JP3365628B2 - Iron-based alloy permanent magnet powder and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an iron-based alloy permanent magnet powder most suitable as a magnet used in electric devices such as various motors, actuators, speakers, meters, focus convergence rings, and a method for producing the same. The present invention also relates to a bond magnet made from the above magnet powder and various electric devices equipped with the bond magnet.

[0002]

2. Description of the Related Art Nanocomposite magnets based on Fe-RB alloys include, for example, microcrystals of iron-based borides that are soft magnetic phases such as Fe ₃ B and Fe ₂₃ B ₆ and R ₂ that are hard magnetic phases.
It is an iron-based alloy permanent magnet in which fine crystals of the Fe ₁₄ B phase are uniformly distributed in the same metallic structure, and both are magnetically coupled by exchange interaction.

The nanocomposite magnet can exhibit excellent magnet characteristics by the magnetic coupling between the soft magnetic phase and the hard magnetic phase even though it contains the soft magnetic phase. Further, as a result of the presence of the soft magnetic phase containing no rare earth element R such as Nd, the content of the rare earth element R can be suppressed low as a whole. This is advantageous in reducing the manufacturing cost of the magnet and stably supplying the magnet.

Such a nanocomposite magnet is produced by solidifying a molten raw material alloy by a quenching method and then subjecting it to an appropriate heat treatment. A single roll method is often used when quenching the raw material melt. The single roll method is a method in which the molten alloy is cooled and solidified by bringing the molten alloy into contact with a rotating cooling roll. According to this method, the shape of the quenched alloy is a ribbon (ribbon) shape extending along the circumferential velocity direction of the cooling roll.

[0005] Conventionally, it has been practiced to produce a quenched alloy ribbon having a thickness of 50 µm or less at a roll surface speed of 15 m / sec or more. The quenched alloy ribbon produced in this manner, after being given permanent magnet characteristics by heat treatment,
The magnet powder is pulverized to have an average particle size of 300 μm or less to obtain magnet powder. This magnet powder constitutes a permanent magnet body having a desired shape by, for example, compression molding or injection molding.

[0006]

A comparatively thin quenched alloy ribbon having a thickness of 50 μm or less is crushed to obtain an average particle diameter of 300 μm.
When a powder having a particle size of m or less is produced, the obtained powder particles have a flat shape. Therefore, the magnet powder produced by the above-mentioned conventional technique has poor filling property and fluidity at the time of molding, and the magnetic powder filling rate (magnetic powder volume / bonded magnet volume) is 80% at maximum in the case of compression molding, In the case of molding, the maximum is 65%. This magnetic powder filling rate affects the characteristics of the permanent magnet body that is the final product, and it is strongly desired to improve the magnetic powder filling rate in order to improve the permanent magnet characteristics.

The present invention has been made in view of the above points, and its main purpose is to improve the filling property and fluidity at the time of molding by changing the particle shape from flat to nearly spherical. It is to provide a base alloy permanent magnet powder and a method for producing the same.

Another object of the present invention is to provide a bonded magnet which uses the above-mentioned iron-based alloy permanent magnet powder and can exhibit excellent permanent magnet characteristics by improving the packing ratio of the magnetic powder, and a bonded magnet. It is to provide an electric device equipped with.

[0009]

A method for producing an iron-based alloy permanent magnet powder according to the present invention comprises a method of cooling a molten Fe-R-B alloy by a quenching method, whereby a solidification having a thickness of 80 μm or more and 300 μm or less is performed. A cooling step to form an alloy,
A step of crystallizing the rapidly solidified alloy by heat treatment to produce an alloy having permanent magnet characteristics; and crushing the alloy to obtain an average particle size of 50 μm or more and 300 μm or less and a short particle size with respect to a major axis size of the powder particle. Forming a powder having an axial size ratio of 0.3 or more and 1.0 or less.

In a preferred embodiment, a step of coarsely crushing the rapidly solidified alloy is further performed before the heat treatment.

It is preferable that the crushing is performed by a pin mill device.

[0012] In a preferred embodiment, the rapidly solidified alloy is Fe ₂₃ B ₆ , Fe before the heat treatment.
_It contains a metallic structure containing at least one metastable phase selected from the group consisting of ₃ B, R ₂ Fe ₁₄ B, and R ₂ Fe ₂₃ B ₃ , and / or an amorphous phase.

In a preferred embodiment, the alloy having the permanent magnet _{properties, Fe 100-xy R x B} y (R is, P
A permanent magnet represented by a composition formula of at least one kind of rare earth element selected from the group consisting of r, Nd, Dy, and Tb, wherein x and y in the composition formula are 1 atomic%
≦ x ≦ 6 atomic% and 15 atomic% ≦ y ≦ 25 atomic% are satisfied, and Fe, Fe and B alloys, and a compound having a R ₂ Fe ₁₄ B type crystal structure are included as constituent phases. The average crystal grain size of each constituent phase is 150 nm or less.

In the cooling step, it is preferable to bring the molten metal into contact with a roll rotating at a roll surface speed of 1 m / sec or more and 13 m / sec or less, thereby forming the rapidly solidified alloy.

