JP3101800B2 - Manufacturing method of anisotropic sintered permanent 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.

[0005] In the direction in which an orientation magnetic field is applied to the magnet powder filled in the cavity, there are a vertical magnetic field forming in which a magnetic field is applied in a direction parallel to the direction of pressure application by the upper and lower punches, and a horizontal magnetic field forming in which a magnetic field is applied in the vertical direction. There is. 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.

[0006]

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 a large disturbance in the orientation near 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)

According to the invention of Japanese Patent Application No. Hei 7-15093, a magnetic pole appears on the surface of a molded body by using all or at least a part of a die member of a die, an upper punch and a lower punch with a metal material having magnetism. 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, especially the orientation near the surface of the sintered block is remarkably improved, so that the residual magnetic flux density of the magnet is remarkably improved, and Magnet production yield by cutting from blocks has also been greatly improved. However, in particular, when a magnetic metal material is used for the upper punch and the lower punch, since magnetization remains in the punch, magnetic field molding is performed once, and then the obtained molded body is taken out of the die and subjected to the next molding. When the magnet powder is supplied into the cavity for the purpose, it is difficult to uniformly fill the cavity with the magnet powder, and the filling density tends to be uneven. For this reason, the density of the compact when molding is performed also becomes uneven, and if the sintering is performed as it is, the shrinkage due to sintering is greater in a portion having a smaller compact density than a portion having a higher compact density, The shape of the sintered body was distorted, resulting in a decrease in yield. 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.

[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. , At least the tip portions of the upper punch and the lower punch are formed of a die, the upper punch, and the lower punch as a metal material having a magnetization of 4πIs of 500 to 12,000 gauss and a remanence of 4πIr of 6000 gauss or less. A permanent magnet powder is supplied into a mold cavity, a magnetic field for orienting the direction of easy magnetization of the permanent magnet powder is applied, and further compaction is performed to perform molding. This is a method for producing an anisotropic sintered magnet, in which the permanent magnet powder is an R-Fe-B-based or R-Co-based rare earth permanent magnet powder.

The material of at least the tip of the upper punch and the lower punch has a saturation magnetization of 4πIs of 500 to 1200.
In order to select a metal material having a magnetic property of 0 gauss, it is necessary to prevent the appearance of magnetic poles on the surface of the molded body, to make the distribution of magnetic flux in the cavity space uniform, and to make the direction of the magnetic flux as parallel as possible. become. Thereby, the orientation of the anisotropic sintered magnet, especially the orientation near the surface of the sintered block is remarkably improved, whereby the residual magnetic flux density of the magnet is remarkably improved. The yield of magnet production by cutting will be greatly improved.

Further, the residual magnetization 4πIr of the magnetic metal material at least at the tip portions of the upper punch and the lower punch is 60.
Since it is not more than 00 Gauss, the magnet powder can be uniformly filled in the cavity when the magnet powder is supplied into 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. A sintered body having an irregular shape is not manufactured, and 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, the saturation magnetization 4πIs of a magnetic metal material used as a material of at least the tip portions of the upper punch and the lower punch is set to 500 to 1200.
Limited to 0 Gauss. Even within this range, in particular, 1500
It is preferable to use a magnetic metal material having a saturation magnetization in the range of -8000 gauss, because the effect of the present invention is remarkably exhibited. When a metal material having a saturation magnetization of 4πIs of less than 500 Gauss is used, or when a nonmagnetic material is used, a magnetic pole is generated on the surface of the molded body,
Therefore, since the direction of the magnetic flux in the peripheral portion of the molded body is disturbed, the orientation of the produced molded body is also disturbed, and the resulting sintered magnet also has poor orientation and a magnet having a small residual magnetic flux density. . Further, when the saturation magnetization 4πIs is 12
If it is larger than 000 gauss, a magnetic pole opposite to that when a metal material having a saturation magnetization 4πIs of less than 500 gauss is used is generated on the surface of the compact, and as a result, the orientation of the compact is similarly disturbed. .

Further, according to the present invention, the remanent magnetization 4 of the magnetic metal material at least at the end portions of the upper punch and the lower punch is
πIr was specified to be 6000 Gauss or less. Even within this range, it is preferable that the value be 2000 Gauss or less, since the effect of the present invention is remarkably exhibited. If it is 500 Gauss or less, more preferable results can be obtained. If the value of the residual magnetization 4πIr of at least the tip portion of the upper punch and the lower punch is larger than 6000 Gauss, it becomes difficult to uniformly fill the magnet powder when supplying the magnet powder into the cavity space. Issues arise,
Not suitable. As the magnetic metal material of the present invention,
Cemented carbides and alloyed carbon steels are desirable.

Cemented carbides include WC, TiC, MoC, N
bC, TaC, Cr ₃ C _2, etc. of the IVa, Va, a carbide powder of a metal belonging to Group VIa Co, Ni, Mo, Fe, C
u, Pb, Sn, or an alloy obtained by sintering using these alloys. These are the amounts of carbon contained in the cemented carbide, the amounts of iron, cobalt, nickel, etc., and the types of additives, The magnetism changes variously depending on the amount added.
Any cemented carbide may be applied to the present invention as long as it has a predetermined magnetic property.

