JPH0935979A - Manufacture of anisotropic sintered permanent magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an anisotropic sintered magnet for improving residual magnetic flux density. SOLUTION: In a molding process of anisotropic sintered magnet manufacturing, at least a tip part of an upper punch and a lower punch is formed of a metallic material having saturation magnetization 4πIs of 500 to 12000G and residual magnetization 4πIr of 6000G or less, permanent magnet powder is supplied into a cavity of a molding comprised of a die, an upper punch and a lower punch, magnetic field for orienting an easy magnetization direction of permanent magnet powder is applied, compression is carried out for molding and an anisotropic sintered magnet is manufactured. Especially, this method is a manufacturing method of an anisotropic sintered magnet wherein permanent magnet powder is R-Fe-B or R-Co rare earth permanent magnet powder.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing an anisotropic sintered magnet.

[0002]

2. Description of the Related Art As anisotropic sintered magnets, ferrite magnets such as Ba ferrite type and Sr ferrite type magnets, RC
Although rare earth magnets such as o type and R-Fe-B type are widely used, the use of rare earth magnets as high-performance magnets has been rapidly increasing in recent years. In these anisotropic sintered magnets, the easy magnetization directions of the crystal grains having magnetism are aligned in a certain direction. Therefore, the easy magnetization directions of the crystal grains are in different directions. Compared with the direction magnet, the value of the residual magnetic flux density is large when magnetized in its easy magnetization direction, and therefore the maximum energy product can be increased. Further, since it is a sintered magnet, the amount of 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 large 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.

In order to align the easy magnetization direction of the magnetic crystal grains in a certain direction, the anisotropic sintered magnet pulverizes the material until each pulverized powder becomes a single crystal, and the pulverized powder is externally pulverized. By applying a magnetic field, the easy axis of magnetization of the magnet powder is aligned in a direction parallel to the direction of the external magnetic field, and pressure is applied to compress and shape. Then, the formed magnet powder is sintered under predetermined conditions to manufacture an anisotropic sintered magnet. Depending on the material, heat treatment may be required after sintering. For example, R ₂
After sintering, the Co ₁₇ system magnet is subjected to solution treatment and further aging treatment. For the R-Fe-B magnet, after sintering, 5
A magnet is manufactured by performing a heat treatment near 00 ° C.

The magnetic field press used in the molding process comprises a die, an upper punch, a lower punch and a magnetic field generating means. Magnet powder is supplied into the cavity composed of the die, upper punch and lower punch, and the magnetic field generating means applies an orientation magnetic field to align the easy magnetization direction of the magnet powder in one direction, and the upper and lower punches apply pressure. And the magnet powder in the cavity is molded. Molding is generally performed by applying a static magnetic field with an electromagnet, etc., but the static magnetic field generated by the electromagnet limits the size of the magnetic field that can be obtained. In some cases, a pulsed magnetic field generated by an air-core coil may be used as the magnetic field generating means. When a pulsed magnetic field is used, magnetic powder is supplied into the cavity, a pulsed magnetic field is applied, and then molding is performed. However, when a pulsed magnetic field is generated, there are many problems such as heat generation of the coil, which is not preferable as a production method.

In the direction in which the orientation magnetic field is applied to the magnet powder filled in the cavity, there are longitudinal magnetic field molding in which a magnetic field is applied in the direction parallel to the direction of pressure application by the upper and lower punches, and transverse magnetic field molding in which a magnetic field is applied in the vertical direction. There is. Whether to select transverse magnetic field molding or longitudinal magnetic field molding is determined by the material to be manufactured, characteristics, shape, magnetization direction, etc. Since the magnetic characteristics are lower than in the case, transverse magnetic field molding is often used.

[0006]

By the way, when a magnet is manufactured by applying a magnetic field to perform molding and sintering, magnetic characteristics may vary depending on each part of one sintered body.
In particular, the surface of the sintered magnet is significantly deteriorated in the residual magnetic flux density as compared with the central portion, and it is considered that this is because the orientation disorder is large near the surface. When the orientation is disturbed near the surface and the residual magnetic flux density is deteriorated as described above, the residual magnetic flux density becomes low as the whole sintered body. Such a phenomenon is particularly remarkable when the size of the sintered body is small. In particular, in recent years, electronic and electric devices in which anisotropic sintered magnets are used have become smaller, and the size of anisotropic sintered magnets has become smaller and thinner, resulting in deterioration of magnetic properties due to disordered orientation. Is becoming irreducible. Furthermore, when manufacturing a small magnet, a large sintered body block may be cut and manufactured, but a magnet cut out from near the surface often has a low residual magnetic flux density and cannot be used, This causes a decrease in yield.