In the cooling step, under a reduced pressure atmosphere,
It is preferable to include a step of rapidly cooling the molten metal of the Fe-RB alloy.

The absolute pressure of the reduced pressure atmosphere is preferably 50 kPa or less.

In a preferred embodiment, the alloy crystallized by the heat treatment is a nanocomposite magnet.

The method for producing a bonded magnet according to the present invention comprises the steps of preparing the iron-based alloy permanent magnet powder by any one of the methods for producing an iron-based alloy permanent magnet powder, and molding the iron-based alloy permanent magnet powder. And the step of performing.

In a preferred embodiment, the iron-based alloy permanent magnet powder is molded by a compression molding method at a filling rate of more than 80%.

In a preferred embodiment, the iron-based alloy permanent magnet powder is molded by an injection molding method with a filling rate of more than 65%.

The iron-based alloy permanent magnet powder according to the present invention is F
_{e 100-xy R x B y} (Fe iron, B is boron, R represents, P
An iron-based alloy permanent magnet powder represented by a composition formula of at least one rare earth element selected from the group consisting of r, Nd, Dy, and Tb, wherein x and y in the composition formula
Is 1 atom% ≦ x ≦ 6 atom% and 15 atom% ≦ y ≦
Satisfying the relationship of 25 atomic%, and as the constituent phase, F
e, an alloy of Fe and B, and a compound having an R ₂ Fe ₁₄ B type crystal structure, and the average crystal grain size of each constituent phase is 150
nm or less, the average particle diameter is 300 μm or less, and the ratio of the size in the minor axis direction to the size in the major axis direction of the powder is 0.3 or more and 1.0 or less.

A bonded magnet according to the present invention contains the above iron-based alloy permanent magnet powder. 80% when using compression molding
Shows a filling factor of over 65% when injection molding is used.
A filling factor exceeding 10 is shown.

An electric device according to the present invention includes the above-mentioned bonded magnet.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, first, Fe-RB
The molten alloy is cooled by quenching method such as jet casting method or strip casting method.
A rapidly solidified alloy of 0 μm or more and 300 μm or less is formed.
Then, the rapidly solidified alloy is given a permanent magnet property by heat treatment, and then the alloy is pulverized to obtain an average particle size of 5
A powder having a ratio of the size in the minor axis direction to the size in the major axis direction of the powder particles of 0.3 μm or more and 1.0 or less is formed in the range of 0 μm to 300 μm. According to the invention, the powder has a particle size of 50
It is possible to set the ratio of the size in the minor axis direction to the size in the major axis direction to 0.3 or more and 1.0 or less for 60% by weight or more of the particles exceeding μm.

Fe-RB alloys include Fe
_{100-xy R x B y (} Fe iron, B is boron, R represents Pr, N
(It is at least one kind of rare earth element selected from the group consisting of d, Dy, and Tb) is preferably used. X and y in the above composition formula in a preferred embodiment are
1 atom% ≤ x ≤ 6 atom%, 15 atom% ≤ y ≤ 25 atom%
Satisfy the relationship. In a preferred embodiment, the molten alloy having the above composition is cooled by a melt-quenching method to form a rapidly solidified alloy containing an amorphous phase, and then the rapidly solidified alloy is heated to form microcrystals. It can be formed and manufactured. In order to obtain a uniform structure, rapid cooling is preferably performed under a reduced pressure atmosphere. In a preferred embodiment, the chill roll is contacted with the molten alloy, thereby forming a rapidly solidified alloy.

In the present invention, as described above, the thickness of the alloy ribbon immediately after rapid solidification is 80 μm or more and 300 μm or less. When a melt spinning method such as a single roll method is used, the thickness of the alloy ribbon immediately after rapid solidification is adjusted to 80 μm or more and 300 μm or less by adjusting the surface speed of the cooling roll within the range of 1 m / sec or more and 13 m / sec or less. Can be controlled. The reason for adjusting the thickness of the alloy ribbon in this way will be described below.

When the roll surface speed is less than 1 m / sec, the thickness of the quenched alloy ribbon becomes thicker than 300 μm, but a quenched alloy structure containing a large amount of α-Fe and Fe ₂ B is formed. R ₂ which is a hard magnetic phase even after heat treatment
Fe ₁₄ B does not precipitate and permanent magnet characteristics are not exhibited.

On the other hand, when the roll surface velocity exceeds 13 m / sec, the thickness of the quenched alloy ribbon becomes thin below 80 μm, and in the crushing step after the heat treatment, in the direction almost perpendicular to the roll contact surface (alloy thin film). It becomes easy to fracture along the thickness direction of the strip. As a result, the quenched alloy ribbon is easily broken into a flat shape, and the ratio of the size of the obtained powder particles in the minor axis direction to the size in the major axis direction is less than 0.3. It is difficult to improve the magnetic powder packing rate in flat powder particles such that the ratio of the size in the minor axis direction to the size in the major axis direction is less than 0.3.

