JP3410171B2 - Method for producing rare earth magnet powder and anisotropic bonded magnet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is a rare earth, transition metals and anisotropic rare earth magnet powder consisting essentially of <br/> boron, list
The present invention relates to improvement of a method for manufacturing an anisotropic bonded magnet.

[0002]

2. Description of the Related Art R-T-B system permanent magnets ( R is a rare magnet containing Y)
At least one of the earth elements, T is Fe or Fe
And a Co) have attracted attention as having magnetic properties inexpensive yet high. RTB permanent magnets are roughly classified into bulk magnets (sintered magnets or warm-worked magnets) and bonded magnets according to the classification of the final product. Bond magnets are expected to increase in importance in the future due to their shape flexibility and price advantages. Magnetic powders for Nd-Fe-B based bonded magnets are classified into several types depending on the manufacturing method. For example, an Nd-Fe-B-based quenched thin piece obtained by the melt spinning method
Heat treatment at an appropriate temperature, a manufacturing method for an isotropic magnet powder is disclosed in JP-A-59-647393. The flakes obtained in the same melt spinning process Hoyo hot press
Fine die chipset anisotropic bulk magnet imparted with anisotropy in the compression direction once prepared, then it is also known manufacturing method of an anisotropic magnet powder by grinding the magnet. In addition, as a method that has been receiving attention in recent years, Sm ₂ F
anisotropic magnetic field by entering the nitrogen element interstitially subjected to nitriding treatment e ₁₇ alloy is remarkably improved, there is a method that can be used as a result the magnetic powder for an anisotropic bonded magnet. In addition, NbFe ₁₁ Ti, N
It has been reported that a similar effect can be obtained with a ThMn ₁₂ type alloy such as dFe ₁₀ V ₂ . Furthermore, Nd-F
e-B alloy is subjected to hydrogen storage treatment and dehydrogenation treatment,
Magnetically anisotropic Nd ₂ Fe using recrystallization reaction
_A method for obtaining ₁₄ B type magnetic powder is known (Japanese Patent Application Laid-Open No. 1-132).
106 gazette , JP-A-2-4901 gazette, etc.).

[0003]

Among the magnetic powders obtained by the conventional method, the Nd-Fe-B system quenched flakes prepared by the melt spinning method are magnetically isotropic and the finally obtained bond magnet is obtained.
The maximum energy record of stone is only 10 MGOe at most, and there is a problem in terms of magnetic properties. Further, the conventional Nd-Fe-B system anisotropy
Anisotropic bonded magnet magnetic powder ing blended with the magnetic properties sufficiently
Instead, there was room for improvement . On the other hand, Sm ₂ Fe
_{Since 17-} type nitride magnetic powder uses Sm as a main raw material, there is concern about its future prospects in terms of resources. ThMn ₁₂ type magnetic powder is resource advantageous because the rare earth element is Nd to use
But magnetic potential after the nitriding is _Nd 2 _{Fe 14} B type Ah <br/> Rui have lower than _Sm 2 _{Fe 17} type. The Nd-Fe-B type anisotropic magnetic powder obtained by performing the hydrogen storage treatment and the dehydrogenation treatment has a feature that the manufacturing process can be considerably simplified, but the Nd-Fe-B type bulk magnet is used. Tei Ru magnetic characteristics obtained at present by estimated from the theoretical value of the leaves much to be desired. This manufacturing method utilizes a recrystallization reaction accompanied with a phase transformation in the dehydrogenation treatment step, and finally obtains N
It is considered that the magnetic characteristics of the d-Fe-B anisotropic magnetic powder largely depend on this reaction rate. That is, even if the forced dehydrogenation is performed blindly, the phase transformation does not proceed, and the phases before the phase transformation, that is, NdH ₂ , α-T, and Fe ₂ B remain as they are or part of them are ideal R ₂ T ₁₄ B Since no phase is obtained, the finally obtained magnetic properties are low.