As a means for solving the above problems, it is effective for the present inventors to use all or at least a part of the die member of the die, the upper punch and the lower punch as a metallic material having magnetism. I have already proposed it. (Japanese Patent Application No. 7-151093)

According to the invention of Japanese Patent Application No. 7-151093, magnetic poles appear on the surface of the molded body by using all or at least a part of the die member of the die, the upper punch and the lower punch as a metallic material having magnetism. This is intended to make the distribution of the magnetic flux in the cavity space uniform and to make the directions of the magnetic flux as parallel as possible.

As a result, the orientation of the anisotropic sintered magnet, in particular, the orientation in the vicinity of the surface of the sintered body block is remarkably improved, whereby the residual magnetic flux density of the magnet is remarkably improved, and the large size is large. The yield of magnet production by cutting from blocks was also greatly improved. However, especially when a magnetic metal material is used for the upper punch and the lower punch, magnetization remains in the punch, so magnetic field molding is performed once, and then the obtained molded body is taken out from the die and the next molding is performed. Therefore, when the magnet powder is supplied into the cavity, it becomes difficult to uniformly fill the cavity with the magnet powder, and the packing density tends to be uneven. Therefore, there is unevenness in the density of the molded body at the time of molding, and if the sintering is performed as it is, the shrinkage due to the sintering is larger in the portion where the molded body density is smaller than the portion where the molded body density is large, The shape of the sintered body became distorted, leading to a decrease in yield. In order to prevent this, it was necessary to manufacture permanent magnets with a size larger than the magnet shape as designed and process it until it had a predetermined shape, so the machining allowance was large and the material yield was also reduced. Improvement was requested.

[0010]

The inventors of the present invention have completed the present invention as a result of diligent efforts to solve the above-mentioned problems, and the gist thereof is the molding step for producing an anisotropic sintered magnet. In at least the tip portions of the upper punch and the lower punch, a die, the upper punch and the lower punch are formed as a magnetic metal material having a saturation magnetization 4πIs of 500 to 12000 gauss and a residual magnetization 4πIr of 6000 gauss or less. An anisotropic sintered magnet characterized in that permanent magnet powder is supplied into a cavity of a mold, a magnetic field for orienting an easy magnetization direction of the permanent magnet powder is applied, and further compression is performed to perform molding. 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.

As a material for at least the tip portions of the upper punch and the lower punch, the saturation magnetization 4πIs is 500 to 1200.
Since a metallic material having a magnetism of 0 Gauss is selected, it is possible to prevent the magnetic pole from appearing on the surface of the molded body, to make the distribution of the magnetic flux in the cavity space uniform, and to make the magnetic flux directions as parallel as possible. become. This significantly improves the orientation of the anisotropic sintered magnet, particularly the orientation near the surface of the sintered body block, which significantly improves the residual magnetic flux density of the magnet. The yield of magnet manufacturing by cutting out will also be greatly improved.

Further, the residual magnetization 4πIr of the magnetic metal material of at least the tip portions of the upper punch and the lower punch is 60.
Since it is less 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 packing density in the cavity is uniform, so that the density of the molded body is also uniform, and therefore there is no variation in shrinkage during sintering. A sintered body having a distorted shape is not manufactured, and the shape of the sintered body can be designed. Therefore, the manufacturing yield is improved, the machining allowance can be reduced, and the material yield is also improved.

In the present invention, the saturation magnetization 4πIs of the metallic material having magnetism used as the material of at least the tip portions of the upper punch and the lower punch is 500 to 1200.
Limited to 0 gauss. Even within this range, especially 1500
It is preferable to use a magnetic metal material having a saturation magnetization in the range of up to 8000 gauss, since 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 it is made of a non-magnetic material, a magnetic pole is generated on the surface of the molded body,
Therefore, the magnetic flux in the peripheral portion of the molded body is disturbed in direction, so that the orientation of the manufactured molded body is also disturbed, and the resulting sintered magnet also has poor orientation and becomes a magnet with a small residual magnetic flux density. . Further, 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 of 4πIs of less than 500 Gauss is used on the surface of the molded body, and as a result, the orientation of the molded body is also disturbed. .

Further, according to the present invention, the remanent magnetization 4 of the magnetic metal material at least at the tip portions of the upper punch and the lower punch.
πIr was defined as 6000 Gauss or less. Even within this range, it is preferable that the amount is 2000 gauss or less, because the effect of the present invention is remarkably exhibited. If it is 500 gauss or less, more preferable results can be obtained. When 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 it is supplied into the cavity space. Because there are various problems
Not suitable. As the magnetic metal material of the present invention,
Cemented carbide and alloy carbon steel are preferred.

