JP3078633B2 - Manufacturing method of sintered anisotropic magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an R-
The present invention relates to a method for producing a Fe-B based sintered anisotropic permanent magnet,
A kneaded product of finely crystallized R-Fe-B-based alloy fine powder and pure water as a binder is injection-molded at a temperature below freezing point, and is subjected to a dehydration treatment at a specific temperature rising rate to be mixed with the rare earth element (R) at the time of treatment The present invention relates to a method for manufacturing a sintered anisotropic magnet by injection molding, which significantly suppresses a reaction, prevents deterioration of magnetic properties, improves moldability at the time of injection molding, and obtains a sintered magnet having a three-dimensionally complex shape. .

[0002]

2. Description of the Related Art Today, small motors and actuators used for home appliances, computer peripherals, automobiles, and other applications are required to be smaller, lighter, and have higher performance. There is a demand for a three-dimensionally more complicated shaped product due to reduction in weight, weight, and thickness.

As a method for obtaining a high-performance permanent magnet having a complicated shape, a rare-earth bonded magnet formed by kneading a resin binder or the like using an Sm-Co-based magnetic material or an R-Fe-B-based magnetic material and mechanically forming the same. Or R-Fe-B
The alloy powder obtained by pulverizing the base alloy ingot and the resin binder are kneaded, injection-molded, and sintered after debinding.
-Fe-B sintered permanent magnet manufacturing method
20315, JP-A-64-28302, and JP-A-64-28303) are known.

[0004]

Generally, an intermetallic compound containing a rare earth element (R) is liable to react with elements such as O, H, C, and N. When kneading the magnetic powder and an organic binder or the like, Alternatively, the R component in the magnetic powder reacts with the binder at the time of debinding, resulting in a problem that the magnetic properties are deteriorated, and that the moldability at the time of injection molding becomes very poor, and it is difficult to obtain a complicated shape.

According to the present invention, there is provided a method for manufacturing an R—Fe—B sintered permanent magnet formed by injection molding and sintering the same, wherein deterioration of magnetic properties due to a reaction between an R component and a binder is prevented. It is an object of the present invention to provide a method for manufacturing a sintered anisotropic magnet capable of improving injection moldability to obtain a complicated shape, particularly a small product R-Fe-B based sintered anisotropic magnet.

[0006]

According to the present invention, there is provided an R-Fe-
As a result of various studies for the purpose of suppressing the reaction between the R component in the B-based magnetic powder and the binder, C, N
In place of an organic binder containing, for example, water, particularly deoxidized pure water, and kneaded with the R-Fe-B-based magnetic fine powder, and injection-molded in a magnetic field at a specific subzero temperature, By performing the dehydration treatment at a specific heating rate, it is possible to suppress the reaction with the rare earth element (R) during the treatment, to prevent the deterioration of the magnetic properties, to improve the moldability at the time of injection molding, and to improve the three-dimensional properties. The present inventors have found that a sintered magnet having a complicated shape can be obtained, and particularly when the product dimensions are 8 mm or less in diameter and 5 mm or less in height, the dewatering treatment is easy and is most suitable for a small product.

That is, the present invention relates to a method for producing a compound comprising R (where R is at least one of rare earth elements including Y) of 8 atomic% to 30 atomic%.
Atomic%, Fe 42 atomic% to 90 atomic%, B2 atomic% to 2
A kneaded product composed of fine powder having an average particle size of 1 to 5 μm containing 8 atomic% as a main component and pure water as a binder is −3 ° C.
Injection molding is performed in a magnetic field at a mold temperature of −15 ° C., and the obtained molded product is heated to −3 ° C. to −10 ° C. in a vacuum of 1 × 10 ⁻³ Torr or less.
This is a method for producing a sintered anisotropic magnet, comprising dehydrating to 100 ° C. at a rate of 5 to 15 ° C./hour, followed by sintering and heat treatment.

Reasons for Limiting Composition Rare earth element R used in the magnet alloy powder and permanent magnet of the present invention is at least one of Nd, Pr, Ho, and Tb.
Species or even La, Sm, Ce, Er, Eu, P
Those containing at least one of m, Tm, Yb, and Y are preferable.

If R (where R is at least one of the rare earth elements including Y) is less than 8 atomic%, the crystal structure becomes a cubic crystal structure identical to that of α - iron, so that high magnetic properties, especially high coercive force, When the content exceeds 30 atomic%, an R-rich non-magnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet having excellent characteristics cannot be obtained. Therefore, R is in the range of 8 at% to 30 at%.

If B is less than 2 atomic%, a rhombohedral structure is obtained, and a high coercive force (iHc) cannot be obtained. If it exceeds 28 atomic%, B-rich nonmagnetic phase increases, and the residual magnetic flux density (Br) decreases. As a result, an excellent permanent magnet cannot be obtained. Therefore, B is in the range of 2 to 28 atomic%.

If Fe is less than 42 at%, the residual magnetic flux density (Br) decreases, and if it exceeds 90 at%, a high coercive force cannot be obtained. Therefore, Fe is contained at 42 to 90 at%. Further, in the present invention, substituting a part of Fe with Co can improve the temperature characteristics without impairing the magnetic characteristics of the obtained magnet.
If the value of e exceeds 50%, the magnetic properties are undesirably deteriorated.

