JPH08288112A - Rare-earth permanent magnet and its manufacture - Google Patents

Abstract

PURPOSE: To improve both the deterioration of the corrosion resistance and the deterioration of the magnetic characteristics by a method wherein the composit composition contents of Ga, C and O2 are specified. CONSTITUTION: The specified weights of metal Na, Fe, Ferro-B and metal Ga are weighed and melted in a vacuum to obtain an ingot. After the ingot is crushed, the crushed ingot is roughly pulverized in an inert gas atmosphere and then finely pulverized to obtain the fine powder. The contents of C and O2 are respectively adjusted during the pulverization so as to obtain high C and high O2 R-M-B (wherein R denotes at least one element among rare-earth elements including Y, and M denotes Fe or Fe and Co) magnet whose contents of C and O2 are 0.02wt.%<=C<=0.2wt.% and O2 >=4000ppm. Further, the content of Ga is 0.02wt.%-1.5wt.%. With this constitution, the R-M-B magnet whose magnetic characteristics deterioration caused by the quantities of C and O2 is suppressed can be obtained.

Description

Detailed Description of the Invention

[0001]

The present invention relates to R (rare earth), M (Fe
Alternatively, the present invention relates to a permanent magnet containing Fe and Co) and B (boron) as main components, and particularly R- which has corrosion resistance and high magnetic characteristics.
The present invention relates to an M-B magnet and its manufacturing method.

[0002]

2. Description of the Related Art R-M-B magnets having a maximum energy product of 40 MGOe or more have been mass-produced due to various improvements in composition and manufacturing method thereof. Among the manufacturing methods, recently, alloy powders of two or more types or alloy powders of different compositions have been used to improve the characteristics from the so-called single method in which alloys of one conventional composition are crushed, molded, sintered and heat-treated. A method (blending method) for producing a high-performance R-M-B magnet by blending, sintering, and heat treatment is proposed.

[0003]

However, it is very difficult for this blending method to satisfy both the corrosion resistance and magnetic characteristics of the R-M-B magnet. That is, RM-
The structure of the B magnet is a state in which a R-rich phase, a B-rich phase and the like are mixed in a matrix phase mainly composed of R ₂ Fe ₁₄ B,
In the single method, a part of this R-rich phase is dispersed within the matrix grains and near the grain boundaries. In the blending method, alloys having different weight ratios of total rare earths are blended to obtain R-
In order to obtain an M-B magnet, especially in the R rich phase, V, Ti,
By consolidating elements such as Mo, W, Al and Nb,
In addition, it is common to control the structure and composition of the precipitation phase that reduces the R-rich phase in the matrix and segregates the R-rich phase near the grain boundaries. In that case, the degree of segregation of the R-rich phase in the vicinity of the grain boundaries is more remarkable than in the single method. On the other hand, in general, the R-rich phase has a particularly high concentration of rare earth elements (particularly Nd),
It is known that the Nd-rich phase is poor in corrosion resistance.
Further, C and O ₂ tend to segregate in this R-rich phase, and R-carbite, R oxides, etc. are generated, and when there are a large amount of these, the magnetic characteristics deteriorate (especially coercive force iHc). The present invention is a novel manufacturing method for improving both of the conventional drawbacks such as deterioration of corrosion resistance due to segregation of R-rich phase and deterioration of magnetic properties due to generation of carbide or oxide in the R-rich phase, and a method thereof. R-M-B obtained by
It provides a magnet. This method and the effects obtained by this method also apply to the single method.

[0004]

In order to solve the problems associated with the segregation of the R-rich phase, the present inventor has improved the conventional magnet composition and structure for corrosion resistance deterioration and magnetic property deterioration to improve the excellent corrosion resistance and magnetic properties. We have found a magnet with high characteristics. Gist of the present invention is to prevent deterioration of magnetic properties due to segregation of the R-rich phase Ga, C, to the complex structure of the O ₂ is corrosion resistance improvement and C R-rich phase, to O ₂ of the R-rich phase Found out.
In particular, the addition of Ga is effective when the amount of C or O ₂ is large. Further, when two or more kinds of alloy powders having different total rare earth elements are blended to produce an R-Fe-B magnet having a predetermined composition, the alloy powder containing a large amount of the total rare earth element in a large amount by weight contains C and O _2. A large amount of Ga, C and O ₂ brings an effective effect.