Cemented carbide means WC, TiC, MoC, N
Carbide powders of metals belonging to the IVa, Va, and VIa groups such as bC, TaC, and Cr ₃ C ₂ are Co, Ni, Mo, Fe, and C.
An alloy obtained by sinter-bonding with u, Pb, Sn, or an alloy thereof, which contains the amount of carbon contained in the cemented carbide, the amount of iron, cobalt, nickel, etc., and the type of additive, Its magnetism changes variously depending on the amount added.
Any cemented carbide may be applied to the present invention as long as it has predetermined magnetic properties.

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 and the like. Also for these, any alloy carbon steel may be used as long as it has predetermined magnetic characteristics. The tip portions of the upper punch and the lower punch refer to portions of the upper punch and the lower punch that come into contact with the compact during compression molding. In the present invention, it is necessary that at least the tip portions of the upper punch and the lower punch are made of a metal material having predetermined magnetic characteristics, and only the tip portions may be made of a magnetic metal material, or the entire punch. May be made of a magnetic metal material, but the thickness of the magnetic metal material is preferably at least 5 mm or more. A more preferable embodiment of the present invention is that the portion that enters the die during compression of the upper and lower punches, that is, the portion from the surface in contact with the molded body of the upper punch to the upper surface of the die and the portion from the surface in contact with the molded body of the lower punch to the lower surface of the die. It is composed of the magnetic metal material defined in the present invention. In the present invention, both of the upper punch and the lower punch are required to have at least their tip portions made of a magnetic metal material, and when only one of them is made of a magnetic metal material, the other punch. A magnetic pole is generated on the surface of the molded body on the side, and the effect of the present invention does not appear, which is not suitable.

The present invention has a sufficient effect even in the case of forming a horizontal magnetic field, but it is particularly effective in forming a vertical magnetic field. Further, 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 magnetism with a saturation magnetization 4πIs of 500 to 12000 gauss and a residual magnetization 4πIr of 6000 gauss or less. As a result, the effect of suppressing the generation of magnetic poles on the surface of the molded body becomes more prominent, and the magnet powder can be supplied into the cavity more uniformly. Examples of anisotropic sintered magnets to which the present invention is applied include ferrite magnets such as Ba ferrite and Sr ferrite magnets, R—Co magnets, and R—Fe magnets.
There are rare earth magnets such as -B type. However, if the present invention is applied particularly when manufacturing a rare earth magnet, the effect of the present invention is remarkably exhibited, so that a preferable result can be obtained. These magnets are manufactured as follows.

R-Co rare earth magnets are RCo ₅ series, R
_Although there are ₂ Co ₁₇ series, etc., most of them are practically used R ₂ Co ₁₇ series. 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
and is manufactured by the following manufacturing method. First, a raw material 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 R ₂ Co ₁₇ rare earth permanent magnet powder. R ₂ Co ₁₇ based rare earth permanent magnet powders are compacted in a magnetic field according to the present invention and then 1100
It is sintered at ˜1250 ° C. for 0.5 to 5 hours, then solutionized at a temperature 0 to 50 ° C. below the sintering temperature for 0.5 to 5 hours, and finally subjected to an aging treatment. The aging treatment is usually a first-stage aging, which is held at 700 to 950 ° C. for a certain period of time, and then continuously cooled or multi-stage aging.

The R-Fe-B type rare earth magnet is usually 5 to 40% R, 50 to 90% Fe, 0.
It 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
Additive elements such as f, Ta, and W are often added. The addition 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 manufacturing the R-Fe-B rare earth magnet is as follows. Raw metal is weighed, melted and cast, and the resulting alloy is finely pulverized to an average particle size of 1 to 20 μm and R-
An Fe-B rare earth permanent magnet powder is obtained. The R—Fe—B rare earth permanent magnet powder is molded in a magnetic field according to the present invention and sintered at 1000 to 1200 ° C. for 0.5 to 5 hours. Finally, aging treatment is performed at 400 to 1000 ° C, and R-
An Fe-B based rare earth magnet is obtained.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The function of the present invention is that, in the process of forming an anisotropic magnet, at least the tip portions of the upper punch and the lower punch are made of a metallic material having magnetism. A permanent magnet powder is supplied into the cavity of, and a magnetic field for orienting the easy magnetization direction is applied to the powder, and the powder is compacted and molded.
This makes it possible to prevent the magnetic poles from appearing on the surface of the molded body, to make the magnetic flux distribution uniform, and to make the magnetic flux directions parallel. Furthermore, the permanent magnet powder can be uniformly filled in the cavity. Therefore, an anisotropic sintered magnet having an improved residual magnetic flux density can be manufactured with high yield.