At least one of the following additional elements is added to the Fe-BR-based permanent magnet because it is effective in improving the coercive force and the like, improving the productivity, and reducing the price. However, since the residual magnetic flux density (Br) decreases with the addition for improving the coercive force, the addition is desirably performed in a range that is equal to or more than the residual magnetic flux density of the conventional hard ferrite magnet. However, when two or more kinds are contained, the maximum content of the additive element having the largest value among the additive elements is not more than the atomic percentage%, so that the permanent magnet can have a high coercive force. Ti 4.5 atomic% or less, Ni 4.5 atomic% or less,
V 9.5 atomic% or less, Nb 12.5 atomic% or less,
Ta 10.5 atom% or less, Cr 8.5 atom% or less, Mo 9.5 atom% or less, W 9.5 atom% or less, Mn 3.5 atom% or less, Al 9.5 atom% or less, Sb 2 0.5 atomic% or less, Ge 7 atomic% or less,
3.5 atomic% or less of Sn, 5.5 atomic% or less of Zr,
Bi 5 atomic% or less, Hf 5.5 atomic% or less, Cu
3.5 atomic% or less, Si 8 atomic% or less, S2.
0 atomic% or less, C 2 atomic% or less, Ca 8 atomic% or less, Mg 8 atomic% or less, P 3.5 atomic% or less,
O 2 atomic% or less. In addition, H, Li, N of 1 atomic% or less
a, K, Be, Sr, Br, Ag, Zn, N, F, S
e, Te, Pb.

Production Conditions of Fine Powder In the present invention, R-particles having an average particle size of 1 to 5 μm are used.
The method for producing the Fe-B-based alloy fine powder may be any known method such as a melting method and a super-quenching method. If the average particle size of the obtained alloy fine powder is less than 1 μm, the amount of the binder to be kneaded is increased to 1: 1.2 by volume ratio with the alloy powder in order to increase the surface area of the alloy powder. It is not preferable because the sintered density of the sintered product after injection molding is reduced to about 95%, and the average particle diameter exceeding 5 μm is too large and the sintered density is about 95% and saturated. And
It is not preferable because the density cannot be improved.

Pure Water In the present invention, pure water is used as a binder. In order to suppress the reaction with R, it is preferable to use deoxidized pure water. Further, in order to improve the strength of the injection molded body, a small amount of a water-soluble polyethylene glycol or acrylic binder can be added to pure water. The amount of pure water to be added is preferably 0.9 to 1.1 with respect to the alloy powder 1 in terms of volume ratio, and if it is less than 0.9, the fluidity of the kneaded material during injection molding becomes poor. This is not preferable because the sintering density is reduced to about 95%.

Injection molding conditions Injection conditions vary depending on the amount of pure water added, but the mold temperature is preferably from -3 ° C to -15 ° C. If the temperature is less than -15 ° C, the fluidity of the kneaded material is poor. If the temperature exceeds ℃, the solidification is insufficient at the time of removal after molding, and there is a possibility of deformation. If the injection molding pressure is less than 30 kg / cm ² , welding occurs and the molding density becomes non-uniform, bending or swelling occurs after sintering, and if it exceeds 50 kg / cm ² , burrs occur, which is not preferable. Therefore, the pressure is preferably 30 to 50 kg / cm ² . If the magnetic field during injection molding is less than 10 kOe, the orientation is insufficient, so that injection molding in a magnetic field of 10 kOe or more is preferred.

Dehydration Treatment In the dehydration treatment which is a feature of the present invention, the temperature raising temperature varies depending on the selected amount of pure water to be added.
It is necessary to raise the temperature from 3 ° C. to 100 ° C. at 5 to 15 ° C./hour, and if it is less than 5 ° C./hour, the treated product may be oxidized. Undesirably, the processed product cracks and cracks due to evaporation. In particular, when the processed product is small, at least 5 ° C
The rate of temperature rise up to 100 ° C is preferably 5 to 15 ° C / hour, and the dehydration treatment can be further simplified. Also, most of the water evaporates during the temperature rise to 100 ° C.
No treatment in the temperature range exceeding ℃ is required. The reason why the dehydration atmosphere is performed in a vacuum of 1 × 10 ⁻³ Torr or less is as follows.
This is for performing the treatment continuously from a low temperature to a high temperature,
It is also for suppressing oxidation of the R-Fe-B-based alloy powder. After the dehydration treatment, it is preferable to perform sintering by heating and heating continuously, and the heating rate after exceeding 100 ° C. may be arbitrarily selected, for example, 100 to 300 ° C. /
For example, a known temperature raising method used for sintering, such as time, can be adopted.

In the present invention, for cooling the mold, a cooling container containing a refrigerant such as a saline solution is attached for cooling, and a cooler using a so-called heat pipe can be used. In addition, 100 ° C from below freezing point in the dehydration process
If a refrigeration heating device using a heat pipe is used to raise the temperature up to, the temperature can be adjusted to an arbitrary temperature by controlling the temperature of the refrigerant from outside the vacuum chamber.

