low melting point and boiling point, and releases a large amount of the above when dissolved, and according to the above method, the Zn content is significantly reduced. Therefore, a Nd-Fe-B-Zn-Co-based Nd-rich alloy having a low melting point is prepared by melting, and the melt is rapidly cooled or hydrogen storage + dehydrogenation is performed, and then crushed and separately prepared Nd-Fe-B. -Mixing with Nb alloy powder, molding, sintering,
By adopting the means of heat treatment, the decrease of Zn can be suppressed.

[0015]

【Example】

Example 1 Composition 1: (Nd _0.9 Dy _0.1 ) _14.8 Fe _76.1-x Co _x B _6.6
Zn _1.0 Nb _1.0 Al _0.5 (x = 0, _1.0, 2.0,
3.0, 4.0, 5.0, 6.0, 7.0), composition 2:
(Nd _0.9 Dy _0.1 ) _14.8 Fe _73.1-x Co _3.0 B _6.6 Zn
_1.0 Nb _1.0 Al _0.5 Cu _x (x = 0, 0.05, 0.1,
0.15, 0.2, 0.25) was prepared, hydrogen was absorbed, and then dehydrogenated while heating at a temperature of 400 to 600 ° C. The obtained alloy powder was coarsely pulverized and finely pulverized, then formed by transverse magnetic field forming, and sintered at 1090 ° C. The obtained sintered body was heat-treated at 600 ° C. to evaluate the magnetic characteristics.

FIG. 1 shows the composition 1 and FIG. 2 shows the evaluation results of the magnetic properties of the composition 2. Apparently, the coercive force increases with the increase of the Co amount, and decreases when the Co amount is 6 at% or more. Also, a slight increase in coercive force can be seen with an increase in the amount of Cu,
It is decreasing soon. Furthermore, x = 0,3,7 of composition 1
The magnet was processed into a shape of Pc = 2, and the change in irreversible demagnetization rate after heating to each temperature was examined. The obtained results are shown in FIG. 3, and the larger the coercive force, the better the thermal stability.

Example 2 Composition 3: (Nd _0.9 Dy _0.1 ) _14.8 Fe _77.1 B _6.6 Mo _1.0
Al _0.5 , composition 4: (Nd _0.9 Dy _0.1 ) _14.8 Fe _76.1 B _6.6 Zn _1.0
Mo _1.0 Al _0.5 , composition 5: (Nd _0.9 Dy _0.1 ) _14.8 Fe _76.05 B _6.6 Zn
_1.0 Mo _1.0 Al _0.5 -Cu _0.05 , composition 6: (Nd _0.9 Dy _0.1 ) _14.8 Fe _73.05 Co _3.0 B
_6.6 Zn _1.0 Mo _1.0 Al _0.5 Cu _0.05 four kinds of molten alloys were prepared, and a sintered magnet was prepared under the conditions of Example 1. These magnets were subjected to Cu undercoating and Ni plating and left in an environment of temperature: 80 ° C. and humidity: 90% to examine corrosion resistance. When the standing time for producing red rust on the surface was examined, the results shown in Table 1 were obtained. It can be seen that the composition 6 in which both Zn and Co are added and the composition 7 in which Cu is further added exhibit the best corrosion resistance.

[0018]

[Table 1]

(Example 3) The pin having the composition 3-7 prepared in Example 2 was subjected to a pin test by similarly plating a Cu undercoat with Ni. In the test, the pin was attached to the plated film with a resin, and then the pin was pulled to measure the peeling strength of the plated film. The results obtained are shown in Table 2.

[0020]

[Table 2]

Example 4 Alloy A: (Nd _0.9 Dy _0.1 ) _12.8 Fe _74.65 Co _3.0 B
Two kinds of melted alloys of _8.0 V _1.0 Al _0.5 Cu _{0.05 and} alloy B: Nd ₆₅ Fe ₂₅ Zn ₁₀ were prepared, hydrogen was absorbed, and then dehydrogenated. After crushing both, mixing at a certain ratio, molding,
Sintered. The magnetic properties obtained are shown in Table 3. As described above, when an Nd-rich alloy was prepared in advance, good results were obtained without significantly losing Zn.

[0022]

[Table 3]

[0023]

The thermal stability and corrosion resistance are improved by adding Zn and Co to the Nd-Fe-B system magnet, and the adhesion to the Cu undercoat is improved by adding a very small amount of Cu. , Could improve the corrosion resistance.

[Brief description of drawings]

FIG. 1 is a graph showing changes in Br and iHc depending on the amount of Co in a magnet having a composition 1.

FIG. 2 is a graph showing changes in Br and iHc depending on the amount of Cu in a magnet having composition 2.

FIG. 3 is a graph showing changes in the irreversible demagnetization rate depending on the Co amount (x = 0, 3, 7) of composition 1.

Claims (5)

[Claims] 1. R _a Fe _b Co _c B _d Zn _e Cu _f M _g Al _h (wherein R is at least one of rare earth elements including Nd, Pr and Ce, M is V, Mo, Nb, At least one of W is 5 ≦ a ≦ 18 at%, 65 ≦ b ≦ 85.
at%, 0 ≦ c ≦ 20 at% 4 ≦ d ≦ 15 at%, e
≦ 7 at%, 0 ≦ f ≦ 7 at%, 0 ≦ g ≦ 5 at%, 0
≦ h ≦ 2 at%), and a permanent magnet having good thermal stability and corrosion resistance. 2. R is one or more of Nd, Pr, Dy, and Ce, and 10 ≦ a ≦ 15 at% and 5 ≦ d ≦ 1.
The permanent magnet having good thermal stability and good corrosion resistance according to claim 1, wherein 5 at% and f ≦ 2 at%. 3. The thermal stability and corrosion resistance according to claim 1, wherein R contains Nd and Dy, and the ratio of Nd and Dy is in the range of 99.95: 0.05 to 80:20. permanent magnet. 4. The ratio of Fe and Co is 99.95: 0.0.
The permanent magnet having good thermal stability and corrosion resistance according to claim 1, which is in the range of 5 to 77:23. 5. Nd-rich Nd-Fe-B-Zn-C
A method for producing a permanent magnet, which comprises mixing an o alloy powder and an Nd-Fe-B-Nb alloy powder so as to have the composition according to claim 1 and then sintering the mixture.