From the above, in the preferred embodiment, the roll surface speed is adjusted so that the thickness of the quenched alloy ribbon is 80 μm.
The above range is set to 300 μm or less. as a result,
The pulverizing step makes it possible to produce magnet powder having an average particle size of 300 μm or less and a ratio of the size in the minor axis direction to the size in the major axis direction of 0.3 or more and 1.0 or less. A more preferable range of this ratio is 0.4 or more and 1.0 or less.

The rapidly solidified alloy contains heat for crystallization.
Has or does not have an amorphous structure before treatment
Is Fe_{twenty three}B₆, Fe₃B, R₂Fe₁₄B and R₂Fe
_{twenty three}B ₃At least one metastable selected from the group consisting of
In some cases, the metal structure has a mixed phase and an amorphous phase.
is there. The proportion of metastable phases decreases when the cooling rate is high
However, the proportion of the amorphous phase increases.

The crystallites produced by the heat treatment of the rapidly solidified alloy are iron, an alloy of iron and boron, R ₂ Fe ₁₄ B.
It is formed of a compound having a type crystal structure. The average crystal grain size of each constituent phase is preferably 150 nm or less. The more preferable average crystal grain size of each constituent phase is 10
0 nm or less, and a more preferable average crystal grain size is 60 n
m or less. According to the present invention, since the alloy ribbon (thickness: 80 to 300 μm) before crushing is composed of the above-mentioned fine crystals, it is easy to break in various directions by the crushing process.
As a result, it is considered that powder particles having a shape close to a sphere can be easily obtained. That is, according to the present invention, powder particles elongated along a certain direction are not obtained, but powder particles having an equiaxial shape, that is, a shape close to a sphere are formed.

On the other hand, when the surface velocity of the roll is increased to make the thickness of the alloy ribbon thinner than 80 μm, as described above, the metallographic structure of the alloy ribbon tends to be aligned in the direction perpendicular to the roll contact surface. is there. Therefore, it is easy to break along its orientation, the powder particles obtained by pulverization are likely to be elongated shape along the direction parallel to the surface of the alloy ribbon, the short axis relative to the long-axis direction size of the powder particles. The ratio of the direction sizes is less than 0.3.

FIG. 1 (a) schematically shows the alloy ribbon 10 before the crushing step and the powder particles 11 after the crushing step in the magnet powder manufacturing method according to the present invention. On the other hand, FIG.
FIG. 2B schematically shows the alloy ribbon 12 before the pulverizing step and the powder particles 13 after the pulverizing step in the above-described conventional method for producing magnet powder.

As shown in FIG. 1 (a), in the case of the present invention, since the alloy ribbon 10 before pulverization is composed of equiaxed crystals having a small grain size, fracture occurs along random orientations. It is easy to produce equiaxed powder particles 11. On the other hand, in the case of the conventional technique, as shown in FIG. 1 (b), since the alloy ribbon 12 is easily broken in a direction substantially perpendicular to the surface thereof, the shape of the particles 13 becomes flat. .

When the alloy melt is rapidly cooled and solidified in a reduced pressure atmosphere, the amount of rare earth metal is small,
It is possible to uniformly form fine crystals of the compound having the R ₂ Fe ₁₄ B type crystal structure (average particle size: 150 nm or less), and as a result, it becomes possible to manufacture a permanent magnet exhibiting excellent magnetic characteristics.

On the other hand, when the molten alloy having the above composition is cooled under an atmospheric pressure atmosphere, the cooling rate of the molten alloy becomes non-uniform, so that α-Fe crystals are easily generated and R ₂ Fe is generated.
₁₄ It becomes impossible to produce a compound having a B-type crystal structure. Further, since the nonuniform cooling rate causes the nonuniform phase to occur, the heat treatment for crystallization causes a problem that the crystal grains become coarse.

In the permanent magnet powder of the present invention,
Exchange coupling due to a mixture of iron, a soft magnetic texture phase composed of an alloy of iron and boron, and a hard magnetic compound phase having an R ₂ Fe ₁₄ B type crystal structure, and the average crystal grain size of each constituent phase is small. Is getting stronger.

[Reasons for limiting composition] The rare earth element R is a permanent magnet.
R, which is a hard magnetic phase required to develop stone characteristics ₂
Fe₁₄It is an essential element for B. R content (x) is 1 original
Less than% child, R₂Fe ₁₄Compound having B-type crystal structure
The phase cannot be precipitated and the coercive force exerting effect is small.
Further, when it exceeds 6 atomic%, R is a hard magnetic phase.₂F
e₁₄B is not generated and the coercive force is significantly reduced.
Therefore, the composition ratio y of the rare earth element R is 1 atom% ≦ x ≦ 6.
Atomic% must be satisfied, 2 atomic% ≤ x ≤ 5.7 original
It is preferable to satisfy the child%.

