JP3101798B2 - Manufacturing method of anisotropic sintered magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing an anisotropic sintered magnet.

[0002]

2. Description of the Related Art Ferrite magnets such as Ba ferrite and Sr ferrite magnets and RC
Rare-earth magnets such as o-based and R-Fe-B-based are widely used, but in recent years, the use of rare-earth magnets as high-performance magnets has been rapidly increasing. In these anisotropic sintered magnets, the direction of easy magnetization of each crystal grain that bears magnetism is aligned in a certain direction, and therefore, the direction of easy magnetization of crystal grains is oriented in different directions. Compared with an isotropic magnet, when magnetized in its easy magnetization direction, the value of the residual magnetic flux density is large, and therefore, the maximum energy product can be increased. Further, since it is a sintered magnet, the amount of the non-magnetic substance is smaller than that of a bonded magnet bonded with a resin or the like, so that the value of the residual magnetic flux density is increased and the maximum energy product can be increased. Therefore, anisotropic sintered magnets are widely used because they can obtain the largest maximum energy product among magnets using the same material.

[0003] Anisotropic sintered magnets are made by pulverizing the material until each pulverized powder becomes a single crystal in order to align the direction of easy magnetization of the magnetic crystal grains to a certain direction, and apply the external powder to the pulverized powder. By applying a magnetic field, the axis of easy magnetization of the magnet powder is aligned in a direction parallel to the direction of the external magnetic field, and compressed and molded by applying pressure. Then, the formed magnet powder is sintered under predetermined conditions to produce an anisotropic sintered magnet. Depending on the material, heat treatment may be required after sintering. For example, R ₂
After sintering, the Co ₁₇ magnet is subjected to a solution treatment and then an aging treatment. For the R-Fe-B magnet, after sintering, 5
The magnet is manufactured by performing heat treatment at around 00 ° C.

[0004] The magnetic field press used in the molding process includes a die, an upper punch, a lower punch, and a magnetic field generating means. Magnet powder is supplied into a cavity composed of a die, an upper punch and a lower punch, and an orientation magnetic field is applied by a magnetic field generating means to align the direction of easy magnetization of the magnet powder in one direction. To form the magnet powder in the cavity. In general, molding is performed by applying a static magnetic field with an electromagnet or the like, and the static magnetic field is applied.However, the static magnetic field using an electromagnet limits the size of the magnetic field obtained. In some cases, a pulse magnetic field generated by an air-core coil is used as the magnetic field generating means. When a pulse magnetic field is used, a magnet powder is supplied into the cavity, a pulse magnetic field is applied, and then molding is performed. However, the generation of a pulsed magnetic field causes significant problems such as heat generation of the coil, which is not preferable as a production method. The direction in which the orientation magnetic field is applied to the magnet powder filled in the cavity includes vertical magnetic field molding in which a magnetic field is applied in a direction parallel to the direction of pressure application by the upper and lower punches, and horizontal magnetic field molding in which a magnetic field is applied in the vertical direction. Whether to select horizontal magnetic field molding or vertical magnetic field molding is determined by the material, properties, shape, magnetization direction, etc., to be manufactured. Since magnetic properties are lower than in the case, transverse magnetic field shaping is often used.

[0005]

When a magnet is manufactured by applying a magnetic field to perform molding and sintering, magnetic properties may vary depending on each portion of one sintered body.
In particular, the residual magnetic flux density is significantly deteriorated on the surface of the sintered magnet as compared with the central portion, which is considered to be due to the large disturbance of the orientation on the surface. If the orientation is disturbed in the vicinity of the surface and the residual magnetic flux density is deteriorated, the residual magnetic flux density of the entire sintered body becomes low. Such a phenomenon appears particularly remarkably when the size of the sintered body is small. In particular, in recent years, the size of electronic and electric devices that use anisotropic sintered magnets has become smaller, and the size of anisotropic sintered magnets has become smaller and thinner. Is becoming impossible to ignore. In addition, when manufacturing small magnets, large sintered blocks may be cut and manufactured, but magnets cut from near the surface often have low residual magnetic flux density and cannot be used, This is causing a decrease in yield.

As a means for solving the above-mentioned problems, the present inventors have effective that all or at least a part of the die member of the die, the upper punch, and the lower punch is made of a magnetic metal material. And has already proposed. (Japanese Patent Application 7-151093)

The invention of Japanese Patent Application No. Hei 7-15093 discloses that a magnetic pole appears on the surface of a molded product by using a metal material having magnetism for all or at least a part of a die, an upper punch and a lower punch. To make the distribution of the magnetic flux in the cavity space uniform and to make the direction of the magnetic flux as parallel as possible.

