JPH06112026A - Permanent magnet with excellent thermal stability and corrosion-resisting property and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve thermal stability using an inexpensive element instead of Ga, and also to improve the close adhesiveness between the base layer Cu and plating. CONSTITUTION:This permanent magnet consists of the composition of (Nd1-x-y-zCexPryDyz)aFebCocBdZneCufMgAlho (in the form of 0.001<=X<=0.1, 0.05<=Y<=0.5, 0.001<=Z<=0.25, M indicates at least a kind selected from V, Mo, Nb and W, 5<=a<=18wt.%, 65<=b<=85wt.%, 0<=c<=20wt.%, 4<=d<=15wt.%, 0<=e<=7wt.%, 0<=f<=7wt.%, 0<=g<=5wt.% and 0<=h<=2wt.%).

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. Maximum energy product is also 3
The product of 0-40 MGOe came to be 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 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 undercoating and Ni plating are generally performed. However, it is desirable to omit the acid etching process 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. Another object of the present invention is to provide a permanent magnet having improved adhesion to the Cu undercoat.

[0005]

[Means for Solving the Problem] The present inventor has obtained the following findings as a result of searching for an element which improves thermal stability in place of Ga. That is, although addition of Zn to the Nd-Fe-B ternary system has some effect on improving coercive force,
It was found that when Zn and Co were added at the same time, the coercive force was further greatly improved and the thermal stability was also improved. Further, simultaneous addition of Zn and Co was effective in improving corrosion resistance. This is an element that has strong resistance to oxidation so that Zn is used for galvanizing. Furthermore, this Zn is the N of the present magnet.
Since a large amount of d-rich was included in the phase, it was effective in improving the corrosion resistance because it protects the phase that is easily corroded. Also, this Zn
The addition also had the effect of improving the adhesion to 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.
However, in mass production, Ce,
Rare earth elements such as Pr are also used. Among these, it was found that the use of Pr is effective for further improving the magnet characteristics. Therefore, a magnet that is inexpensive as a raw material and has excellent thermal stability and corrosion resistance was obtained. The present invention has been made based on the above _{findings, (Nd 1-XYZ Ce X} Pr Y Dy Z) a Fe b Co c B d Zn e
Cu _f M _g Al _h (where 0.001 ≦ X ≦ 0.1, 0.05 ≦ Y ≦
0.5, 0.001 ≦ Z ≦ 0.25, M is V, Mo, N
at least one of b and W, 5 ≦ a ≦ 18 at%,
65 ≦ b ≦ 85 at%, 0 ≦ c ≦ 20 at% 4 ≦ d ≦ 15 at%, 0 ≦ e ≦ 7 at%, 0 ≦ f ≦ 7a
t%, 0 ≦ g ≦ 5 at%, 0 ≦ h ≦ 2 at%), which is a permanent magnet having excellent thermal stability and corrosion resistance.

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 the range of 6 at% or less. Excessive addition of Ce is not preferable, and 0.001 ≦ X ≦ 0.1 is desirable. P
If r is within the range of 0.05 ≦ Y ≦ 0.5, coercive force
Although it is effective in improving heat resistance, addition of more than that decreases saturation magnetization and corrosion resistance. A large coercive force is obtained when Dy is included, and the ratio of Nd and Dy is 9
The range of 9.95: 0.05 to 80:20 is desirable because a high coercive force can be obtained without significantly reducing 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 85 a
This is because if it exceeds t%, the coercive force remarkably decreases.

Co is an element that contributes to the improvement of thermal stability together with Zn as described above, 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 to 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 effective in suppressing the crystal grain growth and improving the 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 an effect of improving 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 that 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 known ultra-quenching method, or an ingot is prepared and hydrogen absorption / dehydrogenation treatment is applied to this ingot, followed by pulverization. There is a method in which an alloy powder is obtained by using the above method, and thereafter, it 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 the above method causes a remarkable decrease in the amount of Zn. Therefore, an Nd-Fe-B-Zn-Co-based Nd-rich alloy having a low melting point is prepared by melting, melt quenching or hydrogen storage + dehydrogenation is performed, and then crushed and separately prepared Nd-Fe-B. -Mixing with Nb alloy powder, molding, sintering,
By adopting a means of heat treatment, the decrease of Zn can be suppressed.