[0021]

EXAMPLES The embodiments of the present invention will be specifically described below 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%
The alloy of Co ₄ B _6.5 Al ₁ was melted and cast in an argon atmosphere by using an induction heating high frequency melting furnace to melt each raw material metal having a purity of 99.9 wt% or more to produce an alloy ingot. This alloy ingot was placed in an argon atmosphere at 1100 ° C x 24
After performing a homogenizing heat treatment for a time, coarse pulverization is performed using a jaw crusher and a brown mill in an argon atmosphere, and then fine pulverization is performed using a jet mill using nitrogen gas,
R-Fe-B based magnet powder having an average particle size of 5 μm was produced.

Molding was performed using this magnet powder. The upper punch and the lower punch are made of cemented carbide or alloy carbon steel having various saturation magnetizations of 4πIs and remanent magnetization of 4πIr as shown in Table 1 at portions of 50 mm from the tip. Magnet powder was supplied into the cavity, a magnetic field of 15 kOe was applied by an electromagnet, and a pressure of 1 ton / cm ² was applied in the direction perpendicular to the magnetic field application direction while applying the magnetic field to perform molding. The height of the produced molded body is 30 mm. The sectional shape of the cavity in the direction perpendicular to the compression direction is 30 mm × 20 mm. The magnetic field application direction is parallel to the 20 mm side of the molded body.

These compacts were vacuumed at 1060 ° C. for 9 minutes.
After 0 minute sintering, aging heat treatment was further performed at 540 ° C. The magnetic characteristics of the obtained R-Fe-B system sintered magnet were measured using a B-H tracer. Table 1 shows those residual magnetic flux densities. Further, the flatness of the surface perpendicular to the orientation direction of the surface of the sintered body was also measured and shown in Table 1.

[0024]

[Table 1]

Example 2 R-Fe-similar to Example 1
The B-based magnet alloy powder was supplied into the cavity, a magnetic field of 18 kOe was applied by an electromagnet, and a pressure of 1.2 ton / cm ² was applied in a direction parallel to the magnetic field application direction to perform longitudinal magnetic field molding. Saturation magnetization 4πIs is 3500 gauss and residual magnetization 4 is 30 mm from the tips of the upper and lower punches.
It is made of πIr300 Gauss cemented carbide. The height of the produced molded body is 50 mm, and the sectional shape of the cavity in the direction perpendicular to the compression direction is 30 mm × 30.
mm.

The obtained compact was sintered under the same conditions as in Example 1 and subjected to an aging heat treatment to produce a sintered magnet. No distortion was observed in the shape of this sintered body, and its residual magnetic flux density Br was 12.09 kG. As a comparative example,
The entire upper punch and lower punch are made of non-magnetic cemented carbide,
Similarly, when a sintered magnet was manufactured, the shape of the sintered body was distorted, and the residual magnetic flux density Br thereof was 11.84 k.
G.

(Embodiment 3) The alloy composition is Sm2 in wt%.
5.5%, Fe14%, Cu4%, Zr2.5%, balance C
After weighing the raw material metals so as to be o, these 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 crushed in an argon atmosphere using a jaw crusher and a brown mill, and then finely crushed in a jet mill using nitrogen gas to produce R ₂ Co ₁₇ magnet 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 alloy carbon steel having various saturation magnetizations 4πIs and remanent magnetization 4πIr as shown in Table 2. Magnet powder was supplied into the cavity, a magnetic field of 15 kOe was applied by an electromagnet, and a magnetic field of 0.
Molding was performed by applying a pressure of 8 ton / cm ² . The height of the produced molded body is 30 mm. The cross-sectional shape of the cavity in the direction perpendicular to the compression direction is 30 mm x 20 m.
m. The magnetic field application direction is parallel to the 20 mm side of the molded body. This molded body is placed under an argon atmosphere for 12
Sintering at 00 ° C and solutionizing at 1180 ° C. The aging heat treatment is as follows: First-stage aging, holding at 850 ° C for 2 hours, then 1 ° C
It was continuously cooled to 400 ° C. at a cooling rate of / min, and then rapidly cooled. The magnetic characteristics of the obtained R ₂ Co ₁₇ system sintered magnet were measured using a BH tracer. The residual magnetic flux densities are shown in Table 2. Further, the flatness of the surface perpendicular to the orientation direction of the surface of the sintered body was also measured and shown in Table 2.

[0028]

[Table 2]

[0029]

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

Claims (2)

[Claims] 1. A metal having a magnetism with a saturation magnetization of 4πIs of 500 to 12000 gauss and a residual magnetization of 4πIr of 6000 gauss or less in at least the tip portions of the upper punch and the lower punch in the forming step of manufacturing the anisotropic sintered magnet. As a material, a permanent magnet powder is supplied into a cavity of a die composed of a die, the upper punch and the lower punch, a magnetic field for orienting an easy magnetization direction of the permanent magnet powder is applied, and further compressed. A method for producing an anisotropic sintered magnet, which comprises 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 anisotropic sintered magnet is Fe-B-based or R-Co-based rare earth permanent magnet powder.