As a result, the orientation of the anisotropic sintered magnet, particularly in the vicinity of the surface of the sintered block, is remarkably improved, whereby the residual magnetic flux density of the magnet is remarkably improved. Magnet production yield by cutting from blocks has also been greatly improved.

However, in particular, when a magnetic metal material is used for the die, since magnetization remains in the die, magnetic field molding is performed once, and then the obtained molded body is taken out from the die and subjected to the next molding. Therefore, when the magnet powder is supplied into the cavity, troubles such as the magnet powder adhering to the die are likely to occur. When such a situation occurs, it is difficult to uniformly fill the cavity with the magnet powder, and the filling density is likely to be uneven. As a result, the density of the molded body after molding is uneven,
If sintering is performed as it is, the shape of the sintered body will be distorted due to the large shrinkage due to sintering in the low density part compared to the high density part, resulting in a decrease in yield. I was In order to prevent this, it was necessary to manufacture permanent magnets larger than the designed magnet shape and process them until they became the specified shape. Improvement was requested. In addition, if the magnet powder adheres to the die, the efficiency of the molding operation may be significantly deteriorated.

[0010]

Means for Solving the Problems The present inventors have made intensive efforts to solve the above problems, and as a result, have completed the present invention. In the above, the saturation magnetization 4πIs is 500 to 120.
A permanent magnet is formed in a cavity of a die including the die, the upper punch, and the lower punch by using a metal material having a magnetic property of 00 gauss and setting the magnetization 4πI of the die to 6000 gauss or less when supplying the permanent magnet powder into the cavity. A method for producing an anisotropic sintered magnet, comprising supplying a powder, applying a magnetic field for orienting the direction of easy magnetization of the permanent magnet powder, and further compacting the molded product. This is a method for producing an anisotropic sintered magnet in which the permanent magnet powder is an R-Fe-B or R-Co rare earth permanent magnet powder.

As described above, in the anisotropic magnet, the value of the residual magnetic flux density is increased by aligning the easy magnetization directions of the magnetic crystal grains constituting the magnet.
The method of aligning the easy magnetization direction affects the quality of the orientation of the finally obtained anisotropic sintered magnet. During the molding process, the orientation disturbance due to the compression pressure is suppressed by the strength of the orientation magnetic field and the magnitude of the anisotropic magnetic field of the magnet powder, but the direction of the orientation magnetic field in the cavity space becomes clear and parallel. Otherwise, the directions of easy magnetization of the magnet powder are not aligned in parallel. For this reason, the magnetic field distribution in the cavity when the magnet powder of the anisotropic sintered magnet is oriented by the orientation magnetic field has a great influence on how to easily align the magnetization direction of the magnet powder.

Generally, when a magnetic field is applied to a magnetic material,
Magnetic poles appear at both ends of the magnetic body, and the magnetic flux inside the magnetic body has a large magnetic flux density at the center of the magnetic body and the direction of the magnetic flux is uniform, but at the peripheral part inside the magnetic body, the magnetic flux density is at the center. And the direction of the magnetic flux is also non-uniform. In particular, in the portion where the magnetic pole appears, such a decrease in the magnetic flux density, non-uniformity, and disturbance in the magnetic flux direction are remarkable. FIG. 1 shows this state. Such a phenomenon,
It also appears in the compact during molding in a static magnetic field, a magnetic pole is generated on the surface of the compact, and the magnetic field distribution inside the compact is considered to be as shown in FIG. Thus, it is considered that the magnetic pole is generated on the surface of the molded body and the magnetic field distribution inside the molded body is disturbed, thereby causing the above problem.

According to the present invention, the dice has a saturation magnetization of 4πIs.
Is made of a metal material having a magnetism of 500 to 12,000 gauss, and a magnetic powder is supplied into the cavity space to form a magnetic field, so that the die and the formed body can be regarded as one magnetic body. Therefore, when the orientation magnetic field is applied, the magnetic pole appears on the surface of the die opposite to the surface in contact with the molded body of the magnetic metal material, and does not appear on the surface of the molded body. Therefore, the reduction and non-uniformity of the magnetic flux density near the magnetic pole and the disturbance in the magnetic flux direction are concentrated on the metal material having magnetic properties of the die, and the effect of the magnetic pole on the molded body is reduced, and the magnetic flux density is reduced. Is large and uniform,
The directions of the magnetic flux are parallel.