[0015]

【Example】

 (Example 1) Composition 1: (Nd_0.9-xPr_xDy_0.1)_14.4Fe_71.5Co
_5.0B_6.6Zn_1.0Nb_1.0 Al_0.5 (X = 0,0.
1, 0.2, 0.3, 0.4, 0.5) was prepared, and hydrogen was occluded, then 400-600
It was dehydrogenated while heating to a temperature of ° C. The obtained alloy powder
After coarsely pulverizing and finely pulverizing, it is molded by transverse magnetic field molding.
Sintered at 0 ° C. Heat treatment of the obtained sintered body at 600 ° C
Then, the magnetic characteristics were evaluated.

FIG. 1 shows the evaluation results of the magnetic characteristics of composition 1. Apparently, the coercive force increases with the increase of the Pr amount. Further, the magnet was processed into a shape of Pc = 2, and the change in the irreversible demagnetization rate after heating to 200 ° C. was examined. As a result, the larger the coercive force, the better the thermal stability.

(Example 2) Composition 2: (Nd _0.9 Dy _0.1 ) _14.8 Fe _77.1 B _6.6 Mo _1.0
Al _0.5 , composition 3: (Nd _0.9 Dy _0.1 ) _14.8 Fe _76.1 B _6.6 Zn _1.0
Mo _1.0 Al _0.5 , composition 4: (Nd _0.9 Dy _0.1 ) _14.8 Fe _71.1 Co _5.0 B _6.6
Zn _1.0 Mo _1.0 Al _0.5 , composition 5: (Nd _0.5 Pr _0.3 Dy _0.1 ) _14.8 Fe _71.1 C
Create a o _5.0 4 kinds of dissolution Alloy _{B 6.6 Zn 1.0 Mo 1. 0 Al} 0.5, and create a sintered magnet under the conditions of Example 1. Cu undercoat and Ni plating were applied to these magnets, and the magnets were left in an environment of temperature: 80 ° C. and humidity: 90% to examine the corrosion resistance. When the standing time for producing red rust on the surface was examined, the results shown in Table 1 were obtained.

[0018]

[Table 1]

(Example 3) The pin having the composition 2-5 prepared in Example 2 was subjected to a pin test by similarly plating a Cu undercoat with Ni. In the test, after the pins were bonded to the plating film with a resin, the pins were pulled and the strength of peeling of the plating film was measured. The obtained results are shown in Table 2.

[0020]

[Table 2]

[0021]

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. further,
By adding Pr, a magnet which is inexpensive as a raw material and has excellent coercive force and heat resistance was obtained.

[Brief description of drawings]

FIG. 1 shows Br, iHc, and Pr depending on the Pr content of a magnet of composition 1.
It is a graph which shows the change of (BH) max and an irreversible demagnetization rate after heating at 200 degreeC.

Claims (4)

[Claims] 1. (Nd _{1 -XYZ} Ce _X Pr _Y Dy _Z ) _a Fe _b C
In _{o c B d Zn e Cu f} M g Al h ( where, 0.001 ≦ X ≦ 0.1,0.05 ≦ Y ≦
0.5, 0.001 ≦ Z ≦ 0.25, M is V, Mo, N
at least one of b and W, 5 ≦ a ≦ 18 at%, 65 ≦ b ≦ 85 at%, 0 ≦ c
≦ 20 at% 4 ≦ d ≦ 15 at%, 0 ≦ e ≦ 7 at%, 0 ≦ f ≦ 7a
t%, 0 ≦ g ≦ 5 at%, 0 ≦ h ≦ 2 at%). A permanent magnet having good thermal stability and corrosion resistance. 2. In the above composition formula, 10 ≦ a ≦ 15a
The permanent magnet excellent in thermal stability and corrosion resistance according to claim 1, wherein t%, 5 ≦ d ≦ 15 at%, and f ≦ 2 at%. 3. The ratio of Fe and Co is 99.95: 0.0.
The permanent magnet having good thermal stability and good corrosion resistance according to any one of claims 1 to 2, which is in the range of 5 to 77:23. 4. R-rich Nd-Fe-B-Zn-Co
A method for producing a permanent magnet, comprising mixing an alloy powder and an Nd-Fe-B-Nb alloy powder so as to have a composition according to claim 1 and then sintering the mixture.