JPH1070023A - Permanent magnet and its manufacturing method - Google Patents

Abstract

(57) [Problem] To provide a permanent magnet having an enhanced magnetic property by increasing a domain wall pinning effect. SOLUTION: In terms of weight percentage, Sw 25.9%, Cu
4.5%, Fe 15.0%, Zr 3.1% and balance C
Various steps of melting, pulverization, molding, sintering, solution treatment and heat treatment were sequentially performed on the alloy having the composition of o. The heat treatment was performed in an inert atmosphere at a temperature in the range of 790-870 ° C. 100 ° C / min and 500 ° C / min after heat treatment
It was quenched at a cooling rate of. After quenching, 80 in an inert atmosphere
Isothermal aging treatment was performed by heating and holding at 0 ° C. for 300 minutes. Thereafter, continuous cooling was performed at a rate of 1 ° C./min to 400 ° C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth cobalt magnet. More specifically, the present invention relates to a R ₂ Co ₁₇ system precipitation hardening permanent magnet of a specific composition, mainly composed of R (R is one or more rare earth metals including yttrium) -cobalt intermetallic compound and added with Cu, Fe and Zr. It is.

[0002]

2. Description of the Related Art It has long been well known that there are many intermetallic compounds between a rare earth metal and Co.
Ferromagnetic compounds centered on RCo ₅ have extremely large crystal magnetic anisotropy and high saturation magnetic flux density.
It was pointed out that this would be an excellent permanent magnet. This led to the commercialization of rare earth cobalt magnets having much higher characteristics than conventional magnets through many studies. Among RCo ₅ alloys, especially SmCo
In ₅ leading to 30kOe have a high coercive force _I H _C, have reached the maximum energy product in 25 MGOe.

On the other hand, an R ₂ Co _17- based alloy, which is a precipitation hardening type permanent magnet, has a low ratio of R to Co, is inexpensive, has a high saturation magnetic flux density, and has a high energy product. Since then, many studies have shown that the maximum energy product is 30 MGOe in the specific composition to which Cu, Fe and Zr are added.
Was obtained.

[0004] By the way, the R ₂ Co _17- based alloy separates the RCo ₅ phase and the R ₂ Co ₁₇ phase into two phases due to aging and magnetically hardens to exhibit preferable magnetic characteristics. It is known that R ₂ Co _17- based alloy has a cell structure as a microstructure. In the cell structure, the boundaries between the cells are clearly distinguished, and the analysis results of the electron beam diffraction pattern show that the inside of the cell has a rhombohedral 2-line structure.
It is said that there are 17 phases and the cell boundary has 1-5 phases of a hexagonal structure.

On the other hand, it has been found that the coercive force of the R ₂ Co ₁₇ alloy is caused by the size of the cell structure. R ₂
In a system in which Cu, Fe and Zr are added to Co ₁₇ , the aging time is increased and the cell size is coarsened. When a certain cell diameter is reached, the coercive force is maximized. It is said that the coercive force decreases with an increase in.

[0006]

DISCLOSURE OF THE INVENTION The present invention relates to a cell structure found in the microstructure of a precipitation hardening type magnet, particularly R ₂ C
In the main ingredient phase of o _17, by distorting the internal cells, add the pinning effect of the magnetic wall by the cell internal strain not pinning effect only of the domain wall at the cell boundary, a high coercive force, makes it possible high energy product Things. Particularly, between the solution treatment and the aging treatment, 790 ° C to 870 ° C.
After the heat treatment step of quenching after holding in
Large lattice strain can be added to the main component phase of R ₂ Co ₁₇ . For this purpose, rapid cooling at a cooling rate of 300 ° C./min or more is desirable. However, 300 ° C / min
At a cooling rate lower than the above, lattice strain cannot be added. Thus, as the quenching rate in the heat treatment step between the solution treatment and the aging treatment increases, the lattice strain increases,
The pinning effect of the domain wall becomes remarkable, and a high coercive force and a high energy product are made possible.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a composition, comprising, by weight percentage, 23% or more and 27% or less of R (R is one or more rare earth metals including yttrium) and 3% or more and less than 6% of Cu.
And Fe of 10% or more and 25% or less, and 1.5% or more and 4%
In a permanent magnet containing the following Zr and the balance being Co and containing an intermetallic compound mainly composed of rare earth cobalt,
It has a cell structure as a fine structure, and the inside of the cell is R ₂ Co ₁₇
And the cell boundary has a microstructure surrounded by two phases: a phase mainly composed of RCo ₅ , and a Zr-containing plate-like phase parallel to the C-plane of the crystal of the intermetallic compound. It is characterized by the following.

When the fine structure of the permanent magnet of the present invention having such a composition is observed by a transmission electron microscope, it has a cell structure, and the inside of the cell has a lattice distortion of R ₂ Co _17.
Having a microstructure surrounded by two phases, a phase mainly composed of RCo ₅ , and a Zr-containing plate-like phase, and a distance between cell centers of adjacent cells. Is less than 500 angstroms. Preferably 200
It is good to be within the range of 400 Å.