Boron (B) is an essential element for iron-based borides such as Fe ₃ B and Fe ₂₃ B ₆ which are soft magnetic phases of permanent magnet materials and R ₂ Fe ₁₄ B which is a hard magnetic phase. is there.
When the content of B (composition ratio y) is less than 15 atomic%, it is difficult to obtain an amorphous structure even when the molten alloy is rapidly cooled by the liquid quenching method. Therefore, when the melt of the raw material alloy is rapidly solidified by the single roll method, the thickness is 70 μm or more and 300 μm or more.
When the rapidly solidified alloy is formed under the condition of being in the range of μm or less, a preferable metallographic structure is not formed and sufficient permanent magnet characteristics are not exhibited even by heat treatment. On the other hand, if it exceeds 25 atomic%, the squareness ratio of the demagnetization curve is remarkably lowered, and the residual magnetic flux density B _r is lowered, which is not preferable. Therefore, the boron composition ratio x needs to satisfy 15 atomic% ≤ x ≤ 25 atomic%, and preferably 16 atomic% ≤ y ≤ 20 atomic%. Note that part of B may be replaced with C (carbon).

As the raw material, the element M (Al, Si, T
i, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr,
At least one element selected from the group consisting of Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb) may be added. The addition of the element M has a squareness ratio of J _r /
It has effects such as improvement of J _s and expansion of operating temperature range capable of exhibiting optimum magnetic characteristics. If the content of the element M is less than 0.05 atom%, such an effect is not sufficiently exhibited, and if it exceeds 7 atom%, the magnetization starts to decrease. Therefore, the composition ratio z of the additional element M needs to satisfy 0.05 atom% ≦ z ≦ 7 atom%, and preferably 0.2 atom% ≦ z ≦ 5 atom%.

Further, cobalt (Co) may be added to the raw material. Co has the effect of improving the squareness ratio and substituting the maximum energy product by being replaced with part of Fe. Therefore, when it is desired to increase the squareness ratio, Co
Is preferably added.

Fe accounts for the remaining content of the above elements.

Next, a preferred embodiment of the method for producing the iron-based permanent magnet alloy powder according to the present invention will be described in detail.

First, a raw material represented by the above composition formula is prepared, and this raw material is heated and melted to prepare a molten alloy. This molten alloy is quenched by the melt quenching method to form a rapidly solidified alloy containing an amorphous phase. As the melt quenching method, a strip casting method can be used in addition to the melt spinning method using the single roll method. In addition, if a quenched alloy having a thickness of 80 μm or more and 300 μm or less can be formed, it is possible to use a molten metal solidification apparatus using twin rolls.

[Description of Quenching Device] In the present embodiment, a raw material alloy is manufactured using, for example, the melt spinning device shown in FIG. In order to prevent the oxidation of the raw material alloy containing a rare earth element that is easily oxidized, the alloy manufacturing process is performed in an inert gas atmosphere. A rare gas such as helium or argon is preferably used as the inert gas. Since nitrogen easily reacts with the rare earth element, it is not preferable to use it as an inert gas.

The apparatus shown in FIG. 2 is provided with a melting chamber 1 and a quenching chamber 2 for the raw material alloy, which can maintain the vacuum or inert gas atmosphere and adjust the pressure thereof.

The melting chamber 1 is provided with a melting furnace 3 for melting a raw material 20 mixed to have a desired magnet alloy composition at a high temperature.
A hot water storage container 4 having a tapping nozzle 5 at the bottom, and a blended raw material supply device 8 for feeding the blended raw material into the melting furnace 3 while suppressing the entry of air. The hot water storage container 4 is
It has a heating device (not shown) capable of storing the melt 21 of the raw material alloy and maintaining the temperature of the molten metal at a predetermined level.

The quenching chamber 2 has the molten metal 2 discharged from the molten metal discharge nozzle 5.
A rotary cooling roll 7 for rapidly solidifying 1 is provided.

In this apparatus, the atmosphere and its pressure in the melting chamber 1 and the quenching chamber 2 are controlled within a predetermined range. Therefore, the atmospheric gas supply ports 1b, 2b, and 8b and the gas exhaust ports 1a, 2a, and 8a are provided at appropriate places of the apparatus. In particular, the gas exhaust port 2a is connected to a pump in order to control the absolute pressure in the quenching chamber 2 within the range of vacuum to 50 kPa.

The melting furnace 3 is tiltable, and the molten metal 21 is appropriately poured into the hot water storage container 4 via the funnel 6. Molten metal 21
Is heated in the hot water storage container 4 by a heating device (not shown).

The hot water outlet nozzle 5 of the hot water storage container 4 is arranged on the partition wall between the melting chamber 1 and the quenching chamber 2, and the molten metal 21 inside the hot water storage container 4 is
To the surface of the cooling roll 7 located below. The orifice diameter of the tap nozzle 5 is, for example, 0.5 to 2.0 m.
m. When the melt 21 has a large viscosity, it becomes difficult for the melt 21 to flow in the hot water discharge nozzle 5. However, in the present embodiment, since the quenching chamber 2 is kept at a lower pressure state than the melting chamber 1, the melting chamber 1 and the quenching chamber 2 are separated from each other. A pressure difference is formed between the molten metal 21
The tap water is smoothly executed.

