JPS5852013B2 - Manufacturing method of rare earth cobalt magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intermetallic compound RCo magnet whose main components are rare earth metals or yttrium and cobalt, and particularly to a manufacturing method for realizing high performance thereof.

Rare earth cobalt magnets are generally manufactured by a so-called powder metallurgy method in which the magnets are molded and then sintered.

As a method of obtaining a magnet with a high energy product using a powder metallurgy method, a method is used in which magnet raw powder is molded in a magnetic field.

Magnetic field molding methods include a wet method in which fine raw material powder is suspended in a dispersion medium such as alcohol and molded while applying a magnetic field in a mold, and a dry method in which the dried fine raw material powder is molded while a magnetic field is applied. There is a law.

In general, the wet method produces magnets with higher performance than the dry method.

On the other hand, in the wet method, it is necessary to discharge the dispersion medium out of the mold during pressure molding, which increases the time required for molding.

If measures for forced liquid drainage are taken, the molding apparatus becomes large-scale.

On the other hand, the dry method has advantages such as short molding time, small equipment, and easy handling of molding powder.

The purpose of the present invention is to provide a manufacturing method that can obtain high-performance magnets even if a dry method, which has many advantages, is adopted as a magnetic field forming method. It can also be applied to cases in which magnets are used, and high performance magnets can be achieved.

Various methods have been attempted to date to realize a high energy product of rare earth cobalt magnets.

Among them, the factors that are recognized to be effective are the purity of raw materials, substitution with specific elements, oxygen content, particle size of molding powder, strength of magnetic field applied during molding, method of applying magnetic field, sintering atmosphere, Examples include freezing temperature and cooling rate.

The present invention is not included in these conventionally considered factors, and is a new method for achieving high performance.

The present invention provides an intermetallic compound R whose main components are yttrium, a rare earth metal (represented by R), and cobal (Co).
In the method for producing a Co5-based magnet, as a molding powder,
Use molding powder adjusted so that the diffraction intensity of the RCo 5 phase in X-ray diffraction in the range corresponding to the plane index of (101) to (102) of the RCo 5 phase is 45% or more of the total diffraction intensity. It is characterized by this.

Examples in which the present invention is applied to SmCo5 magnets will be described below.

Sm is 22~43w by dissolution method or reduction diffusion method
60 kinds of Sm-c in the range of t%.

A series alloy was prepared.

The oxygen content of each alloy was all below 2000 pIll.

In order to know the proportion of SrnCO5 phase in each alloy, each alloy was coarsely pulverized, and Fe- was irradiated with α rays at 2θ (θ is the diffraction angle) in a range of 35° (RCo, phase plane index (101 )from(
X-ray diffraction was performed in the range including 102).

Each diffraction line intensity (■) is determined, and the diffraction line intensity (this is expressed as I(1-5)) of the SmCo phase relative to their sum (this is expressed as ΣIi).

), the ratio I(1→'') was calculated. ΣI1 Next, two or more of the above 60 kinds of alloy powders are selected and mixed, wet-pulverized in a vibrating mill to a particle size of about 3μ, and dried to form a plurality of different alloy powders with '(1-5)/ΣIi. A seed molding powder was obtained.

In addition, at the time of mixing, the content of Sm was selected to be 34 to 37 wt% and the component amount of the alloy powder was selected so that the magnetic properties at the optimum composition could be found.

Each of the molding powders thus obtained was molded into a disk shape with a diameter of 16n1 and a height of 8m in a magnetic field of approximately 10KOe under a molding pressure of 1tm/c.
Pressure molding was performed at WL in a direction parallel to the magnetic field.

The obtained compacted powder was degassed in vacuo, and then sintered at a temperature of 1120° C.±5° C. in an argon atmosphere, slowly cooled, and then rapidly cooled to obtain a sintered body.

After polishing the surface layer of these sintered bodies, the magnetic properties were measured.

