JPH07110965B2 - Method for producing alloy powder for resin-bonded permanent magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to R (T, B) (where R is at least one rare earth metal element containing at least Nd, T is Fe or
Fe and Co are shown and are defined in the range of 0.05 ≦ y ≦ 0.10 and 4.5 ≦ z ≦ 6.5. The present invention relates to a method for producing an alloy powder containing a resin as a main component for a resin-bonded permanent magnet.

“Prior art and its problems” In rare earth transition metal alloys, the intermetallic compound having a ratio of rare earth metal to transition metal of 2:17 may theoretically have extremely high magnetic properties [(BH) _max 〜 50MGOe]. Since its discovery, various attempts have been made to obtain a permanent magnet practical alloy mainly composed of a similar compound. As an example, Sm-Co-Cu-Fe
High magnetic properties of (BH) max to 30MGOe have been achieved with the intermetallic compounds and high magnetic properties of (BH) max to 40MGOe have been obtained with the Nd-Fe intermetallic compounds. Alloys of this composition are crushed, oriented compression molded in a magnetic field or compression molded in a non-magnetic field, sintered, solutionized,
Sintered permanent magnets that are aged were common.

However, the sintered permanent magnet has a drawback that the process is complicated, and the final sintered body is brittle compared to other magnet materials and is easily chipped. On the other hand, it is as low as 20-40%, but it has excellent dimensional accuracy, mechanical workability, strength, and magnetic stability, and has the feature that it can be molded into complex shapes.

[Problems to be Solved by the Invention] However, R (T _1-y B _y ) _z (where R represents at least one rare earth metal element containing at least Nd, and T represents Fe or Fe and Co) , 0.05 ≦ y ≦ 0.10, 4.5 ≦ z ≦ 6.5
Stipulated in the range of. In the alloy having the composition represented by the general formula (1), particularly when a rare earth iron-based alloy in which T is Fe is made into a resin-bonded permanent magnet, the composition alloy is 5-100
After finely pulverizing to a particle size of μm, it can be compression molded (Cmpression-mold) or injection molded (In
It is generally formed by jecton-mold),
The magnetic properties of the obtained resin-bonded permanent magnet are
Both the coercive force is significantly reduced, and the squareness of the 4πI-H demagnetization pole wire is greatly deteriorated.

Further, there are a method for producing a raw material powder for a resin-bonded permanent magnet in which a molten metal is rapidly cooled to obtain an amorphous alloy or a powder is obtained by a spraying method, but the particle size is large, and in the composition of z ≧ 6,
There are drawbacks that fine pulverization becomes difficult because the Fe content increases and the pulverization equipment becomes large-scale.

The present invention has been made in view of the above drawbacks of the prior art, and an object thereof is to provide a new technical means capable of greatly improving the coercive force of a resin-bonded permanent magnet.

[Means for Solving Problems] The present invention aims to solve the above-mentioned problems by using R (T _1-y
B _y ) _z (where R represents one or more rare earth metal elements containing at least Nd, and T represents Fe or Fe and
It represents Co and is defined in the range of 0.05 ≦ y ≦ 0.10 and 4.5 ≦ z ≦ 6.5. In the production of alloy powder for resin-bonded permanent magnets having the composition represented by the general formula (1), the molten alloy is roughly pulverized, then finely pulverized by a vibration mill, and the obtained particles are compression-molded to obtain a green compact. After heating the green compact, the sintered compact is sealed in a hydrogen atmosphere to form a hydrogen compound and disintegrate, and then mechanically ground again to 10 to 50
Provided is a method for producing an alloy powder for a resin-bonded permanent magnet, characterized in that particles having a particle diameter of 0 μm are obtained, and the particles are heated to 600 to 1,000 ° C. for dehydrogenation.

That is, the present invention is completely different from the conventional common general knowledge in the case where this powder is used for a resin-bonded permanent magnet by producing an alloy powder of a specific set as described above by a specific method. It was completed based on the new knowledge that the coercive force of a magnet can be greatly improved.

In this alloy composition, y is 0.05 in the above general formula.
Below or z exceeds 6.5, coercive force cannot be obtained and y
Exceeds 0.10 or z is less than 4.5, a decrease in saturation magnetization is induced. The processing steps in the method of the present invention for producing the powder having this unique alloy composition will be described below in outline.

a) Coarse crushing The molten alloy is first roughly crushed.