The cooling roll 7 is made of Cu, Fe, or Cu.
It is preferably formed from an alloy containing Fe or Fe. If the cooling roll is made of a material other than Cu or Fe, the exfoliation property of the quenched alloy from the cooling roll deteriorates, and therefore the quenched alloy may be wound around the roll, which is not preferable. The diameter of the cooling roll 7 is, for example, 300 to 500 mm. The water cooling capacity of the water cooling device provided in the cooling roll 7 is calculated and adjusted according to the solidification latent heat and the amount of tapping water per unit time.

The surface of the cooling roll 7 is covered with, for example, a chromium plating layer. The surface roughness of the cooling roll 7 is center line average roughness Ra ≦ 0.8 μm and maximum Rmax ≦ 3.2 μ.
It is preferable that m and ten-point average roughness Rz ≦ 3.2 μm. If the surface of the cooling roll 7 is rough, the quenched alloy tends to stick to the roll, which is not preferable.

According to the apparatus shown in FIG. 2, for example, a total of 20
It is possible to rapidly solidify kg of the raw material alloy in 15 to 30 minutes. The quenched alloy thus formed has a thickness of 80 μ.
The alloy ribbon (alloy ribbon) 22 has a width of m to 300 μm and a width of 2 mm to 6 mm. [Explanation of Quenching Method] First, a melt 21 of a raw material alloy represented by the above-mentioned composition formula is prepared, and then, as shown in FIG.
It is stored in the hot water storage container 4 of the melting chamber 1. Next, this molten metal 21
Is tapped from the tapping nozzle 5 onto the water-cooling roll 7 in the reduced pressure Ar atmosphere, and is rapidly cooled by contact with the water-cooling roll 7,
Solidify. As the rapid solidification method, it is necessary to use a method capable of controlling the cooling rate with high accuracy.

In the present embodiment, when the molten metal 21 is cooled and solidified, the cooling rate is 10 ³ to 10 ⁵ ° C / sec. At this cooling rate, the temperature of the alloy is lowered by ΔT ₁ .
Since the temperature of the molten alloy 21 before quenching is close to the melting point T _m (for example, 1200 to 1300 ° C.), the temperature of the alloy falls on the cooling roll 7 from T _m to (T _m −ΔT ₁ ). . According to the experiment by the inventor of the present application, ΔT ₁ is preferably in the range of 700 to 1100 ° C. from the viewpoint of improving the final magnet characteristics.

The time for the molten alloy 21 to be cooled by the cooling roll 7 corresponds to the time from the contact of the alloy from the outer peripheral surface of the rotating cooling roll 7 to the separation thereof, and in the case of this embodiment, it is 0.05. ~ 50 ms. Meanwhile, the temperature of the alloy further decreases by ΔT ₂ and solidifies. afterwards,
The solidified alloy leaves the chill roll 7 and flies in an inert atmosphere. The alloy loses heat by the atmospheric gas while flying in a ribbon shape, and as a result, its temperature is (T _m −ΔT ₁ −ΔT
₂ ). ΔT ₂ is about 100 ° C. or higher, though it varies depending on the size of the apparatus and the pressure of the atmospheric gas.

The atmosphere in the quenching chamber 2 is depressurized. The atmosphere is preferably composed of an inert gas having an absolute pressure of 50 kPa or less. In addition, when the pressure of the atmospheric gas exceeds 50 kPa, the influence of the atmospheric gas being caught between the rotating roll and the molten alloy becomes remarkable, which may increase the possibility that a uniform structure cannot be obtained, which is not preferable.

In the present invention, the thickness of the quenched alloy ribbon is set within the range of 80 μm to 300 μm by adjusting the roll surface speed within the range of 1 m / sec to 13 m / sec. If the roll surface speed is less than 1 m / sec,
Since the average crystal grain size becomes too large, the desired magnetic properties cannot be obtained, which is not preferable. On the other hand, when the roll surface peripheral velocity exceeds 13 m / sec, the thickness of the quenched alloy ribbon falls below 70 μm, and the ratio of the size in the minor axis direction to the size in the minor axis direction (minor axis / major axis) in the crushing process described later. Only powder particles having a value of less than 0.3 can be obtained.

[Explanation of Heat Treatment] After performing the quenching step, the quenching alloy is subjected to crystallization heat treatment to generate fine crystals having an average grain size of 100 nm or less. This heat treatment is 400 ° C to 700 ° C, more preferably 500 ° C.
It is preferable to heat at a temperature of ℃ to 700 ℃ for 30 seconds or more. When the heat treatment temperature exceeds 700 ° C., grain growth is remarkable and the magnetic properties are deteriorated. Conversely, the heat treatment temperature is 400 ° C
If it is less than the above range, a high coercive force cannot be obtained because the R ₂ Fe ₁₄ B phase does not precipitate.

When heat treatment is performed under the above conditions, fine crystals (iron, an alloy of iron and boron, and a compound having an R ₂ Fe ₁₄ B type crystal structure) are formed so that the average crystal grain size is 150 nm or less. can do. The preferable heat treatment time depends on the heat treatment temperature, but is, for example, 600 ° C.
In the case of heat treatment in step 2, it is preferable to perform heating for about 30 seconds to 30 minutes. If the heat treatment time is less than 30 seconds, crystallization may not be completed.