[0004]

The inventors of the present invention have found that the ideal N
To obtain a d-Fe-B based anisotropic magnetic powder, phase transformation kinetics
By controlling the (recrystallization reaction rate) by the degree of vacuum in the dehydrogenation process , magnetic anisotropy is excellent and flat.
Average crystal grain size real of fine crystal grains of an aggregate of 0.02~5μm
Nd- which is qualitative and has higher magnetic characteristics than the conventional one
It was found that an Fe-B anisotropic magnetic powder can be obtained . the above
The method for producing a rare earth magnet powder of the present invention which has solved the problem is
R ₂ T ₁₄ B phase with an average crystal grain size of 0.02 to 5 μm (where R is Y
At least one of rare earth elements including T is Fe or
Is an aggregate of fine crystal grains whose main phase is Fe and Co)
In the method for producing a rare earth magnet powder consisting essentially of
Hydrogen storage and dehydrogenation processes are performed to cause a recrystallization reaction.
Degree of vacuum in the dehydrogenation process among the manufacturing processes
When (Torr) is y and dehydrogenation treatment time (seconds) is x,
Within the range of x = 60 to 1000 seconds, y = Ax ^z (only
The condition of the exponential function represented by -0.70≤z≤-0.30)
It is characterized in that the dehydrogenation treatment is performed by . The method for producing an anisotropic bonded magnet according to the present invention has an average crystal grain size of 0.02 to 5
μm R ₂ T ₁₄ B phase (R is a rare earth element containing Y
And T is Fe or Fe and Co).
Rare earths consisting essentially of aggregates of fine grains as the main phase
Anisotropic bonded magnet made by binding magnet powder with binder
In the manufacturing method of, hydrogen storage treatment and dehydrogenation treatment
Dehydrogenation treatment is one of the manufacturing processes that cause recrystallization reaction.
Dehydration treatment time, where y is the degree of vacuum (Torr) in the process
When (sec) is x, in the range of x = 60 to 1000 seconds
y = Ax ^z (where -0.70 ≦ z ≦ −0.30)
Rare earth magnets dehydrogenated under controlled exponential function
Specializing in molding a mixture of powder and binder in a magnetic field
To collect. The rare earth magnet powder has an R content of 25 to 35 wt%,
0.5 to 1.5 wt% B, 3 to 20 wt% Co, Ga, Z
selected from the group of r, Nb, Hf, Ta, Al, Si and V
0.05-5 wt% in total of at least one selected ,
Also it has with balance of Fe and improper wall impurities
Is preferred . This rare earth magnet powder absorbs hydrogen in the mother alloy
And NdH ₂ , α-T, Fe ₂ after treatment and dehydrogenation treatment
A recrystallization reaction accompanied by a phase transformation in the dehydrogenation process, which changes the three phases of B into fine crystal grains of the R ₂ T ₁₄ B phase.
A shall be obtained by the response, having magnetic anisotropy.

The present inventors considered that the phase transformation rate during dehydrogenation treatment affects the degree of magnetic anisotropy and repeated the experiment under various dehydrogenation treatment conditions. As a result, the dehydrogenation step was found that there is a certain regularity. That it is made of primary dehydrogenation step <br/> and subsequent secondary dehydrogenation process between dehydrogenation start after about 60 to 1000 seconds.
In particular, it was found that the magnetic anisotropy potential that influences the magnetic properties is determined by the primary dehydrogenation treatment rate. After secondary dehydrogenated primary dehydrogenation process ends, a dehydrogenation process for releasing excess hydrogen remaining interstitial, No
Although it is evasive, it does not have such a large influence as to decisively influence the magnetic characteristics. Degree of vacuum in primary dehydrogenation (Torr)
Is y and the dehydrogenation treatment time (sec) is x , x = 60 to 10
Within the range of 00 seconds , it can be approximated to a straight line on a logarithmic graph.
It is expressed by a numerical function of y = Ax ^z (where, −0.70 ≦ z ≦ −0.30), and it was found that the degree of vacuum sharply increases in the secondary dehydrogenation treatment . Here, since the reason for limiting the value of x containing dehydrogenation for x is to degas the furnace hydrogen atmosphere other than the sample in 60 seconds or less, phase transformation equilibrium for the net R ₂ T ₁₄ B phase generator Because it is not in a state. Upper limit of 1000
This is because the second varies slightly depending on the mass of the sample and the performance of the apparatus, but within this range is an approximate guideline for the primary dehydrogenation treatment . When a z value to adjust the amount of processing or the pump capacity at dehydrogenation of the sample was intentionally varied, z values magnetization amount and the coercive force is less than -0.70 showed a very low value. This phenomenon will be described in detail. Since the primary dehydrogenation treatment is performed at a high speed, the nucleation directions necessary for recrystallization and growth occur in random directions, and the growth occurs in that state, so that it becomes magnetically isotropic. Furthermore, since the equilibrium state of the reaction is disrupted, each phase decomposed during hydrogen absorption is left as it is, or a part thereof remains to reduce the substantial amount of R ₂ T ₁₄ B phase produced. Thus addition coercivity in finally obtained the magnet powder to hydrogen a large amount of residual, magnetic properties such as magnetization amount ing to decrease. On the other hand, when the z value exceeds -0.30, the phase transformation proceeds, but it takes a long time to reach the final target vacuum degree (for example, about 0.1 Torr) for releasing excess hydrogen, and the recrystallized grains are coarse. As a result, the coercive force is reduced.
Therefore, by setting the dehydrogenation rate to a velocity gradient within the range of −0.70 ≦ z ≦ −0.30, the phase transformation also proceeds at an appropriate rate, so that it is possible to obtain a rare earth magnet powder having high magnetic properties.