This coarse pulverization includes mechanical pulverization, hydrogen absorption disintegration pulverization, etc.
Regardless of the pulverizing means, it is the pulverization in the previous stage for forming relatively uniform fine particles for the fine pulverization in the next step. If the particles are too large, the vibration pulverization efficiency in the next step is lowered, the pulverization time becomes long, and distortion is accumulated in the particles, which is a necessary step.

b) Fine pulverization by vibrating mill Fine pulverization is necessary because individual particles are refined to a magnetically preferable size, and this step promotes coarse growth through the next green compact → sintered body, and the final powder is This is for forming particles with uniform directionality.

c) Compression molding Next, compression molding is performed to obtain a green compact. This is to obtain the final alloy powder having the largest possible grain size in which the grains adjacent to each other sinter when being heated in the next step and undergo coarse growth and are magnetically aligned in direction.

d) Formation of Sintered Body The formation of the sintered body causes the hot rough growth of adjacent particles.
The purpose is not to form a 100% dense sintered magnet, but to form the original shape of the final alloy powder that is magnetically oriented through hot grain growth.

e) Hydrogen compound disintegration and mechanical crushing The disintegration effect of the hydrogen compound is utilized in order to make the particle sintered body, which has once grown into particles and has magnetically uniform directionality, into the final powder without destroying its structure. Especially for NdFeB magnets, mechanical stress deteriorates the magnetic properties, so it is performed before mechanical grinding.

It is necessary that the final particle size is as large as possible within the range where the final alloy powder does not oxidize.

Regarding the particle size condition, particles having a particle size of 10 to 500 μm are obtained by disintegration due to hydrogen compound formation and subsequent mechanical crushing.

In this case, the particle size range of 10-500 μm is 10
If it is less than μm, it is easily oxidized, and if it exceeds 500 μm, the orientation is deteriorated.

f) Thermal dehydrogenation The thermal dehydrogenation treatment mainly releases hydrogen absorbed as a hydrogen compound, and sets temperature conditions in which particles are not fixed again. In the temperature range, 600 ° C. is the minimum temperature required for hydrogen release, and 1000 ° C. is the temperature at which particles start to fuse.

Further, if the temperature is lower than 600 ° C, the magnetic properties (especially coercive force) are not completely restored, and if the temperature exceeds 1,000 ° C, the powder is fused. Therefore, it is preferable to set the condition in the range of 600 to 1,000 ° C. As the resin molding method, compression molding and injection molding can be applied.

Example 1 Component elements were weighed as shown by the general formula of Nd _0.8 Dy _0.1 Ce _0.1 {(Fe _0.8 Co _0.2 ) _0.92 B _0.08 } _6.0 and arc-melted in Ar gas to obtain a raw material alloy. Next, the raw material alloy was roughly pulverized in a stainless mortar, and then enclosed in a pot filled with toluene, and particles of about 10 μm were obtained by a vibration mill.
After pulverization, it was enclosed in a rubber tube (40 mmφ × 100 mm) and compression molded under hydrostatic pressure at 5 t / cm ² to prepare a green compact. Next, this green compact was evacuated (about 10 ^-3 Torr) and then heated at 1,080 ℃ for 1 hour.
After heating for a period of time to fix the powder compact and cooling it to room temperature, it was taken out of the heat treatment furnace, placed in a stainless steel high-pressure container, introduced with 50 kg / cm ² hydrogen gas, and given a disintegrating action by inhaling hydrogen, and then again using stainless steel. It was ground in a mortar. At this point, the material was separated with almost no impact, and a raw material having a desired particle size could be easily obtained with an industrial sieve of 500 μm.

Next, in order to remove the hydrogen content in the material, exhaust the gas to 200
The sample was heated at each temperature of ℃, 400 ℃, 500 ℃, 600 ℃, 800 ℃, 900 ℃, 1,000 ℃ for 4 hours, then furnace cooled and cooled to room temperature. After the treated powder was magnetized in a pulsed magnetic field and the magnetic characteristics were measured by a vibrating magnetometer, a change in coercive force with respect to the heating temperature was obtained as shown in FIG. As is clear from the drawing, coercive force is hardly obtained below 600 ° C, but 900 ~
The coercive force became maximum at 1,000 ° C. The sample after the treatment at 1,000 ° C. was partially fixed again and was not suitable as the raw material alloy powder for the resin-bonded magnet.