Before the heat treatment, coarse crushing is performed,
It is preferable that the powder has an average particle size of about 1 mm to 500 μm.

[Description of Crushing Step] The alloy of the present invention can be crushed by using, for example, a pin disk mill device as shown in FIG. FIG. 4 is a sectional view showing an example of a pin mill device used in this embodiment. The pin mill device 40 is a pin disc mill, and discs (discs) 42a and 42b having a plurality of pins 11 arranged on one surface thereof.
Are opposed to each other and are arranged so that the pins 41 do not collide with each other. At least one of the disks 42a and / or 42b rotates at high speed. In the example of FIG. 4, the disc 42
a rotates about axis 43. Disk 42a on the rotating side
A front view of the is shown in FIG. On the disk 42a of FIG. 5, the pins 41 are arranged so as to draw a plurality of concentric circles. Even on the fixed disk 42b, the pins 41 are arranged so as to draw concentric circles.

The object to be crushed by the pin disk mill is fed from the charging port 44 into the space of the gap where the two disks face each other, and is stopped at the pin 41 on the rotating disk 42a and stopped. It collides with the pin 41 on the disk 42b and is crushed by the impact. The powder generated by the pulverization is blown in the direction of arrow A and finally collected in one place.

In the pin mill device 40 of this embodiment,
The disks 42a and 42b supporting the pin 41 are made of stainless steel or the like, but the pin 41 is made of a cemented carbide material such as a tungsten carbide (WC) sintered body. As the cemented carbide material, TiC, MoC, NbC, TaC, Cr ₃ C _{2 and the} like can be suitably used in addition to the WC sintered body. These cemented carbides have IV
It is a sintered body in which carbide powders of metals belonging to the groups a, Va, and VIa are bonded using Fe, Co, Ni, Mo, Cu, Pb, or Sn or alloys thereof.

In the case of the present invention, if the above-mentioned pin mill is used to carry out the pulverization under the condition that the average particle diameter is 1 μm or more and 300 μm or less, the ratio of the particle size in the minor axis direction to the particle size in the major axis direction is 0. A powder of 3 or more and 1.0 or less can be obtained. A more desirable range of average particle size is 5
It is not less than μm and not more than 200 μm. The pin mill device preferably used in the present invention is not limited to a pin disc mill in which pins are arranged on a disc, and may be, for example, a device in which pins are arranged on a cylinder.

[Description of Manufacturing Method of Magnet] First, a compound is prepared by adding a binder made of an epoxy resin and an additive to the magnet powder obtained as described above and kneading. Next, after compression-molding with a molding device having a molding space of a desired shape of the compound, a final bonded magnet can be obtained through a heat curing step, a washing step, a coating step, an inspection step, and a magnetizing step.

The molding process is not limited to the compression molding described above, and may be known extrusion molding, injection molding, or roll molding. The magnet powder is kneaded with plastic resin or rubber depending on the type of molding method used.

In the case of injection molding, not only polyimide (nylon) which is widely used as a resin but also PPS
As described above, a high softening point resin can be used. This is because the magnet powder of the present invention is formed of a low rare earth alloy, so that it is difficult to oxidize and the magnet characteristics do not deteriorate even if injection molding is performed at a relatively high temperature.

Since the magnet powder of the present invention is not easily oxidized, it is not necessary to coat the final magnet surface with a resin film. Therefore, for example, the magnetic powder of the present invention and the molten resin are press-fitted into a slot of a component having a complicated shape by injection molding, thereby manufacturing a component integrally provided with a magnet having a complicated shape. It is possible.

[Explanation of Electrical Equipment] The present invention is based on, for example, IP.
It is preferably applied to an M (Interior Permanent Magnet) type motor. This IPM type motor can include a rotor-integrated magnet made by using the magnet powder according to the present invention.

An IPM type motor according to a preferred embodiment comprises a rotor core containing a bond magnet filled with the above-mentioned magnet powder at a high density, and a stator surrounding the rotor core. A plurality of slots are formed in the rotor core, and the magnet of the present invention is located in the slots. This magnet melts the compound of magnet powder according to the invention and directly fills the slots of the rotor core,
It is molded.

The magnet of the present invention is suitable for use in various electric devices such as other types of motors and actuators, in addition to this type of motor.

(Examples) Examples of the present invention will be described below.

Example No. 1-No. For each of No. 6, Fe, Co, B, Nd, and Pr having a purity of 99.5% or more were weighed so that the total amount was 100 g,
It was placed in a quartz crucible. Each Example No. 1-No. 6
The composition was as shown in Table 1. Since the quartz crucible has an orifice with a diameter of 0.8 mm at the bottom, the above raw material is melted in the quartz crucible and then becomes an alloy melt and drops downward from the orifice. The raw material was melted by using a high frequency heating method under an argon atmosphere with a pressure of 2 kPa. In this embodiment, the melting temperature is 13
It was set at 50 ° C.

