JP2004134552A - High coercive force anisotropic magnet and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve heat-proof characteristic by improving the coercive force of the HDDR powder and also improving the limit of the temperature of the magnet for the magnet powder using the HDDR method. <P>SOLUTION: The HDDR powder and a rare earth oxide are mixed and are then subsequently subjected to a heat treatment. The HDDR powder and Dy203 sample A have been manufactured by the heat treatment for 0.5 hour under the Ar flow of the powder mixing the Dy203 powder of 5wt% for the HDDR powder which has been obtained by conducting, at 850°C, the H2 flow and pressure reduction process to the mother alloy in the composition of Nd=12.6, Fe=63.1, Co=17.4, B=6.5, Zr= 0.1, Ga= 0.3. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a high coercive force anisotropic magnet for the purpose of increasing the coercive force of a Nd—Fe—B-based magnet material.
[0002]
[Prior art]
Conventionally, an NDR-Fe-B alloy is subjected to a hydrogen absorption / dehydrogenation treatment to reduce the crystal grain size and develop an HDDR method that expresses a coercive force. Has been realized. This HDDR powder is an Nd-Fe-B-based magnet powder exhibiting anisotropy, and by utilizing this feature, it is possible to improve the performance of the magnet, especially for a bonded magnet.
In the HDDR method, a mother alloy having a Nd ₂ Fe ₁₄ B phase is made to absorb hydrogen at about 850 ° C.
Nd ₂ Fe ₁₄ B → NdH ₂ + α-Fe + Fe ₂ B
Phase decomposition occurs, and then is forcibly dehydrogenated in a vacuum,
NdH ₂ + α-Fe + Fe ₂ B → Nd ₂ Fe ₁₄ B
The recombination is caused to produce a coercive force based on the refinement of the Nd ₂ Fe ₁₄ B phase crystal.
[0003]
On the other hand, to increase the coercive force of the Nd—Fe—B based magnet, a Dy ₂ Fe ₁₄ B compound is generated by substituting a part of the magnet with Dy, and the huge crystal magnetic anisotropy of the Dy ₂ Fe ₁₄ B compound is reduced. A high coercive force material has been developed using the same (see Non-Patent Document 1). This method has been applied to various Nd-Fe-B-based magnet materials, and is particularly effective for sintered magnets.
[0004]
Also, a technique for increasing the coercive force by heat treatment of a mixture of HDDR powder and DyH2 has been developed (see Non-Patent Document 2).
[0005]
[Non-patent document 1]
J. Magn. Magn. Mater. , 61, (1986), 363-369.
[0006]
[Non-patent document 2]
Proc. 16 ^th Int. Workshop REM and their applications, pp. 813-819.
[0007]
[Problems to be solved by the invention]
However, when the technique of substituting a part of the Nd—Fe—B-based magnet described in Non-Patent Document 1 with Dy and generating a Dy ₂ Fe ₁₄ B compound is applied to the HDDR powder having anisotropy, Dy ₂ Since the Fe ₁₄ B phase has low reactivity with hydrogen and hinders the hydrogen absorption decomposition and dehydrogenation recombination reactions, which are the processes of the HDDR method, a Dy-containing Nd-Fe-B-based fine crystal having high coercive force is formed. It was difficult to produce and obtain a high coercive force.
[0008]
In addition, the heat treatment of the mixture of HDDR powder and DyH2 described in Non-Patent Document 2 has a problem that only a slight increase in coercive force can be obtained.
[0009]
In view of the above-mentioned problems, an object of the present invention is to improve the coercive force of the HDDR powder with respect to the magnet powder using the HDDR method, to improve the limit of the operating temperature of the magnet, and to improve the heat resistance. And
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the above-mentioned problem has been solved by mixing HDDR powder and a rare earth oxide and then performing a heat treatment.
[0011]
【The invention's effect】
In the invention of the present application, the coercive force of the HDDR powder did not significantly increase because the rare-earth substitution could not be freely performed, but a rare-earth oxide was mixed and heat treatment was performed. , The coercive force can be dramatically increased. Further, the operating temperature range of the high coercive force anisotropic magnet using this powder can be shifted to a higher temperature, and the industrial application range can be greatly expanded.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a method for producing a high coercive force anisotropic magnet according to the present invention will be described based on examples, but the present invention is not limited to the examples.
[0013]
(Example 1)
HDDR obtained by subjecting Nd _12.6 Fe _63.1 Co _17.4 B _6.5 Zr _0.1 Ga _0.3 composition mother alloy to depressurization treatment at 850 ° C. by an H ₂ flow and a rotary pump. Powder mixed with 5 wt% of Dy ₂ O ₃ powder was heat-treated in an Ar flow for 0.5 hour to prepare HDDR powder + Dy ₂ O ₃ sample A. FIG. 1 shows a change in coercive force HcJ of Sample A and Sample B of HDDR powder alone depending on the heat treatment temperature.
[0014]
No improvement in coercive force HcJ is observed in Sample B containing only the HDDR powder, but it can be seen that Sample A, which is a powder mixed with Dy ₂ O ₃ , shows a remarkable increase in the temperature range of 600 ° C. to 900 ° C. ( Claims 1 and 2). The Jr / Js value as an index indicating the anisotropy of each sample was almost constant in each sample, and no deterioration of the anisotropy was observed with the increase of the coercive force.
[0015]
(Example 2)
Nd _{1 c .} HDDR powder obtained by subjecting ₆ Fe _63.1 Co _17.4 B _6.5 Zr _0.1 Ga _0.3 composition mother alloy to H ₂ flow and depressurizing treatment by a rotary pump at 850 ° C. The powder mixed with 10 wt% of Dy ₂ O ₃ powder was subjected to a heat treatment at 800 ° C. in an Ar flow to prepare a sample C which was (HDDR powder + Dy ₂ O ₃ ). FIG. 2 shows a change in coercive force HcJ of Sample C with heat treatment time.