[Example 2] Nd _0.92 Dy _0.08 (Fe _0.915 B _0.085 ) _5.4 The constituent elements were weighed as represented by the general formula and arc-melted in Ar gas to obtain a raw material alloy (about 100 g of ingot) having the above composition. I got three. Next, each of the three melt-produced raw material alloy ingots was mechanically pulverized in a stainless mortar to a particle size of 200 μm or less, and further pulverized by a vibration mill to an average particle size of 5 μm. After pulverization,
A rubber tube (40 mmφ × 100 mm) was filled in the same manner as in Example 1, and compression molding was performed under hydrostatic pressure at 5 t / cm ² in a magnetic field to prepare a green compact. Next, this powder compact was evacuated (about 10 ^-3 Torr), heated at 1,080 ° C for 1 hour to fix the powder compact, cooled to room temperature, removed from the heat treatment furnace, and placed in a stainless steel high-pressure container. After introducing hydrogen gas of 50kg / cm ² for 2 hours and disintegrating by absorbing hydrogen, vacuum heat treatment is performed at 300 ° C, and then each ingot is crushed with a vibration mill to obtain 3 particles each with an average particle diameter of 26μm. Three types of powder of 19 μm and 14 μm were prepared.

Each of these was compression-molded under hydrostatic pressure in a magnetic field at 5 t / cm ² to form a magnet body, which was subjected to dehydrogenation treatment by heat treatment at 820 ° C. for 2 hours, and then vacuum-impregnated with an epoxy resin,
The resin was cured at room temperature. Table 1 below shows the results of the magnet characteristics of the obtained three types of magnets, and FIG. 2 shows the respective three types of demagnetization curves.

Comparative Example 1 Next, as a comparative example, alloy powder was produced without performing hydrogen pulverization. That is, as in Example 2, the component elements were weighed as represented by the general formula of Nd _0.92 Dy _0.08 (Fe _0.915 B _0.085 ) _5.4 , arm-melted in Ar gas, and the melt-produced raw material alloy ingot was placed in a stainless mortar. Mechanical crushing to a particle size of 200 μm or less, and further crushing to an average particle size of 5 μm with a vibration mill. After pulverization, rubber tube (40mmφ × 10
0 mm) and compacted under hydrostatic pressure at 5 t / cm ² in a magnetic field to prepare a green compact. Next, the green compact is evacuated (about
10 ⁻³ Torr), heat treatment at 1,080 ° C. for 1 hour to fix the powder compact, and after cooling to room temperature, mechanical crushing was performed on this magnet body without hydrogen crushing as in Example 2. Was added to obtain a green compact having a particle size of 500 μm and further pulverized in a vibration mill to have an average particle size of 16 μm, and a pressure of 5 t / cm ² was applied under hydrostatic pressure in a magnetic field to form a green compact.

Next, the green compact was heat-treated at 820 ° C. for 2 hours, the obtained magnet body was vacuum-impregnated with epoxy resin, and the resin was cured at room temperature. The measurement results of the obtained magnet are shown in Table 2 and its demagnetization curve is shown in FIG. As is clear from FIG. 2, when the comparative example and the example 2 were compared, a larger coercive force was obtained with the hydrogen pulverized product.

[Example 3] Nd _0.88 Dy _0.12 [(Fe _0.9 Co _0.1 ) _0.915 B _0.085 ] The constituent elements were weighed as represented by the general formula of _5.6 , and the above composition was obtained by arm dissolution in Ar gas as in the previous example. Was placed in a stainless steel high-pressure container, hydrogen gas of 50 kg / cm ² was introduced, and the mixture was left standing for 2 hours and then collapsed by absorbing hydrogen.
Particles of 0 μm were obtained. After that, 20kOe in the magnetic field press
In the magnetic field of, a pressure of 4 t / cm ² was applied to prepare a green compact, and heat treatment was performed at 800 ° C. for 2 hours to perform dehydrogenation treatment. In this process, the particles are bonded to each other in a point contact state, so they are ground again in a stainless mortar with a minimum force so as not to give a mechanical impact, and particles of 500 μm or less are prepared, and an epoxy resin is used. It was impregnated and cured at room temperature. Table 3 shows the measurement results of the obtained magnets.