By pressing the molten metal surface of the molten alloy at 32 kPa, the molten metal was jetted to the outer peripheral surface of the copper roll located 0.8 mm below the orifice. The roll rotates at high speed while the inside is cooled so that the temperature of the outer peripheral surface is maintained at about room temperature. For this reason, the molten alloy that dripped from the orifice comes into contact with the peripheral surface of the roll to remove heat, and is blown in the circumferential velocity direction. Since the molten alloy is continuously dripped on the peripheral surface of the roll through the orifice, the alloy solidified by quenching is a ribbon elongated in a ribbon shape (width: 2 to 5 mm, thickness: 70 to 300 μ).
m).

In the case of the rotating roll method (single roll method) employed in this embodiment, the cooling rate is defined by the roll peripheral speed and the molten metal flow rate per unit time. The flow-down amount depends on the orifice diameter (cross-sectional area) and the molten metal pressure. In the embodiment, the orifice diameter is 0.8 mm and the molten metal injection pressure is 30 mm.
The flow rate was about 0.1 kg / sec.
In this embodiment, the roll surface speed Vs is set in the range of 2 to 12 m / sec. The thickness of the obtained quenched alloy ribbon is 85μ.
It was in the range of m to 272 μm.

In order to obtain a rapidly solidified alloy containing an amorphous phase, the cooling rate is preferably 10 ³ ° C / sec or more. To achieve the cooling rate in this range, the roll peripheral velocity is 2 m / sec or more. It is preferable to set to.

Cu was applied to the thin strip of the quenched alloy thus obtained.
The characteristic X-ray analysis of Kα was performed. Example No. 2 and No. The powder X-ray diffraction pattern for No. 4 is shown in FIG. As can be seen from FIG. 2 and N
o. The rapidly solidified alloy of No. 4 has an amorphous structure and a metal structure containing Fe ₂₃ B ₆ .

[0079]

[Table 1]

In Table 1, for example, "Nd5.5" in the column labeled "R" indicates that 5.5 atomic% of Nd was added as a rare earth element, and "Nd2.5 + Pr2" is a rare earth element. Nd is 2.5 atomic% and Pr is 2 atomic%
It shows that it was added.

Then, the obtained quenched alloy ribbon was roughly crushed to form a powder having an average particle size of 850 μm or less, and then, Table 1
The heat treatment was performed for 10 minutes in the argon atmosphere at the temperature shown in. After that, the coarsely pulverized powder is pulverized to 150 μm or less by a disc mill device to obtain the magnet powder (magnet powder) of the present invention.
Was produced. Table 2 shows the magnetic properties of this magnet powder and the ratio of the size in the minor axis direction to the size in the minor axis direction of powder particles having a particle size of 40 μm or more (minor axis / long axis).

[0082]

[Table 2]

As can be seen from Table 2, Example No. 1 to
No. The minor axis / major axis ratio in the magnet powder of No. 6 is 0.
It was 3 or more and 1.0 or less.

Next, 2% by mass of epoxide was added to the above magnet powder.
After kneading the resin, 5.9 × 10 ⁸Press molding of Pa
A cylindrical molded body with a diameter of 10 mm and a height of 7 mm is produced by pressure.
did. After that, the molded body is exposed to air at 150 ° C. for 1 hour.
After a time curing process, a bonded magnet is produced.
It was Table 3 shows the magnetic properties and the magnetic powder filling of this bonded magnet.
Indicates the density. Here, the magnetic powder packing density is defined as "volume of magnetic powder / bottle
Volume of the magnet.

[0085]

[Table 3]

As can be seen from Table 3, the compression-molded bonded magnet according to the present invention has achieved a high magnetic powder filling rate of 80% or more.

(Comparative Example) Comparative Example No. 1 in Table 1. 7-9 are
It was manufactured by the same process as described in the above example. The difference from the example is that the roll surface speed was adjusted to 15 m / sec or more and 30 m / sec or less during the rapid cooling of the molten alloy, whereby the thickness of the quenched alloy ribbon was set to 20 μm or more and 65 μm or less.

Table 2 shows the magnetic characteristics and the minor axis / major axis ratio of the magnet powder, and Table 3 shows the magnetic characteristics and the packing ratio of the magnetic particles of the compression-molded bonded magnet for the comparative example. As can be seen from Table 2, the minor axis / major axis ratio of the comparative example is less than 0.3. Further, as can be seen from Table 3, the magnetic powder filling rate of the comparative example is 80.
It is less than%. In addition, the magnetic powder filling rate here is shown by magnet powder volume / bond magnet volume.

FIG. 6 is a cross-sectional SEM photograph of a bonded magnet produced by compression molding the powder according to the present invention. On the other hand, FIG. 7 is a cross-sectional view SE of a bond magnet (comparative example) produced by compression-molding a powder having a product name MQP-B manufactured by MQI.
It is an M photograph. According to the invention, 60% by weight or more of the powder particles having a particle size of 40 μm or more have a minor axis / major axis ratio of 0.3 or more. In the case of the comparative example, powder particles having a particle size of 0.5 μm or less may include those having a minor axis / major axis ratio of 0.3 or more, but a particle size of 40 μm.
Most powder particles of m and above have a minor axis / major axis ratio of less than 0.3.