Therefore, by applying the present invention, the magnetic flux density in the cavity space at the time of molding is uniform and large, and its direction is neatly aligned with the direction in which the magnetic field is applied. Since each particle of the powder is oriented in the direction of easy magnetization and along the magnetic flux having a high density and a uniform direction, the resulting compact has a high degree of orientation, and as a result, a magnet having a high residual magnetic flux density Can be obtained. Also, when a magnet is manufactured by cutting a large sintered block, the magnet cut out from near the surface does not show any deterioration in characteristics, and the yield is remarkably improved.

Furthermore, since the magnetization 4πI remaining in the die when supplying the magnet powder into the cavity space is 6000 gauss or less, the magnet powder adheres to the die when the magnet powder is supplied into the cavity. Therefore, no troubles such as inconvenience occur, so that the magnet powder can be uniformly filled in the cavity. Therefore, not only the working efficiency at the time of molding is improved, but also the filling density in the cavity is uniform, so that the density of the molded body is also uniform, so that there is no variation in shrinkage during sintering. Irregular shaped sintered body is not manufactured,
The shape of the sintered body can be made as designed. For this reason, the production yield is improved, the processing allowance can be reduced, and the material yield is also improved. In the present invention, when the magnetic field is formed, the dice has a saturation magnetization of 4.
It is characterized by being made of a metal material having magnetism of πIs of 500 to 12,000 gauss, and having a magnetization of 4πI of the die of 6000 gauss or less when the permanent magnet powder is supplied into the cavity.

In the present invention, the saturation magnetization 4πIs of the magnetic metal material used as the die material is set to 50.
It was limited to 0 to 12000 gauss. Even within this range, it is particularly preferable to use a magnetic metal material having a saturation magnetization in the range of 1500 to 8000 Gauss, because the effect of the present invention is remarkably exhibited. Saturation magnetization less than 500 Gauss 4πI
If a metal material having s is used, or if it is made of a non-magnetic material, a magnetic pole will be generated on the surface of the molded body, so that the magnetic flux in the peripheral portion of the molded body is disturbed in the direction, The orientation of the manufactured compact is also disturbed, and the resulting sintered magnet also has poor orientation and is a magnet having a low residual magnetic flux density. In addition, the saturation magnetization 4π
When Is is larger than 12000 gauss, a magnetic pole opposite to that when a metal material having a saturation magnetization of 4π Is less than 500 gauss is generated on the surface of the molded body, and as a result,
Similarly, the orientation of the molded product is disturbed.

In the present invention, not only the die but also the upper punch and the lower punch have a saturation magnetization 4πIs of 50.
It is preferable to use a metal material having a magnetism of 0 to 12,000 gauss, because the effect of suppressing the generation of magnetic poles on the surface of the molded product is more remarkably exhibited. At this time, the whole of the upper punch and the lower punch may be made of a magnetic metal material, but only a tip portion in contact with the molded body may be made of a magnetic metal material.

The magnetic metal material of the present invention includes:
Cemented carbides and alloyed carbon steels are desirable. What is cemented carbide?
C, TiC, MoC, NbC, TaC, Cr ₃ C ₂ etc.
Co, a carbide powder of a metal belonging to the group IVa, Va, VIa;
Ni, Mo, Fe, Cu, Pb, Sn, or an alloy obtained by sintering using alloys thereof, and these are the amounts of carbon contained in the cemented carbide and the amounts of iron, cobalt, nickel, etc. Further, the magnetism changes variously depending on the kind and amount of the additive. If it has the predetermined magnetic properties,
Any cemented carbide may be applied to the present invention.

The alloy carbon steel is an alloy mainly composed of Fe—C, and it is particularly preferable to use die steel, carbon tool steel, alloy tool steel, high-speed steel, or the like. Any alloy carbon steel may be used as long as it has a predetermined magnetic property.

In the present invention, it is necessary that the magnetization 4πI of the die when the permanent magnet powder is supplied into the cavity is 6000 gauss or less. Even within this range, it is preferable that the magnetization 4πI of the die be 2000 gauss or less when the permanent magnet powder is supplied into the cavity, since the effect of the present invention is remarkably exhibited. Further, if it is 500 Gauss or less, more preferable results can be obtained. Die magnetization 4π when supplying permanent magnet powder into cavity
When I is larger than 6000 gauss, when the magnet powder is supplied into the cavity, troubles such as the magnet powder adhering to the die are liable to occur, and the above-mentioned problem occurs. is there.