[0016]
The coercive time shows a good coercive force of 10 kOe or more in 1 hour or less. It is considered that when the processing time is 1 hour or longer, the coercive force is significantly reduced due to crystal growth of fine crystal grains of about 300 nm which originally have the coercive force of the HDDR powder. Corresponding to).
[0017]
(Example 3)
HDDR obtained by subjecting Nd _12.6 Fe _63.1 Co _17.4 B _6.5 Zr _0.1 Ga _0.3 composition mother alloy to depressurization treatment at 850 ° C. by an H ₂ flow and a rotary pump. Sample D was prepared by heat-treating the powder obtained by changing the mixing ratio of the powder and Dy ₂ O ₃ powder in an Ar flow at 800 ° C. for 0.3 hours. FIG. 3 shows a change in coercive force HcJ of Sample D depending on the amount of Dy ₂ O ₃ powder mixed.
[0018]
It can be seen that when the amount of Dy ₂ O ₃ mixed is 1 wt% or more, a remarkable increase is exhibited. Since the residual magnetic flux density Br tends to decrease with an increase in the amount of Dy ₂ O ₃ mixed, the upper limit is practically about 10 wt% (corresponding to claim 3). Further, in any of the samples this time, similarly to Example 1, no change was observed in the anisotropy of the HDDR powder with the increase in the coercive force.
[0019]
(Operation of each embodiment)
Regarding the action of the HDDR powder exhibiting a high coercive force in each of the above-mentioned embodiments, no clear reason has been found at present, but the following action is presumed. That is, in each of the above embodiments, the coercive force is improved by performing the heat treatment on the mixture of the HDDR powder and the Dy oxide. Here, when the bonding force of the oxide with oxygen is small, Nd in the magnet powder takes oxygen and is easily oxidized, so that the coercive force is expected to deteriorate. Therefore, it is considered that the oxide mixed with the magnet powder in each of the above embodiments needs to be a stable substance in bonding with oxygen. Although the Dy oxide is used in each of the above-described embodiments, any one or more of Tb and Ho may be used. In addition, Dy or Tb or Ho ions in the oxide to be applied are appropriately dissociated by heat treatment and react with the Nd element in the HDDR magnet, and as a result, the outermost surface of the HDDR magnet powder forms a magnet compound and a crystal structure. It is presumed that a coherent Dy or Tb or Ho oxide layer is formed, thereby improving the coercive force of the magnet powder.
[0020]
In the heat treatment, it is effective to suppress excessive oxidation of the magnet powder by heating in a vacuum or in an inert gas atmosphere (corresponding to claim 4). Heat treatment in an oxygen-containing atmosphere oxidizes most of the magnet powder, so that magnet properties are not exhibited.
[0021]
The effective temperature range for the heat treatment is 600 to 900 ° C., but the reason is not clear. However, when the temperature is lower than 600 ° C., the formation of the matching layer on the outermost surface of the magnet compound is insufficient. On the other hand, when the temperature is 900 ° C. or higher, fine crystal grains of about 300 nm, which originally have a coercive force of the HDDR powder, are used. The remarkable decrease in coercive force due to the crystal growth of the (corresponding to claim 5).
[0022]
When assuming a working described above, rather than the increase of the small coercivity found in heat treatment of the mixture of HDDR powder and DyH ₂ as reported in Non-Patent Document 2, the HDDR powder and Dy or Tb or Ho It is considered that a remarkable increase in coercive force can be recognized by mixing with any one or more kinds of oxides and subsequently performing heat treatment.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a change in coercive force according to a heat treatment temperature in Example 1.
FIG. 2 is a diagram illustrating a change in coercive force with a change in heat treatment time in Example 2.
FIG. 3 is a diagram illustrating a change in coercive force with a change in a Dy ₂ O ₃ mixture amount in Example 3.
[Explanation of symbols]
A sample (HDDR powder + Dy ₂ O ₃ )
B sample (HDDR powder only)
C sample (HDDR powder + Dy ₂ O ₃ )
D sample (HDDR powder + Dy ₂ O ₃ )

Claims (6)

The method is characterized in that the HDDR powder obtained is mixed with a rare earth oxide using an HDDR method for making crystal grains fine by utilizing a hydrogen absorption / desorption reaction to an Nd—Fe—B alloy, followed by heat treatment. A method for producing a high coercivity anisotropic magnet. The method according to claim 1, wherein the rare earth oxide is a rare earth oxide containing at least one kind of Dy, Tb, and Ho. 3. The method of claim 1, wherein a content of the rare earth oxide is 1 to 10 wt% based on a total amount of the HDDR powder and the rare earth oxide. 4. . 4. The heat treatment according to claim 1, wherein the mixed powder of the HDDR powder and the rare earth oxide or the compact of the mixed powder is heated in a vacuum or in an inert gas atmosphere. A method for producing a high coercivity anisotropic magnet according to one of the above aspects. The high coercive anisotropy according to any one of claims 1 to 4, wherein the heat treatment is performed at a heat treatment temperature of 600C to 900C and a coercive time of 0.01 minute to 1 hour. Manufacturing method of magnet. A high coercive force anisotropic magnet manufactured using the method for manufacturing a high coercive force anisotropic magnet according to any one of claims 1 to 5.

Images