Since the rare earth magnet powder according to the present invention has a magnetically high degree of anisotropy, it is bonded with a binder ,
Then high performance anisotropic bonded magnet by molding in a magnetic field is Ru obtained. Controlling the dehydrogenation rate is not very difficult. For example, if the volume inside the furnace and the exhaust capacity of the rotary pump are fixed, the throughput of the sample may be adjusted.If this condition is not applicable, a procedure such as installing a pressure controller in the pipe connecting the inside of the furnace and the rotary pump is taken. Can be considered. Further, it suffices that dehydrogenation is performed stepwise by opening and closing the valve, and the average dehydrogenation rate falls within a predetermined range.

[0007]

Example 1 A rare earth element Nd, a transition metal Fe, Co, and boron B as a main component, Ga or Zr as another element were added, and vacuum-melted to a predetermined composition to obtain a cast alloy. Then the same alloy 11
The sample was homogenized at 00 ° C. for 20 hours to prepare a sample for hydrogen treatment. As the heat treatment furnace, a furnace with a fixed volume equipped with a rotary pump having an exhaust capacity of 6401 / min was used.
Hydrogen treatment was carried out under the same conditions by dividing the treatment amount into 6 stages of 1 kg, 2 kg, 3 kg and 10 kg. The hydrotreating conditions, after first be fully occluded at room temperature of hydrogen and heated to 840 ° C. at one atmosphere heating rate of 10 ° C. / min while maintaining the hydrogen atmosphere. Then, after holding at the same temperature for 3 hours, dehydrogenation treatment was performed for 45 minutes. After completion of dehydrogenation, the inside of the furnace was replaced with an argon atmosphere and cooled. For samples with Ga added 1 after dehydrogenation started
The results plotted on the measured log graph 45 min furnace vacuum from the time the minute between elapsed shown in FIG. As shown in the figure, it can be seen that until about 1000 seconds after the start of dehydrogenation, each of them is approximated to a straight line, and thereafter the vacuum degree rapidly increases. This tendency becomes remarkable as the processing amount decreases. Further, the gradient (z value) calculated from this approximate straight line increases as the amount of treatment increases, which means that the dehydrogenation rate becomes slower. The obtained hydrogen-treated sample was pulverized, and then classified to have a particle size of 425 μm or less, and adjusted to have the same particle size distribution . Minute
Mixing the grade powder and epoxy resin, the resulting mixture
By compression molding in a magnetic field to obtain an anisotropic bonded magnet. Table 1 ultimate vacuum after between dehydrogenated 45 minutes, the amount of hydrogen remaining in the sample after hydrogen treatment, z values when expressed by an exponential function of the linear portion of FIG. 1, and the anisotropic bonded magnet It shows magnetic properties. If this z value than the results -0.70 smaller (i.e. fast dehydrogenation rate), ultimate vacuum large amount of residual magnetic characteristics low hydrogen to higher due despite the sample. On the other hand, the amount of residual hydrogen is large even in the sample having a high z value of the treated amount of 10 kg, and the residual magnetic flux density of the anisotropic bonded magnet is high, but the coercive force is low.