Whether or not to have the above-mentioned cell structure is determined by
It can be easily observed and verified by a scanning electron microscope or a transmission electron microscope.

Such a permanent magnet of the present invention is manufactured as follows. The respective raw materials are blended so as to have the above-mentioned predetermined composition, and are melted by a high-frequency melting furnace in a vacuum of 1 × 10 ⁻² Torr or less to obtain a mother alloy ingot.

Next, the obtained master alloy ingot is roughly pulverized, and further finely pulverized in an inert atmosphere using a jet mill or the like to obtain a powder having an average particle size of 1 to 5 μm.

This powder is placed in a magnetic field of 7 to 22 kOe in a direction perpendicular to or parallel to the magnetic field by 0.5 to 2.0 ton / c.
Press molding with a pressing force of m ² .

[0013] Then, the molded body is placed in a 1 × 10 ^-2 Torr.
In the following vacuum, in an inert atmosphere or in an atmosphere of a combination of these, sinter at a temperature of 1150 to 1250 ° C.
The solution treatment is performed at a temperature lower by ５０50 ° C. After solution treatment,
Rapid cooling at a cooling rate of 100 ° C./min or more. Here, these combinations mean that, for example, in an early stage of the sintering process, after the treatment is performed in a vacuum, the atmosphere is switched to an inert atmosphere in the middle.

After quenching, quenching is performed at a cooling rate of 300 ° C./min or more from a temperature of 790 to 870 ° C. in a vacuum of 1 × 10 ⁻² Torr or less, in an inert atmosphere, or in an atmosphere of a combination of these. The isothermal aging treatment is performed by heating and holding at a temperature of 700 to 870 ° C. for 1 hour or more in a vacuum of × 10 ⁻² Torr or less, in an inert atmosphere, or an atmosphere of a combination of these. Thereafter, when performing continuous aging, at least until the temperature drops to 600 ° C, preferably 400 ° C.
It is preferable to cool at a cooling rate of 0.2 to 5 ° C./min until the temperature falls.

The permanent magnet of the present invention can be widely used for watches, electric motors, gauges, communication devices, computer terminals, speakers, video disks, and other various parts.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION
This will be described in detail in the section of Examples.

[0017]

First, a first embodiment of the present invention will be described.

Sm 25.7 wt%, Cu 4.3 wt%,
Fe 14.9 wt%, Zr 3.0 wt% and balance Co
An alloy having a composition consisting of was melted in a high-frequency melting furnace in a vacuum of 1 × 10 ⁻² Torr or less to obtain a mother alloy ingot. These master alloy ingots were coarsely pulverized and finely pulverized in an inert atmosphere using a jet mill to obtain an average particle size of 4
A μm powder was obtained. This powder was press-molded under a magnetic field of 15 kOe with a pressure of 1.0 ton / cm ² to obtain a molded body. The molded body obtained in this way is 1 × 10
Sintering was performed at a temperature of 1220 ° C. in a vacuum of ⁻² Torr or less and in an inert atmosphere, then a solution treatment was performed at 1200 ° C., and rapid cooling was performed at a cooling rate of 100 ° C./min. After quenching, quenching was performed at a cooling rate in the range of 850 ° C. to 100 ° C./min to 500 ° C./min in an inert atmosphere. After quenching, 800 ° C in an inert atmosphere
At 300 ° C. for isothermal aging treatment, followed by continuous cooling to 400 ° C. at a cooling rate of 1 ° C./min.

The magnetic properties of each permanent magnet material were measured, and the results shown in Table 1 below were obtained.

[0020]

[Table 1] As shown in Table 1, when the cooling rate from the heat treatment after the solution treatment is 300 ° C./min or more, the permanent magnet of the present invention has practically usable magnetic properties (residual magnetic flux density Br, coercive force).
_I H _C, the maximum energy product (BH) _m) was obtained.

Observation of the magnetically hardened permanent magnet by a transmission electron microscope revealed that the permanent magnet had a cell structure as a fine structure and the inside of the cell had lattice distortion.
Has a main ingredient phase of ₂ Co _17, the cell boundary is a phase composed mainly of RCo _5, it was confirmed that the microstructure surrounded by two phases of Zr-containing plate-like phases.

FIGS. 1 and 2 show microstructure photographs (a-plane of the crystal) of the permanent magnets of the test materials 1 and 5 according to the present invention. This is a nanostructure showing a lattice image. In FIG. 1, the lattice images are clearly aligned, and no lattice defects are seen. However, in FIG. 2, lattice distortion is seen in the main component phase of R ₂ Co ₁₇ inside the cell,
It turns out that the pinning effect of the domain wall becomes remarkable, and the coercive force _I H _C also increases.

The permanent magnet of the present invention from above, practically the Kyoseru Br, _I H _C, it can be said that those with (BH) _m.

Next, a second embodiment of the present invention will be described.

Sm 25.9 wt%, Cu 4.5 wt%,
Fe 15.0 wt%, Zr 3.1 wt% and the balance Co
An alloy having a composition consisting of was sequentially subjected to melting, pulverization, molding, sintering, solution treatment, and heat treatment in the same manner as in the first embodiment.