In order to reduce the magnetization 4πI of the die when supplying the permanent magnet powder into the cavity to 6000 gauss or less, the saturation magnetization 4πIs of the die material should be 500-12.
There is a method of using a metal material having magnetism of 000 gauss and having a residual magnetization 4πIr of 6000 gauss or less, and demagnetizing the dice before supplying the magnet powder into the cavity. When degaussing is performed before supplying the magnet powder, there is no problem in applying either of the DC degaussing and the AC degaussing. Examples of the anisotropic sintered magnet that is the object of the present invention include ferrite magnets such as Ba ferrite and Sr ferrite magnets, and R-ferrite magnets.
There are rare earth magnets such as Co-based and R-Fe-B-based. However, if the present invention is applied particularly when manufacturing a rare-earth magnet, the effect of the present invention is remarkably exhibited, and thus a favorable result can be obtained. These magnets are manufactured as follows.

R-Co based rare earth magnets are RCo ₅ based, R
_Although there is a ₂ Co ₁₇ system and the like, most practically used are R ₂ Co ₁₇ systems. R ₂ Co ₁₇ based rare earth magnets are usually 20 to 28% R, 5 to 30% by weight.
% Fe, 3-10% Cu, 1-5% Zr, balance C
o, and is manufactured by the following manufacturing method. First, a raw metal is weighed, melted and cast, and the obtained alloy is finely pulverized to an average particle size of 1 to 20 μm to obtain an R ₂ Co _17- based rare earth permanent magnet powder. R ₂ Co ₁₇ rare earth permanent magnet powder is formed in a magnetic field according to the present invention,
It is sintered at １２1250 ° C. for 0.5-5 hours, then solution-hardened at 0-50 ° C. below the sintering temperature for 0.5-5 hours, and finally subjected to an aging treatment. In the aging treatment, the first-stage aging is usually held at 700 to 950 ° C. for a certain period of time, followed by continuous cooling or multi-stage aging.

R-Fe-B rare earth magnets are usually 5 to 40% of R, 50 to 90% of Fe, 0.5 to 90% by weight.
Consists of 2-8% B. To improve magnetic properties,
C, Al, Si, Ti, V, Cr, Mn, Co, Ni,
Cu, Zn, Ga, Zr, Nb, Mo, Ag, Sn, H
In many cases, additional elements such as f, Ta, and W are added. The amount of these additives is usually 30% by weight or less for Co, and 8% by weight or less for other elements.
Addition of more additives causes the magnetic properties to deteriorate. The method for producing the R-Fe-B rare earth magnet is as follows. The raw metal is weighed, melted and cast, and the obtained alloy is finely pulverized to an average particle size of 1 to 20 μm.
An Fe-B rare earth permanent magnet powder is obtained. The R-Fe-B-based rare earth permanent magnet powder is formed in a magnetic field according to the present invention, and sintered at 1000 to 1200C for 0.5 to 5 hours. Finally, aging treatment is performed at 400 to 1000 ° C.
An Fe-B based rare earth magnet is obtained.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The function of the present invention is to provide a method in which a die is made of a magnetic metal material in a molding step of an anisotropic sintered magnet, and the die is formed in a cavity of a mold comprising an upper punch and a lower punch. A permanent magnet powder is supplied, a magnetic field for orienting the direction of easy magnetization is applied to the powder, and the powder is compacted and compacted, thereby preventing the appearance of magnetic poles on the surface of the compact and reducing the magnetic flux. The distribution can be made uniform and the direction of the magnetic flux can be made parallel. further,
The cavity can be uniformly filled with the permanent magnet powder. Therefore, an anisotropic sintered magnet with improved residual magnetic flux density can be manufactured with high yield.

[0025]

EXAMPLES Hereinafter, embodiments of the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto. (Example 1, Comparative Example) Nd _13.8 Dy ₁ Fe _{73.7 in} atomic%
An alloy of Co ₄ B _6.5 Al ₁ was melted and cast in an argon atmosphere using an induction heating high-frequency melting furnace with each raw material metal having a purity of 99.9 wt% or more to prepare an alloy ingot. This alloy ingot was placed in an argon atmosphere at 1100 ° C. × 24
After performing the homogenization heat treatment for a time, coarse grinding is performed using a jaw crusher and a brown mill in an argon atmosphere, and then fine grinding is performed using a jet mill using nitrogen gas.
An R—Fe—B-based magnet powder having an average particle size of 5 μm was prepared.

Molding was performed using this magnet powder. The dies used for molding had various saturation magnetizations 4 as shown in Table 1.
Cemented carbide or alloyed carbon steel having πIs and residual magnetization of 4πIr was used. Magnet powder was supplied into the cavity, a magnetic field of 15 kOe was applied by an electromagnet, and molding was performed by applying a pressure of 1 ton / cm ^{2 in} a direction perpendicular to the magnetic field application direction while the magnetic field was applied. The height of the formed body is 15
mm. The cross-sectional shape of the cavity in a direction perpendicular to the compression direction is 30 mm × 20 mm.