[0008]

[Table 1]

Example 2 With respect to the Ga-added material, the treatment amount was set to 1 kg, and the dehydrogenation time was set to 0.
6 seconds, 1000 seconds, 2000 seconds, 2700 seconds, 3500 seconds and 4000 seconds
Except for using phase was <br/> hydrotreated in the same manner the other conditions as in Example 1. The relationship between the dehydrogenation time and the degree of vacuum in the furnace is shown in FIG. Then ground in the same manner as in Example 1, the particle size fraction and classified
An anisotropic bonded magnet was produced using the powder obtained by adjusting the cloth . Table 2 shows the ultimate vacuum, the amount of residual hydrogen, and the magnetic properties of the bonded magnet. From this result, it is found that the magnetic characteristics of the bonded magnet are almost determined by the dehydrogenation time up to about 1000 seconds. Further, dehydrogenation for a long time has the effect of reducing the amount of residual hydrogen and improving the residual magnetic flux density, but causes a significant decrease in coercive force. All plots in Figure 2 are y = 53x
Rukoto and can be expressed at ^-0.50, to confirm the reproducibility.

[0010]

[Table 2]

Example 3 As shown in Table 1 of Example 1 , when the treatment amount was 10 kg, a large amount of hydrogen remained in the sample although the sample had a high residual magnetic flux density. Therefore, an experiment was conducted to reduce the amount of residual hydrogen by increasing the dehydrogenation efficiency using rotary pumps with different exhaust capacities. Rotary pump displacement volume 640L / min using, 900 l / min, 1500 l / min, and 2000 l / minute
There are four types. The experimental conditions except for changing the rotary pump was carried out in the same manner as in Example 1. The relationship between the dehydrogenation time and the degree of vacuum in the furnace is shown in FIG. From the figure, it was confirmed that the vacuum degree was gradually improved and the ultimate vacuum degree after 45 minutes could be improved by increasing the exhaust capacity. Furthermore, after starting dehydrogenation, 10
It can be seen that the z value up to 00 seconds also gradually decreases, and the dehydrogenation rate increases slightly. The results obtained hydrotreated samples to and evaluated in the same manner as in Example 1 shown in Table 3. Shown in Table 3
As described above , by increasing the exhaust capability of the rotary pump, the z value was kept within an appropriate range and the amount of residual hydrogen was reduced, and finally a high-performance anisotropic bonded magnet was obtained .

[0012]

[Table 3]

[0013]

According to the present invention, the dehydrogenation treatment rate can be specified.
By controlling within the range, magnetic characteristics compared to conventional
Nd-Fe-B based anisotropic magnet powder having improved heat resistance and the same
It is possible to provide a high-performance anisotropic bonded magnet using .

[Brief description of drawings]

FIG. 1 is a graph showing an example of the relationship between dehydrogenation treatment time and furnace vacuum degree.

FIG. 2 is a graph showing another example of the relationship between the dehydrogenation processing time and the degree of vacuum in the furnace.

FIG. 3 shows still another relationship between the dehydrogenation processing time and the degree of vacuum in the furnace .
It is a graph which shows an example .

Claims (2)

(57) [Claims] 1. R ₂ T having an average crystal grain size of 0.02 to 5 μm
₁₄ B phase (R is at least one rare earth element including Y)
There, T is the method for producing substantially ing rare-earth magnet powder of fine crystal grains of the aggregate as a main phase is Fe or Fe and Co), recrystallization reactions carried hydrogen absorption treatment and dehydrogenation treatment among occurs causing the manufacturing process, the degree of vacuum in the dehydrogenation step
When (Torr) is y and dehydrogenation treatment time (seconds) is x ,
x = Within 60-1000 seconds y = Ax z ^(however, -0.70 ≦ z ≦ -0.30) preparation of a rare earth magnet powder and performing dehydrogenation treatment under conditions of exponential function you express in Method. 2. R ₂ T having an average crystal grain size of 0.02 to 5 μm
₁₄ B phase (R is at least one rare earth element including Y)
There, T is substantially ing rare-earth magnet powder of fine crystal grains of the aggregate as a main phase is Fe or Fe and Co)
In the production method of the anisotropic bonded magnet ing bound by a binder, in the manufacturing process to cause recrystallization reaction performs hydrogen storage process and a dehydrogenation process, degree of vacuum dehydrogenation treatment step
When (Torr) is y and dehydrogenation treatment time (seconds) is x ,
x = 60-1,000 seconds y = Ax z within the range of ^(where, -0.70 ≦ z ≦ -0.30) between the rare-earth magnet powder subjected to dehydrogenation treatment at under exponential function it expresses in a binder
A method for producing an anisotropic bonded magnet, which comprises molding the mixture in a magnetic field.