[0090]

According to the present invention, an iron-based alloy permanent magnet powder having improved filling properties and fluidity during molding can be obtained. By using this iron-based alloy permanent magnet powder,
Provided are a bond magnet having an improved magnetic powder filling rate and an electric device including the bond magnet.

[Brief description of drawings]

FIG. 1 (a) is a perspective view schematically showing an alloy ribbon before crushing and powder particles after crushing according to the present invention,
(B) is a perspective view which shows typically the alloy ribbon before crushing and the powder particle after crushing regarding a prior art.

FIG. 2 (a) is a diagram showing a structural example of a melt spinning device (single roll device) that can be preferably used in the present invention, and FIG. 2 (b) is a partially enlarged view thereof.

FIG. 3 is a graph showing a powder X-ray diffraction pattern for an example of the present invention.

FIG. 4 is a diagram showing a configuration of a pin mill device used in the present invention.

5 is a diagram showing a pin arrangement of the pin mill device of FIG. 4. FIG.

FIG. 6 is a cross-sectional SEM photograph of a bonded magnet according to the present invention.

FIG. 7 is a cross-sectional SEM photograph of a bonded magnet of a comparative example.

[Explanation of symbols]

1 Melting chamber 2 quenching room 3 melting furnace 4 Hot water storage container 5 Hot water nozzle 6 funnel 7 rotating cooling rolls 1a, 2a, 8a gas exhaust port 10 Alloy ribbon in the case of the present invention 11 Powder particles according to the present invention 12 Alloy ribbon in the case of the prior art 13 Conventional powder particles 20 raw materials

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C22C 38/00 303 H01F 1/08 A H01F 1/04 41/02 G 1/08 1/06 A 41/02 1/04 ( 58) Fields surveyed (Int.Cl. ⁷ , DB name) H01F 1/00-1/117 B22F C22C

Claims (11)

(57) [Claims] 1. A rare earth element of 1 atomic% or more and 6 atomic% or less.
And a molten Fe-R-B alloy containing 15 atomic% or more and 25 atomic% or less of boron by a single roll method under a reduced pressure atmosphere.
Cooled under ambient air, resulting in a thickness of 80 μm or more 300
a cooling step of forming a rapidly solidified alloy having a size of less than or equal to μm; a step of crystallizing the rapidly solidified alloy by heat treatment to produce an alloy having permanent magnet characteristics; and an average particle size of 50 μm by crushing the alloy
A method of producing an iron-based alloy permanent magnet powder, the method comprising: forming a powder having a particle size of 300 μm or less and having a minor axis size to a major axis size of 0.3 to 1.0. . 2. The method for producing an iron-based alloy permanent magnet powder according to claim 1, further comprising a step of roughly crushing the rapidly solidified alloy before the heat treatment. 3. The method for producing an iron-based alloy permanent magnet powder according to claim 1, wherein the pulverization is performed by a pin mill device. 4. The rapidly solidified alloy comprises Fe ₂₃ B ₆ , Fe ₃ B, R ₂ Fe ₁₄ B, and R ₂ before the heat treatment.
The method for producing an iron-based alloy permanent magnet powder according to claim 1, containing at least one metastable phase selected from the group consisting of Fe ₂₃ B ₃ and / or an amorphous phase. 5. The alloy having permanent magnet characteristics is Fe
_{100-xy R x B y (} R is, Pr, Nd, Dy, and Tb
A permanent magnet represented by a composition formula of at least one kind of rare earth element selected from the group consisting of: wherein x and y in the composition formula are 1 atom% ≦ x ≦ 6 atom% and 15 atoms. % ≦ y ≦ 25
Satisfies the atomic% relationship, and as the constituent phase, iron-based boride
And a compound having a R ₂ Fe ₁₄ B type crystal structure, and the average crystal grain size of each constituent phase is 150 nm or less. 6. The method according to claim 1, wherein in the cooling step, the molten metal is brought into contact with a roll rotating at a roll surface speed of 1 m / sec or more and 13 m / sec or less, thereby forming the rapidly solidified alloy. Manufacturing method of iron-based alloy permanent magnet powder. 7. The absolute pressure of the reduced pressure atmosphere is 50 kPa.
The method for producing an iron-based alloy permanent magnet powder according to claim 1 , wherein: 8. The method for producing an iron-based alloy permanent magnet powder according to claim 1, wherein the alloy crystallized by the heat treatment is a nanocomposite magnet. 9. A process of preparing the iron-based alloy permanent magnet powder manufactured by the manufacturing method of the iron-based alloy permanent magnet powder according to any one of claims 1 to 8, said iron-based alloy permanent magnet powder A method for manufacturing a bonded magnet, including a step of molding. 10. The method for producing a bonded magnet according to claim 9 , wherein the iron-based alloy permanent magnet powder is molded by a compression molding method at a filling rate of more than 80%. 11. The method for producing a bonded magnet according to claim 9 , wherein the iron-based alloy permanent magnet powder is molded with a filling rate of more than 65% by an injection molding method.