The present invention will be described in detail below. The present invention has a weight percentage of 0.02% ≦ C ≦ 0.2% and O ₂ ≧ 4.
R-M-B magnet with high C and high O ₂ content (R
Is at least one rare earth element including Y, M is Fe
In Fe and Co), Ga is 0.02% to 1.
R-M-B magnet containing 5%. The reason for limiting Ga is that when Ga <0.02%, there is no effect of improving the magnetic characteristics,
This is because even if Ga> 1.5% is added, the degree of improvement of iHc does not change and it is expensive, so it is not a good idea. Further, in the above magnet, Ga, C and O ₂ are segregated in the R rich phase and its periphery. Further, Ga, C, O ₂ and heavy rare earth elements and one or more elements selected from V, Ti, Mo, W, Al and Nb may be segregated in the R-rich phase and its periphery. Next, in the method for manufacturing a rare earth permanent magnet in which powders having different compositions are mixed and sintered, the total rare earth ratio (hereinafter, referred to as T
When an R-M-B magnet having a predetermined TRE% is manufactured by mixing an alloy having a low RE% with an alloy having a high TRE%, an alloy having a high TRE% (hereinafter referred to as a high R alloy). ) C
The amount of O ₂ and the amount of O ₂ are higher than those of alloys having a low TRE% (hereinafter referred to as low R alloys), which is an R-M-B magnet produced by this manufacturing method. When Ga is added to a high R alloy in the above method, the effect is remarkably improved, and according to the present invention, a high performance R-M-B excellent in corrosion resistance is obtained.
The magnet develops.

[0006]

EXAMPLES The embodiments of the present invention will be described below with reference to examples, but the present invention is not limited thereto. (Example 1, Comparative Examples 1, 2, 3) Metal Nd, Dy, F
A predetermined weight of e, ferro-B, ferro-Nd, and metallic Ga was weighed and vacuum-melted to prepare an ingot having a weight of 10 kg. After crushing this ingot with a hammer, it was further crushed in an inert gas atmosphere using a crusher to obtain a coarse powder having a particle size of 500 μm or less. Next, this coarse powder was finely pulverized in an inert atmosphere using a jet mill to obtain fine powder. The amounts of C and O ₂ were adjusted during grinding. The average particle size of this fine powder is 4.0 μm (FSS.
S). Next, this fine powder is applied with an orientation magnetic field strength of 15 KOe,
Press molding was carried out in a transverse magnetic field under a molding pressure of 1.5 Ton / cm ² to prepare a molded body of 30 mm × 20 mm × 15 mm. This compact was sintered at 1100 ° C. × 3 Hr under a substantially vacuum condition, and the obtained sintered body was subjected to a first sintering at 900 ° C. × 2 Hr.
A second heat treatment was then performed, followed by a second heat treatment at 580 ° C. × 2 Hr. The density of the obtained sintered body was 7.58 g / cm ³ . Table 1 shows the compositions of Example 1 and Comparative Examples 1, 2, and 3, and the measurement results of iHc. % In the table is% by weight, and the impurity level of C is 0.01% or less. In Table 1, Example 1 and Comparative Example 3 contained 0.2% by weight of metallic Ga, and Comparative Examples 1 and 2 did not. From Table 1, it can be seen from the conventional example that if Ga is not added as in Comparative Example 2, C
IHc (coercive force) is low when the amount of oxygen and the amount of O ₂ are high. Also, G
When a is added, iHc is improved when the amounts of C and O ₂ are low as in Comparative Example 3. On the other hand, in Example 1, C content and O
By adding Ga even though the amount of ₂ is high, i
Hc is high. That is, 0.02% ≦ C ≦ 0.2%, O ₂ ≧
Addition of Ga to an R-M-B magnet having a high C and high O ₂ amount of 4000 ppm improves iHc and is effective in improving magnetic characteristics.

[0007]

[Table 1]

Next, Table 2 shows the corrosion resistance evaluation results of the samples of Example 1 and Comparative Examples 1 to 3. The corrosion resistance was evaluated by the pressure cooker test method (120 ° C. × 2 atm × 100% relative humidity). In the table, ○ indicates durability at each time, ×
The mark indicates no durability. From Table 2, the amounts of C and O ₂ are high and Ga
Only Example 1 in which was added exhibited a durability of 500 Hr or more. Even if Ga is added as in Comparative Example 3, the amount of C, O ₂
Corrosion resistance of a low amount is as short as 100 hours. Therefore, from the viewpoints of both magnetic properties and corrosion resistance, it was found that the effect of Ga is remarkable when the amounts of C and O ₂ are high.