The heat treatment was performed in an inert atmosphere at five heat treatment temperatures shown in Table 2 below, ranging from 790 ° C. to 870 ° C. 100 ℃ / min and 50 after heat treatment
Rapid cooling was performed at a cooling rate of 0 ° C./min. After quenching, an isothermal aging treatment was performed by heating and holding at 800 ° C. for 300 minutes in an inert atmosphere. Thereafter, continuous cooling was performed to 400 ° C. at a cooling rate of 1 ° C./min. The magnetic properties at that time are shown in Table 2 below.

[0027]

[Table 2] As shown in Table 2, the permanent magnet of the present invention has a heat treatment temperature after solution treatment of 790 ° C. or higher and a cooling rate after heat treatment of 30%.
The magnetic properties (Br,
_I H _C, was obtained (BH) _m).

Observation of the magnetically hardened permanent magnet with a transmission electron microscope revealed that the permanent magnet had a cell structure as a fine structure and the inside of the cell had lattice distortion.
Has a main ingredient phase of ₂ Co _17, the cell boundary is a phase composed mainly of RCo _5, it was confirmed that the microstructure surrounded by two phases of Zr-containing plate-like phases.

FIGS. 3 and 4 show microstructure photographs (a-plane of the crystal) of the permanent magnets of the test materials 9 and 14 according to the present invention.
This is a nanostructure showing a lattice image. In FIG. 3, the lattice images are clearly aligned, and no lattice defects are seen. However, in FIG. 4, lattice distortion is seen in the main component phase of R ₂ Co ₁₇ inside the cell, the pinning effect of the domain wall becomes remarkable, and the coercive force _I H _C
It also turns out that there is a relationship that also increases.

The permanent magnet of the present invention from above, practically the Kyoseru Br, _I H _C, it can be said that those with (BH) _m.

[0031]

As described above, according to the present invention, a cell structure is obtained as a fine structure by quenching and isothermal aging after melting, pulverizing, sintering, and solution treatment. Has a main component phase of R ₂ Co ₁₇ and a cell boundary portion is RCo
_In a permanent magnet characterized by having a microstructure surrounded by two phases of a phase containing ₅ as a main component and a Zr-containing plate-like phase, the main component phase of R ₂ Co ₁₇ inside the cell has lattice distortion. , The pinning effect of the domain wall is increased, and a permanent magnet having excellent magnetic properties can be provided.

[Brief description of the drawings]

FIG. 1 is a photograph of a crystal structure by a transmission electron microscope showing a lattice image of a permanent magnet of a test material 1 according to a first embodiment of the present invention.

FIG. 2 is a photograph of a crystal structure by a transmission electron microscope showing a lattice image of a permanent magnet of a test material 5 according to the first embodiment of the present invention.

FIG. 3 shows a photograph of a crystal structure by a transmission electron microscope showing a lattice image of a permanent magnet of a test material 9 in a second embodiment of the present invention.

FIG. 4 shows a photograph of a crystal structure by a transmission electron microscope showing a lattice image of a permanent magnet of a test piece 14 in a second embodiment of the present invention.

Claims (2)

[Claims] 1. An R of 23% or more and 27% or less in weight percentage (R is at least one rare earth metal containing yttrium).
, 3% or less and less than 6% Cu, 10% or more and 25% or less Fe, 1.5% or more and 4% or less Zr, and the balance Co
Containing an intermetallic compound mainly composed of rare earth cobalt, having a Zr-containing plate-like phase parallel to the C plane of the crystal of the intermetallic compound, having a cell structure as a fine structure, and having a lattice distortion inside the cell. has a main ingredient phase of R ₂ Co ₁₇ having a cell boundary is characterized and a phase composed mainly of RCo _5, that have a microstructure surrounded by two phases of Zr-containing plate-like phase permanent magnet. 2. A raw material is blended so as to have an alloy composition according to claim 1, and in a vacuum of 1 × 10 ⁻² Torr or less,
A melting step of obtaining a mother alloy ingot by a high-frequency melting furnace; a step of coarsely pulverizing the obtained ingot; a fine pulverization step of forming a powder having an average particle diameter of 1 to 5 μm in an inert atmosphere; Perpendicular to the magnetic field in a magnetic field of 22 kOe,
Or a pressing step using a pressing force of 0.5 to 2.0 ton / cm ^{2 in} a parallel direction; and pressing the molded body in a vacuum of 1 × 10 ⁻² Torr or less, in an inert atmosphere, or in an atmosphere of a combination thereof.
A sintering step of sintering at a temperature of 1150 to 1250 ° C .;
℃ and solution heat treating at a low temperature, after solution, a step of quenching at 100 ° C. / min or more cooling rate, after quenching, 1 × 10 ^-2 Torr in a vacuum of, in an inert atmosphere or these 790-87 in a combination atmosphere
It is rapidly cooled from a temperature of 0 ° C. at a cooling rate of 300 ° C./min or more, and is further heated and held at a temperature of 700 to 870 ° C. for 1 hour or more to perform isothermal aging treatment.
And cooling at a cooling rate of 0.2 to 5 ° C./min.