The sintering of the molded article after the dehydration treatment and the heat treatment conditions after the sintering are appropriately selected according to the selected alloy powder composition. The conditions may be the same. As preferred sintering and heat treatment conditions after sintering, a sintering step of holding at 1000 to 1180 ° C for 1 to 2 hours and an aging step of holding at 450 to 800 ° C for 1 to 8 hours are preferable.

[0019]

According to the present invention, the kneading of a magnet alloy powder with pure water as a binder and injection molding into a required shape below the freezing point improve the moldability at the time of the injection molding, resulting in a three-dimensionally complex structure. A sintered magnet having a specific shape can be obtained, and by subjecting the obtained molded body to a dehydration treatment at a specific heating rate, the reaction with the rare earth element (R) during the treatment is significantly suppressed, and at the same time, C is added to the binder. Since it does not contain, it is possible to prevent deterioration of the magnetic properties, and it is possible to obtain a sintered anisotropic magnet having a complicated shape and excellent magnetic properties. The present invention
Since pure water is used as the binder, the temperature inside the screw of the kneading and injection molding machine can be kept at room temperature, remarkably suppressing the reaction with the rare earth element (R), and recycling the spools and runners attached to the molded body. Excellent in nature. In particular, in the case of a small product, since the dehydration treatment temperature can be set to 5 to 100 ° C., the process can be simplified and there is an advantage of high industrial value.

[0020]

EXAMPLE Example 16.5 at% of Nd and 5.7 at% of B as R, the balance being a button-shaped ingot alloy produced by high-frequency heating and melting an alloy lump composed of Fe and unavoidable impurities in Ar gas was roughly pulverized. Thereafter, fine powder having an average particle size of 3 μm obtained by finely pulverizing by jet mill pulverization and pure water are mixed at a volume ratio of 1: 1 and kneaded at 30 ° C. for 10 minutes to obtain a kneaded product for injection molding. Obtained. This kneaded material is injection-molded in a mold cooled to -8 ° C. in a magnetic field strength of 15 kOe, and is 10 mm long × 10 m wide.
A flat injection-molded article of mx 5 mm in height was obtained.

Next, the injection molded body is subjected to a binder removal treatment in which the temperature is raised from -1 ° C. to 100 ° C. at a rate of 6 ° C./hour in a vacuum of 3 × 10 ^-4 Torr, followed by further heating. And kept at 1100 ° C. for 1 hour for sintering. After the completion of sintering, Ar gas was introduced and cooled to 800 ° C. at a rate of 7 ° C./min, and then cooled at 100 ° C./hour to 550 ° C.
An aging treatment for 2 hours was performed. No cracking or deformation was observed in the obtained sintered anisotropic magnet according to the present invention. Table 1 shows the magnet characteristics of the magnet and the measurement results of the residual oxygen content and the residual carbon content.

Comparative Example Using the fine powder having an average particle size of 3 μm of Example 1, an acrylic binder was blended at a volume ratio of 1: 1.
After heating and kneading for 0 minutes to obtain a kneaded product for injection molding,
Injection molding was performed in a mold heated to 0 ° C. at a magnetic field strength of 15 kOe to obtain a flat injection molded body having a length of 10 mm × a width of 10 mm × a height of 5 mm. Injection molded body is 3 × 10 ^-4 Torr
After performing a debinding treatment in which the temperature was raised to 350 ° C. at a rate of 6 ° C./hour in a vacuum, sintering and heat treatment were performed under the same conditions as in Example 1 to obtain a sintered anisotropic magnet. Table 1 shows the measurement results of the magnet properties and the residual oxygen content and the residual carbon content of the obtained comparative example magnet.

[0023]

[Table 1]

[0024]

According to the present invention, R-R having an average particle size of 1 to 5 .mu.m
By kneading the Fe-B-based alloy fine powder and pure water and injection-molding this into a required shape at a specific freezing point, the formability during injection molding is improved, and sintering of a three-dimensionally complex shape is performed. A magnet can be obtained, and the obtained molded body is subjected to a dehydration treatment at a specific heating rate, whereby a rare earth element (R)
, And in particular, the amount of residual carbon is significantly reduced to prevent deterioration of magnetic properties, and a sintered anisotropic magnet having a complicated shape and excellent magnetic properties can be obtained.

Claims (1)

(57) [Claims] 1. An average mainly composed of 8 atomic% to 30 atomic% of R (where R is at least one of rare earth elements including Y), 42 atomic% to 90 atomic% of Fe, and 2 atomic% to 28 atomic% of B. A kneaded product composed of fine powder having a particle size of 1 to 5 μm and pure water as a binder is injection-molded in a magnetic field at a mold temperature of −3 ° C. to −15 ° C., and the obtained molded product is 1 × 10 ^−3. To
Temperature rise rate from -3 ° C to 100 ° C in vacuum of rr or less 5
A method for producing a sintered anisotropic magnet, comprising dehydrating at １５15 ° C./hour, followed by sintering and heat treatment.