[Comparative Example 2] For comparison, Table 4 shows the measurement results of the magnet in which particles having a particle size of 10 to 500 µm, which were obtained only by mechanical pulverization, were compared with Example 3 without hydrogen storage and collapse. Further, FIG. 3 shows a comparison of demagnetization curves of the obtained magnets. As is clear from FIG. 3, when the comparative example and the example 3 were compared, a larger coercive force was obtained in the case of hydrogen pulverization than in the case of mechanical pulverization alone.

[Example 4] Nd _0.92 Dy _0.08 [(Fe _0.97 Co _0.03 ) _0.92 B _0.08 ] As shown in the general form of _5.4 , the constituent elements were weighed and the above composition was obtained by arm melting in Ar gas as in the previous example. After making the alloy, mechanically crush it in a stainless mortar to obtain a particle size of 200
The average particle size is 5 μm or less using a vibration mill.
It was crushed until it became, and was shaped by applying a pressure of 4 t / cm ^{2 in} a magnetic field as in Example 3, and heat-treated at 1080 ° C. for 1 hour in vacuum.

After that, the magnet body was placed in a stainless steel high-pressure container at room temperature, 50 kg / cm ² of hydrogen gas was introduced, and it was left for 2 hours.
Vacuum heat treatment was performed at 300 ° C., and then pulverization was performed using a vibration mill to obtain an average particle size of 16 μm. Further in the magnetic field
Molding was performed by applying a pressure of 4 t / cm ² , heat treatment was performed at 900 ° C. for 2 hours, and then epoxy resin was vacuum-impregnated, and the resin was cured at room temperature. Table 5 shows the measurement results of this magnet.

[Comparative Example 3] Further, as a comparative example, one which does not store hydrogen was prepared, and the measurement results of this magnet are shown in Table 6 and the demagnetization curves thereof are shown in Fig. 4.

As is clear from FIG. 4, when the comparative example and the example 4 were compared, a larger holding force was obtained with the hydrogen-milled one.

[Advantages of the Invention] From the above, according to the present invention, desired particles of 10 to 500 μm can be easily produced by hydrogenating and pulverizing in the previous step of resin molding, and without applying any mechanical strain,
Since the dehydrogenation process is performed at 600-1,000 ℃, the residual magnetism Br and the coercive force iHc can exhibit their original magnetic characteristics, which is effective for applying the rare earth iron-based alloy to the raw material powder for resin-bonded permanent magnets. Target.

[Brief description of drawings]

FIG. 1 is a magnetic characteristic curve showing the coercive force with respect to the heating temperature in the present invention. FIG. 2 is a magnetic characteristic curve showing the coercive force with respect to the heating temperature in comparison with Example 2 of the present invention and Comparative Example. FIG. 3 is a magnetic characteristic curve showing the coercive force with respect to the heating temperature in comparison with Example 3 of the present invention and Comparative Example. FIG. 4 is a magnetic characteristic curve showing the coercive force with respect to the heating temperature in comparison with Example 4 of the present invention and Comparative Example.

Continuation of front page (56) References JP-A-58-135605 (JP, A) JP-A-61-270316 (JP, A) "Powder Metallurgical Technology Association," Japan Metallurgy Generation, page 35, 1964 Published by Nikkan Kogyo Shimbun

Claims (1)

[Claims] 1. R (T _1-y B _y ) _z (where R represents one or more rare earth metal elements containing at least Nd, and T
Indicates Fe or Fe and Co, 0.05 ≦ y ≦ 0.10, 4.5 ≦
It is specified in the range of z ≦ 6.5. In the production of alloy powder for resin-bonded permanent magnets having the composition represented by the general formula (1), the molten alloy is roughly pulverized, then finely pulverized by a vibration mill, and the obtained particles are compression-molded to obtain a green compact. This compact was heated, and the sintered compact that had been fixed by heating was enclosed in a hydrogen atmosphere to form a hydrogen compound and disintegrate, and then mechanically pulverized again to obtain a particle size of 10 to 500 μm. And a dehydrogenation treatment by heating the particles to 600 to 1,000 ° C. to produce an alloy powder for a resin-bonded permanent magnet.