These compacts were placed in vacuum at 1060 ° C. for 9 hours.
Sintering was performed for 0 minutes, and then aging heat treatment was further performed at 540 ° C. The magnetic properties of the obtained R—Fe—B sintered magnet were measured using a BH tracer. Table 1 shows their residual magnetic flux densities. In addition, the flatness of a surface perpendicular to the orientation direction of the surface of the sintered body was also measured.

[0028]

[Table 1]

(Example 2, Comparative Example) The same magnetic alloy powder as in Example 1 was supplied into the cavity, and 10 magnets were supplied using an electromagnet.
A magnetic field of kOe is applied, and 1.
The molding was performed by applying a pressure of ² ton / cm ² . The dice had a saturation magnetization of 4πIs of 10,000 Gauss and a residual magnetization of 4
It is made of πIr 7000 Gauss alloy carbon steel.
Before filling the magnet powder into the cavity, the dies were demagnetized by AC, and the magnetization 4πI was set to 500 gauss. The height of the formed compact is 25 mm. The cross-sectional shape of the cavity in a direction perpendicular to the compression direction is 30 mm × 20.
mm. Next, sintering and aging were performed under the same conditions as in Example 1 to produce a magnet, and its magnetic properties were measured using a BH tracer, and it was 12.65 kG. The flatness of the surface perpendicular to the orientation direction of the surface of the sintered body is 0.
3 mm.

As a comparative example, when the same dies were used and the dies were not demagnetized before the magnet powder was supplied to the cavity, the result was that the residual magnetic flux density was 12.67 kG and
The flatness of the surface perpendicular to the orientation direction of the surface of the sintered body is 1.51 m
m.

Example 3 The alloy composition was Sm2 in weight%.
5.5%, Fe 14%, Cu 4%, Zr 2.5%, residual C
After weighing the raw materials so as to obtain o, they were melted and cast in an argon atmosphere using an induction heating high-frequency melting furnace to produce an alloy ingot. This alloy ingot was roughly pulverized using a jaw crusher and a brown mill in an argon atmosphere, and then finely pulverized using a jet mill using nitrogen gas to produce an R ₂ Co _17- based magnetic powder having an average particle diameter of 5 μm. .

Molding was performed using this magnet powder. The dies used for molding had various saturation magnetizations 4 as shown in Table 2.
Cemented carbide or alloyed carbon steel having πIs and residual magnetization of 4πIr was used. Magnet powder was supplied into the cavity, a magnetic field of 18 kOe was applied by an electromagnet, and molding was performed while applying a magnetic field and applying a pressure of 0.8 ton / cm ^{2 in} a direction perpendicular to the magnetic field application direction. The height of the formed compact is 25 mm. The cross-sectional shape of the cavity in a direction perpendicular to the compression direction is 30 mm × 20 mm.

This molded product was subjected to 1200 under an argon atmosphere.
C. and sintered at 1180.degree. Aging heat treatment is first held at 850 ° C. for 2 hours as aging, then at 1 ° C./m
The sample was continuously cooled to 400 ° C. at a cooling rate of “in” and then rapidly cooled. The magnetic properties of the obtained R ₂ Co ₁₇ based sintered magnet were measured using a BH tracer. Table 2 shows their residual magnetic flux densities. In addition, the flatness of a surface perpendicular to the orientation direction of the surface of the sintered body was also measured.

[0034]

[Table 2]

[0035]

According to the present invention, an anisotropic sintered magnet having a large residual magnetic flux density can be manufactured with good yield.

[Brief description of the drawings]

FIG. 1 shows a magnetic flux distribution when a magnetic field is applied to a magnetic material.

[Explanation of symbols]

 1: magnetic substance 2: magnetic flux

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-287115 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01F 41/02 B22F 3/02

Claims (2)

(57) [Claims] In a molding step for producing an anisotropic sintered magnet, a die is made of a metal material having a magnetism having a saturation magnetization of 4πIs of 500 to 12,000 gauss, and magnetization of the dice is supplied when a permanent magnet powder is supplied into a cavity. 4πI to 600
As 0 Gauss or less, the permanent magnet powder is supplied into the cavity of the die including the die, the upper punch, and the lower punch, and a magnetic field for orienting the easy magnetization direction of the permanent magnet powder is applied. A method for producing an anisotropic sintered magnet, comprising molding. 2. The permanent magnet powder according to claim 1, wherein R-
The method for producing an anisotropic sintered magnet according to claim 1, wherein the magnet is an Fe-B or R-Co rare earth permanent magnet powder.