[0009]

[Table 2]

(Example 2, Comparative Example 4) As shown in Table 3, R alloys having the same weight% were weighed so as to have the compositions of Example 2 and Comparative Example 4, respectively, and separate ingots were prepared. Grinding was carried out in the same manner as in Example 1, and alloy A and alloy B were mixed so that the final composition shown in Table 3 was obtained.
IHc was measured by performing molding, sintering, and heat treatment in the same manner as in. IHc of Example 2 was 17.0 KOe, and Comparative Example 4
Had an iHc of 14.8 KOe.

[0011]

[Table 3] As can be seen from Table 3, R of the same weight% with high C content and O ₂ content
In a mixing method of mixing alloys to form an alloy having a high C content and a high O ₂ content in the composition after blending, Ga is Dy, Al, N
It can be seen that inclusion in an alloy having a so-called iHc improving element such as b leads to improvement in magnetic characteristics.
When Example 1 and Example 2 are compared, Example 2 produced by the single method has the same improvement in magnetic characteristics as Example 2 in which the same weight% of the R alloy is blended.

The EPMA line analysis results of Example 2 are shown in FIG. Ga, C, and O ₂ are segregated in the R-rich phase,
It is considered that obtaining a composite structure of R—Ga—C—O _{2 in} the rich phase will lead to improved characteristics.

(Examples 3, 4, 5, Comparative Examples 5, 6, 7,
8) As shown in Tables 4 and 5, the low R alloy and the high R alloy were weighed so as to have the compositions of Examples 3 and 4 and Comparative Examples 5 and 6, respectively, and separate ingots were prepared. Pulverization is performed in the same manner as in (1), and low R is obtained so that the final composition shown in Tables 4 and 5 is obtained.
The alloy and the high R alloy were mixed, molded, sintered and heat-treated in the same manner as in Example 1, and the magnetic characteristics (iHc) were measured.
The R content of the final composition after mixing is the same, but in Examples 3, 4
The R content of the high R alloys of Comparative Examples 5 and 6 is higher than that of Example 2.
In Examples 3 and 4, Ga is contained in the high R alloy.
Is low R alloy and high R alloy has high C content and O ₂ content,
C of Example 4 low R alloys, O ₂ amount is low, C of the high R alloys, O ₂ amount is high. On the other hand, Comparative Example 5 uses Ga as a low R alloy.
Is included in both the high R alloy and the low R alloy, and the amounts of C and O ₂ are high. In Comparative Example 6, both the low R alloy and the high R alloy do not contain Ga, and the amounts of C and O ₂ are both high. . The measurement result of iHc in each of Examples 3 and 4 and Comparative Examples 5 and 6 is 1 in Example 3.
7.1 KOe, Example 4 was 18.2 KOe, Comparative Example 5 was 15.5 KOe, and Comparative Example 6 was 14.8 KOe.
Comparing Example 3 with Comparative Examples 5 and 6, C after blending
It can be seen that Ga addition is effective for improving iHc when the amounts of O ₂ and O ₂ are high at the same level, but the result of Ga addition is particularly effective for improving magnetic properties when entering a high R alloy. In Example 4, in particular C of the low R alloys, if the amount of O ₂ is less than the high R alloys, the high R alloys C and the amount of O ₂ is high iHc by Ga enters in the high R alloys in the level of Is further improved as compared with the third embodiment. That is, it was confirmed that the effect of Ga is exerted particularly in the case of the blending method in which the low R alloy and the high R alloy are combined, especially when the amount of C or O _{2 in the} high R alloy is high.

[0014]

[Table 4]

[0015]

[Table 5]

Next, the samples of Examples 3, 4, 5 and Comparative Examples 5, 6 were evaluated for corrosion resistance together with Comparative Examples 7, 8. Corrosion resistance is pressure cooker test method (120 ℃ × 2 × 100
% Relative humidity). Example 5 and Comparative Examples 7 and 8 were manufactured in the same manner as in Examples 3 and 4. The composition is shown in Tables 4 and 5
Shown in In Example 5 and Comparative Examples 7 and 8, Ga is not contained in the low R alloy or the high R alloy. Example 5 is a low R alloy C,
The amount of O ₂ is low, and the amount of C and O _{2 in the} high R alloy is high. In Comparative Example 7, both the low R alloy and the high R alloy have low amounts of C and O ₂ , and Comparative Example 8
The low R alloys C, O ₂ amount is high, the high R alloys C, O ₂ amount is low. The results are shown in Table 6. In Table 6, ◯ indicates durability and x indicates no durability.