Residual magnetization Br and energy product (BH)m of each sintered body
ax and the proportion of SmCo and phase in the molding powder, i.e. '(
1-5)/ΣIi is shown in the figure.

In addition, in order to take advantage of the high coercive force that is a feature of SmCo5 magnets, the values of the magnetic field HK at which the magnetization is reduced by 10% compared to the residual magnetization Br are shown for 13 KOe or more.

As is clear from the figure, SmCo in the molding powder.

As the proportion of phases increases, higher performance magnets can be obtained.

Until now, the residual magnetization of SmCo and magnets has usually been around 7.0 to 8.4 KG, and if you want to obtain a stronger magnet than this, the magnetic field applied during molding must be reduced by several hundred kilograms.
(e) There were drawbacks such as wet pressing, which required equipment and extended molding time.

However, as is clear from the figure, Sm in the molding powder
The ratio I of the X-ray diffraction intensity of Co (1-5 and ΣIi is 45
% or more, the residual magnetization Br is 8.4 KG or more,
Maximum energy product (BH) max is approximately 17M.

G, Oe or higher can be obtained, and as described above, the subsequent steps including the magnetic field forming step are similar to the conventional method.

That is, the ratio of the X-ray diffraction intensity of the SmCo alloy phase is 45
By selectively mixing and adjusting the molding powder so that the powder is mixed at a concentration of at least %, it is possible to easily obtain a molding powder with high magnetic properties. By doing so, a rare earth cobalt magnet with significantly improved magnetic properties can be easily manufactured.

In addition, above, we have only described SmCo5 magnets using the dry magnetic field forming method, but similar effects can be seen when using the wet forming method. Similar effects were observed for RCo and magnets.

An example is shown below. Manufactured by reduction method, Sm0.4
MM006. , Co5 powder (here, the component of MM is La
27 wt%, Ce59 wt%, Nd 11 wt%,
Pr3wt%) was heat-treated in vacuum to obtain powders with different RCO5 phases (here, R is synonymous with Sm0.4MM0.6).

This powder was wet-pulverized using a vibration mill to obtain a fine powder of about 3.5 μm.

This powder was molded in the same manner as in the previous example.

Sintered in a similar manner at a holding temperature of 1050,'C,
The magnetic properties were investigated.

The results are shown below.

As described above, increasing the ratio of RCo and phase in the green compact improves the magnetic properties.

RCo-based alloys have a crystal structure with an easy magnetization direction in the C-axis direction.

Therefore, whether R is Sm or another rare earth element, it is extremely well known from physics that an alloy with an RCo5 type crystal structure has an easy magnetization direction in the C-axis direction. That's true.

X-ray diffraction is a method for investigating the structure of this crystal, and it is well known that similar diffraction patterns are obtained for substances having the same type of crystal structure.

Therefore, in the previous embodiment, only the SmCo5 magnet was described, but it is clear that the present invention can be similarly applied to other rare earth cobalt magnets.

In addition, like the conventional RCo5 magnet, iron, nickel, copper,
Even if additives such as manganese, titanium, and zirconium are included, the effects of the present invention will not change.

[Brief explanation of drawings]

The figure shows the residual magnetization Br and maximum energy product (BH) max of a samarium cobalt magnet and S m in the molding powder.
Co, the ratio of the X-ray diffraction intensity of the phase (I(1-5)/Σ
It is a graph showing the relationship with Ii).

Claims (1)

[Claims] 1 Yttrium and rare earth metals (generally referred to as R
In the method for manufacturing an intermetallic compound RCo, which is mainly composed of cobalt (Co) and cobalt (Co), RCo is used as a molding powder, and the phase plane index ranges from (101) to (102).
) A method for producing a rare earth cobalt magnet, characterized by using molding powder adjusted so that the diffraction intensity of the RCO5 phase in X-ray diffraction in a range corresponding to 45% or more of the total diffraction intensity.