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. The tip portions of the upper punch and the lower punch refer to portions that come into contact with the molded body during compression molding of the upper punch and the lower punch. In the present invention, at least the tip portions of the upper punch and the lower punch need to be made of a metal material having predetermined magnetic characteristics, and only the tip portions may be made of a magnetic metal material. May be made of a magnetic metal material, but the thickness of the magnetic metal material is preferably at least 5 mm or more. In a more preferred form of the present invention, the part that enters the die when the upper and lower punches are compressed, that is, the part from the surface in contact with the molded body of the upper punch to the upper surface of the die and the part from the surface in contact with the molded body of the lower punch to the lower surface of the die And the magnetic metal material defined in the present invention. In the present invention, both the upper punch and the lower punch need to have at least the tip portion made of a magnetic metal material, and when only one of the upper punch and the lower punch is made of a magnetic metal material, the other is used. This is unsuitable because a magnetic pole is generated on the surface of the molding on the side and the effect of the present invention does not appear.

In the present invention, a sufficient effect is obtained even when forming a horizontal magnetic field, but the effect is particularly large when forming a vertical magnetic field. In the present invention, not only the upper punch and the lower punch, but also the die, is preferably made of a metal material having a saturation magnetization of 4πIs of 500 to 12,000 gauss and a residual magnetization of 4πIr of 6000 gauss or less. As a result, the effect of suppressing the generation of magnetic poles on the surface of the compact is more remarkably exhibited, and the supply of the magnet powder into the cavity can be performed more uniformly. Examples of the anisotropic sintered magnet that is an object of the present invention include ferrite magnets such as Ba ferrite and Sr ferrite, R—Co, and R—Fe.
Although there are rare-earth magnets such as -B series, particularly when the present invention is applied to the production of a rare-earth magnet, the effect of the present invention is remarkably exhibited, so that preferable results 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.

The R-Fe-B rare earth magnet is usually 5 to 40% of R, 50 to 90% of Fe, 0.1 to 0.5% 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.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The function of the present invention is to provide a mold in which at least the tip portions of an upper punch and a lower punch are formed of a metal material having magnetism, a die, an upper punch, and a lower punch in a step of forming an anisotropic magnet. Supplying permanent magnet powder into the cavity, applying a magnetic field for orienting the magnetization direction to the powder, compressing and molding,
As a result, it is possible to prevent the magnetic poles from appearing on the surface of the molded body, to make the distribution of the magnetic flux uniform, and to make the direction of the magnetic flux parallel. Further, the permanent magnet powder can be uniformly filled in the cavity. Therefore, an anisotropic sintered magnet with improved residual magnetic flux density can be manufactured with high yield.

[0021]

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. For the upper punch and the lower punch, a portion 50 mm from the tip was made of a cemented carbide or alloy carbon steel having various saturated magnetizations 4πIs and residual magnetizations 4πIr as shown in Table 1. 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 compact is 30 mm. The cross-sectional shape of the cavity in a direction perpendicular to the compression direction is 30 mm × 20 mm. The magnetic field application direction is a direction parallel to the 20 mm side of the molded body.

These compacts are placed in a 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.

[0024]

[Table 1]

(Embodiment 2) The same R-Fe-
The B-based magnet alloy powder was supplied into the cavity, a magnetic field of 18 kOe was applied by an electromagnet, and a vertical magnetic field was formed by applying a pressure of 1.2 ton / cm ^{2 in} a direction parallel to the magnetic field application direction. The portion 30 mm from the tip of the upper punch and the lower punch has a saturation magnetization 4πIs of 3500 gauss and a residual magnetization of 4500 gauss.
It is made of cemented carbide of πIr300 Gauss. The height of the produced molded body was 50 mm, and the cross-sectional shape in the direction perpendicular to the compression direction of the cavity was 30 mm × 30.
mm.

The obtained compact was subjected to sintering and aging heat treatment under the same conditions as in Example 1 to produce a sintered magnet. This sintered body did not show any distortion in its shape, and its residual magnetic flux density Br was 12.09 kG. As a comparative example,
The entire upper and lower punches are made of non-magnetic cemented carbide,
Similarly, when a sintered magnet was manufactured, the shape of the sintered body was distorted, and its residual magnetic flux density Br was 11.84 k.
G.

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 upper punch and the lower punch were entirely made of cemented carbide or alloyed carbon steel having various saturation magnetizations 4πIs and residual magnetizations 4πIr as shown in Table 2. A magnet powder is supplied into the cavity, and a magnetic field of 15 kOe is applied by an electromagnet.
The molding was performed by applying a pressure of 8 ton / cm ² . The height of the formed compact is 30 mm. The cross section of the cavity in a direction perpendicular to the compression direction is 30 mm × 20 m.
m. The magnetic field application direction is a direction parallel to the 20 mm side of the molded body. This molded body was placed under an argon atmosphere for 12 hours.
Sintered at 00 ° C and solution-solutioned at 1180 ° C. Aging heat treatment is first held at 850 ° C for 2 hours as aging, then at 1 ° C
The sample was continuously cooled to 400 ° C. at a cooling rate of / min, 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.

[0028]

[Table 2]

[0029]

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

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01F 41/02 B22F 3/02

Claims (2)

(57) [Claims] In a molding process for manufacturing an anisotropic sintered magnet, at least the tip portions of an upper punch and a lower punch have a magnetic property of a saturation magnetization 4πIs of 500 to 12,000 gauss and a remanence magnetization 4πIr of 6000 gauss or less. As a material, a permanent magnet powder is supplied into a cavity of a die constituted by a die, the upper punch and the lower punch, a magnetic field for orienting the easy magnetization direction of the permanent magnet powder is applied, and further compressed. 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.