[0017]

[Table 6]

From the above results, the C content after blending and O ₂
It has been found that, regardless of the amount, Ga can be dramatically improved in corrosion resistance by adding Ga to a high R alloy when the amount of C and O ₂ in the high R alloy is high. Further than this, such as a series of test results, C amount after the blend even in the absence of addition of Ga from a comparison Comparative Examples 7 and 8 Example 5, regardless of the amount of O _2, the high R alloys C,
O ₂ amount, the low R alloys C, and to exhibit good corrosion resistance is higher than the amount of O ₂ was found together.

[0019]

EFFECTS OF THE INVENTION According to the present invention, R-M which suppresses the deterioration of magnetic characteristics due to the amount of C and O ₂ by introducing Ga into the R-rich phase.
It is possible to obtain a -B magnet, which brings about an effect that has not been obtained in the past, especially when the amounts of C and O ₂ are large. Also, G
C amount when even high R alloys and the low R alloys and the high R alloy when combined in a non-additive, the amount of C O ₂ amount low R alloy, after blending by higher than the amount of O ₂ C The corrosion resistance can be improved regardless of the amount and the amount of O ₂ . Further, by increasing the C and O ₂ amounts of Ga-essential high R alloys than those of the low R alloys and mixing, the C content and O ₂ after blending
IHc can be improved regardless of the amount, and its utility value is extremely high in industry.

[Brief description of drawings]

FIG. 1 is an EPMA line analysis result of Example 2.

[Explanation of symbols]

 None

Claims (11)

[Claims] 1. A weight percentage of 0.02% ≦ C ≦ 0.2.
%, O ₂ ≧ 4000 ppm R-M-B magnet (R is Y
0.02% to 1.5% of Ga in at least one or more rare earth elements including M, Fe or Fe and Co)
An R-M-B magnet containing: 2. A weight percentage of 0.02% ≦ C ≦ 0.2.
%, O ₂ ≧ 4000 ppm R-M-B magnet (R is Y
In at least one or more rare earth elements including M, Fe is Fe or Fe and Co), and Ga, C, and O ₂ are segregated in the R-rich phase and its periphery.
-B magnet. 3. A weight percentage of 0.02% ≦ C ≦ 0.2.
%, O ₂ ≧ 4000 ppm R-M-B magnet (R is Y
At least one or more rare earth elements including M, Fe is Fe or Fe and Co), and Ga, C and O ₂ and one or more elements selected from heavy rare earth elements and V, Ti, Mo, W, Al and Nb. An R-M-B magnet characterized by being segregated in the R-rich phase and its surroundings. 4. The weight ratio of the total rare earth elements is approximately the same (± 1
%) Alloy powder to have a predetermined weight ratio of total rare earth elements (R is at least one or more rare earth elements including Y, M is Fe or Fe and Co). Ga is essential for one alloy powder, Al,
A method for manufacturing an R-M-B magnet, which comprises one or more of Ti, Nb, and Mo. 5. The R-M-B produced by the method of claim 4.
magnet. 6. The weight ratio of the total rare earth elements is approximately the same (± 1
%) Alloy powder to have a predetermined weight ratio of total rare earth elements (R is at least one or more rare earth elements including Y, M is Fe or Fe and Co). Ga, Al, Ti, N in one alloy powder
b, R containing at least one of Mo
-M-B magnet manufacturing method. 7. An R-M-B produced by the method of claim 6.
magnet. 8. An R—M—B magnet having a predetermined weight ratio of total rare earth elements (R is a mixture of alloy powder having a low weight ratio of total rare earth elements and alloy powder having a high weight ratio of total rare earth elements). In the method for producing at least one or more rare earth elements including Y, M is Fe or Fe and Co), the alloy powder having a low weight ratio of the total rare earth elements in the C content and the O ₂ content of the alloy powder having a high weight ratio of the total rare earth elements. A method for producing an R-M-B magnet, which is higher than those of powder. 9. An R-M-B produced by the method of claim 8.
magnet. 10. The RM in which Ga is essential in an alloy powder having a high weight ratio of total rare earth elements in the manufacturing method according to claim 8.
-B magnet. 11. An RM produced by the method of claim 10.
-B magnet.